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CommitLineData
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 16#include <linux/hashtable.h>
174cd4b1 17#include <linux/sched/signal.h>
6e84f315 18#include <linux/sched/mm.h>
86039bd3
AA
19#include <linux/mm.h>
20#include <linux/poll.h>
21#include <linux/slab.h>
22#include <linux/seq_file.h>
23#include <linux/file.h>
24#include <linux/bug.h>
25#include <linux/anon_inodes.h>
26#include <linux/syscalls.h>
27#include <linux/userfaultfd_k.h>
28#include <linux/mempolicy.h>
29#include <linux/ioctl.h>
30#include <linux/security.h>
cab350af 31#include <linux/hugetlb.h>
86039bd3 32
3004ec9c
AA
33static struct kmem_cache *userfaultfd_ctx_cachep __read_mostly;
34
86039bd3
AA
35enum userfaultfd_state {
36 UFFD_STATE_WAIT_API,
37 UFFD_STATE_RUNNING,
38};
39
3004ec9c
AA
40/*
41 * Start with fault_pending_wqh and fault_wqh so they're more likely
42 * to be in the same cacheline.
43 */
86039bd3 44struct userfaultfd_ctx {
15b726ef
AA
45 /* waitqueue head for the pending (i.e. not read) userfaults */
46 wait_queue_head_t fault_pending_wqh;
47 /* waitqueue head for the userfaults */
86039bd3
AA
48 wait_queue_head_t fault_wqh;
49 /* waitqueue head for the pseudo fd to wakeup poll/read */
50 wait_queue_head_t fd_wqh;
9cd75c3c
PE
51 /* waitqueue head for events */
52 wait_queue_head_t event_wqh;
2c5b7e1b
AA
53 /* a refile sequence protected by fault_pending_wqh lock */
54 struct seqcount refile_seq;
3004ec9c
AA
55 /* pseudo fd refcounting */
56 atomic_t refcount;
86039bd3
AA
57 /* userfaultfd syscall flags */
58 unsigned int flags;
9cd75c3c
PE
59 /* features requested from the userspace */
60 unsigned int features;
86039bd3
AA
61 /* state machine */
62 enum userfaultfd_state state;
63 /* released */
64 bool released;
df2cc96e
MR
65 /* memory mappings are changing because of non-cooperative event */
66 bool mmap_changing;
86039bd3
AA
67 /* mm with one ore more vmas attached to this userfaultfd_ctx */
68 struct mm_struct *mm;
69};
70
893e26e6
PE
71struct userfaultfd_fork_ctx {
72 struct userfaultfd_ctx *orig;
73 struct userfaultfd_ctx *new;
74 struct list_head list;
75};
76
897ab3e0
MR
77struct userfaultfd_unmap_ctx {
78 struct userfaultfd_ctx *ctx;
79 unsigned long start;
80 unsigned long end;
81 struct list_head list;
82};
83
86039bd3 84struct userfaultfd_wait_queue {
a9b85f94 85 struct uffd_msg msg;
ac6424b9 86 wait_queue_entry_t wq;
86039bd3 87 struct userfaultfd_ctx *ctx;
15a77c6f 88 bool waken;
86039bd3
AA
89};
90
91struct userfaultfd_wake_range {
92 unsigned long start;
93 unsigned long len;
94};
95
ac6424b9 96static int userfaultfd_wake_function(wait_queue_entry_t *wq, unsigned mode,
86039bd3
AA
97 int wake_flags, void *key)
98{
99 struct userfaultfd_wake_range *range = key;
100 int ret;
101 struct userfaultfd_wait_queue *uwq;
102 unsigned long start, len;
103
104 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
105 ret = 0;
86039bd3
AA
106 /* len == 0 means wake all */
107 start = range->start;
108 len = range->len;
a9b85f94
AA
109 if (len && (start > uwq->msg.arg.pagefault.address ||
110 start + len <= uwq->msg.arg.pagefault.address))
86039bd3 111 goto out;
15a77c6f
AA
112 WRITE_ONCE(uwq->waken, true);
113 /*
a9668cd6
PZ
114 * The Program-Order guarantees provided by the scheduler
115 * ensure uwq->waken is visible before the task is woken.
15a77c6f 116 */
86039bd3 117 ret = wake_up_state(wq->private, mode);
a9668cd6 118 if (ret) {
86039bd3
AA
119 /*
120 * Wake only once, autoremove behavior.
121 *
a9668cd6
PZ
122 * After the effect of list_del_init is visible to the other
123 * CPUs, the waitqueue may disappear from under us, see the
124 * !list_empty_careful() in handle_userfault().
125 *
126 * try_to_wake_up() has an implicit smp_mb(), and the
127 * wq->private is read before calling the extern function
128 * "wake_up_state" (which in turns calls try_to_wake_up).
86039bd3 129 */
2055da97 130 list_del_init(&wq->entry);
a9668cd6 131 }
86039bd3
AA
132out:
133 return ret;
134}
135
136/**
137 * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd
138 * context.
139 * @ctx: [in] Pointer to the userfaultfd context.
86039bd3
AA
140 */
141static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
142{
143 if (!atomic_inc_not_zero(&ctx->refcount))
144 BUG();
145}
146
147/**
148 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd
149 * context.
150 * @ctx: [in] Pointer to userfaultfd context.
151 *
152 * The userfaultfd context reference must have been previously acquired either
153 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget().
154 */
155static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx)
156{
157 if (atomic_dec_and_test(&ctx->refcount)) {
158 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock));
159 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh));
160 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock));
161 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh));
9cd75c3c
PE
162 VM_BUG_ON(spin_is_locked(&ctx->event_wqh.lock));
163 VM_BUG_ON(waitqueue_active(&ctx->event_wqh));
86039bd3
AA
164 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock));
165 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh));
d2005e3f 166 mmdrop(ctx->mm);
3004ec9c 167 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
86039bd3
AA
168 }
169}
170
a9b85f94 171static inline void msg_init(struct uffd_msg *msg)
86039bd3 172{
a9b85f94
AA
173 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32);
174 /*
175 * Must use memset to zero out the paddings or kernel data is
176 * leaked to userland.
