linux-kernel - Re: [PATCH 4/5] x86/asm/entry/32: Replace RESTORE_RSI_RDI[

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Date:	Sun, 14 Jun 2015 10:40:59 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Denys Vlasenko <dvlasenk@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	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 4/5] x86/asm/entry/32: Replace RESTORE_RSI_RDI[_RDX] with
 open-coded 32-bit reads


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

> 	+8b 74 24 68            mov    0x68(%rsp),%esi
> 	+8b 7c 24 70            mov    0x70(%rsp),%edi
> 	+8b 54 24 60            mov    0x60(%rsp),%edx

Btw., could you (in another patch) order the restoration properly, by pt_regs 
memory order, where possible?

So this:

> +	movl	RSI(%rsp), %esi
> +	movl	RDI(%rsp), %edi
> +	movl	RDX(%rsp), %edx
>  	movl	RIP(%rsp), %ecx
>  	movl	EFLAGS(%rsp), %r11d

would become:

	movl	RDX(%rsp), %edx
	movl	RSI(%rsp), %esi
	movl	RDI(%rsp), %edi
	movl	RIP(%rsp), %ecx
 	movl	EFLAGS(%rsp), %r11d

... or so.

In fact I'd suggest we structure movl based restoration precisely after the field 
order in the structure, and comment on cases where we depart from what's in 
pt_regs - to make it all easier to verify.

Thanks,

	Ingo
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