linux-kernel - [tip:x86/asm] x86/entry/64: Shorten TEST instructions

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Date:   Thu, 2 Nov 2017 05:48:47 -0700
From:   tip-bot for Borislav Petkov <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     mingo@...nel.org, torvalds@...ux-foundation.org, luto@...nel.org,
        tglx@...utronix.de, hpa@...or.com, peterz@...radead.org,
        brgerst@...il.com, dave.hansen@...el.com,
        linux-kernel@...r.kernel.org, bp@...e.de
Subject: [tip:x86/asm] x86/entry/64: Shorten TEST instructions

Commit-ID:  1e4c4f610f774df6088d7c065b2dd4d22adba698
Gitweb:     https://git.kernel.org/tip/1e4c4f610f774df6088d7c065b2dd4d22adba698
Author:     Borislav Petkov <bp@...e.de>
AuthorDate: Thu, 2 Nov 2017 13:09:26 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 2 Nov 2017 13:45:37 +0100

x86/entry/64: Shorten TEST instructions

Convert TESTL to TESTB and save 3 bytes per callsite.

No functionality change.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Dave Hansen <dave.hansen@...el.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/20171102120926.4srwerqrr7g72e2k@pd.tnic
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/entry/entry_64.S | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 40e9933..84263c7 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -620,7 +620,7 @@ GLOBAL(retint_user)
 GLOBAL(swapgs_restore_regs_and_return_to_usermode)
 #ifdef CONFIG_DEBUG_ENTRY
 	/* Assert that pt_regs indicates user mode. */
-	testl	$3, CS(%rsp)
+	testb	$3, CS(%rsp)
 	jnz	1f
 	ud2
 1:
@@ -653,7 +653,7 @@ retint_kernel:
 GLOBAL(restore_regs_and_return_to_kernel)
 #ifdef CONFIG_DEBUG_ENTRY
 	/* Assert that pt_regs indicates kernel mode. */
-	testl	$3, CS(%rsp)
+	testb	$3, CS(%rsp)
 	jz	1f
 	ud2
 1: