[tip:x86/asm] x86/asm/entry/64: Simplify IRQ stack pt_regs handling

[tip-bot for Andy Lutomirski]

Commit-ID:  a586f98e9767fb0dfdb989002866b4024f00ce08
Gitweb:     http://git.kernel.org/tip/a586f98e9767fb0dfdb989002866b4024f00ce08
Author:     Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Fri, 3 Jul 2015 12:44:30 -0700
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Tue, 7 Jul 2015 10:59:08 +0200

x86/asm/entry/64: Simplify IRQ stack pt_regs handling

There's no need for both RSI and RDI to point to the original stack.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Denys Vlasenko <vda.linux@xxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: paulmck@xxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/3a0481f809dd340c7d3f54ce3fd6d66ef2a578cd.1435952415.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/entry/entry_64.S | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 65029f4..83eb63d 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -506,8 +506,6 @@ END(irq_entries_start)
 	SAVE_C_REGS
 	SAVE_EXTRA_REGS
 
-	movq	%rsp,%rdi	/* arg1 for \func (pointer to pt_regs) */
-
 	testb	$3, CS(%rsp)
 	jz	1f
 	SWAPGS
@@ -519,14 +517,14 @@ END(irq_entries_start)
 	 * a little cheaper to use a separate counter in the PDA (short of
 	 * moving irq_enter into assembly, which would be too much work)
 	 */
-	movq	%rsp, %rsi
+	movq	%rsp, %rdi
 	incl	PER_CPU_VAR(irq_count)
 	cmovzq	PER_CPU_VAR(irq_stack_ptr), %rsp
-	pushq	%rsi
+	pushq	%rdi
 	/* We entered an interrupt context - irqs are off: */
 	TRACE_IRQS_OFF
 
-	call	\func
+	call	\func	/* rdi points to pt_regs */
 	.endm
 
 	/*
--
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