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Commit | Line | Data |
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1da177e4 LT |
1 | /* |
2 | * Generic pidhash and scalable, time-bounded PID allocator | |
3 | * | |
6d49e352 NYC |
4 | * (C) 2002-2003 Nadia Yvette Chambers, IBM |
5 | * (C) 2004 Nadia Yvette Chambers, Oracle | |
1da177e4 LT |
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). | |
30e49c26 PE |
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 | * | |
1da177e4 LT |
27 | */ |
28 | ||
29 | #include <linux/mm.h> | |
9984de1a | 30 | #include <linux/export.h> |
1da177e4 LT |
31 | #include <linux/slab.h> |
32 | #include <linux/init.h> | |
82524746 | 33 | #include <linux/rculist.h> |
1da177e4 LT |
34 | #include <linux/bootmem.h> |
35 | #include <linux/hash.h> | |
61a58c6c | 36 | #include <linux/pid_namespace.h> |
820e45db | 37 | #include <linux/init_task.h> |
3eb07c8c | 38 | #include <linux/syscalls.h> |
0bb80f24 | 39 | #include <linux/proc_ns.h> |
0a01f2cc | 40 | #include <linux/proc_fs.h> |
29930025 | 41 | #include <linux/sched/task.h> |
95846ecf | 42 | #include <linux/idr.h> |
1da177e4 | 43 | |
820e45db | 44 | struct pid init_struct_pid = INIT_STRUCT_PID; |
1da177e4 LT |
45 | |
46 | int pid_max = PID_MAX_DEFAULT; | |
1da177e4 LT |
47 | |
48 | #define RESERVED_PIDS 300 | |
49 | ||
50 | int pid_max_min = RESERVED_PIDS + 1; | |
51 | int pid_max_max = PID_MAX_LIMIT; | |
52 | ||
1da177e4 LT |
53 | /* |
54 | * PID-map pages start out as NULL, they get allocated upon | |
55 | * first use and are never deallocated. This way a low pid_max | |
56 | * value does not cause lots of bitmaps to be allocated, but | |
57 | * the scheme scales to up to 4 million PIDs, runtime. | |
58 | */ | |
61a58c6c | 59 | struct pid_namespace init_pid_ns = { |
1e24edca | 60 | .kref = KREF_INIT(2), |
95846ecf | 61 | .idr = IDR_INIT, |
e8cfbc24 | 62 | .pid_allocated = PIDNS_ADDING, |
faacbfd3 PE |
63 | .level = 0, |
64 | .child_reaper = &init_task, | |
49f4d8b9 | 65 | .user_ns = &init_user_ns, |
435d5f4b | 66 | .ns.inum = PROC_PID_INIT_INO, |
33c42940 AV |
67 | #ifdef CONFIG_PID_NS |
68 | .ns.ops = &pidns_operations, | |
69 | #endif | |
3fbc9648 | 70 | }; |
198fe21b | 71 | EXPORT_SYMBOL_GPL(init_pid_ns); |
1da177e4 | 72 | |
92476d7f EB |
73 | /* |
74 | * Note: disable interrupts while the pidmap_lock is held as an | |
75 | * interrupt might come in and do read_lock(&tasklist_lock). | |
76 | * | |
77 | * If we don't disable interrupts there is a nasty deadlock between | |
78 | * detach_pid()->free_pid() and another cpu that does | |
79 | * spin_lock(&pidmap_lock) followed by an interrupt routine that does | |
80 | * read_lock(&tasklist_lock); | |
81 | * | |
82 | * After we clean up the tasklist_lock and know there are no | |
83 | * irq handlers that take it we can leave the interrupts enabled. | |
84 | * For now it is easier to be safe than to prove it can't happen. | |
85 | */ | |
3fbc9648 | 86 | |
1da177e4 LT |
87 | static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock); |
88 | ||
7ad5b3a5 | 89 | void put_pid(struct pid *pid) |
92476d7f | 90 | { |
baf8f0f8 PE |
91 | struct pid_namespace *ns; |
92 | ||
92476d7f EB |
93 | if (!pid) |
94 | return; | |
baf8f0f8 | 95 | |
