LXR linux/kernel/pid

   1/*
   2 * Pid namespaces
   3 *
   4 * Authors:
   5 *    (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
   6 *    (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
   7 *     Many thanks to Oleg Nesterov for comments and help
   8 *
   9 */
  10
  11#include <linux/pid.h>
  12#include <linux/pid_namespace.h>
  13#include <linux/syscalls.h>
  14#include <linux/err.h>
  15
  16#define BITS_PER_PAGE           (PAGE_SIZE*8)
  17
  18struct pid_cache {
  19        int nr_ids;
  20        char name[16];
  21        struct kmem_cache *cachep;
  22        struct list_head list;
  23};
  24
  25static LIST_HEAD(pid_caches_lh);
  26static DEFINE_MUTEX(pid_caches_mutex);
  27static struct kmem_cache *pid_ns_cachep;
  28
  29/*
  30 * creates the kmem cache to allocate pids from.
  31 * @nr_ids: the number of numerical ids this pid will have to carry
  32 */
  33
  34static struct kmem_cache *create_pid_cachep(int nr_ids)
  35{
  36        struct pid_cache *pcache;
  37        struct kmem_cache *cachep;
  38
  39        mutex_lock(&pid_caches_mutex);
  40        list_for_each_entry(pcache, &pid_caches_lh, list)
  41                if (pcache->nr_ids == nr_ids)
  42                        goto out;
  43
  44        pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
  45        if (pcache == NULL)
  46                goto err_alloc;
  47
  48        snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
  49        cachep = kmem_cache_create(pcache->name,
  50                        sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
  51                        0, SLAB_HWCACHE_ALIGN, NULL);
  52        if (cachep == NULL)
  53                goto err_cachep;
  54
  55        pcache->nr_ids = nr_ids;
  56        pcache->cachep = cachep;
  57        list_add(&pcache->list, &pid_caches_lh);
  58out:
  59        mutex_unlock(&pid_caches_mutex);
  60        return pcache->cachep;
  61
  62err_cachep:
  63        kfree(pcache);
  64err_alloc:
  65        mutex_unlock(&pid_caches_mutex);
  66        return NULL;
  67}
  68
  69static struct pid_namespace *create_pid_namespace(unsigned int level)
  70{
  71        struct pid_namespace *ns;
  72        int i;
  73
  74        ns = kmem_cache_alloc(pid_ns_cachep, GFP_KERNEL);
  75        if (ns == NULL)
  76                goto out;
  77
  78        ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
  79        if (!ns->pidmap[0].page)
  80                goto out_free;
  81
  82        ns->pid_cachep = create_pid_cachep(level + 1);
  83        if (ns->pid_cachep == NULL)
  84                goto out_free_map;
  85
  86        kref_init(&ns->kref);
  87        ns->last_pid = 0;
  88        ns->child_reaper = NULL;
  89        ns->level = level;
  90
  91        set_bit(0, ns->pidmap[0].page);
  92        atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
  93
  94        for (i = 1; i < PIDMAP_ENTRIES; i++) {
  95                ns->pidmap[i].page = NULL;
  96                atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
  97        }
  98
  99        return ns;
 100
 101out_free_map:
 102        kfree(ns->pidmap[0].page);
 103out_free:
 104        kmem_cache_free(pid_ns_cachep, ns);
 105out:
 106        return ERR_PTR(-ENOMEM);
 107}
 108
 109static void destroy_pid_namespace(struct pid_namespace *ns)
 110{
 111        int i;
 112
 113        for (i = 0; i < PIDMAP_ENTRIES; i++)
 114                kfree(ns->pidmap[i].page);
 115        kmem_cache_free(pid_ns_cachep, ns);
 116}
 117
 118struct pid_namespace *copy_pid_ns(unsigned long flags, struct pid_namespace *old_ns)
 119{
 120        struct pid_namespace *new_ns;
 121
 122        BUG_ON(!old_ns);
 123        new_ns = get_pid_ns(old_ns);
 124        if (!(flags & CLONE_NEWPID))
 125                goto out;
 126
 127        new_ns = ERR_PTR(-EINVAL);
 128        if (flags & CLONE_THREAD)
 129                goto out_put;
 130
 131        new_ns = create_pid_namespace(old_ns->level + 1);
 132        if (!IS_ERR(new_ns))
 133                new_ns->parent = get_pid_ns(old_ns);
 134
 135out_put:
 136        put_pid_ns(old_ns);
 137out:
 138        return new_ns;
 139}
 140
 141void free_pid_ns(struct kref *kref)
 142{
 143        struct pid_namespace *ns, *parent;
 144
 145        ns = container_of(kref, struct pid_namespace, kref);
 146
 147        parent = ns->parent;
 148        destroy_pid_namespace(ns);
 149
 150        if (parent != NULL)
 151                put_pid_ns(parent);
 152}
 153
 154void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 155{
 156        int nr;
 157        int rc;
 158
 159        /*
 160         * The last thread in the cgroup-init thread group is terminating.
 161         * Find remaining pid_ts in the namespace, signal and wait for them
 162         * to exit.
 163         *
 164         * Note:  This signals each threads in the namespace - even those that
 165         *        belong to the same thread group, To avoid this, we would have
 166         *        to walk the entire tasklist looking a processes in this
 167         *        namespace, but that could be unnecessarily expensive if the
 168         *        pid namespace has just a few processes. Or we need to
 169         *        maintain a tasklist for each pid namespace.
 170         *
 171         */
 172        read_lock(&tasklist_lock);
 173        nr = next_pidmap(pid_ns, 1);
 174        while (nr > 0) {
 175                kill_proc_info(SIGKILL, SEND_SIG_PRIV, nr);
 176                nr = next_pidmap(pid_ns, nr);
 177        }
 178        read_unlock(&tasklist_lock);
 179
 180        do {
 181                clear_thread_flag(TIF_SIGPENDING);
 182                rc = sys_wait4(-1, NULL, __WALL, NULL);
 183        } while (rc != -ECHILD);
 184
 185
 186        /* Child reaper for the pid namespace is going away */
 187        pid_ns->child_reaper = NULL;
 188        return;
 189}
 190
 191static __init int pid_namespaces_init(void)
 192{
 193        pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 194        return 0;
 195}
 196
 197__initcall(pid_namespaces_init);
 198