sysdeps/unix/sysv/linux/poll.c

   1 /* Poll system call, with emulation if it is not available.
   2    Copyright (C) 1997,1998,1999,2000,2001,2002 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <errno.h>
  21 #include <sys/poll.h>
  22
  23 #include <sysdep-cancel.h>
  24 #include <sys/syscall.h>
  25 #include <bp-checks.h>
  26
  27 #include "kernel-features.h"
  28
  29 #if defined __NR_poll || __ASSUME_POLL_SYSCALL > 0
  30
  31 # if __ASSUME_POLL_SYSCALL == 0
  32 static int __emulate_poll (struct pollfd *fds, nfds_t nfds,
  33                            int timeout) internal_function;
  34 # endif
  35
  36
  37 # if __ASSUME_POLL_SYSCALL == 0
  38 /* For loser kernels.  */
  39 static int
  40 loser_poll (struct pollfd *fds, nfds_t nfds, int timeout)
  41 {
  42   static int must_emulate;
  43
  44   if (!must_emulate)
  45     {
  46       int errno_saved = errno;
  47       int retval = INLINE_SYSCALL (poll, 3, CHECK_N (fds, nfds), nfds,
  48                                    timeout);
  49
  50       if (retval >= 0 || errno != ENOSYS)
  51         return retval;
  52
  53       __set_errno (errno_saved);
  54       must_emulate = 1;
  55     }
  56
  57   return __emulate_poll (fds, nfds, timeout);
  58 }
  59 # endif
  60
  61
  62 /* The real implementation.  */
  63 int
  64 __poll (fds, nfds, timeout)
  65      struct pollfd *fds;
  66      nfds_t nfds;
  67      int timeout;
  68 {
  69 # if __ASSUME_POLL_SYSCALL == 0
  70   if (SINGLE_THREAD_P)
  71     return loser_poll (CHECK_N (fds, nfds), nfds, timeout);
  72
  73   int oldtype = LIBC_CANCEL_ASYNC ();
  74
  75   int result = loser_poll (CHECK_N (fds, nfds), nfds, timeout);
  76
  77    LIBC_CANCEL_RESET (oldtype);
  78
  79   return result;
  80 # else
  81   if (SINGLE_THREAD_P)
  82     return INLINE_SYSCALL (poll, 3, CHECK_N (fds, nfds), nfds, timeout);
  83
  84   int oldtype = LIBC_CANCEL_ASYNC ();
  85
  86   int result = INLINE_SYSCALL (poll, 3, CHECK_N (fds, nfds), nfds, timeout);
  87
  88    LIBC_CANCEL_RESET (oldtype);
  89
  90   return result;
  91 # endif
  92 }
  93 libc_hidden_def (__poll)
  94 weak_alias (__poll, poll)
  95 strong_alias (__poll, __libc_poll)
  96
  97 /* Get the emulation code.  */
  98 # define __poll(fds, nfds, timeout) \
  99   static internal_function __emulate_poll (fds, nfds, timeout)
 100 #endif
 101
 102 #if __ASSUME_POLL_SYSCALL == 0
 103 # include <sysdeps/unix/bsd/poll.c>
 104 #endif