177 */
178 memset(msg, 0, sizeof(struct uffd_msg));
179}
180
181static inline struct uffd_msg userfault_msg(unsigned long address,
182 unsigned int flags,
9d4ac934
AP
183 unsigned long reason,
184 unsigned int features)
a9b85f94
AA
185{
186 struct uffd_msg msg;
187 msg_init(&msg);
188 msg.event = UFFD_EVENT_PAGEFAULT;
189 msg.arg.pagefault.address = address;
86039bd3
AA
190 if (flags & FAULT_FLAG_WRITE)
191 /*
a4605a61 192 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
a9b85f94
AA
193 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE
194 * was not set in a UFFD_EVENT_PAGEFAULT, it means it
195 * was a read fault, otherwise if set it means it's
196 * a write fault.
86039bd3 197 */
a9b85f94 198 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
86039bd3
AA
199 if (reason & VM_UFFD_WP)
200 /*
a9b85f94
AA
201 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
202 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was
203 * not set in a UFFD_EVENT_PAGEFAULT, it means it was
204 * a missing fault, otherwise if set it means it's a
205 * write protect fault.
86039bd3 206 */
a9b85f94 207 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
9d4ac934 208 if (features & UFFD_FEATURE_THREAD_ID)
a36985d3 209 msg.arg.pagefault.feat.ptid = task_pid_vnr(current);
a9b85f94 210 return msg;
86039bd3
AA
211}
212
369cd212
MK
213#ifdef CONFIG_HUGETLB_PAGE
214/*
215 * Same functionality as userfaultfd_must_wait below with modifications for
216 * hugepmd ranges.
217 */
218static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
7868a208 219 struct vm_area_struct *vma,
369cd212
MK
220 unsigned long address,
221 unsigned long flags,
222 unsigned long reason)
223{
224 struct mm_struct *mm = ctx->mm;
1e2c0436 225 pte_t *ptep, pte;
369cd212
MK
226 bool ret = true;
227
228 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
229
1e2c0436
JF
230 ptep = huge_pte_offset(mm, address, vma_mmu_pagesize(vma));
231
232 if (!ptep)
369cd212
MK
233 goto out;
234
235 ret = false;
1e2c0436 236 pte = huge_ptep_get(ptep);
369cd212
MK
237
238 /*
239 * Lockless access: we're in a wait_event so it's ok if it
240 * changes under us.
241 */
1e2c0436 242 if (huge_pte_none(pte))
369cd212 243 ret = true;
1e2c0436 244 if (!huge_pte_write(pte) && (reason & VM_UFFD_WP))
369cd212
MK
245 ret = true;
246out:
247 return ret;
248}
249#else
250static inline bool userfaultfd_huge_must_wait(struct userfaultfd_ctx *ctx,
7868a208 251 struct vm_area_struct *vma,
369cd212
MK
252 unsigned long address,
253 unsigned long flags,
254 unsigned long reason)
255{
256 return false; /* should never get here */
257}
258#endif /* CONFIG_HUGETLB_PAGE */
259
8d2afd96
AA
260/*
261 * Verify the pagetables are still not ok after having reigstered into
262 * the fault_pending_wqh to avoid userland having to UFFDIO_WAKE any
263 * userfault that has already been resolved, if userfaultfd_read and
264 * UFFDIO_COPY|ZEROPAGE are being run simultaneously on two different
265 * threads.
266 */
267static inline bool userfaultfd_must_wait(struct userfaultfd_ctx *ctx,
268 unsigned long address,
269 unsigned long flags,
270 unsigned long reason)
271{
272 struct mm_struct *mm = ctx->mm;
273 pgd_t *pgd;
c2febafc 274 p4d_t *p4d;
8d2afd96
AA
275 pud_t *pud;
276 pmd_t *pmd, _pmd;
277 pte_t *pte;
278 bool ret = true;
279
280 VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
281
282 pgd = pgd_offset(mm, address);
283 if (!pgd_present(*pgd))
284 goto out;
c2febafc
KS
285 p4d = p4d_offset(pgd, address);
286 if (!p4d_present(*p4d))
287 goto out;
288 pud = pud_offset(p4d, address);
8d2afd96
AA
289 if (!pud_present(*pud))
290 goto out;
291 pmd = pmd_offset(pud, address);
292 /*
293 * READ_ONCE must function as a barrier with narrower scope
294 * and it must be equivalent to:
295 * _pmd = *pmd; barrier();
296 *
297 * This is to deal with the instability (as in
298 * pmd_trans_unstable) of the pmd.
299 */
300 _pmd = READ_ONCE(*pmd);
a365ac09 301 if (pmd_none(_pmd))
8d2afd96
AA
302 goto out;
303
304 ret = false;
a365ac09
HY
305 if (!pmd_present(_pmd))
306 goto out;
307
8d2afd96
AA
308 if (pmd_trans_huge(_pmd))
309 goto out;
310
311 /*
312 * the pmd is stable (as in !pmd_trans_unstable) so we can re-read it
313 * and use the standard pte_offset_map() instead of parsing _pmd.
314 */
315 pte = pte_offset_map(pmd, address);
316 /*
317 * Lockless access: we're in a wait_event so it's ok if it
318 * changes under us.
319 */
320 if (pte_none(*pte))
321 ret = true;
322 pte_unmap(pte);
323
324out:
325 return ret;
326}
327
86039bd3
AA
328/*
329 * The locking rules involved in returning VM_FAULT_RETRY depending on
330 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and
331 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution"
332 * recommendation in __lock_page_or_retry is not an understatement.
333 *
334 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released
335 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is
336 * not set.
