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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <endian.h>
  22 #include <unistd.h>
  23
  24 #include <sysdep-cancel.h>
  25 #include <sys/syscall.h>
  26 #include <bp-checks.h>
  27
  28 #include <kernel-features.h>
  29
  30 #ifdef __NR_pread64             /* Newer kernels renamed but it's the same.  */
  31 # ifdef __NR_pread
  32 #  error "__NR_pread and __NR_pread64 both defined???"
  33 # endif
  34 # define __NR_pread __NR_pread64
  35 #endif
  36
  37 #if defined __NR_pread || __ASSUME_PREAD_SYSCALL > 0
  38
  39 # if __ASSUME_PREAD_SYSCALL == 0
  40 static ssize_t __emulate_pread64 (int fd, void *buf, size_t count,
  41                                   off64_t offset) internal_function;
  42 # endif
  43
  44
  45 static ssize_t
  46 do_pread64 (int fd, void *buf, size_t count, off64_t offset)
  47 {
  48   ssize_t result;
  49
  50   /* First try the syscall.  */
  51   result = INLINE_SYSCALL (pread, 5, fd, CHECK_N (buf, count), count,
  52                            __LONG_LONG_PAIR ((off_t) (offset >> 32),
  53                                              (off_t) (offset & 0xffffffff)));
  54 # if __ASSUME_PREAD_SYSCALL == 0
  55   if (result == -1 && errno == ENOSYS)
  56     /* No system call available.  Use the emulation.  */
  57     result = __emulate_pread64 (fd, buf, count, offset);
  58 # endif
  59
  60   return result;
  61 }
  62
  63
  64 ssize_t
  65 __libc_pread64 (fd, buf, count, offset)
  66      int fd;
  67      void *buf;
  68      size_t count;
  69      off64_t offset;
  70 {
  71   if (SINGLE_THREAD_P)
  72     return do_pread64 (fd, buf, count, offset);
  73
  74   int oldtype = LIBC_CANCEL_ASYNC ();
  75
  76   ssize_t result = do_pread64 (fd, buf, count, offset);
  77
  78   LIBC_CANCEL_RESET (oldtype);
  79
  80   return result;
  81 }
  82
  83 weak_alias (__libc_pread64, __pread64)
  84 weak_alias (__libc_pread64, pread64)
  85
  86 # define __libc_pread64(fd, buf, count, offset) \
  87      static internal_function __emulate_pread64 (fd, buf, count, offset)
  88 #endif
  89
  90 # if __ASSUME_PREAD_SYSCALL == 0
  91 # include <sysdeps/posix/pread64.c>
  92 #endif