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