diff options
Diffstat (limited to 'arch/x86/lib/cmpxchg16b_emu.S')
| -rw-r--r-- | arch/x86/lib/cmpxchg16b_emu.S | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/arch/x86/lib/cmpxchg16b_emu.S b/arch/x86/lib/cmpxchg16b_emu.S new file mode 100644 index 000000000..9b330242e --- /dev/null +++ b/arch/x86/lib/cmpxchg16b_emu.S @@ -0,0 +1,53 @@ +/* + * 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/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) |