x86/entry/64: Simplify reg restore code in the standard IRET paths

commit e872045bfd9c465a8555bab4b8567d56a4d2d3bb upstream.

The old code restored all the registers with movq instead of pop.

In theory, this was done because some CPUs have higher movq
throughput, but any gain there would be tiny and is almost certainly
outweighed by the higher text size.

This saves 96 bytes of text.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/ad82520a207ccd851b04ba613f4f752b33ac05f7.1509609304.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 6e160031cfea1d3afd65880f0b6477cc5ff8115e..67d1df061d1abcbda87e7610e3e781f461a8ca57 100644 (file)
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -152,6 +152,27 @@ For 32-bit we have the following conventions - kernel is built with
        UNWIND_HINT_REGS offset=\offset extra=0
        .endm
 
+       .macro POP_EXTRA_REGS
+       popq %r15
+       popq %r14
+       popq %r13
+       popq %r12
+       popq %rbp
+       popq %rbx
+       .endm
+
+       .macro POP_C_REGS
+       popq %r11
+       popq %r10
+       popq %r9
+       popq %r8
+       popq %rax
+       popq %rcx
+       popq %rdx
+       popq %rsi
+       popq %rdi
+       .endm
+
        .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
        .if \rstor_r11
        movq 6*8(%rsp), %r11

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f67ac2647dbf548667290f7d6dbf96b8265fa7ae..77a67ed991fc50c6e177153947654e7e9f574ff0 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -619,9 +619,9 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode)
 1:
 #endif
        SWAPGS
-       RESTORE_EXTRA_REGS
-       RESTORE_C_REGS
-       REMOVE_PT_GPREGS_FROM_STACK 8
+       POP_EXTRA_REGS
+       POP_C_REGS
+       addq    $8, %rsp        /* skip regs->orig_ax */
        INTERRUPT_RETURN
 
 
@@ -651,9 +651,9 @@ GLOBAL(restore_regs_and_return_to_kernel)
        ud2
 1:
 #endif
-       RESTORE_EXTRA_REGS
-       RESTORE_C_REGS
-       REMOVE_PT_GPREGS_FROM_STACK 8
+       POP_EXTRA_REGS
+       POP_C_REGS
+       addq    $8, %rsp        /* skip regs->orig_ax */
        INTERRUPT_RETURN
 
 ENTRY(native_iret)