linux-kernel - [PATCH 3/4] x86: call verify_cpu during 32bit CPU startup

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Message-ID: <20100619055259.GU24749@outflux.net>
Date:	Fri, 18 Jun 2010 22:52:59 -0700
From:	Kees Cook <kees.cook@...onical.com>
To:	x86@...nel.org
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Alexander Potashev <aspotashev@...il.com>,
	Tim Abbott <tabbott@...lice.com>,
	Sam Ravnborg <sam@...nborg.org>,
	Jan Beulich <jbeulich@...ell.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/4] x86: call verify_cpu during 32bit CPU startup

The XD_DISABLE-clearing side-effect needs to happen on 32bit CPU
start-up as well.

Signed-off-by: Kees Cook <kees.cook@...onical.com>
---
 arch/x86/kernel/head_32.S    |    6 ++++++
 arch/x86/kernel/verify_cpu.S |    1 +
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index 37c3d4b..0dec923 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -309,6 +309,10 @@ ENTRY(startup_32_smp)
 	subl $0x80000001, %eax
 	cmpl $(0x8000ffff-0x80000001), %eax
 	ja 6f
+
+	/* Clear bogus XD_DISABLE bits */
+	call verify_cpu
+
 	mov $0x80000001, %eax
 	cpuid
 	/* Execute Disable bit supported? */
@@ -604,6 +608,8 @@ ignore_int:
 #endif
 	iret
 
+#include "verify_cpu.S"
+
 	__REFDATA
 .align 4
 ENTRY(initial_code)
diff --git a/arch/x86/kernel/verify_cpu.S b/arch/x86/kernel/verify_cpu.S
index d6a0be6..29a6357 100644
--- a/arch/x86/kernel/verify_cpu.S
+++ b/arch/x86/kernel/verify_cpu.S
@@ -19,6 +19,7 @@
  *
  *	arch/x86_64/boot/compressed/head_64.S: Boot cpu verification
  *	arch/x86_64/kernel/trampoline_64.S: secondary processor verfication
+ *	arch/x86_64/kernel/head_32.S: processor startup
  *
  *	verify_cpu, returns the status of longmode and SSE in register %eax.
  *		0: Success    1: Failure
-- 
1.7.1


-- 
Kees Cook
Ubuntu Security Team
--
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