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Date: Mon, 13 Mar 2017 08:53:37 -0700
From: Thomas Garnier <thgarnie@...gle.com>
To: Ingo Molnar <mingo@...nel.org>
Cc: Martin Schwidefsky <schwidefsky@...ibm.com>, Heiko Carstens <heiko.carstens@...ibm.com>, 
	David Howells <dhowells@...hat.com>, Arnd Bergmann <arnd@...db.de>, Al Viro <viro@...iv.linux.org.uk>, 
	Dave Hansen <dave.hansen@...el.com>, René Nyffenegger <mail@...enyffenegger.ch>, 
	Andrew Morton <akpm@...ux-foundation.org>, Kees Cook <keescook@...omium.org>, 
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>, Andy Lutomirski <luto@...nel.org>, 
	Ard Biesheuvel <ard.biesheuvel@...aro.org>, Nicolas Pitre <nicolas.pitre@...aro.org>, 
	Petr Mladek <pmladek@...e.com>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>, Helge Deller <deller@....de>, 
	Rik van Riel <riel@...hat.com>, John Stultz <john.stultz@...aro.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Oleg Nesterov <oleg@...hat.com>, 
	Stephen Smalley <sds@...ho.nsa.gov>, Pavel Tikhomirov <ptikhomirov@...tuozzo.com>, 
	Frederic Weisbecker <fweisbec@...il.com>, Stanislav Kinsburskiy <skinsbursky@...tuozzo.com>, 
	Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Dmitry Safonov <dsafonov@...tuozzo.com>, Borislav Petkov <bp@...en8.de>, 
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	He Chen <he.chen@...ux.intel.com>, Russell King <linux@...linux.org.uk>, 
	Vladimir Murzin <vladimir.murzin@....com>, Will Deacon <will.deacon@....com>, 
	Catalin Marinas <catalin.marinas@....com>, Mark Rutland <mark.rutland@....com>, 
	James Morse <james.morse@....com>, "David A . Long" <dave.long@...aro.org>, 
	Pratyush Anand <panand@...hat.com>, Laura Abbott <labbott@...hat.com>, 
	Andre Przywara <andre.przywara@....com>, Chris Metcalf <cmetcalf@...lanox.com>, 
	linux-s390 <linux-s390@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Linux API <linux-api@...r.kernel.org>, "the arch/x86 maintainers" <x86@...nel.org>, 
	linux-arm-kernel@...ts.infradead.org, 
	Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v3 2/4] x86/syscalls: Specific usage of verify_pre_usermode_state

On Sat, Mar 11, 2017 at 1:42 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> Ugh, so you call an assembly function just to ... call another function.
>

The verify_pre_usermode_state function is the architecture independent
checker. By default it is added on each syscall handler so calling it
here save code size.

> Plus why is it in assembly to begin with? Is this some older code that got
> written when the x86 entry code was in assembly, and never properly
> converted to C?

I wrote the assembly to make it faster and save a call on each syscall
return. I can just call verify_pre_usermode_state if you prefer.

-- 
Thomas

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