sysdeps/unix/sysv/linux/pread64.c

   1 /* Copyright (C) 1997,1998,1999,2000,2002,2003,2006
   2         Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  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_pread64 (int fd, void *buf, size_t count,
  42                                   off64_t offset) internal_function;
  43 # endif
  44
  45
  46 static ssize_t
  47 do_pread64 (int fd, void *buf, size_t count, off64_t offset)
  48 {
  49   ssize_t result;
  50
  51   /* First try the syscall.  */
  52   result = INLINE_SYSCALL (pread, 5, fd, CHECK_N (buf, count), count,
  53                            __LONG_LONG_PAIR ((off_t) (offset >> 32),
  54                                              (off_t) (offset & 0xffffffff)));
  55 # if __ASSUME_PREAD_SYSCALL == 0
  56   if (result == -1 && errno == ENOSYS)
  57     /* No system call available.  Use the emulation.  */
  58     result = __emulate_pread64 (fd, buf, count, offset);
  59 # endif
  60
  61   return result;
  62 }
  63
  64
  65 ssize_t
  66 __libc_pread64 (fd, buf, count, offset)
  67      int fd;
  68      void *buf;
  69      size_t count;
  70      off64_t offset;
  71 {
  72   if (SINGLE_THREAD_P)
  73     return do_pread64 (fd, buf, count, offset);
  74
  75   int oldtype = LIBC_CANCEL_ASYNC ();
  76
  77   ssize_t result = do_pread64 (fd, buf, count, offset);
  78
  79   LIBC_CANCEL_RESET (oldtype);
  80
  81   return result;
  82 }
  83
  84 weak_alias (__libc_pread64, __pread64)
  85 weak_alias (__libc_pread64, pread64)
  86
  87 # define __libc_pread64(fd, buf, count, offset) \
  88      static internal_function __emulate_pread64 (fd, buf, count, offset)
  89 #endif
  90
  91 # if __ASSUME_PREAD_SYSCALL == 0
  92 # include <sysdeps/posix/pread64.c>
  93 #endif