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authorBrian Gerst <brgerst@gmail.com>2009-11-25 11:17:36 -0500
committerIngo Molnar <mingo@elte.hu>2009-11-26 10:44:30 +0100
commit8ec6993d9f7d961014af970ded57542961fe9ad9 (patch)
tree62f5eb8402c4cdda753161541f8106c29953d325 /arch
parent64b028b22616946a05bf9580f7f7f7ee2ac070b4 (diff)
x86, 64-bit: Set data segments to null after switching to 64-bit mode
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@gmail.com> Cc: Tim Blechmann <tim@klingt.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jeremy Fitzhardinge <jeremy@goop.org> Cc: Jan Beulich <JBeulich@novell.com> LKML-Reference: <1259165856-3512-1-git-send-email-brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/head_64.S4
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 26406601031c..17ba9ecf27c5 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