Messages in this thread | | | Date | Sun, 23 Nov 2008 18:30:59 +0100 | From | Alexander van Heukelum <> | Subject | Re: [PATCH] x86: remove the confusing entry in call trace |
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On Sun, Nov 23, 2008 at 10:47:10PM +0800, jia zhang wrote: > > avoid the confusion in call trace because of the lack of padding at the tail of > function. > > Signed-off-by: jia zhang <jia.zhang2008@gmail.com> --- When do_exit get call, > the return address behind call instruction is pushed into stack. If something > get wrong in do_exit, for x86_64, the entry "kernel_execve +0x00/0xXX" rather > than "child_rip +0xYY/0xZZ" is remained in call trace. It looks confused.
It's valuable to know from where do_exit is called, so that's the only reason why using "call" is important. Otherwise it could just be changed to a jmp as do_exit does not return. It's maybe a bit ugly to add the padding, but it does give better traces. Maybe a 'ret', 'int3', or 'ud2' would be slightly less offensive?
Anyhow, I don't have a problem with the added padding, so:
Acked-by: Alexander van Heukelum <heukelum@fastmail.fm>
> b/arch/x86/kernel/entry_32.S | 1 + > b/arch/x86/kernel/entry_64.S | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S > index 28b597e..3290819 100644 > --- a/arch/x86/kernel/entry_32.S > +++ b/arch/x86/kernel/entry_32.S > @@ -1051,6 +1051,7 @@ ENTRY(kernel_thread_helper) > push %eax > CFI_ADJUST_CFA_OFFSET 4 > call do_exit > + nop # padding for call trace > CFI_ENDPROC > ENDPROC(kernel_thread_helper) > > diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S > index b86f332..6f677a6 100644 > --- a/arch/x86/kernel/entry_64.S > +++ b/arch/x86/kernel/entry_64.S > @@ -1170,6 +1170,7 @@ child_rip: > # exit > mov %eax, %edi > call do_exit > + nop # padding for call trace > CFI_ENDPROC > ENDPROC(child_rip)
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