1 /* 2 * Copyright (c) 2024 Alexey Dobriyan <adobriyan@gmail.com> 3 * 4 * Permission to use, copy, modify, and distribute this software for any 5 * purpose with or without fee is hereby granted, provided that the above 6 * copyright notice and this permission notice appear in all copies. 7 * 8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15 */ 16 /* Test that kernel thread is reported as such. */ 17 #undef NDEBUG 18 #include <assert.h> 19 #include <errno.h> 20 #include <fcntl.h> 21 #include <string.h> 22 #include <unistd.h> 23 24 int 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