linux-kernel - Re: [regression] x86/signal/64: Fix SS handling for signals delivered to 64-bit programs breaks dosemu

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Message-ID: <55CD1494.1070108@list.ru>
Date:	Fri, 14 Aug 2015 01:05:08 +0300
From:	Stas Sergeev <stsp@...t.ru>
To:	Raymond Jennings <shentino@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	Linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [regression] x86/signal/64: Fix SS handling for signals delivered
 to 64-bit programs breaks dosemu

14.08.2015 01:01, Raymond Jennings пишет:
>
>
> On 08/13/15 14:46, Linus Torvalds wrote:
>> On Thu, Aug 13, 2015 at 2:42 PM, Raymond Jennings 
>> <shentino@...il.com> wrote:
>>> I am curious about what's supposed to happen normally on signal 
>>> delivery.
>>>
>>> Is SS a register that's supposed to be preserved like EIP/RIP and CS 
>>> when a
>>> signal is delivered?
>> What exactly does "supposed" mean?
> Basically, when a process/thread receives a signal, what happens to 
> its registers?
>> So clearly, we're not "supposed" to save/restore it. Because reality
>> matters a hell of a lot more than any theoretical arguments.
> So it still counts as a regression if the kernel pulls the rug out 
> from under someone that was relying on undocumented or buggy behavior?
>
You probably want to read the whole thread...
Or start from here:
https://lkml.org/lkml/2015/8/12/800
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