taskstats.c

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/*
 * 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>

/*
 * 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 = {
    .id     = GENL_ID_GENERATE,
    .name       = TASKSTATS_GENL_NAME,
    .version    = TASKSTATS_GENL_VERSION,
    .maxattr    = TASKSTATS_CMD_ATTR_MAX,
};

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 },};

static const struct nla_policy cgroupstats_cmd_get_policy[CGROUPSTATS_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);
    int rc;

    rc = genlmsg_end(skb, reply);
    if (rc < 0) {
        nlmsg_free(skb);
        return rc;
    }

    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;

    rc = genlmsg_end(skb, reply);
    if (rc < 0) {
        nlmsg_free(skb);
        return;
    }

    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;

    /*
     * 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;
    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);

        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;

    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)
                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 0;
}

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;
}

#if defined(CONFIG_64BIT) && !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
#define TASKSTATS_NEEDS_PADDING 1
#endif

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;

    /*
     * The taskstats structure is internally aligned on 8 byte
     * boundaries but the layout of the aggregrate reply, with
     * two NLA headers and the pid (each 4 bytes), actually
     * force the entire structure to be unaligned. This causes
     * the kernel to issue unaligned access warnings on some
     * architectures like ia64. Unfortunately, some software out there
     * doesn't properly unroll the NLA packet and assumes that the start
     * of the taskstats structure will always be 20 bytes from the start
     * of the netlink payload. Aligning the start of the taskstats
     * structure breaks this software, which we don't want. So, for now
     * the alignment only happens on architectures that require it
     * and those users will have to update to fixed versions of those
     * packages. Space is reserved in the packet only when needed.
     * This ifdef should be removed in several years e.g. 2012 once
     * we can be confident that fixed versions are installed on most
     * systems. We add the padding before the aggregate since the
     * aggregate is already a defined type.
     */
#ifdef TASKSTATS_NEEDS_PADDING
    if (nla_put(skb, TASKSTATS_TYPE_NULL, 0, NULL) < 0)
        goto err;
#endif
    na = nla_nest_start(skb, aggr);
    if (!na)
        goto err;

    if (nla_put(skb, type, sizeof(pid), &pid) < 0)
        goto err;
    ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
    if (!ret)
        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_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(sizeof(struct taskstats)) + nla_total_size(0);
#ifdef TASKSTATS_NEEDS_PADDING
    size += nla_total_size(0); /* Padding for alignment */
#endif
    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 = __this_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 struct genl_ops taskstats_ops = {
    .cmd        = TASKSTATS_CMD_GET,
    .doit       = taskstats_user_cmd,
    .policy     = taskstats_cmd_get_policy,
    .flags      = GENL_ADMIN_PERM,
};

static struct genl_ops cgroupstats_ops = {
    .cmd        = CGROUPSTATS_CMD_GET,
    .doit       = cgroupstats_user_cmd,
    .policy     = cgroupstats_cmd_get_policy,
};

/* 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;

    rc = genl_register_ops(&family, &taskstats_ops);
    if (rc < 0)
        goto err;

    rc = genl_register_ops(&family, &cgroupstats_ops);
    if (rc < 0)
        goto err_cgroup_ops;

    family_registered = 1;
    pr_info("registered taskstats version %d\n", TASKSTATS_GENL_VERSION);
    return 0;
err_cgroup_ops:
    genl_unregister_ops(&family, &taskstats_ops);
err:
    genl_unregister_family(&family);
    return rc;
}

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