1/* SPDX-License-Identifier: GPL-2.0-only */ 2#include <linux/linkage.h> 3#include <asm/percpu.h> 4 5.text 6 7/* 8 * Inputs: 9 * %rsi : memory location to compare 10 * %rax : low 64 bits of old value 11 * %rdx : high 64 bits of old value 12 * %rbx : low 64 bits of new value 13 * %rcx : high 64 bits of new value 14 * %al : Operation successful 15 */ 16SYM_FUNC_START(this_cpu_cmpxchg16b_emu) 17 18# 19# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not 20# via the ZF. Caller will access %al to get result. 21# 22# Note that this is only useful for a cpuops operation. Meaning that we 23# do *not* have a fully atomic operation but just an operation that is 24# *atomic* on a single cpu (as provided by the this_cpu_xx class of 25# macros). 26# 27 pushfq 28 cli 29 30 cmpq PER_CPU_VAR((%rsi)), %rax 31 jne .Lnot_same 32 cmpq PER_CPU_VAR(8(%rsi)), %rdx 33 jne .Lnot_same 34 35 movq %rbx, PER_CPU_VAR((%rsi)) 36 movq %rcx, PER_CPU_VAR(8(%rsi)) 37 38 popfq 39 mov $1, %al 40 ret 41 42.Lnot_same: 43 popfq 44 xor %al,%al 45 ret 46 47SYM_FUNC_END(this_cpu_cmpxchg16b_emu) 48