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1/*2 * Copyright (c) 2024 Alexey Dobriyan <adobriyan@gmail.com>3 *4 * Permission to use, copy, modify, and distribute this software for any5 * purpose with or without fee is hereby granted, provided that the above6 * copyright notice and this permission notice appear in all copies.7 *8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.15 */16/* Test that kernel thread is reported as such. */17#undef NDEBUG18#include <assert.h>19#include <errno.h>20#include <fcntl.h>21#include <string.h>22#include <unistd.h>23 24int main(void)25{26 /*27 * The following solutions don't really work:28 *29 * 1) jit kernel module which creates kernel thread:30 * test becomes arch-specific,31 * problems with mandatory module signing,32 * problems with lockdown mode,33 * doesn't work with CONFIG_MODULES=n at all,34 * kthread creation API is formally unstable internal kernel API,35 * need a mechanism to report test kernel thread's PID back,36 *37 * 2) ksoftirqd/0 and kswapd0 look like stable enough kernel threads,38 * but their PIDs are unstable.39 *40 * Check against kthreadd which always seem to exist under pid 2.41 */42 int fd = open("/proc/2/status", O_RDONLY);43 assert(fd >= 0);44 45 char buf[4096];46 ssize_t rv = read(fd, buf, sizeof(buf));47 assert(0 <= rv && rv < sizeof(buf));48 buf[rv] = '\0';49 50 assert(strstr(buf, "Kthread:\t1\n"));51 52 return 0;53}54