8ef047aa | 96 | ns = pid->numbers[pid->level].ns; |
92476d7f | 97 | if ((atomic_read(&pid->count) == 1) || |
8ef047aa | 98 | atomic_dec_and_test(&pid->count)) { |
baf8f0f8 | 99 | kmem_cache_free(ns->pid_cachep, pid); |
b461cc03 | 100 | put_pid_ns(ns); |
8ef047aa | 101 | } |
92476d7f | 102 | } |
bbf73147 | 103 | EXPORT_SYMBOL_GPL(put_pid); |
92476d7f EB |
104 | |
105 | static void delayed_put_pid(struct rcu_head *rhp) | |
106 | { | |
107 | struct pid *pid = container_of(rhp, struct pid, rcu); | |
108 | put_pid(pid); | |
109 | } | |
110 | ||
7ad5b3a5 | 111 | void free_pid(struct pid *pid) |
92476d7f EB |
112 | { |
113 | /* We can be called with write_lock_irq(&tasklist_lock) held */ | |
8ef047aa | 114 | int i; |
92476d7f EB |
115 | unsigned long flags; |
116 | ||
117 | spin_lock_irqsave(&pidmap_lock, flags); | |
0a01f2cc EB |
118 | for (i = 0; i <= pid->level; i++) { |
119 | struct upid *upid = pid->numbers + i; | |
af4b8a83 | 120 | struct pid_namespace *ns = upid->ns; |
e8cfbc24 | 121 | switch (--ns->pid_allocated) { |
a6064885 | 122 | case 2: |
af4b8a83 EB |
123 | case 1: |
124 | /* When all that is left in the pid namespace | |
125 | * is the reaper wake up the reaper. The reaper | |
126 | * may be sleeping in zap_pid_ns_processes(). | |
127 | */ | |
128 | wake_up_process(ns->child_reaper); | |
129 | break; | |
e8cfbc24 | 130 | case PIDNS_ADDING: |
314a8ad0 ON |
131 | /* Handle a fork failure of the first process */ |
132 | WARN_ON(ns->child_reaper); | |
e8cfbc24 | 133 | ns->pid_allocated = 0; |
314a8ad0 | 134 | /* fall through */ |
af4b8a83 | 135 | case 0: |
af4b8a83 EB |
136 | schedule_work(&ns->proc_work); |
137 | break; | |
5e1182de | 138 | } |
95846ecf GS |
139 | |
140 | idr_remove(&ns->idr, upid->nr); | |
0a01f2cc | 141 | } |
92476d7f EB |
142 | spin_unlock_irqrestore(&pidmap_lock, flags); |
143 | ||
92476d7f EB |
144 | call_rcu(&pid->rcu, delayed_put_pid); |
145 | } | |
146 | ||
8ef047aa | 147 | struct pid *alloc_pid(struct pid_namespace *ns) |
92476d7f EB |
148 | { |
149 | struct pid *pid; | |
150 | enum pid_type type; | |
8ef047aa PE |
151 | int i, nr; |
152 | struct pid_namespace *tmp; | |
198fe21b | 153 | struct upid *upid; |
35f71bc0 | 154 | int retval = -ENOMEM; |
92476d7f | 155 | |
baf8f0f8 | 156 | pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL); |
92476d7f | 157 | if (!pid) |
35f71bc0 | 158 | return ERR_PTR(retval); |
92476d7f | 159 | |
8ef047aa | 160 | tmp = ns; |
0a01f2cc | 161 | pid->level = ns->level; |
95846ecf | 162 | |
8ef047aa | 163 | for (i = ns->level; i >= 0; i--) { |
95846ecf GS |
164 | int pid_min = 1; |
165 | ||
166 | idr_preload(GFP_KERNEL); | |
167 | spin_lock_irq(&pidmap_lock); | |
168 | ||
169 | /* | |
170 | * init really needs pid 1, but after reaching the maximum | |
171 | * wrap back to RESERVED_PIDS | |
172 | */ | |
173 | if (idr_get_cursor(&tmp->idr) > RESERVED_PIDS) | |
174 | pid_min = RESERVED_PIDS; | |
175 | ||
176 | /* | |
177 | * Store a null pointer so find_pid_ns does not find | |
178 | * a partially initialized PID (see below). | |
179 | */ | |
180 | nr = idr_alloc_cyclic(&tmp->idr, NULL, pid_min, | |
181 | pid_max, GFP_ATOMIC); | |
182 | spin_unlock_irq(&pidmap_lock); | |
183 | idr_preload_end(); | |
184 | ||
287980e4 | 185 | if (nr < 0) { |
