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/alternative-asm.h> 10#include <asm/frame.h> 11#include <asm/dwarf2.h> 12 13#ifdef CONFIG_SMP 14#define SEG_PREFIX %gs: 15#else 16#define SEG_PREFIX 17#endif 18 19.text 20 21/* 22 * Inputs: 23 * %rsi : memory location to compare 24 * %rax : low 64 bits of old value 25 * %rdx : high 64 bits of old value 26 * %rbx : low 64 bits of new value 27 * %rcx : high 64 bits of new value 28 * %al : Operation successful 29 */ 30ENTRY(this_cpu_cmpxchg16b_emu) 31CFI_STARTPROC 32 33# 34# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not 35# via the ZF. Caller will access %al to get result. 36# 37# Note that this is only useful for a cpuops operation. Meaning that we 38# do *not* have a fully atomic operation but just an operation that is 39# *atomic* on a single cpu (as provided by the this_cpu_xx class of 40# macros). 41# 42this_cpu_cmpxchg16b_emu: 43 pushf 44 cli 45 46 cmpq SEG_PREFIX(%rsi), %rax 47 jne not_same 48 cmpq SEG_PREFIX 8(%rsi), %rdx 49 jne not_same 50 51 movq %rbx, SEG_PREFIX(%rsi) 52 movq %rcx, SEG_PREFIX 8(%rsi) 53 54 popf 55 mov $1, %al 56 ret 57 58 not_same: 59 popf 60 xor %al,%al 61 ret 62 63CFI_ENDPROC 64 65ENDPROC(this_cpu_cmpxchg16b_emu) 66