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b9ec40af CL |
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 | ||
d7c3f8ce CL |
13 | #ifdef CONFIG_SMP |
14 | #define SEG_PREFIX %gs: | |
15 | #else | |
16 | #define SEG_PREFIX | |
17 | #endif | |
18 | ||
b9ec40af CL |
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 | */ | |
30 | ENTRY(this_cpu_cmpxchg16b_emu) | |
31 | CFI_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 | # | |
42 | this_cpu_cmpxchg16b_emu: | |
43 | pushf | |
44 | cli | |
45 | ||
d7c3f8ce | 46 | cmpq SEG_PREFIX(%rsi), %rax |
b9ec40af | 47 | jne not_same |
d7c3f8ce | 48 | cmpq SEG_PREFIX 8(%rsi), %rdx |
b9ec40af CL |
49 | jne not_same |
50 | ||
d7c3f8ce CL |
51 | movq %rbx, SEG_PREFIX(%rsi) |
52 | movq %rcx, SEG_PREFIX 8(%rsi) | |
b9ec40af CL |
53 | |
54 | popf | |
55 | mov $1, %al | |
56 | ret | |
57 | ||
58 | not_same: | |
59 | popf | |
60 | xor %al,%al | |
61 | ret | |
62 | ||
63 | CFI_ENDPROC | |
64 | ||
65 | ENDPROC(this_cpu_cmpxchg16b_emu) |