Messages in this thread Patch in this message | | | Date | Thu, 2 Nov 2017 03:50:19 -0700 | From | tip-bot for Andy Lutomirski <> | Subject | [tip:x86/asm] x86/entry/64: Simplify reg restore code in the standard IRET paths |
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Commit-ID: e872045bfd9c465a8555bab4b8567d56a4d2d3bb Gitweb: https://git.kernel.org/tip/e872045bfd9c465a8555bab4b8567d56a4d2d3bb Author: Andy Lutomirski <luto@kernel.org> AuthorDate: Thu, 2 Nov 2017 00:59:01 -0700 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Thu, 2 Nov 2017 11:04:38 +0100
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> --- arch/x86/entry/calling.h | 21 +++++++++++++++++++++ arch/x86/entry/entry_64.S | 12 ++++++------ 2 files changed, 27 insertions(+), 6 deletions(-)
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 640aafe..0b9dd81 100644 --- 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 d6ffdc9..925d562 100644 --- 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)
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