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/* SPDX-License-Identifier: GPL-2.0-only */
#include <linux/linkage.h>
#include <asm/percpu.h>
#include <asm/processor-flags.h>
.text
/*
* Emulate 'cmpxchg16b %gs:(%rsi)'
*
* Inputs:
* %rsi : memory location to compare
* %rax : low 64 bits of old value
* %rdx : high 64 bits of old value
* %rbx : low 64 bits of new value
* %rcx : high 64 bits of new value
*
* Notably this is not LOCK prefixed and is not safe against NMIs
*/
SYM_FUNC_START(this_cpu_cmpxchg16b_emu)
pushfq
cli
/* if (*ptr == old) */
cmpq PER_CPU_VAR(0(%rsi)), %rax
jne .Lnot_same
cmpq PER_CPU_VAR(8(%rsi)), %rdx
jne .Lnot_same
/* *ptr = new */
movq %rbx, PER_CPU_VAR(0(%rsi))
movq %rcx, PER_CPU_VAR(8(%rsi))
/* set ZF in EFLAGS to indicate success */
orl $X86_EFLAGS_ZF, (%rsp)
popfq
RET
.Lnot_same:
/* *ptr != old */
/* old = *ptr */
movq PER_CPU_VAR(0(%rsi)), %rax
movq PER_CPU_VAR(8(%rsi)), %rdx
/* clear ZF in EFLAGS to indicate failure */
andl $(~X86_EFLAGS_ZF), (%rsp)
popfq
RET
SYM_FUNC_END(this_cpu_cmpxchg16b_emu)
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