linux-kernel - Re: [PATCH v4 08/17] x86/entry: Add enter_from_user

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Date:	Wed, 1 Jul 2015 12:24:10 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Andy Lutomirski <luto@...nel.org>
Cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Denys Vlasenko <vda.linux@...glemail.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>, paulmck@...ux.vnet.ibm.com
Subject: Re: [PATCH v4 08/17] x86/entry: Add enter_from_user_mode and use it
 in syscalls

On Mon, Jun 29, 2015 at 12:33:40PM -0700, Andy Lutomirski wrote:
> Changing the x86 context tracking hooks is dangerous because there
> are no good checks that we track our context correctly.  Add a
> helper to check that we're actually in CONTEXT_USER when we enter
> from user mode and wire it up for syscall entries.
> 
> Subsequent patches will wire this up for all non-NMI entries as
> well.  NMIs are their own special beast and cannot currently switch
> overall context tracking state.  Instead, they have their own
> special RCU hooks.
> 
> This is a tiny speedup if !CONFIG_CONTEXT_TRACKING (removes a
> branch) and a tiny slowdown if CONFIG_CONTEXT_TRACING (adds a layer

CONTEXT_TRACING?!

Oh noooo, not another tracer :-P

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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