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Commit e872045b authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Ingo Molnar
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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: default avatarAndy 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: default avatarIngo Molnar <mingo@kernel.org>
parent 8a055d7f

arch/x86/entry/calling.h

+21 −0
Original line number Original line Diff line number Diff line
@@ -151,6 +151,27 @@ For 32-bit we have the following conventions - kernel is built with 
	UNWIND_HINT_REGS offset=\offset extra=0

	UNWIND_HINT_REGS offset=\offset extra=0

	.endm

	.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

	.macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1

	.if \rstor_r11

	.if \rstor_r11

	movq 6*8(%rsp), %r11

	movq 6*8(%rsp), %r11

arch/x86/entry/entry_64.S

+6 −6
Original line number Original line Diff line number Diff line
@@ -618,9 +618,9 @@ GLOBAL(swapgs_restore_regs_and_return_to_usermode) 
1:

1:

#endif

#endif

	SWAPGS

	SWAPGS

	RESTORE_EXTRA_REGS

	POP_EXTRA_REGS

	RESTORE_C_REGS

	POP_C_REGS

	REMOVE_PT_GPREGS_FROM_STACK 8

	addq	$8, %rsp	/* skip regs->orig_ax */

	INTERRUPT_RETURN

	INTERRUPT_RETURN
@@ -650,9 +650,9 @@ GLOBAL(restore_regs_and_return_to_kernel) 
	ud2

	ud2

1:

1:

#endif

#endif

	RESTORE_EXTRA_REGS

	POP_EXTRA_REGS

	RESTORE_C_REGS

	POP_C_REGS

	REMOVE_PT_GPREGS_FROM_STACK 8

	addq	$8, %rsp	/* skip regs->orig_ax */

	INTERRUPT_RETURN

	INTERRUPT_RETURN





ENTRY(native_iret)

ENTRY(native_iret)