linux-kernel - [tip:x86/cleanups] x86, reloc: Use xorl instead of xorq in relocate_kernel

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Message-ID: <tip-b76zi1gep39c0zs8fbvkhie9@git.kernel.org>
Date:	Thu, 20 Jun 2013 21:33:32 -0700
From:	"tip-bot for H. Peter Anvin" <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	keescook@...omium.org, tglx@...utronix.de, hpa@...ux.intel.com
Subject: [tip:x86/cleanups] x86, reloc:
  Use xorl instead of xorq in relocate_kernel_64.S

Commit-ID:  f037e416afb38b9ee8ac598d68733fcbaf665384
Gitweb:     http://git.kernel.org/tip/f037e416afb38b9ee8ac598d68733fcbaf665384
Author:     H. Peter Anvin <hpa@...ux.intel.com>
AuthorDate: Thu, 20 Jun 2013 21:16:00 -0700
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
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@...ux.intel.com>
Cc: Kees Cook <keescook@...omium.org>
Link: http://lkml.kernel.org/n/tip-b76zi1gep39c0zs8fbvkhie9@git.kernel.org
---
 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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