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1/*
2 * Generic pidhash and scalable, time-bounded PID allocator
3 *
4 * (C) 2002-2003 Nadia Yvette Chambers, IBM
5 * (C) 2004 Nadia Yvette Chambers, Oracle
6 * (C) 2002-2004 Ingo Molnar, Red Hat
7 *
8 * pid-structures are backing objects for tasks sharing a given ID to chain
9 * against. There is very little to them aside from hashing them and
10 * parking tasks using given ID's on a list.
11 *
12 * The hash is always changed with the tasklist_lock write-acquired,
13 * and the hash is only accessed with the tasklist_lock at least
14 * read-acquired, so there's no additional SMP locking needed here.
15 *
16 * We have a list of bitmap pages, which bitmaps represent the PID space.
17 * Allocating and freeing PIDs is completely lockless. The worst-case
18 * allocation scenario when all but one out of 1 million PIDs possible are
19 * allocated already: the scanning of 32 list entries and at most PAGE_SIZE
20 * bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
21 *
22 * Pid namespaces:
23 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
24 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
25 * Many thanks to Oleg Nesterov for comments and help
26 *
27 */
28
29#include <linux/mm.h>
30#include <linux/export.h>
31#include <linux/slab.h>
32#include <linux/init.h>
33#include <linux/rculist.h>
34#include <linux/bootmem.h>
35#include <linux/hash.h>
36#include <linux/pid_namespace.h>
37#include <linux/init_task.h>
38#include <linux/syscalls.h>
39#include <linux/proc_ns.h>
40#include <linux/proc_fs.h>
41
42#define pid_hashfn(nr, ns) \
43 hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
44static struct hlist_head *pid_hash;
45static unsigned int pidhash_shift = 4;
46struct pid init_struct_pid = INIT_STRUCT_PID;
47
48int pid_max = PID_MAX_DEFAULT;
49
50#define RESERVED_PIDS 300
51
52int pid_max_min = RESERVED_PIDS + 1;
53int pid_max_max = PID_MAX_LIMIT;
54
55static inline int mk_pid(struct pid_namespace *pid_ns,
56 struct pidmap *map, int off)
57{
58 return (map - pid_ns->pidmap)*BITS_PER_PAGE + off;
59}
60
61#define find_next_offset(map, off) \
62 find_next_zero_bit((map)->page, BITS_PER_PAGE, off)
63
64/*
65 * PID-map pages start out as NULL, they get allocated upon
66 * first use and are never deallocated. This way a low pid_max
67 * value does not cause lots of bitmaps to be allocated, but
68 * the scheme scales to up to 4 million PIDs, runtime.
69 */
70struct pid_namespace init_pid_ns = {
71 .kref = {
72 .refcount = ATOMIC_INIT(2),
73 },
74 .pidmap = {
75 [ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL }
76 },
77 .last_pid = 0,
78 .nr_hashed = PIDNS_HASH_ADDING,
79 .level = 0,
80 .child_reaper = &init_task,
81 .user_ns = &init_user_ns,
82 .proc_inum = PROC_PID_INIT_INO,
83};
84EXPORT_SYMBOL_GPL(init_pid_ns);
85
86/*
87 * Note: disable interrupts while the pidmap_lock is held as an
88 * interrupt might come in and do read_lock(&tasklist_lock).
89 *
90 * If we don't disable interrupts there is a nasty deadlock between
91 * detach_pid()->free_pid() and another cpu that does
92 * spin_lock(&pidmap_lock) followed by an interrupt routine that does
93 * read_lock(&tasklist_lock);
94 *
95 * After we clean up the tasklist_lock and know there are no
96 * irq handlers that take it we can leave the interrupts enabled.
97 * For now it is easier to be safe than to prove it can't happen.
98 */
99
100static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
101
102static void free_pidmap(struct upid *upid)
103{
104 int nr = upid->nr;
105 struct pidmap *map = upid->ns->pidmap + nr / BITS_PER_PAGE;
106 int offset = nr & BITS_PER_PAGE_MASK;
107
108 clear_bit(offset, map->page);
109 atomic_inc(&map->nr_free);
110}
111
112/*
113 * If we started walking pids at 'base', is 'a' seen before 'b'?
