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Commit | Line | Data |
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86039bd3 AA |
1 | /* |
2 | * fs/userfaultfd.c | |
3 | * | |
4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
5 | * Copyright (C) 2008-2009 Red Hat, Inc. | |
6 | * Copyright (C) 2015 Red Hat, Inc. | |
7 | * | |
8 | * This work is licensed under the terms of the GNU GPL, version 2. See | |
9 | * the COPYING file in the top-level directory. | |
10 | * | |
11 | * Some part derived from fs/eventfd.c (anon inode setup) and | |
12 | * mm/ksm.c (mm hashing). | |
13 | */ | |
14 | ||
9cd75c3c | 15 | #include <linux/list.h> |
86039bd3 AA |
16 | #include <linux/hashtable.h> |
17 | #include <linux/sched.h> | |
18 | #include <linux/mm.h> | |
19 | #include <linux/poll.h> | |
20 | #include <linux/slab.h> | |
21 | #include <linux/seq_file.h> | |
22 | #include <linux/file.h> | |
23 | #include <linux/bug.h> | |
24 | #include <linux/anon_inodes.h> | |
25 | #include <linux/syscalls.h> | |
26 | #include <linux/userfaultfd_k.h> | |
27 | #include <linux/mempolicy.h> | |
28 | #include <linux/ioctl.h> | |
29 | #include <linux/security.h> | |
30 | ||
3004ec9c AA |
31 | static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly; |
32 | ||
86039bd3 AA |
33 | enum userfaultfd_state { |
34 | UFFD_STATE_WAIT_API, | |
35 | UFFD_STATE_RUNNING, | |
36 | }; | |
37 | ||
3004ec9c AA |
38 | /* |
39 | * Start with fault_pending_wqh and fault_wqh so they're more likely | |
40 | * to be in the same cacheline. | |
41 | */ | |
86039bd3 | 42 | struct userfaultfd_ctx { |
15b726ef AA |
43 | /* waitqueue head for the pending (i.e. not read) userfaults */ |
44 | wait_queue_head_t fault_pending_wqh; | |
45 | /* waitqueue head for the userfaults */ | |
86039bd3 AA |
46 | wait_queue_head_t fault_wqh; |
47 | /* waitqueue head for the pseudo fd to wakeup poll/read */ | |
48 | wait_queue_head_t fd_wqh; | |
9cd75c3c PE |
49 | /* waitqueue head for events */ |
50 | wait_queue_head_t event_wqh; | |
2c5b7e1b AA |
51 | /* a refile sequence protected by fault_pending_wqh lock */ |
52 | struct seqcount refile_seq; | |
3004ec9c AA |
53 | /* pseudo fd refcounting */ |
54 | atomic_t refcount; | |
86039bd3 AA |
55 | /* userfaultfd syscall flags */ |
56 | unsigned int flags; | |
9cd75c3c PE |
57 | /* features requested from the userspace */ |
58 | unsigned int features; | |
86039bd3 AA |
59 | /* state machine */ |
60 | enum userfaultfd_state state; | |
61 | /* released */ | |
62 | bool released; | |
63 | /* mm with one ore more vmas attached to this userfaultfd_ctx */ | |
64 | struct mm_struct *mm; | |
65 | }; | |
66 | ||
893e26e6 PE |
67 | struct userfaultfd_fork_ctx { |
68 | struct userfaultfd_ctx *orig; | |
69 | struct userfaultfd_ctx *new; | |
70 | struct list_head list; | |
71 | }; | |
72 | ||
86039bd3 | 73 | struct userfaultfd_wait_queue { |
a9b85f94 | 74 | struct uffd_msg msg; |
86039bd3 | 75 | wait_queue_t wq; |
86039bd3 | 76 | struct userfaultfd_ctx *ctx; |
15a77c6f | 77 | bool waken; |
86039bd3 AA |
78 | }; |
79 | ||
80 | struct userfaultfd_wake_range { | |
81 | unsigned long start; | |
82 | unsigned long len; | |
83 | }; | |
84 | ||
85 | static int userfaultfd_wake_function(wait_queue_t *wq, unsigned mode, | |
86 | int wake_flags, void *key) | |
87 | { | |
88 | struct userfaultfd_wake_range *range = key; | |
89 | int ret; | |
90 | struct userfaultfd_wait_queue *uwq; | |
91 | unsigned long start, len; | |
92 | ||
93 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); | |
94 | ret = 0; | |
86039bd3 AA |
95 | /* len == 0 means wake all */ |
96 | start = range->start; | |
97 | len = range->len; | |
a9b85f94 AA |
98 | if (len && (start > uwq->msg.arg.pagefault.address || |
99 | start + len <= uwq->msg.arg.pagefault.address)) | |
86039bd3 | 100 | goto out; |
15a77c6f AA |
101 | WRITE_ONCE(uwq->waken, true); |
102 | /* | |
103 | * The implicit smp_mb__before_spinlock in try_to_wake_up() | |
104 | * renders uwq->waken visible to other CPUs before the task is | |
105 | * waken. | |
106 | */ | |
86039bd3 AA |
107 | ret = wake_up_state(wq->private, mode); |
108 | if (ret) | |
109 | /* | |
110 | * Wake only once, autoremove behavior. | |
111 | * | |
112 | * After the effect of list_del_init is visible to the | |
113 | * other CPUs, the waitqueue may disappear from under | |
114 | * us, see the !list_empty_careful() in | |
115 | * handle_userfault(). try_to_wake_up() has an | |
116 | * implicit smp_mb__before_spinlock, and the | |
117 | * wq->private is read before calling the extern | |
118 | * function "wake_up_state" (which in turns calls | |
119 | * try_to_wake_up). While the spin_lock;spin_unlock; | |
120 | * wouldn't be enough, the smp_mb__before_spinlock is | |
121 | * enough to avoid an explicit smp_mb() here. | |
122 | */ | |
123 | list_del_init(&wq->task_list); | |
124 | out: | |
125 | return ret; | |
126 | } | |
127 | ||
128 | /** | |
129 | * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd | |
130 | * context. | |
131 | * @ctx: [in] Pointer to the userfaultfd context. | |
132 | * | |
133 | * Returns: In case of success, returns not zero. | |
134 | */ | |
135 | static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx) | |
136 | { | |
137 | if (!atomic_inc_not_zero(&ctx->refcount)) | |
138 | BUG(); | |
139 | } | |
140 | ||
141 | /** | |
142 | * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd | |
143 | * context. | |
144 | * @ctx: [in] Pointer to userfaultfd context. | |
145 | * | |
146 | * The userfaultfd context reference must have been previously acquired either | |
147 | * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget(). | |
148 | */ | |
149 | static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx) | |
150 | { | |
151 | if (atomic_dec_and_test(&ctx->refcount)) { | |
152 | VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock)); | |
153 | VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh)); | |
154 | VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock)); | |
155 | VM_BUG_ON(waitqueue_active(&ctx->fault_wqh)); | |
9cd75c3c PE |
156 | VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock)); |
157 | VM_BUG_ON(waitqueue_active(&ctx->event_wqh)); | |
86039bd3 AA |
158 | VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock)); |
159 | VM_BUG_ON(waitqueue_active(&ctx->fd_wqh)); | |
d2005e3f | 160 | mmdrop(ctx->mm); |
3004ec9c | 161 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
86039bd3 AA |
162 | } |
163 | } | |
164 | ||
a9b85f94 | 165 | static inline void msg_init(struct uffd_msg *msg) |
86039bd3 | 166 | { |
a9b85f94 AA |
167 | BUILD_BUG_ON(sizeof(struct uffd_msg) != 32); |
168 | /* | |
169 | * Must use memset to zero out the paddings or kernel data is | |
170 | * leaked to userland. | |
171 | */ | |
172 | memset(msg, 0, sizeof(struct uffd_msg)); | |
173 | } | |
174 | ||
175 | static inline struct uffd_msg userfault_msg(unsigned long address, | |
176 | unsigned int flags, | |
177 | unsigned long reason) | |
178 | { | |
179 | struct uffd_msg msg; | |
180 | msg_init(&msg); | |
181 | msg.event = UFFD_EVENT_PAGEFAULT; | |
182 | msg.arg.pagefault.address = address; | |
86039bd3 AA |
183 | if (flags & FAULT_FLAG_WRITE) |
184 | /* | |
a4605a61 | 185 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
a9b85f94 AA |
186 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE |
187 | * was not set in a UFFD_EVENT_PAGEFAULT, it means it | |
188 | * was a read fault, otherwise if set it means it's | |
189 | * a write fault. | |
86039bd3 | 190 | */ |
a9b85f94 | 191 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE; |
86039bd3 AA |
192 | if (reason & VM_UFFD_WP) |
193 | /* | |
a9b85f94 AA |
194 | * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the |
