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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Generic pidhash and scalable, time-bounded PID allocator
4 *
5 * (C) 2002-2003 Nadia Yvette Chambers, IBM
6 * (C) 2004 Nadia Yvette Chambers, Oracle
7 * (C) 2002-2004 Ingo Molnar, Red Hat
8 *
9 * pid-structures are backing objects for tasks sharing a given ID to chain
10 * against. There is very little to them aside from hashing them and
11 * parking tasks using given ID's on a list.
12 *
13 * The hash is always changed with the tasklist_lock write-acquired,
14 * and the hash is only accessed with the tasklist_lock at least
15 * read-acquired, so there's no additional SMP locking needed here.
16 *
17 * We have a list of bitmap pages, which bitmaps represent the PID space.
18 * Allocating and freeing PIDs is completely lockless. The worst-case
19 * allocation scenario when all but one out of 1 million PIDs possible are
20 * allocated already: the scanning of 32 list entries and at most PAGE_SIZE
21 * bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
22 *
23 * Pid namespaces:
24 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
25 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
26 * Many thanks to Oleg Nesterov for comments and help
27 *
28 */
29
30#include <linux/mm.h>
31#include <linux/export.h>
32#include <linux/slab.h>
33#include <linux/init.h>
34#include <linux/rculist.h>
35#include <linux/memblock.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/refcount.h>
41#include <linux/anon_inodes.h>
42#include <linux/sched/signal.h>
43#include <linux/sched/task.h>
44#include <linux/idr.h>
45
46struct pid init_struct_pid = {
47 .count = REFCOUNT_INIT(1),
48 .tasks = {
49 { .first = NULL },
50 { .first = NULL },
51 { .first = NULL },
52 },
53 .level = 0,
54 .numbers = { {
55 .nr = 0,
56 .ns = &init_pid_ns,
57 }, }
58};
59
60int pid_max = PID_MAX_DEFAULT;
61
62#define RESERVED_PIDS 300
63
64int pid_max_min = RESERVED_PIDS + 1;
65int pid_max_max = PID_MAX_LIMIT;
66
67/*
68 * PID-map pages start out as NULL, they get allocated upon
69 * first use and are never deallocated. This way a low pid_max
70 * value does not cause lots of bitmaps to be allocated, but
71 * the scheme scales to up to 4 million PIDs, runtime.
72 */
73struct pid_namespace init_pid_ns = {
74 .kref = KREF_INIT(2),
75 .idr = IDR_INIT(init_pid_ns.idr),
76 .pid_allocated = PIDNS_ADDING,
77 .level = 0,
78 .child_reaper = &init_task,
79 .user_ns = &init_user_ns,
80 .ns.inum = PROC_PID_INIT_INO,
81#ifdef CONFIG_PID_NS
82 .ns.ops = &pidns_operations,
83#endif
84};
85EXPORT_SYMBOL_GPL(init_pid_ns);
86
87/*
88 * Note: disable interrupts while the pidmap_lock is held as an
89 * interrupt might come in and do read_lock(&tasklist_lock).
90 *
91 * If we don't disable interrupts there is a nasty deadlock between
92 * detach_pid()->free_pid() and another cpu that does
93 * spin_lock(&pidmap_lock) followed by an interrupt routine that does
94 * read_lock(&tasklist_lock);
95 *
96 * After we clean up the tasklist_lock and know there are no
97 * irq handlers that take it we can leave the interrupts enabled.
98 * For now it is easier to be safe than to prove it can't happen.
99 */
100
101static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
102
103void put_pid(struct pid *pid)
104{
105 struct pid_namespace *ns;
106
107 if (!pid)
108 return;
109
110 ns = pid->numbers[pid->level].ns;
111 if (refcount_dec_and_test(&pid->count)) {
112 kmem_cache_free(ns->pid_cachep, pid);
113 put_pid_ns(ns);
114 }
115}
116EXPORT_SYMBOL_GPL(put_pid);
117
118static void delayed_put_pid(struct rcu_head *rhp)
119{
120 struct pid *pid = container_of(rhp, struct pid, rcu);
121 put_pid(pid);
122}
123
124void free_pid(struct pid *pid)
125{
126 /* We can be called with write_lock_irq(&tasklist_lock) held */
127 int i;
128 unsigned long flags;
129
130 spin_lock_irqsave(&pidmap_lock, flags);
131 for (i = 0; i <= pid->level; i++) {
132 struct upid *upid = pid->numbers + i;
133 struct pid_namespace *ns = upid->ns;
134 switch (--ns->pid_allocated) {
135 case 2:
136 case 1:
137 /* When all that is left in the pid namespace
138 * is the reaper wake up the reaper. The reaper
139 * may be sleeping in zap_pid_ns_processes().
