[RFC v2 00/10] kdb: Kiosk (reduced capabilities) mode - linaro-kernel

Daniel Thompson

2 Apr 2 Apr

3:43 p.m.

New subject: [RFC v2 01/10] sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb

If kdb is triggered using SysRq-g then any use of the sr command results in the SysRq key table lock being recursively acquired, killing the debug session. That patch resolves the problem by introducing a _nolock alternative for __handle_sysrq.

Strictly speaking this approach risks racing on the key table when kdb is triggered by something other than SysRq-g however in that case any other CPU involved should release the spin lock before kgdb parks the slave CPUs.

Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- drivers/tty/sysrq.c | 11 ++++++++--- include/linux/sysrq.h | 1 + kernel/debug/kdb/kdb_main.c | 2 +- 3 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c index ce396ec..7b47b2d 100644 --- a/drivers/tty/sysrq.c +++ b/drivers/tty/sysrq.c @@ -505,14 +505,12 @@ static void __sysrq_put_key_op(int key, struct sysrq_key_op *op_p) sysrq_key_table[i] = op_p; }

-void __handle_sysrq(int key, bool check_mask) +void __handle_sysrq_nolock(int key, bool check_mask) { struct sysrq_key_op *op_p; int orig_log_level; int i; - unsigned long flags;

- spin_lock_irqsave(&sysrq_key_table_lock, flags); /* * Raise the apparent loglevel to maximum so that the sysrq header * is shown to provide the user with positive feedback. We do not @@ -554,6 +552,13 @@ void __handle_sysrq(int key, bool check_mask) printk("\n"); console_loglevel = orig_log_level; } +} + +void __handle_sysrq(int key, bool check_mask) +{ + unsigned long flags; + spin_lock_irqsave(&sysrq_key_table_lock, flags); + __handle_sysrq_nolock(key, check_mask); spin_unlock_irqrestore(&sysrq_key_table_lock, flags); }

diff --git a/include/linux/sysrq.h b/include/linux/sysrq.h index 387fa7d..1d51d64 100644 --- a/include/linux/sysrq.h +++ b/include/linux/sysrq.h @@ -44,6 +44,7 @@ struct sysrq_key_op {

void handle_sysrq(int key); void __handle_sysrq(int key, bool check_mask); +void __handle_sysrq_nolock(int key, bool check_mask); int register_sysrq_key(int key, struct sysrq_key_op *op); int unregister_sysrq_key(int key, struct sysrq_key_op *op); struct sysrq_key_op *__sysrq_get_key_op(int key); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 0b097c8..f39f926 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1924,7 +1924,7 @@ static int kdb_sr(int argc, const char **argv) if (argc != 1) return KDB_ARGCOUNT; kdb_trap_printk++; - __handle_sysrq(*argv[1], false); + __handle_sysrq_nolock(*argv[1], false); kdb_trap_printk--;

return 0;

-- 1.9.0

Reply

Daniel Thompson

3:43 p.m.

New subject: [RFC v2 03/10] kdb: Rename kdb_repeat_t to kdb_cmdflags_t, cmd_repeat to cmd_flags

From: Anton Vorontsov anton.vorontsov@linaro.org

We're about to add more options for command behaviour, so let's expand the meaning of kdb_repeat_t.

So far we just do various renames, there should be no functional changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- include/linux/kdb.h | 4 ++-- kernel/debug/kdb/kdb_main.c | 6 +++--- kernel/debug/kdb/kdb_private.h | 2 +- 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 290db12..0911633 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -17,7 +17,7 @@ typedef enum { KDB_REPEAT_NONE = 0, /* Do not repeat this command */ KDB_REPEAT_NO_ARGS, /* Repeat the command without arguments */ KDB_REPEAT_WITH_ARGS, /* Repeat the command including its arguments */ -} kdb_repeat_t; +} kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **);

@@ -147,7 +147,7 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos) /* Dynamic kdb shell command registration */ extern int kdb_register(char *, kdb_func_t, char *, char *, short); extern int kdb_register_repeat(char *, kdb_func_t, char *, char *, - short, kdb_repeat_t); + short, kdb_cmdflags_t); extern int kdb_unregister(char *); #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 938c47b..c328cc6 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1008,7 +1008,7 @@ int kdb_parse(const char *cmdstr) if (result && ignore_errors && result > KDB_CMD_GO) result = 0; KDB_STATE_CLEAR(CMD); - switch (tp->cmd_repeat) { + switch (tp->cmd_flags) { case KDB_REPEAT_NONE: argc = 0; if (argv[0]) @@ -2646,7 +2646,7 @@ int kdb_register_repeat(char *cmd, char *usage, char *help, short minlen, - kdb_repeat_t repeat) + kdb_cmdflags_t flags) { int i; kdbtab_t *kp; @@ -2695,7 +2695,7 @@ int kdb_register_repeat(char *cmd, kp->cmd_usage = usage; kp->cmd_help = help; kp->cmd_minlen = minlen; - kp->cmd_repeat = repeat; + kp->cmd_flags = flags;

return 0; } diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index c4c46c7..eaacd16 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -174,7 +174,7 @@ typedef struct _kdbtab { char *cmd_help; /* Help message for this command */ short cmd_minlen; /* Minimum legal # command * chars required */ - kdb_repeat_t cmd_repeat; /* Does command auto repeat on enter? */ + kdb_cmdflags_t cmd_flags; /* Command behaviour flags */ } kdbtab_t;

extern int kdb_bt(int, const char **); /* KDB display back trace */

-- 1.9.0

Reply

Daniel Thompson

3:43 p.m.

New subject: [RFC v2 05/10] kdb: Use KDB_REPEAT_* values as flags

From: Anton Vorontsov anton.vorontsov@linaro.org

The actual values of KDB_REPEAT_* enum values and overall logic stayed the same, but we now treat the values as flags.

This makes it possible to add other flags and combine them, plus makes the code a lot simpler and shorter. But functionality-wise, there should be no changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- include/linux/kdb.h | 4 ++-- kernel/debug/kdb/kdb_main.c | 21 +++++++-------------- 2 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 02bae26..f5cc722 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -15,8 +15,8 @@

typedef enum { KDB_REPEAT_NONE = 0, /* Do not repeat this command */ - KDB_REPEAT_NO_ARGS, /* Repeat the command without arguments */ - KDB_REPEAT_WITH_ARGS, /* Repeat the command including its arguments */ + KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ + KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ } kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 17f9042..5d67ff6 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1008,20 +1008,13 @@ int kdb_parse(const char *cmdstr) if (result && ignore_errors && result > KDB_CMD_GO) result = 0; KDB_STATE_CLEAR(CMD); - switch (tp->cmd_flags) { - case KDB_REPEAT_NONE: - argc = 0; - if (argv[0]) - *(argv[0]) = '\0'; - break; - case KDB_REPEAT_NO_ARGS: - argc = 1; - if (argv[1]) - *(argv[1]) = '\0'; - break; - case KDB_REPEAT_WITH_ARGS: - break; - } + + if (tp->cmd_flags & KDB_REPEAT_WITH_ARGS) + return result; + + argc = tp->cmd_flags & KDB_REPEAT_NO_ARGS ? 1 : 0; + if (argv[argc]) + *(argv[argc]) = '\0'; return result; }

-- 1.9.0

Reply

Daniel Thompson

3:43 p.m.

New subject: [RFC v2 07/10] kdb: Mark safe commands as KDB_SAFE and KDB_SAFE_NO_ARGS

From: Anton Vorontsov anton.vorontsov@linaro.org

This patch introduces two new flags: KDB_SAFE, denotes a safe command, and KDB_SAFE_NO_ARGS, denotes a safe command when used without arguments.

The word "safe" here used in the sense that the commands cannot be used to leak sensitive data from the memory, and cannot be used to change program flow in a predefined manner.

These flags will be used by the "kiosk" mode, i.e. when it is possible for the ordinary user to enter the KDB (or user can get the access to KDB after the crash), but we do not allow user to read dump the memory [and thus read some sensitive data].

The following commands were marked as "safe":

Display stack for process Display stack all processes Backtrace current process on each cpu Execute cmd for each element in linked list Show environment variables Set environment variables Display Help Message Switch to new cpu Display active task list Switch to another task Reboot the machine immediately List loaded kernel modules Magic SysRq key Display syslog buffer Define a set of commands, down to endefcmd Summarize the system Disable NMI entry to KDB Macro commands (subject to finer grain checking)

The following commands were marked as safe when issued with no arguments:

Stack traceback Continue Execution

And the following commands are unsafe:

Display exception frame Clear Breakpoint Enable Breakpoint Disable Breakpoint Single step Single step to branch/call Continue Execution (with address argument) Display Memory Contents Display Raw Memory Display Physical Memory Display Memory Symbolically Modify Memory Contents Display Registers Modify Registers Backtrace process given its struct task address Send a signal to a process Enter kgdb mode Display per_cpu variables

Note that we mark "display registers" command unsafe, this is because single stepping + constantly dumping registers in string or memory functions can be used as a way to read sensitive data (it's actually trivial to exploit). Later we can do a bit better, i.e. not displaying general-purpose registers, but printing control registers.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- include/linux/kdb.h | 2 ++ kernel/debug/kdb/kdb_main.c | 48 ++++++++++++++++++++++++--------------------- kernel/trace/trace_kdb.c | 2 +- 3 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 4b656d6..784b22f 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -16,6 +16,8 @@ typedef enum { KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ + KDB_SAFE = 0x4, /* Security-wise safe command */ + KDB_SAFE_NO_ARGS = 0x8, /* Only safe if run w/o arguments */ } kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index a40b05b..0205e4a 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -641,8 +641,12 @@ static int kdb_defcmd2(const char *cmdstr, const char *argv0) if (!s->count) s->usable = 0; if (s->usable) - kdb_register(s->name, kdb_exec_defcmd, - s->usage, s->help, 0); + /* macros are safe because when executed each + * internal command re-enters kdb_parse() and is + * safety checked individually. + */ + kdb_register_flags(s->name, kdb_exec_defcmd, + s->usage, s->help, 0, KDB_SAFE); return 0; } if (!s->usable) @@ -2767,7 +2771,7 @@ static void __init kdb_inittab(void) kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[<vaddr>]", - "Continue Execution", 1, 0); + "Continue Execution", 1, KDB_SAFE_NO_ARGS); kdb_register_flags("rd", kdb_rd, "", "Display Registers", 0, 0); kdb_register_flags("rm", kdb_rm, "<reg> <contents>", @@ -2775,60 +2779,60 @@ static void __init kdb_inittab(void) kdb_register_flags("ef", kdb_ef, "<vaddr>", "Display exception frame", 0, 0); kdb_register_flags("bt", kdb_bt, "[<vaddr>]", - "Stack traceback", 1, 0); + "Stack traceback", 1, KDB_SAFE_NO_ARGS); kdb_register_flags("btp", kdb_bt, "<pid>", - "Display stack for process <pid>", 0, 0); + "Display stack for process <pid>", 0, KDB_SAFE); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, 0); + "Backtrace all processes matching state flag", 0, KDB_SAFE); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, 0); + "Backtrace current process on each cpu", 0, KDB_SAFE); kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, 0); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, 0); + "Show environment variables", 0, KDB_SAFE); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, 0); + "Set environment variables", 0, KDB_SAFE); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, 0); + "Display Help Message", 1, KDB_SAFE); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, 0); + "Display Help Message", 0, KDB_SAFE); kdb_register_flags("cpu", kdb_cpu, "<cpunum>", - "Switch to new cpu", 0, 0); + "Switch to new cpu", 0, KDB_SAFE); kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[<flags>|A]", - "Display active task list", 0, 0); + "Display active task list", 0, KDB_SAFE); kdb_register_flags("pid", kdb_pid, "<pidnum>", - "Switch to another task", 0, 0); + "Switch to another task", 0, KDB_SAFE); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, 0); + "Reboot the machine immediately", 0, KDB_SAFE); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, 0); + "List loaded kernel modules", 0, KDB_SAFE); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "<key>", - "Magic SysRq key", 0, 0); + "Magic SysRq key", 0, KDB_SAFE); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, 0); + "Display syslog buffer", 0, KDB_SAFE); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, 0); + "Disable NMI entry to KDB", 0, KDB_SAFE); } kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", - "Define a set of commands, down to endefcmd", 0, 0); + "Define a set of commands, down to endefcmd", 0, KDB_SAFE); kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", "Send a signal to a process", 0, 0); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, 0); + "Summarize the system", 4, KDB_SAFE); kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", "Display per_cpu variables", 3, 0); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, 0); + "Display help on | grep", 0, KDB_SAFE); }

/* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 3da7e30..52f9ad6 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, 0); + "Dump ftrace log", 0, KDB_SAFE); return 0; }

-- 1.9.0

Reply

Daniel Thompson

3:43 p.m.

New subject: [RFC v2 09/10] kdb: Improve usability of help text when running in kiosk mode

Currently 'help' in kiosk mode results in help text being issued for many commands the user cannot actually run. Filter the help list when kiosk mode is engaged to ensure help is fully relevant.

Filtering the list is also greatly simplifies scanning for commands that may have been accidentally classified as safe.

Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- kernel/debug/kdb/kdb_main.c | 3 +++ 1 file changed, 3 insertions(+)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 808bf55..77b6e61 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2401,6 +2401,9 @@ static int kdb_help(int argc, const char **argv) return 0; if (!kt->cmd_name) continue; + if (kdb_kiosk && + !(kt->cmd_flags & (KDB_SAFE | KDB_SAFE_NO_ARGS))) + continue; if (strlen(kt->cmd_usage) > 20) space = "\n "; kdb_printf("%-15.15s %-20s%s%s\n", kt->cmd_name,

-- 1.9.0

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Daniel Thompson

25 Apr 25 Apr

4:29 p.m.

New subject: [RFC v3 0/9] kdb: Allow selective reduction in capabilities (was "kiosk mode")

### This RFC has significant updates since v2. Comments appreciated (I ### hope the next iteration can be PATCH rather than RFC).

This patchset implements restricted modes for the KDB debugger. It is a continuation of previous kiosk mode work of Anton Vorontsov (dating back to late 2012).

Modelled of the SysRq masking functionality it provides a means for the root user to choose the set of kdb commands that are available on the kdb console.

There are a few patches, some are just cleanups, some are churn-ish cleanups, but inevitable. And the rest implements the mode -- after all the preparations, everything is pretty straightforward. The first patch is actually a pure bug fix (arguably unrelated to kiosk mode) but collides with the code to honour the sysrq mask when capabilities are stricted so I have included it here.

Changes since v2: * Fixed stupid build error when CONFIG_KDB[_KIOSK]_DEFAULT_ENABLE was not defined. * Increase flexibility by allowing the userspace greater control over the commands to be restricted. * Removed the "kiosk" terminology. Its confusing.

Changes since v1 (circa 2012):

* ef (Display exception frame) is essentially an overly complex peek and has therefore been marked unsafe * bt (Stack traceback) has been marked safe only with no arguments * sr (Magic SysRq key) honours the sysrq mask when called in kiosk mode * Fixed over-zealous blocking of macro commands * Symbol lookup is forbidden by kdbgetaddrarg (more robust, better error reporting to user) * Fix deadlock in sr (Magic SysRq key) * Better help text in kiosk mode * Default (kiosk on/off) can be changed From the config file.

Anton Vorontsov (6): kdb: Remove currently unused kdbtab_t->cmd_flags kdb: Rename kdb_repeat_t to kdb_cmdflags_t, cmd_repeat to cmd_flags kdb: Rename kdb_register_repeat() to kdb_register_flags() kdb: Use KDB_REPEAT_* values as flags kdb: Remove KDB_REPEAT_NONE flag kdb: Add enable mask for groups of commands

Daniel Thompson (3): sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb kdb: Categorize kdb commands (similar to SysRq categorization) kdb: Allow access to sensitive commands to be restricted by default

-- 1.9.0

Reply

Daniel Thompson

4:29 p.m.

New subject: [RFC v3 2/9] kdb: Remove currently unused kdbtab_t->cmd_flags

From: Anton Vorontsov anton.vorontsov@linaro.org

The struct member is never used in the code, so we can remove it.

We will introduce real flags soon by renaming cmd_repeat to cmd_flags.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org --- kernel/debug/kdb/kdb_main.c | 1 - kernel/debug/kdb/kdb_private.h | 1 - 2 files changed, 2 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index f39f926..938c47b 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2694,7 +2694,6 @@ int kdb_register_repeat(char *cmd, kp->cmd_func = func; kp->cmd_usage = usage; kp->cmd_help = help; - kp->cmd_flags = 0; kp->cmd_minlen = minlen; kp->cmd_repeat = repeat;

diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index 7afd3c8..c4c46c7 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -172,7 +172,6 @@ typedef struct _kdbtab { kdb_func_t cmd_func; /* Function to execute command */ char *cmd_usage; /* Usage String for this command */ char *cmd_help; /* Help message for this command */ - short cmd_flags; /* Parsing flags */ short cmd_minlen; /* Minimum legal # command * chars required */ kdb_repeat_t cmd_repeat; /* Does command auto repeat on enter? */

-- 1.9.0

Reply

Daniel Thompson

4:29 p.m.

New subject: [RFC v3 4/9] kdb: Rename kdb_register_repeat() to kdb_register_flags()

From: Anton Vorontsov anton.vorontsov@linaro.org

We're about to add more options for commands behaviour, so let's give a more generic name to the low-level kdb command registration function.