195 | * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was | |
196 | * not set in a UFFD_EVENT_PAGEFAULT, it means it was | |
197 | * a missing fault, otherwise if set it means it's a | |
198 | * write protect fault. | |
86039bd3 | 199 | */ |
a9b85f94 AA |
200 | msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP; |
201 | return msg; | |
86039bd3 AA |
202 | } |
203 | ||
8d2afd96 AA |
204 | /* |
205 | * Verify the pagetables are still not ok after having reigstered into | |
206 | * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any | |
207 | * userfault that has already been resolved, if userfaultfd_read and | |
208 | * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different | |
209 | * threads. | |
210 | */ | |
211 | static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx, | |
212 | unsigned long address, | |
213 | unsigned long flags, | |
214 | unsigned long reason) | |
215 | { | |
216 | struct mm_struct *mm = ctx->mm; | |
217 | pgd_t *pgd; | |
218 | pud_t *pud; | |
219 | pmd_t *pmd, _pmd; | |
220 | pte_t *pte; | |
221 | bool ret = true; | |
222 | ||
223 | VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); | |
224 | ||
225 | pgd = pgd_offset(mm, address); | |
226 | if (!pgd_present(*pgd)) | |
227 | goto out; | |
228 | pud = pud_offset(pgd, address); | |
229 | if (!pud_present(*pud)) | |
230 | goto out; | |
231 | pmd = pmd_offset(pud, address); | |
232 | /* | |
233 | * READ_ONCE must function as a barrier with narrower scope | |
234 | * and it must be equivalent to: | |
235 | * _pmd = *pmd; barrier(); | |
236 | * | |
237 | * This is to deal with the instability (as in | |
238 | * pmd_trans_unstable) of the pmd. | |
239 | */ | |
240 | _pmd = READ_ONCE(*pmd); | |
241 | if (!pmd_present(_pmd)) | |
242 | goto out; | |
243 | ||
244 | ret = false; | |
245 | if (pmd_trans_huge(_pmd)) | |
246 | goto out; | |
247 | ||
248 | /* | |
249 | * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it | |
250 | * and use the standard pte_offset_map() instead of parsing _pmd. | |
251 | */ | |
252 | pte = pte_offset_map(pmd, address); | |
253 | /* | |
254 | * Lockless access: we're in a wait_event so it's ok if it | |
255 | * changes under us. | |
256 | */ | |
257 | if (pte_none(*pte)) | |
258 | ret = true; | |
259 | pte_unmap(pte); | |
260 | ||
261 | out: | |
262 | return ret; | |
263 | } | |
264 | ||
86039bd3 AA |
265 | /* |
266 | * The locking rules involved in returning VM_FAULT_RETRY depending on | |
267 | * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and | |
268 | * FAULT_FLAG_KILLABLE are not straightforward. The "Caution" | |
269 | * recommendation in __lock_page_or_retry is not an understatement. | |
270 | * | |
271 | * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released | |
272 | * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is | |
273 | * not set. | |
274 | * | |
275 | * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not | |
276 | * set, VM_FAULT_RETRY can still be returned if and only if there are | |
277 | * fatal_signal_pending()s, and the mmap_sem must be released before | |
278 | * returning it. | |
279 | */ | |
82b0f8c3 | 280 | int handle_userfault(struct vm_fault *vmf, unsigned long reason) |
86039bd3 | 281 | { |
82b0f8c3 | 282 | struct mm_struct *mm = vmf->vma->vm_mm; |
86039bd3 AA |
283 | struct userfaultfd_ctx *ctx; |
284 | struct userfaultfd_wait_queue uwq; | |
ba85c702 | 285 | int ret; |
dfa37dc3 | 286 | bool must_wait, return_to_userland; |
15a77c6f | 287 | long blocking_state; |
86039bd3 AA |
288 | |
289 | BUG_ON(!rwsem_is_locked(&mm->mmap_sem)); | |
290 | ||
ba85c702 | 291 | ret = VM_FAULT_SIGBUS; |
82b0f8c3 | 292 | ctx = vmf->vma->vm_userfaultfd_ctx.ctx; |
86039bd3 | 293 | if (!ctx) |
ba85c702 | 294 | goto out; |
86039bd3 AA |
295 | |
296 | BUG_ON(ctx->mm != mm); | |
297 | ||
298 | VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP)); | |
299 | VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP)); | |
300 | ||
301 | /* | |
302 | * If it's already released don't get it. This avoids to loop | |
303 | * in __get_user_pages if userfaultfd_release waits on the | |
304 | * caller of handle_userfault to release the mmap_sem. | |
305 | */ | |
306 | if (unlikely(ACCESS_ONCE(ctx->released))) | |
ba85c702 | 307 | goto out; |
86039bd3 | 308 | |
39680f50 LT |
309 | /* |
310 | * We don't do userfault handling for the final child pid update. | |
311 | */ | |
312 | if (current->flags & PF_EXITING) | |
313 | goto out; | |
314 | ||
86039bd3 AA |
315 | /* |
316 | * Check that we can return VM_FAULT_RETRY. | |
317 | * | |
318 | * NOTE: it should become possible to return VM_FAULT_RETRY | |
319 | * even if FAULT_FLAG_TRIED is set without leading to gup() | |
320 | * -EBUSY failures, if the userfaultfd is to be extended for | |
321 | * VM_UFFD_WP tracking and we intend to arm the userfault | |
322 | * without first stopping userland access to the memory. For | |
323 | * VM_UFFD_MISSING userfaults this is enough for now. | |
324 | */ | |
82b0f8c3 | 325 | if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) { |
86039bd3 AA |
326 | /* |
327 | * Validate the invariant that nowait must allow retry | |
328 | * to be sure not to return SIGBUS erroneously on | |
329 | * nowait invocations. | |
330 | */ | |
82b0f8c3 | 331 | BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT); |
86039bd3 AA |
332 | #ifdef CONFIG_DEBUG_VM |
333 | if (printk_ratelimit()) { | |
334 | printk(KERN_WARNING | |
82b0f8c3 JK |
335 | "FAULT_FLAG_ALLOW_RETRY missing %x\n", |
336 | vmf->flags); | |
86039bd3 AA |
337 | dump_stack(); |
338 | } | |
339 | #endif | |
ba85c702 | 340 | goto out; |
86039bd3 AA |
341 | } |
342 | ||
343 | /* | |
344 | * Handle nowait, not much to do other than tell it to retry | |
345 | * and wait. | |
346 | */ | |
ba85c702 | 347 | ret = VM_FAULT_RETRY; |
82b0f8c3 | 348 | if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT) |
ba85c702 | 349 | goto out; |
86039bd3 AA |
350 | |
351 | /* take the reference before dropping the mmap_sem */ | |
352 | userfaultfd_ctx_get(ctx); | |
353 | ||
86039bd3 AA |
354 | init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function); |
355 | uwq.wq.private = current; | |
82b0f8c3 | 356 | uwq.msg = userfault_msg(vmf->address, vmf->flags, reason); |
86039bd3 | 357 | uwq.ctx = ctx; |
15a77c6f | 358 | uwq.waken = false; |
86039bd3 | 359 | |
bae473a4 | 360 | return_to_userland = |
82b0f8c3 | 361 | (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) == |
dfa37dc3 | 362 | (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE); |
15a77c6f AA |
363 | blocking_state = return_to_userland ? TASK_INTERRUPTIBLE : |
364 | TASK_KILLABLE; | |
dfa37dc3 | 365 | |
15b726ef | 366 | spin_lock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
367 | /* |
368 | * After the __add_wait_queue the uwq is visible to userland | |
369 | * through poll/read(). | |
370 | */ | |
15b726ef AA |
371 | __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq); |
372 | /* | |
373 | * The smp_mb() after __set_current_state prevents the reads | |
374 | * following the spin_unlock to happen before the list_add in | |
375 | * __add_wait_queue. | |
376 | */ | |
15a77c6f | 377 | set_current_state(blocking_state); |
15b726ef | 378 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 379 | |
82b0f8c3 JK |
380 | must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags, |
381 | reason); | |
8d2afd96 AA |
382 | up_read(&mm->mmap_sem); |
383 | ||
384 | if (likely(must_wait && !ACCESS_ONCE(ctx->released) && | |
dfa37dc3 AA |
385 | (return_to_userland ? !signal_pending(current) : |
386 | !fatal_signal_pending(current)))) { | |
86039bd3 AA |
387 | wake_up_poll(&ctx->fd_wqh, POLLIN); |
388 | schedule(); | |
ba85c702 | 389 | ret |= VM_FAULT_MAJOR; |
15a77c6f AA |
390 | |
391 | /* | |
