nptl/futex-internal.c

   1 /* futex helper functions for glibc-internal use.
   2    Copyright (C) 2020-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <sysdep.h>
  21 #include <time.h>
  22 #include <futex-internal.h>
  23 #include <kernel-features.h>
  24
  25 #ifndef __ASSUME_TIME64_SYSCALLS
  26 static int
  27 __futex_abstimed_wait_common32 (unsigned int* futex_word,
  28                                 unsigned int expected, int op,
  29                                 const struct __timespec64* abstime,
  30                                 int private, bool cancel)
  31 {
  32   struct timespec ts32, *pts32 = NULL;
  33   if (abstime != NULL)
  34     {
  35       ts32 = valid_timespec64_to_timespec (*abstime);
  36       pts32 = &ts32;
  37     }
  38
  39   if (cancel)
  40     return INTERNAL_SYSCALL_CANCEL (futex, futex_word, op, expected,
  41                                     pts32, NULL /* Unused.  */,
  42                                     FUTEX_BITSET_MATCH_ANY);
  43   else
  44     return INTERNAL_SYSCALL_CALL (futex, futex_word, op, expected,
  45                                   pts32, NULL /* Unused.  */,
  46                                   FUTEX_BITSET_MATCH_ANY);
  47 }
  48 #endif /* ! __ASSUME_TIME64_SYSCALLS */
  49
  50 static int
  51 __futex_abstimed_wait_common64 (unsigned int* futex_word,
  52                                 unsigned int expected, int op,
  53                                 const struct __timespec64* abstime,
  54                                 int private, bool cancel)
  55 {
  56   if (cancel)
  57     return INTERNAL_SYSCALL_CANCEL (futex_time64, futex_word, op, expected,
  58                                     abstime, NULL /* Unused.  */,
  59                                     FUTEX_BITSET_MATCH_ANY);
  60   else
  61     return INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op, expected,
  62                                   abstime, NULL /* Unused.  */,
  63                                   FUTEX_BITSET_MATCH_ANY);
  64 }
  65
  66 static int
  67 __futex_abstimed_wait_common (unsigned int* futex_word,
  68                               unsigned int expected, clockid_t clockid,
  69                               const struct __timespec64* abstime,
  70                               int private, bool cancel)
  71 {
  72   int err;
  73   unsigned int clockbit;
  74
  75   /* Work around the fact that the kernel rejects negative timeout values
  76      despite them being valid.  */
  77   if (__glibc_unlikely ((abstime != NULL) && (abstime->tv_sec < 0)))
  78     return ETIMEDOUT;
  79
  80   if (! lll_futex_supported_clockid (clockid))
  81     return EINVAL;
  82
  83   clockbit = (clockid == CLOCK_REALTIME) ? FUTEX_CLOCK_REALTIME : 0;
  84   int op = __lll_private_flag (FUTEX_WAIT_BITSET | clockbit, private);
  85
  86 #ifdef __ASSUME_TIME64_SYSCALLS
  87   err = __futex_abstimed_wait_common64 (futex_word, expected, op, abstime,
  88                                         private, cancel);
  89 #else
  90   bool need_time64 = abstime != NULL && !in_int32_t_range (abstime->tv_sec);
  91   if (need_time64)
  92     {
  93       err = __futex_abstimed_wait_common64 (futex_word, expected, op, abstime,
  94                                             private, cancel);
  95       if (err == -ENOSYS)
  96         err = -EOVERFLOW;
  97     }
  98   else
  99     err = __futex_abstimed_wait_common32 (futex_word, expected, op, abstime,
 100                                           private, cancel);
 101 #endif
 102
 103   switch (err)
 104     {
 105     case 0:
 106     case -EAGAIN:
 107     case -EINTR:
 108     case -ETIMEDOUT:
 109     case -EINVAL:
 110     case -EOVERFLOW:  /* Passed absolute timeout uses 64 bit time_t type, but
 111                          underlying kernel does not support 64 bit time_t futex