There are just various renames, no functional changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org --- include/linux/kdb.h | 10 +++--- kernel/debug/kdb/kdb_bp.c | 14 ++++---- kernel/debug/kdb/kdb_main.c | 86 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 56 insertions(+), 56 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 0911633..02bae26 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -146,17 +146,17 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos)

/* Dynamic kdb shell command registration */ extern int kdb_register(char *, kdb_func_t, char *, char *, short); -extern int kdb_register_repeat(char *, kdb_func_t, char *, char *, - short, kdb_cmdflags_t); +extern int kdb_register_flags(char *, kdb_func_t, char *, char *, + short, kdb_cmdflags_t); extern int kdb_unregister(char *); #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } static inline void kdb_init(int level) {} static inline int kdb_register(char *cmd, kdb_func_t func, char *usage, char *help, short minlen) { return 0; } -static inline int kdb_register_repeat(char *cmd, kdb_func_t func, char *usage, - char *help, short minlen, - kdb_repeat_t repeat) { return 0; } +static inline int kdb_register_flags(char *cmd, kdb_func_t func, char *usage, + char *help, short minlen, + kdb_repeat_t repeat) { return 0; } static inline int kdb_unregister(char *cmd) { return 0; } #endif /* CONFIG_KGDB_KDB */ enum { diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 70a5046..7be2c5d 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -531,21 +531,21 @@ void __init kdb_initbptab(void) for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) bp->bp_free = 1;

- kdb_register_repeat("bp", kdb_bp, "[<vaddr>]", + kdb_register_flags("bp", kdb_bp, "[<vaddr>]", "Set/Display breakpoints", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bl", kdb_bp, "[<vaddr>]", + kdb_register_flags("bl", kdb_bp, "[<vaddr>]", "Display breakpoints", 0, KDB_REPEAT_NO_ARGS); if (arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT) - kdb_register_repeat("bph", kdb_bp, "[<vaddr>]", + kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bc", kdb_bc, "<bpnum>", + kdb_register_flags("bc", kdb_bc, "<bpnum>", "Clear Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("be", kdb_bc, "<bpnum>", + kdb_register_flags("be", kdb_bc, "<bpnum>", "Enable Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bd", kdb_bc, "<bpnum>", + kdb_register_flags("bd", kdb_bc, "<bpnum>", "Disable Breakpoint", 0, KDB_REPEAT_NONE);

- kdb_register_repeat("ss", kdb_ss, "", + kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); /* * Architecture dependent initialization. diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index c328cc6..17f9042 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2629,7 +2629,7 @@ static int kdb_grep_help(int argc, const char **argv) }

/* - * kdb_register_repeat - This function is used to register a kernel + * kdb_register_flags - This function is used to register a kernel * debugger command. * Inputs: * cmd Command name @@ -2641,12 +2641,12 @@ static int kdb_grep_help(int argc, const char **argv) * zero for success, one if a duplicate command. */ #define kdb_command_extend 50 /* arbitrary */ -int kdb_register_repeat(char *cmd, - kdb_func_t func, - char *usage, - char *help, - short minlen, - kdb_cmdflags_t flags) +int kdb_register_flags(char *cmd, + kdb_func_t func, + char *usage, + char *help, + short minlen, + kdb_cmdflags_t flags) { int i; kdbtab_t *kp; @@ -2699,13 +2699,13 @@ int kdb_register_repeat(char *cmd,

return 0; } -EXPORT_SYMBOL_GPL(kdb_register_repeat); +EXPORT_SYMBOL_GPL(kdb_register_flags);

/* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_repeat with KDB_REPEAT_NONE. + * kdb_register_flags with KDB_REPEAT_NONE. * Inputs: * cmd Command name * func Function to execute the command @@ -2720,8 +2720,8 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_repeat(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, + KDB_REPEAT_NONE); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2763,79 +2763,79 @@ static void __init kdb_inittab(void) for_each_kdbcmd(kp, i) kp->cmd_name = NULL;

- kdb_register_repeat("md", kdb_md, "<vaddr>", + kdb_register_flags("md", kdb_md, "<vaddr>", "Display Memory Contents, also mdWcN, e.g. md8c1", 1, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdr", kdb_md, "<vaddr> <bytes>", + kdb_register_flags("mdr", kdb_md, "<vaddr> <bytes>", "Display Raw Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdp", kdb_md, "<paddr> <bytes>", + kdb_register_flags("mdp", kdb_md, "<paddr> <bytes>", "Display Physical Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mds", kdb_md, "<vaddr>", + kdb_register_flags("mds", kdb_md, "<vaddr>", "Display Memory Symbolically", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mm", kdb_mm, "<vaddr> <contents>", + kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("go", kdb_go, "[<vaddr>]", + kdb_register_flags("go", kdb_go, "[<vaddr>]", "Continue Execution", 1, KDB_REPEAT_NONE); - kdb_register_repeat("rd", kdb_rd, "", + kdb_register_flags("rd", kdb_rd, "", "Display Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("rm", kdb_rm, "<reg> <contents>", + kdb_register_flags("rm", kdb_rm, "<reg> <contents>", "Modify Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ef", kdb_ef, "<vaddr>", + kdb_register_flags("ef", kdb_ef, "<vaddr>", "Display exception frame", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bt", kdb_bt, "[<vaddr>]", + kdb_register_flags("bt", kdb_bt, "[<vaddr>]", "Stack traceback", 1, KDB_REPEAT_NONE); - kdb_register_repeat("btp", kdb_bt, "<pid>", + kdb_register_flags("btp", kdb_bt, "<pid>", "Display stack for process <pid>", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", + kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btc", kdb_bt, "", + kdb_register_flags("btc", kdb_bt, "", "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btt", kdb_bt, "<vaddr>", + kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, KDB_REPEAT_NONE); - kdb_register_repeat("env", kdb_env, "", + kdb_register_flags("env", kdb_env, "", "Show environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("set", kdb_set, "", + kdb_register_flags("set", kdb_set, "", "Set environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("help", kdb_help, "", + kdb_register_flags("help", kdb_help, "", "Display Help Message", 1, KDB_REPEAT_NONE); - kdb_register_repeat("?", kdb_help, "", + kdb_register_flags("?", kdb_help, "", "Display Help Message", 0, KDB_REPEAT_NONE); - kdb_register_repeat("cpu", kdb_cpu, "<cpunum>", + kdb_register_flags("cpu", kdb_cpu, "<cpunum>", "Switch to new cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kgdb", kdb_kgdb, "", + kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ps", kdb_ps, "[<flags>|A]", + kdb_register_flags("ps", kdb_ps, "[<flags>|A]", "Display active task list", 0, KDB_REPEAT_NONE); - kdb_register_repeat("pid", kdb_pid, "<pidnum>", + kdb_register_flags("pid", kdb_pid, "<pidnum>", "Switch to another task", 0, KDB_REPEAT_NONE); - kdb_register_repeat("reboot", kdb_reboot, "", + kdb_register_flags("reboot", kdb_reboot, "", "Reboot the machine immediately", 0, KDB_REPEAT_NONE); #if defined(CONFIG_MODULES) - kdb_register_repeat("lsmod", kdb_lsmod, "", + kdb_register_flags("lsmod", kdb_lsmod, "", "List loaded kernel modules", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_MAGIC_SYSRQ) - kdb_register_repeat("sr", kdb_sr, "<key>", + kdb_register_flags("sr", kdb_sr, "<key>", "Magic SysRq key", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_PRINTK) - kdb_register_repeat("dmesg", kdb_dmesg, "[lines]", + kdb_register_flags("dmesg", kdb_dmesg, "[lines]", "Display syslog buffer", 0, KDB_REPEAT_NONE); #endif if (arch_kgdb_ops.enable_nmi) { - kdb_register_repeat("disable_nmi", kdb_disable_nmi, "", + kdb_register_flags("disable_nmi", kdb_disable_nmi, "", "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); } - kdb_register_repeat("defcmd", kdb_defcmd, "name "usage" "help"", + kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kill", kdb_kill, "<-signal> <pid>", + kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", "Send a signal to a process", 0, KDB_REPEAT_NONE); - kdb_register_repeat("summary", kdb_summary, "", + kdb_register_flags("summary", kdb_summary, "", "Summarize the system", 4, KDB_REPEAT_NONE); - kdb_register_repeat("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", + kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", "Display per_cpu variables", 3, KDB_REPEAT_NONE); - kdb_register_repeat("grephelp", kdb_grep_help, "", + kdb_register_flags("grephelp", kdb_grep_help, "", "Display help on | grep", 0, KDB_REPEAT_NONE); }

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index bd90e1b..1e3b36c 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -127,7 +127,7 @@ static int kdb_ftdump(int argc, const char **argv)

static __init int kdb_ftrace_register(void) { - kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", + kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", "Dump ftrace log", 0, KDB_REPEAT_NONE); return 0; }

-- 1.9.0

Reply

Daniel Thompson

4:29 p.m.

New subject: [RFC v3 6/9] kdb: Remove KDB_REPEAT_NONE flag

From: Anton Vorontsov anton.vorontsov@linaro.org

Since we now treat KDB_REPEAT_* as flags, there is no need to pass KDB_REPEAT_NONE. It's just the default behaviour when no flags are specified.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org --- include/linux/kdb.h | 1 - kernel/debug/kdb/kdb_bp.c | 6 ++--- kernel/debug/kdb/kdb_main.c | 59 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 33 insertions(+), 35 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index f5cc722..4b656d6 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -14,7 +14,6 @@ */

typedef enum { - KDB_REPEAT_NONE = 0, /* Do not repeat this command */ KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ } kdb_cmdflags_t; diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 7be2c5d..87343f0 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -539,11 +539,11 @@ void __init kdb_initbptab(void) kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("bc", kdb_bc, "<bpnum>", - "Clear Breakpoint", 0, KDB_REPEAT_NONE); + "Clear Breakpoint", 0, 0); kdb_register_flags("be", kdb_bc, "<bpnum>", - "Enable Breakpoint", 0, KDB_REPEAT_NONE); + "Enable Breakpoint", 0, 0); kdb_register_flags("bd", kdb_bc, "<bpnum>", - "Disable Breakpoint", 0, KDB_REPEAT_NONE); + "Disable Breakpoint", 0, 0);

kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 5d67ff6..a40b05b 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2698,7 +2698,7 @@ EXPORT_SYMBOL_GPL(kdb_register_flags); /* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_flags with KDB_REPEAT_NONE. + * kdb_register_flags with flags set to 0. * Inputs: * cmd Command name * func Function to execute the command @@ -2713,8 +2713,7 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_flags(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, 0); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2768,68 +2767,68 @@ static void __init kdb_inittab(void) kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[<vaddr>]", - "Continue Execution", 1, KDB_REPEAT_NONE); + "Continue Execution", 1, 0); kdb_register_flags("rd", kdb_rd, "", - "Display Registers", 0, KDB_REPEAT_NONE); + "Display Registers", 0, 0); kdb_register_flags("rm", kdb_rm, "<reg> <contents>", - "Modify Registers", 0, KDB_REPEAT_NONE); + "Modify Registers", 0, 0); kdb_register_flags("ef", kdb_ef, "<vaddr>", - "Display exception frame", 0, KDB_REPEAT_NONE); + "Display exception frame", 0, 0); kdb_register_flags("bt", kdb_bt, "[<vaddr>]", - "Stack traceback", 1, KDB_REPEAT_NONE); + "Stack traceback", 1, 0); kdb_register_flags("btp", kdb_bt, "<pid>", - "Display stack for process <pid>", 0, KDB_REPEAT_NONE); + "Display stack for process <pid>", 0, 0); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); + "Backtrace all processes matching state flag", 0, 0); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); + "Backtrace current process on each cpu", 0, 0); kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, - KDB_REPEAT_NONE); + 0); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, KDB_REPEAT_NONE); + "Show environment variables", 0, 0); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, KDB_REPEAT_NONE); + "Set environment variables", 0, 0); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, KDB_REPEAT_NONE); + "Display Help Message", 1, 0); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, KDB_REPEAT_NONE); + "Display Help Message", 0, 0); kdb_register_flags("cpu", kdb_cpu, "<cpunum>", - "Switch to new cpu", 0, KDB_REPEAT_NONE); + "Switch to new cpu", 0, 0); kdb_register_flags("kgdb", kdb_kgdb, "", - "Enter kgdb mode", 0, KDB_REPEAT_NONE); + "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[<flags>|A]", - "Display active task list", 0, KDB_REPEAT_NONE); + "Display active task list", 0, 0); kdb_register_flags("pid", kdb_pid, "<pidnum>", - "Switch to another task", 0, KDB_REPEAT_NONE); + "Switch to another task", 0, 0); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, KDB_REPEAT_NONE); + "Reboot the machine immediately", 0, 0); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, KDB_REPEAT_NONE); + "List loaded kernel modules", 0, 0); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "<key>", - "Magic SysRq key", 0, KDB_REPEAT_NONE); + "Magic SysRq key", 0, 0); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, KDB_REPEAT_NONE); + "Display syslog buffer", 0, 0); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); + "Disable NMI entry to KDB", 0, 0); } kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", - "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); + "Define a set of commands, down to endefcmd", 0, 0); kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", - "Send a signal to a process", 0, KDB_REPEAT_NONE); + "Send a signal to a process", 0, 0); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, KDB_REPEAT_NONE); + "Summarize the system", 4, 0); kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", - "Display per_cpu variables", 3, KDB_REPEAT_NONE); + "Display per_cpu variables", 3, 0); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, KDB_REPEAT_NONE); + "Display help on | grep", 0, 0); }

/* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 1e3b36c..3da7e30 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, KDB_REPEAT_NONE); + "Dump ftrace log", 0, 0); return 0; }

-- 1.9.0

Reply

Daniel Thompson

4:29 p.m.

New subject: [RFC v3 8/9] kdb: Add enable mask for groups of commands

From: Anton Vorontsov anton.vorontsov@linaro.org

Currently all kdb commands are enabled whenever kdb is deployed. This makes it difficult to deploy kdb to help debug certain types of systems.

Android phones provide one example; the FIQ debugger found on some Android devices has a deliberately weak set of commands to allow the debugger to enabled very late in the production cycle.

Certain kiosk environments offer another interesting case where an engineer might wish to probe the system state using passive inspection commands without providing sufficient power for a passer by to root it.

Without any restrictions, obtaining the root rights via KDB is a matter of a few commands, and works everywhere. For example, log in as a normal user:

cbou:~$ id uid=1001(cbou) gid=1001(cbou) groups=1001(cbou)

Now enter KDB (for example via sysrq):

Entering kdb (current=0xffff8800065bc740, pid 920) due to Keyboard Entry kdb> ps 23 sleeping system daemon (state M) processes suppressed, use 'ps A' to see all. Task Addr Pid Parent [*] cpu State Thread Command 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

0xffff880007078000 1 0 0 0 S 0xffff8800070782e0 init [...snip...] 0xffff8800065be3c0 918 1 0 0 S 0xffff8800065be6a0 getty 0xffff8800065b9c80 919 1 0 0 S 0xffff8800065b9f60 login 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

All we need is the offset of cred pointers. We can look up the offset in the distro's kernel source, but it is unnecessary. We can just start dumping init's task_struct, until we see the process name:

kdb> md 0xffff880007078000 0xffff880007078000 0000000000000001 ffff88000703c000 ................ 0xffff880007078010 0040210000000002 0000000000000000 .....!@......... [...snip...] 0xffff8800070782b0 ffff8800073e0580 ffff8800073e0580 ..>.......>..... 0xffff8800070782c0 0000000074696e69 0000000000000000 init............

^ Here, 'init'. Creds are just above it, so the offset is 0x02b0.

Now we set up init's creds for our non-privileged shell:

kdb> mm 0xffff8800065bc740+0x02b0 0xffff8800073e0580 0xffff8800065bc9f0 = 0xffff8800073e0580 kdb> mm 0xffff8800065bc740+0x02b8 0xffff8800073e0580 0xffff8800065bc9f8 = 0xffff8800073e0580

And thus gaining the root:

kdb> go cbou:~$ id uid=0(root) gid=0(root) groups=0(root) cbou:~$ bash root:~#

p.s. No distro enables kdb by default (although, with a nice KDB-over-KMS feature availability, I would expect at least some would enable it), so it's not actually some kind of a major issue.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- include/linux/kdb.h | 1 + kernel/debug/kdb/kdb_main.c | 30 +++++++++++++++++++++++++++++- 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 2f65c7a..ed323c2 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -109,6 +109,7 @@ extern atomic_t kdb_event; #define KDB_BADLENGTH (-19) #define KDB_NOBP (-20) #define KDB_BADADDR (-21) +#define KDB_NOPERM (-22)

/* * kdb_diemsg diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index e88fbb1..4e9340c 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -12,6 +12,7 @@ */

#include <linux/ctype.h> +#include <linux/types.h> #include <linux/string.h> #include <linux/kernel.h> #include <linux/kmsg_dump.h> @@ -23,6 +24,7 @@ #include <linux/vmalloc.h> #include <linux/atomic.h> #include <linux/module.h> +#include <linux/moduleparam.h> #include <linux/mm.h> #include <linux/init.h> #include <linux/kallsyms.h> @@ -42,6 +44,12 @@ #include <linux/slab.h> #include "kdb_private.h"

+#undef MODULE_PARAM_PREFIX +#define MODULE_PARAM_PREFIX "kdb." + +static int kdb_cmd_enabled; +module_param_named(cmd_enable, kdb_cmd_enabled, int, 0600); + #define GREP_LEN 256 char kdb_grep_string[GREP_LEN]; int kdb_grepping_flag; @@ -121,6 +129,7 @@ static kdbmsg_t kdbmsgs[] = { KDBMSG(BADLENGTH, "Invalid length field"), KDBMSG(NOBP, "No Breakpoint exists"), KDBMSG(BADADDR, "Invalid address"), + KDBMSG(NOPERM, "Permission denied"), }; #undef KDBMSG

@@ -476,6 +485,15 @@ int kdbgetaddrarg(int argc, const char **argv, int *nextarg, kdb_symtab_t symtab;

/* + * If the enable flags prohibit both arbitrary memory access + * and flow control then there are no reasonable grounds to + * provide symbol lookup. + */ + if (!kdb_check_flags(KDB_ENABLE_MEM_READ | KDB_ENABLE_FLOW_CTRL, + kdb_cmd_enabled, false)) + return KDB_NOPERM; + + /* * Process arguments which follow the following syntax: * * symbol | numeric-address [+/- numeric-offset] @@ -1008,6 +1026,10 @@ int kdb_parse(const char *cmdstr)

if (i < kdb_max_commands) { int result; + + if (!kdb_check_flags(tp->cmd_flags, kdb_cmd_enabled, argc <= 1)) + return KDB_NOPERM; + KDB_STATE_SET(CMD); result = (*tp->cmd_func)(argc-1, (const char **)argv); if (result && ignore_errors && result > KDB_CMD_GO) @@ -1919,10 +1941,14 @@ static int kdb_rm(int argc, const char **argv) */ static int kdb_sr(int argc, const char **argv) { + bool check_mask = + !kdb_check_flags(KDB_ENABLE_ALL, kdb_cmd_enabled, false); + if (argc != 1) return KDB_ARGCOUNT; + kdb_trap_printk++; - __handle_sysrq_nolock(*argv[1], false); + __handle_sysrq_nolock(*argv[1], check_mask); kdb_trap_printk--;

return 0; @@ -2373,6 +2399,8 @@ static int kdb_help(int argc, const char **argv) return 0; if (!kt->cmd_name) continue; + if (!kdb_check_flags(kt->cmd_flags, kdb_cmd_enabled, true)) + continue; if (strlen(kt->cmd_usage) > 20) space = "\n "; kdb_printf("%-15.15s %-20s%s%s\n", kt->cmd_name,

-- 1.9.0

Reply

Steven Rostedt

4:45 p.m.

New subject: [RFC v3 1/9] sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb

On Fri, 25 Apr 2014 17:29:22 +0100 Daniel Thompson daniel.thompson@linaro.org wrote:

...

If kdb is triggered using SysRq-g then any use of the sr command results in the SysRq key table lock being recursively acquired, killing the debug session. That patch resolves the problem by introducing a _nolock alternative for __handle_sysrq.

Strictly speaking this approach risks racing on the key table when kdb is triggered by something other than SysRq-g however in that case any other CPU involved should release the spin lock before kgdb parks the slave CPUs.

Is that case documented somewhere in the code comments?

-- Steve

Reply

Daniel Thompson

28 Apr 28 Apr

10:24 a.m.

New subject: [RFC v3 1/9] sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb

On 25/04/14 17:45, Steven Rostedt wrote:

...

On Fri, 25 Apr 2014 17:29:22 +0100 Daniel Thompson daniel.thompson@linaro.org wrote:

...
If kdb is triggered using SysRq-g then any use of the sr command results in the SysRq key table lock being recursively acquired, killing the debug session. That patch resolves the problem by introducing a _nolock alternative for __handle_sysrq.

Strictly speaking this approach risks racing on the key table when kdb is triggered by something other than SysRq-g however in that case any other CPU involved should release the spin lock before kgdb parks the slave CPUs.

Is that case documented somewhere in the code comments?

Perhaps not near enough to the _nolock but the primary bit of comment is here (and in same file as kdb_sr). --- cut here --- * kdb_main_loop - After initial setup and assignment of the * controlling cpu, all cpus are in this loop. One cpu is in * control and will issue the kdb prompt, the others will spin * until 'go' or cpu switch. --- cut here ---

The mechanism kgdb uses to quiesce other CPUs means other CPUs cannot be in irqsave critical sections.

Reply

Colin Cross

5:44 p.m.

New subject: [RFC v3 1/9] sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb

On Mon, Apr 28, 2014 at 3:24 AM, Daniel Thompson daniel.thompson@linaro.org wrote:

...

