/*
   * taskstats.c - Export per-task statistics to userland
   *
   * Copyright (C) Shailabh Nagar, IBM Corp. 2006
   *           (C) Balbir Singh,   IBM Corp. 2006
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   */
  
  #include <linux/kernel.h>
  #include <linux/taskstats_kern.h>

  #include <linux/tsacct_kern.h>

  #include <linux/delayacct.h>

  #include <linux/cpumask.h>
  #include <linux/percpu.h>

  #include <linux/slab.h>

  #include <linux/cgroupstats.h>
  #include <linux/cgroup.h>
  #include <linux/fs.h>
  #include <linux/file.h>

  #include <linux/pid_namespace.h>

  #include <net/genetlink.h>

  #include <linux/atomic.h>

  #include <linux/sched/cputime.h>

  /*
   * Maximum length of a cpumask that can be specified in
   * the TASKSTATS_CMD_ATTR_REGISTER/DEREGISTER_CPUMASK attribute
   */
  #define TASKSTATS_CPUMASK_MAXLEN	(100+6*NR_CPUS)

  static DEFINE_PER_CPU(__u32, taskstats_seqnum);

  static int family_registered;

  struct kmem_cache *taskstats_cache;

  static struct genl_family family;

  static const struct nla_policy taskstats_cmd_get_policy[TASKSTATS_CMD_ATTR_MAX+1] = {

  	[TASKSTATS_CMD_ATTR_PID]  = { .type = NLA_U32 },
  	[TASKSTATS_CMD_ATTR_TGID] = { .type = NLA_U32 },

  	[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK] = { .type = NLA_STRING },
  	[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK] = { .type = NLA_STRING },};

  /*
   * We have to use TASKSTATS_CMD_ATTR_MAX here, it is the maxattr in the family.
   * Make sure they are always aligned.
   */
  static const struct nla_policy cgroupstats_cmd_get_policy[TASKSTATS_CMD_ATTR_MAX+1] = {

  	[CGROUPSTATS_CMD_ATTR_FD] = { .type = NLA_U32 },
  };

  struct listener {
  	struct list_head list;
  	pid_t pid;

  	char valid;

  };

  struct listener_list {
  	struct rw_semaphore sem;
  	struct list_head list;
  };
  static DEFINE_PER_CPU(struct listener_list, listener_array);
  
  enum actions {
  	REGISTER,
  	DEREGISTER,
  	CPU_DONT_CARE
  };

  
  static int prepare_reply(struct genl_info *info, u8 cmd, struct sk_buff **skbp,

  				size_t size)

  {
  	struct sk_buff *skb;
  	void *reply;
  
  	/*
  	 * If new attributes are added, please revisit this allocation
  	 */

  	skb = genlmsg_new(size, GFP_KERNEL);

  	if (!skb)
  		return -ENOMEM;
  
  	if (!info) {

  		int seq = this_cpu_inc_return(taskstats_seqnum) - 1;

  		reply = genlmsg_put(skb, 0, seq, &family, 0, cmd);

  	} else

  		reply = genlmsg_put_reply(skb, info, &family, 0, cmd);

  	if (reply == NULL) {
  		nlmsg_free(skb);
  		return -EINVAL;
  	}
  
  	*skbp = skb;

  	return 0;
  }

  /*
   * Send taskstats data in @skb to listener with nl_pid @pid
   */

  static int send_reply(struct sk_buff *skb, struct genl_info *info)

  {

  	struct genlmsghdr *genlhdr = nlmsg_data(nlmsg_hdr(skb));

  	void *reply = genlmsg_data(genlhdr);

  	genlmsg_end(skb, reply);

  	return genlmsg_reply(skb, info);

  }

  /*
   * Send taskstats data in @skb to listeners registered for @cpu's exit data
   */

  static void send_cpu_listeners(struct sk_buff *skb,
  					struct listener_list *listeners)

