The pidfd interface was extended with:
* PIDFD_GET_INFO and pidfd_info (along with related extra flags) to
allow get information about the process without the need to parse
/proc (commit cdda1f26e74ba, Linux 6.13).
* PIDFD_SELF_{THREAD,THREAD_GROUP,SELF,SELF_PROCESS} to allow
pidfd_send_signal refer to the own process or thread lead groups
without the need of allocating a file descriptor (commit f08d0c3a71114,
Linux 6.15).
* PIDFD_INFO_COREDUMP that extends PIDFD_GET_INFO to obtain coredump
information.
Linux uAPI header defines both PIDFD_SELF_THREAD and
PIDFD_SELF_THREAD_GROUP on linux/fcntl.h (since they reserve part of the
AT_* values), however for glibc I do not see any good reason to add pidfd
definitions on fcntl-linux.h.
The tst-pidfd.c is extended with some PIDFD_SELF_* tests and a new
‘tst-pidfd_getinfo.c’ test is added to check PIDFD_GET_INFO. The
PIDFD_INFO_COREDUMP tests would require very large and complex tests
that are already covered by kernel tests.
Checked on aarch64-linux-gnu and x86_64-linux-gnu on kernels 6.8 and
6.17.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Linux 6.11 adds some more PIDFD_* constants for 'pidfs: allow retrieval
of namespace file descriptors'
(5b08bd408534bfb3a7cf5778da5b27d4e4fffe12).
Tested with build-many-glibcs.py.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Linux 6.9 adds some more PIDFD_* constants. Add them to glibc's
sys/pidfd.h, including updating comments that said FLAGS was reserved
and must be 0, along with updating tst-pidfd-consts.py.
Tested with build-many-glibcs.py.
This interface allows to obtain the associated process ID from the
process file descriptor. It is done by parsing the procps fdinfo
information. Its prototype is:
pid_t pidfd_getpid (int fd)
It returns the associated pid or -1 in case of an error and sets the
errno accordingly. The possible errno values are those from open, read,
and close (used on procps parsing), along with:
- EBADF if the FD is negative, does not have a PID associated, or if
the fdinfo fields contain a value larger than pid_t.
- EREMOTE if the PID is in a separate namespace.
- ESRCH if the process is already terminated.
Checked on x86_64-linux-gnu on Linux 4.15 (no CLONE_PIDFD or waitid
support), Linux 5.4 (full support), and Linux 6.2.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
This was added on Linux 5.1(3eb39f47934f9d5a3027fe00d906a45fe3a15fad)
as a way to avoid the race condition of using kill (where PID might be
reused by the kernel between between obtaining the pid and sending the
signal).
If the siginfo_t argument is NULL then pidfd_send_signal is equivalent
to kill. If it is not NULL pidfd_send_signal is equivalent to
rt_sigqueueinfo.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This was added on Linux 5.6 (8649c322f75c96e7ced2fec201e123b2b073bf09)
as a way to retrieve a file descriptors for another process though
pidfd (created either with CLONE_PIDFD or pidfd_getfd). The
functionality is similar to recvmmsg SCM_RIGHTS.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
This was added on Linux 5.3 (32fcb426ec001cb6d5a4a195091a8486ea77e2df)
as a way to retrieve a pid file descriptors for process that has not
been created CLONE_PIDFD (by usual fork/clone).
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>
