pstree.c

#include <sys/mman.h>
#include <unistd.h>
#include <stdlib.h>
#include <sched.h>

#include "cr_options.h"
#include "pstree.h"
#include "rst-malloc.h"
#include "lock.h"
#include "namespaces.h"
#include "files.h"
#include "tty.h"
#include "mount.h"
#include "asm/dump.h"

#include "protobuf.h"
#include "images/pstree.pb-c.h"

struct pstree_item *root_item;
static struct rb_root pid_root_rb;

void core_entry_free(CoreEntry *core)
{
	if (core->tc && core->tc->timers)
		xfree(core->tc->timers->posix);
	if (core->thread_core)
		xfree(core->thread_core->creds->groups);
	arch_free_thread_info(core);
	xfree(core);
}

#ifndef RLIM_NLIMITS
# define RLIM_NLIMITS 16
#endif

CoreEntry *core_entry_alloc(int th, int tsk)
{
	size_t sz;
	CoreEntry *core = NULL;
	void *m;

	sz = sizeof(CoreEntry);
	if (tsk) {
		sz += sizeof(TaskCoreEntry) + TASK_COMM_LEN;
		if (th) {
			sz += sizeof(TaskRlimitsEntry);
			sz += RLIM_NLIMITS * sizeof(RlimitEntry *);
			sz += RLIM_NLIMITS * sizeof(RlimitEntry);
			sz += sizeof(TaskTimersEntry);
			sz += 3 * sizeof(ItimerEntry); /* 3 for real, virt and prof */
		}
	}
	if (th) {
		CredsEntry *ce = NULL;

		sz += sizeof(ThreadCoreEntry) + sizeof(ThreadSasEntry) + sizeof(CredsEntry);

		sz += CR_CAP_SIZE * sizeof(ce->cap_inh[0]);
		sz += CR_CAP_SIZE * sizeof(ce->cap_prm[0]);
		sz += CR_CAP_SIZE * sizeof(ce->cap_eff[0]);
		sz += CR_CAP_SIZE * sizeof(ce->cap_bnd[0]);
		/*
		 * @groups are dynamic and allocated
		 * on demand.
		 */
	}

	m = xmalloc(sz);
	if (m) {
		core = xptr_pull(&m, CoreEntry);
		core_entry__init(core);
		core->mtype = CORE_ENTRY__MARCH;

		if (tsk) {
			core->tc = xptr_pull(&m, TaskCoreEntry);
			task_core_entry__init(core->tc);
			core->tc->comm = xptr_pull_s(&m, TASK_COMM_LEN);
			memzero(core->tc->comm, TASK_COMM_LEN);

			if (th) {
				TaskRlimitsEntry *rls;
				TaskTimersEntry *tte;
				int i;

				rls = core->tc->rlimits = xptr_pull(&m, TaskRlimitsEntry);
				task_rlimits_entry__init(rls);

				rls->n_rlimits = RLIM_NLIMITS;
				rls->rlimits = xptr_pull_s(&m, sizeof(RlimitEntry *) * RLIM_NLIMITS);

				for (i = 0; i < RLIM_NLIMITS; i++) {
					rls->rlimits[i] = xptr_pull(&m, RlimitEntry);
					rlimit_entry__init(rls->rlimits[i]);
				}

				tte = core->tc->timers = xptr_pull(&m, TaskTimersEntry);
				task_timers_entry__init(tte);
				tte->real = xptr_pull(&m, ItimerEntry);
				itimer_entry__init(tte->real);
				tte->virt = xptr_pull(&m, ItimerEntry);
				itimer_entry__init(tte->virt);
				tte->prof = xptr_pull(&m, ItimerEntry);
				itimer_entry__init(tte->prof);
			}
		}

		if (th) {
			CredsEntry *ce;

			core->thread_core = xptr_pull(&m, ThreadCoreEntry);
			thread_core_entry__init(core->thread_core);
			core->thread_core->sas = xptr_pull(&m, ThreadSasEntry);
			thread_sas_entry__init(core->thread_core->sas);
			ce = core->thread_core->creds = xptr_pull(&m, CredsEntry);
			creds_entry__init(ce);

