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

[Mikko Rapeli]

On Thu, Sep 03, 2015 at 09:42:32AM +0200, Ingo Molnar wrote:
> 
> * Mikko Rapeli <mikko.rapeli@xxxxxx> 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 âstruct _fpregâ
 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 âstruct _fpxregâ
 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 âstruct _xmmregâ
 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@xxxxxxxxxx>
> 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@xxxxxx>
> Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxxxx>
> Cc: Brian Gerst <brgerst@xxxxxxxxx>
> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
> Cc: H. Peter Anvin <hpa@xxxxxxxxx>
> Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
>  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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