140 */
141 wake_up_process(ns->child_reaper);
142 break;
143 case PIDNS_ADDING:
144 /* Handle a fork failure of the first process */
145 WARN_ON(ns->child_reaper);
146 ns->pid_allocated = 0;
147 /* fall through */
148 case 0:
149 schedule_work(&ns->proc_work);
150 break;
151 }
152
153 idr_remove(&ns->idr, upid->nr);
154 }
155 spin_unlock_irqrestore(&pidmap_lock, flags);
156
157 call_rcu(&pid->rcu, delayed_put_pid);
158}
159
160struct pid *alloc_pid(struct pid_namespace *ns)
161{
162 struct pid *pid;
163 enum pid_type type;
164 int i, nr;
165 struct pid_namespace *tmp;
166 struct upid *upid;
167 int retval = -ENOMEM;
168
169 pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
170 if (!pid)
171 return ERR_PTR(retval);
172
173 tmp = ns;
174 pid->level = ns->level;
175
176 for (i = ns->level; i >= 0; i--) {
177 int pid_min = 1;
178
179 idr_preload(GFP_KERNEL);
180 spin_lock_irq(&pidmap_lock);
181
182 /*
183 * init really needs pid 1, but after reaching the maximum
184 * wrap back to RESERVED_PIDS
185 */
186 if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS)
187 pid_min = RESERVED_PIDS;
188
189 /*
190 * Store a null pointer so find_pid_ns does not find
191 * a partially initialized PID (see below).
192 */
193 nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min,
194 pid_max, GFP_ATOMIC);
195 spin_unlock_irq(&pidmap_lock);
196 idr_preload_end();
197
198 if (nr < 0) {
199 retval = (nr == -ENOSPC) ? -EAGAIN : nr;
200 goto out_free;
201 }
202
203 pid->numbers[i].nr = nr;
204 pid->numbers[i].ns = tmp;
205 tmp = tmp->parent;
206 }
207
208 if (unlikely(is_child_reaper(pid))) {
209 if (pid_ns_prepare_proc(ns))
210 goto out_free;
211 }
212
213 get_pid_ns(ns);
214 refcount_set(&pid->count, 1);
215 for (type = 0; type < PIDTYPE_MAX; ++type)
216 INIT_HLIST_HEAD(&pid->tasks[type]);
217
218 init_waitqueue_head(&pid->wait_pidfd);
219
220 upid = pid->numbers + ns->level;
221 spin_lock_irq(&pidmap_lock);
222 if (!(ns->pid_allocated & PIDNS_ADDING))
223 goto out_unlock;
224 for ( ; upid >= pid->numbers; --upid) {
225 /* Make the PID visible to find_pid_ns. */
226 idr_replace(&upid->ns->idr, pid, upid->nr);
227 upid->ns->pid_allocated++;
228 }
229 spin_unlock_irq(&pidmap_lock);
230
231 return pid;
232
233out_unlock:
234 spin_unlock_irq(&pidmap_lock);
235 put_pid_ns(ns);
236
237out_free:
238 spin_lock_irq(&pidmap_lock);
239 while (++i <= ns->level) {
240 upid = pid->numbers + i;
241 idr_remove(&upid->ns->idr, upid->nr);
242 }
243
244 /* On failure to allocate the first pid, reset the state */
245 if (ns->pid_allocated == PIDNS_ADDING)
246 idr_set_cursor(&ns->idr, 0);
247
248 spin_unlock_irq(&pidmap_lock);
249
250 kmem_cache_free(ns->pid_cachep, pid);
251 return ERR_PTR(retval);
252}
253
254void disable_pid_allocation(struct pid_namespace *ns)
255{
256 spin_lock_irq(&pidmap_lock);
257 ns->pid_allocated &= ~PIDNS_ADDING;
258 spin_unlock_irq(&pidmap_lock);
259}
260
261struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
262{
263 return idr_find(&ns->idr, nr);
264}
265EXPORT_SYMBOL_GPL(find_pid_ns);
266
267struct pid *find_vpid(int nr)
268{
269 return find_pid_ns(nr, task_active_pid_ns(current));
270}
271EXPORT_SYMBOL_GPL(find_vpid);
272
273static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type)
274{
275 return (type == PIDTYPE_PID) ?
