Commit-ID: 6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0
Gitweb: http://git.kernel.org/tip/6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0
Author: Steven Rostedt <rost...@goodmis.org>
AuthorDate: Fri, 13 Jul 2012 15:44:14 -0400
Committer: Steven Rostedt <rost...@goodmis.org>
CommitDate: Mon, 19 Nov 2012 05:31:37 -0500
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.ca...@gandalf.stny.rr.com
Reviewed-by: Masami Hiramatsu <masami.hiramatsu...@hitachi.com>
Signed-off-by: Steven Rostedt <rost...@goodmis.org>
---
arch/x86/include/asm/ptrace.h | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index dcfde52..2233713 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);
}
--
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