1/* mmapio.c -- File views using mmap.
2 Copyright (C) 2012-2025 Free Software Foundation, Inc.
3 Written by Ian Lance Taylor, Google.
4
5Redistribution and use in source and binary forms, with or without
6modification, are permitted provided that the following conditions are
7met:
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
21THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
23WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
24DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
25INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
26(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
27SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
29STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
30IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
31POSSIBILITY 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
44extern 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
56int
57backtrace_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, len: size, PROT_READ, MAP_PRIVATE, fd: descriptor, offset: 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
96void
97backtrace_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}
111

source code of libbacktrace/mmapio.c