276 &task->thread_pid :
277 &task->signal->pids[type];
278}
279
280/*
281 * attach_pid() must be called with the tasklist_lock write-held.
282 */
283void attach_pid(struct task_struct *task, enum pid_type type)
284{
285 struct pid *pid = *task_pid_ptr(task, type);
286 hlist_add_head_rcu(&task->pid_links[type], &pid->tasks[type]);
287}
288
289static void __change_pid(struct task_struct *task, enum pid_type type,
290 struct pid *new)
291{
292 struct pid **pid_ptr = task_pid_ptr(task, type);
293 struct pid *pid;
294 int tmp;
295
296 pid = *pid_ptr;
297
298 hlist_del_rcu(&task->pid_links[type]);
299 *pid_ptr = new;
300
301 for (tmp = PIDTYPE_MAX; --tmp >= 0; )
302 if (!hlist_empty(&pid->tasks[tmp]))
303 return;
304
305 free_pid(pid);
306}
307
308void detach_pid(struct task_struct *task, enum pid_type type)
309{
310 __change_pid(task, type, NULL);
311}
312
313void change_pid(struct task_struct *task, enum pid_type type,
314 struct pid *pid)
315{
316 __change_pid(task, type, pid);
317 attach_pid(task, type);
318}
319
320/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
321void transfer_pid(struct task_struct *old, struct task_struct *new,
322 enum pid_type type)
323{
324 if (type == PIDTYPE_PID)
325 new->thread_pid = old->thread_pid;
326 hlist_replace_rcu(&old->pid_links[type], &new->pid_links[type]);
327}
328
329struct task_struct *pid_task(struct pid *pid, enum pid_type type)
330{
331 struct task_struct *result = NULL;
332 if (pid) {
333 struct hlist_node *first;
334 first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
335 lockdep_tasklist_lock_is_held());
336 if (first)
337 result = hlist_entry(first, struct task_struct, pid_links[(type)]);
338 }
339 return result;
340}
341EXPORT_SYMBOL(pid_task);
342
343/*
344 * Must be called under rcu_read_lock().
345 */
346struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
347{
348 RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
349 "find_task_by_pid_ns() needs rcu_read_lock() protection");
350 return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
351}
352
353struct task_struct *find_task_by_vpid(pid_t vnr)
354{
355 return find_task_by_pid_ns(vnr, task_active_pid_ns(current));
356}
357
358struct task_struct *find_get_task_by_vpid(pid_t nr)
359{
360 struct task_struct *task;
361
362 rcu_read_lock();
363 task = find_task_by_vpid(nr);
364 if (task)
365 get_task_struct(task);
366 rcu_read_unlock();
367
368 return task;
369}
370
371struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
372{
373 struct pid *pid;
374 rcu_read_lock();
375 pid = get_pid(rcu_dereference(*task_pid_ptr(task, type)));
376 rcu_read_unlock();
377 return pid;
378}
379EXPORT_SYMBOL_GPL(get_task_pid);
380
381struct task_struct *get_pid_task(struct pid *pid, enum pid_type type)
382{
383 struct task_struct *result;
384 rcu_read_lock();
385 result = pid_task(pid, type);
386 if (result)
387 get_task_struct(result);
388 rcu_read_unlock();
389 return result;
390}
391EXPORT_SYMBOL_GPL(get_pid_task);
392
393struct pid *find_get_pid(pid_t nr)
394{
395 struct pid *pid;
396
397 rcu_read_lock();
398 pid = get_pid(find_vpid(nr));
399 rcu_read_unlock();
400
401 return pid;
402}
403EXPORT_SYMBOL_GPL(find_get_pid);
404
405pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
406{
407 struct upid *upid;
408 pid_t nr = 0;
409
410 if (pid && ns->level <= pid->level) {
411 upid = &pid->numbers[ns->level];
412 if (upid->ns == ns)
413 nr = upid->nr;
414 }
415 return nr;
416}
417EXPORT_SYMBOL_GPL(pid_nr_ns);
418
419pid_t pid_vnr(struct pid *pid)
420{
421 return pid_nr_ns(pid, task_active_pid_ns(current));
422}
423EXPORT_SYMBOL_GPL(pid_vnr);
424
425pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
426 struct pid_namespace *ns)
427{
428 pid_t nr = 0;
429
430 rcu_read_lock();
431 if (!ns)
432 ns = task_active_pid_ns(current);
433 if (likely(pid_alive(task)))
434 nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
435 rcu_read_unlock();
436
437 return nr;
438}
439EXPORT_SYMBOL(__task_pid_nr_ns);
440
441struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
442{
443 return ns_of_pid(task_pid(tsk));
444}
445EXPORT_SYMBOL_GPL(task_active_pid_ns);
446
447/*
448 * Used by proc to find the first pid that is greater than or equal to nr.