337 *
338 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not
339 * set, VM_FAULT_RETRY can still be returned if and only if there are
340 * fatal_signal_pending()s, and the mmap_sem must be released before
341 * returning it.
342 */
2b740303 343vm_fault_t handle_userfault(struct vm_fault *vmf, unsigned long reason)
86039bd3 344{
82b0f8c3 345 struct mm_struct *mm = vmf->vma->vm_mm;
86039bd3
AA
346 struct userfaultfd_ctx *ctx;
347 struct userfaultfd_wait_queue uwq;
2b740303 348 vm_fault_t ret = VM_FAULT_SIGBUS;
dfa37dc3 349 bool must_wait, return_to_userland;
15a77c6f 350 long blocking_state;
86039bd3 351
64c2b203
AA
352 /*
353 * We don't do userfault handling for the final child pid update.
354 *
355 * We also don't do userfault handling during
356 * coredumping. hugetlbfs has the special
357 * follow_hugetlb_page() to skip missing pages in the
358 * FOLL_DUMP case, anon memory also checks for FOLL_DUMP with
359 * the no_page_table() helper in follow_page_mask(), but the
360 * shmem_vm_ops->fault method is invoked even during
361 * coredumping without mmap_sem and it ends up here.
362 */
363 if (current->flags & (PF_EXITING|PF_DUMPCORE))
364 goto out;
365
366 /*
367 * Coredumping runs without mmap_sem so we can only check that
368 * the mmap_sem is held, if PF_DUMPCORE was not set.
369 */
370 WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
371
82b0f8c3 372 ctx = vmf->vma->vm_userfaultfd_ctx.ctx;
86039bd3 373 if (!ctx)
ba85c702 374 goto out;
86039bd3
AA
375
376 BUG_ON(ctx->mm != mm);
377
378 VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP));
379 VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP));
380
2d6d6f5a
PS
381 if (ctx->features & UFFD_FEATURE_SIGBUS)
382 goto out;
383
86039bd3
AA
384 /*
385 * If it's already released don't get it. This avoids to loop
386 * in __get_user_pages if userfaultfd_release waits on the
387 * caller of handle_userfault to release the mmap_sem.
388 */
6aa7de05 389 if (unlikely(READ_ONCE(ctx->released))) {
656710a6
AA
390 /*
391 * Don't return VM_FAULT_SIGBUS in this case, so a non
392 * cooperative manager can close the uffd after the
393 * last UFFDIO_COPY, without risking to trigger an
394 * involuntary SIGBUS if the process was starting the
395 * userfaultfd while the userfaultfd was still armed
396 * (but after the last UFFDIO_COPY). If the uffd
397 * wasn't already closed when the userfault reached
398 * this point, that would normally be solved by
399 * userfaultfd_must_wait returning 'false'.
400 *
401 * If we were to return VM_FAULT_SIGBUS here, the non
402 * cooperative manager would be instead forced to
403 * always call UFFDIO_UNREGISTER before it can safely
404 * close the uffd.
405 */
406 ret = VM_FAULT_NOPAGE;
ba85c702 407 goto out;
656710a6 408 }
86039bd3
AA
409
410 /*
411 * Check that we can return VM_FAULT_RETRY.
412 *
413 * NOTE: it should become possible to return VM_FAULT_RETRY
414 * even if FAULT_FLAG_TRIED is set without leading to gup()
415 * -EBUSY failures, if the userfaultfd is to be extended for
416 * VM_UFFD_WP tracking and we intend to arm the userfault
417 * without first stopping userland access to the memory. For
418 * VM_UFFD_MISSING userfaults this is enough for now.
419 */
82b0f8c3 420 if (unlikely(!(vmf->flags & FAULT_FLAG_ALLOW_RETRY))) {
86039bd3
AA
421 /*
422 * Validate the invariant that nowait must allow retry
423 * to be sure not to return SIGBUS erroneously on
424 * nowait invocations.
425 */
82b0f8c3 426 BUG_ON(vmf->flags & FAULT_FLAG_RETRY_NOWAIT);
86039bd3
AA
427#ifdef CONFIG_DEBUG_VM
428 if (printk_ratelimit()) {
429 printk(KERN_WARNING
82b0f8c3
JK
430 "FAULT_FLAG_ALLOW_RETRY missing %x\n",
431 vmf->flags);
86039bd3
AA
432 dump_stack();
433 }
434#endif
ba85c702 435 goto out;
86039bd3
AA
436 }
437
438 /*
439 * Handle nowait, not much to do other than tell it to retry
440 * and wait.
441 */
ba85c702 442 ret = VM_FAULT_RETRY;
82b0f8c3 443 if (vmf->flags & FAULT_FLAG_RETRY_NOWAIT)
ba85c702 444 goto out;
86039bd3
AA
445
446 /* take the reference before dropping the mmap_sem */
447 userfaultfd_ctx_get(ctx);
448
86039bd3
AA
449 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
450 uwq.wq.private = current;
9d4ac934
AP
451 uwq.msg = userfault_msg(vmf->address, vmf->flags, reason,
452 ctx->features);
86039bd3 453 uwq.ctx = ctx;
15a77c6f 454 uwq.waken = false;
86039bd3 455
bae473a4 456 return_to_userland =
82b0f8c3 457 (vmf->flags & (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE)) ==
dfa37dc3 458 (FAULT_FLAG_USER|FAULT_FLAG_KILLABLE);
15a77c6f
AA
459 blocking_state = return_to_userland ? TASK_INTERRUPTIBLE :
460 TASK_KILLABLE;
dfa37dc3 461
15b726ef 462 spin_lock(&ctx->fault_pending_wqh.lock);
86039bd3
AA
463 /*
464 * After the __add_wait_queue the uwq is visible to userland
465 * through poll/read().
466 */
15b726ef
AA
467 __add_wait_queue(&ctx->fault_pending_wqh, &uwq.wq);
468 /*
469 * The smp_mb() after __set_current_state prevents the reads
470 * following the spin_unlock to happen before the list_add in
471 * __add_wait_queue.
