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

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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>
This commit is contained in:
Andy Lutomirski 2017-11-02 00:59:01 -07:00 • committed by Ingo Molnar
parent 8a055d7f41
commit e872045bfd
2 changed files with 27 additions and 6 deletions
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21
arch/x86/entry/calling.h
View file

@ -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

12
arch/x86/entry/entry_64.S
View file

@ -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)