[tip:x86/cleanups] x86, reloc: Use xorl instead of xorq in relocate_kernel_64.S

From: tip-bot for H. Peter Anvin
Date: Fri Jun 21 2013 - 00:33:58 EST


Commit-ID: f037e416afb38b9ee8ac598d68733fcbaf665384
Gitweb: http://git.kernel.org/tip/f037e416afb38b9ee8ac598d68733fcbaf665384
Author: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
AuthorDate: Thu, 20 Jun 2013 21:16:00 -0700
Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Thu, 20 Jun 2013 21:30:04 -0700

x86, reloc: Use xorl instead of xorq in relocate_kernel_64.S

There is no point in using "xorq" to clear a register... use "xorl" to
clear the bottom 32 bits, and the upper 32 bits get cleared by virtue
of zero extension.

Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Link: http://lkml.kernel.org/n/tip-b76zi1gep39c0zs8fbvkhie9@xxxxxxxxxxxxxx
---
arch/x86/kernel/relocate_kernel_64.S | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index f2bb9c9..3fd2c69 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -151,21 +151,21 @@ identity_mapped:

testq %r11, %r11
jnz 1f
- xorq %rax, %rax
- xorq %rbx, %rbx
- xorq %rcx, %rcx
- xorq %rdx, %rdx
- xorq %rsi, %rsi
- xorq %rdi, %rdi
- xorq %rbp, %rbp
- xorq %r8, %r8
- xorq %r9, %r9
- xorq %r10, %r10
- xorq %r11, %r11
- xorq %r12, %r12
- xorq %r13, %r13
- xorq %r14, %r14
- xorq %r15, %r15
+ xorl %eax, %eax
+ xorl %ebx, %ebx
+ xorl %ecx, %ecx
+ xorl %edx, %edx
+ xorl %esi, %esi
+ xorl %edi, %edi
+ xorl %ebp, %ebp
+ xorl %r8d, %r8d
+ xorl %r9d, %r9d
+ xorl %r10d, %r10d
+ xorl %r11d, %r11d
+ xorl %r12d, %r12d
+ xorl %r13d, %r13d
+ xorl %r14d, %r14d
+ xorl %r15d, %r15d

ret

@@ -212,8 +212,8 @@ virtual_mapped:
/* Do the copies */
swap_pages:
movq %rdi, %rcx /* Put the page_list in %rcx */
- xorq %rdi, %rdi
- xorq %rsi, %rsi
+ xorl %edi, %edi
+ xorl %esi, %esi
jmp 1f

0: /* top, read another word for the indirection page */
--
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