392 | * False wakeups can orginate even from rwsem before | |
393 | * up_read() however userfaults will wait either for a | |
394 | * targeted wakeup on the specific uwq waitqueue from | |
395 | * wake_userfault() or for signals or for uffd | |
396 | * release. | |
397 | */ | |
398 | while (!READ_ONCE(uwq.waken)) { | |
399 | /* | |
400 | * This needs the full smp_store_mb() | |
401 | * guarantee as the state write must be | |
402 | * visible to other CPUs before reading | |
403 | * uwq.waken from other CPUs. | |
404 | */ | |
405 | set_current_state(blocking_state); | |
406 | if (READ_ONCE(uwq.waken) || | |
407 | READ_ONCE(ctx->released) || | |
408 | (return_to_userland ? signal_pending(current) : | |
409 | fatal_signal_pending(current))) | |
410 | break; | |
411 | schedule(); | |
412 | } | |
ba85c702 | 413 | } |
86039bd3 | 414 | |
ba85c702 | 415 | __set_current_state(TASK_RUNNING); |
15b726ef | 416 | |
dfa37dc3 AA |
417 | if (return_to_userland) { |
418 | if (signal_pending(current) && | |
419 | !fatal_signal_pending(current)) { | |
420 | /* | |
421 | * If we got a SIGSTOP or SIGCONT and this is | |
422 | * a normal userland page fault, just let | |
423 | * userland return so the signal will be | |
424 | * handled and gdb debugging works. The page | |
425 | * fault code immediately after we return from | |
426 | * this function is going to release the | |
427 | * mmap_sem and it's not depending on it | |
428 | * (unlike gup would if we were not to return | |
429 | * VM_FAULT_RETRY). | |
430 | * | |
431 | * If a fatal signal is pending we still take | |
432 | * the streamlined VM_FAULT_RETRY failure path | |
433 | * and there's no need to retake the mmap_sem | |
434 | * in such case. | |
435 | */ | |
436 | down_read(&mm->mmap_sem); | |
437 | ret = 0; | |
438 | } | |
439 | } | |
440 | ||
15b726ef AA |
441 | /* |
442 | * Here we race with the list_del; list_add in | |
443 | * userfaultfd_ctx_read(), however because we don't ever run | |
444 | * list_del_init() to refile across the two lists, the prev | |
445 | * and next pointers will never point to self. list_add also | |
446 | * would never let any of the two pointers to point to | |
447 | * self. So list_empty_careful won't risk to see both pointers | |
448 | * pointing to self at any time during the list refile. The | |
449 | * only case where list_del_init() is called is the full | |
450 | * removal in the wake function and there we don't re-list_add | |
451 | * and it's fine not to block on the spinlock. The uwq on this | |
452 | * kernel stack can be released after the list_del_init. | |
453 | */ | |
ba85c702 | 454 | if (!list_empty_careful(&uwq.wq.task_list)) { |
15b726ef AA |
455 | spin_lock(&ctx->fault_pending_wqh.lock); |
456 | /* | |
457 | * No need of list_del_init(), the uwq on the stack | |
458 | * will be freed shortly anyway. | |
459 | */ | |
460 | list_del(&uwq.wq.task_list); | |
461 | spin_unlock(&ctx->fault_pending_wqh.lock); | |
86039bd3 | 462 | } |
86039bd3 AA |
463 | |
464 | /* | |
465 | * ctx may go away after this if the userfault pseudo fd is | |
466 | * already released. | |
467 | */ | |
468 | userfaultfd_ctx_put(ctx); | |
469 | ||
ba85c702 AA |
470 | out: |
471 | return ret; | |
86039bd3 AA |
472 | } |
473 | ||
893e26e6 PE |
474 | static int userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx, |
475 | struct userfaultfd_wait_queue *ewq) | |
9cd75c3c PE |
476 | { |
477 | int ret = 0; | |
478 | ||
479 | ewq->ctx = ctx; | |
480 | init_waitqueue_entry(&ewq->wq, current); | |
481 | ||
482 | spin_lock(&ctx->event_wqh.lock); | |
483 | /* | |
484 | * After the __add_wait_queue the uwq is visible to userland | |
485 | * through poll/read(). | |
486 | */ | |
487 | __add_wait_queue(&ctx->event_wqh, &ewq->wq); | |
488 | for (;;) { | |
489 | set_current_state(TASK_KILLABLE); | |
490 | if (ewq->msg.event == 0) | |
491 | break; | |
492 | if (ACCESS_ONCE(ctx->released) || | |
493 | fatal_signal_pending(current)) { | |
494 | ret = -1; | |
495 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); | |
496 | break; | |
497 | } | |
498 | ||
499 | spin_unlock(&ctx->event_wqh.lock); | |
500 | ||
501 | wake_up_poll(&ctx->fd_wqh, POLLIN); | |
502 | schedule(); | |
503 | ||
504 | spin_lock(&ctx->event_wqh.lock); | |
505 | } | |
506 | __set_current_state(TASK_RUNNING); | |
507 | spin_unlock(&ctx->event_wqh.lock); | |
508 | ||
509 | /* | |
510 | * ctx may go away after this if the userfault pseudo fd is | |
511 | * already released. | |
512 | */ | |
513 | ||
514 | userfaultfd_ctx_put(ctx); | |
515 | return ret; | |
516 | } | |
517 | ||
518 | static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx, | |
519 | struct userfaultfd_wait_queue *ewq) | |
520 | { | |
521 | ewq->msg.event = 0; | |
522 | wake_up_locked(&ctx->event_wqh); | |
523 | __remove_wait_queue(&ctx->event_wqh, &ewq->wq); | |
524 | } | |
525 | ||
893e26e6 PE |
526 | int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs) |
527 | { | |
528 | struct userfaultfd_ctx *ctx = NULL, *octx; | |
529 | struct userfaultfd_fork_ctx *fctx; | |
530 | ||
531 | octx = vma->vm_userfaultfd_ctx.ctx; | |
532 | if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) { | |
533 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
534 | vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING); | |
535 | return 0; | |
536 | } | |
537 | ||
538 | list_for_each_entry(fctx, fcs, list) | |
539 | if (fctx->orig == octx) { | |
540 | ctx = fctx->new; | |
541 | break; | |
542 | } | |
543 | ||
544 | if (!ctx) { | |
545 | fctx = kmalloc(sizeof(*fctx), GFP_KERNEL); | |
546 | if (!fctx) | |
547 | return -ENOMEM; | |
548 | ||
549 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); | |
550 | if (!ctx) { | |
551 | kfree(fctx); | |
552 | return -ENOMEM; | |
553 | } | |
554 | ||
555 | atomic_set(&ctx->refcount, 1); | |
556 | ctx->flags = octx->flags; | |
557 | ctx->state = UFFD_STATE_RUNNING; | |
558 | ctx->features = octx->features; | |
559 | ctx->released = false; | |
560 | ctx->mm = vma->vm_mm; | |
d3aadc8e | 561 | atomic_inc(&ctx->mm->mm_count); |
893e26e6 PE |
562 | |
563 | userfaultfd_ctx_get(octx); | |
564 | fctx->orig = octx; | |
565 | fctx->new = ctx; | |
566 | list_add_tail(&fctx->list, fcs); | |
567 | } | |
568 | ||
569 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
570 | return 0; | |
571 | } | |
572 | ||
573 | static int dup_fctx(struct userfaultfd_fork_ctx *fctx) | |
574 | { | |
575 | struct userfaultfd_ctx *ctx = fctx->orig; | |
576 | struct userfaultfd_wait_queue ewq; | |
577 | ||
578 | msg_init(&ewq.msg); | |
579 | ||
580 | ewq.msg.event = UFFD_EVENT_FORK; | |
581 | ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new; | |
582 | ||
583 | return userfaultfd_event_wait_completion(ctx, &ewq); | |
584 | } | |
585 | ||
586 | void dup_userfaultfd_complete(struct list_head *fcs) | |
587 | { | |
588 | int ret = 0; | |
589 | struct userfaultfd_fork_ctx *fctx, *n; | |
590 | ||
591 | list_for_each_entry_safe(fctx, n, fcs, list) { | |
592 | if (!ret) | |
593 | ret = dup_fctx(fctx); | |
594 | list_del(&fctx->list); | |
595 | kfree(fctx); | |
596 | } | |
597 | } | |
598 | ||
72f87654 PE |
599 | void mremap_userfaultfd_prep(struct vm_area_struct *vma, |
600 | struct vm_userfaultfd_ctx *vm_ctx) | |
601 | { | |
602 | struct userfaultfd_ctx *ctx; | |
603 | ||
604 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
605 | if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) { | |
606 | vm_ctx->ctx = ctx; | |
607 | userfaultfd_ctx_get(ctx); | |
608 | } | |
609 | } | |
610 | ||
90794bf1 | 611 | void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx, |
72f87654 PE |
612 | unsigned long from, unsigned long to, |
613 | unsigned long len) | |
614 | { | |
90794bf1 | 615 | struct userfaultfd_ctx *ctx = vm_ctx->ctx; |
