linux-kernel - Re: [PATCH] [Cleanup] x86: signal: unify the sigaltstack check with other arches

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Date:	Thu, 25 Feb 2016 09:25:25 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Stas Sergeev <stsp@...t.ru>
Cc:	linux-kernel@...r.kernel.org,
	Andy Lutomirski <luto@...capital.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Borislav Petkov <bp@...e.de>, Brian Gerst <brgerst@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Richard Weinberger <richard@....at>,
	Stas Sergeev <stsp@...rs.sourceforge.net>
Subject: Re: [PATCH] [Cleanup] x86: signal: unify the sigaltstack check with
 other arches


* Stas Sergeev <stsp@...t.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?

Thanks,

	Ingo