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 */ 16 SYM_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 47 SYM_FUNC_END(this_cpu_cmpxchg16b_emu) 48