linux-kernel - Re: [PATCH v2 1/4] x86/signal/64: Add a comment about sigcontext->fs and gs

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Message-ID: <56827B97.9060106@list.ru>
Date:	Tue, 29 Dec 2015 15:24:55 +0300
From:	Stas Sergeev <stsp@...t.ru>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Brian Gerst <brgerst@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v2 1/4] x86/signal/64: Add a comment about sigcontext->fs
 and gs

08.12.2015 02:23, Andy Lutomirski пишет:
> On Oct 31, 2015 8:25 AM, "Stas Sergeev" <stsp@...t.ru> wrote:
>>
>> 26.10.2015 04:25, Andy Lutomirski пишет:
>>
>>> These fields have a strange history.  This tries to document it.
>>>
>>> This borrows from 9a036b93a344 ("x86/signal/64: Remove 'fs' and 'gs'
>>> from sigcontext"), which was reverted by ed596cde9425 ("Revert x86
>>> sigcontext cleanups").
>>>
>>> Signed-off-by: Andy Lutomirski <luto@...nel.org>
>>
>> Now the strategy about SS is to always save it to the sigcontext.
>> This is good because the syscall can clobber it, so the app had
>> to be very careful in the past trying to save it by hands.
>> How about saving also fs and gs? (without restoring yet)
>> If you do, you'll save dosemu a headache of doing any "pre-syscall"
>> work. Pre-syscall work is very nasty.
>> I haven't checked if the syscall clobber also these or only SS,
>> but perhaps saving them by the kernel won't hurt?
> 
> There's a bunch of ongoing work about FS and GS.  I want to wait and see.
Andy, have you postponed only this, or also the sigreturn patch?
Long time no news...
sigreturn patch would really be nice to have.
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