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

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Message-ID: <0b46d9d7-30f7-4aee-be9e-dd83cf8056d9@email.android.com>
Date:	Fri, 11 Jul 2014 19:26:50 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>
CC:	Andi Kleen <andi@...stfloor.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] x86_64,signal: Remove 'fs' and 'gs' from sigcontext

Our current handling of fs/vs is really weird.  The best may very well be to explicitly save and restore both fs and he as part of Andi's patchset to support wrxsbase.

On July 11, 2014 7:21:54 PM PDT, Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>On Fri, Jul 11, 2014 at 9:29 AM, Andy Lutomirski <luto@...capital.net>
>wrote:
>> As far as I can tell, these fields have been set to zero on save and
>> ignored on restore since Linux was imported into git.  Rename them
>> '__pad1' and '__pad2' to avoid confusion and to allow them to be
>> recycled some day.
>
>Shouldn't we actually try to save/restore gs/fs properly? Admittedly,
>changing them in the signal handler would be insane, but still.. See
>our context switching code  with the whole segment selector vs base
>save/restore code. Hmm?
>
>            Linus

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