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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/x86/lib/cmpxchg8b_emu.S
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/* SPDX-License-Identifier: GPL-2.0-only */

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#include <linux/export.h>

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#include <linux/linkage.h>

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#include <asm/percpu.h>

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#include <asm/processor-flags.h>

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.text

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#ifndef CONFIG_X86_CX8

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/*

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 * Emulate 'cmpxchg8b (%esi)' on UP

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 *

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 * Inputs:

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 * %esi : memory location to compare

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 * %eax : low 32 bits of old value

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 * %edx : high 32 bits of old value

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 * %ebx : low 32 bits of new value

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 * %ecx : high 32 bits of new value

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 */

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SYM_FUNC_START(cmpxchg8b_emu)

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	pushfl

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	cli

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	cmpl	(%esi), %eax

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	jne	.Lnot_same

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	cmpl	4(%esi), %edx

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	jne	.Lnot_same

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	movl	%ebx, (%esi)

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	movl	%ecx, 4(%esi)

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	orl	$X86_EFLAGS_ZF, (%esp)

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	popfl

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	RET

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.Lnot_same:

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	movl	(%esi), %eax

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	movl	4(%esi), %edx

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	andl	$(~X86_EFLAGS_ZF), (%esp)

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	popfl

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	RET

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SYM_FUNC_END(cmpxchg8b_emu)

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EXPORT_SYMBOL(cmpxchg8b_emu)

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#endif

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#ifndef CONFIG_UML

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/*

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 * Emulate 'cmpxchg8b %fs:(%rsi)'

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 *

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 * Inputs:

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 * %esi : memory location to compare

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 * %eax : low 32 bits of old value

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 * %edx : high 32 bits of old value

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 * %ebx : low 32 bits of new value

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 * %ecx : high 32 bits of new value

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 *

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 * Notably this is not LOCK prefixed and is not safe against NMIs

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 */

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SYM_FUNC_START(this_cpu_cmpxchg8b_emu)

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	pushfl

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	cli

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	cmpl	__percpu (%esi), %eax

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	jne	.Lnot_same2

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	cmpl	__percpu 4(%esi), %edx

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	jne	.Lnot_same2

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	movl	%ebx, __percpu (%esi)

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	movl	%ecx, __percpu 4(%esi)

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	orl	$X86_EFLAGS_ZF, (%esp)

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	popfl

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	RET

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.Lnot_same2:

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	movl	__percpu (%esi), %eax

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	movl	__percpu 4(%esi), %edx

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	andl	$(~X86_EFLAGS_ZF), (%esp)

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	popfl

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	RET

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SYM_FUNC_END(this_cpu_cmpxchg8b_emu)

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#endif

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