Show pid in each pid namespaces

pid.stp

#!/usr/bin/env stap

%{
#include <linux/sched.h>
#include <linux/thread_info.h>
#include <linux/pid_namespace.h>
%}

function show_pidtree:long(pn:long) %{
        struct task_struct *task;
        int pid_nr = STAP_ARG_pn;
        struct pid_namespace *pid_ns;
        int indent_level = 0, i;

        struct pid *pid = find_get_pid(pid_nr);

        if (!pid) {
                STAP_PRINTF("Could not find  pid %d\n", pid_nr);
                STAP_RETURN(-1);
        }

        task = pid_task(pid, PIDTYPE_PID);
        if (!task) {
                STAP_PRINTF("Cannot find task by pid %d\n", pid_nr);
                STAP_RETURN(-1);
        }

        pid_ns = task->nsproxy->pid_ns_for_children;

        do {
                pid_nr = __task_pid_nr_ns(task, PIDTYPE_PID, pid_ns);
                for (i = 0; i < indent_level; i++)
                        STAP_PRINTF("  ");
                STAP_PRINTF("pid %d\n", pid_nr);
                pid_ns = pid_ns->parent;
                indent_level++;
        } while (pid_ns);

        STAP_RETURN(0);
%}

probe begin {
        /* pass pid that is command line argument */
        show_pidtree($1)
        exit()
}
probe end {
        printf("Done\n")
}