libbacktrace/mmapio.c

   1 /* mmapio.c -- File views using mmap.
   2    Copyright (C) 2012-2018 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 MAP_FAILED
  44 #define MAP_FAILED ((void *)-1)
  45 #endif
  46
  47 /* This file implements file views and memory allocation when mmap is
  48    available.  */
  49
  50 /* Create a view of SIZE bytes from DESCRIPTOR at OFFSET.  */
  51
  52 int
  53 backtrace_get_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
  54                     int descriptor, off_t offset, size_t size,
  55                     backtrace_error_callback error_callback,
  56                     void *data, struct backtrace_view *view)
  57 {
  58   size_t pagesize;
  59   unsigned int inpage;
  60   off_t pageoff;
  61   void *map;
  62
  63   pagesize = getpagesize ();
  64   inpage = offset % pagesize;
  65   pageoff = offset - inpage;
  66
  67   size += inpage;
  68   size = (size + (pagesize - 1)) & ~ (pagesize - 1);
  69
  70   map = mmap (NULL, size, PROT_READ, MAP_PRIVATE, descriptor, pageoff);
  71   if (map == MAP_FAILED)
  72     {
  73       error_callback (data, "mmap", errno);
  74       return 0;
  75     }
  76
  77   view->data = (char *) map + inpage;
  78   view->base = map;
  79   view->len = size;
  80
  81   return 1;
  82 }
  83
  84 /* Release a view read by backtrace_get_view.  */
  85
  86 void
  87 backtrace_release_view (struct backtrace_state *state ATTRIBUTE_UNUSED,
  88                         struct backtrace_view *view,
  89                         backtrace_error_callback error_callback,
  90                         void *data)
  91 {
  92   union {
  93     const void *cv;
  94     void *v;
  95   } const_cast;
  96
  97   const_cast.cv = view->base;
  98   if (munmap (const_cast.v, view->len) < 0)
  99     error_callback (data, "munmap", errno);
 100 }