On 25/04/14 17:45, Steven Rostedt wrote:

...
On Fri, 25 Apr 2014 17:29:22 +0100 Daniel Thompson daniel.thompson@linaro.org wrote:

...
If kdb is triggered using SysRq-g then any use of the sr command results in the SysRq key table lock being recursively acquired, killing the debug session. That patch resolves the problem by introducing a _nolock alternative for __handle_sysrq.

Strictly speaking this approach risks racing on the key table when kdb is triggered by something other than SysRq-g however in that case any other CPU involved should release the spin lock before kgdb parks the slave CPUs.

Is that case documented somewhere in the code comments?

Perhaps not near enough to the _nolock but the primary bit of comment is here (and in same file as kdb_sr). --- cut here ---
kdb_main_loop - After initial setup and assignment of the
 controlling cpu, all cpus are in this loop.  One cpu is in
 control and will issue the kdb prompt, the others will spin
 until 'go' or cpu switch.
--- cut here ---

The mechanism kgdb uses to quiesce other CPUs means other CPUs cannot be in irqsave critical sections.

One of the advantages of FIQ debugger is that it can be triggered from an FIQ (NMI for those in x86 land), and Jason and I have discussed using FIQs for kgdb to allow interrupting cpus stuck in critical sections. If that gets implemented the above assumption will no longer be correct.

Reply

Daniel Thompson

29 Apr 29 Apr

8:59 a.m.

New subject: [RFC v3 1/9] sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb

On 28/04/14 18:44, Colin Cross wrote:

...

...
...
Is that case documented somewhere in the code comments?

Perhaps not near enough to the _nolock but the primary bit of comment is here (and in same file as kdb_sr). --- cut here ---
kdb_main_loop - After initial setup and assignment of the
 controlling cpu, all cpus are in this loop.  One cpu is in
 control and will issue the kdb prompt, the others will spin
 until 'go' or cpu switch.
--- cut here ---

The mechanism kgdb uses to quiesce other CPUs means other CPUs cannot be in irqsave critical sections.
One of the advantages of FIQ debugger is that it can be triggered from an FIQ (NMI for those in x86 land), and Jason and I have discussed using FIQs for kgdb to allow interrupting cpus stuck in critical sections. If that gets implemented the above assumption will no longer be correct.

Reviewing this I realized I missed one of the most critical points in the above.

Today kdb, even if triggered by FIQ/NMI, would still be likely to wedge waiting for the IPI interrupts to be delivered to other processors.

Did you and Jason discuss getting the active CPU to quiesce the other processors using FIQ/NMI, or to allow the active CPU to timeout while waiting for them the stop?

Daniel.

Reply

Daniel Thompson

6 May 6 May

1:03 p.m.

New subject: [PATCH v4 0/9] kdb: Allow selective reduction in capabilities (was "kiosk mode")

This patchset implements restricted modes for the KDB debugger. It is a continuation of previous kiosk mode work of Anton Vorontsov.

It provides a means for the root user to choose the set of kdb commands that are available on the kdb console. It is implemented similarly to the existing code to mask the available magic SysRq commands with modes for disable-all (0), enable-all(1) and a bitmask to enable/disable groups of functionality.

The implementation of the mask check includes a feature to allow command to change which group they belong to based on whether or not the command has arguments (for example, go without arguments is a very safe command whilst go with an argument allows arbitrary changes to the program counter).

There are a few patches, some are just cleanups, some are churn-ish cleanups, but inevitable. And the rest implements the mode -- after all the preparations, everything is pretty straightforward. The first patch is actually a pure bug fix (arguably unrelated to kiosk mode) but collides with the code to honour the SysRq mask when capabilities are restricted so I have included it here.

Changes since v3: * Rebase to latest mainline (3.15rc4). * Improved commenting on safety of calls to __handle_sysrq_nolock * Remove magic shift value in the command categorization values and expressed the flags using shifts to make code review of the defined shift value easier.

Changes since v2: * Fixed stupid build error when CONFIG_KDB[_KIOSK]_DEFAULT_ENABLE was not defined. * Increase flexibility by allowing the userspace greater control over the commands to be restricted. * Removed the "kiosk" terminology. Its confusing.

Changes since v1 (circa 2012):

* ef (Display exception frame) is essentially an overly complex peek and has therefore been marked unsafe * bt (Stack traceback) has been marked safe only with no arguments * sr (Magic SysRq key) honours the sysrq mask when called in kiosk mode * Fixed over-zealous blocking of macro commands * Symbol lookup is forbidden by kdbgetaddrarg (more robust, better error reporting to user) * Fix deadlock in sr (Magic SysRq key) * Better help text in kiosk mode * Default (kiosk on/off) can be changed From the config file.

Anton Vorontsov (6): kdb: Remove currently unused kdbtab_t->cmd_flags kdb: Rename kdb_repeat_t to kdb_cmdflags_t, cmd_repeat to cmd_flags kdb: Rename kdb_register_repeat() to kdb_register_flags() kdb: Use KDB_REPEAT_* values as flags kdb: Remove KDB_REPEAT_NONE flag kdb: Add enable mask for groups of commands

Daniel Thompson (3): sysrq: Implement __handle_sysrq_nolock to avoid recursive locking in kdb kdb: Categorize kdb commands (similar to SysRq categorization) kdb: Allow access to sensitive commands to be restricted by default

-- 1.9.0

Reply

Daniel Thompson

1:03 p.m.

New subject: [PATCH v4 2/9] kdb: Remove currently unused kdbtab_t->cmd_flags

From: Anton Vorontsov anton.vorontsov@linaro.org

The struct member is never used in the code, so we can remove it.

We will introduce real flags soon by renaming cmd_repeat to cmd_flags.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org --- kernel/debug/kdb/kdb_main.c | 1 - kernel/debug/kdb/kdb_private.h | 1 - 2 files changed, 2 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index de439bb..f0a4e69 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2701,7 +2701,6 @@ int kdb_register_repeat(char *cmd, kp->cmd_func = func; kp->cmd_usage = usage; kp->cmd_help = help; - kp->cmd_flags = 0; kp->cmd_minlen = minlen; kp->cmd_repeat = repeat;

diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index 7afd3c8..c4c46c7 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -172,7 +172,6 @@ typedef struct _kdbtab { kdb_func_t cmd_func; /* Function to execute command */ char *cmd_usage; /* Usage String for this command */ char *cmd_help; /* Help message for this command */ - short cmd_flags; /* Parsing flags */ short cmd_minlen; /* Minimum legal # command * chars required */ kdb_repeat_t cmd_repeat; /* Does command auto repeat on enter? */

-- 1.9.0

Reply

Daniel Thompson

1:03 p.m.

New subject: [PATCH v4 4/9] kdb: Rename kdb_register_repeat() to kdb_register_flags()

From: Anton Vorontsov anton.vorontsov@linaro.org

We're about to add more options for commands behaviour, so let's give a more generic name to the low-level kdb command registration function.

There are just various renames, no functional changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- include/linux/kdb.h | 10 +++--- kernel/debug/kdb/kdb_bp.c | 14 ++++---- kernel/debug/kdb/kdb_main.c | 86 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 56 insertions(+), 56 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index e650f79..32d2f40 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -146,17 +146,17 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos)

/* Dynamic kdb shell command registration */ extern int kdb_register(char *, kdb_func_t, char *, char *, short); -extern int kdb_register_repeat(char *, kdb_func_t, char *, char *, - short, kdb_cmdflags_t); +extern int kdb_register_flags(char *, kdb_func_t, char *, char *, + short, kdb_cmdflags_t); extern int kdb_unregister(char *); #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } static inline void kdb_init(int level) {} static inline int kdb_register(char *cmd, kdb_func_t func, char *usage, char *help, short minlen) { return 0; } -static inline int kdb_register_repeat(char *cmd, kdb_func_t func, char *usage, - char *help, short minlen, - kdb_cmdflags_t flags) { return 0; } +static inline int kdb_register_flags(char *cmd, kdb_func_t func, char *usage, + char *help, short minlen, + kdb_cmdflags_t flags) { return 0; } static inline int kdb_unregister(char *cmd) { return 0; } #endif /* CONFIG_KGDB_KDB */ enum { diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 70a5046..7be2c5d 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -531,21 +531,21 @@ void __init kdb_initbptab(void) for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) bp->bp_free = 1;

- kdb_register_repeat("bp", kdb_bp, "[<vaddr>]", + kdb_register_flags("bp", kdb_bp, "[<vaddr>]", "Set/Display breakpoints", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bl", kdb_bp, "[<vaddr>]", + kdb_register_flags("bl", kdb_bp, "[<vaddr>]", "Display breakpoints", 0, KDB_REPEAT_NO_ARGS); if (arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT) - kdb_register_repeat("bph", kdb_bp, "[<vaddr>]", + kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bc", kdb_bc, "<bpnum>", + kdb_register_flags("bc", kdb_bc, "<bpnum>", "Clear Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("be", kdb_bc, "<bpnum>", + kdb_register_flags("be", kdb_bc, "<bpnum>", "Enable Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bd", kdb_bc, "<bpnum>", + kdb_register_flags("bd", kdb_bc, "<bpnum>", "Disable Breakpoint", 0, KDB_REPEAT_NONE);

- kdb_register_repeat("ss", kdb_ss, "", + kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); /* * Architecture dependent initialization. diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 5b7b13a..626c6d2 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2636,7 +2636,7 @@ static int kdb_grep_help(int argc, const char **argv) }

/* - * kdb_register_repeat - This function is used to register a kernel + * kdb_register_flags - This function is used to register a kernel * debugger command. * Inputs: * cmd Command name @@ -2648,12 +2648,12 @@ static int kdb_grep_help(int argc, const char **argv) * zero for success, one if a duplicate command. */ #define kdb_command_extend 50 /* arbitrary */ -int kdb_register_repeat(char *cmd, - kdb_func_t func, - char *usage, - char *help, - short minlen, - kdb_cmdflags_t flags) +int kdb_register_flags(char *cmd, + kdb_func_t func, + char *usage, + char *help, + short minlen, + kdb_cmdflags_t flags) { int i; kdbtab_t *kp; @@ -2706,13 +2706,13 @@ int kdb_register_repeat(char *cmd,

return 0; } -EXPORT_SYMBOL_GPL(kdb_register_repeat); +EXPORT_SYMBOL_GPL(kdb_register_flags);

/* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_repeat with KDB_REPEAT_NONE. + * kdb_register_flags with KDB_REPEAT_NONE. * Inputs: * cmd Command name * func Function to execute the command @@ -2727,8 +2727,8 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_repeat(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, + KDB_REPEAT_NONE); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2770,79 +2770,79 @@ static void __init kdb_inittab(void) for_each_kdbcmd(kp, i) kp->cmd_name = NULL;

- kdb_register_repeat("md", kdb_md, "<vaddr>", + kdb_register_flags("md", kdb_md, "<vaddr>", "Display Memory Contents, also mdWcN, e.g. md8c1", 1, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdr", kdb_md, "<vaddr> <bytes>", + kdb_register_flags("mdr", kdb_md, "<vaddr> <bytes>", "Display Raw Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdp", kdb_md, "<paddr> <bytes>", + kdb_register_flags("mdp", kdb_md, "<paddr> <bytes>", "Display Physical Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mds", kdb_md, "<vaddr>", + kdb_register_flags("mds", kdb_md, "<vaddr>", "Display Memory Symbolically", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mm", kdb_mm, "<vaddr> <contents>", + kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("go", kdb_go, "[<vaddr>]", + kdb_register_flags("go", kdb_go, "[<vaddr>]", "Continue Execution", 1, KDB_REPEAT_NONE); - kdb_register_repeat("rd", kdb_rd, "", + kdb_register_flags("rd", kdb_rd, "", "Display Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("rm", kdb_rm, "<reg> <contents>", + kdb_register_flags("rm", kdb_rm, "<reg> <contents>", "Modify Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ef", kdb_ef, "<vaddr>", + kdb_register_flags("ef", kdb_ef, "<vaddr>", "Display exception frame", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bt", kdb_bt, "[<vaddr>]", + kdb_register_flags("bt", kdb_bt, "[<vaddr>]", "Stack traceback", 1, KDB_REPEAT_NONE); - kdb_register_repeat("btp", kdb_bt, "<pid>", + kdb_register_flags("btp", kdb_bt, "<pid>", "Display stack for process <pid>", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", + kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btc", kdb_bt, "", + kdb_register_flags("btc", kdb_bt, "", "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btt", kdb_bt, "<vaddr>", + kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, KDB_REPEAT_NONE); - kdb_register_repeat("env", kdb_env, "", + kdb_register_flags("env", kdb_env, "", "Show environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("set", kdb_set, "", + kdb_register_flags("set", kdb_set, "", "Set environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("help", kdb_help, "", + kdb_register_flags("help", kdb_help, "", "Display Help Message", 1, KDB_REPEAT_NONE); - kdb_register_repeat("?", kdb_help, "", + kdb_register_flags("?", kdb_help, "", "Display Help Message", 0, KDB_REPEAT_NONE); - kdb_register_repeat("cpu", kdb_cpu, "<cpunum>", + kdb_register_flags("cpu", kdb_cpu, "<cpunum>", "Switch to new cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kgdb", kdb_kgdb, "", + kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ps", kdb_ps, "[<flags>|A]", + kdb_register_flags("ps", kdb_ps, "[<flags>|A]", "Display active task list", 0, KDB_REPEAT_NONE); - kdb_register_repeat("pid", kdb_pid, "<pidnum>", + kdb_register_flags("pid", kdb_pid, "<pidnum>", "Switch to another task", 0, KDB_REPEAT_NONE); - kdb_register_repeat("reboot", kdb_reboot, "", + kdb_register_flags("reboot", kdb_reboot, "", "Reboot the machine immediately", 0, KDB_REPEAT_NONE); #if defined(CONFIG_MODULES) - kdb_register_repeat("lsmod", kdb_lsmod, "", + kdb_register_flags("lsmod", kdb_lsmod, "", "List loaded kernel modules", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_MAGIC_SYSRQ) - kdb_register_repeat("sr", kdb_sr, "<key>", + kdb_register_flags("sr", kdb_sr, "<key>", "Magic SysRq key", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_PRINTK) - kdb_register_repeat("dmesg", kdb_dmesg, "[lines]", + kdb_register_flags("dmesg", kdb_dmesg, "[lines]", "Display syslog buffer", 0, KDB_REPEAT_NONE); #endif if (arch_kgdb_ops.enable_nmi) { - kdb_register_repeat("disable_nmi", kdb_disable_nmi, "", + kdb_register_flags("disable_nmi", kdb_disable_nmi, "", "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); } - kdb_register_repeat("defcmd", kdb_defcmd, "name "usage" "help"", + kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kill", kdb_kill, "<-signal> <pid>", + kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", "Send a signal to a process", 0, KDB_REPEAT_NONE); - kdb_register_repeat("summary", kdb_summary, "", + kdb_register_flags("summary", kdb_summary, "", "Summarize the system", 4, KDB_REPEAT_NONE); - kdb_register_repeat("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", + kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", "Display per_cpu variables", 3, KDB_REPEAT_NONE); - kdb_register_repeat("grephelp", kdb_grep_help, "", + kdb_register_flags("grephelp", kdb_grep_help, "", "Display help on | grep", 0, KDB_REPEAT_NONE); }

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index bd90e1b..1e3b36c 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -127,7 +127,7 @@ static int kdb_ftdump(int argc, const char **argv)

static __init int kdb_ftrace_register(void) { - kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", + kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", "Dump ftrace log", 0, KDB_REPEAT_NONE); return 0; }

-- 1.9.0

Reply

Daniel Thompson

1:03 p.m.

New subject: [PATCH v4 6/9] kdb: Remove KDB_REPEAT_NONE flag

From: Anton Vorontsov anton.vorontsov@linaro.org

Since we now treat KDB_REPEAT_* as flags, there is no need to pass KDB_REPEAT_NONE. It's just the default behaviour when no flags are specified.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org --- include/linux/kdb.h | 1 - kernel/debug/kdb/kdb_bp.c | 6 ++--- kernel/debug/kdb/kdb_main.c | 59 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 33 insertions(+), 35 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 90aed7c..39b44b3 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -14,7 +14,6 @@ */

typedef enum { - KDB_REPEAT_NONE = 0, /* Do not repeat this command */ KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ } kdb_cmdflags_t; diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 7be2c5d..87343f0 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -539,11 +539,11 @@ void __init kdb_initbptab(void) kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("bc", kdb_bc, "<bpnum>", - "Clear Breakpoint", 0, KDB_REPEAT_NONE); + "Clear Breakpoint", 0, 0); kdb_register_flags("be", kdb_bc, "<bpnum>", - "Enable Breakpoint", 0, KDB_REPEAT_NONE); + "Enable Breakpoint", 0, 0); kdb_register_flags("bd", kdb_bc, "<bpnum>", - "Disable Breakpoint", 0, KDB_REPEAT_NONE); + "Disable Breakpoint", 0, 0);

kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 2f54353..41dac47 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2705,7 +2705,7 @@ EXPORT_SYMBOL_GPL(kdb_register_flags); /* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_flags with KDB_REPEAT_NONE. + * kdb_register_flags with flags set to 0. * Inputs: * cmd Command name * func Function to execute the command @@ -2720,8 +2720,7 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_flags(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, 0); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2775,68 +2774,68 @@ static void __init kdb_inittab(void) kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[<vaddr>]", - "Continue Execution", 1, KDB_REPEAT_NONE); + "Continue Execution", 1, 0); kdb_register_flags("rd", kdb_rd, "", - "Display Registers", 0, KDB_REPEAT_NONE); + "Display Registers", 0, 0); kdb_register_flags("rm", kdb_rm, "<reg> <contents>", - "Modify Registers", 0, KDB_REPEAT_NONE); + "Modify Registers", 0, 0); kdb_register_flags("ef", kdb_ef, "<vaddr>", - "Display exception frame", 0, KDB_REPEAT_NONE); + "Display exception frame", 0, 0); kdb_register_flags("bt", kdb_bt, "[<vaddr>]", - "Stack traceback", 1, KDB_REPEAT_NONE); + "Stack traceback", 1, 0); kdb_register_flags("btp", kdb_bt, "<pid>", - "Display stack for process <pid>", 0, KDB_REPEAT_NONE); + "Display stack for process <pid>", 0, 0); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); + "Backtrace all processes matching state flag", 0, 0); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); + "Backtrace current process on each cpu", 0, 0); kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, - KDB_REPEAT_NONE); + 0); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, KDB_REPEAT_NONE); + "Show environment variables", 0, 0); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, KDB_REPEAT_NONE); + "Set environment variables", 0, 0); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, KDB_REPEAT_NONE); + "Display Help Message", 1, 0); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, KDB_REPEAT_NONE); + "Display Help Message", 0, 0); kdb_register_flags("cpu", kdb_cpu, "<cpunum>", - "Switch to new cpu", 0, KDB_REPEAT_NONE); + "Switch to new cpu", 0, 0); kdb_register_flags("kgdb", kdb_kgdb, "", - "Enter kgdb mode", 0, KDB_REPEAT_NONE); + "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[<flags>|A]", - "Display active task list", 0, KDB_REPEAT_NONE); + "Display active task list", 0, 0); kdb_register_flags("pid", kdb_pid, "<pidnum>", - "Switch to another task", 0, KDB_REPEAT_NONE); + "Switch to another task", 0, 0); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, KDB_REPEAT_NONE); + "Reboot the machine immediately", 0, 0); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, KDB_REPEAT_NONE); + "List loaded kernel modules", 0, 0); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "<key>", - "Magic SysRq key", 0, KDB_REPEAT_NONE); + "Magic SysRq key", 0, 0); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, KDB_REPEAT_NONE); + "Display syslog buffer", 0, 0); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); + "Disable NMI entry to KDB", 0, 0); } kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", - "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); + "Define a set of commands, down to endefcmd", 0, 0); kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", - "Send a signal to a process", 0, KDB_REPEAT_NONE); + "Send a signal to a process", 0, 0); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, KDB_REPEAT_NONE); + "Summarize the system", 4, 0); kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", - "Display per_cpu variables", 3, KDB_REPEAT_NONE); + "Display per_cpu variables", 3, 0); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, KDB_REPEAT_NONE); + "Display help on | grep", 0, 0); }

/* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 1e3b36c..3da7e30 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, KDB_REPEAT_NONE); + "Dump ftrace log", 0, 0); return 0; }

-- 1.9.0

Reply

Daniel Thompson

1:03 p.m.