			ce->n_cap_inh	= CR_CAP_SIZE;
			ce->n_cap_prm	= CR_CAP_SIZE;
			ce->n_cap_eff	= CR_CAP_SIZE;
			ce->n_cap_bnd	= CR_CAP_SIZE;
			ce->cap_inh	= xptr_pull_s(&m, CR_CAP_SIZE * sizeof(ce->cap_inh[0]));
			ce->cap_prm	= xptr_pull_s(&m, CR_CAP_SIZE * sizeof(ce->cap_prm[0]));
			ce->cap_eff	= xptr_pull_s(&m, CR_CAP_SIZE * sizeof(ce->cap_eff[0]));
			ce->cap_bnd	= xptr_pull_s(&m, CR_CAP_SIZE * sizeof(ce->cap_bnd[0]));

			if (arch_alloc_thread_info(core)) {
				xfree(core);
				core = NULL;
			}
		}
	}

	return core;
}

int pstree_alloc_cores(struct pstree_item *item)
{
	unsigned int i;

	item->core = xzalloc(sizeof(*item->core) * item->nr_threads);
	if (!item->core)
		return -1;

	for (i = 0; i < item->nr_threads; i++) {
		if (item->threads[i].real == item->pid.real)
			item->core[i] = core_entry_alloc(1, 1);
		else
			item->core[i] = core_entry_alloc(1, 0);

		if (!item->core[i])
			goto err;
	}

	return 0;
err:
	pstree_free_cores(item);
	return -1;
}

void pstree_free_cores(struct pstree_item *item)
{
	unsigned int i;

	if (item->core) {
		for (i = 1; i < item->nr_threads; i++)
			if (item->core[i])
				core_entry_free(item->core[i]);
		xfree(item->core);
		item->core = NULL;
	}
}

void free_pstree(struct pstree_item *root_item)
{
	struct pstree_item *item = root_item, *parent;

	while (item) {
		if (!list_empty(&item->children)) {
			item = list_first_entry(&item->children, struct pstree_item, sibling);
			continue;
		}

		parent = item->parent;
		list_del(&item->sibling);
		pstree_free_cores(item);
		xfree(item->threads);
		xfree(item);
		item = parent;
	}
}

struct pstree_item *__alloc_pstree_item(bool rst)
{
	struct pstree_item *item;
	int sz;

	if (!rst) {
		sz = sizeof(*item) + sizeof(struct dmp_info);
		item = xzalloc(sz);
		if (!item)
			return NULL;
	} else {
		sz = sizeof(*item) + sizeof(struct rst_info);
		item = shmalloc(sz);
		if (!item)
			return NULL;

		memset(item, 0, sz);
		vm_area_list_init(&rsti(item)->vmas);
	}

	INIT_LIST_HEAD(&item->children);
	INIT_LIST_HEAD(&item->sibling);

	item->pid.virt = -1;
	item->pid.real = -1;
	item->born_sid = -1;

	return item;
}

void init_pstree_helper(struct pstree_item *ret)
{
	ret->pid.state = TASK_HELPER;
	rsti(ret)->clone_flags = CLONE_FILES | CLONE_FS;
	task_entries->nr_helpers++;
}

/* Deep first search on children */
struct pstree_item *pstree_item_next(struct pstree_item *item)
{
	if (!list_empty(&item->children))
		return list_first_entry(&item->children, struct pstree_item, sibling);

	while (item->parent) {
		if (item->sibling.next != &item->parent->children)
			return list_entry(item->sibling.next, struct pstree_item, sibling);
		item = item->parent;
	}

	return NULL;
}

/* Preorder traversal of pstree item */
int preorder_pstree_traversal(struct pstree_item *item, int (*f)(struct pstree_item *))
{
	struct pstree_item *cursor;

	if (f(item) < 0)
		return -1;

	list_for_each_entry(cursor, &item->children, sibling) {
		if (preorder_pstree_traversal(cursor, f) < 0)
			return -1;
	}

	return 0;
}

int dump_pstree(struct pstree_item *root_item)
{
	struct pstree_item *item = root_item;
	PstreeEntry e = PSTREE_ENTRY__INIT;
	int ret = -1, i;
	struct cr_img *img;

	pr_info("\n");
	pr_info("Dumping pstree (pid: %d)\n", root_item->pid.real);
	pr_info("----------------------------------------\n");