72f87654 PE |
616 | struct userfaultfd_wait_queue ewq; |
617 | ||
618 | if (!ctx) | |
619 | return; | |
620 | ||
621 | if (to & ~PAGE_MASK) { | |
622 | userfaultfd_ctx_put(ctx); | |
623 | return; | |
624 | } | |
625 | ||
626 | msg_init(&ewq.msg); | |
627 | ||
628 | ewq.msg.event = UFFD_EVENT_REMAP; | |
629 | ewq.msg.arg.remap.from = from; | |
630 | ewq.msg.arg.remap.to = to; | |
631 | ewq.msg.arg.remap.len = len; | |
632 | ||
633 | userfaultfd_event_wait_completion(ctx, &ewq); | |
634 | } | |
635 | ||
05ce7724 PE |
636 | void madvise_userfault_dontneed(struct vm_area_struct *vma, |
637 | struct vm_area_struct **prev, | |
638 | unsigned long start, unsigned long end) | |
639 | { | |
640 | struct mm_struct *mm = vma->vm_mm; | |
641 | struct userfaultfd_ctx *ctx; | |
642 | struct userfaultfd_wait_queue ewq; | |
643 | ||
644 | ctx = vma->vm_userfaultfd_ctx.ctx; | |
645 | if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_MADVDONTNEED)) | |
646 | return; | |
647 | ||
648 | userfaultfd_ctx_get(ctx); | |
649 | up_read(&mm->mmap_sem); | |
650 | ||
651 | *prev = NULL; /* We wait for ACK w/o the mmap semaphore */ | |
652 | ||
653 | msg_init(&ewq.msg); | |
654 | ||
655 | ewq.msg.event = UFFD_EVENT_MADVDONTNEED; | |
656 | ewq.msg.arg.madv_dn.start = start; | |
657 | ewq.msg.arg.madv_dn.end = end; | |
658 | ||
659 | userfaultfd_event_wait_completion(ctx, &ewq); | |
660 | ||
661 | down_read(&mm->mmap_sem); | |
662 | } | |
663 | ||
86039bd3 AA |
664 | static int userfaultfd_release(struct inode *inode, struct file *file) |
665 | { | |
666 | struct userfaultfd_ctx *ctx = file->private_data; | |
667 | struct mm_struct *mm = ctx->mm; | |
668 | struct vm_area_struct *vma, *prev; | |
669 | /* len == 0 means wake all */ | |
670 | struct userfaultfd_wake_range range = { .len = 0, }; | |
671 | unsigned long new_flags; | |
672 | ||
673 | ACCESS_ONCE(ctx->released) = true; | |
674 | ||
d2005e3f ON |
675 | if (!mmget_not_zero(mm)) |
676 | goto wakeup; | |
677 | ||
86039bd3 AA |
678 | /* |
679 | * Flush page faults out of all CPUs. NOTE: all page faults | |
680 | * must be retried without returning VM_FAULT_SIGBUS if | |
681 | * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx | |
682 | * changes while handle_userfault released the mmap_sem. So | |
683 | * it's critical that released is set to true (above), before | |
684 | * taking the mmap_sem for writing. | |
685 | */ | |
686 | down_write(&mm->mmap_sem); | |
687 | prev = NULL; | |
688 | for (vma = mm->mmap; vma; vma = vma->vm_next) { | |
689 | cond_resched(); | |
690 | BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^ | |
691 | !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
692 | if (vma->vm_userfaultfd_ctx.ctx != ctx) { | |
693 | prev = vma; | |
694 | continue; | |
695 | } | |
696 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); | |
697 | prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end, | |
698 | new_flags, vma->anon_vma, | |
699 | vma->vm_file, vma->vm_pgoff, | |
700 | vma_policy(vma), | |
701 | NULL_VM_UFFD_CTX); | |
702 | if (prev) | |
703 | vma = prev; | |
704 | else | |
705 | prev = vma; | |
706 | vma->vm_flags = new_flags; | |
707 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
708 | } | |
709 | up_write(&mm->mmap_sem); | |
d2005e3f ON |
710 | mmput(mm); |
711 | wakeup: | |
86039bd3 | 712 | /* |
15b726ef | 713 | * After no new page faults can wait on this fault_*wqh, flush |
86039bd3 | 714 | * the last page faults that may have been already waiting on |
15b726ef | 715 | * the fault_*wqh. |
86039bd3 | 716 | */ |
15b726ef | 717 | spin_lock(&ctx->fault_pending_wqh.lock); |
ac5be6b4 AA |
718 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range); |
719 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, &range); | |
15b726ef | 720 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
721 | |
722 | wake_up_poll(&ctx->fd_wqh, POLLHUP); | |
723 | userfaultfd_ctx_put(ctx); | |
724 | return 0; | |
725 | } | |
726 | ||
15b726ef | 727 | /* fault_pending_wqh.lock must be hold by the caller */ |
6dcc27fd PE |
728 | static inline struct userfaultfd_wait_queue *find_userfault_in( |
729 | wait_queue_head_t *wqh) | |
86039bd3 AA |
730 | { |
731 | wait_queue_t *wq; | |
15b726ef | 732 | struct userfaultfd_wait_queue *uwq; |
86039bd3 | 733 | |
6dcc27fd | 734 | VM_BUG_ON(!spin_is_locked(&wqh->lock)); |
86039bd3 | 735 | |
15b726ef | 736 | uwq = NULL; |
6dcc27fd | 737 | if (!waitqueue_active(wqh)) |
15b726ef AA |
738 | goto out; |
739 | /* walk in reverse to provide FIFO behavior to read userfaults */ | |
6dcc27fd | 740 | wq = list_last_entry(&wqh->task_list, typeof(*wq), task_list); |
15b726ef AA |
741 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); |
742 | out: | |
743 | return uwq; | |
86039bd3 | 744 | } |
6dcc27fd PE |
745 | |
746 | static inline struct userfaultfd_wait_queue *find_userfault( | |
747 | struct userfaultfd_ctx *ctx) | |
748 | { | |
749 | return find_userfault_in(&ctx->fault_pending_wqh); | |
750 | } | |
86039bd3 | 751 | |
9cd75c3c PE |
752 | static inline struct userfaultfd_wait_queue *find_userfault_evt( |
753 | struct userfaultfd_ctx *ctx) | |
754 | { | |
755 | return find_userfault_in(&ctx->event_wqh); | |
756 | } | |
757 | ||
86039bd3 AA |
758 | static unsigned int userfaultfd_poll(struct file *file, poll_table *wait) |
759 | { | |
760 | struct userfaultfd_ctx *ctx = file->private_data; | |
761 | unsigned int ret; | |
762 | ||
763 | poll_wait(file, &ctx->fd_wqh, wait); | |
764 | ||
765 | switch (ctx->state) { | |
766 | case UFFD_STATE_WAIT_API: | |
767 | return POLLERR; | |
768 | case UFFD_STATE_RUNNING: | |
ba85c702 AA |
769 | /* |
770 | * poll() never guarantees that read won't block. | |
771 | * userfaults can be waken before they're read(). | |
772 | */ | |
773 | if (unlikely(!(file->f_flags & O_NONBLOCK))) | |
774 | return POLLERR; | |
15b726ef AA |
775 | /* |
776 | * lockless access to see if there are pending faults | |
777 | * __pollwait last action is the add_wait_queue but | |
778 | * the spin_unlock would allow the waitqueue_active to | |
779 | * pass above the actual list_add inside | |
780 | * add_wait_queue critical section. So use a full | |
781 | * memory barrier to serialize the list_add write of | |
782 | * add_wait_queue() with the waitqueue_active read | |
783 | * below. | |
784 | */ | |
785 | ret = 0; | |
786 | smp_mb(); | |
787 | if (waitqueue_active(&ctx->fault_pending_wqh)) | |
788 | ret = POLLIN; | |
9cd75c3c PE |
789 | else if (waitqueue_active(&ctx->event_wqh)) |
790 | ret = POLLIN; | |
791 | ||
86039bd3 AA |
792 | return ret; |
793 | default: | |
8474901a AA |
794 | WARN_ON_ONCE(1); |
795 | return POLLERR; | |
86039bd3 AA |
796 | } |
797 | } | |
798 | ||
893e26e6 PE |
799 | static const struct file_operations userfaultfd_fops; |
800 | ||
801 | static int resolve_userfault_fork(struct userfaultfd_ctx *ctx, | |
802 | struct userfaultfd_ctx *new, | |
803 | struct uffd_msg *msg) | |
804 | { | |
805 | int fd; | |
806 | struct file *file; | |
807 | unsigned int flags = new->flags & UFFD_SHARED_FCNTL_FLAGS; | |
808 | ||
809 | fd = get_unused_fd_flags(flags); | |
810 | if (fd < 0) | |
811 | return fd; | |
812 | ||
813 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, new, | |
814 | O_RDWR | flags); | |
815 | if (IS_ERR(file)) { | |
816 | put_unused_fd(fd); | |
817 | return PTR_ERR(file); | |
818 | } | |
819 | ||
820 | fd_install(fd, file); | |
821 | msg->arg.reserved.reserved1 = 0; | |
822 | msg->arg.fork.ufd = fd; | |
823 | ||
824 | return 0; | |
825 | } | |
826 | ||
86039bd3 | 827 | static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait, |
a9b85f94 | 828 | struct uffd_msg *msg) |
86039bd3 AA |
829 | { |
830 | ssize_t ret; | |
831 | DECLARE_WAITQUEUE(wait, current); | |