New subject: [PATCH v4 8/9] kdb: Add enable mask for groups of commands

From: Anton Vorontsov anton.vorontsov@linaro.org

Currently all kdb commands are enabled whenever kdb is deployed. This makes it difficult to deploy kdb to help debug certain types of systems.

Android phones provide one example; the FIQ debugger found on some Android devices has a deliberately weak set of commands to allow the debugger to enabled very late in the production cycle.

Certain kiosk environments offer another interesting case where an engineer might wish to probe the system state using passive inspection commands without providing sufficient power for a passer by to root it.

Without any restrictions, obtaining the root rights via KDB is a matter of a few commands, and works everywhere. For example, log in as a normal user:

cbou:~$ id uid=1001(cbou) gid=1001(cbou) groups=1001(cbou)

Now enter KDB (for example via sysrq):

Entering kdb (current=0xffff8800065bc740, pid 920) due to Keyboard Entry kdb> ps 23 sleeping system daemon (state M) processes suppressed, use 'ps A' to see all. Task Addr Pid Parent [*] cpu State Thread Command 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

0xffff880007078000 1 0 0 0 S 0xffff8800070782e0 init [...snip...] 0xffff8800065be3c0 918 1 0 0 S 0xffff8800065be6a0 getty 0xffff8800065b9c80 919 1 0 0 S 0xffff8800065b9f60 login 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

All we need is the offset of cred pointers. We can look up the offset in the distro's kernel source, but it is unnecessary. We can just start dumping init's task_struct, until we see the process name:

kdb> md 0xffff880007078000 0xffff880007078000 0000000000000001 ffff88000703c000 ................ 0xffff880007078010 0040210000000002 0000000000000000 .....!@......... [...snip...] 0xffff8800070782b0 ffff8800073e0580 ffff8800073e0580 ..>.......>..... 0xffff8800070782c0 0000000074696e69 0000000000000000 init............

^ Here, 'init'. Creds are just above it, so the offset is 0x02b0.

Now we set up init's creds for our non-privileged shell:

kdb> mm 0xffff8800065bc740+0x02b0 0xffff8800073e0580 0xffff8800065bc9f0 = 0xffff8800073e0580 kdb> mm 0xffff8800065bc740+0x02b8 0xffff8800073e0580 0xffff8800065bc9f8 = 0xffff8800073e0580

And thus gaining the root:

kdb> go cbou:~$ id uid=0(root) gid=0(root) groups=0(root) cbou:~$ bash root:~#

p.s. No distro enables kdb by default (although, with a nice KDB-over-KMS feature availability, I would expect at least some would enable it), so it's not actually some kind of a major issue.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- include/linux/kdb.h | 1 + kernel/debug/kdb/kdb_main.c | 30 +++++++++++++++++++++++++++++- 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 08f9875..0872b35 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -125,6 +125,7 @@ extern atomic_t kdb_event; #define KDB_BADLENGTH (-19) #define KDB_NOBP (-20) #define KDB_BADADDR (-21) +#define KDB_NOPERM (-22)

/* * kdb_diemsg diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index dcf45a9..4a82dc3 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -12,6 +12,7 @@ */

#include <linux/ctype.h> +#include <linux/types.h> #include <linux/string.h> #include <linux/kernel.h> #include <linux/kmsg_dump.h> @@ -23,6 +24,7 @@ #include <linux/vmalloc.h> #include <linux/atomic.h> #include <linux/module.h> +#include <linux/moduleparam.h> #include <linux/mm.h> #include <linux/init.h> #include <linux/kallsyms.h> @@ -42,6 +44,12 @@ #include <linux/slab.h> #include "kdb_private.h"

+#undef MODULE_PARAM_PREFIX +#define MODULE_PARAM_PREFIX "kdb." + +static int kdb_cmd_enabled; +module_param_named(cmd_enable, kdb_cmd_enabled, int, 0600); + #define GREP_LEN 256 char kdb_grep_string[GREP_LEN]; int kdb_grepping_flag; @@ -121,6 +129,7 @@ static kdbmsg_t kdbmsgs[] = { KDBMSG(BADLENGTH, "Invalid length field"), KDBMSG(NOBP, "No Breakpoint exists"), KDBMSG(BADADDR, "Invalid address"), + KDBMSG(NOPERM, "Permission denied"), }; #undef KDBMSG

@@ -476,6 +485,15 @@ int kdbgetaddrarg(int argc, const char **argv, int *nextarg, kdb_symtab_t symtab;

/* + * If the enable flags prohibit both arbitrary memory access + * and flow control then there are no reasonable grounds to + * provide symbol lookup. + */ + if (!kdb_check_flags(KDB_ENABLE_MEM_READ | KDB_ENABLE_FLOW_CTRL, + kdb_cmd_enabled, false)) + return KDB_NOPERM; + + /* * Process arguments which follow the following syntax: * * symbol | numeric-address [+/- numeric-offset] @@ -1008,6 +1026,10 @@ int kdb_parse(const char *cmdstr)

if (i < kdb_max_commands) { int result; + + if (!kdb_check_flags(tp->cmd_flags, kdb_cmd_enabled, argc <= 1)) + return KDB_NOPERM; + KDB_STATE_SET(CMD); result = (*tp->cmd_func)(argc-1, (const char **)argv); if (result && ignore_errors && result > KDB_CMD_GO) @@ -1926,10 +1948,14 @@ static int kdb_rm(int argc, const char **argv) */ static int kdb_sr(int argc, const char **argv) { + bool check_mask = + !kdb_check_flags(KDB_ENABLE_ALL, kdb_cmd_enabled, false); + if (argc != 1) return KDB_ARGCOUNT; + kdb_trap_printk++; - __handle_sysrq_nolock(*argv[1], false); + __handle_sysrq_nolock(*argv[1], check_mask); kdb_trap_printk--;

return 0; @@ -2380,6 +2406,8 @@ static int kdb_help(int argc, const char **argv) return 0; if (!kt->cmd_name) continue; + if (!kdb_check_flags(kt->cmd_flags, kdb_cmd_enabled, true)) + continue; if (strlen(kt->cmd_usage) > 20) space = "\n "; kdb_printf("%-15.15s %-20s%s%s\n", kt->cmd_name,

-- 1.9.0

Reply

Daniel Thompson

19 Jun 19 Jun

1:19 p.m.

New subject: [PATCH v5 0/8] kdb: Allow selective reduction in capabilities (was "kiosk mode")

This patchset implements restricted modes for the KDB debugger. It is a continuation of previous kiosk mode work of Anton Vorontsov. There are no outstanding review comments for this patchset.

It provides a means for the root user to choose the set of kdb commands that are available on the kdb console. It is implemented similarly to the existing code to mask the available magic SysRq commands with modes for disable-all (0), enable-all(1) and a bitmask to enable/disable groups of functionality.

The implementation of the mask check includes a feature to allow command to change which group they belong to based on whether or not the command has arguments (for example, go without arguments is a very safe command whilst go with an argument allows arbitrary changes to the program counter).

There are a few patches, some are just cleanups, some are churn-ish cleanups, but inevitable. And the rest implements the mode -- after all the preparations, everything is pretty straightforward. The first patch is actually a pure bug fix (arguably unrelated to kiosk mode) but collides with the code to honour the SysRq mask when capabilities are restricted so I have included it here.

Changes since v4: * Rebase to 3.16rc1. * Drop patches to avoid deadlock on sysrq spin lock (Rik van Riel's 984d74a... is a much better approach).

Changes since v3: * Rebase to latest mainline (3.15rc4). * Improved commenting on safety of calls to __handle_sysrq_nolock * Remove magic shift value in the command categorization values and expressed the flags using shifts to make code review of the defined shift value easier.

Changes since v2: * Fixed stupid build error when CONFIG_KDB[_KIOSK]_DEFAULT_ENABLE was not defined. * Increase flexibility by allowing the userspace greater control over the commands to be restricted. * Removed the "kiosk" terminology. Its confusing.

Changes since v1 (circa 2012):

* ef (Display exception frame) is essentially an overly complex peek and has therefore been marked unsafe * bt (Stack traceback) has been marked safe only with no arguments * sr (Magic SysRq key) honours the sysrq mask when called in kiosk mode * Fixed over-zealous blocking of macro commands * Symbol lookup is forbidden by kdbgetaddrarg (more robust, better error reporting to user) * Fix deadlock in sr (Magic SysRq key) * Better help text in kiosk mode * Default (kiosk on/off) can be changed From the config file.

Anton Vorontsov (6): kdb: Remove currently unused kdbtab_t->cmd_flags kdb: Rename kdb_repeat_t to kdb_cmdflags_t, cmd_repeat to cmd_flags kdb: Rename kdb_register_repeat() to kdb_register_flags() kdb: Use KDB_REPEAT_* values as flags kdb: Remove KDB_REPEAT_NONE flag kdb: Add enable mask for groups of commands

Daniel Thompson (2): kdb: Categorize kdb commands (similar to SysRq categorization) kdb: Allow access to sensitive commands to be restricted by default

-- 1.9.3

Reply

Daniel Thompson

1:19 p.m.

New subject: [PATCH v5 2/8] kdb: Rename kdb_repeat_t to kdb_cmdflags_t, cmd_repeat to cmd_flags

From: Anton Vorontsov anton.vorontsov@linaro.org

We're about to add more options for command behaviour, so let's expand the meaning of kdb_repeat_t.

So far we just do various renames, there should be no functional changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Mike Travis travis@sgi.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 6 +++--- kernel/debug/kdb/kdb_main.c | 6 +++--- kernel/debug/kdb/kdb_private.h | 2 +- 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 290db12..e650f79 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -17,7 +17,7 @@ typedef enum { KDB_REPEAT_NONE = 0, /* Do not repeat this command */ KDB_REPEAT_NO_ARGS, /* Repeat the command without arguments */ KDB_REPEAT_WITH_ARGS, /* Repeat the command including its arguments */ -} kdb_repeat_t; +} kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **);

@@ -147,7 +147,7 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos) /* Dynamic kdb shell command registration */ extern int kdb_register(char *, kdb_func_t, char *, char *, short); extern int kdb_register_repeat(char *, kdb_func_t, char *, char *, - short, kdb_repeat_t); + short, kdb_cmdflags_t); extern int kdb_unregister(char *); #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } @@ -156,7 +156,7 @@ static inline int kdb_register(char *cmd, kdb_func_t func, char *usage, char *help, short minlen) { return 0; } static inline int kdb_register_repeat(char *cmd, kdb_func_t func, char *usage, char *help, short minlen, - kdb_repeat_t repeat) { return 0; } + kdb_cmdflags_t flags) { return 0; } static inline int kdb_unregister(char *cmd) { return 0; } #endif /* CONFIG_KGDB_KDB */ enum { diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 0b28bb0..05c4abc 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1008,7 +1008,7 @@ int kdb_parse(const char *cmdstr) if (result && ignore_errors && result > KDB_CMD_GO) result = 0; KDB_STATE_CLEAR(CMD); - switch (tp->cmd_repeat) { + switch (tp->cmd_flags) { case KDB_REPEAT_NONE: argc = 0; if (argv[0]) @@ -2646,7 +2646,7 @@ int kdb_register_repeat(char *cmd, char *usage, char *help, short minlen, - kdb_repeat_t repeat) + kdb_cmdflags_t flags) { int i; kdbtab_t *kp; @@ -2695,7 +2695,7 @@ int kdb_register_repeat(char *cmd, kp->cmd_usage = usage; kp->cmd_help = help; kp->cmd_minlen = minlen; - kp->cmd_repeat = repeat; + kp->cmd_flags = flags;

return 0; } diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index c4c46c7..eaacd16 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -174,7 +174,7 @@ typedef struct _kdbtab { char *cmd_help; /* Help message for this command */ short cmd_minlen; /* Minimum legal # command * chars required */ - kdb_repeat_t cmd_repeat; /* Does command auto repeat on enter? */ + kdb_cmdflags_t cmd_flags; /* Command behaviour flags */ } kdbtab_t;

extern int kdb_bt(int, const char **); /* KDB display back trace */

-- 1.9.3

Reply

Daniel Thompson

1:19 p.m.

New subject: [PATCH v5 4/8] kdb: Use KDB_REPEAT_* values as flags

From: Anton Vorontsov anton.vorontsov@linaro.org

The actual values of KDB_REPEAT_* enum values and overall logic stayed the same, but we now treat the values as flags.

This makes it possible to add other flags and combine them, plus makes the code a lot simpler and shorter. But functionality-wise, there should be no changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Mike Travis travis@sgi.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 4 ++-- kernel/debug/kdb/kdb_main.c | 21 +++++++-------------- 2 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 32d2f40..90aed7c 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -15,8 +15,8 @@

typedef enum { KDB_REPEAT_NONE = 0, /* Do not repeat this command */ - KDB_REPEAT_NO_ARGS, /* Repeat the command without arguments */ - KDB_REPEAT_WITH_ARGS, /* Repeat the command including its arguments */ + KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ + KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ } kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 6b33f9c..7a0a65c 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1008,20 +1008,13 @@ int kdb_parse(const char *cmdstr) if (result && ignore_errors && result > KDB_CMD_GO) result = 0; KDB_STATE_CLEAR(CMD); - switch (tp->cmd_flags) { - case KDB_REPEAT_NONE: - argc = 0; - if (argv[0]) - *(argv[0]) = '\0'; - break; - case KDB_REPEAT_NO_ARGS: - argc = 1; - if (argv[1]) - *(argv[1]) = '\0'; - break; - case KDB_REPEAT_WITH_ARGS: - break; - } + + if (tp->cmd_flags & KDB_REPEAT_WITH_ARGS) + return result; + + argc = tp->cmd_flags & KDB_REPEAT_NO_ARGS ? 1 : 0; + if (argv[argc]) + *(argv[argc]) = '\0'; return result; }

-- 1.9.3

Reply

Daniel Thompson

1:19 p.m.

New subject: [PATCH v5 6/8] kdb: Categorize kdb commands (similar to SysRq categorization)

This patch introduces several new flags to collect kdb commands into groups (later allowing them to be optionally disabled).

This follows similar prior art to enable/disable magic sysrq commands.

The commands have been categorized as follows:

Always on: go (w/o args), env, set, help, ?, cpu (w/o args), sr, dmesg, disable_nmi, defcmd, summary, grephelp Mem read: md, mdr, mdp, mds, ef, bt (with args), per_cpu Mem write: mm Reg read: rd Reg write: go (with args), rm Inspect: bt (w/o args), btp, bta, btc, btt, ps, pid, lsmod Flow ctrl: bp, bl, bph, bc, be, bd, ss Signal: kill Reboot: reboot All: cpu, kgdb, (and all of the above), nmi_console

Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Ingo Molnar mingo@redhat.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 48 +++++++++++++++++- kernel/debug/kdb/kdb_bp.c | 21 +++++--- kernel/debug/kdb/kdb_main.c | 120 ++++++++++++++++++++++++++++++++------------ kernel/trace/trace_kdb.c | 2 +- 4 files changed, 148 insertions(+), 43 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 39b44b3..f1fe361 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -13,9 +13,53 @@ * Copyright (C) 2009 Jason Wessel jason.wessel@windriver.com */

+/* Shifted versions of the command enable bits are be used if the command + * has no arguments (see kdb_check_flags). This allows commands, such as + * go, to have different permissions depending upon whether it is called + * with an argument. + */ +#define KDB_ENABLE_NO_ARGS_SHIFT 10 + typedef enum { - KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ - KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ + KDB_ENABLE_ALL = (1 << 0), /* Enable everything */ + KDB_ENABLE_MEM_READ = (1 << 1), + KDB_ENABLE_MEM_WRITE = (1 << 2), + KDB_ENABLE_REG_READ = (1 << 3), + KDB_ENABLE_REG_WRITE = (1 << 4), + KDB_ENABLE_INSPECT = (1 << 5), + KDB_ENABLE_FLOW_CTRL = (1 << 6), + KDB_ENABLE_SIGNAL = (1 << 7), + KDB_ENABLE_REBOOT = (1 << 8), + /* User exposed values stop here, all remaining flags are + * exclusively used to describe a commands behaviour. + */ + + KDB_ENABLE_ALWAYS_SAFE = (1 << 9), + KDB_ENABLE_MASK = (1 << KDB_ENABLE_NO_ARGS_SHIFT) - 1, + + KDB_ENABLE_ALL_NO_ARGS = KDB_ENABLE_ALL << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_MEM_READ_NO_ARGS = KDB_ENABLE_MEM_READ + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_MEM_WRITE_NO_ARGS = KDB_ENABLE_MEM_WRITE + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_REG_READ_NO_ARGS = KDB_ENABLE_REG_READ + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_REG_WRITE_NO_ARGS = KDB_ENABLE_REG_WRITE + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_INSPECT_NO_ARGS = KDB_ENABLE_INSPECT + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_FLOW_CTRL_NO_ARGS = KDB_ENABLE_FLOW_CTRL + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_SIGNAL_NO_ARGS = KDB_ENABLE_SIGNAL + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_REBOOT_NO_ARGS = KDB_ENABLE_REBOOT + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_ALWAYS_SAFE_NO_ARGS = KDB_ENABLE_ALWAYS_SAFE + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_MASK_NO_ARGS = KDB_ENABLE_MASK << KDB_ENABLE_NO_ARGS_SHIFT, + + KDB_REPEAT_NO_ARGS = 0x40000000, /* Repeat the command w/o arguments */ + KDB_REPEAT_WITH_ARGS = 0x80000000, /* Repeat the command with args */ } kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **); diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 87343f0..f5b3d89 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -532,21 +532,28 @@ void __init kdb_initbptab(void) bp->bp_free = 1;

kdb_register_flags("bp", kdb_bp, "[<vaddr>]", - "Set/Display breakpoints", 0, KDB_REPEAT_NO_ARGS); + "Set/Display breakpoints", 0, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); kdb_register_flags("bl", kdb_bp, "[<vaddr>]", - "Display breakpoints", 0, KDB_REPEAT_NO_ARGS); + "Display breakpoints", 0, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); if (arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT) kdb_register_flags("bph", kdb_bp, "[<vaddr>]", - "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); + "[datar [length]|dataw [length]] Set hw brk", 0, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); kdb_register_flags("bc", kdb_bc, "<bpnum>", - "Clear Breakpoint", 0, 0); + "Clear Breakpoint", 0, + KDB_ENABLE_FLOW_CTRL); kdb_register_flags("be", kdb_bc, "<bpnum>", - "Enable Breakpoint", 0, 0); + "Enable Breakpoint", 0, + KDB_ENABLE_FLOW_CTRL); kdb_register_flags("bd", kdb_bc, "<bpnum>", - "Disable Breakpoint", 0, 0); + "Disable Breakpoint", 0, + KDB_ENABLE_FLOW_CTRL);

kdb_register_flags("ss", kdb_ss, "", - "Single Step", 1, KDB_REPEAT_NO_ARGS); + "Single Step", 1, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); /* * Architecture dependent initialization. */ diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index fa31ccc..941ff97 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -188,6 +188,26 @@ struct task_struct *kdb_curr_task(int cpu) }