114 */
115static int pid_before(int base, int a, int b)
116{
117 /*
118 * This is the same as saying
119 *
120 * (a - base + MAXUINT) % MAXUINT < (b - base + MAXUINT) % MAXUINT
121 * and that mapping orders 'a' and 'b' with respect to 'base'.
122 */
123 return (unsigned)(a - base) < (unsigned)(b - base);
124}
125
126/*
127 * We might be racing with someone else trying to set pid_ns->last_pid
128 * at the pid allocation time (there's also a sysctl for this, but racing
129 * with this one is OK, see comment in kernel/pid_namespace.c about it).
130 * We want the winner to have the "later" value, because if the
131 * "earlier" value prevails, then a pid may get reused immediately.
132 *
133 * Since pids rollover, it is not sufficient to just pick the bigger
134 * value. We have to consider where we started counting from.
135 *
136 * 'base' is the value of pid_ns->last_pid that we observed when
137 * we started looking for a pid.
138 *
139 * 'pid' is the pid that we eventually found.
140 */
141static void set_last_pid(struct pid_namespace *pid_ns, int base, int pid)
142{
143 int prev;
144 int last_write = base;
145 do {
146 prev = last_write;
147 last_write = cmpxchg(&pid_ns->last_pid, prev, pid);
148 } while ((prev != last_write) && (pid_before(base, last_write, pid)));
149}
150
151static int alloc_pidmap(struct pid_namespace *pid_ns)
152{
153 int i, offset, max_scan, pid, last = pid_ns->last_pid;
154 struct pidmap *map;
155
156 pid = last + 1;
157 if (pid >= pid_max)
158 pid = RESERVED_PIDS;
159 offset = pid & BITS_PER_PAGE_MASK;
160 map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
161 /*
162 * If last_pid points into the middle of the map->page we
163 * want to scan this bitmap block twice, the second time
164 * we start with offset == 0 (or RESERVED_PIDS).
165 */
166 max_scan = DIV_ROUND_UP(pid_max, BITS_PER_PAGE) - !offset;
167 for (i = 0; i <= max_scan; ++i) {
168 if (unlikely(!map->page)) {
169 void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
170 /*
171 * Free the page if someone raced with us
172 * installing it:
173 */
174 spin_lock_irq(&pidmap_lock);
175 if (!map->page) {
176 map->page = page;
177 page = NULL;
178 }
179 spin_unlock_irq(&pidmap_lock);
180 kfree(page);
181 if (unlikely(!map->page))
182 break;
183 }
184 if (likely(atomic_read(&map->nr_free))) {
185 for ( ; ; ) {
186 if (!test_and_set_bit(offset, map->page)) {
187 atomic_dec(&map->nr_free);
188 set_last_pid(pid_ns, last, pid);
189 return pid;
190 }
191 offset = find_next_offset(map, offset);
192 if (offset >= BITS_PER_PAGE)
193 break;
194 pid = mk_pid(pid_ns, map, offset);
195 if (pid >= pid_max)
196 break;
197 }
198 }
199 if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
200 ++map;
201 offset = 0;
202 } else {
203 map = &pid_ns->pidmap[0];
204 offset = RESERVED_PIDS;
205 if (unlikely(last == offset))
206 break;
207 }
208 pid = mk_pid(pid_ns, map, offset);
209 }
210 return -1;
211}
212
213int next_pidmap(struct pid_namespace *pid_ns, unsigned int last)
214{
215 int offset;
216 struct pidmap *map, *end;
217
218 if (last >= PID_MAX_LIMIT)
219 return -1;
220
221 offset = (last + 1) & BITS_PER_PAGE_MASK;
222 map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE];
223 end = &pid_ns->pidmap[PIDMAP_ENTRIES];
224 for (; map < end; map++, offset = 0) {
225 if (unlikely(!map->page))
226 continue;
227 offset = find_next_bit((map)->page, BITS_PER_PAGE, offset);
228 if (offset < BITS_PER_PAGE)
229 return mk_pid(pid_ns, map, offset);
230 }
231 return -1;
232}
233
234void put_pid(struct pid *pid)
235{
236 struct pid_namespace *ns;
237
238 if (!pid)
239 return;
240
241 ns = pid->numbers[pid->level].ns;
242 if ((atomic_read(&pid->count) == 1) ||
243 atomic_dec_and_test(&pid->count)) {
244 kmem_cache_free(ns->pid_cachep, pid);
245 put_pid_ns(ns);
246 }
247}
248EXPORT_SYMBOL_GPL(put_pid);
249
250static void delayed_put_pid(struct rcu_head *rhp)
251{
252 struct pid *pid = container_of(rhp, struct pid, rcu);
253 put_pid(pid);
254}
255
256void free_pid(struct pid *pid)
257{
258 /* We can be called with write_lock_irq(&tasklist_lock) held */
259 int i;
260 unsigned long flags;
261
262 spin_lock_irqsave(&pidmap_lock, flags);
263 for (i = 0; i <= pid->level; i++) {
264 struct upid *upid = pid->numbers + i;
265 struct pid_namespace *ns = upid->ns;
266 hlist_del_rcu(&upid->pid_chain);
267 switch(--ns->nr_hashed) {
268 case 2:
269 case 1:
270 /* When all that is left in the pid namespace
271 * is the reaper wake up the reaper. The reaper
272 * may be sleeping in zap_pid_ns_processes().