449 *
450 * If there is a pid at nr this function is exactly the same as find_pid_ns.
451 */
452struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
453{
454 return idr_get_next(&ns->idr, &nr);
455}
456
457/**
458 * pidfd_create() - Create a new pid file descriptor.
459 *
460 * @pid: struct pid that the pidfd will reference
461 *
462 * This creates a new pid file descriptor with the O_CLOEXEC flag set.
463 *
464 * Note, that this function can only be called after the fd table has
465 * been unshared to avoid leaking the pidfd to the new process.
466 *
467 * Return: On success, a cloexec pidfd is returned.
468 * On error, a negative errno number will be returned.
469 */
470static int pidfd_create(struct pid *pid)
471{
472 int fd;
473
474 fd = anon_inode_getfd("[pidfd]", &pidfd_fops, get_pid(pid),
475 O_RDWR | O_CLOEXEC);
476 if (fd < 0)
477 put_pid(pid);
478
479 return fd;
480}
481
482/**
483 * pidfd_open() - Open new pid file descriptor.
484 *
485 * @pid: pid for which to retrieve a pidfd
486 * @flags: flags to pass
487 *
488 * This creates a new pid file descriptor with the O_CLOEXEC flag set for
489 * the process identified by @pid. Currently, the process identified by
490 * @pid must be a thread-group leader. This restriction currently exists
491 * for all aspects of pidfds including pidfd creation (CLONE_PIDFD cannot
492 * be used with CLONE_THREAD) and pidfd polling (only supports thread group
493 * leaders).
494 *
495 * Return: On success, a cloexec pidfd is returned.
496 * On error, a negative errno number will be returned.
497 */
498SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
499{
500 int fd, ret;
501 struct pid *p;
502
503 if (flags)
504 return -EINVAL;
505
506 if (pid <= 0)
507 return -EINVAL;
508
509 p = find_get_pid(pid);
510 if (!p)
511 return -ESRCH;
512
513 ret = 0;
514 rcu_read_lock();
515 if (!pid_task(p, PIDTYPE_TGID))
516 ret = -EINVAL;
517 rcu_read_unlock();
518
519 fd = ret ?: pidfd_create(p);
520 put_pid(p);
521 return fd;
522}
523
524void __init pid_idr_init(void)
525{
526 /* Verify no one has done anything silly: */
527 BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING);
528
529 /* bump default and minimum pid_max based on number of cpus */
530 pid_max = min(pid_max_max, max_t(int, pid_max,
531 PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
532 pid_max_min = max_t(int, pid_max_min,
533 PIDS_PER_CPU_MIN * num_possible_cpus());
534 pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
535
536 idr_init(&init_pid_ns.idr);
537
538 init_pid_ns.pid_cachep = KMEM_CACHE(pid,
539 SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT);
540}
1/*
2 * Generic pidhash and scalable, time-bounded PID allocator
3 *
4 * (C) 2002-2003 William Irwin, IBM
5 * (C) 2004 William Irwin, 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/module.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
40#define pid_hashfn(nr, ns) \
41 hash_long((unsigned long)nr + (unsigned long)ns, pidhash_shift)
42static struct hlist_head *pid_hash;
43static unsigned int pidhash_shift = 4;
44struct pid init_struct_pid = INIT_STRUCT_PID;
45
46int pid_max = PID_MAX_DEFAULT;
47
48#define RESERVED_PIDS 300
49
50int pid_max_min = RESERVED_PIDS + 1;
51int pid_max_max = PID_MAX_LIMIT;
52
53#define BITS_PER_PAGE (PAGE_SIZE*8)
54#define BITS_PER_PAGE_MASK (BITS_PER_PAGE-1)
55
56static inline int mk_pid(struct pid_namespace *pid_ns,
