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@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: paulmck@linux.vnet.ibm.com
Link: http://lkml.kernel.org/r/3a0481f809dd340c7d3f54ce3fd6d66ef2a578cd.1435952415.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index 65029f4..83eb63d 100644 (file)
--- 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
 
        /*