1 /* 2 * Find out the size of kernel's sigset_t. 3 * 4 * Copyright (c) 2016-2017 Dmitry V. Levin <ldv (at) 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 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