57 struct pidmap *map, int off)
58{
59 return (map - pid_ns->pidmap)*BITS_PER_PAGE + off;
60}
61
62#define find_next_offset(map, off) \
63 find_next_zero_bit((map)->page, BITS_PER_PAGE, off)
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 = {
73 .refcount = ATOMIC_INIT(2),
74 },
75 .pidmap = {
76 [ 0 ... PIDMAP_ENTRIES-1] = { ATOMIC_INIT(BITS_PER_PAGE), NULL }
77 },
78 .last_pid = 0,
79 .level = 0,
80 .child_reaper = &init_task,
81};
82EXPORT_SYMBOL_GPL(init_pid_ns);
83
84int is_container_init(struct task_struct *tsk)
85{
86 int ret = 0;
87 struct pid *pid;
88
89 rcu_read_lock();
90 pid = task_pid(tsk);
91 if (pid != NULL && pid->numbers[pid->level].nr == 1)
92 ret = 1;
93 rcu_read_unlock();
94
95 return ret;
96}
97EXPORT_SYMBOL(is_container_init);
98
99/*
100 * Note: disable interrupts while the pidmap_lock is held as an
101 * interrupt might come in and do read_lock(&tasklist_lock).
102 *
103 * If we don't disable interrupts there is a nasty deadlock between
104 * detach_pid()->free_pid() and another cpu that does
105 * spin_lock(&pidmap_lock) followed by an interrupt routine that does
106 * read_lock(&tasklist_lock);
107 *
108 * After we clean up the tasklist_lock and know there are no
109 * irq handlers that take it we can leave the interrupts enabled.
110 * For now it is easier to be safe than to prove it can't happen.
111 */
112
113static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
114
115static void free_pidmap(struct upid *upid)
116{
117 int nr = upid->nr;
118 struct pidmap *map = upid->ns->pidmap + nr / BITS_PER_PAGE;
119 int offset = nr & BITS_PER_PAGE_MASK;
120
121 clear_bit(offset, map->page);
122 atomic_inc(&map->nr_free);
123}
124
125/*
126 * If we started walking pids at 'base', is 'a' seen before 'b'?
127 */
128static int pid_before(int base, int a, int b)
129{
130 /*
131 * This is the same as saying
132 *
133 * (a - base + MAXUINT) % MAXUINT < (b - base + MAXUINT) % MAXUINT
134 * and that mapping orders 'a' and 'b' with respect to 'base'.
135 */
136 return (unsigned)(a - base) < (unsigned)(b - base);
137}
138
139/*
140 * We might be racing with someone else trying to set pid_ns->last_pid.
141 * We want the winner to have the "later" value, because if the
142 * "earlier" value prevails, then a pid may get reused immediately.
143 *
144 * Since pids rollover, it is not sufficient to just pick the bigger
145 * value. We have to consider where we started counting from.
146 *
147 * 'base' is the value of pid_ns->last_pid that we observed when
148 * we started looking for a pid.
149 *
150 * 'pid' is the pid that we eventually found.
151 */
152static void set_last_pid(struct pid_namespace *pid_ns, int base, int pid)
153{
154 int prev;
155 int last_write = base;
156 do {
157 prev = last_write;
158 last_write = cmpxchg(&pid_ns->last_pid, prev, pid);
159 } while ((prev != last_write) && (pid_before(base, last_write, pid)));
160}
161
162static int alloc_pidmap(struct pid_namespace *pid_ns)
163{
164 int i, offset, max_scan, pid, last = pid_ns->last_pid;
165 struct pidmap *map;
166
167 pid = last + 1;
168 if (pid >= pid_max)
169 pid = RESERVED_PIDS;
170 offset = pid & BITS_PER_PAGE_MASK;
171 map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
172 /*
173 * If last_pid points into the middle of the map->page we
174 * want to scan this bitmap block twice, the second time
175 * we start with offset == 0 (or RESERVED_PIDS).