/* + * Check whether the flags of the current command and the permissions + * of the kdb console has allow a command to be run. + */ +static inline bool kdb_check_flags(kdb_cmdflags_t flags, int permissions, + bool no_args) +{ + /* permissions comes from userspace so needs massaging slightly */ + permissions &= KDB_ENABLE_MASK; + permissions |= KDB_ENABLE_ALWAYS_SAFE; + + /* some commands change group when launched with no arguments */ + if (no_args) + permissions |= permissions << KDB_ENABLE_NO_ARGS_SHIFT; + + flags |= KDB_ENABLE_ALL; + + return permissions & flags; +} + +/* * kdbgetenv - This function will return the character string value of * an environment variable. * Parameters: @@ -641,8 +661,13 @@ static int kdb_defcmd2(const char *cmdstr, const char *argv0) if (!s->count) s->usable = 0; if (s->usable) - kdb_register(s->name, kdb_exec_defcmd, - s->usage, s->help, 0); + /* macros are always safe because when executed each + * internal command re-enters kdb_parse() and is + * safety checked individually. + */ + kdb_register_flags(s->name, kdb_exec_defcmd, s->usage, + s->help, 0, + KDB_ENABLE_ALWAYS_SAFE); return 0; } if (!s->usable) @@ -2757,78 +2782,107 @@ static void __init kdb_inittab(void)

kdb_register_flags("md", kdb_md, "<vaddr>", "Display Memory Contents, also mdWcN, e.g. md8c1", 1, - KDB_REPEAT_NO_ARGS); + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mdr", kdb_md, "<vaddr> <bytes>", - "Display Raw Memory", 0, KDB_REPEAT_NO_ARGS); + "Display Raw Memory", 0, + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mdp", kdb_md, "<paddr> <bytes>", - "Display Physical Memory", 0, KDB_REPEAT_NO_ARGS); + "Display Physical Memory", 0, + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mds", kdb_md, "<vaddr>", - "Display Memory Symbolically", 0, KDB_REPEAT_NO_ARGS); + "Display Memory Symbolically", 0, + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", - "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); + "Modify Memory Contents", 0, + KDB_ENABLE_MEM_WRITE | KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[<vaddr>]", - "Continue Execution", 1, 0); + "Continue Execution", 1, + KDB_ENABLE_REG_WRITE | KDB_ENABLE_ALWAYS_SAFE_NO_ARGS); kdb_register_flags("rd", kdb_rd, "", - "Display Registers", 0, 0); + "Display Registers", 0, + KDB_ENABLE_REG_READ); kdb_register_flags("rm", kdb_rm, "<reg> <contents>", - "Modify Registers", 0, 0); + "Modify Registers", 0, + KDB_ENABLE_REG_WRITE); kdb_register_flags("ef", kdb_ef, "<vaddr>", - "Display exception frame", 0, 0); + "Display exception frame", 0, + KDB_ENABLE_MEM_READ); kdb_register_flags("bt", kdb_bt, "[<vaddr>]", - "Stack traceback", 1, 0); + "Stack traceback", 1, + KDB_ENABLE_MEM_READ | KDB_ENABLE_INSPECT_NO_ARGS); kdb_register_flags("btp", kdb_bt, "<pid>", - "Display stack for process <pid>", 0, 0); + "Display stack for process <pid>", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, 0); + "Backtrace all processes matching state flag", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, 0); + "Backtrace current process on each cpu", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, - 0); + KDB_ENABLE_MEM_READ | KDB_ENABLE_INSPECT_NO_ARGS); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, 0); + "Show environment variables", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, 0); + "Set environment variables", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, 0); + "Display Help Message", 1, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, 0); + "Display Help Message", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("cpu", kdb_cpu, "<cpunum>", - "Switch to new cpu", 0, 0); + "Switch to new cpu", 0, + KDB_ENABLE_ALWAYS_SAFE_NO_ARGS); kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[<flags>|A]", - "Display active task list", 0, 0); + "Display active task list", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("pid", kdb_pid, "<pidnum>", - "Switch to another task", 0, 0); + "Switch to another task", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, 0); + "Reboot the machine immediately", 0, + KDB_ENABLE_REBOOT); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, 0); + "List loaded kernel modules", 0, + KDB_ENABLE_INSPECT); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "<key>", - "Magic SysRq key", 0, 0); + "Magic SysRq key", 0, + KDB_ENABLE_ALWAYS_SAFE); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, 0); + "Display syslog buffer", 0, + KDB_ENABLE_ALWAYS_SAFE); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, 0); + "Disable NMI entry to KDB", 0, + KDB_ENABLE_ALWAYS_SAFE); } kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", - "Define a set of commands, down to endefcmd", 0, 0); + "Define a set of commands, down to endefcmd", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", - "Send a signal to a process", 0, 0); + "Send a signal to a process", 0, + KDB_ENABLE_SIGNAL); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, 0); + "Summarize the system", 4, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", - "Display per_cpu variables", 3, 0); + "Display per_cpu variables", 3, + KDB_ENABLE_MEM_READ); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, 0); + "Display help on | grep", 0, + KDB_ENABLE_ALWAYS_SAFE); }

/* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 3da7e30..1058f6b 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, 0); + "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE); return 0; }

-- 1.9.3

Reply

Daniel Thompson

1:19 p.m.

New subject: [PATCH v5 8/8] kdb: Allow access to sensitive commands to be restricted by default

Currently kiosk mode must be explicitly requested by the bootloader or userspace. It is convenient to be able to change the default value in a similar manner to CONFIG_MAGIC_SYSRQ_DEFAULT_MASK.

Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: kgdb-bugreport@lists.sourceforge.net --- kernel/debug/kdb/kdb_main.c | 2 +- lib/Kconfig.kgdb | 25 +++++++++++++++++++++++++ 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index c670fe4..a11a26b 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -47,7 +47,7 @@ #undef MODULE_PARAM_PREFIX #define MODULE_PARAM_PREFIX "kdb."

-static int kdb_cmd_enabled; +static int kdb_cmd_enabled = CONFIG_KDB_DEFAULT_ENABLE; module_param_named(cmd_enable, kdb_cmd_enabled, int, 0600);

#define GREP_LEN 256 diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb index 358eb81..fbbcff6 100644 --- a/lib/Kconfig.kgdb +++ b/lib/Kconfig.kgdb @@ -73,6 +73,31 @@ config KGDB_KDB help KDB frontend for kernel

+config KDB_DEFAULT_ENABLE + hex "KDB: Select kdb command functions to be enabled by default" + depends on KGDB_KDB + default 0x1 + help + Specifiers which kdb commands are enabled by default. This may + be set to 1 or 0 to enable all commands or disable almost all + commands. + + Alternatively the following bitmask applies: + + 0x0002 - allow arbitrary reads from memory and symbol lookup + 0x0004 - allow arbitrary writes to memory + 0x0008 - allow current register state to be inspected + 0x0010 - allow current register state to be modified + 0x0020 - allow passive inspection (backtrace, process list, lsmod) + 0x0040 - allow flow control management (breakpoint, single step) + 0x0080 - enable signalling of processes + 0x0100 - allow machine to be rebooted + + The config option merely sets the default at boot time. Both + issuing 'echo X > /sys/module/kdb/parameters/kdb.cmd_enable' or + setting with kdb.cmd_enable=X kernel command line option will + override the default settings. + config KDB_KEYBOARD bool "KGDB_KDB: keyboard as input device" depends on VT && KGDB_KDB

-- 1.9.3

Reply

Daniel Thompson

11:33 a.m.

New subject: [RESEND PATCH v5 3.16-rc4 1/8] kdb: Remove currently unused kdbtab_t->cmd_flags

From: Anton Vorontsov anton.vorontsov@linaro.org

The struct member is never used in the code, so we can remove it.

We will introduce real flags soon by renaming cmd_repeat to cmd_flags.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@liaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Ingo Molnar mingo@kernel.org Cc: kgdb-bugreport@lists.sourceforge.net --- kernel/debug/kdb/kdb_main.c | 1 - kernel/debug/kdb/kdb_private.h | 1 - 2 files changed, 2 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 2f7c760..0b28bb0 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2694,7 +2694,6 @@ int kdb_register_repeat(char *cmd, kp->cmd_func = func; kp->cmd_usage = usage; kp->cmd_help = help; - kp->cmd_flags = 0; kp->cmd_minlen = minlen; kp->cmd_repeat = repeat;

diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index 7afd3c8..c4c46c7 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -172,7 +172,6 @@ typedef struct _kdbtab { kdb_func_t cmd_func; /* Function to execute command */ char *cmd_usage; /* Usage String for this command */ char *cmd_help; /* Help message for this command */ - short cmd_flags; /* Parsing flags */ short cmd_minlen; /* Minimum legal # command * chars required */ kdb_repeat_t cmd_repeat; /* Does command auto repeat on enter? */

-- 1.9.3

Reply

Daniel Thompson

11:33 a.m.

New subject: [RESEND PATCH v5 3.16-rc4 3/8] kdb: Rename kdb_register_repeat() to kdb_register_flags()

From: Anton Vorontsov anton.vorontsov@linaro.org

We're about to add more options for commands behaviour, so let's give a more generic name to the low-level kdb command registration function.

There are just various renames, no functional changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Ingo Molnar mingo@redhat.com Cc: Mike Travis travis@sgi.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 10 +++--- kernel/debug/kdb/kdb_bp.c | 14 ++++---- kernel/debug/kdb/kdb_main.c | 86 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 56 insertions(+), 56 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index e650f79..32d2f40 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -146,17 +146,17 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos)

/* Dynamic kdb shell command registration */ extern int kdb_register(char *, kdb_func_t, char *, char *, short); -extern int kdb_register_repeat(char *, kdb_func_t, char *, char *, - short, kdb_cmdflags_t); +extern int kdb_register_flags(char *, kdb_func_t, char *, char *, + short, kdb_cmdflags_t); extern int kdb_unregister(char *); #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } static inline void kdb_init(int level) {} static inline int kdb_register(char *cmd, kdb_func_t func, char *usage, char *help, short minlen) { return 0; } -static inline int kdb_register_repeat(char *cmd, kdb_func_t func, char *usage, - char *help, short minlen, - kdb_cmdflags_t flags) { return 0; } +static inline int kdb_register_flags(char *cmd, kdb_func_t func, char *usage, + char *help, short minlen, + kdb_cmdflags_t flags) { return 0; } static inline int kdb_unregister(char *cmd) { return 0; } #endif /* CONFIG_KGDB_KDB */ enum { diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 70a5046..7be2c5d 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -531,21 +531,21 @@ void __init kdb_initbptab(void) for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) bp->bp_free = 1;

- kdb_register_repeat("bp", kdb_bp, "[<vaddr>]", + kdb_register_flags("bp", kdb_bp, "[<vaddr>]", "Set/Display breakpoints", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bl", kdb_bp, "[<vaddr>]", + kdb_register_flags("bl", kdb_bp, "[<vaddr>]", "Display breakpoints", 0, KDB_REPEAT_NO_ARGS); if (arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT) - kdb_register_repeat("bph", kdb_bp, "[<vaddr>]", + kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bc", kdb_bc, "<bpnum>", + kdb_register_flags("bc", kdb_bc, "<bpnum>", "Clear Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("be", kdb_bc, "<bpnum>", + kdb_register_flags("be", kdb_bc, "<bpnum>", "Enable Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bd", kdb_bc, "<bpnum>", + kdb_register_flags("bd", kdb_bc, "<bpnum>", "Disable Breakpoint", 0, KDB_REPEAT_NONE);

- kdb_register_repeat("ss", kdb_ss, "", + kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); /* * Architecture dependent initialization. diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 05c4abc..6b33f9c 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2629,7 +2629,7 @@ static int kdb_grep_help(int argc, const char **argv) }

/* - * kdb_register_repeat - This function is used to register a kernel + * kdb_register_flags - This function is used to register a kernel * debugger command. * Inputs: * cmd Command name @@ -2641,12 +2641,12 @@ static int kdb_grep_help(int argc, const char **argv) * zero for success, one if a duplicate command. */ #define kdb_command_extend 50 /* arbitrary */ -int kdb_register_repeat(char *cmd, - kdb_func_t func, - char *usage, - char *help, - short minlen, - kdb_cmdflags_t flags) +int kdb_register_flags(char *cmd, + kdb_func_t func, + char *usage, + char *help, + short minlen, + kdb_cmdflags_t flags) { int i; kdbtab_t *kp; @@ -2699,13 +2699,13 @@ int kdb_register_repeat(char *cmd,

return 0; } -EXPORT_SYMBOL_GPL(kdb_register_repeat); +EXPORT_SYMBOL_GPL(kdb_register_flags);

/* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_repeat with KDB_REPEAT_NONE. + * kdb_register_flags with KDB_REPEAT_NONE. * Inputs: * cmd Command name * func Function to execute the command @@ -2720,8 +2720,8 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_repeat(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, + KDB_REPEAT_NONE); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2763,79 +2763,79 @@ static void __init kdb_inittab(void) for_each_kdbcmd(kp, i) kp->cmd_name = NULL;

- kdb_register_repeat("md", kdb_md, "<vaddr>", + kdb_register_flags("md", kdb_md, "<vaddr>", "Display Memory Contents, also mdWcN, e.g. md8c1", 1, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdr", kdb_md, "<vaddr> <bytes>", + kdb_register_flags("mdr", kdb_md, "<vaddr> <bytes>", "Display Raw Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdp", kdb_md, "<paddr> <bytes>", + kdb_register_flags("mdp", kdb_md, "<paddr> <bytes>", "Display Physical Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mds", kdb_md, "<vaddr>", + kdb_register_flags("mds", kdb_md, "<vaddr>", "Display Memory Symbolically", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mm", kdb_mm, "<vaddr> <contents>", + kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("go", kdb_go, "[<vaddr>]", + kdb_register_flags("go", kdb_go, "[<vaddr>]", "Continue Execution", 1, KDB_REPEAT_NONE); - kdb_register_repeat("rd", kdb_rd, "", + kdb_register_flags("rd", kdb_rd, "", "Display Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("rm", kdb_rm, "<reg> <contents>", + kdb_register_flags("rm", kdb_rm, "<reg> <contents>", "Modify Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ef", kdb_ef, "<vaddr>", + kdb_register_flags("ef", kdb_ef, "<vaddr>", "Display exception frame", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bt", kdb_bt, "[<vaddr>]", + kdb_register_flags("bt", kdb_bt, "[<vaddr>]", "Stack traceback", 1, KDB_REPEAT_NONE); - kdb_register_repeat("btp", kdb_bt, "<pid>", + kdb_register_flags("btp", kdb_bt, "<pid>", "Display stack for process <pid>", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", + kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btc", kdb_bt, "", + kdb_register_flags("btc", kdb_bt, "", "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btt", kdb_bt, "<vaddr>", + kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, KDB_REPEAT_NONE); - kdb_register_repeat("env", kdb_env, "", + kdb_register_flags("env", kdb_env, "", "Show environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("set", kdb_set, "", + kdb_register_flags("set", kdb_set, "", "Set environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("help", kdb_help, "", + kdb_register_flags("help", kdb_help, "", "Display Help Message", 1, KDB_REPEAT_NONE); - kdb_register_repeat("?", kdb_help, "", + kdb_register_flags("?", kdb_help, "", "Display Help Message", 0, KDB_REPEAT_NONE); - kdb_register_repeat("cpu", kdb_cpu, "<cpunum>", + kdb_register_flags("cpu", kdb_cpu, "<cpunum>", "Switch to new cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kgdb", kdb_kgdb, "", + kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ps", kdb_ps, "[<flags>|A]", + kdb_register_flags("ps", kdb_ps, "[<flags>|A]", "Display active task list", 0, KDB_REPEAT_NONE); - kdb_register_repeat("pid", kdb_pid, "<pidnum>", + kdb_register_flags("pid", kdb_pid, "<pidnum>", "Switch to another task", 0, KDB_REPEAT_NONE); - kdb_register_repeat("reboot", kdb_reboot, "", + kdb_register_flags("reboot", kdb_reboot, "", "Reboot the machine immediately", 0, KDB_REPEAT_NONE); #if defined(CONFIG_MODULES) - kdb_register_repeat("lsmod", kdb_lsmod, "", + kdb_register_flags("lsmod", kdb_lsmod, "", "List loaded kernel modules", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_MAGIC_SYSRQ) - kdb_register_repeat("sr", kdb_sr, "<key>", + kdb_register_flags("sr", kdb_sr, "<key>", "Magic SysRq key", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_PRINTK) - kdb_register_repeat("dmesg", kdb_dmesg, "[lines]", + kdb_register_flags("dmesg", kdb_dmesg, "[lines]", "Display syslog buffer", 0, KDB_REPEAT_NONE); #endif if (arch_kgdb_ops.enable_nmi) { - kdb_register_repeat("disable_nmi", kdb_disable_nmi, "", + kdb_register_flags("disable_nmi", kdb_disable_nmi, "", "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); } - kdb_register_repeat("defcmd", kdb_defcmd, "name "usage" "help"", + kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kill", kdb_kill, "<-signal> <pid>", + kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", "Send a signal to a process", 0, KDB_REPEAT_NONE); - kdb_register_repeat("summary", kdb_summary, "", + kdb_register_flags("summary", kdb_summary, "", "Summarize the system", 4, KDB_REPEAT_NONE); - kdb_register_repeat("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", + kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", "Display per_cpu variables", 3, KDB_REPEAT_NONE); - kdb_register_repeat("grephelp", kdb_grep_help, "", + kdb_register_flags("grephelp", kdb_grep_help, "", "Display help on | grep", 0, KDB_REPEAT_NONE); }

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index bd90e1b..1e3b36c 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -127,7 +127,7 @@ static int kdb_ftdump(int argc, const char **argv)

static __init int kdb_ftrace_register(void) { - kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", + kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", "Dump ftrace log", 0, KDB_REPEAT_NONE); return 0; }

-- 1.9.3

Reply

Daniel Thompson

11:33 a.m.