472 */
15a77c6f 473 set_current_state(blocking_state);
15b726ef 474 spin_unlock(&ctx->fault_pending_wqh.lock);
86039bd3 475
369cd212
MK
476 if (!is_vm_hugetlb_page(vmf->vma))
477 must_wait = userfaultfd_must_wait(ctx, vmf->address, vmf->flags,
478 reason);
479 else
7868a208
PA
480 must_wait = userfaultfd_huge_must_wait(ctx, vmf->vma,
481 vmf->address,
369cd212 482 vmf->flags, reason);
8d2afd96
AA
483 up_read(&mm->mmap_sem);
484
6aa7de05 485 if (likely(must_wait && !READ_ONCE(ctx->released) &&
dfa37dc3
AA
486 (return_to_userland ? !signal_pending(current) :
487 !fatal_signal_pending(current)))) {
a9a08845 488 wake_up_poll(&ctx->fd_wqh, EPOLLIN);
86039bd3 489 schedule();
ba85c702 490 ret |= VM_FAULT_MAJOR;
15a77c6f
AA
491
492 /*
493 * False wakeups can orginate even from rwsem before
494 * up_read() however userfaults will wait either for a
495 * targeted wakeup on the specific uwq waitqueue from
496 * wake_userfault() or for signals or for uffd
497 * release.
498 */
499 while (!READ_ONCE(uwq.waken)) {
500 /*
501 * This needs the full smp_store_mb()
502 * guarantee as the state write must be
503 * visible to other CPUs before reading
504 * uwq.waken from other CPUs.
505 */
506 set_current_state(blocking_state);
507 if (READ_ONCE(uwq.waken) ||
508 READ_ONCE(ctx->released) ||
509 (return_to_userland ? signal_pending(current) :
510 fatal_signal_pending(current)))
511 break;
512 schedule();
513 }
ba85c702 514 }
86039bd3 515
ba85c702 516 __set_current_state(TASK_RUNNING);
15b726ef 517
dfa37dc3
AA
518 if (return_to_userland) {
519 if (signal_pending(current) &&
520 !fatal_signal_pending(current)) {
521 /*
522 * If we got a SIGSTOP or SIGCONT and this is
523 * a normal userland page fault, just let
524 * userland return so the signal will be
525 * handled and gdb debugging works. The page
526 * fault code immediately after we return from
527 * this function is going to release the
528 * mmap_sem and it's not depending on it
529 * (unlike gup would if we were not to return
530 * VM_FAULT_RETRY).
531 *
532 * If a fatal signal is pending we still take
533 * the streamlined VM_FAULT_RETRY failure path
534 * and there's no need to retake the mmap_sem
535 * in such case.
536 */
537 down_read(&mm->mmap_sem);
6bbc4a41 538 ret = VM_FAULT_NOPAGE;
dfa37dc3
AA
539 }
540 }
541
15b726ef
AA
542 /*
543 * Here we race with the list_del; list_add in
544 * userfaultfd_ctx_read(), however because we don't ever run
545 * list_del_init() to refile across the two lists, the prev
546 * and next pointers will never point to self. list_add also
547 * would never let any of the two pointers to point to
548 * self. So list_empty_careful won't risk to see both pointers
549 * pointing to self at any time during the list refile. The
550 * only case where list_del_init() is called is the full
551 * removal in the wake function and there we don't re-list_add
552 * and it's fine not to block on the spinlock. The uwq on this
553 * kernel stack can be released after the list_del_init.
554 */
2055da97 555 if (!list_empty_careful(&uwq.wq.entry)) {
15b726ef
AA
556 spin_lock(&ctx->fault_pending_wqh.lock);
557 /*
558 * No need of list_del_init(), the uwq on the stack
559 * will be freed shortly anyway.
560 */
2055da97 561 list_del(&uwq.wq.entry);
15b726ef 562 spin_unlock(&ctx->fault_pending_wqh.lock);
86039bd3 563 }
86039bd3
AA
564
565 /*
566 * ctx may go away after this if the userfault pseudo fd is
567 * already released.
568 */
569 userfaultfd_ctx_put(ctx);
570
ba85c702
AA
571out:
572 return ret;
86039bd3
AA
573}
574
8c9e7bb7
AA
575static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
576 struct userfaultfd_wait_queue *ewq)
9cd75c3c 577{
0cbb4b4f
AA
578 struct userfaultfd_ctx *release_new_ctx;
579
9a69a829
AA
580 if (WARN_ON_ONCE(current->flags & PF_EXITING))
581 goto out;
9cd75c3c
PE
582
583 ewq->ctx = ctx;
584 init_waitqueue_entry(&ewq->wq, current);
0cbb4b4f 585 release_new_ctx = NULL;
9cd75c3c
PE
586
587 spin_lock(&ctx->event_wqh.lock);
588 /*
589 * After the __add_wait_queue the uwq is visible to userland
590 * through poll/read().
591 */
592 __add_wait_queue(&ctx->event_wqh, &ewq->wq);
593 for (;;) {
594 set_current_state(TASK_KILLABLE);
595 if (ewq->msg.event == 0)
596 break;
6aa7de05 597 if (READ_ONCE(ctx->released) ||
9cd75c3c 598 fatal_signal_pending(current)) {
384632e6
AA
599 /*
600 * &ewq->wq may be queued in fork_event, but
601 * __remove_wait_queue ignores the head
602 * parameter. It would be a problem if it
603 * didn't.
