[mirror_ubuntu-eoan-kernel.git] / arch / x86 / lib / cmpxchg16b_emu.S

/* SPDX-License-Identifier: GPL-2.0-only */
#include <linux/linkage.h>
#include <asm/percpu.h>

.text

/*
 * 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
 * %al  : Operation successful
 */
ENTRY(this_cpu_cmpxchg16b_emu)

#
# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not
# via the ZF.  Caller will access %al to get result.
#
# Note that this is only useful for a cpuops operation.  Meaning that we
# do *not* have a fully atomic operation but just an operation that is
# *atomic* on a single cpu (as provided by the this_cpu_xx class of
# macros).
#
	pushfq
	cli

	cmpq PER_CPU_VAR((%rsi)), %rax
	jne .Lnot_same
	cmpq PER_CPU_VAR(8(%rsi)), %rdx
	jne .Lnot_same

	movq %rbx, PER_CPU_VAR((%rsi))
	movq %rcx, PER_CPU_VAR(8(%rsi))

	popfq
	mov $1, %al
	ret

.Lnot_same:
	popfq
	xor %al,%al
	ret

ENDPROC(this_cpu_cmpxchg16b_emu)
Commit	Line	Data
b886d83c	1	/* SPDX-License-Identifier: GPL-2.0-only */
b9ec40af	2	#include <linux/linkage.h>
3f635721	3	#include <asm/percpu.h>
d7c3f8ce	4
b9ec40af CL	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	ENTRY(this_cpu_cmpxchg16b_emu)
b9ec40af CL	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	#
131484c8	27	pushfq
b9ec40af CL	28	cli
b9ec40af CL	29
3f635721 JB	30	cmpq PER_CPU_VAR((%rsi)), %rax
	31	jne .Lnot_same
	32	cmpq PER_CPU_VAR(8(%rsi)), %rdx
	33	jne .Lnot_same
b9ec40af	34
3f635721 JB	35	movq %rbx, PER_CPU_VAR((%rsi))
3f635721 JB	36	movq %rcx, PER_CPU_VAR(8(%rsi))
b9ec40af	37
131484c8	38	popfq
b9ec40af CL	39	mov $1, %al
	40	ret
	41
3f635721	42	.Lnot_same:
131484c8	43	popfq
b9ec40af CL	44	xor %al,%al
	45	ret
	46
b9ec40af	47	ENDPROC(this_cpu_cmpxchg16b_emu)