Currently when kdb traps printk messages then the raw log level prefix (consisting of '\001' followed by a numeral) does not get stripped off before the message is issued to the various I/O handlers supported by kdb. This causes annoying visual noise as well as causing problems grepping for ^. It is also a change of behaviour compared to normal usage of printk() usage. For example <SysRq>-h ends up with different output to that of kdb's "sr h".
This patch addresses the problem by stripping log levels from messages before they are issued to the I/O handlers. printk() which can also act as an i/o handler in some cases is special cased; if the caller provided a log level then the prefix will be preserved when sent to printk().
The addition of non-printable characters to the output of kdb commands is a regression, albeit and extremely elderly one, introduced by commit 04d2c8c83d0e ("printk: convert the format for KERN_<LEVEL> to a 2 byte pattern"). Note also that this patch does *not* restore the original behaviour from v3.5. Instead it makes printk() from within a kdb command display the message without any prefix (i.e. like printk() normally does).
Signed-off-by: Daniel Thompson daniel.thompson@linaro.org Cc: Jason Wessel jason.wessel@windriver.com Cc: Joe Perches joe@perches.com Cc: stable@vger.kernel.org ---
Notes: This patch is tested both on arm (kgdboc=ttyAMA0) and x86_64 (kgdboc=kdb,ttyS0).
v3:
* Introduce enum kdb_msgsrc to further improve the fidelity of messages that hit the log (Joe Perches). The output of "sr h" benefits a lot from this change.
v2:
* Adopt printk_skip_level() to skip the header characters (Joe Perches).
* Update patch description to describe the addition of non-printable characters to kdb output as a regression and Cc: stable@ (Joe Perches).
include/linux/kdb.h | 8 +++++++- kernel/debug/kdb/kdb_io.c | 22 +++++++++++++--------- kernel/printk/printk.c | 2 +- 3 files changed, 21 insertions(+), 11 deletions(-)
diff --git a/include/linux/kdb.h b/include/linux/kdb.h index 290db1269c4c..204901ae003a 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -112,8 +112,14 @@ typedef enum { KDB_REASON_SYSTEM_NMI, /* In NMI due to SYSTEM cmd; regs valid */ } kdb_reason_t;
+enum kdb_msgsrc { + KDB_MSGSRC_INTERNAL, /* direct call to kdb_printf() */ + KDB_MSGSRC_PRINTK, /* trapped from printk() */ +}; + extern int kdb_trap_printk; -extern __printf(1, 0) int vkdb_printf(const char *fmt, va_list args); +extern __printf(2, 0) int vkdb_printf(enum kdb_msgsrc src, const char *fmt, + va_list args); extern __printf(1, 2) int kdb_printf(const char *, ...); typedef __printf(1, 2) int (*kdb_printf_t)(const char *, ...);
diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index 7c70812caea5..a550afb99ebe 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -548,7 +548,7 @@ static int kdb_search_string(char *searched, char *searchfor) return 0; }
-int vkdb_printf(const char *fmt, va_list ap) +int vkdb_printf(enum kdb_msgsrc src, const char *fmt, va_list ap) { int diag; int linecount; @@ -691,19 +691,20 @@ kdb_printit: * Write to all consoles. */ retlen = strlen(kdb_buffer); + cp = (char *) printk_skip_level(kdb_buffer); if (!dbg_kdb_mode && kgdb_connected) { - gdbstub_msg_write(kdb_buffer, retlen); + gdbstub_msg_write(cp, retlen - (cp - kdb_buffer)); } else { if (dbg_io_ops && !dbg_io_ops->is_console) { - len = retlen; - cp = kdb_buffer; + len = retlen - (cp - kdb_buffer); + cp2 = cp; while (len--) { - dbg_io_ops->write_char(*cp); - cp++; + dbg_io_ops->write_char(*cp2); + cp2++; } } while (c) { - c->write(c, kdb_buffer, retlen); + c->write(c, cp, retlen - (cp - kdb_buffer)); touch_nmi_watchdog(); c = c->next; } @@ -711,7 +712,10 @@ kdb_printit: if (logging) { saved_loglevel = console_loglevel; console_loglevel = CONSOLE_LOGLEVEL_SILENT; - printk(KERN_INFO "%s", kdb_buffer); + if (printk_get_level(kdb_buffer) || src == KDB_MSGSRC_PRINTK) + printk("%s", kdb_buffer); + else + pr_info("%s", kdb_buffer); }
if (KDB_STATE(PAGER)) { @@ -844,7 +848,7 @@ int kdb_printf(const char *fmt, ...) int r;
va_start(ap, fmt); - r = vkdb_printf(fmt, ap); + r = vkdb_printf(KDB_MSGSRC_INTERNAL, fmt, ap); va_end(ap);
return r; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index ced2b84b1cb7..3a884ab1b9cb 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1836,7 +1836,7 @@ asmlinkage __visible int printk(const char *fmt, ...) #ifdef CONFIG_KGDB_KDB if (unlikely(kdb_trap_printk)) { va_start(args, fmt); - r = vkdb_printf(fmt, args); + r = vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args); va_end(args); return r; } -- 1.9.3