1/* 2 * This program is free software; you can redistribute it and/or 3 * modify it under the terms of the GNU General Public License 4 * as published by the Free Software Foundation; version 2 5 * of the License. 6 * 7 */ 8#include <linux/linkage.h> 9#include <asm/percpu.h> 10 11.text 12 13/* 14 * Inputs: 15 * %rsi : memory location to compare 16 * %rax : low 64 bits of old value 17 * %rdx : high 64 bits of old value 18 * %rbx : low 64 bits of new value 19 * %rcx : high 64 bits of new value 20 * %al : Operation successful 21 */ 22ENTRY(this_cpu_cmpxchg16b_emu) 23 24# 25# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not 26# via the ZF. Caller will access %al to get result. 27# 28# Note that this is only useful for a cpuops operation. Meaning that we 29# do *not* have a fully atomic operation but just an operation that is 30# *atomic* on a single cpu (as provided by the this_cpu_xx class of 31# macros). 32# 33 pushfq 34 cli 35 36 cmpq PER_CPU_VAR((%rsi)), %rax 37 jne .Lnot_same 38 cmpq PER_CPU_VAR(8(%rsi)), %rdx 39 jne .Lnot_same 40 41 movq %rbx, PER_CPU_VAR((%rsi)) 42 movq %rcx, PER_CPU_VAR(8(%rsi)) 43 44 popfq 45 mov $1, %al 46 ret 47 48.Lnot_same: 49 popfq 50 xor %al,%al 51 ret 52 53ENDPROC(this_cpu_cmpxchg16b_emu) 54