pidfd: add NSpid entries to fdinfo

}

#ifdef CONFIG_PROC_FS

/**

 * pidfd_show_fdinfo - print information about a pidfd

 * @m: proc fdinfo file

 * @f: file referencing a pidfd

 *

 * Pid:

 * This function will print the pid that a given pidfd refers to in the

 * pid namespace of the procfs instance.

 * If the pid namespace of the process is not a descendant of the pid

 * namespace of the procfs instance 0 will be shown as its pid. This is

 * similar to calling getppid() on a process whose parent is outside of

 * its pid namespace.

 *

 * NSpid:

 * If pid namespaces are supported then this function will also print

 * the pid of a given pidfd refers to for all descendant pid namespaces

 * starting from the current pid namespace of the instance, i.e. the

 * Pid field and the first entry in the NSpid field will be identical.

 * If the pid namespace of the process is not a descendant of the pid

 * namespace of the procfs instance 0 will be shown as its first NSpid

 * entry and no others will be shown.

 * Note that this differs from the Pid and NSpid fields in

 * /proc/<pid>/status where Pid and NSpid are always shown relative to

 * the  pid namespace of the procfs instance. The difference becomes

 * obvious when sending around a pidfd between pid namespaces from a

 * different branch of the tree, i.e. where no ancestoral relation is

 * present between the pid namespaces:

 * - create two new pid namespaces ns1 and ns2 in the initial pid

 *   namespace (also take care to create new mount namespaces in the

 *   new pid namespace and mount procfs)

 * - create a process with a pidfd in ns1

 * - send pidfd from ns1 to ns2

 * - read /proc/self/fdinfo/<pidfd> and observe that both Pid and NSpid

 *   have exactly one entry, which is 0

 */

static void pidfd_show_fdinfo(struct seq_file *m, struct file *f)

{

	struct pid_namespace *ns = proc_pid_ns(file_inode(m->file));

	struct pid *pid = f->private_data;

	pid_t nr = pid_nr_ns(pid, ns);

	seq_put_decimal_ull(m, "Pid:\t", nr);

	seq_put_decimal_ull(m, "Pid:\t", pid_nr_ns(pid, ns));

#ifdef CONFIG_PID_NS

	seq_put_decimal_ull(m, "\nNSpid:\t", nr);

	if (nr) {

		int i;

		/* If nr is non-zero it means that 'pid' is valid and that

		 * ns, i.e. the pid namespace associated with the procfs

		 * instance, is in the pid namespace hierarchy of pid.

		 * Start at one below the already printed level.

		 */

		for (i = ns->level + 1; i <= pid->level; i++)

			seq_put_decimal_ull(m, "\t", pid->numbers[i].nr);

	}

#endif

	seq_putc(m, '\n');

}

#endif