	/*
	 * Make sure we're dumping session leader, if not an
	 * appropriate option must be passed.
	 *
	 * Also note that if we're not a session leader we
	 * can't get the situation where the leader sits somewhere
	 * deeper in process tree, thus top-level checking for
	 * leader is enough.
	 */
	if (root_item->pid.virt != root_item->sid) {
		if (!opts.shell_job) {
			pr_err("The root process %d is not a session leader. "
			       "Consider using --" OPT_SHELL_JOB " option\n", item->pid.virt);
			return -1;
		}
	}

	img = open_image(CR_FD_PSTREE, O_DUMP);
	if (!img)
		return -1;

	for_each_pstree_item(item) {
		pr_info("Process: %d(%d)\n", item->pid.virt, item->pid.real);

		e.pid		= item->pid.virt;
		e.ppid		= item->parent ? item->parent->pid.virt : 0;
		e.pgid		= item->pgid;
		e.sid		= item->sid;
		e.n_threads	= item->nr_threads;

		e.threads = xmalloc(sizeof(e.threads[0]) * e.n_threads);
		if (!e.threads)
			goto err;

		for (i = 0; i < item->nr_threads; i++)
			e.threads[i] = item->threads[i].virt;

		ret = pb_write_one(img, &e, PB_PSTREE);
		xfree(e.threads);

		if (ret)
			goto err;
	}
	ret = 0;

err:
	pr_info("----------------------------------------\n");
	close_image(img);
	return ret;
}

static int prepare_pstree_for_shell_job(void)
{
	pid_t current_sid = getsid(getpid());
	pid_t current_gid = getpgid(getpid());

	struct pstree_item *pi;

	pid_t old_sid;
	pid_t old_gid;

	if (!opts.shell_job)
		return 0;

	if (root_item->sid == root_item->pid.virt)
		return 0;

	/*
	 * Migration of a root task group leader is a bit tricky.
	 * When a task yields SIGSTOP, the kernel notifies the parent
	 * with SIGCHLD. This means when task is running in a
	 * shell, the shell obtains SIGCHLD and sends a task to
	 * the background.
	 *
	 * The situation gets changed once we restore the
	 * program -- our tool become an additional stub between
	 * the restored program and the shell. So to be able to
	 * notify the shell with SIGCHLD from our restored
	 * program -- we make the root task to inherit the
	 * process group from us.
	 *
	 * Not that clever solution but at least it works.
	 */

	old_sid = root_item->sid;
	old_gid = root_item->pgid;

	pr_info("Migrating process tree (GID %d->%d SID %d->%d)\n",
		old_gid, current_gid, old_sid, current_sid);

	for_each_pstree_item(pi) {
		if (pi->pgid == old_gid)
			pi->pgid = current_gid;
		if (pi->sid == old_sid)
			pi->sid = current_sid;
	}

	if (lookup_create_item(current_sid) == NULL)
		return -1;
	if (lookup_create_item(current_gid) == NULL)
		return -1;

	return 0;
}

/*
 * Try to find a pid node in the tree and insert a new one,
 * it is not there yet. If pid_node isn't set, pstree_item
 * is inserted.
 */
static struct pid *lookup_create_pid(pid_t pid, struct pid *pid_node)
{
	struct rb_node *node = pid_root_rb.rb_node;
	struct rb_node **new = &pid_root_rb.rb_node;
	struct rb_node *parent = NULL;

	while (node) {
		struct pid *this = rb_entry(node, struct pid, node);

		parent = *new;
		if (pid < this->virt)
			node = node->rb_left, new = &((*new)->rb_left);
		else if (pid > this->virt)
			node = node->rb_right, new = &((*new)->rb_right);
		else
			return this;
	}

	if (!pid_node) {
		struct pstree_item *item;

		item = __alloc_pstree_item(true);
		if (item == NULL)
			return NULL;

		item->pid.virt = pid;
		pid_node = &item->pid;
	}
	rb_link_and_balance(&pid_root_rb, &pid_node->node, parent, new);
	return pid_node;
}

void pstree_insert_pid(pid_t pid, struct pid *pid_node)
{
	struct pid* n;

	n = lookup_create_pid(pid, pid_node);

