linux-kernel - Re: [PATCH] x86: uapi: Fix __BITS_PER

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Date:	Fri, 02 Oct 2015 02:52:27 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Brian Gerst <brgerst@...il.com>, Ingo Molnar <mingo@...nel.org>
Cc:	the arch/x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH] x86: uapi: Fix __BITS_PER_LONG for x32

On Thu, 2015-10-01 at 21:54 +0100, Ben Hutchings wrote:
> On Thu, 2015-10-01 at 09:02 -0400, Brian Gerst wrote:
> > On Thu, Oct 1, 2015 at 4:23 AM, Ingo Molnar <mingo@...nel.org> wrote:
> > > 
> > > * Ben Hutchings <ben@...adent.org.uk> wrote:
> > > 
> > > > diff --git a/arch/x86/include/uapi/asm/bitsperlong.h
> > > > b/arch/x86/include/uapi/asm/bitsperlong.h
> > > > index b0ae1c4..217909b 100644
> > > > --- a/arch/x86/include/uapi/asm/bitsperlong.h
> > > > +++ b/arch/x86/include/uapi/asm/bitsperlong.h
> > > > @@ -1,7 +1,7 @@
> > > >  #ifndef __ASM_X86_BITSPERLONG_H
> > > >  #define __ASM_X86_BITSPERLONG_H
> > > > 
> > > > -#ifdef __x86_64__
> > > > +#if defined(__x86_64__) && !defined(__ILP32__)
> > > >  # define __BITS_PER_LONG 64
> > > 
> > > Can we write this as:
> > > 
> > >    #ifdef __ILP64__
> 
> Assuming you meant __LP64__...
> 
> > Do all versions of gcc/clang define that, even if x32 isn't
> > supported?
> 
> For gcc, it's been defined since 2003 (gcc 3.3):
> https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=0bdab2d89e28ca4dc84f8f0fafed85a4822bca49
> 
> For clang, it's been defined since before its first public release:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Basic/Targets.cpp?r1=38978&r2=38987&pathrev=161685
> 
> So gcc 3.1 and 3.2 didn't define it, but everything newer does.

As the kernel itself is supposed to still be compilable with gcc 3.2, I
think this means that my patch has the right condition.

Ben.

-- 
Ben Hutchings
When in doubt, use brute force. - Ken Thompson
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