15b726ef | 832 | struct userfaultfd_wait_queue *uwq; |
893e26e6 PE |
833 | /* |
834 | * Handling fork event requires sleeping operations, so | |
835 | * we drop the event_wqh lock, then do these ops, then | |
836 | * lock it back and wake up the waiter. While the lock is | |
837 | * dropped the ewq may go away so we keep track of it | |
838 | * carefully. | |
839 | */ | |
840 | LIST_HEAD(fork_event); | |
841 | struct userfaultfd_ctx *fork_nctx = NULL; | |
86039bd3 | 842 | |
15b726ef | 843 | /* always take the fd_wqh lock before the fault_pending_wqh lock */ |
86039bd3 AA |
844 | spin_lock(&ctx->fd_wqh.lock); |
845 | __add_wait_queue(&ctx->fd_wqh, &wait); | |
846 | for (;;) { | |
847 | set_current_state(TASK_INTERRUPTIBLE); | |
15b726ef AA |
848 | spin_lock(&ctx->fault_pending_wqh.lock); |
849 | uwq = find_userfault(ctx); | |
850 | if (uwq) { | |
2c5b7e1b AA |
851 | /* |
852 | * Use a seqcount to repeat the lockless check | |
853 | * in wake_userfault() to avoid missing | |
854 | * wakeups because during the refile both | |
855 | * waitqueue could become empty if this is the | |
856 | * only userfault. | |
857 | */ | |
858 | write_seqcount_begin(&ctx->refile_seq); | |
859 | ||
86039bd3 | 860 | /* |
15b726ef AA |
861 | * The fault_pending_wqh.lock prevents the uwq |
862 | * to disappear from under us. | |
863 | * | |
864 | * Refile this userfault from | |
865 | * fault_pending_wqh to fault_wqh, it's not | |
866 | * pending anymore after we read it. | |
867 | * | |
868 | * Use list_del() by hand (as | |
869 | * userfaultfd_wake_function also uses | |
870 | * list_del_init() by hand) to be sure nobody | |
871 | * changes __remove_wait_queue() to use | |
872 | * list_del_init() in turn breaking the | |
873 | * !list_empty_careful() check in | |
874 | * handle_userfault(). The uwq->wq.task_list | |
875 | * must never be empty at any time during the | |
876 | * refile, or the waitqueue could disappear | |
877 | * from under us. The "wait_queue_head_t" | |
878 | * parameter of __remove_wait_queue() is unused | |
879 | * anyway. | |
86039bd3 | 880 | */ |
15b726ef AA |
881 | list_del(&uwq->wq.task_list); |
882 | __add_wait_queue(&ctx->fault_wqh, &uwq->wq); | |
883 | ||
2c5b7e1b AA |
884 | write_seqcount_end(&ctx->refile_seq); |
885 | ||
a9b85f94 AA |
886 | /* careful to always initialize msg if ret == 0 */ |
887 | *msg = uwq->msg; | |
15b726ef | 888 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
889 | ret = 0; |
890 | break; | |
891 | } | |
15b726ef | 892 | spin_unlock(&ctx->fault_pending_wqh.lock); |
9cd75c3c PE |
893 | |
894 | spin_lock(&ctx->event_wqh.lock); | |
895 | uwq = find_userfault_evt(ctx); | |
896 | if (uwq) { | |
897 | *msg = uwq->msg; | |
898 | ||
893e26e6 PE |
899 | if (uwq->msg.event == UFFD_EVENT_FORK) { |
900 | fork_nctx = (struct userfaultfd_ctx *) | |
901 | (unsigned long) | |
902 | uwq->msg.arg.reserved.reserved1; | |
903 | list_move(&uwq->wq.task_list, &fork_event); | |
904 | spin_unlock(&ctx->event_wqh.lock); | |
905 | ret = 0; | |
906 | break; | |
907 | } | |
908 | ||
9cd75c3c PE |
909 | userfaultfd_event_complete(ctx, uwq); |
910 | spin_unlock(&ctx->event_wqh.lock); | |
911 | ret = 0; | |
912 | break; | |
913 | } | |
914 | spin_unlock(&ctx->event_wqh.lock); | |
915 | ||
86039bd3 AA |
916 | if (signal_pending(current)) { |
917 | ret = -ERESTARTSYS; | |
918 | break; | |
919 | } | |
920 | if (no_wait) { | |
921 | ret = -EAGAIN; | |
922 | break; | |
923 | } | |
924 | spin_unlock(&ctx->fd_wqh.lock); | |
925 | schedule(); | |
926 | spin_lock(&ctx->fd_wqh.lock); | |
927 | } | |
928 | __remove_wait_queue(&ctx->fd_wqh, &wait); | |
929 | __set_current_state(TASK_RUNNING); | |
930 | spin_unlock(&ctx->fd_wqh.lock); | |
931 | ||
893e26e6 PE |
932 | if (!ret && msg->event == UFFD_EVENT_FORK) { |
933 | ret = resolve_userfault_fork(ctx, fork_nctx, msg); | |
934 | ||
935 | if (!ret) { | |
936 | spin_lock(&ctx->event_wqh.lock); | |
937 | if (!list_empty(&fork_event)) { | |
938 | uwq = list_first_entry(&fork_event, | |
939 | typeof(*uwq), | |
940 | wq.task_list); | |
941 | list_del(&uwq->wq.task_list); | |
942 | __add_wait_queue(&ctx->event_wqh, &uwq->wq); | |
943 | userfaultfd_event_complete(ctx, uwq); | |
944 | } | |
945 | spin_unlock(&ctx->event_wqh.lock); | |
946 | } | |
947 | } | |
948 | ||
86039bd3 AA |
949 | return ret; |
950 | } | |
951 | ||
952 | static ssize_t userfaultfd_read(struct file *file, char __user *buf, | |
953 | size_t count, loff_t *ppos) | |
954 | { | |
955 | struct userfaultfd_ctx *ctx = file->private_data; | |
956 | ssize_t _ret, ret = 0; | |
a9b85f94 | 957 | struct uffd_msg msg; |
86039bd3 AA |
958 | int no_wait = file->f_flags & O_NONBLOCK; |
959 | ||
960 | if (ctx->state == UFFD_STATE_WAIT_API) | |
961 | return -EINVAL; | |
86039bd3 AA |
962 | |
963 | for (;;) { | |
a9b85f94 | 964 | if (count < sizeof(msg)) |
86039bd3 | 965 | return ret ? ret : -EINVAL; |
a9b85f94 | 966 | _ret = userfaultfd_ctx_read(ctx, no_wait, &msg); |
86039bd3 AA |
967 | if (_ret < 0) |
968 | return ret ? ret : _ret; | |
a9b85f94 | 969 | if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg))) |
86039bd3 | 970 | return ret ? ret : -EFAULT; |
a9b85f94 AA |
971 | ret += sizeof(msg); |
972 | buf += sizeof(msg); | |
973 | count -= sizeof(msg); | |
86039bd3 AA |
974 | /* |
975 | * Allow to read more than one fault at time but only | |
976 | * block if waiting for the very first one. | |
977 | */ | |
978 | no_wait = O_NONBLOCK; | |
979 | } | |
980 | } | |
981 | ||
982 | static void __wake_userfault(struct userfaultfd_ctx *ctx, | |
983 | struct userfaultfd_wake_range *range) | |
984 | { | |
985 | unsigned long start, end; | |
986 | ||
987 | start = range->start; | |
988 | end = range->start + range->len; | |
989 | ||
15b726ef | 990 | spin_lock(&ctx->fault_pending_wqh.lock); |
86039bd3 | 991 | /* wake all in the range and autoremove */ |
15b726ef | 992 | if (waitqueue_active(&ctx->fault_pending_wqh)) |
ac5be6b4 | 993 | __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, |
15b726ef AA |
994 | range); |
995 | if (waitqueue_active(&ctx->fault_wqh)) | |
ac5be6b4 | 996 | __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, range); |
15b726ef | 997 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
998 | } |
999 | ||
1000 | static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx, | |
1001 | struct userfaultfd_wake_range *range) | |
1002 | { | |
2c5b7e1b AA |
1003 | unsigned seq; |
1004 | bool need_wakeup; | |
1005 | ||
86039bd3 AA |
1006 | /* |
1007 | * To be sure waitqueue_active() is not reordered by the CPU | |
1008 | * before the pagetable update, use an explicit SMP memory | |
1009 | * barrier here. PT lock release or up_read(mmap_sem) still | |
1010 | * have release semantics that can allow the | |
1011 | * waitqueue_active() to be reordered before the pte update. | |
1012 | */ | |
1013 | smp_mb(); | |
1014 | ||
1015 | /* | |
1016 | * Use waitqueue_active because it's very frequent to | |
1017 | * change the address space atomically even if there are no | |
1018 | * userfaults yet. So we take the spinlock only when we're | |
1019 | * sure we've userfaults to wake. | |
1020 | */ | |
2c5b7e1b AA |
1021 | do { |
1022 | seq = read_seqcount_begin(&ctx->refile_seq); | |
1023 | need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) || | |
1024 | waitqueue_active(&ctx->fault_wqh); | |
1025 | cond_resched(); | |
1026 | } while (read_seqcount_retry(&ctx->refile_seq, seq)); | |
1027 | if (need_wakeup) | |
86039bd3 AA |
1028 | __wake_userfault(ctx, range); |
1029 | } | |
1030 | ||
1031 | static __always_inline int validate_range(struct mm_struct *mm, | |
1032 | __u64 start, __u64 len) | |
1033 | { | |
1034 | __u64 task_size = mm->task_size; | |
1035 | ||
1036 | if (start & ~PAGE_MASK) | |