	BUG_ON(n != pid_node);
}

struct pstree_item *lookup_create_item(pid_t pid)
{
	struct pid *node;;

	node = lookup_create_pid(pid, NULL);
	if (!node)
		return NULL;
	BUG_ON(node->state == TASK_THREAD);

	return container_of(node, struct pstree_item, pid);
}

struct pid *pstree_pid_by_virt(pid_t pid)
{
	struct rb_node *node = pid_root_rb.rb_node;

	while (node) {
		struct pid *this = rb_entry(node, struct pid, node);

		if (pid < this->virt)
			node = node->rb_left;
		else if (pid > this->virt)
			node = node->rb_right;
		else
			return this;
	}
	return NULL;
}

static int read_pstree_ids(struct pstree_item *pi)
{
	int ret;
	struct cr_img *img;

	img = open_image(CR_FD_IDS, O_RSTR, pi->pid.virt);
	if (!img)
		return -1;

	ret = pb_read_one_eof(img, &pi->ids, PB_IDS);
	close_image(img);

	if (ret <= 0)
		return ret;

	if (pi->ids->has_mnt_ns_id) {
		if (rst_add_ns_id(pi->ids->mnt_ns_id, pi, &mnt_ns_desc))
			return -1;
	}

	return 0;
}

static int read_pstree_image(pid_t *pid_max)
{
	int ret = 0, i;
	struct cr_img *img;
	struct pstree_item *pi;

	pr_info("Reading image tree\n");

	img = open_image(CR_FD_PSTREE, O_RSTR);
	if (!img)
		return -1;

	while (1) {
		PstreeEntry *e;

		ret = pb_read_one_eof(img, &e, PB_PSTREE);
		if (ret <= 0)
			break;

		ret = -1;
		pi = lookup_create_item(e->pid);
		if (pi == NULL)
			break;
		BUG_ON(pi->pid.state != TASK_UNDEF);

		/*
		 * All pids should be added in the tree to be able to find
		 * free pid-s for helpers. pstree_item for these pid-s will
		 * be initialized when we meet PstreeEntry with this pid or
		 * we will create helpers for them.
		 */
		if (lookup_create_item(e->pgid) == NULL)
			break;
		if (lookup_create_item(e->sid) == NULL)
			break;

		pi->pid.virt = e->pid;
		if (e->pid > *pid_max)
			*pid_max = e->pid;
		pi->pgid = e->pgid;
		if (e->pgid > *pid_max)
			*pid_max = e->pgid;
		pi->sid = e->sid;
		if (e->sid > *pid_max)
			*pid_max = e->sid;
		pi->pid.state = TASK_ALIVE;

		if (e->ppid == 0) {
			if (root_item) {
				pr_err("Parent missed on non-root task "
				       "with pid %d, image corruption!\n", e->pid);
				goto err;
			}
			root_item = pi;
			pi->parent = NULL;
		} else {
			struct pid *pid;
			struct pstree_item *parent;

			pid = pstree_pid_by_virt(e->ppid);
			if (!pid || pid->state == TASK_UNDEF || pid->state == TASK_THREAD) {
				pr_err("Can't find a parent for %d\n", pi->pid.virt);
				pstree_entry__free_unpacked(e, NULL);
				xfree(pi);
				goto err;
			}

			parent = container_of(pid, struct pstree_item, pid);
			pi->parent = parent;
			list_add(&pi->sibling, &parent->children);
		}

		pi->nr_threads = e->n_threads;
		pi->threads = xmalloc(e->n_threads * sizeof(struct pid));
		if (!pi->threads)
			break;

		for (i = 0; i < e->n_threads; i++) {
			struct pid *node;
			pi->threads[i].real = -1;
			pi->threads[i].virt = e->threads[i];
			pi->threads[i].state = TASK_THREAD;
			if (i == 0)
				continue; /* A thread leader is in a tree already */
			node = lookup_create_pid(pi->threads[i].virt, &pi->threads[i]);

