1/* SPDX-License-Identifier: GPL-2.0-only */
 
 
 
 
 
 
 2#include <linux/linkage.h>
 3#include <asm/percpu.h>
 4#include <asm/processor-flags.h>
 
 
 
 
 
 
 
 5
 6.text
 7
 8/*
 9 * Emulate 'cmpxchg16b %gs:(%rsi)'
10 *
11 * Inputs:
12 * %rsi : memory location to compare
13 * %rax : low 64 bits of old value
14 * %rdx : high 64 bits of old value
15 * %rbx : low 64 bits of new value
16 * %rcx : high 64 bits of new value
17 *
18 * Notably this is not LOCK prefixed and is not safe against NMIs
19 */
20SYM_FUNC_START(this_cpu_cmpxchg16b_emu)
 
21
22	pushfq
 
 
 
 
 
 
 
 
 
 
23	cli
24
25	/* if (*ptr == old) */
26	cmpq	PER_CPU_VAR(0(%rsi)), %rax
27	jne	.Lnot_same
28	cmpq	PER_CPU_VAR(8(%rsi)), %rdx
29	jne	.Lnot_same
30
31	/* *ptr = new */
32	movq	%rbx, PER_CPU_VAR(0(%rsi))
33	movq	%rcx, PER_CPU_VAR(8(%rsi))
34
35	/* set ZF in EFLAGS to indicate success */
36	orl	$X86_EFLAGS_ZF, (%rsp)
37
38	popfq
39	RET
40
41.Lnot_same:
42	/* *ptr != old */
43
44	/* old = *ptr */
45	movq	PER_CPU_VAR(0(%rsi)), %rax
46	movq	PER_CPU_VAR(8(%rsi)), %rdx
47
48	/* clear ZF in EFLAGS to indicate failure */
49	andl	$(~X86_EFLAGS_ZF), (%rsp)
50
51	popfq
52	RET
53
54SYM_FUNC_END(this_cpu_cmpxchg16b_emu)

 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)