libgcc/config/arm/linux-atomic-64bit.c

   1 /* 64bit Linux-specific atomic operations for ARM EABI.
   2    Copyright (C) 2008-2016 Free Software Foundation, Inc.
   3    Based on linux-atomic.c
   4
   5    64 bit additions david.gilbert@linaro.org
   6
   7 This file is part of GCC.
   8
   9 GCC is free software; you can redistribute it and/or modify it under
  10 the terms of the GNU General Public License as published by the Free
  11 Software Foundation; either version 3, or (at your option) any later
  12 version.
  13
  14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  16 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  17 for more details.
  18
  19 Under Section 7 of GPL version 3, you are granted additional
  20 permissions described in the GCC Runtime Library Exception, version
  21 3.1, as published by the Free Software Foundation.
  22
  23 You should have received a copy of the GNU General Public License and
  24 a copy of the GCC Runtime Library Exception along with this program;
  25 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  26 <http://www.gnu.org/licenses/>.  */
  27
  28 /* 64bit helper functions for atomic operations; the compiler will
  29    call these when the code is compiled for a CPU without ldrexd/strexd.
  30    (If the CPU had those then the compiler inlines the operation).
  31
  32    These helpers require a kernel helper that's only present on newer
  33    kernels; we check for that in an init section and bail out rather
  34    unceremoneously.  */
  35
  36 extern int write (int fd, const void *buf, unsigned int count);
  37 extern void abort (void);
  38
  39 /* Kernel helper for compare-and-exchange.  */
  40 typedef int (__kernel_cmpxchg64_t) (const long long* oldval,
  41                                         const long long* newval,
  42                                         long long *ptr);
  43 #define __kernel_cmpxchg64 (*(__kernel_cmpxchg64_t *) 0xffff0f60)
  44
  45 /* Kernel helper page version number.  */
  46 #define __kernel_helper_version (*(unsigned int *)0xffff0ffc)
  47
  48 /* Check that the kernel has a new enough version at load.  */
  49 static void __check_for_sync8_kernelhelper (void)
  50 {
  51   if (__kernel_helper_version < 5)
  52     {
  53       const char err[] = "A newer kernel is required to run this binary. "
  54                                 "(__kernel_cmpxchg64 helper)\n";
  55       /* At this point we need a way to crash with some information
  56          for the user - I'm not sure I can rely on much else being
  57          available at this point, so do the same as generic-morestack.c
  58          write () and abort ().  */
  59       write (2 /* stderr.  */, err, sizeof (err));
  60       abort ();
  61     }
  62 };
  63
  64 static void (*__sync8_kernelhelper_inithook[]) (void)
  65                 __attribute__ ((used, section (".init_array"))) = {
  66   &__check_for_sync8_kernelhelper
  67 };
  68
  69 #define HIDDEN __attribute__ ((visibility ("hidden")))
  70
  71 #define FETCH_AND_OP_WORD64(OP, PFX_OP, INF_OP)                 \
  72   long long HIDDEN                                              \
  73   __sync_fetch_and_##OP##_8 (long long *ptr, long long val)     \
  74   {                                                             \
  75     int failure;                                                \
  76     long long tmp,tmp2;                                         \
  77                                                                 \
  78     do {                                                        \
  79       tmp = *ptr;                                               \
  80       tmp2 = PFX_OP (tmp INF_OP val);                           \
  81       failure = __kernel_cmpxchg64 (&tmp, &tmp2, ptr);          \
  82     } while (failure != 0);                                     \
  83                                                                 \
  84     return tmp;                                                 \
  85   }
  86
  87 FETCH_AND_OP_WORD64 (add,   , +)
  88 FETCH_AND_OP_WORD64 (sub,   , -)
  89 FETCH_AND_OP_WORD64 (or,    , |)
  90 FETCH_AND_OP_WORD64 (and,   , &)
  91 FETCH_AND_OP_WORD64 (xor,   , ^)
  92 FETCH_AND_OP_WORD64 (nand, ~, &)
  93
  94 #define NAME_oldval(OP, WIDTH) __sync_fetch_and_##OP##_##WIDTH
  95 #define NAME_newval(OP, WIDTH) __sync_##OP##_and_fetch_##WIDTH
  96
  97 /* Implement both __sync_<op>_and_fetch and __sync_fetch_and_<op> for
  98    subword-sized quantities.  */
  99
 100 #define OP_AND_FETCH_WORD64(OP, PFX_OP, INF_OP)                 \
 101   long long HIDDEN                                              \
 102   __sync_##OP##_and_fetch_8 (long long *ptr, long long val)     \
 103   {                                                             \
 104     int failure;                                                \
 105     long long tmp,tmp2;                                         \
 106                                                                 \
 107     do {                                                        \
 108       tmp = *ptr;                                               \
 109       tmp2 = PFX_OP (tmp INF_OP val);                           \
 110       failure = __kernel_cmpxchg64 (&tmp, &tmp2, ptr);          \
 111     } while (failure != 0);                                     \
 112                                                                 \
 113     return tmp2;                                                \
 114   }
 115
 116 OP_AND_FETCH_WORD64 (add,   , +)
 117 OP_AND_FETCH_WORD64 (sub,   , -)
 118 OP_AND_FETCH_WORD64 (or,    , |)
 119 OP_AND_FETCH_WORD64 (and,   , &)
 120 OP_AND_FETCH_WORD64 (xor,   , ^)
 121 OP_AND_FETCH_WORD64 (nand, ~, &)
 122
 123 long long HIDDEN
 124 __sync_val_compare_and_swap_8 (long long *ptr, long long oldval,
 125                                 long long newval)
 126 {
 127   int failure;
 128   long long actual_oldval;
 129
 130   while (1)
 131     {
 132       actual_oldval = *ptr;
 133
 134       if (__builtin_expect (oldval != actual_oldval, 0))
 135         return actual_oldval;
 136
 137       failure = __kernel_cmpxchg64 (&actual_oldval, &newval, ptr);
 138
 139       if (__builtin_expect (!failure, 1))
 140         return oldval;
 141     }
 142 }
 143
 144 typedef unsigned char bool;
 145
 146 bool HIDDEN
 147 __sync_bool_compare_and_swap_8 (long long *ptr, long long oldval,
 148                                  long long newval)
 149 {
 150   int failure = __kernel_cmpxchg64 (&oldval, &newval, ptr);
 151   return (failure == 0);
 152 }
 153
 154 long long HIDDEN
 155 __sync_lock_test_and_set_8 (long long *ptr, long long val)
 156 {
 157   int failure;
 158   long long oldval;
 159
 160   do {
 161     oldval = *ptr;
 162     failure = __kernel_cmpxchg64 (&oldval, &val, ptr);
 163   } while (failure != 0);
 164
 165   return oldval;
 166 }