From: Andi Kleen <andi@firstfloor.org>
To: Kees Cook <kees.cook@canonical.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] x86: clear XD_DISABLED flag on Intel to regain NX
Date: Wed, 10 Nov 2010 17:11:55 +0100 [thread overview]
Message-ID: <87hbfpp390.fsf@basil.nowhere.org> (raw)
In-Reply-To: <20101109181501.GG5876@outflux.net> (Kees Cook's message of "Tue, 9 Nov 2010 10:15:01 -0800")
Kees Cook <kees.cook@canonical.com> writes:
> +
> +verify_cpu_clear_xd:
> + movl $MSR_IA32_MISC_ENABLE, %ecx
> + rdmsr
> + btrl $2, %edx # clear MSR_IA32_MISC_ENABLE_XD_DISABLE
> + jnc verify_cpu_check # only write MSR if bit was
> changed
Strictly it's still a bit dangerous to read this MSR without knowing
about the CPU for sure. If you guess wrong you'll die here.
I would rather move this code later into the early init code (before the
second mapping is set up, which is still in time). There the exception
handlers are up and you could handle a #GP if it happens.
-Andi
--
ak@linux.intel.com -- Speaking for myself only.
next prev parent reply other threads:[~2010-11-10 16:12 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-09 18:11 [Security] [PATCH v3 0/4] x86: clear XD_DISABLED flag on Intel to regain NX Kees Cook
2010-11-09 18:14 ` [PATCH 1/4] x86: rename verify_cpu_64.S to verify_cpu.S Kees Cook
2010-11-09 18:46 ` Pekka Enberg
2010-11-09 19:00 ` Kees Cook
2010-11-09 19:59 ` Pekka Enberg
2010-11-09 19:02 ` Kees Cook
2010-11-09 19:11 ` Pekka Enberg
2010-11-09 18:15 ` [PATCH 2/4] x86: clear XD_DISABLED flag on Intel to regain NX Kees Cook
2010-11-10 16:11 ` Andi Kleen [this message]
2010-11-10 16:47 ` Kees Cook
2010-11-10 17:42 ` Andi Kleen
2010-11-10 18:15 ` Kees Cook
2010-11-09 18:15 ` [PATCH 3/4] x86: call verify_cpu during 32bit CPU startup Kees Cook
2010-11-09 19:09 ` Pekka Enberg
2010-11-09 19:19 ` Kees Cook
2010-11-09 19:46 ` Pekka Enberg
2010-11-09 19:56 ` Kees Cook
2010-11-09 20:28 ` Pekka Enberg
2010-11-09 20:48 ` Kees Cook
2010-11-09 20:50 ` Pekka Enberg
2010-11-09 18:15 ` [PATCH 4/4] x86: only CPU features determine NX capabilities Kees Cook
2010-11-09 18:31 ` [Security] [PATCH v3 0/4] x86: clear XD_DISABLED flag on Intel to regain NX Alan Cox
2010-11-09 18:56 ` Kees Cook
2010-11-09 22:50 ` Alan Cox
2010-11-09 23:53 ` Kees Cook
2010-11-10 0:21 ` Alan Cox
2010-11-10 0:43 ` Kees Cook
2010-11-10 1:10 ` Kees Cook
2010-11-10 11:11 ` Alan Cox
2010-11-10 11:15 ` Ingo Molnar
2010-11-11 15:15 ` Rogier Wolff
-- strict thread matches above, loose matches on Subject: below --
2010-11-10 18:35 [Security] [PATCH v5 " Kees Cook
2010-11-10 18:35 ` [PATCH 2/4] " Kees Cook
2010-11-09 22:17 [Security] [PATCH v4 0/4] " Kees Cook
2010-11-09 22:18 ` [PATCH 2/4] " Kees Cook
2010-06-19 5:50 [PATCH v2 0/4] " Kees Cook
2010-06-19 5:52 ` [PATCH 2/4] " Kees Cook
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