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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@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>
This commit is contained in:
Brian Gerst 2009-11-25 11:17:36 -05:00 committed by Ingo Molnar
parent 64b028b226
commit 8ec6993d9f
1 changed files with 2 additions and 2 deletions
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4
arch/x86/kernel/head_64.S
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@ -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