From e3944bfac961cd7fc82f3b3143c55dc375748569 Mon Sep 17 00:00:00 2001 From: Steven Rostedt <srostedt@redhat.com> Date: Tue, 10 Feb 2009 13:07:13 -0500 Subject: [PATCH] tracing, x86: fix fixup section to return to original code Impact: fix to prevent a kernel crash on fault If for some reason the pointer to the parent function on the stack takes a fault, the fix up code will not return back to the original faulting code. This can lead to unpredictable results and perhaps even a kernel panic. A fault should not happen, but if it does, we should simply disable the tracer, warn, and continue running the kernel. It should not lead to a kernel crash. Signed-off-by: Steven Rostedt <srostedt@redhat.com> --- arch/x86/kernel/ftrace.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index 1b43086b097a..9d549e4fe880 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -491,13 +491,15 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr) "1: " _ASM_MOV " (%[parent_old]), %[old]\n" "2: " _ASM_MOV " %[return_hooker], (%[parent_replaced])\n" " movl $0, %[faulted]\n" + "3:\n" ".section .fixup, \"ax\"\n" - "3: movl $1, %[faulted]\n" + "4: movl $1, %[faulted]\n" + " jmp 3b\n" ".previous\n" - _ASM_EXTABLE(1b, 3b) - _ASM_EXTABLE(2b, 3b) + _ASM_EXTABLE(1b, 4b) + _ASM_EXTABLE(2b, 4b) : [parent_replaced] "=r" (parent), [old] "=r" (old), [faulted] "=r" (faulted)