linux-kernel - Re: [PATCH] x86/headers: Fix (old) header file dependency bug in uapi/asm/sigcontext32.h

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Date:	Fri, 4 Sep 2015 10:10:31 +0300
From:	Mikko Rapeli <mikko.rapeli@....fi>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] x86/headers: Fix (old) header file dependency bug in
 uapi/asm/sigcontext32.h

On Thu, Sep 03, 2015 at 09:42:32AM +0200, Ingo Molnar wrote:
> 
> * Mikko Rapeli <mikko.rapeli@....fi> wrote:
> 
> > Hi Ingo, Thomas and Peter,
> > 
> > Do you have any pointers for me how arch/x86/include/uapi/asm/sigcontext32.h
> > could be fixed to also compile in userspace? Is definition of _fpx_sw_bytes
> > or _fpstate_ia32 even needed there?
> > 
> > Instructions to reproduce the userspace build failure are here:
> > https://lkml.org/lkml/2015/5/30/98
> 
> Yeah, so this is a real bug in the headers, good find.
> 
> Also note that somewhat luckily your testcase is artificial, no real user-space 
> code can contain that code at the moment because the header never built standalone 
> in the past either AFAICS.
> 
> So it's an old header file dependency bug, to make it build in user-space you need 
> to do this workaround:
> 
>  #include <asm/sigcontext.h>
>  #include <asm/sigcontext32.h>
> 
> If you only include sigcontext32.h:
> 
>  #include <asm/sigcontext32.h>
> 
> it will fail to build.
> 
> To fix the bug:
> 
> > > --- a/arch/x86/include/uapi/asm/sigcontext32.h
> > > +++ b/arch/x86/include/uapi/asm/sigcontext32.h
> > > @@ -45,7 +45,6 @@ struct _fpstate_ia32 {
> > >  	__u32	padding[44];
> > >  	union {
> > >  		__u32 padding2[12];
> > > -		struct _fpx_sw_bytes sw_reserved;
> > >  	};
> > >  };
> 
> No, those fields are real and compat sigframe handling user-space might be relying 
> on them.
>
> Does the fix below work for you?

Unfortunately no:

cc -Wall -c -nostdinc -I /usr/lib/gcc/i586-linux-gnu/5/include -I /usr/lib/gcc/i
586-linux-gnu/5/include-fixed -I . -I ../headers_compile_test_include -I ../head
ers_compile_test_include/i586-linux-gnu ./asm/sigcontext32.c
In file included from ./asm/sigcontext32.c:1:0:
./asm/sigcontext32.h:12:8: error: redefinition of ‘struct _fpreg’
 struct _fpreg {
        ^
In file included from ./asm/sigcontext32.h:6:0,
                 from ./asm/sigcontext32.c:1:
./asm/sigcontext.h:56:8: note: originally defined here
 struct _fpreg {
        ^
In file included from ./asm/sigcontext32.c:1:0:
./asm/sigcontext32.h:17:8: error: redefinition of ‘struct _fpxreg’
 struct _fpxreg {
        ^
In file included from ./asm/sigcontext32.h:6:0,
                 from ./asm/sigcontext32.c:1:
./asm/sigcontext.h:61:8: note: originally defined here
 struct _fpxreg {
        ^
In file included from ./asm/sigcontext32.c:1:0:
./asm/sigcontext32.h:23:8: error: redefinition of ‘struct _xmmreg’
 struct _xmmreg {
        ^
In file included from ./asm/sigcontext32.h:6:0,
                 from ./asm/sigcontext32.c:1:
./asm/sigcontext.h:67:8: note: originally defined here
 struct _xmmreg {
        ^
FAILED: ./asm/sigcontext32.h

I guess this was the reason why I ended with the hack.

-Mikko

> Thanks,
> 
> 	Ingo
> 
> =========================>
> >From 0bcdebb70e1ae246139df71acfa744ab1629d877 Mon Sep 17 00:00:00 2001
> From: Ingo Molnar <mingo@...nel.org>
> Date: Thu, 3 Sep 2015 09:35:19 +0200
> Subject: [PATCH] x86/headers: Fix (old) header file dependency bug in uapi/asm/sigcontext32.h
> 
> Mikko Rapeli reported that the following standalone user-space header does not compile:
> 
>   #include <asm/sigcontext32.h>
> 
> Due to undefined 'struct __fpx_sw_bytes' which is defined in asm/sigcontext.h.
> 
> The following header order works:
> 
>   #include <asm/sigcontext.h>
>   #include <asm/sigcontext32.h>
> 
> and that's probably how everyone's been using these headers for the past decade or
> so, but it's a legit header file dependency bug, so include asm/sigcontext.h in
> sigcontext32.h to allow it to be built standlone.
> 
> Reported-by: Mikko Rapeli <mikko.rapeli@....fi>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Brian Gerst <brgerst@...il.com>
> Cc: Denys Vlasenko <dvlasenk@...hat.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Ingo Molnar <mingo@...nel.org>
> ---
>  arch/x86/include/uapi/asm/sigcontext32.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/x86/include/uapi/asm/sigcontext32.h b/arch/x86/include/uapi/asm/sigcontext32.h
> index ad1478c4ae12..ff7826c41a1c 100644
> --- a/arch/x86/include/uapi/asm/sigcontext32.h
> +++ b/arch/x86/include/uapi/asm/sigcontext32.h
> @@ -3,6 +3,8 @@
>  
>  #include <linux/types.h>
>  
> +#include <asm/sigcontext.h>
> +
>  /* signal context for 32bit programs. */
>  
>  #define X86_FXSR_MAGIC		0x0000
> 
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