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| author | Steven Rostedt <rostedt@goodmis.org> | 2012-07-13 15:44:14 -0400 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2012-11-19 05:31:37 -0500 |
| commit | 6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0 (patch) | |
| tree | 4e081e4ed48d426aee8ff665d5bc42d62ce41b58 /arch/x86 | |
| parent | 28696f434fef0efa97534b59986ad33b9c4df7f8 (diff) | |
| download | blackbird-op-linux-6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0.tar.gz blackbird-op-linux-6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0.zip | |
x86_32: Return actual stack when requesting sp from regs
As x86_32 traps do not save sp when taken in kernel mode, we need to
accommodate the sp when requesting to get the register.
This affects kprobes.
Before:
# echo 'p:ftrace sys_read+4 s=%sp' > /debug/tracing/kprobe_events
# echo 1 > /debug/tracing/events/kprobes/enable
# cat trace
sshd-1345 [000] d... 489.117168: ftrace: (sys_read+0x4/0x70) s=b7e96768
sshd-1345 [000] d... 489.117191: ftrace: (sys_read+0x4/0x70) s=b7e96768
cat-1447 [000] d... 489.117392: ftrace: (sys_read+0x4/0x70) s=5a7
cat-1447 [001] d... 489.118023: ftrace: (sys_read+0x4/0x70) s=b77ad05f
less-1448 [000] d... 489.118079: ftrace: (sys_read+0x4/0x70) s=b7762e06
less-1448 [000] d... 489.118117: ftrace: (sys_read+0x4/0x70) s=b7764970
After:
sshd-1352 [000] d... 362.348016: ftrace: (sys_read+0x4/0x70) s=f3febfa8
sshd-1352 [000] d... 362.348048: ftrace: (sys_read+0x4/0x70) s=f3febfa8
bash-1355 [001] d... 362.348081: ftrace: (sys_read+0x4/0x70) s=f5075fa8
sshd-1352 [000] d... 362.348082: ftrace: (sys_read+0x4/0x70) s=f3febfa8
sshd-1352 [000] d... 362.690950: ftrace: (sys_read+0x4/0x70) s=f3febfa8
bash-1355 [001] d... 362.691033: ftrace: (sys_read+0x4/0x70) s=f5075fa8
Link: http://lkml.kernel.org/r/1342208654.30075.22.camel@gandalf.stny.rr.com
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/include/asm/ptrace.h | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index dcfde52979c3..2233713d0297 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -246,6 +246,15 @@ static inline unsigned long regs_get_register(struct pt_regs *regs, { if (unlikely(offset > MAX_REG_OFFSET)) return 0; +#ifdef CONFIG_X86_32 + /* + * Traps from the kernel do not save sp and ss. + * Use the helper function to retrieve sp. + */ + if (offset == offsetof(struct pt_regs, sp) && + regs->cs == __KERNEL_CS) + return kernel_stack_pointer(regs); +#endif return *(unsigned long *)((unsigned long)regs + offset); } |
