From 7b6c6c77732ca1d2498eda7eabb64f9648896e96 Mon Sep 17 00:00:00 2001 From: Masami Hiramatsu Date: Mon, 11 May 2009 17:03:00 -0400 Subject: [PATCH] x86, 32-bit: fix kernel_trap_sp() Use ®s->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 [ v2: rename the API to kernel_stack_pointer(), move variable inside ] Acked-by: Linus Torvalds Cc: systemtap@sources.redhat.com Cc: Harvey Harrison Cc: Jan Blunck Cc: Christoph Hellwig LKML-Reference: <20090511210300.17332.67549.stgit@localhost.localdomain> Signed-off-by: Ingo Molnar --- arch/x86/include/asm/ptrace.h | 7 ++++--- arch/x86/oprofile/backtrace.c | 2 +- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index e304b66..624f133 100644 --- 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 '®s->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)(®s->sp); #else return regs->sp; #endif diff --git a/arch/x86/oprofile/backtrace.c b/arch/x86/oprofile/backtrace.c index 04df67f..044897b 100644 --- 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); -- 1.8.2.3