sysdeps/unix/sysv/linux/select.c

   1 /* Linux select implementation.
   2    Copyright (C) 2017-2021 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 <sys/time.h>
  20 #include <sys/types.h>
  21 #include <sys/select.h>
  22 #include <errno.h>
  23 #include <sysdep-cancel.h>
  24 #include <time64-support.h>
  25
  26 /* Check the first NFDS descriptors each in READFDS (if not NULL) for read
  27    readiness, in WRITEFDS (if not NULL) for write readiness, and in EXCEPTFDS
  28    (if not NULL) for exceptional conditions.  If TIMEOUT is not NULL, time out
  29    after waiting the interval specified therein.  Returns the number of ready
  30    descriptors, or -1 for errors.  */
  31
  32 int
  33 __select64 (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
  34             struct __timeval64 *timeout)
  35 {
  36   struct __timespec64 ts64, *pts64 = NULL;
  37   if (timeout != NULL)
  38     {
  39       ts64 = timeval64_to_timespec64 (*timeout);
  40       pts64 = &ts64;
  41     }
  42
  43 #ifndef __NR_pselect6_time64
  44 # define __NR_pselect6_time64 __NR_pselect6
  45 #endif
  46   int r;
  47   if (supports_time64 ())
  48     {
  49       r = SYSCALL_CANCEL (pselect6_time64, nfds, readfds, writefds, exceptfds,
  50                           pts64, NULL);
  51       /* Linux by default will update the timeout after a pselect6 syscall
  52          (though the pselect() glibc call suppresses this behavior).
  53          Since select() on Linux has the same behavior as the pselect6
  54          syscall, we update the timeout here.  */
  55       if (r == 0 || errno != ENOSYS)
  56         {
  57           if (timeout != NULL)
  58             TIMEVAL_TO_TIMESPEC (timeout, &ts64);
  59           return r;
  60         }
  61
  62       mark_time64_unsupported ();
  63     }
  64
  65 #ifndef __ASSUME_TIME64_SYSCALLS
  66   struct timespec ts32, *pts32 = NULL;
  67   if (timeout != NULL)
  68     {
  69       if (! in_time_t_range (timeout->tv_sec))
  70         {
  71           __set_errno (EINVAL);
  72           return -1;
  73         }
  74       ts32 = valid_timespec64_to_timespec (ts64);
  75       pts32 = &ts32;
  76     }
  77 # ifndef __ASSUME_PSELECT
  78 #  ifdef __NR__newselect
  79 #   undef __NR_select
  80 #   define __NR_select __NR__newselect
  81 #  endif
  82   r = SYSCALL_CANCEL (select, nfds, readfds, writefds, exceptfds, pts32);
  83 # else
  84   r = SYSCALL_CANCEL (pselect6, nfds, readfds, writefds, exceptfds, pts32,
  85                       NULL);
  86 # endif
  87   if (r >= 0 && timeout != NULL)
  88     *timeout = valid_timespec_to_timeval64 (ts32);
  89 #endif
  90
  91   return r;
  92 }
  93
  94 #if __TIMESIZE != 64
  95 libc_hidden_def (__select64)
  96
  97 int
  98 __select (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
  99           struct timeval *timeout)
 100 {
 101   struct __timeval64 tv64, *ptv64 = NULL;
 102   if (timeout != NULL)
 103     {
 104       tv64 = valid_timeval_to_timeval64 (*timeout);
 105       ptv64 = &tv64;
 106     }
 107   int r = __select64 (nfds, readfds, writefds, exceptfds, ptv64);
 108   if (r >= 0 && timeout != NULL)
 109     /* The remanining timeout will be always less the input TIMEOUT.  */
 110     *timeout = valid_timeval64_to_timeval (tv64);
 111   return r;
 112 }
 113 #endif
 114 libc_hidden_def (__select)
 115
 116 weak_alias (__select, select)
 117 weak_alias (__select, __libc_select)