 112                          syscalls.  */
 113       return -err;
 114
 115     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 116     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 117     /* No other errors are documented at this time.  */
 118     default:
 119       futex_fatal_error ();
 120     }
 121 }
 122
 123 int
 124 __futex_abstimed_wait64 (unsigned int* futex_word, unsigned int expected,
 125                          clockid_t clockid,
 126                          const struct __timespec64* abstime, int private)
 127 {
 128   return __futex_abstimed_wait_common (futex_word, expected, clockid,
 129                                        abstime, private, false);
 130 }
 131 libc_hidden_def (__futex_abstimed_wait64)
 132
 133 int
 134 __futex_abstimed_wait_cancelable64 (unsigned int* futex_word,
 135                                     unsigned int expected, clockid_t clockid,
 136                                     const struct __timespec64* abstime,
 137                                     int private)
 138 {
 139   return __futex_abstimed_wait_common (futex_word, expected, clockid,
 140                                        abstime, private, true);
 141 }
 142 libc_hidden_def (__futex_abstimed_wait_cancelable64)
 143
 144 int
 145 __futex_lock_pi64 (int *futex_word, clockid_t clockid,
 146                    const struct __timespec64 *abstime, int private)
 147 {
 148   int err;
 149
 150   unsigned int clockbit = clockid == CLOCK_REALTIME
 151                           ? FUTEX_CLOCK_REALTIME : 0;
 152   int op_pi2 = __lll_private_flag (FUTEX_LOCK_PI2 | clockbit, private);
 153 #if __ASSUME_FUTEX_LOCK_PI2
 154   /* Assume __ASSUME_TIME64_SYSCALLS since FUTEX_LOCK_PI2 was added later.  */
 155   err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op_pi2, 0, abstime);
 156 #else
 157   /* FUTEX_LOCK_PI does not support clock selection, so for CLOCK_MONOTONIC
 158      the only option is to use FUTEX_LOCK_PI2.  */
 159   int op_pi1 = __lll_private_flag (FUTEX_LOCK_PI, private);
 160   int op_pi = abstime != NULL && clockid != CLOCK_REALTIME ? op_pi2 : op_pi1;
 161
 162 # ifdef __ASSUME_TIME64_SYSCALLS
 163   err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op_pi, 0, abstime);
 164 # else
 165   bool need_time64 = abstime != NULL && !in_int32_t_range (abstime->tv_sec);
 166   if (need_time64)
 167     err = INTERNAL_SYSCALL_CALL (futex_time64, futex_word, op_pi, 0, abstime);
 168   else
 169     {
 170       struct timespec ts32, *pts32 = NULL;
 171       if (abstime != NULL)
 172         {
 173           ts32 = valid_timespec64_to_timespec (*abstime);
 174           pts32 = &ts32;
 175         }
 176       err = INTERNAL_SYSCALL_CALL (futex, futex_word, op_pi, 0, pts32);
 177     }
 178 # endif  /* __ASSUME_TIME64_SYSCALLS */
 179    /* FUTEX_LOCK_PI2 is not available on this kernel.  */
 180    if (err == -ENOSYS)
 181      err = -EINVAL;
 182 #endif /* __ASSUME_FUTEX_LOCK_PI2  */
 183
 184   switch (err)
 185     {
 186     case 0:
 187     case -EAGAIN:
 188     case -EINTR:
 189     case -ETIMEDOUT:
 190     case -ESRCH:
 191     case -EDEADLK:
 192     case -EINVAL: /* This indicates either state corruption or that the kernel
 193                      found a waiter on futex address which is waiting via
 194                      FUTEX_WAIT or FUTEX_WAIT_BITSET.  This is reported on
 195                      some futex_lock_pi usage (pthread_mutex_timedlock for
 196                      instance).  */
 197       return -err;
 198
 199     case -EFAULT: /* Must have been caused by a glibc or application bug.  */
 200     case -ENOSYS: /* Must have been caused by a glibc bug.  */
 201     /* No other errors are documented at this time.  */
 202     default:
 203       futex_fatal_error ();
 204     }
 205 }