1037 | return -EINVAL; | |
1038 | if (len & ~PAGE_MASK) | |
1039 | return -EINVAL; | |
1040 | if (!len) | |
1041 | return -EINVAL; | |
1042 | if (start < mmap_min_addr) | |
1043 | return -EINVAL; | |
1044 | if (start >= task_size) | |
1045 | return -EINVAL; | |
1046 | if (len > task_size - start) | |
1047 | return -EINVAL; | |
1048 | return 0; | |
1049 | } | |
1050 | ||
1051 | static int userfaultfd_register(struct userfaultfd_ctx *ctx, | |
1052 | unsigned long arg) | |
1053 | { | |
1054 | struct mm_struct *mm = ctx->mm; | |
1055 | struct vm_area_struct *vma, *prev, *cur; | |
1056 | int ret; | |
1057 | struct uffdio_register uffdio_register; | |
1058 | struct uffdio_register __user *user_uffdio_register; | |
1059 | unsigned long vm_flags, new_flags; | |
1060 | bool found; | |
1061 | unsigned long start, end, vma_end; | |
1062 | ||
1063 | user_uffdio_register = (struct uffdio_register __user *) arg; | |
1064 | ||
1065 | ret = -EFAULT; | |
1066 | if (copy_from_user(&uffdio_register, user_uffdio_register, | |
1067 | sizeof(uffdio_register)-sizeof(__u64))) | |
1068 | goto out; | |
1069 | ||
1070 | ret = -EINVAL; | |
1071 | if (!uffdio_register.mode) | |
1072 | goto out; | |
1073 | if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING| | |
1074 | UFFDIO_REGISTER_MODE_WP)) | |
1075 | goto out; | |
1076 | vm_flags = 0; | |
1077 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING) | |
1078 | vm_flags |= VM_UFFD_MISSING; | |
1079 | if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) { | |
1080 | vm_flags |= VM_UFFD_WP; | |
1081 | /* | |
1082 | * FIXME: remove the below error constraint by | |
1083 | * implementing the wprotect tracking mode. | |
1084 | */ | |
1085 | ret = -EINVAL; | |
1086 | goto out; | |
1087 | } | |
1088 | ||
1089 | ret = validate_range(mm, uffdio_register.range.start, | |
1090 | uffdio_register.range.len); | |
1091 | if (ret) | |
1092 | goto out; | |
1093 | ||
1094 | start = uffdio_register.range.start; | |
1095 | end = start + uffdio_register.range.len; | |
1096 | ||
d2005e3f ON |
1097 | ret = -ENOMEM; |
1098 | if (!mmget_not_zero(mm)) | |
1099 | goto out; | |
1100 | ||
86039bd3 AA |
1101 | down_write(&mm->mmap_sem); |
1102 | vma = find_vma_prev(mm, start, &prev); | |
86039bd3 AA |
1103 | if (!vma) |
1104 | goto out_unlock; | |
1105 | ||
1106 | /* check that there's at least one vma in the range */ | |
1107 | ret = -EINVAL; | |
1108 | if (vma->vm_start >= end) | |
1109 | goto out_unlock; | |
1110 | ||
1111 | /* | |
1112 | * Search for not compatible vmas. | |
1113 | * | |
1114 | * FIXME: this shall be relaxed later so that it doesn't fail | |
1115 | * on tmpfs backed vmas (in addition to the current allowance | |
1116 | * on anonymous vmas). | |
1117 | */ | |
1118 | found = false; | |
1119 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { | |
1120 | cond_resched(); | |
1121 | ||
1122 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
1123 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
1124 | ||
1125 | /* check not compatible vmas */ | |
1126 | ret = -EINVAL; | |
a94720bf | 1127 | if (!vma_is_anonymous(cur)) |
86039bd3 AA |
1128 | goto out_unlock; |
1129 | ||
1130 | /* | |
1131 | * Check that this vma isn't already owned by a | |
1132 | * different userfaultfd. We can't allow more than one | |
1133 | * userfaultfd to own a single vma simultaneously or we | |
1134 | * wouldn't know which one to deliver the userfaults to. | |
1135 | */ | |
1136 | ret = -EBUSY; | |
1137 | if (cur->vm_userfaultfd_ctx.ctx && | |
1138 | cur->vm_userfaultfd_ctx.ctx != ctx) | |
1139 | goto out_unlock; | |
1140 | ||
1141 | found = true; | |
1142 | } | |
1143 | BUG_ON(!found); | |
1144 | ||
1145 | if (vma->vm_start < start) | |
1146 | prev = vma; | |
1147 | ||
1148 | ret = 0; | |
1149 | do { | |
1150 | cond_resched(); | |
1151 | ||
a94720bf | 1152 | BUG_ON(!vma_is_anonymous(vma)); |
86039bd3 AA |
1153 | BUG_ON(vma->vm_userfaultfd_ctx.ctx && |
1154 | vma->vm_userfaultfd_ctx.ctx != ctx); | |
1155 | ||
1156 | /* | |
1157 | * Nothing to do: this vma is already registered into this | |
1158 | * userfaultfd and with the right tracking mode too. | |
1159 | */ | |
1160 | if (vma->vm_userfaultfd_ctx.ctx == ctx && | |
1161 | (vma->vm_flags & vm_flags) == vm_flags) | |
1162 | goto skip; | |
1163 | ||
1164 | if (vma->vm_start > start) | |
1165 | start = vma->vm_start; | |
1166 | vma_end = min(end, vma->vm_end); | |
1167 | ||
1168 | new_flags = (vma->vm_flags & ~vm_flags) | vm_flags; | |
1169 | prev = vma_merge(mm, prev, start, vma_end, new_flags, | |
1170 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1171 | vma_policy(vma), | |
1172 | ((struct vm_userfaultfd_ctx){ ctx })); | |
1173 | if (prev) { | |
1174 | vma = prev; | |
1175 | goto next; | |
1176 | } | |
1177 | if (vma->vm_start < start) { | |
1178 | ret = split_vma(mm, vma, start, 1); | |
1179 | if (ret) | |
1180 | break; | |
1181 | } | |
1182 | if (vma->vm_end > end) { | |
1183 | ret = split_vma(mm, vma, end, 0); | |
1184 | if (ret) | |
1185 | break; | |
1186 | } | |
1187 | next: | |
1188 | /* | |
1189 | * In the vma_merge() successful mprotect-like case 8: | |
1190 | * the next vma was merged into the current one and | |
1191 | * the current one has not been updated yet. | |
1192 | */ | |
1193 | vma->vm_flags = new_flags; | |
1194 | vma->vm_userfaultfd_ctx.ctx = ctx; | |
1195 | ||
1196 | skip: | |
1197 | prev = vma; | |
1198 | start = vma->vm_end; | |
1199 | vma = vma->vm_next; | |
1200 | } while (vma && vma->vm_start < end); | |
1201 | out_unlock: | |
1202 | up_write(&mm->mmap_sem); | |
d2005e3f | 1203 | mmput(mm); |
86039bd3 AA |
1204 | if (!ret) { |
1205 | /* | |
1206 | * Now that we scanned all vmas we can already tell | |
1207 | * userland which ioctls methods are guaranteed to | |
1208 | * succeed on this range. | |
1209 | */ | |
1210 | if (put_user(UFFD_API_RANGE_IOCTLS, | |
1211 | &user_uffdio_register->ioctls)) | |
1212 | ret = -EFAULT; | |
1213 | } | |
1214 | out: | |
1215 | return ret; | |
1216 | } | |
1217 | ||
1218 | static int userfaultfd_unregister(struct userfaultfd_ctx *ctx, | |
1219 | unsigned long arg) | |
1220 | { | |
1221 | struct mm_struct *mm = ctx->mm; | |
1222 | struct vm_area_struct *vma, *prev, *cur; | |
1223 | int ret; | |
1224 | struct uffdio_range uffdio_unregister; | |
1225 | unsigned long new_flags; | |
1226 | bool found; | |
1227 | unsigned long start, end, vma_end; | |
1228 | const void __user *buf = (void __user *)arg; | |
1229 | ||
1230 | ret = -EFAULT; | |
1231 | if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister))) | |
1232 | goto out; | |
1233 | ||
1234 | ret = validate_range(mm, uffdio_unregister.start, | |
1235 | uffdio_unregister.len); | |
1236 | if (ret) | |
1237 | goto out; | |
1238 | ||
1239 | start = uffdio_unregister.start; | |
1240 | end = start + uffdio_unregister.len; | |
1241 | ||
d2005e3f ON |
1242 | ret = -ENOMEM; |
1243 | if (!mmget_not_zero(mm)) | |
1244 | goto out; | |
1245 | ||
86039bd3 AA |
1246 | down_write(&mm->mmap_sem); |
1247 | vma = find_vma_prev(mm, start, &prev); | |
86039bd3 AA |
1248 | if (!vma) |
1249 | goto out_unlock; | |
1250 | ||
1251 | /* check that there's at least one vma in the range */ | |
1252 | ret = -EINVAL; | |
1253 | if (vma->vm_start >= end) | |
1254 | goto out_unlock; | |
1255 | ||
1256 | /* | |
1257 | * Search for not compatible vmas. | |
1258 | * | |
1259 | * FIXME: this shall be relaxed later so that it doesn't fail | |
1260 | * on tmpfs backed vmas (in addition to the current allowance | |
1261 | * on anonymous vmas). | |
1262 | */ | |
1263 | found = false; | |
1264 | ret = -EINVAL; | |
1265 | for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) { | |
1266 | cond_resched(); | |
1267 | ||
1268 | BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^ | |
