linux-kernel - [PATCH v2] x86/entry_64.S: introduce prepare_error

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Date:	Sun, 17 Jan 2016 13:41:18 +0600
From:	Alexander Kuleshov <kuleshovmail@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Ingo Molnar <mingo@...hat.com>, "H . Peter Anvin" <hpa@...or.com>,
	x86@...nel.org, Andy Lutomirski <luto@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Borislav Petkov <bp@...e.de>, linux-kernel@...r.kernel.org,
	Alexander Kuleshov <kuleshovmail@...il.com>
Subject: [PATCH v2] x86/entry_64.S: introduce prepare_error_code macro

We need to put an error code to the %rsi if an exception provides
it, before the call of an exception handler. We do it in the idtentry
macro in two places.

This patch introduces prepare_error_code macro which will check existence
of an error code and put it to %rsi from ORIG_RAX if it exists, or just
clears %esi if an error code does not exist to prevent code duplication
in the idtentry macro.

Signed-off-by: Alexander Kuleshov <kuleshovmail@...il.com>
---

v2: indentation fixed

 arch/x86/entry/entry_64.S | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 9d34d3c..e2b1e79 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -722,6 +722,15 @@ apicinterrupt IRQ_WORK_VECTOR			irq_work_interrupt		smp_irq_work_interrupt
  */
 #define CPU_TSS_IST(x) PER_CPU_VAR(cpu_tss) + (TSS_ist + ((x) - 1) * 8)
 
+	.macro prepare_error_code has_error_code:req
+	.if \has_error_code
+	movq	ORIG_RAX(%rsp), %rsi		/* get error code */
+	movq	$-1, ORIG_RAX(%rsp)		/* no syscall to restart */
+	.else
+	xorl	%esi, %esi			/* no error code */
+	.endif
+	.endm
+
 .macro idtentry sym do_sym has_error_code:req paranoid=0 shift_ist=-1
 ENTRY(\sym)
 	/* Sanity check */
@@ -759,12 +768,7 @@ ENTRY(\sym)
 
 	movq	%rsp, %rdi			/* pt_regs pointer */
 
-	.if \has_error_code
-	movq	ORIG_RAX(%rsp), %rsi		/* get error code */
-	movq	$-1, ORIG_RAX(%rsp)		/* no syscall to restart */
-	.else
-	xorl	%esi, %esi			/* no error code */
-	.endif
+	prepare_error_code \has_error_code      /* %rsi -> error code */
 
 	.if \shift_ist != -1
 	subq	$EXCEPTION_STKSZ, CPU_TSS_IST(\shift_ist)
@@ -799,13 +803,7 @@ ENTRY(\sym)
 
 	movq	%rsp, %rdi			/* pt_regs pointer */
 
-	.if \has_error_code
-	movq	ORIG_RAX(%rsp), %rsi		/* get error code */
-	movq	$-1, ORIG_RAX(%rsp)		/* no syscall to restart */
-	.else
-	xorl	%esi, %esi			/* no error code */
-	.endif
-
+	prepare_error_code \has_error_code      /* %rsi -> error code */
 	call	\do_sym
 
 	jmp	error_exit			/* %ebx: no swapgs flag */
-- 
2.7.0.25.gfc10eb5