New subject: [RESEND PATCH v5 3.16-rc4 5/8] kdb: Remove KDB_REPEAT_NONE flag

From: Anton Vorontsov anton.vorontsov@linaro.org

Since we now treat KDB_REPEAT_* as flags, there is no need to pass KDB_REPEAT_NONE. It's just the default behaviour when no flags are specified.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Ingo Molnar mingo@redhat.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 1 - kernel/debug/kdb/kdb_bp.c | 6 ++--- kernel/debug/kdb/kdb_main.c | 59 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 33 insertions(+), 35 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 90aed7c..39b44b3 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -14,7 +14,6 @@ */

typedef enum { - KDB_REPEAT_NONE = 0, /* Do not repeat this command */ KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ } kdb_cmdflags_t; diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 7be2c5d..87343f0 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -539,11 +539,11 @@ void __init kdb_initbptab(void) kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("bc", kdb_bc, "<bpnum>", - "Clear Breakpoint", 0, KDB_REPEAT_NONE); + "Clear Breakpoint", 0, 0); kdb_register_flags("be", kdb_bc, "<bpnum>", - "Enable Breakpoint", 0, KDB_REPEAT_NONE); + "Enable Breakpoint", 0, 0); kdb_register_flags("bd", kdb_bc, "<bpnum>", - "Disable Breakpoint", 0, KDB_REPEAT_NONE); + "Disable Breakpoint", 0, 0);

kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 7a0a65c..fa31ccc 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2698,7 +2698,7 @@ EXPORT_SYMBOL_GPL(kdb_register_flags); /* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_flags with KDB_REPEAT_NONE. + * kdb_register_flags with flags set to 0. * Inputs: * cmd Command name * func Function to execute the command @@ -2713,8 +2713,7 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_flags(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, 0); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2768,68 +2767,68 @@ static void __init kdb_inittab(void) kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[<vaddr>]", - "Continue Execution", 1, KDB_REPEAT_NONE); + "Continue Execution", 1, 0); kdb_register_flags("rd", kdb_rd, "", - "Display Registers", 0, KDB_REPEAT_NONE); + "Display Registers", 0, 0); kdb_register_flags("rm", kdb_rm, "<reg> <contents>", - "Modify Registers", 0, KDB_REPEAT_NONE); + "Modify Registers", 0, 0); kdb_register_flags("ef", kdb_ef, "<vaddr>", - "Display exception frame", 0, KDB_REPEAT_NONE); + "Display exception frame", 0, 0); kdb_register_flags("bt", kdb_bt, "[<vaddr>]", - "Stack traceback", 1, KDB_REPEAT_NONE); + "Stack traceback", 1, 0); kdb_register_flags("btp", kdb_bt, "<pid>", - "Display stack for process <pid>", 0, KDB_REPEAT_NONE); + "Display stack for process <pid>", 0, 0); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); + "Backtrace all processes matching state flag", 0, 0); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); + "Backtrace current process on each cpu", 0, 0); kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, - KDB_REPEAT_NONE); + 0); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, KDB_REPEAT_NONE); + "Show environment variables", 0, 0); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, KDB_REPEAT_NONE); + "Set environment variables", 0, 0); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, KDB_REPEAT_NONE); + "Display Help Message", 1, 0); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, KDB_REPEAT_NONE); + "Display Help Message", 0, 0); kdb_register_flags("cpu", kdb_cpu, "<cpunum>", - "Switch to new cpu", 0, KDB_REPEAT_NONE); + "Switch to new cpu", 0, 0); kdb_register_flags("kgdb", kdb_kgdb, "", - "Enter kgdb mode", 0, KDB_REPEAT_NONE); + "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[<flags>|A]", - "Display active task list", 0, KDB_REPEAT_NONE); + "Display active task list", 0, 0); kdb_register_flags("pid", kdb_pid, "<pidnum>", - "Switch to another task", 0, KDB_REPEAT_NONE); + "Switch to another task", 0, 0); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, KDB_REPEAT_NONE); + "Reboot the machine immediately", 0, 0); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, KDB_REPEAT_NONE); + "List loaded kernel modules", 0, 0); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "<key>", - "Magic SysRq key", 0, KDB_REPEAT_NONE); + "Magic SysRq key", 0, 0); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, KDB_REPEAT_NONE); + "Display syslog buffer", 0, 0); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); + "Disable NMI entry to KDB", 0, 0); } kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", - "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); + "Define a set of commands, down to endefcmd", 0, 0); kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", - "Send a signal to a process", 0, KDB_REPEAT_NONE); + "Send a signal to a process", 0, 0); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, KDB_REPEAT_NONE); + "Summarize the system", 4, 0); kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", - "Display per_cpu variables", 3, KDB_REPEAT_NONE); + "Display per_cpu variables", 3, 0); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, KDB_REPEAT_NONE); + "Display help on | grep", 0, 0); }

/* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 1e3b36c..3da7e30 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, KDB_REPEAT_NONE); + "Dump ftrace log", 0, 0); return 0; }

-- 1.9.3

Reply

Daniel Thompson

11:33 a.m.

New subject: [RESEND PATCH v5 3.16-rc4 7/8] kdb: Add enable mask for groups of commands

From: Anton Vorontsov anton.vorontsov@linaro.org

Currently all kdb commands are enabled whenever kdb is deployed. This makes it difficult to deploy kdb to help debug certain types of systems.

Android phones provide one example; the FIQ debugger found on some Android devices has a deliberately weak set of commands to allow the debugger to enabled very late in the production cycle.

Certain kiosk environments offer another interesting case where an engineer might wish to probe the system state using passive inspection commands without providing sufficient power for a passer by to root it.

Without any restrictions, obtaining the root rights via KDB is a matter of a few commands, and works everywhere. For example, log in as a normal user:

cbou:~$ id uid=1001(cbou) gid=1001(cbou) groups=1001(cbou)

Now enter KDB (for example via sysrq):

Entering kdb (current=0xffff8800065bc740, pid 920) due to Keyboard Entry kdb> ps 23 sleeping system daemon (state M) processes suppressed, use 'ps A' to see all. Task Addr Pid Parent [*] cpu State Thread Command 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

0xffff880007078000 1 0 0 0 S 0xffff8800070782e0 init [...snip...] 0xffff8800065be3c0 918 1 0 0 S 0xffff8800065be6a0 getty 0xffff8800065b9c80 919 1 0 0 S 0xffff8800065b9f60 login 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

All we need is the offset of cred pointers. We can look up the offset in the distro's kernel source, but it is unnecessary. We can just start dumping init's task_struct, until we see the process name:

kdb> md 0xffff880007078000 0xffff880007078000 0000000000000001 ffff88000703c000 ................ 0xffff880007078010 0040210000000002 0000000000000000 .....!@......... [...snip...] 0xffff8800070782b0 ffff8800073e0580 ffff8800073e0580 ..>.......>..... 0xffff8800070782c0 0000000074696e69 0000000000000000 init............

^ Here, 'init'. Creds are just above it, so the offset is 0x02b0.

Now we set up init's creds for our non-privileged shell:

kdb> mm 0xffff8800065bc740+0x02b0 0xffff8800073e0580 0xffff8800065bc9f0 = 0xffff8800073e0580 kdb> mm 0xffff8800065bc740+0x02b8 0xffff8800073e0580 0xffff8800065bc9f8 = 0xffff8800073e0580

And thus gaining the root:

kdb> go cbou:~$ id uid=0(root) gid=0(root) groups=0(root) cbou:~$ bash root:~#

p.s. No distro enables kdb by default (although, with a nice KDB-over-KMS feature availability, I would expect at least some would enable it), so it's not actually some kind of a major issue.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 1 + kernel/debug/kdb/kdb_main.c | 30 +++++++++++++++++++++++++++++- 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index f1fe361..75ae2e2 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -105,6 +105,7 @@ extern atomic_t kdb_event; #define KDB_BADLENGTH (-19) #define KDB_NOBP (-20) #define KDB_BADADDR (-21) +#define KDB_NOPERM (-22)

/* * kdb_diemsg diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 941ff97..c670fe4 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -12,6 +12,7 @@ */

#include <linux/ctype.h> +#include <linux/types.h> #include <linux/string.h> #include <linux/kernel.h> #include <linux/kmsg_dump.h> @@ -23,6 +24,7 @@ #include <linux/vmalloc.h> #include <linux/atomic.h> #include <linux/module.h> +#include <linux/moduleparam.h> #include <linux/mm.h> #include <linux/init.h> #include <linux/kallsyms.h> @@ -42,6 +44,12 @@ #include <linux/slab.h> #include "kdb_private.h"

+#undef MODULE_PARAM_PREFIX +#define MODULE_PARAM_PREFIX "kdb." + +static int kdb_cmd_enabled; +module_param_named(cmd_enable, kdb_cmd_enabled, int, 0600); + #define GREP_LEN 256 char kdb_grep_string[GREP_LEN]; int kdb_grepping_flag; @@ -121,6 +129,7 @@ static kdbmsg_t kdbmsgs[] = { KDBMSG(BADLENGTH, "Invalid length field"), KDBMSG(NOBP, "No Breakpoint exists"), KDBMSG(BADADDR, "Invalid address"), + KDBMSG(NOPERM, "Permission denied"), }; #undef KDBMSG

@@ -496,6 +505,15 @@ int kdbgetaddrarg(int argc, const char **argv, int *nextarg, kdb_symtab_t symtab;

/* + * If the enable flags prohibit both arbitrary memory access + * and flow control then there are no reasonable grounds to + * provide symbol lookup. + */ + if (!kdb_check_flags(KDB_ENABLE_MEM_READ | KDB_ENABLE_FLOW_CTRL, + kdb_cmd_enabled, false)) + return KDB_NOPERM; + + /* * Process arguments which follow the following syntax: * * symbol | numeric-address [+/- numeric-offset] @@ -1028,6 +1046,10 @@ int kdb_parse(const char *cmdstr)

if (i < kdb_max_commands) { int result; + + if (!kdb_check_flags(tp->cmd_flags, kdb_cmd_enabled, argc <= 1)) + return KDB_NOPERM; + KDB_STATE_SET(CMD); result = (*tp->cmd_func)(argc-1, (const char **)argv); if (result && ignore_errors && result > KDB_CMD_GO) @@ -1939,10 +1961,14 @@ static int kdb_rm(int argc, const char **argv) */ static int kdb_sr(int argc, const char **argv) { + bool check_mask = + !kdb_check_flags(KDB_ENABLE_ALL, kdb_cmd_enabled, false); + if (argc != 1) return KDB_ARGCOUNT; + kdb_trap_printk++; - __handle_sysrq(*argv[1], false); + __handle_sysrq(*argv[1], check_mask); kdb_trap_printk--;

return 0; @@ -2393,6 +2419,8 @@ static int kdb_help(int argc, const char **argv) return 0; if (!kt->cmd_name) continue; + if (!kdb_check_flags(kt->cmd_flags, kdb_cmd_enabled, true)) + continue; if (strlen(kt->cmd_usage) > 20) space = "\n "; kdb_printf("%-15.15s %-20s%s%s\n", kt->cmd_name,

-- 1.9.3

Reply

Jason Wessel

1:16 p.m.

New subject: [RESEND PATCH v5 3.16-rc4 0/8] kdb: Allow selective reduction in capabilities

On 07/11/2014 06:33 AM, Daniel Thompson wrote:

...

This patchset implements restricted modes for the KDB debugger. It is a continuation of previous work of Anton Vorontsov. There are no outstanding review comments for this patchset.

It provides a means for the root user to choose the set of kdb commands that are available on the kdb console. It is implemented similarly to the existing code to mask the available magic SysRq commands with modes for disable-all (0), enable-all(1) and a bitmask to enable/disable groups of functionality.

The implementation of the mask check includes a feature to allow a command to change which group it belongs to based on whether or not the command has arguments (for example, go without arguments is a very safe command whilst go with an argument allows arbitrary changes to the program counter).

There are a few patches, some are just cleanups, some are churn-ish cleanups, but inevitable. And the rest implements the mode -- after all the preparations, everything is pretty straightforward.

I plan to take one more walk through the code and aim to get this merged for the upcoming merge window. :-)

Cheers, Jason.

Reply

Daniel Thompson

2:01 p.m.

New subject: [RESEND PATCH v5 3.17-rc1 1/8] kdb: Remove currently unused kdbtab_t->cmd_flags

From: Anton Vorontsov anton.vorontsov@linaro.org

The struct member is never used in the code, so we can remove it.

We will introduce real flags soon by renaming cmd_repeat to cmd_flags.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@liaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Ingo Molnar mingo@kernel.org Cc: kgdb-bugreport@lists.sourceforge.net --- kernel/debug/kdb/kdb_main.c | 1 - kernel/debug/kdb/kdb_private.h | 1 - 2 files changed, 2 deletions(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 379650b..cc02aa2 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2694,7 +2694,6 @@ int kdb_register_repeat(char *cmd, kp->cmd_func = func; kp->cmd_usage = usage; kp->cmd_help = help; - kp->cmd_flags = 0; kp->cmd_minlen = minlen; kp->cmd_repeat = repeat;

diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index 7afd3c8..c4c46c7 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -172,7 +172,6 @@ typedef struct _kdbtab { kdb_func_t cmd_func; /* Function to execute command */ char *cmd_usage; /* Usage String for this command */ char *cmd_help; /* Help message for this command */ - short cmd_flags; /* Parsing flags */ short cmd_minlen; /* Minimum legal # command * chars required */ kdb_repeat_t cmd_repeat; /* Does command auto repeat on enter? */

-- 1.9.3

Reply

Daniel Thompson

2:01 p.m.

New subject: [RESEND PATCH v5 3.17-rc1 3/8] kdb: Rename kdb_register_repeat() to kdb_register_flags()

From: Anton Vorontsov anton.vorontsov@linaro.org

We're about to add more options for commands behaviour, so let's give a more generic name to the low-level kdb command registration function.

There are just various renames, no functional changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Ingo Molnar mingo@redhat.com Cc: Mike Travis travis@sgi.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 10 +++--- kernel/debug/kdb/kdb_bp.c | 14 ++++---- kernel/debug/kdb/kdb_main.c | 86 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 56 insertions(+), 56 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index e650f79..32d2f40 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -146,17 +146,17 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos)

/* Dynamic kdb shell command registration */ extern int kdb_register(char *, kdb_func_t, char *, char *, short); -extern int kdb_register_repeat(char *, kdb_func_t, char *, char *, - short, kdb_cmdflags_t); +extern int kdb_register_flags(char *, kdb_func_t, char *, char *, + short, kdb_cmdflags_t); extern int kdb_unregister(char *); #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } static inline void kdb_init(int level) {} static inline int kdb_register(char *cmd, kdb_func_t func, char *usage, char *help, short minlen) { return 0; } -static inline int kdb_register_repeat(char *cmd, kdb_func_t func, char *usage, - char *help, short minlen, - kdb_cmdflags_t flags) { return 0; } +static inline int kdb_register_flags(char *cmd, kdb_func_t func, char *usage, + char *help, short minlen, + kdb_cmdflags_t flags) { return 0; } static inline int kdb_unregister(char *cmd) { return 0; } #endif /* CONFIG_KGDB_KDB */ enum { diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 70a5046..7be2c5d 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -531,21 +531,21 @@ void __init kdb_initbptab(void) for (i = 0, bp = kdb_breakpoints; i < KDB_MAXBPT; i++, bp++) bp->bp_free = 1;

- kdb_register_repeat("bp", kdb_bp, "[<vaddr>]", + kdb_register_flags("bp", kdb_bp, "[<vaddr>]", "Set/Display breakpoints", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bl", kdb_bp, "[<vaddr>]", + kdb_register_flags("bl", kdb_bp, "[<vaddr>]", "Display breakpoints", 0, KDB_REPEAT_NO_ARGS); if (arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT) - kdb_register_repeat("bph", kdb_bp, "[<vaddr>]", + kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("bc", kdb_bc, "<bpnum>", + kdb_register_flags("bc", kdb_bc, "<bpnum>", "Clear Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("be", kdb_bc, "<bpnum>", + kdb_register_flags("be", kdb_bc, "<bpnum>", "Enable Breakpoint", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bd", kdb_bc, "<bpnum>", + kdb_register_flags("bd", kdb_bc, "<bpnum>", "Disable Breakpoint", 0, KDB_REPEAT_NONE);

- kdb_register_repeat("ss", kdb_ss, "", + kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); /* * Architecture dependent initialization. diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 41966b5..070f1ff 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2629,7 +2629,7 @@ static int kdb_grep_help(int argc, const char **argv) }

/* - * kdb_register_repeat - This function is used to register a kernel + * kdb_register_flags - This function is used to register a kernel * debugger command. * Inputs: * cmd Command name @@ -2641,12 +2641,12 @@ static int kdb_grep_help(int argc, const char **argv) * zero for success, one if a duplicate command. */ #define kdb_command_extend 50 /* arbitrary */ -int kdb_register_repeat(char *cmd, - kdb_func_t func, - char *usage, - char *help, - short minlen, - kdb_cmdflags_t flags) +int kdb_register_flags(char *cmd, + kdb_func_t func, + char *usage, + char *help, + short minlen, + kdb_cmdflags_t flags) { int i; kdbtab_t *kp; @@ -2699,13 +2699,13 @@ int kdb_register_repeat(char *cmd,

return 0; } -EXPORT_SYMBOL_GPL(kdb_register_repeat); +EXPORT_SYMBOL_GPL(kdb_register_flags);

/* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_repeat with KDB_REPEAT_NONE. + * kdb_register_flags with KDB_REPEAT_NONE. * Inputs: * cmd Command name * func Function to execute the command @@ -2720,8 +2720,8 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_repeat(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, + KDB_REPEAT_NONE); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2763,79 +2763,79 @@ static void __init kdb_inittab(void) for_each_kdbcmd(kp, i) kp->cmd_name = NULL;

- kdb_register_repeat("md", kdb_md, "<vaddr>", + kdb_register_flags("md", kdb_md, "<vaddr>", "Display Memory Contents, also mdWcN, e.g. md8c1", 1, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdr", kdb_md, "<vaddr> <bytes>", + kdb_register_flags("mdr", kdb_md, "<vaddr> <bytes>", "Display Raw Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mdp", kdb_md, "<paddr> <bytes>", + kdb_register_flags("mdp", kdb_md, "<paddr> <bytes>", "Display Physical Memory", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mds", kdb_md, "<vaddr>", + kdb_register_flags("mds", kdb_md, "<vaddr>", "Display Memory Symbolically", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("mm", kdb_mm, "<vaddr> <contents>", + kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); - kdb_register_repeat("go", kdb_go, "[<vaddr>]", + kdb_register_flags("go", kdb_go, "[<vaddr>]", "Continue Execution", 1, KDB_REPEAT_NONE); - kdb_register_repeat("rd", kdb_rd, "", + kdb_register_flags("rd", kdb_rd, "", "Display Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("rm", kdb_rm, "<reg> <contents>", + kdb_register_flags("rm", kdb_rm, "<reg> <contents>", "Modify Registers", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ef", kdb_ef, "<vaddr>", + kdb_register_flags("ef", kdb_ef, "<vaddr>", "Display exception frame", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bt", kdb_bt, "[<vaddr>]", + kdb_register_flags("bt", kdb_bt, "[<vaddr>]", "Stack traceback", 1, KDB_REPEAT_NONE); - kdb_register_repeat("btp", kdb_bt, "<pid>", + kdb_register_flags("btp", kdb_bt, "<pid>", "Display stack for process <pid>", 0, KDB_REPEAT_NONE); - kdb_register_repeat("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", + kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btc", kdb_bt, "", + kdb_register_flags("btc", kdb_bt, "", "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("btt", kdb_bt, "<vaddr>", + kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, KDB_REPEAT_NONE); - kdb_register_repeat("env", kdb_env, "", + kdb_register_flags("env", kdb_env, "", "Show environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("set", kdb_set, "", + kdb_register_flags("set", kdb_set, "", "Set environment variables", 0, KDB_REPEAT_NONE); - kdb_register_repeat("help", kdb_help, "", + kdb_register_flags("help", kdb_help, "", "Display Help Message", 1, KDB_REPEAT_NONE); - kdb_register_repeat("?", kdb_help, "", + kdb_register_flags("?", kdb_help, "", "Display Help Message", 0, KDB_REPEAT_NONE); - kdb_register_repeat("cpu", kdb_cpu, "<cpunum>", + kdb_register_flags("cpu", kdb_cpu, "<cpunum>", "Switch to new cpu", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kgdb", kdb_kgdb, "", + kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, KDB_REPEAT_NONE); - kdb_register_repeat("ps", kdb_ps, "[<flags>|A]", + kdb_register_flags("ps", kdb_ps, "[<flags>|A]", "Display active task list", 0, KDB_REPEAT_NONE); - kdb_register_repeat("pid", kdb_pid, "<pidnum>", + kdb_register_flags("pid", kdb_pid, "<pidnum>", "Switch to another task", 0, KDB_REPEAT_NONE); - kdb_register_repeat("reboot", kdb_reboot, "", + kdb_register_flags("reboot", kdb_reboot, "", "Reboot the machine immediately", 0, KDB_REPEAT_NONE); #if defined(CONFIG_MODULES) - kdb_register_repeat("lsmod", kdb_lsmod, "", + kdb_register_flags("lsmod", kdb_lsmod, "", "List loaded kernel modules", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_MAGIC_SYSRQ) - kdb_register_repeat("sr", kdb_sr, "<key>", + kdb_register_flags("sr", kdb_sr, "<key>", "Magic SysRq key", 0, KDB_REPEAT_NONE); #endif #if defined(CONFIG_PRINTK) - kdb_register_repeat("dmesg", kdb_dmesg, "[lines]", + kdb_register_flags("dmesg", kdb_dmesg, "[lines]", "Display syslog buffer", 0, KDB_REPEAT_NONE); #endif if (arch_kgdb_ops.enable_nmi) { - kdb_register_repeat("disable_nmi", kdb_disable_nmi, "", + kdb_register_flags("disable_nmi", kdb_disable_nmi, "", "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); } - kdb_register_repeat("defcmd", kdb_defcmd, "name "usage" "help"", + kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); - kdb_register_repeat("kill", kdb_kill, "<-signal> <pid>", + kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", "Send a signal to a process", 0, KDB_REPEAT_NONE); - kdb_register_repeat("summary", kdb_summary, "", + kdb_register_flags("summary", kdb_summary, "", "Summarize the system", 4, KDB_REPEAT_NONE); - kdb_register_repeat("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", + kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", "Display per_cpu variables", 3, KDB_REPEAT_NONE); - kdb_register_repeat("grephelp", kdb_grep_help, "", + kdb_register_flags("grephelp", kdb_grep_help, "", "Display help on | grep", 0, KDB_REPEAT_NONE); }

diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index bd90e1b..1e3b36c 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -127,7 +127,7 @@ static int kdb_ftdump(int argc, const char **argv)

static __init int kdb_ftrace_register(void) { - kdb_register_repeat("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", + kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", "Dump ftrace log", 0, KDB_REPEAT_NONE); return 0; }

-- 1.9.3

Reply

Daniel Thompson

2:01 p.m.

