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[RFC/INCOMPLETE 11/13] x86/asm/entry/64: Simplify irq stack pt_regs handling

From Andy Lutomirski <luto@kernel.org>
Newsgroups linux.kernel
Subject [RFC/INCOMPLETE 11/13] x86/asm/entry/64: Simplify irq stack pt_regs handling
Date 2015-06-16 22:30 +0200
Message-ID <pC5EC-4Oe-21@gated-at.bofh.it> (permalink)
References <pC5uV-4CR-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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There's no need for both rsi and rdi to point to the original stack.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 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 43bf5762443c..ab8cbf602d19 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -505,8 +505,6 @@ 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
@@ -518,14 +516,14 @@ 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
 
 	/*
-- 
2.4.3

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[RFC/INCOMPLETE 00/13] x86: Rewrite exit-to-userspace code Andy Lutomirski <luto@kernel.org> - 2015-06-16 22:20 +0200
  [RFC/INCOMPLETE 10/13] x86/asm/entry/64: Save all regs on interrupt entry Andy Lutomirski <luto@kernel.org> - 2015-06-16 22:30 +0200
  [RFC/INCOMPLETE 09/13] x86/entry/compat: Migrate compat syscalls to new exit hooks Andy Lutomirski <luto@kernel.org> - 2015-06-16 22:30 +0200
  [RFC/INCOMPLETE 11/13] x86/asm/entry/64: Simplify irq stack pt_regs handling Andy Lutomirski <luto@kernel.org> - 2015-06-16 22:30 +0200

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