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#include <linux/acct.h>
  16#include <linux/slab.h>
  17
  18#define BITS_PER_PAGE           (PAGE_SIZE*8)
  19
  20struct pid_cache {
  21        int nr_ids;
  22        char name[16];
  23        struct kmem_cache *cachep;
  24        struct list_head list;
  25};
  26
  27static LIST_HEAD(pid_caches_lh);
  28static DEFINE_MUTEX(pid_caches_mutex);
  29static struct kmem_cache *pid_ns_cachep;
  30
  31/*
  32 * creates the kmem cache to allocate pids from.
  33 * @nr_ids: the number of numerical ids this pid will have to carry
  34 */
  35
  36static struct kmem_cache *create_pid_cachep(int nr_ids)
  37{
  38        struct pid_cache *pcache;
  39        struct kmem_cache *cachep;
  40
  41        mutex_lock(&pid_caches_mutex);
  42        list_for_each_entry(pcache, &pid_caches_lh, list)
  43                if (pcache->nr_ids == nr_ids)
  44                        goto out;
  45
  46        pcache = kmalloc(sizeof(struct pid_cache), GFP_KERNEL);
  47        if (pcache == NULL)
  48                goto err_alloc;
  49
  50        snprintf(pcache->name, sizeof(pcache->name), "pid_%d", nr_ids);
  51        cachep = kmem_cache_create(pcache->name,
  52                        sizeof(struct pid) + (nr_ids - 1) * sizeof(struct upid),
  53                        0, SLAB_HWCACHE_ALIGN, NULL);
  54        if (cachep == NULL)
  55                goto err_cachep;
  56
  57        pcache->nr_ids = nr_ids;
  58        pcache->cachep = cachep;
  59        list_add(&pcache->list, &pid_caches_lh);
  60out:
  61        mutex_unlock(&pid_caches_mutex);
  62        return pcache->cachep;
  63
  64err_cachep:
  65        kfree(pcache);
  66err_alloc:
  67        mutex_unlock(&pid_caches_mutex);
  68        return NULL;
  69}
  70
  71static struct pid_namespace *create_pid_namespace(struct pid_namespace *parent_pid_ns)
  72{
  73        struct pid_namespace *ns;
  74        unsigned int level = parent_pid_ns->level + 1;
  75        int i;
  76
  77        ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL);
  78        if (ns == NULL)
  79                goto out;
  80
  81        ns->pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
  82        if (!ns->pidmap[0].page)
  83                goto out_free;
  84
  85        ns->pid_cachep = create_pid_cachep(level + 1);
  86        if (ns->pid_cachep == NULL)
  87                goto out_free_map;
  88
  89        kref_init(&ns->kref);
  90        ns->level = level;
  91        ns->parent = get_pid_ns(parent_pid_ns);
  92
  93        set_bit(0, ns->pidmap[0].page);
  94        atomic_set(&ns->pidmap[0].nr_free, BITS_PER_PAGE - 1);
  95
  96        for (i = 1; i < PIDMAP_ENTRIES; i++)
  97                atomic_set(&ns->pidmap[i].nr_free, BITS_PER_PAGE);
  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        if (!(flags & CLONE_NEWPID))
 121                return get_pid_ns(old_ns);
 122        if (flags & (CLONE_THREAD|CLONE_PARENT))
 123                return ERR_PTR(-EINVAL);
 124        return create_pid_namespace(old_ns);
 125}
 126
 127void free_pid_ns(struct kref *kref)
 128{
 129        struct pid_namespace *ns, *parent;
 130
 131        ns = container_of(kref, struct pid_namespace, kref);
 132
 133        parent = ns->parent;
 134        destroy_pid_namespace(ns);
 135
 136        if (parent != NULL)
 137                put_pid_ns(parent);
 138}
 139
 140void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 141{
 142        int nr;
 143        int rc;
 144        struct task_struct *task;
 145
 146        /*
 147         * The last thread in the cgroup-init thread group is terminating.
 148         * Find remaining pid_ts in the namespace, signal and wait for them
 149         * to exit.
 150         *
 151         * Note:  This signals each threads in the namespace - even those that
 152         *        belong to the same thread group, To avoid this, we would have
 153         *        to walk the entire tasklist looking a processes in this
 154         *        namespace, but that could be unnecessarily expensive if the
 155         *        pid namespace has just a few processes. Or we need to
 156         *        maintain a tasklist for each pid namespace.
 157         *
 158         */
 159        read_lock(&tasklist_lock);
 160        nr = next_pidmap(pid_ns, 1);
 161        while (nr > 0) {
 162                rcu_read_lock();
 163
 164                /*
 165                 * Any nested-container's init processes won't ignore the
 166                 * SEND_SIG_NOINFO signal, see send_signal()->si_fromuser().
 167                 */
 168                task = pid_task(find_vpid(nr), PIDTYPE_PID);
 169                if (task)
 170                        send_sig_info(SIGKILL, SEND_SIG_NOINFO, task);
 171
 172                rcu_read_unlock();
 173
 174                nr = next_pidmap(pid_ns, nr);
 175        }
 176        read_unlock(&tasklist_lock);
 177
 178        do {
 179                clear_thread_flag(TIF_SIGPENDING);
 180                rc = sys_wait4(-1, NULL, __WALL, NULL);
 181        } while (rc != -ECHILD);
 182
 183        acct_exit_ns(pid_ns);
 184        return;
 185}
 186
 187static __init int pid_namespaces_init(void)
 188{
 189        pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
 190        return 0;
 191}
 192
 193__initcall(pid_namespaces_init);
 194