// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * taskstats.c - Export per-task statistics to userland
 *
 * Copyright (C) Shailabh Nagar, IBM Corp. 2006
 *           (C) Balbir Singh,   IBM Corp. 2006
 */

#include <linux/kernel.h>
#include <linux/taskstats_kern.h>
#include <linux/tsacct_kern.h>
#include <linux/acct.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_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 },};

static const struct nla_policy cgroupstats_cmd_get_policy[] = {
	[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
};

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 delcount = 0;

	genlmsg_end(skb, reply);

	down_read(&listeners->sem);
	list_for_each_entry(s, &listeners->list, list) {
		int rc;

		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 exe_add_tsk(struct taskstats *stats, struct task_struct *tsk)
{
	/* No idea if I'm allowed to access that here, now. */
	struct file *exe_file = get_task_exe_file(tsk);

	if (exe_file) {
		/* Following cp_new_stat64() in stat.c . */
		stats->ac_exe_dev =
			huge_encode_dev(exe_file->f_inode->i_sb->s_dev);
		stats->ac_exe_inode = exe_file->f_inode->i_ino;
		fput(exe_file);
	} else {
		stats->ac_exe_dev = 0;
		stats->ac_exe_inode = 0;
	}
}

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);

	/* add executable info */
	exe_add_tsk(stats, tsk);
}

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

	tsk = find_get_task_by_vpid(pid);
	if (!tsk)
		return -ESRCH;
	fill_stats(current_user_ns(), task_active_pid_ns(current), tsk, stats);
	put_task_struct(tsk);
	return 0;
}

static void tgid_stats_add_task(struct taskstats *stats,
				struct task_struct *tsk, u64 now_ns)
{
	u64 delta, utime, stime;

	/*
	 * Each accounting subsystem calls its functions here to
	 * accumulate its per-task stats for tsk, into the per-tgid structure
	 *
	 *	per-task-foo(stats, tsk);
	 */
	delayacct_add_tsk(stats, tsk);

	/* calculate task elapsed time in nsec */
	delta = now_ns - 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;
}

static int fill_stats_for_tgid(pid_t tgid, struct taskstats *stats)
{
	struct task_struct *tsk, *first;
	unsigned long flags;
	int rc = -ESRCH;
	u64 now_ns;

	/*
	 * 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));

	now_ns = ktime_get_ns();
	for_each_thread(first, tsk) {
		if (tsk->exit_state)
			continue;

		tgid_stats_add_task(stats, tsk, now_ns);
	}

	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;
	u64 now_ns;

	spin_lock_irqsave(&tsk->sighand->siglock, flags);
	if (!tsk->signal->stats)
		goto ret;

	now_ns = ktime_get_ns();
	tgid_stats_add_task(tsk->signal->stats, tsk, now_ns);
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;

	len = nla_len(na);
	if (len > TASKSTATS_CPUMASK_MAXLEN)
		return -E2BIG;
	if (len < 1)
		return -EINVAL;
	data = nla_strdup(na, GFP_KERNEL);
	if (!data)
		return -ENOMEM;
	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_noflag(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;

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

	fd = nla_get_u32(info->attrs[CGROUPSTATS_CMD_ATTR_FD]);
	CLASS(fd, f)(fd);
	if (fd_empty(f))
		return -EBADF;

	size = nla_total_size(sizeof(struct cgroupstats));

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

	na = nla_reserve(rep_skb, CGROUPSTATS_TYPE_CGROUP_STATS,
				sizeof(struct cgroupstats));
	if (na == NULL) {
		nlmsg_free(rep_skb);
		return -EMSGSIZE;
	}

