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

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>

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 640aafebdc00e460687a796f5011c1ab917a4ab9..0b9dd8123701a91bbb004419f09b52297328559c 100644 (file)
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -151,6 +151,27 @@ 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 d6ffdc9afcbb67dd49deb0c6284482e8a609296b..925d56246071723b36cadf68a77e022fb325b63f 100644 (file)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -618,9 +618,9 @@ 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
 
 
@@ -650,9 +650,9 @@ 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)