35f71bc0 | 186 | retval = nr; |
8ef047aa | 187 | goto out_free; |
35f71bc0 | 188 | } |
92476d7f | 189 | |
8ef047aa PE |
190 | pid->numbers[i].nr = nr; |
191 | pid->numbers[i].ns = tmp; | |
192 | tmp = tmp->parent; | |
193 | } | |
194 | ||
0a01f2cc | 195 | if (unlikely(is_child_reaper(pid))) { |
c0ee5549 | 196 | if (pid_ns_prepare_proc(ns)) |
0a01f2cc EB |
197 | goto out_free; |
198 | } | |
199 | ||
b461cc03 | 200 | get_pid_ns(ns); |
92476d7f | 201 | atomic_set(&pid->count, 1); |
92476d7f EB |
202 | for (type = 0; type < PIDTYPE_MAX; ++type) |
203 | INIT_HLIST_HEAD(&pid->tasks[type]); | |
204 | ||
417e3152 | 205 | upid = pid->numbers + ns->level; |
92476d7f | 206 | spin_lock_irq(&pidmap_lock); |
e8cfbc24 | 207 | if (!(ns->pid_allocated & PIDNS_ADDING)) |
5e1182de | 208 | goto out_unlock; |
0a01f2cc | 209 | for ( ; upid >= pid->numbers; --upid) { |
95846ecf GS |
210 | /* Make the PID visible to find_pid_ns. */ |
211 | idr_replace(&upid->ns->idr, pid, upid->nr); | |
e8cfbc24 | 212 | upid->ns->pid_allocated++; |
0a01f2cc | 213 | } |
92476d7f EB |
214 | spin_unlock_irq(&pidmap_lock); |
215 | ||
92476d7f EB |
216 | return pid; |
217 | ||
5e1182de | 218 | out_unlock: |
6e666884 | 219 | spin_unlock_irq(&pidmap_lock); |
24c037eb ON |
220 | put_pid_ns(ns); |
221 | ||
92476d7f | 222 | out_free: |
95846ecf | 223 | spin_lock_irq(&pidmap_lock); |
b7127aa4 | 224 | while (++i <= ns->level) |
95846ecf GS |
225 | idr_remove(&ns->idr, (pid->numbers + i)->nr); |
226 | ||
c0ee5549 EB |
227 | /* On failure to allocate the first pid, reset the state */ |
228 | if (ns->pid_allocated == PIDNS_ADDING) | |
229 | idr_set_cursor(&ns->idr, 0); | |
230 | ||
95846ecf | 231 | spin_unlock_irq(&pidmap_lock); |
8ef047aa | 232 | |
baf8f0f8 | 233 | kmem_cache_free(ns->pid_cachep, pid); |
35f71bc0 | 234 | return ERR_PTR(retval); |
92476d7f EB |
235 | } |
236 | ||
c876ad76 EB |
237 | void disable_pid_allocation(struct pid_namespace *ns) |
238 | { | |
239 | spin_lock_irq(&pidmap_lock); | |
e8cfbc24 | 240 | ns->pid_allocated &= ~PIDNS_ADDING; |
c876ad76 EB |
241 | spin_unlock_irq(&pidmap_lock); |
242 | } | |
243 | ||
7ad5b3a5 | 244 | struct pid *find_pid_ns(int nr, struct pid_namespace *ns) |
1da177e4 | 245 | { |
e8cfbc24 | 246 | return idr_find(&ns->idr, nr); |
1da177e4 | 247 | } |
198fe21b | 248 | EXPORT_SYMBOL_GPL(find_pid_ns); |
1da177e4 | 249 | |
8990571e PE |
250 | struct pid *find_vpid(int nr) |
251 | { | |
17cf22c3 | 252 | return find_pid_ns(nr, task_active_pid_ns(current)); |
8990571e PE |
253 | } |
254 | EXPORT_SYMBOL_GPL(find_vpid); | |
255 | ||
e713d0da SB |
256 | /* |
257 | * attach_pid() must be called with the tasklist_lock write-held. | |
258 | */ | |
81907739 | 259 | void attach_pid(struct task_struct *task, enum pid_type type) |
1da177e4 | 260 | { |
81907739 ON |
261 | struct pid_link *link = &task->pids[type]; |
262 | hlist_add_head_rcu(&link->node, &link->pid->tasks[type]); | |
1da177e4 LT |
263 | } |
264 | ||
24336eae ON |
265 | static void __change_pid(struct task_struct *task, enum pid_type type, |
266 | struct pid *new) | |
1da177e4 | 267 | { |
92476d7f EB |
268 | struct pid_link *link; |
269 | struct pid *pid; | |
270 | int tmp; | |
1da177e4 | 271 | |
92476d7f EB |
272 | link = &task->pids[type]; |
273 | pid = link->pid; | |
