arch/x86/lib/rwsem.S

   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_reg ecx
  38
  39 #define restore_common_regs \
  40         popl_cfi_reg 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_reg rdi; \
  68         pushq_cfi_reg rsi; \
  69         pushq_cfi_reg rcx; \
  70         pushq_cfi_reg r8;  \
  71         pushq_cfi_reg r9;  \
  72         pushq_cfi_reg r10; \
  73         pushq_cfi_reg r11
  74
  75 #define restore_common_regs \
  76         popq_cfi_reg r11; \
  77         popq_cfi_reg r10; \
  78         popq_cfi_reg r9; \
  79         popq_cfi_reg r8; \
  80         popq_cfi_reg rcx; \
  81         popq_cfi_reg rsi; \
  82         popq_cfi_reg 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_reg) __ASM_REG(dx)
  91         movq %rax,%rdi
  92         call rwsem_down_read_failed
  93         __ASM_SIZE(pop,_cfi_reg) __ASM_REG(dx)
  94         restore_common_regs
  95         ret
  96         CFI_ENDPROC
  97 ENDPROC(call_rwsem_down_read_failed)
  98
  99 ENTRY(call_rwsem_down_write_failed)
 100         CFI_STARTPROC
 101         save_common_regs
 102         movq %rax,%rdi
 103         call rwsem_down_write_failed
 104         restore_common_regs
 105         ret
 106         CFI_ENDPROC
 107 ENDPROC(call_rwsem_down_write_failed)
 108
 109 ENTRY(call_rwsem_wake)
 110         CFI_STARTPROC
 111         /* do nothing if still outstanding active readers */
 112         __ASM_HALF_SIZE(dec) %__ASM_HALF_REG(dx)
 113         jnz 1f
 114         save_common_regs
 115         movq %rax,%rdi
 116         call rwsem_wake
 117         restore_common_regs
 118 1:      ret
 119         CFI_ENDPROC
 120 ENDPROC(call_rwsem_wake)
 121
 122 ENTRY(call_rwsem_downgrade_wake)
 123         CFI_STARTPROC
 124         save_common_regs
 125         __ASM_SIZE(push,_cfi_reg) __ASM_REG(dx)
 126         movq %rax,%rdi
 127         call rwsem_downgrade_wake
 128         __ASM_SIZE(pop,_cfi_reg) __ASM_REG(dx)
 129         restore_common_regs
 130         ret
 131         CFI_ENDPROC
 132 ENDPROC(call_rwsem_downgrade_wake)