/*
 * Pid namespaces
 *
 * Authors:
 *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
 *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
 *     Many thanks to Oleg Nesterov for comments and help
 *
 */

#include <linux/pid.h>
#include <linux/pid_namespace.h>
#include <linux/syscalls.h>
#include <linux/err.h>
#include <linux/acct.h>

#define BITS_PER_PAGE           (PAGE_SIZE*8)

struct pid_cache {
        int nr_ids;
        char name[16];
        struct kmem_cache *cachep;
        struct list_head list;
};

static LIST_HEAD(pid_caches_lh);
static DEFINE_MUTEX(pid_caches_mutex);
static struct kmem_cache *pid_ns_cachep;

/*
 * creates the kmem cache to allocate pids from.
 * @nr_ids: the number of numerical ids this pid will have to carry
 */

static struct kmem_cache *create_pid_cachep(int nr_ids)
{
        struct pid_cache *pcache;
        struct kmem_cache *cachep;

        mutex_lock(&pid_caches_mutex);
        list_for_each_entry(pcache, &pid_caches_lh, list)
                if (pcache->nr_ids == nr_ids)
                        goto out;

        pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
        if (pcache == NULL)
                goto err_alloc;

        snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
        cachep = kmem_cache_create(pcache->name,
                        sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
                        0, SLAB_HWCACHE_ALIGN, NULL);
        if (cachep == NULL)
                goto err_cachep;

        pcache->nr_ids = nr_ids;
        pcache->cachep = cachep;
        list_add(&pcache->list, &pid_caches_lh);
out:
        mutex_unlock(&pid_caches_mutex);
        return pcache->cachep;

err_cachep:
        kfree(pcache);
err_alloc:
        mutex_unlock(&pid_caches_mutex);
        return NULL;
}

static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
{
        struct pid_namespace *ns;
        unsigned int level = parent_pid_ns->level + 1;
        int i;

        ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
        if (ns == NULL)
                goto out;

        ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
        if (!ns->pidmap[0].page)
                goto out_free;

        ns->pid_cachep = create_pid_cachep(level + 1);
        if (ns->pid_cachep == NULL)
                goto out_free_map;

        kref_init(&ns->kref);
        ns->level = level;
        ns->parent = get_pid_ns(parent_pid_ns);

        set_bit(0, ns->pidmap[0].page);
        atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);

        for (i = 1; i < PIDMAP_ENTRIES; i++)
                atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);

        return ns;

out_free_map:
        kfree(ns->pidmap[0].page);
out_free:
        kmem_cache_free(pid_ns_cachep, ns);
out:
        return ERR_PTR(-ENOMEM);
}

static void destroy_pid_namespace(struct pid_namespace *ns)
{
        int i;

        for (i = 0; i < PIDMAP_ENTRIES; i++)
                kfree(ns->pidmap[i].page);
        kmem_cache_free(pid_ns_cachep, ns);
}

struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
{
        if (!(flags & CLONE_NEWPID))
                return get_pid_ns(old_ns);
        if (flags & (CLONE_THREAD|CLONE_PARENT))
                return ERR_PTR(-EINVAL);
        return create_pid_namespace(old_ns);
}

void free_pid_ns(struct kref *kref)
{
        struct pid_namespace *ns, *parent;

        ns = container_of(kref, struct pid_namespace, kref);

        parent = ns->parent;
        destroy_pid_namespace(ns);

        if (parent != NULL)
                put_pid_ns(parent);
}

void zap_pid_ns_processes(struct pid_namespace *pid_ns)
{
        int nr;
        int rc;
        struct task_struct *task;

        /*
         * The last thread in the cgroup-init thread group is terminating.
         * Find remaining pid_ts in the namespace, signal and wait for them
         * to exit.
         *
         * Note:  This signals each threads in the namespace - even those that
         *        belong to the same thread group, To avoid this, we would have
         *        to walk the entire tasklist looking a processes in this
         *        namespace, but that could be unnecessarily expensive if the
         *        pid namespace has just a few processes. Or we need to
         *        maintain a tasklist for each pid namespace.
         *
         */
        read_lock(&tasklist_lock);
        nr = next_pidmap(pid_ns, 1);
        while (nr > 0) {
                rcu_read_lock();

                /*
                 * Use force_sig() since it clears SIGNAL_UNKILLABLE ensuring
                 * any nested-container's init processes don't ignore the
                 * signal
                 */
                task = pid_task(find_vpid(nr), PIDTYPE_PID);
                if (task)
                        force_sig(SIGKILL, task);

                rcu_read_unlock();

                nr = next_pidmap(pid_ns, nr);
        }
        read_unlock(&tasklist_lock);

        do {
                clear_thread_flag(TIF_SIGPENDING);
                rc = sys_wait4(-1, NULL, __WALL, NULL);
        } while (rc != -ECHILD);

        acct_exit_ns(pid_ns);
        return;
}

static __init int pid_namespaces_init(void)
{
        pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
        return 0;
}

__initcall(pid_namespaces_init);