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>

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 4db7c4d12ffacb0ac5bdfe8d26c2ee1c181e52fc..59af275b37a28576dbb350ef92009866c7edc267 100644 (file)
--- 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)