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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>,
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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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