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: <55CD13A0.8060403@gmail.com>
Date:	Thu, 13 Aug 2015 15:01:04 -0700
From:	Raymond Jennings <shentino@...il.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Cyrill Gorcunov <gorcunov@...il.com>,
	Andy Lutomirski <luto@...capital.net>,
	Pavel Emelyanov <xemul@...allels.com>,
	Stas Sergeev <stsp@...t.ru>,
	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



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?
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