176 */
177 max_scan = DIV_ROUND_UP(pid_max, BITS_PER_PAGE) - !offset;
178 for (i = 0; i <= max_scan; ++i) {
179 if (unlikely(!map->page)) {
180 void *page = kzalloc(PAGE_SIZE, GFP_KERNEL);
181 /*
182 * Free the page if someone raced with us
183 * installing it:
184 */
185 spin_lock_irq(&pidmap_lock);
186 if (!map->page) {
187 map->page = page;
188 page = NULL;
189 }
190 spin_unlock_irq(&pidmap_lock);
191 kfree(page);
192 if (unlikely(!map->page))
193 break;
194 }
195 if (likely(atomic_read(&map->nr_free))) {
196 do {
197 if (!test_and_set_bit(offset, map->page)) {
198 atomic_dec(&map->nr_free);
199 set_last_pid(pid_ns, last, pid);
200 return pid;
201 }
202 offset = find_next_offset(map, offset);
203 pid = mk_pid(pid_ns, map, offset);
204 } while (offset < BITS_PER_PAGE && pid < pid_max);
205 }
206 if (map < &pid_ns->pidmap[(pid_max-1)/BITS_PER_PAGE]) {
207 ++map;
208 offset = 0;
209 } else {
210 map = &pid_ns->pidmap[0];
211 offset = RESERVED_PIDS;
212 if (unlikely(last == offset))
213 break;
214 }
215 pid = mk_pid(pid_ns, map, offset);
216 }
217 return -1;
218}
219
220int next_pidmap(struct pid_namespace *pid_ns, unsigned int last)
221{
222 int offset;
223 struct pidmap *map, *end;
224
225 if (last >= PID_MAX_LIMIT)
226 return -1;
227
228 offset = (last + 1) & BITS_PER_PAGE_MASK;
229 map = &pid_ns->pidmap[(last + 1)/BITS_PER_PAGE];
230 end = &pid_ns->pidmap[PIDMAP_ENTRIES];
231 for (; map < end; map++, offset = 0) {
232 if (unlikely(!map->page))
233 continue;
234 offset = find_next_bit((map)->page, BITS_PER_PAGE, offset);
235 if (offset < BITS_PER_PAGE)
236 return mk_pid(pid_ns, map, offset);
237 }
238 return -1;
239}
240
241void put_pid(struct pid *pid)
242{
243 struct pid_namespace *ns;
244
245 if (!pid)
246 return;
247
248 ns = pid->numbers[pid->level].ns;
249 if ((atomic_read(&pid->count) == 1) ||
250 atomic_dec_and_test(&pid->count)) {
251 kmem_cache_free(ns->pid_cachep, pid);
252 put_pid_ns(ns);
253 }
254}
255EXPORT_SYMBOL_GPL(put_pid);
256
257static void delayed_put_pid(struct rcu_head *rhp)
258{
259 struct pid *pid = container_of(rhp, struct pid, rcu);
260 put_pid(pid);
261}
262
263void free_pid(struct pid *pid)
264{
265 /* We can be called with write_lock_irq(&tasklist_lock) held */
266 int i;
267 unsigned long flags;
268
269 spin_lock_irqsave(&pidmap_lock, flags);
270 for (i = 0; i <= pid->level; i++)
271 hlist_del_rcu(&pid->numbers[i].pid_chain);
272 spin_unlock_irqrestore(&pidmap_lock, flags);
273
274 for (i = 0; i <= pid->level; i++)
275 free_pidmap(pid->numbers + i);
276
277 call_rcu(&pid->rcu, delayed_put_pid);
278}
279
280struct pid *alloc_pid(struct pid_namespace *ns)
281{
282 struct pid *pid;
283 enum pid_type type;
284 int i, nr;
285 struct pid_namespace *tmp;
286 struct upid *upid;
287
288 pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
289 if (!pid)
290 goto out;
291
292 tmp = ns;
293 for (i = ns->level; i >= 0; i--) {
294 nr = alloc_pidmap(tmp);
295 if (nr < 0)
296 goto out_free;
