Ingo, Peter, I posted this back in July as an RFC and did get Masami's reviewed-by tag. I'm currently cleaning out my inbox and realized I didn't push this further. I didn't know which branch to base this on, so I just picked the tip/x86/asm branch where I did my last x86 work in.
https://lkml.org/lkml/2012/7/13/351 Please pull the latest tip/x86/asm tree, which can be found at: git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace.git tip/x86/asm Head SHA1: 6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0 Steven Rostedt (1): x86_32: Return actual stack when requesting sp from regs ---- arch/x86/include/asm/ptrace.h | 9 +++++++++ 1 file changed, 9 insertions(+) --------------------------- commit 6c8d8b3c69cef1330e0c5cbc2a8b9268024927a0 Author: Steven Rostedt <[email protected]> Date: Fri Jul 13 15:44:14 2012 -0400 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/[email protected] Reviewed-by: Masami Hiramatsu <[email protected]> Signed-off-by: Steven Rostedt <[email protected]> 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); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
