linux-kernel - [PATCH 1/3] move retint_kernel code block closer to its user

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Date:	Mon, 30 Mar 2015 14:26:33 +0200
From:	Denys Vlasenko <dvlasenk@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Denys Vlasenko <dvlasenk@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>, 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 1/3] move retint_kernel code block closer to its user

"retint_kernel" code block is misplaced. Since its logical continuation
is "retint_restore_args", it is more natural to place it above that label.
This also makes two jumps "short".

This change only moves code block around, without changing logic.

This enables the next simplification: making "retint_restore_args"
label a local numeric one.

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 | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 750c6ef..98edd7d 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -739,7 +739,19 @@ opportunistic_sysret_failed:
 	SWAPGS
 	jmp restore_args
 
-retint_restore_args:	/* return to kernel space */
+/* Returning to kernel space */
+#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
+	bt	$9,EFLAGS(%rsp)	/* interrupts were off? */
+	jnc	retint_restore_args
+	call	preempt_schedule_irq
+	jmp	exit_intr
+#endif
+retint_restore_args:
 	DISABLE_INTERRUPTS(CLBR_ANY)
 	/*
 	 * The iretq could re-enable interrupts:
@@ -829,17 +841,6 @@ retint_signal:
 	GET_THREAD_INFO(%rcx)
 	jmp retint_with_reschedule
 
-#ifdef CONFIG_PREEMPT
-	/* Returning to kernel space. Check if we need preemption */
-	/* rcx:	 threadinfo. interrupts off. */
-ENTRY(retint_kernel)
-	cmpl $0,PER_CPU_VAR(__preempt_count)
-	jnz  retint_restore_args
-	bt   $9,EFLAGS(%rsp)	/* interrupts off? */
-	jnc  retint_restore_args
-	call preempt_schedule_irq
-	jmp exit_intr
-#endif
 	CFI_ENDPROC
 END(common_interrupt)
 
-- 
1.8.1.4

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