604 */
9cd75c3c 605 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
7eb76d45
MR
606 if (ewq->msg.event == UFFD_EVENT_FORK) {
607 struct userfaultfd_ctx *new;
608
609 new = (struct userfaultfd_ctx *)
610 (unsigned long)
611 ewq->msg.arg.reserved.reserved1;
0cbb4b4f 612 release_new_ctx = new;
7eb76d45 613 }
9cd75c3c
PE
614 break;
615 }
616
617 spin_unlock(&ctx->event_wqh.lock);
618
a9a08845 619 wake_up_poll(&ctx->fd_wqh, EPOLLIN);
9cd75c3c
PE
620 schedule();
621
622 spin_lock(&ctx->event_wqh.lock);
623 }
624 __set_current_state(TASK_RUNNING);
625 spin_unlock(&ctx->event_wqh.lock);
626
0cbb4b4f
AA
627 if (release_new_ctx) {
628 struct vm_area_struct *vma;
629 struct mm_struct *mm = release_new_ctx->mm;
630
631 /* the various vma->vm_userfaultfd_ctx still points to it */
632 down_write(&mm->mmap_sem);
633 for (vma = mm->mmap; vma; vma = vma->vm_next)
31e810aa 634 if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx) {
0cbb4b4f 635 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
31e810aa
MR
636 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
637 }
0cbb4b4f
AA
638 up_write(&mm->mmap_sem);
639
640 userfaultfd_ctx_put(release_new_ctx);
641 }
642
9cd75c3c
PE
643 /*
644 * ctx may go away after this if the userfault pseudo fd is
645 * already released.
646 */
9a69a829 647out:
df2cc96e 648 WRITE_ONCE(ctx->mmap_changing, false);
9cd75c3c 649 userfaultfd_ctx_put(ctx);
9cd75c3c
PE
650}
651
652static void userfaultfd_event_complete(struct userfaultfd_ctx *ctx,
653 struct userfaultfd_wait_queue *ewq)
654{
655 ewq->msg.event = 0;
656 wake_up_locked(&ctx->event_wqh);
657 __remove_wait_queue(&ctx->event_wqh, &ewq->wq);
658}
659
893e26e6
PE
660int dup_userfaultfd(struct vm_area_struct *vma, struct list_head *fcs)
661{
662 struct userfaultfd_ctx *ctx = NULL, *octx;
663 struct userfaultfd_fork_ctx *fctx;
664
665 octx = vma->vm_userfaultfd_ctx.ctx;
666 if (!octx || !(octx->features & UFFD_FEATURE_EVENT_FORK)) {
667 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
668 vma->vm_flags &= ~(VM_UFFD_WP | VM_UFFD_MISSING);
669 return 0;
670 }
671
672 list_for_each_entry(fctx, fcs, list)
673 if (fctx->orig == octx) {
674 ctx = fctx->new;
675 break;
676 }
677
678 if (!ctx) {
679 fctx = kmalloc(sizeof(*fctx), GFP_KERNEL);
680 if (!fctx)
681 return -ENOMEM;
682
683 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
684 if (!ctx) {
685 kfree(fctx);
686 return -ENOMEM;
687 }
688
689 atomic_set(&ctx->refcount, 1);
690 ctx->flags = octx->flags;
691 ctx->state = UFFD_STATE_RUNNING;
692 ctx->features = octx->features;
693 ctx->released = false;
df2cc96e 694 ctx->mmap_changing = false;
893e26e6 695 ctx->mm = vma->vm_mm;
00bb31fa 696 mmgrab(ctx->mm);
893e26e6
PE
697
698 userfaultfd_ctx_get(octx);
df2cc96e 699 WRITE_ONCE(octx->mmap_changing, true);
893e26e6
PE
700 fctx->orig = octx;
701 fctx->new = ctx;
702 list_add_tail(&fctx->list, fcs);
703 }
704
705 vma->vm_userfaultfd_ctx.ctx = ctx;
706 return 0;
707}
708
8c9e7bb7 709static void dup_fctx(struct userfaultfd_fork_ctx *fctx)
893e26e6
PE
710{
711 struct userfaultfd_ctx *ctx = fctx->orig;
712 struct userfaultfd_wait_queue ewq;
713
714 msg_init(&ewq.msg);
715
716 ewq.msg.event = UFFD_EVENT_FORK;
717 ewq.msg.arg.reserved.reserved1 = (unsigned long)fctx->new;
718
8c9e7bb7 719 userfaultfd_event_wait_completion(ctx, &ewq);
893e26e6
PE
720}
721
722void dup_userfaultfd_complete(struct list_head *fcs)
723{
893e26e6
PE
724 struct userfaultfd_fork_ctx *fctx, *n;
725
726 list_for_each_entry_safe(fctx, n, fcs, list) {
8c9e7bb7 727 dup_fctx(fctx);
893e26e6
PE
728 list_del(&fctx->list);
729 kfree(fctx);
730 }
731}
732
72f87654
PE
733void mremap_userfaultfd_prep(struct vm_area_struct *vma,
734 struct vm_userfaultfd_ctx *vm_ctx)
735{
736 struct userfaultfd_ctx *ctx;
737
738 ctx = vma->vm_userfaultfd_ctx.ctx;
739 if (ctx && (ctx->features & UFFD_FEATURE_EVENT_REMAP)) {
740 vm_ctx->ctx = ctx;
741 userfaultfd_ctx_get(ctx);
df2cc96e 742 WRITE_ONCE(ctx->mmap_changing, true);
72f87654
PE
743 }
744}
745
90794bf1 746void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx *vm_ctx,
72f87654
PE
747 unsigned long from, unsigned long to,
748 unsigned long len)
749{
90794bf1 750 struct userfaultfd_ctx *ctx = vm_ctx->ctx;
72f87654
PE
751 struct userfaultfd_wait_queue ewq;
752
753 if (!ctx)
754 return;
755
756 if (to & ~PAGE_MASK) {
757 userfaultfd_ctx_put(ctx);
758 return;
759 }
760
761 msg_init(&ewq.msg);
762
763 ewq.msg.event = UFFD_EVENT_REMAP;
