[tip:x86/asm] x86-64, asm: Directly access per-cpu IST

[tip-bot for Brian Gerst <brgerst@gmail.com>]

Commit-ID:  c15a5958a0b6dbf06b3c05972694f04a0c50a4cf
Gitweb:     http://git.kernel.org/tip/c15a5958a0b6dbf06b3c05972694f04a0c50a4cf
Author:     Brian Gerst <brgerst@gmail.com>
AuthorDate: Sat, 31 Jul 2010 12:48:22 -0400
Committer:  H. Peter Anvin <hpa@zytor.com>
CommitDate: Sun, 1 Aug 2010 16:05:17 -0700

x86-64, asm: Directly access per-cpu IST

Use a direct per-cpu reference for the IST instead of using a scratch
register.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
LKML-Reference: <1280594903-6341-1-git-send-email-brgerst@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
 arch/x86/kernel/entry_64.S |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 4db7c4d..59af275 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1065,6 +1065,7 @@ ENTRY(\sym)
 END(\sym)
 .endm
 
+#define INIT_TSS_IST(x) PER_CPU_VAR(init_tss) + (TSS_ist + ((x) - 1) * 8)
 .macro paranoidzeroentry_ist sym do_sym ist
 ENTRY(\sym)
 	INTR_FRAME
@@ -1076,10 +1077,9 @@ ENTRY(\sym)
 	TRACE_IRQS_OFF
 	movq %rsp,%rdi		/* pt_regs pointer */
 	xorl %esi,%esi		/* no error code */
-	PER_CPU(init_tss, %r12)
-	subq $EXCEPTION_STKSZ, TSS_ist + (\ist - 1) * 8(%r12)
+	subq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist)
 	call \do_sym
-	addq $EXCEPTION_STKSZ, TSS_ist + (\ist - 1) * 8(%r12)
+	addq $EXCEPTION_STKSZ, INIT_TSS_IST(\ist)
 	jmp paranoid_exit	/* %ebx: no swapgs flag */
 	CFI_ENDPROC
 END(\sym)