273 */
274 wake_up_process(ns->child_reaper);
275 break;
276 case PIDNS_HASH_ADDING:
277 /* Handle a fork failure of the first process */
278 WARN_ON(ns->child_reaper);
279 ns->nr_hashed = 0;
280 /* fall through */
281 case 0:
282 schedule_work(&ns->proc_work);
283 break;
284 }
285 }
286 spin_unlock_irqrestore(&pidmap_lock, flags);
287
288 for (i = 0; i <= pid->level; i++)
289 free_pidmap(pid->numbers + i);
290
291 call_rcu(&pid->rcu, delayed_put_pid);
292}
293
294struct pid *alloc_pid(struct pid_namespace *ns)
295{
296 struct pid *pid;
297 enum pid_type type;
298 int i, nr;
299 struct pid_namespace *tmp;
300 struct upid *upid;
301
302 pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
303 if (!pid)
304 goto out;
305
306 tmp = ns;
307 pid->level = ns->level;
308 for (i = ns->level; i >= 0; i--) {
309 nr = alloc_pidmap(tmp);
310 if (nr < 0)
311 goto out_free;
312
313 pid->numbers[i].nr = nr;
314 pid->numbers[i].ns = tmp;
315 tmp = tmp->parent;
316 }
317
318 if (unlikely(is_child_reaper(pid))) {
319 if (pid_ns_prepare_proc(ns))
320 goto out_free;
321 }
322
323 get_pid_ns(ns);
324 atomic_set(&pid->count, 1);
325 for (type = 0; type < PIDTYPE_MAX; ++type)
326 INIT_HLIST_HEAD(&pid->tasks[type]);
327
328 upid = pid->numbers + ns->level;
329 spin_lock_irq(&pidmap_lock);
330 if (!(ns->nr_hashed & PIDNS_HASH_ADDING))
331 goto out_unlock;
332 for ( ; upid >= pid->numbers; --upid) {
333 hlist_add_head_rcu(&upid->pid_chain,
334 &pid_hash[pid_hashfn(upid->nr, upid->ns)]);
335 upid->ns->nr_hashed++;
336 }
337 spin_unlock_irq(&pidmap_lock);
338
339out:
340 return pid;
341
342out_unlock:
343 spin_unlock_irq(&pidmap_lock);
344out_free:
345 while (++i <= ns->level)
346 free_pidmap(pid->numbers + i);
347
348 kmem_cache_free(ns->pid_cachep, pid);
349 pid = NULL;
350 goto out;
351}
352
353void disable_pid_allocation(struct pid_namespace *ns)
354{
355 spin_lock_irq(&pidmap_lock);
356 ns->nr_hashed &= ~PIDNS_HASH_ADDING;
357 spin_unlock_irq(&pidmap_lock);
358}
359
360struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
361{
362 struct upid *pnr;
363
364 hlist_for_each_entry_rcu(pnr,
365 &pid_hash[pid_hashfn(nr, ns)], pid_chain)
366 if (pnr->nr == nr && pnr->ns == ns)
367 return container_of(pnr, struct pid,
368 numbers[ns->level]);
369
370 return NULL;
371}
372EXPORT_SYMBOL_GPL(find_pid_ns);
373
374struct pid *find_vpid(int nr)
375{
376 return find_pid_ns(nr, task_active_pid_ns(current));
377}
378EXPORT_SYMBOL_GPL(find_vpid);
379
380/*
381 * attach_pid() must be called with the tasklist_lock write-held.