297
298 pid->numbers[i].nr = nr;
299 pid->numbers[i].ns = tmp;
300 tmp = tmp->parent;
301 }
302
303 get_pid_ns(ns);
304 pid->level = ns->level;
305 atomic_set(&pid->count, 1);
306 for (type = 0; type < PIDTYPE_MAX; ++type)
307 INIT_HLIST_HEAD(&pid->tasks[type]);
308
309 upid = pid->numbers + ns->level;
310 spin_lock_irq(&pidmap_lock);
311 for ( ; upid >= pid->numbers; --upid)
312 hlist_add_head_rcu(&upid->pid_chain,
313 &pid_hash[pid_hashfn(upid->nr, upid->ns)]);
314 spin_unlock_irq(&pidmap_lock);
315
316out:
317 return pid;
318
319out_free:
320 while (++i <= ns->level)
321 free_pidmap(pid->numbers + i);
322
323 kmem_cache_free(ns->pid_cachep, pid);
324 pid = NULL;
325 goto out;
326}
327
328struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
329{
330 struct hlist_node *elem;
331 struct upid *pnr;
332
333 hlist_for_each_entry_rcu(pnr, elem,
334 &pid_hash[pid_hashfn(nr, ns)], pid_chain)
335 if (pnr->nr == nr && pnr->ns == ns)
336 return container_of(pnr, struct pid,
337 numbers[ns->level]);
338
339 return NULL;
340}
341EXPORT_SYMBOL_GPL(find_pid_ns);
342
343struct pid *find_vpid(int nr)
344{
345 return find_pid_ns(nr, current->nsproxy->pid_ns);
346}
347EXPORT_SYMBOL_GPL(find_vpid);
348
349/*
350 * attach_pid() must be called with the tasklist_lock write-held.
351 */
352void attach_pid(struct task_struct *task, enum pid_type type,
353 struct pid *pid)
354{
355 struct pid_link *link;
356
357 link = &task->pids[type];
358 link->pid = pid;
359 hlist_add_head_rcu(&link->node, &pid->tasks[type]);
360}
361
362static void __change_pid(struct task_struct *task, enum pid_type type,
363 struct pid *new)
364{
365 struct pid_link *link;
366 struct pid *pid;
367 int tmp;
368
369 link = &task->pids[type];
370 pid = link->pid;
371
372 hlist_del_rcu(&link->node);
373 link->pid = new;
374
375 for (tmp = PIDTYPE_MAX; --tmp >= 0; )
376 if (!hlist_empty(&pid->tasks[tmp]))
377 return;
378
379 free_pid(pid);
380}
381
382void detach_pid(struct task_struct *task, enum pid_type type)
383{
384 __change_pid(task, type, NULL);
385}
386
387void change_pid(struct task_struct *task, enum pid_type type,
388 struct pid *pid)
389{
390 __change_pid(task, type, pid);
391 attach_pid(task, type, pid);
392}
393
394/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
395void transfer_pid(struct task_struct *old, struct task_struct *new,
396 enum pid_type type)
397{
398 new->pids[type].pid = old->pids[type].pid;
399 hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node);
400}
401
402struct task_struct *pid_task(struct pid *pid, enum pid_type type)
403{
404 struct task_struct *result = NULL;
405 if (pid) {
406 struct hlist_node *first;
407 first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
408 lockdep_tasklist_lock_is_held());
409 if (first)
410 result = hlist_entry(first, struct task_struct, pids[(type)].node);
411 }
412 return result;
413}
414EXPORT_SYMBOL(pid_task);
415
416/*
417 * Must be called under rcu_read_lock().
