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
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