linux-kernel - Re: [PATCH 4/4] x86: entry_64.S: remove unused thread

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Message-ID: <55005D05.6010606@redhat.com>
Date:	Wed, 11 Mar 2015 16:19:33 +0100
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	"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 4/4] x86: entry_64.S: remove unused thread_struct::usersp

On 03/11/2015 01:55 PM, Borislav Petkov wrote:
> On Tue, Mar 10, 2015 at 11:45:07AM +0100, Denys Vlasenko wrote:
>> @@ -894,11 +893,6 @@ extern unsigned long thread_saved_pc(struct task_struct *tsk);
>>  #define task_pt_regs(tsk)	((struct pt_regs *)(tsk)->thread.sp0 - 1)
>>  extern unsigned long KSTK_ESP(struct task_struct *task);
>>  
>> -/*
>> - * User space RSP while inside the SYSCALL fast path
>> - */
>> -DECLARE_PER_CPU(unsigned long, old_rsp);
> 
> Please grep the whole arch/x86/ tree for old_rsp as there are more
> leftovers.

I think I did:

$ grep -r old_rsp arch/x86
arch/x86/xen/xen-asm_64.S:	movq %rsp, PER_CPU_VAR(old_rsp)
arch/x86/xen/xen-asm_64.S:	pushq PER_CPU_VAR(old_rsp)
arch/x86/xen/xen-asm_64.S:	movq %rsp, PER_CPU_VAR(old_rsp)
arch/x86/xen/xen-asm_64.S:	pushq PER_CPU_VAR(old_rsp)
arch/x86/kernel/process_64.c:__visible DEFINE_PER_CPU(unsigned long, old_rsp);
arch/x86/kernel/entry_64.S:	movq	%rsp,PER_CPU_VAR(old_rsp)
arch/x86/kernel/entry_64.S:	movq	PER_CPU_VAR(old_rsp),%rcx
arch/x86/kernel/entry_64.S:	/* 0(%rsp): old_rsp */

The only remaining use in C code is the definition in process_64.c
It is necessary for assembly (.S) files.
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