1 /*
2 * Find out the size of kernel's sigset_t.
3 *
4 * Copyright (c) 2016-2017 Dmitry V. Levin <ldv@altlinux.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
15 * 3. The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30 #include "tests.h"
31 #include <signal.h>
32 #include <unistd.h>
33 #include <asm/unistd.h>
34
35 /*
36 * If the sigset size specified to rt_sigprocmask is not equal to the size
37 * of kernel's sigset_t, the kernel does not look at anything else and fails
38 * with EINVAL.
39 *
40 * Otherwise, if both pointers specified to rt_sigprocmask are NULL,
41 * the kernel just returns 0.
42 *
43 * This vaguely documented kernel feature can be used to probe
44 * the kernel and find out the size of kernel's sigset_t.
45 */
46
47 unsigned int
get_sigset_size(void)48 get_sigset_size(void)
49 {
50 static unsigned int set_size;
51
52 if (!set_size) {
53 static const unsigned int big_size = 1024 / 8;
54
55 for (set_size = big_size; set_size; set_size >>= 1) {
56 if (!syscall(__NR_rt_sigprocmask, SIG_SETMASK,
57 NULL, NULL, set_size))
58 break;
59 }
60
61 if (!set_size)
62 perror_msg_and_fail("rt_sigprocmask");
63 }
64
65 return set_size;
66 }
67