On Tue, Aug 06, 2013 at 07:12:06AM +0100, Sandeepa Prabhu wrote:
AArch64 Single Steping and Breakpoint debug exceptions will be used by multiple debug framworks like kprobes & kgdb.
This patch implements the hooks for those frameworks to register their own handlers for handling breakpoint and single step events.
Reworked the debug exception handler in entry.S: do_dbg to pass the correct break/step address to the handlers, i.e. FAR_EL1 if exception is watchpoint, ELR_EL1 for all other debug exceptions.
Signed-off-by: Sandeepa Prabhu sandeepa.prabhu@linaro.org Signed-off-by: Deepak Saxena dsaxena@linaro.org
arch/arm64/include/asm/debug-monitors.h | 20 +++++++ arch/arm64/kernel/debug-monitors.c | 102 +++++++++++++++++++++++++++++++- arch/arm64/kernel/entry.S | 6 +- 3 files changed, 124 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h index a2232d0..aff3a76 100644 --- a/arch/arm64/include/asm/debug-monitors.h +++ b/arch/arm64/include/asm/debug-monitors.h @@ -16,6 +16,8 @@ #ifndef __ASM_DEBUG_MONITORS_H #define __ASM_DEBUG_MONITORS_H +#include <linux/list.h>
#ifdef __KERNEL__ #define DBG_ESR_EVT(x) (((x) >> 27) & 0x7) @@ -62,6 +64,24 @@ struct task_struct; #define DBG_ARCH_ID_RESERVED 0 /* In case of ptrace ABI updates. */ +struct step_hook {
- struct list_head node;
- int (*fn)(struct pt_regs *regs, unsigned int insn, unsigned long addr);
+};
Shouldn't that be esr instead of insn?
+void register_step_hook(struct step_hook *hook); +void unregister_step_hook(struct step_hook *hook);
+struct break_hook {
- struct list_head node;
- u32 esr_magic;
There's nothing magic about it. esr_val instead?
- u32 esr_mask;
- int (*fn)(struct pt_regs *regs, unsigned int insn, unsigned long addr);
+};
+void register_break_hook(struct break_hook *hook); +void unregister_break_hook(struct break_hook *hook);
u8 debug_monitors_arch(void); void enable_debug_monitors(enum debug_el el); diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index cbfacf7..2846327 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -188,6 +188,54 @@ static void clear_regs_spsr_ss(struct pt_regs *regs) regs->pstate = spsr; } +/* EL1 Single Step Handler hooks */ +static LIST_HEAD(step_hook); +static DEFINE_RAW_SPINLOCK(step_lock);
+void register_step_hook(struct step_hook *hook) +{
- unsigned long flags;
- raw_spin_lock_irqsave(&step_lock, flags);
- list_add(&hook->node, &step_hook);
- raw_spin_unlock_irqrestore(&step_lock, flags);
+}
+void unregister_step_hook(struct step_hook *hook) +{
- unsigned long flags;
- raw_spin_lock_irqsave(&step_lock, flags);
- list_del(&hook->node);
- raw_spin_unlock_irqrestore(&step_lock, flags);
+}
Why do you need to disable IRQs during these operations?
+/*
- Call registered single step handers
- There is no Syndrome info to check for determining the handler.
- So we call all the registered handlers, until the right handler is
- found which returns zero.
- */
+static int call_step_hook(struct pt_regs *regs,
unsigned int esr, unsigned long addr)+{
- struct step_hook *hook;
- unsigned long flags;
- raw_spin_lock_irqsave(&step_lock, flags);
- list_for_each_entry(hook, &step_hook, node) {
raw_spin_unlock_irqrestore(&step_lock, flags);
Is this safe? Can't you stask the function pointer and break out of the loop when you find it instead?
if (hook->fn(regs, esr, addr) == 0)return 0;raw_spin_lock_irqsave(&step_lock, flags);- }
- raw_spin_unlock_irqrestore(&step_lock, flags);
- return 1;
+}
static int single_step_handler(unsigned long addr, unsigned int esr, struct pt_regs *regs) { @@ -215,8 +263,11 @@ static int single_step_handler(unsigned long addr, unsigned int esr, */ user_rewind_single_step(current); } else {
/* TODO: route to KGDB */pr_warning("Unexpected kernel single-step exception at EL1\n");
/* Call single step handlers for kgdb/kprobes */if (call_step_hook(regs, addr, esr) == 0)return 0;pr_warn("unexpected single step exception at %lx!\n", addr);
- Re-enable stepping since we know that we will be
- returning to regs.
@@ -227,11 +278,56 @@ static int single_step_handler(unsigned long addr, unsigned int esr, return 0; }
+static LIST_HEAD(break_hook); +static DEFINE_RAW_SPINLOCK(break_lock);
+void register_break_hook(struct break_hook *hook) +{
- unsigned long flags;
- raw_spin_lock_irqsave(&break_lock, flags);
- list_add(&hook->node, &break_hook);
- raw_spin_unlock_irqrestore(&break_lock, flags);
+}
+void unregister_break_hook(struct break_hook *hook) +{
- unsigned long flags;
- raw_spin_lock_irqsave(&break_lock, flags);
- list_del(&hook->node);
- raw_spin_unlock_irqrestore(&break_lock, flags);
+}
+static int call_break_hook(struct pt_regs *regs,
unsigned int esr, unsigned long addr)+{
- struct break_hook *hook;
- unsigned long flags;
- int (*fn)(struct pt_regs *regs,
unsigned int esr, unsigned long addr) = NULL;- raw_spin_lock_irqsave(&break_lock, flags);
- list_for_each_entry(hook, &break_hook, node)
if ((esr & hook->esr_mask) == hook->esr_magic)fn = hook->fn;- raw_spin_unlock_irqrestore(&break_lock, flags);
That's better! (although I'm still unsure about the interrupts).
- return fn ? fn(regs, esr, addr) : 1;
+}
static int brk_handler(unsigned long addr, unsigned int esr, struct pt_regs *regs) { siginfo_t info;
- /* Call single step handlers for kgdb/kprobes */
- if (call_break_hook(regs, esr, addr) == 0)
return 0;- pr_warn("unexpected brk exception at %lx, esr=0x%x\n", addr, esr);
- if (!user_mode(regs)) return -EFAULT;
@@ -291,7 +387,7 @@ static int __init debug_traps_init(void) hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP, TRAP_HWBKPT, "single-step handler"); hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP,
TRAP_BRKPT, "ptrace BRK handler");
TRAP_BRKPT, "AArch64 BRK handler");
Why change this name?
return 0; } arch_initcall(debug_traps_init); diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 6ad781b..e7350bd 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -288,8 +288,12 @@ el1_dbg: /* * Debug exception handling */
- mrs x25, far_el1 //far for watchpt
Useless comment. How about: "// Watchpoint location"?
- cmp x24, #ESR_EL1_EC_WATCHPT_EL1
- csel x0, x25, x22, eq //addr: x25->far_el1, x22->elr_el1
- b.ge do_dbg tbz x24, #0, el1_inv // EL1 only
I'd rather you left the tbz as the first instruction in el1_dbg, then you can also lose the b.ge.
Finally, I don't see the need for this patch until we have something like kprobes or kgdb, so I'd rather hold off merging this additional support code until we have a user for it.
Cheers,
Will