  {

  	struct genlmsghdr *genlhdr = nlmsg_data(nlmsg_hdr(skb));

  	struct listener *s, *tmp;
  	struct sk_buff *skb_next, *skb_cur = skb;
  	void *reply = genlmsg_data(genlhdr);

  	int rc, delcount = 0;

  	genlmsg_end(skb, reply);

  
  	rc = 0;

  	down_read(&listeners->sem);

  	list_for_each_entry(s, &listeners->list, list) {

  		skb_next = NULL;
  		if (!list_is_last(&s->list, &listeners->list)) {
  			skb_next = skb_clone(skb_cur, GFP_KERNEL);

  			if (!skb_next)

  				break;

  		}

  		rc = genlmsg_unicast(&init_net, skb_cur, s->pid);

  		if (rc == -ECONNREFUSED) {

  			s->valid = 0;
  			delcount++;

  		}
  		skb_cur = skb_next;
  	}

  	up_read(&listeners->sem);

  	if (skb_cur)
  		nlmsg_free(skb_cur);

  	if (!delcount)

  		return;

  
  	/* Delete invalidated entries */
  	down_write(&listeners->sem);
  	list_for_each_entry_safe(s, tmp, &listeners->list, list) {
  		if (!s->valid) {
  			list_del(&s->list);
  			kfree(s);
  		}
  	}
  	up_write(&listeners->sem);

  }

  static void fill_stats(struct user_namespace *user_ns,
  		       struct pid_namespace *pid_ns,
  		       struct task_struct *tsk, struct taskstats *stats)

  {

  	memset(stats, 0, sizeof(*stats));

  	/*
  	 * Each accounting subsystem adds calls to its functions to
  	 * fill in relevant parts of struct taskstsats as follows
  	 *

  	 *	per-task-foo(stats, tsk);

  	 */

  	delayacct_add_tsk(stats, tsk);

  
  	/* fill in basic acct fields */

  	stats->version = TASKSTATS_VERSION;

  	stats->nvcsw = tsk->nvcsw;
  	stats->nivcsw = tsk->nivcsw;

  	bacct_add_tsk(user_ns, pid_ns, stats, tsk);

  	/* fill in extended acct fields */
  	xacct_add_tsk(stats, tsk);

  }

  static int fill_stats_for_pid(pid_t pid, struct taskstats *stats)
  {
  	struct task_struct *tsk;

  	rcu_read_lock();
  	tsk = find_task_by_vpid(pid);
  	if (tsk)
  		get_task_struct(tsk);
  	rcu_read_unlock();
  	if (!tsk)
  		return -ESRCH;

  	fill_stats(current_user_ns(), task_active_pid_ns(current), tsk, stats);

  	put_task_struct(tsk);
  	return 0;

  }

  static int fill_stats_for_tgid(pid_t tgid, struct taskstats *stats)

  {

  	struct task_struct *tsk, *first;

  	unsigned long flags;

  	int rc = -ESRCH;

  	u64 delta, utime, stime;
  	u64 start_time;

  	/*
  	 * Add additional stats from live tasks except zombie thread group
  	 * leaders who are already counted with the dead tasks
  	 */

  	rcu_read_lock();

  	first = find_task_by_vpid(tgid);

  	if (!first || !lock_task_sighand(first, &flags))
  		goto out;

  	if (first->signal->stats)
  		memcpy(stats, first->signal->stats, sizeof(*stats));

  	else
  		memset(stats, 0, sizeof(*stats));

  	tsk = first;

  	start_time = ktime_get_ns();

  	do {

  		if (tsk->exit_state)

  			continue;

  		/*

  		 * Accounting subsystem can call its functions here to

  		 * fill in relevant parts of struct taskstsats as follows
  		 *

  		 *	per-task-foo(stats, tsk);

  		 */

  		delayacct_add_tsk(stats, tsk);

  		/* calculate task elapsed time in nsec */
  		delta = start_time - tsk->start_time;
  		/* Convert to micro seconds */
  		do_div(delta, NSEC_PER_USEC);
  		stats->ac_etime += delta;
  
  		task_cputime(tsk, &utime, &stime);
  		stats->ac_utime += div_u64(utime, NSEC_PER_USEC);
  		stats->ac_stime += div_u64(stime, NSEC_PER_USEC);

  		stats->nvcsw += tsk->nvcsw;
  		stats->nivcsw += tsk->nivcsw;

  	} while_each_thread(first, tsk);

  	unlock_task_sighand(first, &flags);
  	rc = 0;
  out:
  	rcu_read_unlock();
  
  	stats->version = TASKSTATS_VERSION;

  	/*

  	 * Accounting subsystems can also add calls here to modify

  	 * fields of taskstats.

