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d7c3f8cee8
Omit the segment prefix in the UP case. GS is not used then and we will generate segfaults if cmpxchg16b is used otherwise. Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
66 lines
1.3 KiB
ArmAsm
66 lines
1.3 KiB
ArmAsm
/*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; version 2
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* of the License.
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*
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*/
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#include <linux/linkage.h>
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#include <asm/alternative-asm.h>
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#include <asm/frame.h>
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#include <asm/dwarf2.h>
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#ifdef CONFIG_SMP
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#define SEG_PREFIX %gs:
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#else
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#define SEG_PREFIX
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#endif
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.text
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/*
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* Inputs:
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* %rsi : memory location to compare
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* %rax : low 64 bits of old value
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* %rdx : high 64 bits of old value
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* %rbx : low 64 bits of new value
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* %rcx : high 64 bits of new value
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* %al : Operation successful
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*/
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ENTRY(this_cpu_cmpxchg16b_emu)
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CFI_STARTPROC
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#
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# Emulate 'cmpxchg16b %gs:(%rsi)' except we return the result in %al not
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# via the ZF. Caller will access %al to get result.
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#
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# Note that this is only useful for a cpuops operation. Meaning that we
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# do *not* have a fully atomic operation but just an operation that is
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# *atomic* on a single cpu (as provided by the this_cpu_xx class of
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# macros).
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#
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this_cpu_cmpxchg16b_emu:
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pushf
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cli
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cmpq SEG_PREFIX(%rsi), %rax
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jne not_same
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cmpq SEG_PREFIX 8(%rsi), %rdx
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jne not_same
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movq %rbx, SEG_PREFIX(%rsi)
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movq %rcx, SEG_PREFIX 8(%rsi)
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popf
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mov $1, %al
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ret
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not_same:
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popf
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xor %al,%al
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ret
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CFI_ENDPROC
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ENDPROC(this_cpu_cmpxchg16b_emu)
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