418 */
419struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
420{
421 rcu_lockdep_assert(rcu_read_lock_held());
422 return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
423}
424
425struct task_struct *find_task_by_vpid(pid_t vnr)
426{
427 return find_task_by_pid_ns(vnr, current->nsproxy->pid_ns);
428}
429
430struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
431{
432 struct pid *pid;
433 rcu_read_lock();
434 if (type != PIDTYPE_PID)
435 task = task->group_leader;
436 pid = get_pid(task->pids[type].pid);
437 rcu_read_unlock();
438 return pid;
439}
440EXPORT_SYMBOL_GPL(get_task_pid);
441
442struct task_struct *get_pid_task(struct pid *pid, enum pid_type type)
443{
444 struct task_struct *result;
445 rcu_read_lock();
446 result = pid_task(pid, type);
447 if (result)
448 get_task_struct(result);
449 rcu_read_unlock();
450 return result;
451}
452EXPORT_SYMBOL_GPL(get_pid_task);
453
454struct pid *find_get_pid(pid_t nr)
455{
456 struct pid *pid;
457
458 rcu_read_lock();
459 pid = get_pid(find_vpid(nr));
460 rcu_read_unlock();
461
462 return pid;
463}
464EXPORT_SYMBOL_GPL(find_get_pid);
465
466pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
467{
468 struct upid *upid;
469 pid_t nr = 0;
470
471 if (pid && ns->level <= pid->level) {
472 upid = &pid->numbers[ns->level];
473 if (upid->ns == ns)
474 nr = upid->nr;
475 }
476 return nr;
477}
478
479pid_t pid_vnr(struct pid *pid)
480{
481 return pid_nr_ns(pid, current->nsproxy->pid_ns);
482}
483EXPORT_SYMBOL_GPL(pid_vnr);
484
485pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
486 struct pid_namespace *ns)
487{
488 pid_t nr = 0;
489
490 rcu_read_lock();
491 if (!ns)
492 ns = current->nsproxy->pid_ns;
493 if (likely(pid_alive(task))) {
494 if (type != PIDTYPE_PID)
495 task = task->group_leader;
496 nr = pid_nr_ns(task->pids[type].pid, ns);
497 }
498 rcu_read_unlock();
499
500 return nr;
501}
502EXPORT_SYMBOL(__task_pid_nr_ns);
503
504pid_t task_tgid_nr_ns(struct task_struct *tsk, struct pid_namespace *ns)
505{
506 return pid_nr_ns(task_tgid(tsk), ns);
507}
508EXPORT_SYMBOL(task_tgid_nr_ns);
509
510struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
511{
512 return ns_of_pid(task_pid(tsk));
513}
514EXPORT_SYMBOL_GPL(task_active_pid_ns);
515
516/*
517 * Used by proc to find the first pid that is greater than or equal to nr.
518 *
519 * If there is a pid at nr this function is exactly the same as find_pid_ns.
520 */
521struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
522{
523 struct pid *pid;
524
525 do {
526 pid = find_pid_ns(nr, ns);
527 if (pid)
528 break;
529 nr = next_pidmap(ns, nr);
530 } while (nr > 0);
531
532 return pid;
533}
534
535/*
536 * The pid hash table is scaled according to the amount of memory in the
537 * machine. From a minimum of 16 slots up to 4096 slots at one gigabyte or
538 * more.
539 */
540void __init pidhash_init(void)
541{
542 int i, pidhash_size;
543
544 pid_hash = alloc_large_system_hash("PID", sizeof(*pid_hash), 0, 18,
545 HASH_EARLY | HASH_SMALL,
546 &pidhash_shift, NULL, 4096);
547 pidhash_size = 1 << pidhash_shift;
548
549 for (i = 0; i < pidhash_size; i++)
550 INIT_HLIST_HEAD(&pid_hash[i]);
551}
552
553void __init pidmap_init(void)
554{
555 /* bump default and minimum pid_max based on number of cpus */
556 pid_max = min(pid_max_max, max_t(int, pid_max,
557 PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
558 pid_max_min = max_t(int, pid_max_min,
559 PIDS_PER_CPU_MIN * num_possible_cpus());
560 pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min);
561
562 init_pid_ns.pidmap[0].page = kzalloc(PAGE_SIZE, GFP_KERNEL);
563 /* Reserve PID 0. We never call free_pidmap(0) */
564 set_bit(0, init_pid_ns.pidmap[0].page);
565 atomic_dec(&init_pid_ns.pidmap[0].nr_free);
566
567 init_pid_ns.pid_cachep = KMEM_CACHE(pid,
568 SLAB_HWCACHE_ALIGN | SLAB_PANIC);
569}