  	 */

  	return rc;

  }

  static void fill_tgid_exit(struct task_struct *tsk)
  {
  	unsigned long flags;

  	spin_lock_irqsave(&tsk->sighand->siglock, flags);

  	if (!tsk->signal->stats)
  		goto ret;
  
  	/*
  	 * Each accounting subsystem calls its functions here to
  	 * accumalate its per-task stats for tsk, into the per-tgid structure
  	 *
  	 *	per-task-foo(tsk->signal->stats, tsk);
  	 */
  	delayacct_add_tsk(tsk->signal->stats, tsk);
  ret:

  	spin_unlock_irqrestore(&tsk->sighand->siglock, flags);

  	return;

  }

  static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)

  {
  	struct listener_list *listeners;

  	struct listener *s, *tmp, *s2;

  	unsigned int cpu;

  	int ret = 0;

  	if (!cpumask_subset(mask, cpu_possible_mask))

  		return -EINVAL;

  	if (current_user_ns() != &init_user_ns)
  		return -EINVAL;
  
  	if (task_active_pid_ns(current) != &init_pid_ns)
  		return -EINVAL;

  	if (isadd == REGISTER) {

  		for_each_cpu(cpu, mask) {

  			s = kmalloc_node(sizeof(struct listener),
  					GFP_KERNEL, cpu_to_node(cpu));

  			if (!s) {
  				ret = -ENOMEM;

  				goto cleanup;

  			}

  			s->pid = pid;

  			s->valid = 1;

  
  			listeners = &per_cpu(listener_array, cpu);
  			down_write(&listeners->sem);

  			list_for_each_entry(s2, &listeners->list, list) {

  				if (s2->pid == pid && s2->valid)

  					goto exists;

  			}

  			list_add(&s->list, &listeners->list);

  			s = NULL;

  exists:

  			up_write(&listeners->sem);

  			kfree(s); /* nop if NULL */

  		}
  		return 0;
  	}
  
  	/* Deregister or cleanup */
  cleanup:

  	for_each_cpu(cpu, mask) {

  		listeners = &per_cpu(listener_array, cpu);
  		down_write(&listeners->sem);
  		list_for_each_entry_safe(s, tmp, &listeners->list, list) {
  			if (s->pid == pid) {
  				list_del(&s->list);
  				kfree(s);
  				break;
  			}
  		}
  		up_write(&listeners->sem);
  	}

  	return ret;

  }

  static int parse(struct nlattr *na, struct cpumask *mask)

  {
  	char *data;
  	int len;
  	int ret;
  
  	if (na == NULL)
  		return 1;
  	len = nla_len(na);
  	if (len > TASKSTATS_CPUMASK_MAXLEN)
  		return -E2BIG;
  	if (len < 1)
  		return -EINVAL;
  	data = kmalloc(len, GFP_KERNEL);
  	if (!data)
  		return -ENOMEM;
  	nla_strlcpy(data, na, len);

  	ret = cpulist_parse(data, mask);

  	kfree(data);
  	return ret;
  }

  static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)

  {

  	struct nlattr *na, *ret;

  	int aggr;

  	aggr = (type == TASKSTATS_TYPE_PID)
  			? TASKSTATS_TYPE_AGGR_PID
  			: TASKSTATS_TYPE_AGGR_TGID;

  
  	na = nla_nest_start(skb, aggr);

  	if (!na)
  		goto err;

  	if (nla_put(skb, type, sizeof(pid), &pid) < 0) {
  		nla_nest_cancel(skb, na);

  		goto err;

  	}

  	ret = nla_reserve_64bit(skb, TASKSTATS_TYPE_STATS,
  				sizeof(struct taskstats), TASKSTATS_TYPE_NULL);

  	if (!ret) {
  		nla_nest_cancel(skb, na);

  		goto err;

  	}

  	nla_nest_end(skb, na);

  	return nla_data(ret);
  err:
  	return NULL;

