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

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Message-ID: <0795204d-575c-40b9-b5b0-75ab14eee330@email.android.com>
Date:	Sat, 12 Jul 2014 11:40:03 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>,
	Andy Lutomirski <luto@...capital.net>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH 2/2] x86_64,signal: Remove 'fs' and 'gs' from sigcontext

Because you are doing something weird (like Pin, for example) and take an asynchronous fault?

On July 12, 2014 11:37:48 AM PDT, Andi Kleen <andi@...stfloor.org> wrote:
>> This seems like it's asking for trouble.  I think wxe'd have to
>> separately save the selectors and the base registers to avoid
>breaking
>> something, especially once wrgsbase, etc are enabled.
>
>I agree, it would likely break existing code.
>
>> Linus, for context, the other patch in this series saves and restores
>> SS. 
>
>> Without that, 64-bit sigreturn to a nondefault stack segment is
>> basically impossible.  
>
>Why would you ever want to do that?
>
>-Andi

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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