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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@canonical.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 bcece91..fdaea52 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -314,6 +314,10 @@ 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? */
@@ -609,6 +613,8 @@ 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 ccb4136..5644b4b 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
--
1.7.2.3

--
Kees Cook
Ubuntu Security Team


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