  }

  static int cgroupstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
  {
  	int rc = 0;
  	struct sk_buff *rep_skb;
  	struct cgroupstats *stats;
  	struct nlattr *na;
  	size_t size;
  	u32 fd;

  	struct fd f;

  
  	na = info->attrs[CGROUPSTATS_CMD_ATTR_FD];
  	if (!na)
  		return -EINVAL;
  
  	fd = nla_get_u32(info->attrs[CGROUPSTATS_CMD_ATTR_FD]);

  	f = fdget(fd);
  	if (!f.file)

  		return 0;

  	size = nla_total_size(sizeof(struct cgroupstats));

  	rc = prepare_reply(info, CGROUPSTATS_CMD_NEW, &rep_skb,
  				size);
  	if (rc < 0)
  		goto err;

  	na = nla_reserve(rep_skb, CGROUPSTATS_TYPE_CGROUP_STATS,
  				sizeof(struct cgroupstats));

  	if (na == NULL) {

  		nlmsg_free(rep_skb);

  		rc = -EMSGSIZE;
  		goto err;
  	}

  	stats = nla_data(na);
  	memset(stats, 0, sizeof(*stats));

  	rc = cgroupstats_build(stats, f.file->f_path.dentry);

  	if (rc < 0) {
  		nlmsg_free(rep_skb);
  		goto err;

  	}

  	rc = send_reply(rep_skb, info);

  err:

  	fdput(f);

  	return rc;
  }

  static int cmd_attr_register_cpumask(struct genl_info *info)

  {

  	cpumask_var_t mask;

  	int rc;

  
  	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
  		return -ENOMEM;

  	rc = parse(info->attrs[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK], mask);

  	if (rc < 0)

  		goto out;

  	rc = add_del_listener(info->snd_portid, mask, REGISTER);

  out:
  	free_cpumask_var(mask);
  	return rc;
  }
  
  static int cmd_attr_deregister_cpumask(struct genl_info *info)
  {
  	cpumask_var_t mask;
  	int rc;

  	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
  		return -ENOMEM;

  	rc = parse(info->attrs[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK], mask);

  	if (rc < 0)

  		goto out;

  	rc = add_del_listener(info->snd_portid, mask, DEREGISTER);

  out:

  	free_cpumask_var(mask);

  	return rc;
  }

  static size_t taskstats_packet_size(void)
  {
  	size_t size;
  
  	size = nla_total_size(sizeof(u32)) +

  		nla_total_size_64bit(sizeof(struct taskstats)) +
  		nla_total_size(0);

  	return size;
  }

  static int cmd_attr_pid(struct genl_info *info)
  {
  	struct taskstats *stats;
  	struct sk_buff *rep_skb;
  	size_t size;
  	u32 pid;
  	int rc;

  	size = taskstats_packet_size();

  	rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);

  	if (rc < 0)
  		return rc;

  	rc = -EINVAL;

  	pid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_PID]);
  	stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID, pid);
  	if (!stats)

  		goto err;

  	rc = fill_stats_for_pid(pid, stats);

  	if (rc < 0)
  		goto err;

  	return send_reply(rep_skb, info);

  err:
  	nlmsg_free(rep_skb);
  	return rc;
  }

  static int cmd_attr_tgid(struct genl_info *info)
  {
  	struct taskstats *stats;
  	struct sk_buff *rep_skb;
  	size_t size;
  	u32 tgid;
  	int rc;

  	size = taskstats_packet_size();

  
  	rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
  	if (rc < 0)
  		return rc;
  
  	rc = -EINVAL;
  	tgid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_TGID]);
  	stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tgid);
  	if (!stats)
  		goto err;

  	rc = fill_stats_for_tgid(tgid, stats);

  	if (rc < 0)
  		goto err;
  	return send_reply(rep_skb, info);
  err:
  	nlmsg_free(rep_skb);
  	return rc;
  }
  
  static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
  {
  	if (info->attrs[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK])
  		return cmd_attr_register_cpumask(info);
  	else if (info->attrs[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK])
  		return cmd_attr_deregister_cpumask(info);
  	else if (info->attrs[TASKSTATS_CMD_ATTR_PID])
  		return cmd_attr_pid(info);
  	else if (info->attrs[TASKSTATS_CMD_ATTR_TGID])
  		return cmd_attr_tgid(info);
  	else
  		return -EINVAL;
  }

  static struct taskstats *taskstats_tgid_alloc(struct task_struct *tsk)
  {
  	struct signal_struct *sig = tsk->signal;
  	struct taskstats *stats;
  
  	if (sig->stats || thread_group_empty(tsk))
  		goto ret;
  