New subject: [RESEND PATCH v5 3.17-rc1 5/8] kdb: Remove KDB_REPEAT_NONE flag

From: Anton Vorontsov anton.vorontsov@linaro.org

Since we now treat KDB_REPEAT_* as flags, there is no need to pass KDB_REPEAT_NONE. It's just the default behaviour when no flags are specified.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Steven Rostedt rostedt@goodmis.org Cc: Ingo Molnar mingo@redhat.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 1 - kernel/debug/kdb/kdb_bp.c | 6 ++--- kernel/debug/kdb/kdb_main.c | 59 ++++++++++++++++++++++----------------------- kernel/trace/trace_kdb.c | 2 +- 4 files changed, 33 insertions(+), 35 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 90aed7c..39b44b3 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -14,7 +14,6 @@ */

typedef enum { - KDB_REPEAT_NONE = 0, /* Do not repeat this command */ KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ } kdb_cmdflags_t; diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index 7be2c5d..87343f0 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -539,11 +539,11 @@ void __init kdb_initbptab(void) kdb_register_flags("bph", kdb_bp, "[<vaddr>]", "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("bc", kdb_bc, "<bpnum>", - "Clear Breakpoint", 0, KDB_REPEAT_NONE); + "Clear Breakpoint", 0, 0); kdb_register_flags("be", kdb_bc, "<bpnum>", - "Enable Breakpoint", 0, KDB_REPEAT_NONE); + "Enable Breakpoint", 0, 0); kdb_register_flags("bd", kdb_bc, "<bpnum>", - "Disable Breakpoint", 0, KDB_REPEAT_NONE); + "Disable Breakpoint", 0, 0);

kdb_register_flags("ss", kdb_ss, "", "Single Step", 1, KDB_REPEAT_NO_ARGS); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index cbacae2..538bf1d 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -2698,7 +2698,7 @@ EXPORT_SYMBOL_GPL(kdb_register_flags); /* * kdb_register - Compatibility register function for commands that do * not need to specify a repeat state. Equivalent to - * kdb_register_flags with KDB_REPEAT_NONE. + * kdb_register_flags with flags set to 0. * Inputs: * cmd Command name * func Function to execute the command @@ -2713,8 +2713,7 @@ int kdb_register(char *cmd, char *help, short minlen) { - return kdb_register_flags(cmd, func, usage, help, minlen, - KDB_REPEAT_NONE); + return kdb_register_flags(cmd, func, usage, help, minlen, 0); } EXPORT_SYMBOL_GPL(kdb_register);

@@ -2768,68 +2767,68 @@ static void __init kdb_inittab(void) kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[<vaddr>]", - "Continue Execution", 1, KDB_REPEAT_NONE); + "Continue Execution", 1, 0); kdb_register_flags("rd", kdb_rd, "", - "Display Registers", 0, KDB_REPEAT_NONE); + "Display Registers", 0, 0); kdb_register_flags("rm", kdb_rm, "<reg> <contents>", - "Modify Registers", 0, KDB_REPEAT_NONE); + "Modify Registers", 0, 0); kdb_register_flags("ef", kdb_ef, "<vaddr>", - "Display exception frame", 0, KDB_REPEAT_NONE); + "Display exception frame", 0, 0); kdb_register_flags("bt", kdb_bt, "[<vaddr>]", - "Stack traceback", 1, KDB_REPEAT_NONE); + "Stack traceback", 1, 0); kdb_register_flags("btp", kdb_bt, "<pid>", - "Display stack for process <pid>", 0, KDB_REPEAT_NONE); + "Display stack for process <pid>", 0, 0); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, KDB_REPEAT_NONE); + "Backtrace all processes matching state flag", 0, 0); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, KDB_REPEAT_NONE); + "Backtrace current process on each cpu", 0, 0); kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, - KDB_REPEAT_NONE); + 0); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, KDB_REPEAT_NONE); + "Show environment variables", 0, 0); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, KDB_REPEAT_NONE); + "Set environment variables", 0, 0); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, KDB_REPEAT_NONE); + "Display Help Message", 1, 0); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, KDB_REPEAT_NONE); + "Display Help Message", 0, 0); kdb_register_flags("cpu", kdb_cpu, "<cpunum>", - "Switch to new cpu", 0, KDB_REPEAT_NONE); + "Switch to new cpu", 0, 0); kdb_register_flags("kgdb", kdb_kgdb, "", - "Enter kgdb mode", 0, KDB_REPEAT_NONE); + "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[<flags>|A]", - "Display active task list", 0, KDB_REPEAT_NONE); + "Display active task list", 0, 0); kdb_register_flags("pid", kdb_pid, "<pidnum>", - "Switch to another task", 0, KDB_REPEAT_NONE); + "Switch to another task", 0, 0); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, KDB_REPEAT_NONE); + "Reboot the machine immediately", 0, 0); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, KDB_REPEAT_NONE); + "List loaded kernel modules", 0, 0); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "<key>", - "Magic SysRq key", 0, KDB_REPEAT_NONE); + "Magic SysRq key", 0, 0); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, KDB_REPEAT_NONE); + "Display syslog buffer", 0, 0); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, KDB_REPEAT_NONE); + "Disable NMI entry to KDB", 0, 0); } kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", - "Define a set of commands, down to endefcmd", 0, KDB_REPEAT_NONE); + "Define a set of commands, down to endefcmd", 0, 0); kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", - "Send a signal to a process", 0, KDB_REPEAT_NONE); + "Send a signal to a process", 0, 0); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, KDB_REPEAT_NONE); + "Summarize the system", 4, 0); kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", - "Display per_cpu variables", 3, KDB_REPEAT_NONE); + "Display per_cpu variables", 3, 0); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, KDB_REPEAT_NONE); + "Display help on | grep", 0, 0); }

/* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 1e3b36c..3da7e30 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -128,7 +128,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, KDB_REPEAT_NONE); + "Dump ftrace log", 0, 0); return 0; }

-- 1.9.3

Reply

Daniel Thompson

2:02 p.m.

New subject: [RESEND PATCH v5 3.17-rc1 7/8] kdb: Add enable mask for groups of commands

From: Anton Vorontsov anton.vorontsov@linaro.org

Currently all kdb commands are enabled whenever kdb is deployed. This makes it difficult to deploy kdb to help debug certain types of systems.

Android phones provide one example; the FIQ debugger found on some Android devices has a deliberately weak set of commands to allow the debugger to enabled very late in the production cycle.

Certain kiosk environments offer another interesting case where an engineer might wish to probe the system state using passive inspection commands without providing sufficient power for a passer by to root it.

Without any restrictions, obtaining the root rights via KDB is a matter of a few commands, and works everywhere. For example, log in as a normal user:

cbou:~$ id uid=1001(cbou) gid=1001(cbou) groups=1001(cbou)

Now enter KDB (for example via sysrq):

Entering kdb (current=0xffff8800065bc740, pid 920) due to Keyboard Entry kdb> ps 23 sleeping system daemon (state M) processes suppressed, use 'ps A' to see all. Task Addr Pid Parent [*] cpu State Thread Command 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

0xffff880007078000 1 0 0 0 S 0xffff8800070782e0 init [...snip...] 0xffff8800065be3c0 918 1 0 0 S 0xffff8800065be6a0 getty 0xffff8800065b9c80 919 1 0 0 S 0xffff8800065b9f60 login 0xffff8800065bc740 920 919 1 0 R 0xffff8800065bca20 *bash

All we need is the offset of cred pointers. We can look up the offset in the distro's kernel source, but it is unnecessary. We can just start dumping init's task_struct, until we see the process name:

kdb> md 0xffff880007078000 0xffff880007078000 0000000000000001 ffff88000703c000 ................ 0xffff880007078010 0040210000000002 0000000000000000 .....!@......... [...snip...] 0xffff8800070782b0 ffff8800073e0580 ffff8800073e0580 ..>.......>..... 0xffff8800070782c0 0000000074696e69 0000000000000000 init............

^ Here, 'init'. Creds are just above it, so the offset is 0x02b0.

Now we set up init's creds for our non-privileged shell:

kdb> mm 0xffff8800065bc740+0x02b0 0xffff8800073e0580 0xffff8800065bc9f0 = 0xffff8800073e0580 kdb> mm 0xffff8800065bc740+0x02b8 0xffff8800073e0580 0xffff8800065bc9f8 = 0xffff8800073e0580

And thus gaining the root:

kdb> go cbou:~$ id uid=0(root) gid=0(root) groups=0(root) cbou:~$ bash root:~#

p.s. No distro enables kdb by default (although, with a nice KDB-over-KMS feature availability, I would expect at least some would enable it), so it's not actually some kind of a major issue.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: kgdb-bugreport@lists.sourceforge.net --- include/linux/kdb.h | 1 + kernel/debug/kdb/kdb_main.c | 30 +++++++++++++++++++++++++++++- 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index f1fe361..75ae2e2 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -105,6 +105,7 @@ extern atomic_t kdb_event; #define KDB_BADLENGTH (-19) #define KDB_NOBP (-20) #define KDB_BADADDR (-21) +#define KDB_NOPERM (-22)

/* * kdb_diemsg diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index fae1fc3..fe1ac56 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -12,6 +12,7 @@ */

#include <linux/ctype.h> +#include <linux/types.h> #include <linux/string.h> #include <linux/kernel.h> #include <linux/kmsg_dump.h> @@ -23,6 +24,7 @@ #include <linux/vmalloc.h> #include <linux/atomic.h> #include <linux/module.h> +#include <linux/moduleparam.h> #include <linux/mm.h> #include <linux/init.h> #include <linux/kallsyms.h> @@ -42,6 +44,12 @@ #include <linux/slab.h> #include "kdb_private.h"

+#undef MODULE_PARAM_PREFIX +#define MODULE_PARAM_PREFIX "kdb." + +static int kdb_cmd_enabled; +module_param_named(cmd_enable, kdb_cmd_enabled, int, 0600); + #define GREP_LEN 256 char kdb_grep_string[GREP_LEN]; int kdb_grepping_flag; @@ -121,6 +129,7 @@ static kdbmsg_t kdbmsgs[] = { KDBMSG(BADLENGTH, "Invalid length field"), KDBMSG(NOBP, "No Breakpoint exists"), KDBMSG(BADADDR, "Invalid address"), + KDBMSG(NOPERM, "Permission denied"), }; #undef KDBMSG

@@ -496,6 +505,15 @@ int kdbgetaddrarg(int argc, const char **argv, int *nextarg, kdb_symtab_t symtab;

/* + * If the enable flags prohibit both arbitrary memory access + * and flow control then there are no reasonable grounds to + * provide symbol lookup. + */ + if (!kdb_check_flags(KDB_ENABLE_MEM_READ | KDB_ENABLE_FLOW_CTRL, + kdb_cmd_enabled, false)) + return KDB_NOPERM; + + /* * Process arguments which follow the following syntax: * * symbol | numeric-address [+/- numeric-offset] @@ -1028,6 +1046,10 @@ int kdb_parse(const char *cmdstr)

if (i < kdb_max_commands) { int result; + + if (!kdb_check_flags(tp->cmd_flags, kdb_cmd_enabled, argc <= 1)) + return KDB_NOPERM; + KDB_STATE_SET(CMD); result = (*tp->cmd_func)(argc-1, (const char **)argv); if (result && ignore_errors && result > KDB_CMD_GO) @@ -1939,10 +1961,14 @@ static int kdb_rm(int argc, const char **argv) */ static int kdb_sr(int argc, const char **argv) { + bool check_mask = + !kdb_check_flags(KDB_ENABLE_ALL, kdb_cmd_enabled, false); + if (argc != 1) return KDB_ARGCOUNT; + kdb_trap_printk++; - __handle_sysrq(*argv[1], false); + __handle_sysrq(*argv[1], check_mask); kdb_trap_printk--;

return 0; @@ -2393,6 +2419,8 @@ static int kdb_help(int argc, const char **argv) return 0; if (!kt->cmd_name) continue; + if (!kdb_check_flags(kt->cmd_flags, kdb_cmd_enabled, true)) + continue; if (strlen(kt->cmd_usage) > 20) space = "\n "; kdb_printf("%-15.15s %-20s%s%s\n", kt->cmd_name,

-- 1.9.3

Reply

Daniel Thompson

7 Jan 7 Jan

4:34 p.m.

New subject: [RESEND PATCH v5 3.19-rc2 0/8] kdb: Allow selective reduction in capabilities

Jason: This patchset is already integrated into kgdb-next and I'm only really posted it for completeness. The rebase from v3.18-rc3 to v3.19-rc2 was trivial (no conflicts at all) so you can probably just stick with what you already have in kgdb-next.

This patchset implements restricted modes for the KDB debugger. These can be used to provide some diagnostic capability to a users with access to the debug console without giving unrestricted access to the system.

There are no outstanding review comments for this patchset.

Most obvious use cases are to realize a diagnostic mode to tackle in-the-field failures of systems such as mobile phones, web kiosks or embedded devices. A concrete example is the serial debugger found in some android devices which is typically multiplexed over the headphone or USB socket. Currently Android cannot use kdb for this purpose because it introduces risks to user data if the phone were connected to "evil" audio hardware.

The feature is conceptually similarly to the existing code to mask the available magic SysRq commands. For this reason it is implemented in a similar way with modes for disable-all (0), enable-all(1) and a bitmask to enable/disable groups of functionality.

The implementation of the mask check includes a feature to allow a command to change which group it belongs to based on whether or not the command has arguments (for example, go without arguments is a very safe command whilst go with an argument allows arbitrary changes to the program counter).

There are a few patches, some are just cleanups, some are churn-ish cleanups, but inevitable. And the rest implements the mode -- after all the preparations, everything is pretty straightforward.

Changes since v4: * Drop patches to avoid deadlock on sysrq spin lock (Rik van Riel's 984d74a72076... is a much better approach).

Changes since v3: * Improved commenting on safety of calls to __handle_sysrq_nolock * Remove magic shift value in the command categorization values and expressed the flags using shifts to make code review of the defined shift value easier.

Changes since v2: * Fixed stupid build error when CONFIG_KDB[_KIOSK]_DEFAULT_ENABLE was not defined. * Increase flexibility by allowing the userspace greater control over the commands to be restricted. * Removed the "kiosk" terminology. Its confusing.

Changes since v1 (circa 2012):

* ef (Display exception frame) is essentially an overly complex peek and has therefore been marked unsafe * bt (Stack traceback) has been marked safe only with no arguments * sr (Magic SysRq key) honours the sysrq mask when called in kiosk mode * Fixed over-zealous blocking of macro commands * Symbol lookup is forbidden by kdbgetaddrarg (more robust, better error reporting to user) * Fix deadlock in sr (Magic SysRq key) * Better help text in kiosk mode * Default (kiosk on/off) can be changed From the config file.

Anton Vorontsov (6): kdb: Remove currently unused kdbtab_t->cmd_flags kdb: Rename kdb_repeat_t to kdb_cmdflags_t, cmd_repeat to cmd_flags kdb: Rename kdb_register_repeat() to kdb_register_flags() kdb: Use KDB_REPEAT_* values as flags kdb: Remove KDB_REPEAT_NONE flag kdb: Add enable mask for groups of commands

Daniel Thompson (2): kdb: Categorize kdb commands (similar to SysRq categorization) kdb: Allow access to sensitive commands to be restricted by default

-- 1.9.3

Reply

Daniel Thompson

4:34 p.m.

New subject: [RESEND PATCH v5 3.19-rc2 2/8] kdb: Rename kdb_repeat_t to kdb_cmdflags_t, cmd_repeat to cmd_flags

From: Anton Vorontsov anton.vorontsov@linaro.org

We're about to add more options for command behaviour, so let's expand the meaning of kdb_repeat_t.

So far we just do various renames, there should be no functional changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com --- include/linux/kdb.h | 6 +++--- kernel/debug/kdb/kdb_main.c | 6 +++--- kernel/debug/kdb/kdb_private.h | 2 +- 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 290db1269c4c..e650f79aa414 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -17,7 +17,7 @@ typedef enum { KDB_REPEAT_NONE = 0, /* Do not repeat this command */ KDB_REPEAT_NO_ARGS, /* Repeat the command without arguments */ KDB_REPEAT_WITH_ARGS, /* Repeat the command including its arguments */ -} kdb_repeat_t; +} kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **);

@@ -147,7 +147,7 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos) /* Dynamic kdb shell command registration */ extern int kdb_register(char *, kdb_func_t, char *, char *, short); extern int kdb_register_repeat(char *, kdb_func_t, char *, char *, - short, kdb_repeat_t); + short, kdb_cmdflags_t); extern int kdb_unregister(char *); #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } @@ -156,7 +156,7 @@ static inline int kdb_register(char *cmd, kdb_func_t func, char *usage, char *help, short minlen) { return 0; } static inline int kdb_register_repeat(char *cmd, kdb_func_t func, char *usage, char *help, short minlen, - kdb_repeat_t repeat) { return 0; } + kdb_cmdflags_t flags) { return 0; } static inline int kdb_unregister(char *cmd) { return 0; } #endif /* CONFIG_KGDB_KDB */ enum { diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index cc02aa205668..41966b5f86b7 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1008,7 +1008,7 @@ int kdb_parse(const char *cmdstr) if (result && ignore_errors && result > KDB_CMD_GO) result = 0; KDB_STATE_CLEAR(CMD); - switch (tp->cmd_repeat) { + switch (tp->cmd_flags) { case KDB_REPEAT_NONE: argc = 0; if (argv[0]) @@ -2646,7 +2646,7 @@ int kdb_register_repeat(char *cmd, char *usage, char *help, short minlen, - kdb_repeat_t repeat) + kdb_cmdflags_t flags) { int i; kdbtab_t *kp; @@ -2695,7 +2695,7 @@ int kdb_register_repeat(char *cmd, kp->cmd_usage = usage; kp->cmd_help = help; kp->cmd_minlen = minlen; - kp->cmd_repeat = repeat; + kp->cmd_flags = flags;

return 0; } diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h index c4c46c7b26fd..eaacd1693954 100644 --- a/kernel/debug/kdb/kdb_private.h +++ b/kernel/debug/kdb/kdb_private.h @@ -174,7 +174,7 @@ typedef struct _kdbtab { char *cmd_help; /* Help message for this command */ short cmd_minlen; /* Minimum legal # command * chars required */ - kdb_repeat_t cmd_repeat; /* Does command auto repeat on enter? */ + kdb_cmdflags_t cmd_flags; /* Command behaviour flags */ } kdbtab_t;

extern int kdb_bt(int, const char **); /* KDB display back trace */

-- 1.9.3

Reply

Daniel Thompson

4:34 p.m.

