linux-kernel - Re: [PATCH 2/2] x86_64,signal: Remove 'fs' and 'gs' from sigcontext

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Date:	Fri, 11 Jul 2014 19:09:03 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andy Lutomirski <luto@...capital.net>,
	Andi Kleen <andi@...stfloor.org>
CC:	Al Viro <viro@...iv.linux.org.uk>, X86 ML <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 2/2] x86_64,signal: Remove 'fs' and 'gs' from sigcontext

On 07/11/2014 11:39 AM, Andy Lutomirski wrote:
> On Fri, Jul 11, 2014 at 11:12 AM, Andi Kleen <andi@...stfloor.org> wrote:
>>> diff --git a/arch/x86/include/uapi/asm/sigcontext.h b/arch/x86/include/uapi/asm/sigcontext.h
>>> index 076b11f..df9908b 100644
>>> --- a/arch/x86/include/uapi/asm/sigcontext.h
>>> +++ b/arch/x86/include/uapi/asm/sigcontext.h
>>
>> I don't think renaming fields in uapi/asm is acceptable. These
>> are likely used by user programs and you'll break compiles.
> 
> Hmm.  That's a fair point.  On the other hand, any user code that uses
> these fields explicitly may already be broken, since the current names
> of these fields rather strongly imply that they do something.
> 
> Is there any clear policy on minor API breaks in the UAPI headers that
> don't affect ABI?
> 

There really isn't, and this *definitely* a boundary case: as you state,
it is very likely that anyone currently using them are doing so
incorrectly, but it does induce potential source-level breakage.

Linus, do you have any guidance here?

	-hpa

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