tools/testing/selftests/proc/proc-self-isnt-kthread.c

/*
 * Copyright (c) 2024 Alexey Dobriyan <adobriyan@gmail.com>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
/* Test that userspace program is not kernel thread. */
#undef NDEBUG
#include <assert.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>

int main(void)
{
	int fd = open("/proc/self/status", O_RDONLY);
	assert(fd >= 0);

	char buf[4096];
	ssize_t rv = read(fd, buf, sizeof(buf));
	assert(0 <= rv && rv < sizeof(buf));
	buf[rv] = '\0';

	/* This test is very much not kernel thread. */
	assert(strstr(buf, "Kthread:\t0\n"));

	return 0;
}