New subject: [RESEND PATCH v5 3.19-rc2 4/8] kdb: Use KDB_REPEAT_* values as flags

From: Anton Vorontsov anton.vorontsov@linaro.org

The actual values of KDB_REPEAT_* enum values and overall logic stayed the same, but we now treat the values as flags.

This makes it possible to add other flags and combine them, plus makes the code a lot simpler and shorter. But functionality-wise, there should be no changes.

Signed-off-by: Anton Vorontsov anton.vorontsov@linaro.org Signed-off-by: John Stultz john.stultz@linaro.org Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com --- include/linux/kdb.h | 4 ++-- kernel/debug/kdb/kdb_main.c | 21 +++++++-------------- 2 files changed, 9 insertions(+), 16 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 32d2f407981d..90aed7c31f0d 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -15,8 +15,8 @@

typedef enum { KDB_REPEAT_NONE = 0, /* Do not repeat this command */ - KDB_REPEAT_NO_ARGS, /* Repeat the command without arguments */ - KDB_REPEAT_WITH_ARGS, /* Repeat the command including its arguments */ + KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ + KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ } kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **); diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 070f1ff358d2..cbacae24a55a 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -1008,20 +1008,13 @@ int kdb_parse(const char *cmdstr) if (result && ignore_errors && result > KDB_CMD_GO) result = 0; KDB_STATE_CLEAR(CMD); - switch (tp->cmd_flags) { - case KDB_REPEAT_NONE: - argc = 0; - if (argv[0]) - *(argv[0]) = '\0'; - break; - case KDB_REPEAT_NO_ARGS: - argc = 1; - if (argv[1]) - *(argv[1]) = '\0'; - break; - case KDB_REPEAT_WITH_ARGS: - break; - } + + if (tp->cmd_flags & KDB_REPEAT_WITH_ARGS) + return result; + + argc = tp->cmd_flags & KDB_REPEAT_NO_ARGS ? 1 : 0; + if (argv[argc]) + *(argv[argc]) = '\0'; return result; }

-- 1.9.3

Reply

Daniel Thompson

4:34 p.m.

New subject: [RESEND PATCH v5 3.19-rc2 6/8] kdb: Categorize kdb commands (similar to SysRq categorization)

This patch introduces several new flags to collect kdb commands into groups (later allowing them to be optionally disabled).

This follows similar prior art to enable/disable magic sysrq commands.

The commands have been categorized as follows:

Always on: go (w/o args), env, set, help, ?, cpu (w/o args), sr, dmesg, disable_nmi, defcmd, summary, grephelp Mem read: md, mdr, mdp, mds, ef, bt (with args), per_cpu Mem write: mm Reg read: rd Reg write: go (with args), rm Inspect: bt (w/o args), btp, bta, btc, btt, ps, pid, lsmod Flow ctrl: bp, bl, bph, bc, be, bd, ss Signal: kill Reboot: reboot All: cpu, kgdb, (and all of the above), nmi_console

Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com --- include/linux/kdb.h | 48 +++++++++++++++++- kernel/debug/kdb/kdb_bp.c | 21 +++++--- kernel/debug/kdb/kdb_main.c | 120 ++++++++++++++++++++++++++++++++------------ kernel/trace/trace_kdb.c | 2 +- 4 files changed, 148 insertions(+), 43 deletions(-)

diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 39b44b37c8dc..f1fe36185c17 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -13,9 +13,53 @@ * Copyright (C) 2009 Jason Wessel jason.wessel@windriver.com */

+/* Shifted versions of the command enable bits are be used if the command + * has no arguments (see kdb_check_flags). This allows commands, such as + * go, to have different permissions depending upon whether it is called + * with an argument. + */ +#define KDB_ENABLE_NO_ARGS_SHIFT 10 + typedef enum { - KDB_REPEAT_NO_ARGS = 0x1, /* Repeat the command w/o arguments */ - KDB_REPEAT_WITH_ARGS = 0x2, /* Repeat the command w/ its arguments */ + KDB_ENABLE_ALL = (1 << 0), /* Enable everything */ + KDB_ENABLE_MEM_READ = (1 << 1), + KDB_ENABLE_MEM_WRITE = (1 << 2), + KDB_ENABLE_REG_READ = (1 << 3), + KDB_ENABLE_REG_WRITE = (1 << 4), + KDB_ENABLE_INSPECT = (1 << 5), + KDB_ENABLE_FLOW_CTRL = (1 << 6), + KDB_ENABLE_SIGNAL = (1 << 7), + KDB_ENABLE_REBOOT = (1 << 8), + /* User exposed values stop here, all remaining flags are + * exclusively used to describe a commands behaviour. + */ + + KDB_ENABLE_ALWAYS_SAFE = (1 << 9), + KDB_ENABLE_MASK = (1 << KDB_ENABLE_NO_ARGS_SHIFT) - 1, + + KDB_ENABLE_ALL_NO_ARGS = KDB_ENABLE_ALL << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_MEM_READ_NO_ARGS = KDB_ENABLE_MEM_READ + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_MEM_WRITE_NO_ARGS = KDB_ENABLE_MEM_WRITE + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_REG_READ_NO_ARGS = KDB_ENABLE_REG_READ + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_REG_WRITE_NO_ARGS = KDB_ENABLE_REG_WRITE + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_INSPECT_NO_ARGS = KDB_ENABLE_INSPECT + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_FLOW_CTRL_NO_ARGS = KDB_ENABLE_FLOW_CTRL + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_SIGNAL_NO_ARGS = KDB_ENABLE_SIGNAL + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_REBOOT_NO_ARGS = KDB_ENABLE_REBOOT + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_ALWAYS_SAFE_NO_ARGS = KDB_ENABLE_ALWAYS_SAFE + << KDB_ENABLE_NO_ARGS_SHIFT, + KDB_ENABLE_MASK_NO_ARGS = KDB_ENABLE_MASK << KDB_ENABLE_NO_ARGS_SHIFT, + + KDB_REPEAT_NO_ARGS = 0x40000000, /* Repeat the command w/o arguments */ + KDB_REPEAT_WITH_ARGS = 0x80000000, /* Repeat the command with args */ } kdb_cmdflags_t;

typedef int (*kdb_func_t)(int, const char **); diff --git a/kernel/debug/kdb/kdb_bp.c b/kernel/debug/kdb/kdb_bp.c index f8844fb55311..e1dbf4a2c69e 100644 --- a/kernel/debug/kdb/kdb_bp.c +++ b/kernel/debug/kdb/kdb_bp.c @@ -532,21 +532,28 @@ void __init kdb_initbptab(void) bp->bp_free = 1;

kdb_register_flags("bp", kdb_bp, "[<vaddr>]", - "Set/Display breakpoints", 0, KDB_REPEAT_NO_ARGS); + "Set/Display breakpoints", 0, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); kdb_register_flags("bl", kdb_bp, "[<vaddr>]", - "Display breakpoints", 0, KDB_REPEAT_NO_ARGS); + "Display breakpoints", 0, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); if (arch_kgdb_ops.flags & KGDB_HW_BREAKPOINT) kdb_register_flags("bph", kdb_bp, "[<vaddr>]", - "[datar [length]|dataw [length]] Set hw brk", 0, KDB_REPEAT_NO_ARGS); + "[datar [length]|dataw [length]] Set hw brk", 0, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); kdb_register_flags("bc", kdb_bc, "<bpnum>", - "Clear Breakpoint", 0, 0); + "Clear Breakpoint", 0, + KDB_ENABLE_FLOW_CTRL); kdb_register_flags("be", kdb_bc, "<bpnum>", - "Enable Breakpoint", 0, 0); + "Enable Breakpoint", 0, + KDB_ENABLE_FLOW_CTRL); kdb_register_flags("bd", kdb_bc, "<bpnum>", - "Disable Breakpoint", 0, 0); + "Disable Breakpoint", 0, + KDB_ENABLE_FLOW_CTRL);

kdb_register_flags("ss", kdb_ss, "", - "Single Step", 1, KDB_REPEAT_NO_ARGS); + "Single Step", 1, + KDB_ENABLE_FLOW_CTRL | KDB_REPEAT_NO_ARGS); /* * Architecture dependent initialization. */ diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index 538bf1dce26a..fae1fc3962f8 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -188,6 +188,26 @@ struct task_struct *kdb_curr_task(int cpu) }

/* + * Check whether the flags of the current command and the permissions + * of the kdb console has allow a command to be run. + */ +static inline bool kdb_check_flags(kdb_cmdflags_t flags, int permissions, + bool no_args) +{ + /* permissions comes from userspace so needs massaging slightly */ + permissions &= KDB_ENABLE_MASK; + permissions |= KDB_ENABLE_ALWAYS_SAFE; + + /* some commands change group when launched with no arguments */ + if (no_args) + permissions |= permissions << KDB_ENABLE_NO_ARGS_SHIFT; + + flags |= KDB_ENABLE_ALL; + + return permissions & flags; +} + +/* * kdbgetenv - This function will return the character string value of * an environment variable. * Parameters: @@ -641,8 +661,13 @@ static int kdb_defcmd2(const char *cmdstr, const char *argv0) if (!s->count) s->usable = 0; if (s->usable) - kdb_register(s->name, kdb_exec_defcmd, - s->usage, s->help, 0); + /* macros are always safe because when executed each + * internal command re-enters kdb_parse() and is + * safety checked individually. + */ + kdb_register_flags(s->name, kdb_exec_defcmd, s->usage, + s->help, 0, + KDB_ENABLE_ALWAYS_SAFE); return 0; } if (!s->usable) @@ -2757,78 +2782,107 @@ static void __init kdb_inittab(void)

kdb_register_flags("md", kdb_md, "<vaddr>", "Display Memory Contents, also mdWcN, e.g. md8c1", 1, - KDB_REPEAT_NO_ARGS); + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mdr", kdb_md, "<vaddr> <bytes>", - "Display Raw Memory", 0, KDB_REPEAT_NO_ARGS); + "Display Raw Memory", 0, + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mdp", kdb_md, "<paddr> <bytes>", - "Display Physical Memory", 0, KDB_REPEAT_NO_ARGS); + "Display Physical Memory", 0, + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mds", kdb_md, "<vaddr>", - "Display Memory Symbolically", 0, KDB_REPEAT_NO_ARGS); + "Display Memory Symbolically", 0, + KDB_ENABLE_MEM_READ | KDB_REPEAT_NO_ARGS); kdb_register_flags("mm", kdb_mm, "<vaddr> <contents>", - "Modify Memory Contents", 0, KDB_REPEAT_NO_ARGS); + "Modify Memory Contents", 0, + KDB_ENABLE_MEM_WRITE | KDB_REPEAT_NO_ARGS); kdb_register_flags("go", kdb_go, "[<vaddr>]", - "Continue Execution", 1, 0); + "Continue Execution", 1, + KDB_ENABLE_REG_WRITE | KDB_ENABLE_ALWAYS_SAFE_NO_ARGS); kdb_register_flags("rd", kdb_rd, "", - "Display Registers", 0, 0); + "Display Registers", 0, + KDB_ENABLE_REG_READ); kdb_register_flags("rm", kdb_rm, "<reg> <contents>", - "Modify Registers", 0, 0); + "Modify Registers", 0, + KDB_ENABLE_REG_WRITE); kdb_register_flags("ef", kdb_ef, "<vaddr>", - "Display exception frame", 0, 0); + "Display exception frame", 0, + KDB_ENABLE_MEM_READ); kdb_register_flags("bt", kdb_bt, "[<vaddr>]", - "Stack traceback", 1, 0); + "Stack traceback", 1, + KDB_ENABLE_MEM_READ | KDB_ENABLE_INSPECT_NO_ARGS); kdb_register_flags("btp", kdb_bt, "<pid>", - "Display stack for process <pid>", 0, 0); + "Display stack for process <pid>", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("bta", kdb_bt, "[D|R|S|T|C|Z|E|U|I|M|A]", - "Backtrace all processes matching state flag", 0, 0); + "Backtrace all processes matching state flag", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("btc", kdb_bt, "", - "Backtrace current process on each cpu", 0, 0); + "Backtrace current process on each cpu", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("btt", kdb_bt, "<vaddr>", "Backtrace process given its struct task address", 0, - 0); + KDB_ENABLE_MEM_READ | KDB_ENABLE_INSPECT_NO_ARGS); kdb_register_flags("env", kdb_env, "", - "Show environment variables", 0, 0); + "Show environment variables", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("set", kdb_set, "", - "Set environment variables", 0, 0); + "Set environment variables", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("help", kdb_help, "", - "Display Help Message", 1, 0); + "Display Help Message", 1, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("?", kdb_help, "", - "Display Help Message", 0, 0); + "Display Help Message", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("cpu", kdb_cpu, "<cpunum>", - "Switch to new cpu", 0, 0); + "Switch to new cpu", 0, + KDB_ENABLE_ALWAYS_SAFE_NO_ARGS); kdb_register_flags("kgdb", kdb_kgdb, "", "Enter kgdb mode", 0, 0); kdb_register_flags("ps", kdb_ps, "[<flags>|A]", - "Display active task list", 0, 0); + "Display active task list", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("pid", kdb_pid, "<pidnum>", - "Switch to another task", 0, 0); + "Switch to another task", 0, + KDB_ENABLE_INSPECT); kdb_register_flags("reboot", kdb_reboot, "", - "Reboot the machine immediately", 0, 0); + "Reboot the machine immediately", 0, + KDB_ENABLE_REBOOT); #if defined(CONFIG_MODULES) kdb_register_flags("lsmod", kdb_lsmod, "", - "List loaded kernel modules", 0, 0); + "List loaded kernel modules", 0, + KDB_ENABLE_INSPECT); #endif #if defined(CONFIG_MAGIC_SYSRQ) kdb_register_flags("sr", kdb_sr, "<key>", - "Magic SysRq key", 0, 0); + "Magic SysRq key", 0, + KDB_ENABLE_ALWAYS_SAFE); #endif #if defined(CONFIG_PRINTK) kdb_register_flags("dmesg", kdb_dmesg, "[lines]", - "Display syslog buffer", 0, 0); + "Display syslog buffer", 0, + KDB_ENABLE_ALWAYS_SAFE); #endif if (arch_kgdb_ops.enable_nmi) { kdb_register_flags("disable_nmi", kdb_disable_nmi, "", - "Disable NMI entry to KDB", 0, 0); + "Disable NMI entry to KDB", 0, + KDB_ENABLE_ALWAYS_SAFE); } kdb_register_flags("defcmd", kdb_defcmd, "name "usage" "help"", - "Define a set of commands, down to endefcmd", 0, 0); + "Define a set of commands, down to endefcmd", 0, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("kill", kdb_kill, "<-signal> <pid>", - "Send a signal to a process", 0, 0); + "Send a signal to a process", 0, + KDB_ENABLE_SIGNAL); kdb_register_flags("summary", kdb_summary, "", - "Summarize the system", 4, 0); + "Summarize the system", 4, + KDB_ENABLE_ALWAYS_SAFE); kdb_register_flags("per_cpu", kdb_per_cpu, "<sym> [<bytes>] [<cpu>]", - "Display per_cpu variables", 3, 0); + "Display per_cpu variables", 3, + KDB_ENABLE_MEM_READ); kdb_register_flags("grephelp", kdb_grep_help, "", - "Display help on | grep", 0, 0); + "Display help on | grep", 0, + KDB_ENABLE_ALWAYS_SAFE); }

/* Execute any commands defined in kdb_cmds. */ diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c index 70fbf315bc9f..3ccf5c2c1320 100644 --- a/kernel/trace/trace_kdb.c +++ b/kernel/trace/trace_kdb.c @@ -133,7 +133,7 @@ static int kdb_ftdump(int argc, const char **argv) static __init int kdb_ftrace_register(void) { kdb_register_flags("ftdump", kdb_ftdump, "[skip_#lines] [cpu]", - "Dump ftrace log", 0, 0); + "Dump ftrace log", 0, KDB_ENABLE_ALWAYS_SAFE); return 0; }

-- 1.9.3

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Daniel Thompson

4:34 p.m.

New subject: [RESEND PATCH v5 3.19-rc2 8/8] kdb: Allow access to sensitive commands to be restricted by default

Currently kiosk mode must be explicitly requested by the bootloader or userspace. It is convenient to be able to change the default value in a similar manner to CONFIG_MAGIC_SYSRQ_DEFAULT_MASK.

Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com --- kernel/debug/kdb/kdb_main.c | 2 +- lib/Kconfig.kgdb | 25 +++++++++++++++++++++++++ 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/kernel/debug/kdb/kdb_main.c b/kernel/debug/kdb/kdb_main.c index fe1ac56b62e9..8d84979cbe05 100644 --- a/kernel/debug/kdb/kdb_main.c +++ b/kernel/debug/kdb/kdb_main.c @@ -47,7 +47,7 @@ #undef MODULE_PARAM_PREFIX #define MODULE_PARAM_PREFIX "kdb."

-static int kdb_cmd_enabled; +static int kdb_cmd_enabled = CONFIG_KDB_DEFAULT_ENABLE; module_param_named(cmd_enable, kdb_cmd_enabled, int, 0600);

#define GREP_LEN 256 diff --git a/lib/Kconfig.kgdb b/lib/Kconfig.kgdb index 358eb81fa28d..c635a107a7de 100644 --- a/lib/Kconfig.kgdb +++ b/lib/Kconfig.kgdb @@ -73,6 +73,31 @@ config KGDB_KDB help KDB frontend for kernel

+config KDB_DEFAULT_ENABLE + hex "KDB: Select kdb command functions to be enabled by default" + depends on KGDB_KDB + default 0x1 + help + Specifiers which kdb commands are enabled by default. This may + be set to 1 or 0 to enable all commands or disable almost all + commands. + + Alternatively the following bitmask applies: + + 0x0002 - allow arbitrary reads from memory and symbol lookup + 0x0004 - allow arbitrary writes to memory + 0x0008 - allow current register state to be inspected + 0x0010 - allow current register state to be modified + 0x0020 - allow passive inspection (backtrace, process list, lsmod) + 0x0040 - allow flow control management (breakpoint, single step) + 0x0080 - enable signalling of processes + 0x0100 - allow machine to be rebooted + + The config option merely sets the default at boot time. Both + issuing 'echo X > /sys/module/kdb/parameters/cmd_enable' or + setting with kdb.cmd_enable=X kernel command line option will + override the default settings. + config KDB_KEYBOARD bool "KGDB_KDB: keyboard as input device" depends on VT && KGDB_KDB

-- 1.9.3

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