libc/sysdeps/linux/common/pselect.c

   1 /* Copyright (C) 1996-1998,2001,2002,2003,2006 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   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    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <features.h>
  20
  21 #ifdef __USE_XOPEN2K
  22
  23 #include <sys/syscall.h>
  24 #include <sys/select.h>
  25 #include <sys/time.h>
  26 #include <signal.h>
  27 #include <cancel.h>
  28
  29 static int __NC(pselect)(int nfds, fd_set *readfds, fd_set *writefds,
  30                          fd_set *exceptfds, const struct timespec *timeout,
  31                          const sigset_t *sigmask)
  32 {
  33 #ifdef __NR_pselect6
  34         /* The Linux kernel can in some situations update the timeout value.
  35          * We do not want that so use a local variable.
  36          */
  37         struct timespec _ts;
  38
  39         /* Note: the system call expects 7 values but on most architectures
  40            we can only pass in 6 directly.  If there is an architecture with
  41            support for more parameters a new version of this file needs to
  42            be created.  */
  43         struct {
  44                 __kernel_ulong_t ss;
  45                 __kernel_size_t  ss_len;
  46         } data;
  47
  48         if (timeout != NULL) {
  49                 _ts = *timeout;
  50                 timeout = &_ts;
  51         }
  52
  53         if (sigmask != NULL) {
  54                 data.ss = (__kernel_ulong_t) sigmask;
  55                 data.ss_len = __SYSCALL_SIGSET_T_SIZE;
  56
  57                 sigmask = (void *)&data;
  58         }
  59 #if defined(__UCLIBC_USE_TIME64__) && defined(__NR_pselect6_time64)
  60         return INLINE_SYSCALL(pselect6_time64, 6, nfds, readfds, writefds, exceptfds, timeout, sigmask);
  61 #else
  62         return INLINE_SYSCALL(pselect6, 6, nfds, readfds, writefds, exceptfds, timeout, sigmask);
  63 #endif
  64 #else
  65         struct timeval tval;
  66         int retval;
  67         sigset_t savemask;
  68
  69         /* Change nanosecond number to microseconds.  This might mean losing
  70            precision and therefore the `pselect` should be available.  But
  71            for now it is hardly found.  */
  72         if (timeout != NULL)
  73                 TIMESPEC_TO_TIMEVAL (&tval, timeout);
  74
  75         /* The setting and restoring of the signal mask and the select call
  76            should be an atomic operation.  This can't be done without kernel
  77            help.  */
  78         if (sigmask != NULL)
  79                 sigprocmask (SIG_SETMASK, sigmask, &savemask);
  80
  81         /* The comment below does not apply on uClibc, since we use __select_nocancel */
  82         /* Note the pselect() is a cancellation point.  But since we call
  83            select() which itself is a cancellation point we do not have
  84            to do anything here.  */
  85         retval = __NC(select)(nfds, readfds, writefds, exceptfds,
  86                         timeout != NULL ? &tval : NULL);
  87
  88         if (sigmask != NULL)
  89                 sigprocmask (SIG_SETMASK, &savemask, NULL);
  90
  91         return retval;
  92 #endif
  93 }
  94
  95 CANCELLABLE_SYSCALL(int, pselect, (int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
  96                                    const struct timespec *timeout, const sigset_t *sigmask),
  97                     (nfds, readfds, writefds, exceptfds, timeout, sigmask))
  98
  99 #endif