			BUG_ON(node == NULL);
			if (node != &pi->threads[i]) {
				pr_err("Unexpected task %d in a tree %d\n", e->threads[i], i);
				return -1;
			}
		}

		task_entries->nr_threads += e->n_threads;
		task_entries->nr_tasks++;

		pstree_entry__free_unpacked(e, NULL);

		ret = read_pstree_ids(pi);
		if (ret < 0)
			goto err;
	}

err:
	close_image(img);
	return ret;
}

#define RESERVED_PIDS           300
static int get_free_pid()
{
	static struct pstree_item *prev, *next;

	if (prev == NULL)
		prev = rb_entry(rb_first(&pid_root_rb), struct pstree_item, pid.node);

	while (1) {
		struct rb_node *node;
		pid_t pid;

		pid = prev->pid.virt + 1;
		pid = pid < RESERVED_PIDS ? RESERVED_PIDS + 1 : pid;

		node = rb_next(&prev->pid.node);
		if (node == NULL)
			return pid;
		next = rb_entry(node, struct pstree_item, pid.node);
		if (next->pid.virt > pid)
			return pid;
		prev = next;
	}

	return -1;
}

static int prepare_pstree_ids(void)
{
	struct pstree_item *item, *child, *helper, *tmp;
	LIST_HEAD(helpers);

	pid_t current_pgid = getpgid(getpid());

	/*
	 * Some task can be reparented to init. A helper task should be added
	 * for restoring sid of such tasks. The helper tasks will be exited
	 * immediately after forking children and all children will be
	 * reparented to init.
	 */
	list_for_each_entry(item, &root_item->children, sibling) {
		struct pstree_item *leader;

		/*
		 * If a child belongs to the root task's session or it's
		 * a session leader himself -- this is a simple case, we
		 * just proceed in a normal way.
		 */
		if (item->sid == root_item->sid || item->sid == item->pid.virt)
			continue;

		leader = pstree_item_by_virt(item->sid);
		BUG_ON(leader == NULL);
		if (leader->pid.state != TASK_UNDEF) {
			pid_t pid;

			pid = get_free_pid();
			if (pid < 0)
				break;
			helper = lookup_create_item(pid);
			if (helper == NULL)
				return -1;

			pr_info("Session leader %d\n", item->sid);

			helper->sid = item->sid;
			helper->pgid = leader->pgid;
			helper->ids = leader->ids;
			helper->parent = leader;
			list_add(&helper->sibling, &leader->children);

			pr_info("Attach %d to the task %d\n",
					helper->pid.virt, leader->pid.virt);
		} else {
			helper = leader;
			helper->sid = item->sid;
			helper->pgid = item->sid;
			helper->parent = root_item;
			helper->ids = root_item->ids;
			list_add_tail(&helper->sibling, &helpers);
		}
		init_pstree_helper(helper);

		pr_info("Add a helper %d for restoring SID %d\n",
				helper->pid.virt, helper->sid);

		child = list_entry(item->sibling.prev, struct pstree_item, sibling);
		item = child;

		/*
		 * Stack on helper task all children with target sid.
		 */
		list_for_each_entry_safe_continue(child, tmp, &root_item->children, sibling) {
			if (child->sid != helper->sid)
				continue;
			if (child->sid == child->pid.virt)
				continue;

			pr_info("Attach %d to the temporary task %d\n",
					child->pid.virt, helper->pid.virt);

			child->parent = helper;
			list_move(&child->sibling, &helper->children);
		}
	}

	/* Try to connect helpers to session leaders */
	for_each_pstree_item(item) {
		if (!item->parent) /* skip the root task */
			continue;

		if (item->pid.state == TASK_HELPER)
			continue;

		if (item->sid != item->pid.virt) {
			struct pstree_item *parent;

			if (item->parent->sid == item->sid)
				continue;