382 */
383void attach_pid(struct task_struct *task, enum pid_type type)
384{
385 struct pid_link *link = &task->pids[type];
386 hlist_add_head_rcu(&link->node, &link->pid->tasks[type]);
387}
388
389static void __change_pid(struct task_struct *task, enum pid_type type,
390 struct pid *new)
391{
392 struct pid_link *link;
393 struct pid *pid;
394 int tmp;
395
396 link = &task->pids[type];
397 pid = link->pid;
398
399 hlist_del_rcu(&link->node);
400 link->pid = new;
401
402 for (tmp = PIDTYPE_MAX; --tmp >= 0; )
403 if (!hlist_empty(&pid->tasks[tmp]))
404 return;
405
406 free_pid(pid);
407}
408
409void detach_pid(struct task_struct *task, enum pid_type type)
410{
411 __change_pid(task, type, NULL);
412}
413
414void change_pid(struct task_struct *task, enum pid_type type,
415 struct pid *pid)
416{
417 __change_pid(task, type, pid);
418 attach_pid(task, type);
419}
420
421/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
422void transfer_pid(struct task_struct *old, struct task_struct *new,
423 enum pid_type type)
424{
425 new->pids[type].pid = old->pids[type].pid;
426 hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node);
427}
428
429struct task_struct *pid_task(struct pid *pid, enum pid_type type)
430{
431 struct task_struct *result = NULL;
432 if (pid) {
433 struct hlist_node *first;
434 first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
435 lockdep_tasklist_lock_is_held());
436 if (first)
437 result = hlist_entry(first, struct task_struct, pids[(type)].node);
438 }
439 return result;
440}
441EXPORT_SYMBOL(pid_task);
442
443/*
444 * Must be called under rcu_read_lock().
445 */
446struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
447{
448 rcu_lockdep_assert(rcu_read_lock_held(),
449 "find_task_by_pid_ns() needs rcu_read_lock()"
450 " protection");
451 return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
452}
453
454struct task_struct *find_task_by_vpid(pid_t vnr)
455{
456 return find_task_by_pid_ns(vnr, task_active_pid_ns(current));
457}
458
459struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
460{
461 struct pid *pid;
462 rcu_read_lock();
463 if (type != PIDTYPE_PID)
464 task = task->group_leader;
465 pid = get_pid(task->pids[type].pid);
466 rcu_read_unlock();
467 return pid;
468}
469EXPORT_SYMBOL_GPL(get_task_pid);
470
471struct task_struct *get_pid_task(struct pid *pid, enum pid_type type)
472{
473 struct task_struct *result;
474 rcu_read_lock();
475 result = pid_task(pid, type);
476 if (result)
477 get_task_struct(result);
478 rcu_read_unlock();
479 return result;
480}
481EXPORT_SYMBOL_GPL(get_pid_task);
482
483struct pid *find_get_pid(pid_t nr)
484{
485 struct pid *pid;
486
487 rcu_read_lock();
488 pid = get_pid(find_vpid(nr));
489 rcu_read_unlock();
490
491 return pid;
492}
493EXPORT_SYMBOL_GPL(find_get_pid);
494
495pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
496{
497 struct upid *upid;
498 pid_t nr = 0;
499
500 if (pid && ns->level <= pid->level) {
501 upid = &pid->numbers[ns->level];
502 if (upid->ns == ns)
503 nr = upid->nr;
504 }
505 return nr;
506}
507EXPORT_SYMBOL_GPL(pid_nr_ns);
508
509pid_t pid_vnr(struct pid *pid)
510{
511 return pid_nr_ns(pid, task_active_pid_ns(current));
512}
513EXPORT_SYMBOL_GPL(pid_vnr);
514
515pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
516 struct pid_namespace *ns)
517{
518 pid_t nr = 0;
519
520 rcu_read_lock();
521 if (!ns)
522 ns = task_active_pid_ns(current);
523 if (likely(pid_alive(task))) {
524 if (type != PIDTYPE_PID)
525 task = task->group_leader;
526 nr = pid_nr_ns(task->pids[type].pid, ns);
527 }
528 rcu_read_unlock();
529
530 return nr;
531}
532EXPORT_SYMBOL(__task_pid_nr_ns);
533
534pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
535{
536 return pid_nr_ns(task_tgid(tsk), ns);
537}
538EXPORT_SYMBOL(task_tgid_nr_ns);
539
540struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
541{
542 return ns_of_pid(task_pid(tsk));
543}
544EXPORT_SYMBOL_GPL(task_active_pid_ns);
545
546/*
547 * Used by proc to find the first pid that is greater than or equal to nr.
