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/*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; version 2
* of the License.
*
*/
#include <linux/linkage.h>
#include <asm/alternative-asm.h>
#include <asm/frame.h>
#include <asm/dwarf2.h>
#ifdef CONFIG_SMP
#define SEG_PREFIX %gs:
#else
#define SEG_PREFIX
#endif
.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)
CFI_STARTPROC
#
# 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).
#
this_cpu_cmpxchg16b_emu:
pushf
cli
cmpq SEG_PREFIX(%rsi), %rax
jne not_same
cmpq SEG_PREFIX 8(%rsi), %rdx
jne not_same
movq %rbx, SEG_PREFIX(%rsi)
movq %rcx, SEG_PREFIX 8(%rsi)
popf
mov $1, %al
ret
not_same:
popf
xor %al,%al
ret
CFI_ENDPROC
ENDPROC(this_cpu_cmpxchg16b_emu)
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