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Jan Beulicha73866942011-07-19 13:00:19 +01001/*
2 * x86 semaphore implementation.
3 *
4 * (C) Copyright 1999 Linus Torvalds
5 *
6 * Portions Copyright 1999 Red Hat, Inc.
7 *
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; either version
11 * 2 of the License, or (at your option) any later version.
12 *
13 * rw semaphores implemented November 1999 by Benjamin LaHaise <bcrl@kvack.org>
14 */
15
16#include <linux/linkage.h>
17#include <asm/alternative-asm.h>
18#include <asm/dwarf2.h>
19
20#define __ASM_HALF_REG(reg) __ASM_SEL(reg, e##reg)
21#define __ASM_HALF_SIZE(inst) __ASM_SEL(inst##w, inst##l)
22
23#ifdef CONFIG_X86_32
24
25/*
26 * The semaphore operations have a special calling sequence that
27 * allow us to do a simpler in-line version of them. These routines
28 * need to convert that sequence back into the C sequence when
29 * there is contention on the semaphore.
30 *
31 * %eax contains the semaphore pointer on entry. Save the C-clobbered
32 * registers (%eax, %edx and %ecx) except %eax whish is either a return
33 * value or just clobbered..
34 */
35
36#define save_common_regs \
37 pushl_cfi %ecx; CFI_REL_OFFSET ecx, 0
38
39#define restore_common_regs \
40 popl_cfi %ecx; CFI_RESTORE ecx
41
42 /* Avoid uglifying the argument copying x86-64 needs to do. */
43 .macro movq src, dst
44 .endm
45
46#else
47
48/*
49 * x86-64 rwsem wrappers
50 *
51 * This interfaces the inline asm code to the slow-path
52 * C routines. We need to save the call-clobbered regs
53 * that the asm does not mark as clobbered, and move the
54 * argument from %rax to %rdi.
55 *
56 * NOTE! We don't need to save %rax, because the functions
57 * will always return the semaphore pointer in %rax (which
58 * is also the input argument to these helpers)
59 *
60 * The following can clobber %rdx because the asm clobbers it:
61 * call_rwsem_down_write_failed
62 * call_rwsem_wake
63 * but %rdi, %rsi, %rcx, %r8-r11 always need saving.
64 */
65
66#define save_common_regs \
67 pushq_cfi %rdi; CFI_REL_OFFSET rdi, 0; \
68 pushq_cfi %rsi; CFI_REL_OFFSET rsi, 0; \
69 pushq_cfi %rcx; CFI_REL_OFFSET rcx, 0; \
70 pushq_cfi %r8; CFI_REL_OFFSET r8, 0; \
71 pushq_cfi %r9; CFI_REL_OFFSET r9, 0; \
72 pushq_cfi %r10; CFI_REL_OFFSET r10, 0; \
73 pushq_cfi %r11; CFI_REL_OFFSET r11, 0
74
75#define restore_common_regs \
76 popq_cfi %r11; CFI_RESTORE r11; \
77 popq_cfi %r10; CFI_RESTORE r10; \
78 popq_cfi %r9; CFI_RESTORE r9; \
79 popq_cfi %r8; CFI_RESTORE r8; \
80 popq_cfi %rcx; CFI_RESTORE rcx; \
81 popq_cfi %rsi; CFI_RESTORE rsi; \
82 popq_cfi %rdi; CFI_RESTORE rdi
83
84#endif
85
86/* Fix up special calling conventions */
87ENTRY(call_rwsem_down_read_failed)
88 CFI_STARTPROC
89 save_common_regs
90 __ASM_SIZE(push,_cfi) %__ASM_REG(dx)
91 CFI_REL_OFFSET __ASM_REG(dx), 0
92 movq %rax,%rdi
93 call rwsem_down_read_failed
94 __ASM_SIZE(pop,_cfi) %__ASM_REG(dx)
95 CFI_RESTORE __ASM_REG(dx)
96 restore_common_regs
97 ret
98 CFI_ENDPROC
99ENDPROC(call_rwsem_down_read_failed)
100
101ENTRY(call_rwsem_down_write_failed)
102 CFI_STARTPROC
103 save_common_regs
104 movq %rax,%rdi
105 call rwsem_down_write_failed
106 restore_common_regs
107 ret
108 CFI_ENDPROC
109ENDPROC(call_rwsem_down_write_failed)
110
111ENTRY(call_rwsem_wake)
112 CFI_STARTPROC
113 /* do nothing if still outstanding active readers */
114 __ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx)
115 jnz 1f
116 save_common_regs
117 movq %rax,%rdi
118 call rwsem_wake
119 restore_common_regs
1201: ret
121 CFI_ENDPROC
122ENDPROC(call_rwsem_wake)
123
124ENTRY(call_rwsem_downgrade_wake)
125 CFI_STARTPROC
126 save_common_regs
127 __ASM_SIZE(push,_cfi) %__ASM_REG(dx)
128 CFI_REL_OFFSET __ASM_REG(dx), 0
129 movq %rax,%rdi
130 call rwsem_downgrade_wake
131 __ASM_SIZE(pop,_cfi) %__ASM_REG(dx)
132 CFI_RESTORE __ASM_REG(dx)
133 restore_common_regs
134 ret
135 CFI_ENDPROC
136ENDPROC(call_rwsem_downgrade_wake)