linux-kernel - [PATCH 2/5] x86/asm/entry/64: simplify retint_kernel label usage, make retint_restore

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Message-Id: <1427738975-7391-3-git-send-email-dvlasenk@redhat.com>
Date:	Mon, 30 Mar 2015 20:09:32 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...capital.net>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 2/5] x86/asm/entry/64: simplify retint_kernel label usage, make retint_restore_args label local

Get rid of #define obfuscation of retint_kernel in CONFIG_PREEMPT case
by defining retint_kernel label always, not only for CONFIG_PREEMPT.

Strip retint_kernel of .global-ness (ENTRY macro) - it has no users
outside of this file.

This looks like cosmetics, but it is not:
"je LABEL" can be optimized to short jump by assember
only if LABEL is not global, for global labels jump is always
a near one with relocation.

Convert retint_restore_args to a local numeric label, making it clearer
that it is not used elsewhere in the file.

Signed-off-by: Denys Vlasenko <dvlasenk@...hat.com>
CC: Linus Torvalds <torvalds@...ux-foundation.org>
CC: Steven Rostedt <rostedt@...dmis.org>
CC: Ingo Molnar <mingo@...nel.org>
CC: Borislav Petkov <bp@...en8.de>
CC: "H. Peter Anvin" <hpa@...or.com>
CC: Andy Lutomirski <luto@...capital.net>
CC: Oleg Nesterov <oleg@...hat.com>
CC: Frederic Weisbecker <fweisbec@...il.com>
CC: Alexei Starovoitov <ast@...mgrid.com>
CC: Will Drewry <wad@...omium.org>
CC: Kees Cook <keescook@...omium.org>
CC: x86@...nel.org
CC: linux-kernel@...r.kernel.org
---
 arch/x86/kernel/entry_64.S | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 34d60c3..4d723ed 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -57,10 +57,6 @@
 	.section .entry.text, "ax"
 
 
-#ifndef CONFIG_PREEMPT
-#define retint_kernel retint_restore_args
-#endif
-
 #ifdef CONFIG_PARAVIRT
 ENTRY(native_usergs_sysret64)
 	swapgs
@@ -741,18 +737,18 @@ opportunistic_sysret_failed:
 	jmp restore_args
 
 /* Returning to kernel space */
+retint_kernel:
 #ifdef CONFIG_PREEMPT
 	/* Interrupts are off */
 	/* Check if we need preemption */
-ENTRY(retint_kernel)
 	cmpl	$0,PER_CPU_VAR(__preempt_count)
-	jnz	retint_restore_args
+	jnz	1f
 	bt	$9,EFLAGS(%rsp)	/* interrupts were off? */
-	jnc	retint_restore_args
+	jnc	1f
 	call	preempt_schedule_irq
 	jmp	exit_intr
+1:
 #endif
-retint_restore_args:
 	DISABLE_INTERRUPTS(CLBR_ANY)
 	/*
 	 * The iretq could re-enable interrupts:
-- 
1.8.1.4

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