1  /* mmap - map files or devices into memory.  Linux version.
       2     Copyright (C) 1999-2023 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, see
      17     <https://www.gnu.org/licenses/>.  */
      18  
      19  #include <errno.h>
      20  #include <unistd.h>
      21  #include <sys/mman.h>
      22  #include <sysdep.h>
      23  #include <mmap_internal.h>
      24  
      25  #ifdef __NR_mmap2
      26  /* To avoid silent truncation of offset when using mmap2, do not accept
      27     offset larger than 1 << (page_shift + off_t bits).  For archictures with
      28     32 bits off_t and page size of 4096 it would be 1^44.  */
      29  # define MMAP_OFF_HIGH_MASK \
      30    ((-(MMAP2_PAGE_UNIT << 1) << (8 * sizeof (off_t) - 1)))
      31  #else
      32  /* Some ABIs might use __NR_mmap while having sizeof (off_t) smaller than
      33     sizeof (off64_t) (currently only MIPS64n32).  For this case just set
      34     zero the higher bits so mmap with large offset does not fail.  */
      35  # define MMAP_OFF_HIGH_MASK  0x0
      36  #endif
      37  
      38  #define MMAP_OFF_MASK (MMAP_OFF_HIGH_MASK | MMAP_OFF_LOW_MASK)
      39  
      40  /* An architecture may override this.  */
      41  #ifndef MMAP_PREPARE
      42  # define MMAP_PREPARE(addr, len, prot, flags, fd, offset)
      43  #endif
      44  
      45  void *
      46  __mmap64 (void *addr, size_t len, int prot, int flags, int fd, off64_t offset)
      47  {
      48    MMAP_CHECK_PAGE_UNIT ();
      49  
      50    if (offset & MMAP_OFF_MASK)
      51      return (void *) INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
      52  
      53    MMAP_PREPARE (addr, len, prot, flags, fd, offset);
      54  #ifdef __NR_mmap2
      55    return (void *) MMAP_CALL (mmap2, addr, len, prot, flags, fd,
      56  			     (off_t) (offset / MMAP2_PAGE_UNIT));
      57  #else
      58    return (void *) MMAP_CALL (mmap, addr, len, prot, flags, fd, offset);
      59  #endif
      60  }
      61  weak_alias (__mmap64, mmap64)
      62  libc_hidden_def (__mmap64)
      63  
      64  #ifdef __OFF_T_MATCHES_OFF64_T
      65  weak_alias (__mmap64, mmap)
      66  weak_alias (__mmap64, __mmap)
      67  libc_hidden_def (__mmap)
      68  #endif