From 6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Fri, 13 Jul 2012 15:44:14 -0400 Subject: 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 Signed-off-by: Steven Rostedt --- arch/x86/include/asm/ptrace.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'arch/x86/include/asm/ptrace.h') diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index dcfde52979c3..2233713d0297 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); } -- cgit v1.2.1