548 *
549 * If there is a pid at nr this function is exactly the same as find_pid_ns.
550 */
551struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
552{
553 struct pid *pid;
554
555 do {
556 pid = find_pid_ns(nr, ns);
557 if (pid)
558 break;
559 nr = next_pidmap(ns, nr);
560 } while (nr > 0);
561
562 return pid;
563}
564
565/*
566 * The pid hash table is scaled according to the amount of memory in the
567 * machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or
568 * more.
569 */
570void __init pidhash_init(void)
571{
572 unsigned int i, pidhash_size;
573
574 pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,
575 HASH_EARLY | HASH_SMALL,
576 &pidhash_shift, NULL,
577 0, 4096);
578 pidhash_size = 1U << pidhash_shift;
579
580 for (i = 0; i < pidhash_size; i++)
581 INIT_HLIST_HEAD(&pid_hash[i]);
582}
583
584void __init pidmap_init(void)
585{
586 /* Veryify no one has done anything silly */
587 BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_HASH_ADDING);
588
589 /* bump default and minimum pid_max based on number of cpus */
590 pid_max = min(pid_max_max, max_t(int, pid_max,
591 PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
592 pid_max_min = max_t(int, pid_max_min,
593 PIDS_PER_CPU_MIN * num_possible_cpus());
594 pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
595
596 init_pid_ns.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
597 /* Reserve PID 0. We never call free_pidmap(0) */
598 set_bit(0, init_pid_ns.pidmap[0].page);
599 atomic_dec(&init_pid_ns.pidmap[0].nr_free);
600
601 init_pid_ns.pid_cachep = KMEM_CACHE(pid,
602 SLAB_HWCACHE_ALIGN | SLAB_PANIC);
603}
1/*
2 * Generic pidhash and scalable, time-bounded PID allocator
3 *
4 * (C) 2002-2003 Nadia Yvette Chambers, IBM
5 * (C) 2004 Nadia Yvette Chambers, Oracle
6 * (C) 2002-2004 Ingo Molnar, Red Hat
7 *
8 * pid-structures are backing objects for tasks sharing a given ID to chain
9 * against. There is very little to them aside from hashing them and
10 * parking tasks using given ID's on a list.
11 *
12 * The hash is always changed with the tasklist_lock write-acquired,
13 * and the hash is only accessed with the tasklist_lock at least
14 * read-acquired, so there's no additional SMP locking needed here.
15 *
16 * We have a list of bitmap pages, which bitmaps represent the PID space.
17 * Allocating and freeing PIDs is completely lockless. The worst-case
18 * allocation scenario when all but one out of 1 million PIDs possible are
19 * allocated already: the scanning of 32 list entries and at most PAGE_SIZE
20 * bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
21 *
22 * Pid namespaces:
23 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
24 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
25 * Many thanks to Oleg Nesterov for comments and help
26 *
27 */
28
29#include <linux/mm.h>
30#include <linux/export.h>
31#include <linux/slab.h>
32#include <linux/init.h>
33#include <linux/rculist.h>
34#include <linux/bootmem.h>
35#include <linux/hash.h>
36#include <linux/pid_namespace.h>
37#include <linux/init_task.h>
38#include <linux/syscalls.h>
39#include <linux/proc_ns.h>
40#include <linux/proc_fs.h>
41#include <linux/sched/task.h>
42#include <linux/idr.h>
43
44struct pid init_struct_pid = {
45 .count = ATOMIC_INIT(1),
46 .tasks = {
47 { .first = NULL },
48 { .first = NULL },
49 { .first = NULL },
50 },
51 .level = 0,
52 .numbers = { {
53 .nr = 0,
54 .ns = &init_pid_ns,
55 }, }
56};
57
58int pid_max = PID_MAX_DEFAULT;
59
60#define RESERVED_PIDS 300
61
62int pid_max_min = RESERVED_PIDS + 1;
63int pid_max_max = PID_MAX_LIMIT;
64
65/*
66 * PID-map pages start out as NULL, they get allocated upon
67 * first use and are never deallocated. This way a low pid_max
68 * value does not cause lots of bitmaps to be allocated, but
69 * the scheme scales to up to 4 million PIDs, runtime.
