sysdeps/unix/sysv/linux/pread.c

   1 /* Copyright (C) 1997-2000,2002,2003,2004,2006 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   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 <assert.h>
  21 #include <errno.h>
  22 #include <endian.h>
  23 #include <unistd.h>
  24
  25 #include <sysdep-cancel.h>
  26 #include <sys/syscall.h>
  27 #include <bp-checks.h>
  28
  29 #include <kernel-features.h>
  30
  31 #ifdef __NR_pread64             /* Newer kernels renamed but it's the same.  */
  32 # ifdef __NR_pread
  33 #  error "__NR_pread and __NR_pread64 both defined???"
  34 # endif
  35 # define __NR_pread __NR_pread64
  36 #endif
  37
  38 #if defined __NR_pread || __ASSUME_PREAD_SYSCALL > 0
  39
  40 # if __ASSUME_PREAD_SYSCALL == 0
  41 static ssize_t __emulate_pread (int fd, void *buf, size_t count,
  42                                 off_t offset) internal_function;
  43 # endif
  44
  45
  46 static ssize_t
  47 #ifdef NO_CANCELLATION
  48 inline __attribute ((always_inline))
  49 #endif
  50 do_pread (int fd, void *buf, size_t count, off_t offset)
  51 {
  52   ssize_t result;
  53
  54   /* First try the syscall.  */
  55   assert (sizeof (offset) == 4);
  56   result = INLINE_SYSCALL (pread, 5, fd, CHECK_N (buf, count), count,
  57                            __LONG_LONG_PAIR (offset >> 31, offset));
  58 # if __ASSUME_PREAD_SYSCALL == 0
  59   if (result == -1 && errno == ENOSYS)
  60     /* No system call available.  Use the emulation.  */
  61     result = __emulate_pread (fd, buf, count, offset);
  62 # endif
  63
  64   return result;
  65 }
  66
  67
  68 ssize_t
  69 __libc_pread (fd, buf, count, offset)
  70      int fd;
  71      void *buf;
  72      size_t count;
  73      off_t offset;
  74 {
  75   if (SINGLE_THREAD_P)
  76     return do_pread (fd, buf, count, offset);
  77
  78   int oldtype = LIBC_CANCEL_ASYNC ();
  79
  80   ssize_t result = do_pread (fd, buf, count, offset);
  81
  82   LIBC_CANCEL_RESET (oldtype);
  83
  84   return result;
  85 }
  86
  87 strong_alias (__libc_pread, __pread)
  88 weak_alias (__libc_pread, pread)
  89
  90 # define __libc_pread(fd, buf, count, offset) \
  91      static internal_function __emulate_pread (fd, buf, count, offset)
  92 #endif
  93
  94 #if __ASSUME_PREAD_SYSCALL == 0
  95 # include <sysdeps/posix/pread.c>
  96 #endif