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Subject: Re: [PATCH] [Cleanup] x86: signal: unify the sigaltstack check with
 other arches
To: Ingo Molnar <mingo@kernel.org>
References: <1456095685-23857-1-git-send-email-stsp@list.ru>
 <20160225082524.GA12294@gmail.com>
Cc: linux-kernel@vger.kernel.org, Andy Lutomirski <luto@amacapital.net>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        Borislav Petkov <bp@suse.de>, Brian Gerst <brgerst@gmail.com>,
        Oleg Nesterov <oleg@redhat.com>, Richard Weinberger <richard@nod.at>,
        Stas Sergeev <stsp@users.sourceforge.net>
From: Stas Sergeev <stsp@list.ru>
Message-ID: <56CEF02C.7050906@list.ru>
Date: Thu, 25 Feb 2016 15:14:36 +0300
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25.02.2016 11:25, Ingo Molnar пишет:
> 
> * Stas Sergeev <stsp@list.ru> wrote:
> 
>> Currently x86's get_sigframe() checks for "current->sas_ss_size"
>> to determine whether there is a need to switch to sigaltstack.
>> The common practice used by all other arches is to check for
>> sas_ss_flags(sp) == 0
>>
>> This patch makes the code consistent with other arches.
>> The slight complexity of the patch is added by the optimization on
>> !sigstack check that was requested by Andy Lutomirski: sas_ss_flags(sp)==0
>> already implies that we are not on a sigstack, so the code is shuffled
>> to avoid the duplicate checking.
> 
> So this changelog is missing an analysis about what effect this change will have 
> on applications. Can any type of user-space code see a change in behavior? If yes, 
> what will happen and is that effect desirable?
This is a clean-up, and as such, there is no visible effect.
If there is - it is a bug.
The purpose of this patch is only to unify the x86 code with
what all the other arches do. It was initially the part of the
rejected series, but now it is just a clean-up.