1da177e4 | 274 | |
92476d7f | 275 | hlist_del_rcu(&link->node); |
24336eae | 276 | link->pid = new; |
1da177e4 | 277 | |
92476d7f EB |
278 | for (tmp = PIDTYPE_MAX; --tmp >= 0; ) |
279 | if (!hlist_empty(&pid->tasks[tmp])) | |
280 | return; | |
1da177e4 | 281 | |
92476d7f | 282 | free_pid(pid); |
1da177e4 LT |
283 | } |
284 | ||
24336eae ON |
285 | void detach_pid(struct task_struct *task, enum pid_type type) |
286 | { | |
287 | __change_pid(task, type, NULL); | |
288 | } | |
289 | ||
290 | void change_pid(struct task_struct *task, enum pid_type type, | |
291 | struct pid *pid) | |
292 | { | |
293 | __change_pid(task, type, pid); | |
81907739 | 294 | attach_pid(task, type); |
24336eae ON |
295 | } |
296 | ||
c18258c6 | 297 | /* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */ |
7ad5b3a5 | 298 | void transfer_pid(struct task_struct *old, struct task_struct *new, |
c18258c6 EB |
299 | enum pid_type type) |
300 | { | |
301 | new->pids[type].pid = old->pids[type].pid; | |
302 | hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node); | |
c18258c6 EB |
303 | } |
304 | ||
7ad5b3a5 | 305 | struct task_struct *pid_task(struct pid *pid, enum pid_type type) |
1da177e4 | 306 | { |
92476d7f EB |
307 | struct task_struct *result = NULL; |
308 | if (pid) { | |
309 | struct hlist_node *first; | |
67bdbffd | 310 | first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]), |
db1466b3 | 311 | lockdep_tasklist_lock_is_held()); |
92476d7f EB |
312 | if (first) |
313 | result = hlist_entry(first, struct task_struct, pids[(type)].node); | |
314 | } | |
315 | return result; | |
316 | } | |
eccba068 | 317 | EXPORT_SYMBOL(pid_task); |
1da177e4 | 318 | |
92476d7f | 319 | /* |
9728e5d6 | 320 | * Must be called under rcu_read_lock(). |
92476d7f | 321 | */ |
17f98dcf | 322 | struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns) |
92476d7f | 323 | { |
f78f5b90 PM |
324 | RCU_LOCKDEP_WARN(!rcu_read_lock_held(), |
325 | "find_task_by_pid_ns() needs rcu_read_lock() protection"); | |
17f98dcf | 326 | return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID); |
92476d7f | 327 | } |
1da177e4 | 328 | |
228ebcbe PE |
329 | struct task_struct *find_task_by_vpid(pid_t vnr) |
330 | { | |
17cf22c3 | 331 | return find_task_by_pid_ns(vnr, task_active_pid_ns(current)); |
228ebcbe | 332 | } |
228ebcbe | 333 | |
1a657f78 ON |
334 | struct pid *get_task_pid(struct task_struct *task, enum pid_type type) |
335 | { | |
336 | struct pid *pid; | |
337 | rcu_read_lock(); | |
2ae448ef ON |
338 | if (type != PIDTYPE_PID) |
339 | task = task->group_leader; | |
81b1a832 | 340 | pid = get_pid(rcu_dereference(task->pids[type].pid)); |
1a657f78 ON |
341 | rcu_read_unlock(); |
342 | return pid; | |
343 | } | |
77c100c8 | 344 | EXPORT_SYMBOL_GPL(get_task_pid); |
1a657f78 | 345 | |
7ad5b3a5 | 346 | struct task_struct *get_pid_task(struct pid *pid, enum pid_type type) |
92476d7f EB |
347 | { |
348 | struct task_struct *result; | |
349 | rcu_read_lock(); | |
350 | result = pid_task(pid, type); | |
351 | if (result) | |
352 | get_task_struct(result); | |
353 | rcu_read_unlock(); | |
354 | return result; | |
1da177e4 | 355 | } |
77c100c8 | 356 | EXPORT_SYMBOL_GPL(get_pid_task); |
1da177e4 | 357 | |
