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proc: test "Kthread:" field

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/proc/${pid}/status got Kthread field recently.

Test that userspace program is not reported as kernel thread.

Test that kernel thread is reported as kernel thread.
Use kthreadd with pid 2 for this.

Link: https://lkml.kernel.org/r/818c4c41-8668-4566-97a9-7254abf819ee@p183
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Chunguang Wu <fullspring2018@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexey Dobriyan 2024-06-07 18:14:29 +03:00 committed by Andrew Morton
parent d0bff05405
commit e7679a5c82
4 changed files with 94 additions and 0 deletions
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2
tools/testing/selftests/proc/.gitignore vendored
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@ -2,6 +2,7 @@
/fd-001-lookup
/fd-002-posix-eq
/fd-003-kthread
/proc-2-is-kthread
/proc-fsconfig-hidepid
/proc-loadavg-001
/proc-multiple-procfs
@ -9,6 +10,7 @@
/proc-pid-vm
/proc-self-map-files-001
/proc-self-map-files-002
/proc-self-isnt-kthread
/proc-self-syscall
/proc-self-wchan
/proc-subset-pid

2
tools/testing/selftests/proc/Makefile
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@ -7,11 +7,13 @@ TEST_GEN_PROGS :=
TEST_GEN_PROGS += fd-001-lookup
TEST_GEN_PROGS += fd-002-posix-eq
TEST_GEN_PROGS += fd-003-kthread
TEST_GEN_PROGS += proc-2-is-kthread
TEST_GEN_PROGS += proc-loadavg-001
TEST_GEN_PROGS += proc-empty-vm
TEST_GEN_PROGS += proc-pid-vm
TEST_GEN_PROGS += proc-self-map-files-001
TEST_GEN_PROGS += proc-self-map-files-002
TEST_GEN_PROGS += proc-self-isnt-kthread
TEST_GEN_PROGS += proc-self-syscall
TEST_GEN_PROGS += proc-self-wchan
TEST_GEN_PROGS += proc-subset-pid

53
tools/testing/selftests/proc/proc-2-is-kthread.c Normal file
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@ -0,0 +1,53 @@
/*
* 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;
}

37
tools/testing/selftests/proc/proc-self-isnt-kthread.c Normal file
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@ -0,0 +1,37 @@
/*
* 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;
}