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x86/asm/entry/32: Improve a TOP_OF_KERNEL_STACK_PADDING comment 

At Denys' request, clean up the comment describing stack padding
in the 32-bit sysenter path.

No code changes.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/41fee7bb8490ae840fe7ef2699f9c2feb932e729.1428002830.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Andy Lutomirski 2015-04-02 12:41:44 -07:00 committed by Ingo Molnar
parent d9dc64f30a
commit ff8287f363
1 changed files with 6 additions and 3 deletions
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9
arch/x86/kernel/entry_32.S
View File

@ -395,10 +395,13 @@ sysenter_past_esp:
/*CFI_REL_OFFSET cs, 0*/ /*CFI_REL_OFFSET cs, 0*/
/* /*
* Push current_thread_info()->sysenter_return to the stack. * Push current_thread_info()->sysenter_return to the stack.
* A tiny bit of offset fixup is necessary - 4*4 means the 4 words * A tiny bit of offset fixup is necessary: TI_sysenter_return
* pushed above; +8 corresponds to copy_thread's esp0 setting. * is relative to thread_info, which is at the bottom of the
* kernel stack page. 4*4 means the 4 words pushed above;
* TOP_OF_KERNEL_STACK_PADDING takes us to the top of the stack;
* and THREAD_SIZE takes us to the bottom.
*/ */
pushl_cfi ((TI_sysenter_return)-THREAD_SIZE+TOP_OF_KERNEL_STACK_PADDING+4*4)(%esp) pushl_cfi ((TI_sysenter_return) - THREAD_SIZE + TOP_OF_KERNEL_STACK_PADDING + 4*4)(%esp)
CFI_REL_OFFSET eip, 0 CFI_REL_OFFSET eip, 0
pushl_cfi %eax pushl_cfi %eax