764 ewq.msg.arg.remap.from = from;
765 ewq.msg.arg.remap.to = to;
766 ewq.msg.arg.remap.len = len;
767
768 userfaultfd_event_wait_completion(ctx, &ewq);
769}
770
70ccb92f 771bool userfaultfd_remove(struct vm_area_struct *vma,
d811914d 772 unsigned long start, unsigned long end)
05ce7724
PE
773{
774 struct mm_struct *mm = vma->vm_mm;
775 struct userfaultfd_ctx *ctx;
776 struct userfaultfd_wait_queue ewq;
777
778 ctx = vma->vm_userfaultfd_ctx.ctx;
d811914d 779 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_REMOVE))
70ccb92f 780 return true;
05ce7724
PE
781
782 userfaultfd_ctx_get(ctx);
df2cc96e 783 WRITE_ONCE(ctx->mmap_changing, true);
05ce7724
PE
784 up_read(&mm->mmap_sem);
785
05ce7724
PE
786 msg_init(&ewq.msg);
787
d811914d
MR
788 ewq.msg.event = UFFD_EVENT_REMOVE;
789 ewq.msg.arg.remove.start = start;
790 ewq.msg.arg.remove.end = end;
05ce7724
PE
791
792 userfaultfd_event_wait_completion(ctx, &ewq);
793
70ccb92f 794 return false;
05ce7724
PE
795}
796
897ab3e0
MR
797static bool has_unmap_ctx(struct userfaultfd_ctx *ctx, struct list_head *unmaps,
798 unsigned long start, unsigned long end)
799{
800 struct userfaultfd_unmap_ctx *unmap_ctx;
801
802 list_for_each_entry(unmap_ctx, unmaps, list)
803 if (unmap_ctx->ctx == ctx && unmap_ctx->start == start &&
804 unmap_ctx->end == end)
805 return true;
806
807 return false;
808}
809
810int userfaultfd_unmap_prep(struct vm_area_struct *vma,
811 unsigned long start, unsigned long end,
812 struct list_head *unmaps)
813{
814 for ( ; vma && vma->vm_start < end; vma = vma->vm_next) {
815 struct userfaultfd_unmap_ctx *unmap_ctx;
816 struct userfaultfd_ctx *ctx = vma->vm_userfaultfd_ctx.ctx;
817
818 if (!ctx || !(ctx->features & UFFD_FEATURE_EVENT_UNMAP) ||
819 has_unmap_ctx(ctx, unmaps, start, end))
820 continue;
821
822 unmap_ctx = kzalloc(sizeof(*unmap_ctx), GFP_KERNEL);
823 if (!unmap_ctx)
824 return -ENOMEM;
825
826 userfaultfd_ctx_get(ctx);
df2cc96e 827 WRITE_ONCE(ctx->mmap_changing, true);
897ab3e0
MR
828 unmap_ctx->ctx = ctx;
829 unmap_ctx->start = start;
830 unmap_ctx->end = end;
831 list_add_tail(&unmap_ctx->list, unmaps);
832 }
833
834 return 0;
835}
836
837void userfaultfd_unmap_complete(struct mm_struct *mm, struct list_head *uf)
838{
839 struct userfaultfd_unmap_ctx *ctx, *n;
840 struct userfaultfd_wait_queue ewq;
841
842 list_for_each_entry_safe(ctx, n, uf, list) {
843 msg_init(&ewq.msg);
844
845 ewq.msg.event = UFFD_EVENT_UNMAP;
846 ewq.msg.arg.remove.start = ctx->start;
847 ewq.msg.arg.remove.end = ctx->end;
848
849 userfaultfd_event_wait_completion(ctx->ctx, &ewq);
850
851 list_del(&ctx->list);
852 kfree(ctx);
853 }
854}
855
86039bd3
AA
856static int userfaultfd_release(struct inode *inode, struct file *file)
857{
858 struct userfaultfd_ctx *ctx = file->private_data;
859 struct mm_struct *mm = ctx->mm;
860 struct vm_area_struct *vma, *prev;
861 /* len == 0 means wake all */
862 struct userfaultfd_wake_range range = { .len = 0, };
863 unsigned long new_flags;
864
6aa7de05 865 WRITE_ONCE(ctx->released, true);
86039bd3 866
d2005e3f
ON
867 if (!mmget_not_zero(mm))
868 goto wakeup;
869
86039bd3
AA
870 /*
871 * Flush page faults out of all CPUs. NOTE: all page faults
872 * must be retried without returning VM_FAULT_SIGBUS if
873 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
874 * changes while handle_userfault released the mmap_sem. So
875 * it's critical that released is set to true (above), before
876 * taking the mmap_sem for writing.
877 */
878 down_write(&mm->mmap_sem);
879 prev = NULL;
880 for (vma = mm->mmap; vma; vma = vma->vm_next) {
881 cond_resched();
882 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
883 !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
884 if (vma->vm_userfaultfd_ctx.ctx != ctx) {
885 prev = vma;
886 continue;
887 }
888 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
889 prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
890 new_flags, vma->anon_vma,
891 vma->vm_file, vma->vm_pgoff,
892 vma_policy(vma),
893 NULL_VM_UFFD_CTX);
894 if (prev)
895 vma = prev;
896 else
897 prev = vma;
898 vma->vm_flags = new_flags;
899 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
900 }
901 up_write(&mm->mmap_sem);
d2005e3f
ON
902 mmput(mm);
903wakeup:
86039bd3 904 /*
15b726ef 905 * After no new page faults can wait on this fault_*wqh, flush
86039bd3 906 * the last page faults that may have been already waiting on
15b726ef 907 * the fault_*wqh.
