| Andrew Scull | b4b6d4a | 2019-01-02 15:54:55 +0000 | [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/frame.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 which is either a return |
| 33 | * value or just gets clobbered. Same is true for %edx so make sure GCC |
| 34 | * reloads it after the slow path, by making it hold a temporary, for |
| 35 | * example see ____down_write(). |
| 36 | */ |
| 37 | |
| 38 | #define save_common_regs \ |
| 39 | pushl %ecx |
| 40 | |
| 41 | #define restore_common_regs \ |
| 42 | popl %ecx |
| 43 | |
| 44 | /* Avoid uglifying the argument copying x86-64 needs to do. */ |
| 45 | .macro movq src, dst |
| 46 | .endm |
| 47 | |
| 48 | #else |
| 49 | |
| 50 | /* |
| 51 | * x86-64 rwsem wrappers |
| 52 | * |
| 53 | * This interfaces the inline asm code to the slow-path |
| 54 | * C routines. We need to save the call-clobbered regs |
| 55 | * that the asm does not mark as clobbered, and move the |
| 56 | * argument from %rax to %rdi. |
| 57 | * |
| 58 | * NOTE! We don't need to save %rax, because the functions |
| 59 | * will always return the semaphore pointer in %rax (which |
| 60 | * is also the input argument to these helpers) |
| 61 | * |
| 62 | * The following can clobber %rdx because the asm clobbers it: |
| 63 | * call_rwsem_down_write_failed |
| 64 | * call_rwsem_wake |
| 65 | * but %rdi, %rsi, %rcx, %r8-r11 always need saving. |
| 66 | */ |
| 67 | |
| 68 | #define save_common_regs \ |
| 69 | pushq %rdi; \ |
| 70 | pushq %rsi; \ |
| 71 | pushq %rcx; \ |
| 72 | pushq %r8; \ |
| 73 | pushq %r9; \ |
| 74 | pushq %r10; \ |
| 75 | pushq %r11 |
| 76 | |
| 77 | #define restore_common_regs \ |
| 78 | popq %r11; \ |
| 79 | popq %r10; \ |
| 80 | popq %r9; \ |
| 81 | popq %r8; \ |
| 82 | popq %rcx; \ |
| 83 | popq %rsi; \ |
| 84 | popq %rdi |
| 85 | |
| 86 | #endif |
| 87 | |
| 88 | /* Fix up special calling conventions */ |
| 89 | ENTRY(call_rwsem_down_read_failed) |
| 90 | FRAME_BEGIN |
| 91 | save_common_regs |
| 92 | __ASM_SIZE(push,) %__ASM_REG(dx) |
| 93 | movq %rax,%rdi |
| 94 | call rwsem_down_read_failed |
| 95 | __ASM_SIZE(pop,) %__ASM_REG(dx) |
| 96 | restore_common_regs |
| 97 | FRAME_END |
| 98 | ret |
| 99 | ENDPROC(call_rwsem_down_read_failed) |
| 100 | |
| 101 | ENTRY(call_rwsem_down_read_failed_killable) |
| 102 | FRAME_BEGIN |
| 103 | save_common_regs |
| 104 | __ASM_SIZE(push,) %__ASM_REG(dx) |
| 105 | movq %rax,%rdi |
| 106 | call rwsem_down_read_failed_killable |
| 107 | __ASM_SIZE(pop,) %__ASM_REG(dx) |
| 108 | restore_common_regs |
| 109 | FRAME_END |
| 110 | ret |
| 111 | ENDPROC(call_rwsem_down_read_failed_killable) |
| 112 | |
| 113 | ENTRY(call_rwsem_down_write_failed) |
| 114 | FRAME_BEGIN |
| 115 | save_common_regs |
| 116 | movq %rax,%rdi |
| 117 | call rwsem_down_write_failed |
| 118 | restore_common_regs |
| 119 | FRAME_END |
| 120 | ret |
| 121 | ENDPROC(call_rwsem_down_write_failed) |
| 122 | |
| 123 | ENTRY(call_rwsem_down_write_failed_killable) |
| 124 | FRAME_BEGIN |
| 125 | save_common_regs |
| 126 | movq %rax,%rdi |
| 127 | call rwsem_down_write_failed_killable |
| 128 | restore_common_regs |
| 129 | FRAME_END |
| 130 | ret |
| 131 | ENDPROC(call_rwsem_down_write_failed_killable) |
| 132 | |
| 133 | ENTRY(call_rwsem_wake) |
| 134 | FRAME_BEGIN |
| 135 | /* do nothing if still outstanding active readers */ |
| 136 | __ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx) |
| 137 | jnz 1f |
| 138 | save_common_regs |
| 139 | movq %rax,%rdi |
| 140 | call rwsem_wake |
| 141 | restore_common_regs |
| 142 | 1: FRAME_END |
| 143 | ret |
| 144 | ENDPROC(call_rwsem_wake) |
| 145 | |
| 146 | ENTRY(call_rwsem_downgrade_wake) |
| 147 | FRAME_BEGIN |
| 148 | save_common_regs |
| 149 | __ASM_SIZE(push,) %__ASM_REG(dx) |
| 150 | movq %rax,%rdi |
| 151 | call rwsem_downgrade_wake |
| 152 | __ASM_SIZE(pop,) %__ASM_REG(dx) |
| 153 | restore_common_regs |
| 154 | FRAME_END |
| 155 | ret |
| 156 | ENDPROC(call_rwsem_downgrade_wake) |