  	/* No problem if kmem_cache_zalloc() fails */
  	stats = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);
  
  	spin_lock_irq(&tsk->sighand->siglock);
  	if (!sig->stats) {
  		sig->stats = stats;
  		stats = NULL;
  	}
  	spin_unlock_irq(&tsk->sighand->siglock);
  
  	if (stats)
  		kmem_cache_free(taskstats_cache, stats);
  ret:
  	return sig->stats;
  }

  /* Send pid data out on exit */

  void taskstats_exit(struct task_struct *tsk, int group_dead)

  {
  	int rc;

  	struct listener_list *listeners;

  	struct taskstats *stats;

  	struct sk_buff *rep_skb;

  	size_t size;
  	int is_thread_group;

  	if (!family_registered)

  		return;

  	/*
  	 * Size includes space for nested attributes
  	 */

  	size = taskstats_packet_size();

  	is_thread_group = !!taskstats_tgid_alloc(tsk);

  	if (is_thread_group) {
  		/* PID + STATS + TGID + STATS */
  		size = 2 * size;
  		/* fill the tsk->signal->stats structure */
  		fill_tgid_exit(tsk);
  	}

  	listeners = raw_cpu_ptr(&listener_array);

  	if (list_empty(&listeners->list))
  		return;

  	rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, size);

  	if (rc < 0)

  		return;

  	stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID,
  			 task_pid_nr_ns(tsk, &init_pid_ns));

  	if (!stats)

  		goto err;

  	fill_stats(&init_user_ns, &init_pid_ns, tsk, stats);

  	/*

  	 * Doesn't matter if tsk is the leader or the last group member leaving

  	 */

  	if (!is_thread_group || !group_dead)

  		goto send;

  	stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID,
  			 task_tgid_nr_ns(tsk, &init_pid_ns));

  	if (!stats)

  		goto err;

  
  	memcpy(stats, tsk->signal->stats, sizeof(*stats));

  send:

  	send_cpu_listeners(rep_skb, listeners);

  	return;

  err:

  	nlmsg_free(rep_skb);

  }

  static const struct genl_ops taskstats_ops[] = {

  	{
  		.cmd		= TASKSTATS_CMD_GET,
  		.doit		= taskstats_user_cmd,
  		.policy		= taskstats_cmd_get_policy,
  		.flags		= GENL_ADMIN_PERM,
  	},
  	{
  		.cmd		= CGROUPSTATS_CMD_GET,
  		.doit		= cgroupstats_user_cmd,
  		.policy		= cgroupstats_cmd_get_policy,
  	},

  };

  static struct genl_family family __ro_after_init = {

  	.name		= TASKSTATS_GENL_NAME,
  	.version	= TASKSTATS_GENL_VERSION,
  	.maxattr	= TASKSTATS_CMD_ATTR_MAX,
  	.module		= THIS_MODULE,
  	.ops		= taskstats_ops,
  	.n_ops		= ARRAY_SIZE(taskstats_ops),
  };

  /* Needed early in initialization */
  void __init taskstats_init_early(void)
  {

  	unsigned int i;

  	taskstats_cache = KMEM_CACHE(taskstats, SLAB_PANIC);

  	for_each_possible_cpu(i) {
  		INIT_LIST_HEAD(&(per_cpu(listener_array, i).list));
  		init_rwsem(&(per_cpu(listener_array, i).sem));
  	}

  }
  
  static int __init taskstats_init(void)
  {
  	int rc;

  	rc = genl_register_family(&family);

  	if (rc)
  		return rc;

  	family_registered = 1;

  	pr_info("registered taskstats version %d
  ", TASKSTATS_GENL_VERSION);

  	return 0;

  }
  
  /*
   * late initcall ensures initialization of statistics collection
   * mechanisms precedes initialization of the taskstats interface
   */
  late_initcall(taskstats_init);