linux-kernel - Re: [PATCH] i386: add unwind directives to syscall ptregs stubs

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Date:	Fri, 03 Sep 2010 01:09:06 +0200
From:	"Alexander van Heukelum" <heukelum@...tmail.fm>
To:	"Jan Beulich" <JBeulich@...ell.com>, "Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i386: add unwind directives to syscall ptregs stubs

On Thu, 02 Sep 2010 14:04 +0100, "Jan Beulich" <JBeulich@...ell.com> wrote:
> When these stubs are actual functions (i.e. having a return
> instruction) and have stack manipulation instructions in them, they
> should also be annotated to allow unwinding through them.
> 
> Signed-off-by: Jan Beulich <jbeulich@...ell.com>

Compiles to exactly the same machine code.

Acked-by: Alexander van Heukelum <heukelum@...tmail.fm>

> ---
>  arch/x86/kernel/entry_32.S    |  16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> --- linux-2.6.36-rc3/arch/x86/kernel/entry_32.S
> +++ 2.6.36-rc3-x86-push-pop-cfi/arch/x86/kernel/entry_32.S
> @@ -750,14 +710,18 @@ ptregs_##name: \
>  #define PTREGSCALL3(name) \
>  	ALIGN; \
>  ptregs_##name: \
> +       CFI_STARTPROC; \
>  	leal 4(%esp),%eax; \
> -       pushl %eax; \
> +       pushl_cfi %eax; \
>  	movl PT_EDX(%eax),%ecx; \
>  	movl PT_ECX(%eax),%edx; \
>  	movl PT_EBX(%eax),%eax; \
>  	call sys_##name; \
>  	addl $4,%esp; \
> -       ret
> +       CFI_ADJUST_CFA_OFFSET -4; \
> +       ret; \
> +       CFI_ENDPROC; \
> +ENDPROC(ptregs_##name)
>  
>  PTREGSCALL1(iopl)
>  PTREGSCALL0(fork)
> @@ -772,15 +736,19 @@ PTREGSCALL1(vm86old)
>  /* Clone is an oddball.  The 4th arg is in %edi */
>  	ALIGN;
>  ptregs_clone:
> +       CFI_STARTPROC
>  	leal 4(%esp),%eax
> -       pushl %eax
> -       pushl PT_EDI(%eax)
> +       pushl_cfi %eax
> +       pushl_cfi PT_EDI(%eax)
>  	movl PT_EDX(%eax),%ecx
>  	movl PT_ECX(%eax),%edx
>  	movl PT_EBX(%eax),%eax
>  	call sys_clone
>  	addl $8,%esp
> +       CFI_ADJUST_CFA_OFFSET -8
>  	ret
> +       CFI_ENDPROC
> +ENDPROC(ptregs_clone)
>  
>  .macro FIXUP_ESPFIX_STACK
>  /*
> 
> 
> 
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