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    Subject[tip:x86/asm] x86/asm/entry/64: Simplify IRQ stack pt_regs handling
    Commit-ID:  a586f98e9767fb0dfdb989002866b4024f00ce08
    Gitweb: http://git.kernel.org/tip/a586f98e9767fb0dfdb989002866b4024f00ce08
    Author: Andy Lutomirski <luto@kernel.org>
    AuthorDate: Fri, 3 Jul 2015 12:44:30 -0700
    Committer: Ingo Molnar <mingo@kernel.org>
    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@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>
    ---
    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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