			/* the task could fork a child before and after setsid() */
			parent = item->parent;
			while (parent && parent->pid.virt != item->sid) {
				if (parent->born_sid != -1 && parent->born_sid != item->sid) {
					pr_err("Can't determinate with which sid (%d or %d)"
						"the process %d was born\n",
						parent->born_sid, item->sid, parent->pid.virt);
					return -1;
				}
				parent->born_sid = item->sid;
				pr_info("%d was born with sid %d\n", parent->pid.virt, item->sid);
				parent = parent->parent;
			}

			if (parent == NULL) {
				pr_err("Can't find a session leader for %d\n", item->sid);
				return -1;
			}

			continue;
		}
	}

	/* All other helpers are session leaders for own sessions */
	list_splice(&helpers, &root_item->children);

	/* Add a process group leader if it is absent  */
	for_each_pstree_item(item) {
		struct pid *pid;

		if (!item->pgid || item->pid.virt == item->pgid)
			continue;

		pid = pstree_pid_by_virt(item->pgid);
		if (pid->state != TASK_UNDEF) {
			BUG_ON(pid->state == TASK_THREAD);
			rsti(item)->pgrp_leader = container_of(pid, struct pstree_item, pid);
			continue;
		}

		/*
		 * If the PGID is eq to current one -- this
		 * means we're inheriting group from the current
		 * task so we need to escape creating a helper here.
		 */
		if (current_pgid == item->pgid)
			continue;

		helper = container_of(pid, struct pstree_item, pid);
		init_pstree_helper(helper);

		helper->sid = item->sid;
		helper->pgid = item->pgid;
		helper->pid.virt = item->pgid;
		helper->parent = item;
		helper->ids = item->ids;
		list_add(&helper->sibling, &item->children);
		rsti(item)->pgrp_leader = helper;

		pr_info("Add a helper %d for restoring PGID %d\n",
				helper->pid.virt, helper->pgid);
	}

	return 0;
}

static unsigned long get_clone_mask(TaskKobjIdsEntry *i,
		TaskKobjIdsEntry *p)
{
	unsigned long mask = 0;

	if (i->files_id == p->files_id)
		mask |= CLONE_FILES;
	if (i->pid_ns_id != p->pid_ns_id)
		mask |= CLONE_NEWPID;
	if (i->net_ns_id != p->net_ns_id)
		mask |= CLONE_NEWNET;
	if (i->ipc_ns_id != p->ipc_ns_id)
		mask |= CLONE_NEWIPC;
	if (i->uts_ns_id != p->uts_ns_id)
		mask |= CLONE_NEWUTS;
	if (i->mnt_ns_id != p->mnt_ns_id)
		mask |= CLONE_NEWNS;
	if (i->user_ns_id != p->user_ns_id)
		mask |= CLONE_NEWUSER;

	return mask;
}

static int prepare_pstree_kobj_ids(void)
{
	struct pstree_item *item;

	/* Find a process with minimal pid for shared fd tables */
	for_each_pstree_item(item) {
		struct pstree_item *parent = item->parent;
		TaskKobjIdsEntry *ids;
		unsigned long cflags;

		if (!item->ids) {
			if (item == root_item) {
				pr_err("No IDS for root task.\n");
				pr_err("Images currupted or too old criu was used for dump.\n");
				return -1;
			}

			continue;
		}

		if (parent)
			ids = parent->ids;
		else
			ids = root_ids;

		/*
		 * Add some sanity check on image data.
		 */
		if (unlikely(!ids)) {
			pr_err("No kIDs provided, image corruption\n");
			return -1;
		}

		cflags = get_clone_mask(item->ids, ids);

		if (cflags & CLONE_FILES) {
			int ret;