1269 | !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP))); | |
1270 | ||
1271 | /* | |
1272 | * Check not compatible vmas, not strictly required | |
1273 | * here as not compatible vmas cannot have an | |
1274 | * userfaultfd_ctx registered on them, but this | |
1275 | * provides for more strict behavior to notice | |
1276 | * unregistration errors. | |
1277 | */ | |
a94720bf | 1278 | if (!vma_is_anonymous(cur)) |
86039bd3 AA |
1279 | goto out_unlock; |
1280 | ||
1281 | found = true; | |
1282 | } | |
1283 | BUG_ON(!found); | |
1284 | ||
1285 | if (vma->vm_start < start) | |
1286 | prev = vma; | |
1287 | ||
1288 | ret = 0; | |
1289 | do { | |
1290 | cond_resched(); | |
1291 | ||
a94720bf | 1292 | BUG_ON(!vma_is_anonymous(vma)); |
86039bd3 AA |
1293 | |
1294 | /* | |
1295 | * Nothing to do: this vma is already registered into this | |
1296 | * userfaultfd and with the right tracking mode too. | |
1297 | */ | |
1298 | if (!vma->vm_userfaultfd_ctx.ctx) | |
1299 | goto skip; | |
1300 | ||
1301 | if (vma->vm_start > start) | |
1302 | start = vma->vm_start; | |
1303 | vma_end = min(end, vma->vm_end); | |
1304 | ||
1305 | new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP); | |
1306 | prev = vma_merge(mm, prev, start, vma_end, new_flags, | |
1307 | vma->anon_vma, vma->vm_file, vma->vm_pgoff, | |
1308 | vma_policy(vma), | |
1309 | NULL_VM_UFFD_CTX); | |
1310 | if (prev) { | |
1311 | vma = prev; | |
1312 | goto next; | |
1313 | } | |
1314 | if (vma->vm_start < start) { | |
1315 | ret = split_vma(mm, vma, start, 1); | |
1316 | if (ret) | |
1317 | break; | |
1318 | } | |
1319 | if (vma->vm_end > end) { | |
1320 | ret = split_vma(mm, vma, end, 0); | |
1321 | if (ret) | |
1322 | break; | |
1323 | } | |
1324 | next: | |
1325 | /* | |
1326 | * In the vma_merge() successful mprotect-like case 8: | |
1327 | * the next vma was merged into the current one and | |
1328 | * the current one has not been updated yet. | |
1329 | */ | |
1330 | vma->vm_flags = new_flags; | |
1331 | vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX; | |
1332 | ||
1333 | skip: | |
1334 | prev = vma; | |
1335 | start = vma->vm_end; | |
1336 | vma = vma->vm_next; | |
1337 | } while (vma && vma->vm_start < end); | |
1338 | out_unlock: | |
1339 | up_write(&mm->mmap_sem); | |
d2005e3f | 1340 | mmput(mm); |
86039bd3 AA |
1341 | out: |
1342 | return ret; | |
1343 | } | |
1344 | ||
1345 | /* | |
ba85c702 AA |
1346 | * userfaultfd_wake may be used in combination with the |
1347 | * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches. | |
86039bd3 AA |
1348 | */ |
1349 | static int userfaultfd_wake(struct userfaultfd_ctx *ctx, | |
1350 | unsigned long arg) | |
1351 | { | |
1352 | int ret; | |
1353 | struct uffdio_range uffdio_wake; | |
1354 | struct userfaultfd_wake_range range; | |
1355 | const void __user *buf = (void __user *)arg; | |
1356 | ||
1357 | ret = -EFAULT; | |
1358 | if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake))) | |
1359 | goto out; | |
1360 | ||
1361 | ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len); | |
1362 | if (ret) | |
1363 | goto out; | |
1364 | ||
1365 | range.start = uffdio_wake.start; | |
1366 | range.len = uffdio_wake.len; | |
1367 | ||
1368 | /* | |
1369 | * len == 0 means wake all and we don't want to wake all here, | |
1370 | * so check it again to be sure. | |
1371 | */ | |
1372 | VM_BUG_ON(!range.len); | |
1373 | ||
1374 | wake_userfault(ctx, &range); | |
1375 | ret = 0; | |
1376 | ||
1377 | out: | |
1378 | return ret; | |
1379 | } | |
1380 | ||
ad465cae AA |
1381 | static int userfaultfd_copy(struct userfaultfd_ctx *ctx, |
1382 | unsigned long arg) | |
1383 | { | |
1384 | __s64 ret; | |
1385 | struct uffdio_copy uffdio_copy; | |
1386 | struct uffdio_copy __user *user_uffdio_copy; | |
1387 | struct userfaultfd_wake_range range; | |
1388 | ||
1389 | user_uffdio_copy = (struct uffdio_copy __user *) arg; | |
1390 | ||
1391 | ret = -EFAULT; | |
1392 | if (copy_from_user(&uffdio_copy, user_uffdio_copy, | |
1393 | /* don't copy "copy" last field */ | |
1394 | sizeof(uffdio_copy)-sizeof(__s64))) | |
1395 | goto out; | |
1396 | ||
1397 | ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len); | |
1398 | if (ret) | |
1399 | goto out; | |
1400 | /* | |
1401 | * double check for wraparound just in case. copy_from_user() | |
1402 | * will later check uffdio_copy.src + uffdio_copy.len to fit | |
1403 | * in the userland range. | |
1404 | */ | |
1405 | ret = -EINVAL; | |
1406 | if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src) | |
1407 | goto out; | |
1408 | if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE) | |
1409 | goto out; | |
d2005e3f ON |
1410 | if (mmget_not_zero(ctx->mm)) { |
1411 | ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src, | |
1412 | uffdio_copy.len); | |
1413 | mmput(ctx->mm); | |
1414 | } | |
ad465cae AA |
1415 | if (unlikely(put_user(ret, &user_uffdio_copy->copy))) |
1416 | return -EFAULT; | |
1417 | if (ret < 0) | |
1418 | goto out; | |
1419 | BUG_ON(!ret); | |
1420 | /* len == 0 would wake all */ | |
1421 | range.len = ret; | |
1422 | if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) { | |
1423 | range.start = uffdio_copy.dst; | |
1424 | wake_userfault(ctx, &range); | |
1425 | } | |
1426 | ret = range.len == uffdio_copy.len ? 0 : -EAGAIN; | |
1427 | out: | |
1428 | return ret; | |
1429 | } | |
1430 | ||
1431 | static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx, | |
1432 | unsigned long arg) | |
1433 | { | |
1434 | __s64 ret; | |
1435 | struct uffdio_zeropage uffdio_zeropage; | |
1436 | struct uffdio_zeropage __user *user_uffdio_zeropage; | |
1437 | struct userfaultfd_wake_range range; | |
1438 | ||
1439 | user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg; | |
1440 | ||
1441 | ret = -EFAULT; | |
1442 | if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage, | |
1443 | /* don't copy "zeropage" last field */ | |
1444 | sizeof(uffdio_zeropage)-sizeof(__s64))) | |
1445 | goto out; | |
1446 | ||
1447 | ret = validate_range(ctx->mm, uffdio_zeropage.range.start, | |
1448 | uffdio_zeropage.range.len); | |
1449 | if (ret) | |
1450 | goto out; | |
1451 | ret = -EINVAL; | |
1452 | if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE) | |
1453 | goto out; | |
1454 | ||
d2005e3f ON |
1455 | if (mmget_not_zero(ctx->mm)) { |
1456 | ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start, | |
1457 | uffdio_zeropage.range.len); | |
1458 | mmput(ctx->mm); | |
1459 | } | |
ad465cae AA |
1460 | if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage))) |
1461 | return -EFAULT; | |
1462 | if (ret < 0) | |
1463 | goto out; | |
1464 | /* len == 0 would wake all */ | |
1465 | BUG_ON(!ret); | |
1466 | range.len = ret; | |
1467 | if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) { | |
1468 | range.start = uffdio_zeropage.range.start; | |
1469 | wake_userfault(ctx, &range); | |
1470 | } | |
1471 | ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN; | |
1472 | out: | |
1473 | return ret; | |
1474 | } | |
1475 | ||
9cd75c3c PE |
1476 | static inline unsigned int uffd_ctx_features(__u64 user_features) |
1477 | { | |
1478 | /* | |
1479 | * For the current set of features the bits just coincide | |
1480 | */ | |
1481 | return (unsigned int)user_features; | |
1482 | } | |
1483 | ||
86039bd3 AA |
1484 | /* |
1485 | * userland asks for a certain API version and we return which bits | |
1486 | * and ioctl commands are implemented in this kernel for such API | |
1487 | * version or -EINVAL if unknown. | |
1488 | */ | |
1489 | static int userfaultfd_api(struct userfaultfd_ctx *ctx, | |
1490 | unsigned long arg) | |
1491 | { | |
1492 | struct uffdio_api uffdio_api; | |
1493 | void __user *buf = (void __user *)arg; | |
1494 | int ret; | |
