| Jan Beulich | a7386694 | 2011-07-19 13:00:19 +0100 | [diff] [blame] | 1 | /* |
| 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 */ |
| 87 | ENTRY(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 |
| 99 | ENDPROC(call_rwsem_down_read_failed) |
| 100 | |
| 101 | ENTRY(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 |
| 109 | ENDPROC(call_rwsem_down_write_failed) |
| 110 | |
| 111 | ENTRY(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 |
| 120 | 1: ret |
| 121 | CFI_ENDPROC |
| 122 | ENDPROC(call_rwsem_wake) |
| 123 | |
| 124 | ENTRY(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 |
| 136 | ENDPROC(call_rwsem_downgrade_wake) |