92476d7f | 358 | struct pid *find_get_pid(pid_t nr) |
1da177e4 LT |
359 | { |
360 | struct pid *pid; | |
361 | ||
92476d7f | 362 | rcu_read_lock(); |
198fe21b | 363 | pid = get_pid(find_vpid(nr)); |
92476d7f | 364 | rcu_read_unlock(); |
1da177e4 | 365 | |
92476d7f | 366 | return pid; |
1da177e4 | 367 | } |
339caf2a | 368 | EXPORT_SYMBOL_GPL(find_get_pid); |
1da177e4 | 369 | |
7af57294 PE |
370 | pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns) |
371 | { | |
372 | struct upid *upid; | |
373 | pid_t nr = 0; | |
374 | ||
375 | if (pid && ns->level <= pid->level) { | |
376 | upid = &pid->numbers[ns->level]; | |
377 | if (upid->ns == ns) | |
378 | nr = upid->nr; | |
379 | } | |
380 | return nr; | |
381 | } | |
4f82f457 | 382 | EXPORT_SYMBOL_GPL(pid_nr_ns); |
7af57294 | 383 | |
44c4e1b2 EB |
384 | pid_t pid_vnr(struct pid *pid) |
385 | { | |
17cf22c3 | 386 | return pid_nr_ns(pid, task_active_pid_ns(current)); |
44c4e1b2 EB |
387 | } |
388 | EXPORT_SYMBOL_GPL(pid_vnr); | |
389 | ||
52ee2dfd ON |
390 | pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, |
391 | struct pid_namespace *ns) | |
2f2a3a46 | 392 | { |
52ee2dfd ON |
393 | pid_t nr = 0; |
394 | ||
395 | rcu_read_lock(); | |
396 | if (!ns) | |
17cf22c3 | 397 | ns = task_active_pid_ns(current); |
52ee2dfd | 398 | if (likely(pid_alive(task))) { |
dd1c1f2f ON |
399 | if (type != PIDTYPE_PID) { |
400 | if (type == __PIDTYPE_TGID) | |
401 | type = PIDTYPE_PID; | |
e8cfbc24 | 402 | |
52ee2dfd | 403 | task = task->group_leader; |
dd1c1f2f | 404 | } |
81b1a832 | 405 | nr = pid_nr_ns(rcu_dereference(task->pids[type].pid), ns); |
52ee2dfd ON |
406 | } |
407 | rcu_read_unlock(); | |
408 | ||
409 | return nr; | |
2f2a3a46 | 410 | } |
52ee2dfd | 411 | EXPORT_SYMBOL(__task_pid_nr_ns); |
2f2a3a46 | 412 | |
61bce0f1 EB |
413 | struct pid_namespace *task_active_pid_ns(struct task_struct *tsk) |
414 | { | |
415 | return ns_of_pid(task_pid(tsk)); | |
416 | } | |
417 | EXPORT_SYMBOL_GPL(task_active_pid_ns); | |
418 | ||
0804ef4b | 419 | /* |
025dfdaf | 420 | * Used by proc to find the first pid that is greater than or equal to nr. |
0804ef4b | 421 | * |
e49859e7 | 422 | * If there is a pid at nr this function is exactly the same as find_pid_ns. |
0804ef4b | 423 | */ |
198fe21b | 424 | struct pid *find_ge_pid(int nr, struct pid_namespace *ns) |
0804ef4b | 425 | { |
95846ecf | 426 | return idr_get_next(&ns->idr, &nr); |
0804ef4b EB |
427 | } |
428 | ||
95846ecf | 429 | void __init pid_idr_init(void) |
1da177e4 | 430 | { |
840d6fe7 | 431 | /* Verify no one has done anything silly: */ |
e8cfbc24 | 432 | BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING); |
c876ad76 | 433 | |
72680a19 HB |
434 | /* bump default and minimum pid_max based on number of cpus */ |
435 | pid_max = min(pid_max_max, max_t(int, pid_max, | |
436 | PIDS_PER_CPU_DEFAULT * num_possible_cpus())); | |
437 | pid_max_min = max_t(int, pid_max_min, | |
438 | PIDS_PER_CPU_MIN * num_possible_cpus()); | |
439 | pr_info("pid_max: default: %u minimum: %u\n", pid_max, pid_max_min); | |
440 | ||
95846ecf | 441 | idr_init(&init_pid_ns.idr); |
92476d7f | 442 | |
74bd59bb | 443 | init_pid_ns.pid_cachep = KMEM_CACHE(pid, |
5d097056 | 444 | SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT); |
1da177e4 | 445 | } |