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

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