86039bd3 908 */
15b726ef 909 spin_lock(&ctx->fault_pending_wqh.lock);
ac5be6b4 910 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL, &range);
c430d1e8 911 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, &range);
15b726ef 912 spin_unlock(&ctx->fault_pending_wqh.lock);
86039bd3 913
5a18b64e
MR
914 /* Flush pending events that may still wait on event_wqh */
915 wake_up_all(&ctx->event_wqh);
916
a9a08845 917 wake_up_poll(&ctx->fd_wqh, EPOLLHUP);
86039bd3
AA
918 userfaultfd_ctx_put(ctx);
919 return 0;
920}
921
15b726ef 922/* fault_pending_wqh.lock must be hold by the caller */
6dcc27fd
PE
923static inline struct userfaultfd_wait_queue *find_userfault_in(
924 wait_queue_head_t *wqh)
86039bd3 925{
ac6424b9 926 wait_queue_entry_t *wq;
15b726ef 927 struct userfaultfd_wait_queue *uwq;
86039bd3 928
6dcc27fd 929 VM_BUG_ON(!spin_is_locked(&wqh->lock));
86039bd3 930
15b726ef 931 uwq = NULL;
6dcc27fd 932 if (!waitqueue_active(wqh))
15b726ef
AA
933 goto out;
934 /* walk in reverse to provide FIFO behavior to read userfaults */
2055da97 935 wq = list_last_entry(&wqh->head, typeof(*wq), entry);
15b726ef
AA
936 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
937out:
938 return uwq;
86039bd3 939}
6dcc27fd
PE
940
941static inline struct userfaultfd_wait_queue *find_userfault(
942 struct userfaultfd_ctx *ctx)
943{
944 return find_userfault_in(&ctx->fault_pending_wqh);
945}
86039bd3 946
9cd75c3c
PE
947static inline struct userfaultfd_wait_queue *find_userfault_evt(
948 struct userfaultfd_ctx *ctx)
949{
950 return find_userfault_in(&ctx->event_wqh);
951}
952
076ccb76 953static __poll_t userfaultfd_poll(struct file *file, poll_table *wait)
86039bd3
AA
954{
955 struct userfaultfd_ctx *ctx = file->private_data;
076ccb76 956 __poll_t ret;
86039bd3
AA
957
958 poll_wait(file, &ctx->fd_wqh, wait);
959
960 switch (ctx->state) {
961 case UFFD_STATE_WAIT_API:
a9a08845 962 return EPOLLERR;
86039bd3 963 case UFFD_STATE_RUNNING:
ba85c702
AA
964 /*
965 * poll() never guarantees that read won't block.
966 * userfaults can be waken before they're read().
967 */
968 if (unlikely(!(file->f_flags & O_NONBLOCK)))
a9a08845 969 return EPOLLERR;
15b726ef
AA
970 /*
971 * lockless access to see if there are pending faults
972 * __pollwait last action is the add_wait_queue but
973 * the spin_unlock would allow the waitqueue_active to
974 * pass above the actual list_add inside
975 * add_wait_queue critical section. So use a full
976 * memory barrier to serialize the list_add write of
977 * add_wait_queue() with the waitqueue_active read
978 * below.
979 */
980 ret = 0;
981 smp_mb();
982 if (waitqueue_active(&ctx->fault_pending_wqh))
a9a08845 983 ret = EPOLLIN;
9cd75c3c 984 else if (waitqueue_active(&ctx->event_wqh))
a9a08845 985 ret = EPOLLIN;
9cd75c3c 986
86039bd3
AA
987 return ret;
988 default:
8474901a 989 WARN_ON_ONCE(1);
a9a08845 990 return EPOLLERR;
86039bd3
AA
991 }
992}
993
893e26e6
PE
994static const struct file_operations userfaultfd_fops;
995
996static int resolve_userfault_fork(struct userfaultfd_ctx *ctx,
997 struct userfaultfd_ctx *new,
998 struct uffd_msg *msg)
999{
1000 int fd;
893e26e6 1001
284cd241
EB
1002 fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, new,
1003 O_RDWR | (new->flags & UFFD_SHARED_FCNTL_FLAGS));
893e26e6
PE
1004 if (fd < 0)
1005 return fd;
1006
893e26e6
PE
1007 msg->arg.reserved.reserved1 = 0;
1008 msg->arg.fork.ufd = fd;
893e26e6
PE
1009 return 0;
1010}
1011
86039bd3 1012static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
a9b85f94 1013 struct uffd_msg *msg)
86039bd3
AA
1014{
1015 ssize_t ret;
1016 DECLARE_WAITQUEUE(wait, current);
15b726ef 1017 struct userfaultfd_wait_queue *uwq;
893e26e6
PE
1018 /*
1019 * Handling fork event requires sleeping operations, so
1020 * we drop the event_wqh lock, then do these ops, then
1021 * lock it back and wake up the waiter. While the lock is
1022 * dropped the ewq may go away so we keep track of it
1023 * carefully.
1024 */
1025 LIST_HEAD(fork_event);
1026 struct userfaultfd_ctx *fork_nctx = NULL;
86039bd3 1027
15b726ef 1028 /* always take the fd_wqh lock before the fault_pending_wqh lock */
86039bd3
AA
1029 spin_lock(&ctx->fd_wqh.lock);
1030 __add_wait_queue(&ctx->fd_wqh, &wait);
1031 for (;;) {
1032 set_current_state(TASK_INTERRUPTIBLE);
15b726ef
AA
1033 spin_lock(&ctx->fault_pending_wqh.lock);
1034 uwq = find_userfault(ctx);
1035 if (uwq) {
2c5b7e1b
AA
1036 /*
1037 * Use a seqcount to repeat the lockless check
1038 * in wake_userfault() to avoid missing
1039 * wakeups because during the refile both
1040 * waitqueue could become empty if this is the
1041 * only userfault.
1042 */
1043 write_seqcount_begin(&ctx->refile_seq);
1044
86039bd3 1045 /*
15b726ef
AA
1046 * The fault_pending_wqh.lock prevents the uwq
1047 * to disappear from under us.
1048 *
1049 * Refile this userfault from
1050 * fault_pending_wqh to fault_wqh, it's not
1051 * pending anymore after we read it.