70 */
71struct pid_namespace init_pid_ns = {
72 .kref = KREF_INIT(2),
73 .idr = IDR_INIT(init_pid_ns.idr),
74 .pid_allocated = PIDNS_ADDING,
75 .level = 0,
76 .child_reaper = &init_task,
77 .user_ns = &init_user_ns,
78 .ns.inum = PROC_PID_INIT_INO,
79#ifdef CONFIG_PID_NS
80 .ns.ops = &pidns_operations,
81#endif
82};
83EXPORT_SYMBOL_GPL(init_pid_ns);
84
85/*
86 * Note: disable interrupts while the pidmap_lock is held as an
87 * interrupt might come in and do read_lock(&tasklist_lock).
88 *
89 * If we don't disable interrupts there is a nasty deadlock between
90 * detach_pid()->free_pid() and another cpu that does
91 * spin_lock(&pidmap_lock) followed by an interrupt routine that does
92 * read_lock(&tasklist_lock);
93 *
94 * After we clean up the tasklist_lock and know there are no
95 * irq handlers that take it we can leave the interrupts enabled.
96 * For now it is easier to be safe than to prove it can't happen.
97 */
98
99static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
100
101void put_pid(struct pid *pid)
102{
103 struct pid_namespace *ns;
104
105 if (!pid)
106 return;
107
108 ns = pid->numbers[pid->level].ns;
109 if ((atomic_read(&pid->count) == 1) ||
110 atomic_dec_and_test(&pid->count)) {
111 kmem_cache_free(ns->pid_cachep, pid);
112 put_pid_ns(ns);
113 }
114}
115EXPORT_SYMBOL_GPL(put_pid);
116
117static void delayed_put_pid(struct rcu_head *rhp)
118{
119 struct pid *pid = container_of(rhp, struct pid, rcu);
120 put_pid(pid);
121}
122
123void free_pid(struct pid *pid)
124{
125 /* We can be called with write_lock_irq(&tasklist_lock) held */
126 int i;
127 unsigned long flags;
128
129 spin_lock_irqsave(&pidmap_lock, flags);
130 for (i = 0; i <= pid->level; i++) {
131 struct upid *upid = pid->numbers + i;
132 struct pid_namespace *ns = upid->ns;
133 switch (--ns->pid_allocated) {
134 case 2:
135 case 1:
136 /* When all that is left in the pid namespace
137 * is the reaper wake up the reaper. The reaper
138 * may be sleeping in zap_pid_ns_processes().
139 */
140 wake_up_process(ns->child_reaper);
141 break;
142 case PIDNS_ADDING:
143 /* Handle a fork failure of the first process */
144 WARN_ON(ns->child_reaper);
145 ns->pid_allocated = 0;
146 /* fall through */
147 case 0:
148 schedule_work(&ns->proc_work);
149 break;
150 }
151
152 idr_remove(&ns->idr, upid->nr);
153 }
154 spin_unlock_irqrestore(&pidmap_lock, flags);
155
156 call_rcu(&pid->rcu, delayed_put_pid);
157}
158
159struct pid *alloc_pid(struct pid_namespace *ns)
160{
161 struct pid *pid;
162 enum pid_type type;
163 int i, nr;
164 struct pid_namespace *tmp;
165 struct upid *upid;
166 int retval = -ENOMEM;
167
168 pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
169 if (!pid)
170 return ERR_PTR(retval);
171
172 tmp = ns;
173 pid->level = ns->level;
174
175 for (i = ns->level; i >= 0; i--) {
176 int pid_min = 1;
177
178 idr_preload(GFP_KERNEL);
179 spin_lock_irq(&pidmap_lock);
180
181 /*
182 * init really needs pid 1, but after reaching the maximum
183 * wrap back to RESERVED_PIDS
184 */
185 if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
186 pid_min = RESERVED_PIDS;
187
188 /*
189 * Store a null pointer so find_pid_ns does not find
190 * a partially initialized PID (see below).
