[PATCH -rc] [BUGFIX] x86: fix kernel_trap_sp()

[Masami Hiramatsu]

Use &regs->sp instead of regs for getting the top of stack in kernel mode.
(on x86-64, regs->sp always points the top of stack)

[ impact: Oprofile decodes only stack for backtracing on i386 ]

Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Harvey Harrison <harvey.harrison@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Jan Blunck <jblunck@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
---

 arch/x86/include/asm/ptrace.h |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index 5cdd19f..90b76b3 100644
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -187,14 +187,14 @@ static inline int v8086_mode(struct pt_regs *regs)
 
 /*
  * X86_32 CPUs don't save ss and esp if the CPU is already in kernel mode
- * when it traps.  So regs will be the current sp.
+ * when it traps.  So &regs->sp will be the current sp.
  *
  * This is valid only for kernel mode traps.
  */
 static inline unsigned long kernel_trap_sp(struct pt_regs *regs)
 {
 #ifdef CONFIG_X86_32
-	return (unsigned long)regs;
+	return (unsigned long)&regs->sp;
 #else
 	return regs->sp;
 #endif

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