1 /* Allocate a memory region shared across processes.
2 Copyright (C) 2017-2022 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 <stddef.h>
21 #include <support/support.h>
22 #include <support/xunistd.h>
23 #include <sys/mman.h>
24
25 /* Header for the allocation. It contains the size of the allocation
26 for subsequent unmapping. */
27 struct header
28 {
29 size_t total_size;
30 char data[] __attribute__ ((aligned (__alignof__ (max_align_t))));
31 };
32
33 void *
support_shared_allocate(size_t size)34 support_shared_allocate (size_t size)
35 {
36 size_t total_size = size + offsetof (struct header, data);
37 if (total_size < size)
38 {
39 errno = ENOMEM;
40 oom_error (__func__, size);
41 return NULL;
42 }
43 else
44 {
45 struct header *result = xmmap (NULL, total_size, PROT_READ | PROT_WRITE,
46 MAP_ANONYMOUS | MAP_SHARED, -1);
47 result->total_size = total_size;
48 return &result->data;
49 }
50 }
51
52 void
support_shared_free(void * data)53 support_shared_free (void *data)
54 {
55 struct header *header = data - offsetof (struct header, data);
56 xmunmap (header, header->total_size);
57 }
58