			/*
			 * There might be a case when kIDs for
			 * root task are the same as in root_ids,
			 * thus it's image corruption and we should
			 * exit out.
			 */
			if (unlikely(!item->parent)) {
				pr_err("Image corruption on kIDs data\n");
				return -1;
			}

			ret = shared_fdt_prepare(item);
			if (ret)
				return ret;
		}

		rsti(item)->clone_flags = cflags;
		if (parent)
			/*
			 * Mount namespaces are setns()-ed at
			 * restore_task_mnt_ns() explicitly,
			 * no need in creating it with its own
			 * temporary namespace.
			 *
			 * Root task is exceptional -- it will
			 * be born in a fresh new mount namespace
			 * which will be populated with all other
			 * namespaces' entries.
			 */
			rsti(item)->clone_flags &= ~CLONE_NEWNS;

		cflags &= CLONE_ALLNS;

		if (item == root_item) {
			pr_info("Will restore in %lx namespaces\n", cflags);
			root_ns_mask = cflags;
		} else if (cflags & ~(root_ns_mask & CLONE_SUBNS)) {
			/*
			 * Namespaces from CLONE_SUBNS can be nested, but in
			 * this case nobody can't share external namespaces of
			 * these types.
			 *
			 * Workaround for all other namespaces --
			 * all tasks should be in one namespace. And
			 * this namespace is either inherited from the
			 * criu or is created for the init task (only)
			 */
			pr_err("Can't restore sub-task in NS\n");
			return -1;
		}
	}

	pr_debug("NS mask to use %lx\n", root_ns_mask);
	return 0;
}

int prepare_pstree(void)
{
	int ret;
	pid_t pid_max = 0, kpid_max = 0;
	int fd;
	char buf[21];

	fd = open_proc(PROC_GEN, PID_MAX_PATH);
	if (fd >= 0) {
		ret = read(fd, buf, sizeof(buf) - 1);
		close(fd);
		if (ret > 0) {
			buf[ret] = 0;
			kpid_max = strtoul(buf, NULL, 10);
			pr_debug("kernel pid_max=%d\n", kpid_max);
		}
	}

	ret = read_pstree_image(&pid_max);
	pr_debug("pstree pid_max=%d\n", pid_max);

	if (!ret && kpid_max && pid_max > kpid_max) {
		/* Try to set kernel pid_max */
		fd = open_proc_rw(PROC_GEN, PID_MAX_PATH);
		if (fd == -1)
			ret = -1;
		else {
			snprintf(buf, sizeof(buf), "%u", pid_max+1);
			if (write(fd, buf, strlen(buf)) < 0) {
				pr_perror("Can't set kernel pid_max=%s", buf);
				ret = -1;
			}
			else
				pr_info("kernel pid_max pushed to %s\n", buf);
			close(fd);
		}
	}

	if (!ret)
		/*
		 * Shell job may inherit sid/pgid from the current
		 * shell, not from image. Set things up for this.
		 */
		ret = prepare_pstree_for_shell_job();
	if (!ret)
		/*
		 * Walk the collected tree and prepare for restoring
		 * of shared objects at clone time
		 */
		ret = prepare_pstree_kobj_ids();
	if (!ret)
		/*
		 * Session/Group leaders might be dead. Need to fix
		 * pstree with properly injected helper tasks.
		 */
		ret = prepare_pstree_ids();

	return ret;
}

bool restore_before_setsid(struct pstree_item *child)
{
	int csid = child->born_sid == -1 ? child->sid : child->born_sid;

	if (child->parent->born_sid == csid)
		return true;

	return false;
}

struct pstree_item *pstree_item_by_virt(pid_t virt)
{
	struct pid *pid;

	pid = pstree_pid_by_virt(virt);
	if (pid == NULL)
		return NULL;
	BUG_ON(pid->state == TASK_THREAD);

	return container_of(pid, struct pstree_item, pid);
}

struct pstree_item *pstree_item_by_real(pid_t real)
{
	struct pstree_item *item;

	for_each_pstree_item(item) {
		if (item->pid.real == real)
			return item;
	}
	return NULL;
}

int pid_to_virt(pid_t real)
{
	struct pstree_item *item;

	item = pstree_item_by_real(real);
	if (item)
		return item->pid.virt;
	return 0;
}