1  /* mmapio.c -- File views using mmap.
       2     Copyright (C) 2012-2023 Free Software Foundation, Inc.
       3     Written by Ian Lance Taylor, Google.
       4  
       5  Redistribution and use in source and binary forms, with or without
       6  modification, are permitted provided that the following conditions are
       7  met:
       8  
       9      (1) Redistributions of source code must retain the above copyright
      10      notice, this list of conditions and the following disclaimer.
      11  
      12      (2) Redistributions in binary form must reproduce the above copyright
      13      notice, this list of conditions and the following disclaimer in
      14      the documentation and/or other materials provided with the
      15      distribution.
      16  
      17      (3) The name of the author may not be used to
      18      endorse or promote products derived from this software without
      19      specific prior written permission.
      20  
      21  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
      22  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
      23  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
      24  DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
      25  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
      26  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
      27  SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
      28  HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
      29  STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
      30  IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
      31  POSSIBILITY OF SUCH DAMAGE.  */
      32  
      33  #include "config.h"
      34  
      35  #include <errno.h>
      36  #include <sys/types.h>
      37  #include <sys/mman.h>
      38  #include <unistd.h>
      39  
      40  #include "backtrace.h"
      41  #include "internal.h"
      42  
      43  #ifndef HAVE_DECL_GETPAGESIZE
      44  extern int getpagesize (void);
      45  #endif
      46  
      47  #ifndef MAP_FAILED
      48  #define MAP_FAILED ((void *)-1)
      49  #endif
      50  
      51  /* This file implements file views and memory allocation when mmap is
      52     available.  */
      53  
      54  /* Create a view of SIZE bytes from DESCRIPTOR at OFFSET.  */
      55  
      56  int
      57  backtrace_get_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
      58  		    int descriptor, off_t offset, uint64_t size,
      59  		    backtrace_error_callback error_callback,
      60  		    void *data, struct backtrace_view *view)
      61  {
      62    size_t pagesize;
      63    unsigned int inpage;
      64    off_t pageoff;
      65    void *map;
      66  
      67    if ((uint64_t) (size_t) size != size)
      68      {
      69        error_callback (data, "file size too large", 0);
      70        return 0;
      71      }
      72  
      73    pagesize = getpagesize ();
      74    inpage = offset % pagesize;
      75    pageoff = offset - inpage;
      76  
      77    size += inpage;
      78    size = (size + (pagesize - 1)) & ~ (pagesize - 1);
      79  
      80    map = mmap (NULL, size, PROT_READ, MAP_PRIVATE, descriptor, pageoff);
      81    if (map == MAP_FAILED)
      82      {
      83        error_callback (data, "mmap", errno);
      84        return 0;
      85      }
      86  
      87    view->data = (char *) map + inpage;
      88    view->base = map;
      89    view->len = size;
      90  
      91    return 1;
      92  }
      93  
      94  /* Release a view read by backtrace_get_view.  */
      95  
      96  void
      97  backtrace_release_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
      98  			struct backtrace_view *view,
      99  			backtrace_error_callback error_callback,
     100  			void *data)
     101  {
     102    union {
     103      const void *cv;
     104      void *v;
     105    } const_cast;
     106  
     107    const_cast.cv = view->base;
     108    if (munmap (const_cast.v, view->len) < 0)
     109      error_callback (data, "munmap", errno);
     110  }