191 */
192 nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
193 pid_max, GFP_ATOMIC);
194 spin_unlock_irq(&pidmap_lock);
195 idr_preload_end();
196
197 if (nr < 0) {
198 retval = nr;
199 goto out_free;
200 }
201
202 pid->numbers[i].nr = nr;
203 pid->numbers[i].ns = tmp;
204 tmp = tmp->parent;
205 }
206
207 if (unlikely(is_child_reaper(pid))) {
208 if (pid_ns_prepare_proc(ns))
209 goto out_free;
210 }
211
212 get_pid_ns(ns);
213 atomic_set(&pid->count, 1);
214 for (type = 0; type < PIDTYPE_MAX; ++type)
215 INIT_HLIST_HEAD(&pid->tasks[type]);
216
217 upid = pid->numbers + ns->level;
218 spin_lock_irq(&pidmap_lock);
219 if (!(ns->pid_allocated & PIDNS_ADDING))
220 goto out_unlock;
221 for ( ; upid >= pid->numbers; --upid) {
222 /* Make the PID visible to find_pid_ns. */
223 idr_replace(&upid->ns->idr, pid, upid->nr);
224 upid->ns->pid_allocated++;
225 }
226 spin_unlock_irq(&pidmap_lock);
227
228 return pid;
229
230out_unlock:
231 spin_unlock_irq(&pidmap_lock);
232 put_pid_ns(ns);
233
234out_free:
235 spin_lock_irq(&pidmap_lock);
236 while (++i <= ns->level)
237 idr_remove(&ns->idr, (pid->numbers + i)->nr);
238
239 /* On failure to allocate the first pid, reset the state */
240 if (ns->pid_allocated == PIDNS_ADDING)
241 idr_set_cursor(&ns->idr, 0);
242
243 spin_unlock_irq(&pidmap_lock);
244
245 kmem_cache_free(ns->pid_cachep, pid);
246 return ERR_PTR(retval);
247}
248
249void disable_pid_allocation(struct pid_namespace *ns)
250{
251 spin_lock_irq(&pidmap_lock);
252 ns->pid_allocated &= ~PIDNS_ADDING;
253 spin_unlock_irq(&pidmap_lock);
254}
255
256struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
257{
258 return idr_find(&ns->idr, nr);
259}
260EXPORT_SYMBOL_GPL(find_pid_ns);
261
262struct pid *find_vpid(int nr)
263{
264 return find_pid_ns(nr, task_active_pid_ns(current));
265}
266EXPORT_SYMBOL_GPL(find_vpid);
267
268/*
269 * attach_pid() must be called with the tasklist_lock write-held.
270 */
271void attach_pid(struct task_struct *task, enum pid_type type)
272{
273 struct pid_link *link = &task->pids[type];
274 hlist_add_head_rcu(&link->node, &link->pid->tasks[type]);
275}
276
277static void __change_pid(struct task_struct *task, enum pid_type type,
278 struct pid *new)
279{
280 struct pid_link *link;
281 struct pid *pid;
282 int tmp;
283
284 link = &task->pids[type];
285 pid = link->pid;
286
287 hlist_del_rcu(&link->node);
288 link->pid = new;
289
290 for (tmp = PIDTYPE_MAX; --tmp >= 0; )
291 if (!hlist_empty(&pid->tasks[tmp]))
292 return;
293
294 free_pid(pid);
295}
296
297void detach_pid(struct task_struct *task, enum pid_type type)
298{
299 __change_pid(task, type, NULL);
300}
301
302void change_pid(struct task_struct *task, enum pid_type type,
303 struct pid *pid)
304{
305 __change_pid(task, type, pid);
306 attach_pid(task, type);
307}
308
309/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
310void transfer_pid(struct task_struct *old, struct task_struct *new,
311 enum pid_type type)
312{
313 new->pids[type].pid = old->pids[type].pid;
314 hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node);
315}
316
317struct task_struct *pid_task(struct pid *pid, enum pid_type type)
318{
319 struct task_struct *result = NULL;
320 if (pid) {
321 struct hlist_node *first;
322 first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
323 lockdep_tasklist_lock_is_held());
324 if (first)
325 result = hlist_entry(first, struct task_struct, pids[(type)].node);
326 }
327 return result;
328}
329EXPORT_SYMBOL(pid_task);
330
331/*
332 * Must be called under rcu_read_lock().