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

	rc = cgroupstats_build(stats, fd_file(f)->f_path.dentry);
	if (rc < 0) {
		nlmsg_free(rep_skb);
		return rc;
	}

	return send_reply(rep_skb, info);
}

static int cmd_attr_cpumask(struct genl_info *info, int attr,
			    enum actions action)
{
	cpumask_var_t mask __free(free_cpumask_var) = CPUMASK_VAR_NULL;
	int rc;

	if (!alloc_cpumask_var(&mask, GFP_KERNEL))
		return -ENOMEM;
	rc = parse(info->attrs[attr], mask);
	if (rc < 0)
		return rc;
	return add_del_listener(info->snd_portid, mask, action);
}

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_tgid(struct genl_info *info, int attr,
			     int (*fill)(pid_t, struct taskstats *))
{
	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[attr]);
	stats = mk_reply(rep_skb,
			 attr == TASKSTATS_CMD_ATTR_PID
				? TASKSTATS_TYPE_PID : TASKSTATS_TYPE_TGID,
			 pid);
	if (!stats)
		goto err;

	rc = fill(pid, 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_cpumask(info,
					TASKSTATS_CMD_ATTR_REGISTER_CPUMASK,
					REGISTER);
	else if (info->attrs[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK])
		return cmd_attr_cpumask(info,
					TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK,
					DEREGISTER);
	else if (info->attrs[TASKSTATS_CMD_ATTR_PID])
		return cmd_attr_pid_tgid(info, TASKSTATS_CMD_ATTR_PID,
					 fill_stats_for_pid);
	else if (info->attrs[TASKSTATS_CMD_ATTR_TGID])
		return cmd_attr_pid_tgid(info, TASKSTATS_CMD_ATTR_TGID,
					 fill_stats_for_tgid);
	else
		return -EINVAL;
}

static struct taskstats *taskstats_tgid_alloc(struct task_struct *tsk)
{
	struct signal_struct *sig = tsk->signal;
	struct taskstats *stats_new, *stats;

	/* Pairs with smp_store_release() below. */
	stats = smp_load_acquire(&sig->stats);
	if (stats || thread_group_empty(tsk))
		return stats;

	/* No problem if kmem_cache_zalloc() fails */
	stats_new = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);

	spin_lock_irq(&tsk->sighand->siglock);
	stats = sig->stats;
	if (!stats) {
		/*
		 * Pairs with smp_store_release() above and order the
		 * kmem_cache_zalloc().
		 */
		smp_store_release(&sig->stats, stats_new);
		stats = stats_new;
		stats_new = NULL;
	}
	spin_unlock_irq(&tsk->sighand->siglock);

	if (stats_new)
		kmem_cache_free(taskstats_cache, stats_new);

	return 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);
	if (group_dead)
		stats->ac_flag |= AGROUP;

	/*
	 * 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));
	stats->version = TASKSTATS_VERSION;

send:
	send_cpu_listeners(rep_skb, listeners);
	return;
err:
	nlmsg_free(rep_skb);
}

static const struct genl_ops taskstats_ops[] = {
	{
		.cmd		= TASKSTATS_CMD_GET,
		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
		.doit		= taskstats_user_cmd,
		.policy		= taskstats_cmd_get_policy,
		.maxattr	= ARRAY_SIZE(taskstats_cmd_get_policy) - 1,
		.flags		= GENL_ADMIN_PERM,
	},
	{
		.cmd		= CGROUPSTATS_CMD_GET,
		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
		.doit		= cgroupstats_user_cmd,
		.policy		= cgroupstats_cmd_get_policy,
		.maxattr	= ARRAY_SIZE(cgroupstats_cmd_get_policy) - 1,
	},
};

static struct genl_family family __ro_after_init = {
	.name		= TASKSTATS_GENL_NAME,
	.version	= TASKSTATS_GENL_VERSION,
	.module		= THIS_MODULE,
	.ops		= taskstats_ops,
	.n_ops		= ARRAY_SIZE(taskstats_ops),
	.resv_start_op	= CGROUPSTATS_CMD_GET + 1,
	.netnsok	= true,
};

/* 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\n", TASKSTATS_GENL_VERSION);
	return 0;
}

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