Since the introduction of CLONE_PIDFD pidfd_send_signal() is independent
of CONFIG_PROC_FS.

Signed-off-by: Christian Brauner <christian@brauner.io>

This adds testing for the new pidfd_open() syscalls. Specifically, we test:
- that no invalid flags can be passed to pidfd_open()
- that no invalid pid can be passed to pidfd_open()
- that a pidfd can be retrieved with pidfd_open()
- that the retrieved pidfd references the correct pid

Signed-off-by: Christian Brauner <christian@brauner.io>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jann Horn <jannh@google.com>
Cc: David Howells <dhowells@redhat.com>
Cc: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-api@vger.kernel.org

Other than verifying pidfd based polling, the tests make sure that
wait semantics are preserved with the pidfd poll. Notably the 2 cases:
1. If a thread group leader exits while threads still there, then no
   pidfd poll notifcation should happen.
2. If a non-thread group leader does an execve, then the thread group
   leader is signaled to exit and is replaced with the execing thread
   as the new leader, however the parent is not notified in this case.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Christian Brauner <christian@brauner.io>

Create ../selftests/pidfd/.gitignore which holds the following file name
created after compiling:

	- pidfd_test

Signed-off-by: Kelsey Skunberg <skunberg.kelsey@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

The test plan for TAP needs to be declared immediately after the header.
This adds the test plan API to kselftest.h and updates all callers to
declare their expected test counts.

Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

As suggested by Andrew Morton in [1] add selftests for the new
sys_pidfd_send_signal() syscall:

/* test_pidfd_send_signal_syscall_support */
Test whether the pidfd_send_signal() syscall is supported and the tests can
be run or need to be skipped.

/* test_pidfd_send_signal_simple_success */
Test whether sending a signal via a pidfd works.

/* test_pidfd_send_signal_exited_fail */
Verify that sending a signal to an already exited process fails with ESRCH.

/* test_pidfd_send_signal_recycled_pid_fail */
Verify that a recycled pid cannot be signaled via a pidfd referring to an
already exited process that had the same pid (cf. [2], [3]).

[1]: https://lore.kernel.org/lkml/20181228152012.dbf0508c2508138efc5f2bbe@linux-foundation.org/
[2]: https://lore.kernel.org/lkml/20181230210245.GA30252@mail.hallyn.com/
[3]: https://lore.kernel.org/lkml/20181230232711.7aayb7vnhogbv4co@brauner.io/

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Jann Horn <jannh@google.com>
Cc: Andy Lutomirsky <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Tycho Andersen <tycho@tycho.ws>
Acked-by: Serge Hallyn <serge@hallyn.com>