[PATCH] x86, 64-bit: Set data segments to null after switching to 64-bit mode

[Brian Gerst]

This prevents kernel threads from inheriting non-null segment selectors,
and causing optimizations in __switch_to() to be ineffective.

Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
---
 arch/x86/kernel/head_64.S |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 780cd92..22db86a 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -212,8 +212,8 @@ ENTRY(secondary_startup_64)
 	 */
 	lgdt	early_gdt_descr(%rip)
 
-	/* set up data segments. actually 0 would do too */
-	movl $__KERNEL_DS,%eax
+	/* set up data segments */
+	xorl %eax,%eax
 	movl %eax,%ds
 	movl %eax,%ss
 	movl %eax,%es
-- 
1.6.5.2

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