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/*
* Find out the size of kernel's sigset_t.
*
* Copyright (c) 2016-2018 Dmitry V. Levin <ldv@strace.io>
* Copyright (c) 2017-2021 The strace developers.
* All rights reserved.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "tests.h"
#include <signal.h>
#include <unistd.h>
#include "scno.h"
/*
* If the sigset size specified to rt_sigprocmask is not equal to the size
* of kernel's sigset_t, the kernel does not look at anything else and fails
* with EINVAL.
*
* Otherwise, if both pointers specified to rt_sigprocmask are NULL,
* the kernel just returns 0.
*
* This vaguely documented kernel feature can be used to probe
* the kernel and find out the size of kernel's sigset_t.
*/
unsigned int
get_sigset_size(void)
{
static unsigned int set_size;
if (!set_size) {
static const unsigned int big_size = 1024 / 8;
for (set_size = big_size; set_size; set_size >>= 1) {
if (!syscall(__NR_rt_sigprocmask, SIG_SETMASK,
NULL, NULL, set_size))
break;
}
if (!set_size)
perror_msg_and_fail("rt_sigprocmask");
}
return set_size;
}
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