brgerst at gmail
Nov 25, 2009, 8:17 AM
Post #1 of 2
(115 views)
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[PATCH] x86, 64-bit: Set data segments to null after switching to 64-bit mode
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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 [at] gmail>
---
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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