65603144 | 1495 | __u64 features; |
86039bd3 AA |
1496 | |
1497 | ret = -EINVAL; | |
1498 | if (ctx->state != UFFD_STATE_WAIT_API) | |
1499 | goto out; | |
1500 | ret = -EFAULT; | |
a9b85f94 | 1501 | if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api))) |
86039bd3 | 1502 | goto out; |
65603144 AA |
1503 | features = uffdio_api.features; |
1504 | if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) { | |
86039bd3 AA |
1505 | memset(&uffdio_api, 0, sizeof(uffdio_api)); |
1506 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1507 | goto out; | |
1508 | ret = -EINVAL; | |
1509 | goto out; | |
1510 | } | |
65603144 AA |
1511 | /* report all available features and ioctls to userland */ |
1512 | uffdio_api.features = UFFD_API_FEATURES; | |
86039bd3 AA |
1513 | uffdio_api.ioctls = UFFD_API_IOCTLS; |
1514 | ret = -EFAULT; | |
1515 | if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api))) | |
1516 | goto out; | |
1517 | ctx->state = UFFD_STATE_RUNNING; | |
65603144 AA |
1518 | /* only enable the requested features for this uffd context */ |
1519 | ctx->features = uffd_ctx_features(features); | |
86039bd3 AA |
1520 | ret = 0; |
1521 | out: | |
1522 | return ret; | |
1523 | } | |
1524 | ||
1525 | static long userfaultfd_ioctl(struct file *file, unsigned cmd, | |
1526 | unsigned long arg) | |
1527 | { | |
1528 | int ret = -EINVAL; | |
1529 | struct userfaultfd_ctx *ctx = file->private_data; | |
1530 | ||
e6485a47 AA |
1531 | if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API) |
1532 | return -EINVAL; | |
1533 | ||
86039bd3 AA |
1534 | switch(cmd) { |
1535 | case UFFDIO_API: | |
1536 | ret = userfaultfd_api(ctx, arg); | |
1537 | break; | |
1538 | case UFFDIO_REGISTER: | |
1539 | ret = userfaultfd_register(ctx, arg); | |
1540 | break; | |
1541 | case UFFDIO_UNREGISTER: | |
1542 | ret = userfaultfd_unregister(ctx, arg); | |
1543 | break; | |
1544 | case UFFDIO_WAKE: | |
1545 | ret = userfaultfd_wake(ctx, arg); | |
1546 | break; | |
ad465cae AA |
1547 | case UFFDIO_COPY: |
1548 | ret = userfaultfd_copy(ctx, arg); | |
1549 | break; | |
1550 | case UFFDIO_ZEROPAGE: | |
1551 | ret = userfaultfd_zeropage(ctx, arg); | |
1552 | break; | |
86039bd3 AA |
1553 | } |
1554 | return ret; | |
1555 | } | |
1556 | ||
1557 | #ifdef CONFIG_PROC_FS | |
1558 | static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f) | |
1559 | { | |
1560 | struct userfaultfd_ctx *ctx = f->private_data; | |
1561 | wait_queue_t *wq; | |
1562 | struct userfaultfd_wait_queue *uwq; | |
1563 | unsigned long pending = 0, total = 0; | |
1564 | ||
15b726ef AA |
1565 | spin_lock(&ctx->fault_pending_wqh.lock); |
1566 | list_for_each_entry(wq, &ctx->fault_pending_wqh.task_list, task_list) { | |
1567 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); | |
1568 | pending++; | |
1569 | total++; | |
1570 | } | |
86039bd3 AA |
1571 | list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) { |
1572 | uwq = container_of(wq, struct userfaultfd_wait_queue, wq); | |
86039bd3 AA |
1573 | total++; |
1574 | } | |
15b726ef | 1575 | spin_unlock(&ctx->fault_pending_wqh.lock); |
86039bd3 AA |
1576 | |
1577 | /* | |
1578 | * If more protocols will be added, there will be all shown | |
1579 | * separated by a space. Like this: | |
1580 | * protocols: aa:... bb:... | |
1581 | */ | |
1582 | seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n", | |
3f602d27 | 1583 | pending, total, UFFD_API, UFFD_API_FEATURES, |
86039bd3 AA |
1584 | UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS); |
1585 | } | |
1586 | #endif | |
1587 | ||
1588 | static const struct file_operations userfaultfd_fops = { | |
1589 | #ifdef CONFIG_PROC_FS | |
1590 | .show_fdinfo = userfaultfd_show_fdinfo, | |
1591 | #endif | |
1592 | .release = userfaultfd_release, | |
1593 | .poll = userfaultfd_poll, | |
1594 | .read = userfaultfd_read, | |
1595 | .unlocked_ioctl = userfaultfd_ioctl, | |
1596 | .compat_ioctl = userfaultfd_ioctl, | |
1597 | .llseek = noop_llseek, | |
1598 | }; | |
1599 | ||
3004ec9c AA |
1600 | static void init_once_userfaultfd_ctx(void *mem) |
1601 | { | |
1602 | struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem; | |
1603 | ||
1604 | init_waitqueue_head(&ctx->fault_pending_wqh); | |
1605 | init_waitqueue_head(&ctx->fault_wqh); | |
9cd75c3c | 1606 | init_waitqueue_head(&ctx->event_wqh); |
3004ec9c | 1607 | init_waitqueue_head(&ctx->fd_wqh); |
2c5b7e1b | 1608 | seqcount_init(&ctx->refile_seq); |
3004ec9c AA |
1609 | } |
1610 | ||
86039bd3 AA |
1611 | /** |
1612 | * userfaultfd_file_create - Creates an userfaultfd file pointer. | |
1613 | * @flags: Flags for the userfaultfd file. | |
1614 | * | |
1615 | * This function creates an userfaultfd file pointer, w/out installing | |
1616 | * it into the fd table. This is useful when the userfaultfd file is | |
1617 | * used during the initialization of data structures that require | |
1618 | * extra setup after the userfaultfd creation. So the userfaultfd | |
1619 | * creation is split into the file pointer creation phase, and the | |
1620 | * file descriptor installation phase. In this way races with | |
1621 | * userspace closing the newly installed file descriptor can be | |
1622 | * avoided. Returns an userfaultfd file pointer, or a proper error | |
1623 | * pointer. | |
1624 | */ | |
1625 | static struct file *userfaultfd_file_create(int flags) | |
1626 | { | |
1627 | struct file *file; | |
1628 | struct userfaultfd_ctx *ctx; | |
1629 | ||
1630 | BUG_ON(!current->mm); | |
1631 | ||
1632 | /* Check the UFFD_* constants for consistency. */ | |
1633 | BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC); | |
1634 | BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK); | |
1635 | ||
1636 | file = ERR_PTR(-EINVAL); | |
1637 | if (flags & ~UFFD_SHARED_FCNTL_FLAGS) | |
1638 | goto out; | |
1639 | ||
1640 | file = ERR_PTR(-ENOMEM); | |
3004ec9c | 1641 | ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL); |
86039bd3 AA |
1642 | if (!ctx) |
1643 | goto out; | |
1644 | ||
1645 | atomic_set(&ctx->refcount, 1); | |
86039bd3 | 1646 | ctx->flags = flags; |
9cd75c3c | 1647 | ctx->features = 0; |
86039bd3 AA |
1648 | ctx->state = UFFD_STATE_WAIT_API; |
1649 | ctx->released = false; | |
1650 | ctx->mm = current->mm; | |
1651 | /* prevent the mm struct to be freed */ | |
d2005e3f | 1652 | atomic_inc(&ctx->mm->mm_count); |
86039bd3 AA |
1653 | |
1654 | file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx, | |
1655 | O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS)); | |
c03e946f | 1656 | if (IS_ERR(file)) { |
d2005e3f | 1657 | mmdrop(ctx->mm); |
3004ec9c | 1658 | kmem_cache_free(userfaultfd_ctx_cachep, ctx); |
c03e946f | 1659 | } |
86039bd3 AA |
1660 | out: |
1661 | return file; | |
1662 | } | |
1663 | ||
1664 | SYSCALL_DEFINE1(userfaultfd, int, flags) | |
1665 | { | |
1666 | int fd, error; | |
1667 | struct file *file; | |
1668 | ||
1669 | error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS); | |
1670 | if (error < 0) | |
1671 | return error; | |
1672 | fd = error; | |
1673 | ||
1674 | file = userfaultfd_file_create(flags); | |
1675 | if (IS_ERR(file)) { | |
1676 | error = PTR_ERR(file); | |
1677 | goto err_put_unused_fd; | |
1678 | } | |
1679 | fd_install(fd, file); | |
1680 | ||
1681 | return fd; | |
1682 | ||
1683 | err_put_unused_fd: | |
1684 | put_unused_fd(fd); | |
1685 | ||
1686 | return error; | |
1687 | } | |
3004ec9c AA |
1688 | |
1689 | static int __init userfaultfd_init(void) | |
1690 | { | |
1691 | userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache", | |
1692 | sizeof(struct userfaultfd_ctx), | |
1693 | 0, | |
1694 | SLAB_HWCACHE_ALIGN|SLAB_PANIC, | |
1695 | init_once_userfaultfd_ctx); | |
1696 | return 0; | |
1697 | } | |
1698 | __initcall(userfaultfd_init); |