linux-kernel - Re: [PATCH 2/2] x86: save user %rsp in pt

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Message-ID: <20150309161859.GA22871@gmail.com>
Date:	Mon, 9 Mar 2015 17:18:59 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: save user %rsp in pt_regs->sp on SYSCALL64
 fastpath


* Denys Vlasenko <dvlasenk@...hat.com> wrote:

> PER_CPU(old_rsp) usage is simplified - now it is used only
> as temp storage, and userspace stack pointer is immediately stored
> in pt_regs->sp on syscall entry, instead of being used later,
> on syscall exit.
> 
> All references of PER_CPU(old_rsp) in C code are gone -
> pt_regs->sp is used instead.
> 
> This also allows to get rid of thread_struct::usersp,
> which was needed only to set PER_CPU(old_rsp) for
> correct return from fork/clone.

Would it be possible to split this one into two parts as well:

  - Essential changes into the first one (old_rsp update 
    simplification, usersp usage conversion)

  - Removal of usersp, old_rsp extern declaration removal, comment 
    changes, in the second patch?

Thanks,

	Ingo
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