333 */
334struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
335{
336 RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
337 "find_task_by_pid_ns() needs rcu_read_lock() protection");
338 return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
339}
340
341struct task_struct *find_task_by_vpid(pid_t vnr)
342{
343 return find_task_by_pid_ns(vnr, task_active_pid_ns(current));
344}
345
346struct task_struct *find_get_task_by_vpid(pid_t nr)
347{
348 struct task_struct *task;
349
350 rcu_read_lock();
351 task = find_task_by_vpid(nr);
352 if (task)
353 get_task_struct(task);
354 rcu_read_unlock();
355
356 return task;
357}
358
359struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
360{
361 struct pid *pid;
362 rcu_read_lock();
363 if (type != PIDTYPE_PID)
364 task = task->group_leader;
365 pid = get_pid(rcu_dereference(task->pids[type].pid));
366 rcu_read_unlock();
367 return pid;
368}
369EXPORT_SYMBOL_GPL(get_task_pid);
370
371struct task_struct *get_pid_task(struct pid *pid, enum pid_type type)
372{
373 struct task_struct *result;
374 rcu_read_lock();
375 result = pid_task(pid, type);
376 if (result)
377 get_task_struct(result);
378 rcu_read_unlock();
379 return result;
380}
381EXPORT_SYMBOL_GPL(get_pid_task);
382
383struct pid *find_get_pid(pid_t nr)
384{
385 struct pid *pid;
386
387 rcu_read_lock();
388 pid = get_pid(find_vpid(nr));
389 rcu_read_unlock();
390
391 return pid;
392}
393EXPORT_SYMBOL_GPL(find_get_pid);
394
395pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
396{
397 struct upid *upid;
398 pid_t nr = 0;
399
400 if (pid && ns->level <= pid->level) {
401 upid = &pid->numbers[ns->level];
402 if (upid->ns == ns)
403 nr = upid->nr;
404 }
405 return nr;
406}
407EXPORT_SYMBOL_GPL(pid_nr_ns);
408
409pid_t pid_vnr(struct pid *pid)
410{
411 return pid_nr_ns(pid, task_active_pid_ns(current));
412}
413EXPORT_SYMBOL_GPL(pid_vnr);
414
415pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
416 struct pid_namespace *ns)
417{
418 pid_t nr = 0;
419
420 rcu_read_lock();
421 if (!ns)
422 ns = task_active_pid_ns(current);
423 if (likely(pid_alive(task))) {
424 if (type != PIDTYPE_PID) {
425 if (type == __PIDTYPE_TGID)
426 type = PIDTYPE_PID;
427
428 task = task->group_leader;
429 }
430 nr = pid_nr_ns(rcu_dereference(task->pids[type].pid), ns);
431 }
432 rcu_read_unlock();
433
434 return nr;
435}
436EXPORT_SYMBOL(__task_pid_nr_ns);
437
438struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
439{
440 return ns_of_pid(task_pid(tsk));
441}
442EXPORT_SYMBOL_GPL(task_active_pid_ns);
443
444/*
445 * Used by proc to find the first pid that is greater than or equal to nr.
446 *
447 * If there is a pid at nr this function is exactly the same as find_pid_ns.
448 */
449struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
450{
451 return idr_get_next(&ns->idr, &nr);
452}
453
454void __init pid_idr_init(void)
455{
456 /* Verify no one has done anything silly: */
457 BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING);
458
459 /* bump default and minimum pid_max based on number of cpus */
460 pid_max = min(pid_max_max, max_t(int, pid_max,
461 PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
462 pid_max_min = max_t(int, pid_max_min,
463 PIDS_PER_CPU_MIN * num_possible_cpus());
464 pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
465
466 idr_init(&init_pid_ns.idr);
467
468 init_pid_ns.pid_cachep = KMEM_CACHE(pid,
469 SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
470}