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/*
* 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 kernel thread is reported as such. */
#undef NDEBUG
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
int main(void)
{
/*
* The following solutions don't really work:
*
* 1) jit kernel module which creates kernel thread:
* test becomes arch-specific,
* problems with mandatory module signing,
* problems with lockdown mode,
* doesn't work with CONFIG_MODULES=n at all,
* kthread creation API is formally unstable internal kernel API,
* need a mechanism to report test kernel thread's PID back,
*
* 2) ksoftirqd/0 and kswapd0 look like stable enough kernel threads,
* but their PIDs are unstable.
*
* Check against kthreadd which always seem to exist under pid 2.
*/
int fd = open("/proc/2/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';
assert(strstr(buf, "Kthread:\t1\n"));
return 0;
}
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