* [RFC][PATCH] x86_32: Return actual stack when requesting sp from regs
@ 2012-07-13 19:44 Steven Rostedt
2012-07-18 11:41 ` Masami Hiramatsu
2012-12-09 11:32 ` [tip:x86/asm] " tip-bot for Steven Rostedt
0 siblings, 2 replies; 3+ messages in thread
From: Steven Rostedt @ 2012-07-13 19:44 UTC (permalink / raw)
To: LKML; +Cc: Masami Hiramatsu, Ingo Molnar, Andrew Morton, H. Peter Anvin, stable
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
[ I wonder if this should also go to stable? ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Index: linux-trace.git/arch/x86/include/asm/ptrace.h
===================================================================
--- linux-trace.git.orig/arch/x86/include/asm/ptrace.h
+++ linux-trace.git/arch/x86/include/asm/ptrace.h
@@ -246,6 +246,15 @@ static inline unsigned long regs_get_reg
{
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);
}
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [RFC][PATCH] x86_32: Return actual stack when requesting sp from regs
2012-07-13 19:44 [RFC][PATCH] x86_32: Return actual stack when requesting sp from regs Steven Rostedt
@ 2012-07-18 11:41 ` Masami Hiramatsu
2012-12-09 11:32 ` [tip:x86/asm] " tip-bot for Steven Rostedt
1 sibling, 0 replies; 3+ messages in thread
From: Masami Hiramatsu @ 2012-07-18 11:41 UTC (permalink / raw)
To: Steven Rostedt; +Cc: LKML, Ingo Molnar, Andrew Morton, H. Peter Anvin, stable
(2012/07/14 4:44), Steven Rostedt wrote:
>
> 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
>
> [ I wonder if this should also go to stable? ]
>
This obviously makes tracing output better on i386. Original %sp
gives nothing (or just misleading)...
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
NOTE: if someone needs to get kernel stack address from regs,
I recommend him to use kernel_stack_pointer() directly.
Thank you,
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> Index: linux-trace.git/arch/x86/include/asm/ptrace.h
> ===================================================================
> --- linux-trace.git.orig/arch/x86/include/asm/ptrace.h
> +++ linux-trace.git/arch/x86/include/asm/ptrace.h
> @@ -246,6 +246,15 @@ static inline unsigned long regs_get_reg
> {
> 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);
> }
--
Masami HIRAMATSU
Software Platform Research Dept. Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory
E-mail: masami.hiramatsu.pt@hitachi.com
^ permalink raw reply [flat|nested] 3+ messages in thread* [tip:x86/asm] x86_32: Return actual stack when requesting sp from regs
2012-07-13 19:44 [RFC][PATCH] x86_32: Return actual stack when requesting sp from regs Steven Rostedt
2012-07-18 11:41 ` Masami Hiramatsu
@ 2012-12-09 11:32 ` tip-bot for Steven Rostedt
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot for Steven Rostedt @ 2012-12-09 11:32 UTC (permalink / raw)
To: linux-tip-commits
Cc: linux-kernel, hpa, mingo, masami.hiramatsu.pt, rostedt, tglx
Commit-ID: 6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0
Gitweb: http://git.kernel.org/tip/6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0
Author: Steven Rostedt <rostedt@goodmis.org>
AuthorDate: Fri, 13 Jul 2012 15:44:14 -0400
Committer: Steven Rostedt <rostedt@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.camel@gandalf.stny.rr.com
Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@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);
}
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2012-12-09 11:33 UTC | newest]
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2012-07-13 19:44 [RFC][PATCH] x86_32: Return actual stack when requesting sp from regs Steven Rostedt
2012-07-18 11:41 ` Masami Hiramatsu
2012-12-09 11:32 ` [tip:x86/asm] " tip-bot for Steven Rostedt
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