x86, 32-bit: fix kernel_trap_sp()

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 <[email protected]>
[ v2: rename the API to kernel_stack_pointer(), move variable inside ]
Acked-by: Linus Torvalds <[email protected]>
Cc: [email protected]
Cc: Harvey Harrison <[email protected]>
Cc: Jan Blunck <[email protected]>
Cc: Christoph Hellwig <[email protected]>
LKML-Reference: <20090511210300[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h
index e304b66abeea6eeb819f9c682124b67ff27e05fb..624f133943ed71293aaba1477b9ca20ad0836da8 100644 (file)
--- a/arch/x86/include/asm/ptrace.h
+++ b/arch/x86/include/asm/ptrace.h
@@ -187,14 +187,15 @@ 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.  The previous stack will be directly underneath the saved
+ * registers, and 'sp/ss' won't even have been saved. Thus the '&regs->sp'.
  *
  * This is valid only for kernel mode traps.
  */
-static inline unsigned long kernel_trap_sp(struct pt_regs *regs)
+static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
 {
 #ifdef CONFIG_X86_32
-       return (unsigned long)regs;
+       return (unsigned long)(&regs->sp);
 #else
        return regs->sp;
 #endif

diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c
index 04df67f8a7ba8f2f8c397832eec1b6fb0180ef8d..044897be021f0ed4a7bfc3eb3ee6208d2ae37dab 100644 (file)
--- a/arch/x86/oprofile/backtrace.c
+++ b/arch/x86/oprofile/backtrace.c
@@ -76,9 +76,9 @@ void
 x86_backtrace(struct pt_regs * const regs, unsigned int depth)
 {
        struct frame_head *head = (struct frame_head *)frame_pointer(regs);
-       unsigned long stack = kernel_trap_sp(regs);
 
        if (!user_mode_vm(regs)) {
+               unsigned long stack = kernel_stack_pointer(regs);
                if (depth)
                        dump_trace(NULL, regs, (unsigned long *)stack, 0,
                                   &backtrace_ops, &depth);