1052 *
1053 * Use list_del() by hand (as
1054 * userfaultfd_wake_function also uses
1055 * list_del_init() by hand) to be sure nobody
1056 * changes __remove_wait_queue() to use
1057 * list_del_init() in turn breaking the
1058 * !list_empty_careful() check in
2055da97 1059 * handle_userfault(). The uwq->wq.head list
15b726ef
AA
1060 * must never be empty at any time during the
1061 * refile, or the waitqueue could disappear
1062 * from under us. The "wait_queue_head_t"
1063 * parameter of __remove_wait_queue() is unused
1064 * anyway.
86039bd3 1065 */
2055da97 1066 list_del(&uwq->wq.entry);
c430d1e8 1067 add_wait_queue(&ctx->fault_wqh, &uwq->wq);
15b726ef 1068
2c5b7e1b
AA
1069 write_seqcount_end(&ctx->refile_seq);
1070
a9b85f94
AA
1071 /* careful to always initialize msg if ret == 0 */
1072 *msg = uwq->msg;
15b726ef 1073 spin_unlock(&ctx->fault_pending_wqh.lock);
86039bd3
AA
1074 ret = 0;
1075 break;
1076 }
15b726ef 1077 spin_unlock(&ctx->fault_pending_wqh.lock);
9cd75c3c
PE
1078
1079 spin_lock(&ctx->event_wqh.lock);
1080 uwq = find_userfault_evt(ctx);
1081 if (uwq) {
1082 *msg = uwq->msg;
1083
893e26e6
PE
1084 if (uwq->msg.event == UFFD_EVENT_FORK) {
1085 fork_nctx = (struct userfaultfd_ctx *)
1086 (unsigned long)
1087 uwq->msg.arg.reserved.reserved1;
2055da97 1088 list_move(&uwq->wq.entry, &fork_event);
384632e6
AA
1089 /*
1090 * fork_nctx can be freed as soon as
1091 * we drop the lock, unless we take a
1092 * reference on it.
1093 */
1094 userfaultfd_ctx_get(fork_nctx);
893e26e6
PE
1095 spin_unlock(&ctx->event_wqh.lock);
1096 ret = 0;
1097 break;
1098 }
1099
9cd75c3c
PE
1100 userfaultfd_event_complete(ctx, uwq);
1101 spin_unlock(&ctx->event_wqh.lock);
1102 ret = 0;
1103 break;
1104 }
1105 spin_unlock(&ctx->event_wqh.lock);
1106
86039bd3
AA
1107 if (signal_pending(current)) {
1108 ret = -ERESTARTSYS;
1109 break;
1110 }
1111 if (no_wait) {
1112 ret = -EAGAIN;
1113 break;
1114 }
1115 spin_unlock(&ctx->fd_wqh.lock);
1116 schedule();
1117 spin_lock(&ctx->fd_wqh.lock);
1118 }
1119 __remove_wait_queue(&ctx->fd_wqh, &wait);
1120 __set_current_state(TASK_RUNNING);
1121 spin_unlock(&ctx->fd_wqh.lock);
1122
893e26e6
PE
1123 if (!ret && msg->event == UFFD_EVENT_FORK) {
1124 ret = resolve_userfault_fork(ctx, fork_nctx, msg);
384632e6
AA
1125 spin_lock(&ctx->event_wqh.lock);
1126 if (!list_empty(&fork_event)) {
1127 /*
1128 * The fork thread didn't abort, so we can
1129 * drop the temporary refcount.
1130 */
1131 userfaultfd_ctx_put(fork_nctx);
1132
1133 uwq = list_first_entry(&fork_event,
1134 typeof(*uwq),
1135 wq.entry);
1136 /*
1137 * If fork_event list wasn't empty and in turn
1138 * the event wasn't already released by fork
1139 * (the event is allocated on fork kernel
1140 * stack), put the event back to its place in
1141 * the event_wq. fork_event head will be freed
1142 * as soon as we return so the event cannot
1143 * stay queued there no matter the current
1144 * "ret" value.
1145 */
1146 list_del(&uwq->wq.entry);
1147 __add_wait_queue(&ctx->event_wqh, &uwq->wq);
893e26e6 1148
384632e6
AA
1149 /*
1150 * Leave the event in the waitqueue and report
1151 * error to userland if we failed to resolve
1152 * the userfault fork.
1153 */
1154 if (likely(!ret))
893e26e6 1155 userfaultfd_event_complete(ctx, uwq);
384632e6
AA
1156 } else {
1157 /*
1158 * Here the fork thread aborted and the
1159 * refcount from the fork thread on fork_nctx
1160 * has already been released. We still hold
1161 * the reference we took before releasing the
1162 * lock above. If resolve_userfault_fork
1163 * failed we've to drop it because the
1164 * fork_nctx has to be freed in such case. If
1165 * it succeeded we'll hold it because the new
1166 * uffd references it.
1167 */
1168 if (ret)
1169 userfaultfd_ctx_put(fork_nctx);
893e26e6 1170 }
384632e6 1171 spin_unlock(&ctx->event_wqh.lock);
893e26e6
PE
1172 }
1173
86039bd3
AA
1174 return ret;
1175}
1176
1177static ssize_t userfaultfd_read(struct file *file, char __user *buf,
1178 size_t count, loff_t *ppos)
1179{
1180 struct userfaultfd_ctx *ctx = file->private_data;
1181 ssize_t _ret, ret = 0;
a9b85f94 1182 struct uffd_msg msg;
86039bd3
AA
1183 int no_wait = file->f_flags & O_NONBLOCK;
1184
1185 if (ctx->state == UFFD_STATE_WAIT_API)
1186 return -EINVAL;
86039bd3
AA
1187
1188 for (;;) {
a9b85f94 1189 if (count < sizeof(msg))
86039bd3 1190 return ret ? ret : -EINVAL;
a9b85f94 1191 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg);
86039bd3
AA
1192 if (_ret < 0)
1193 return ret ? ret : _ret;
a9b85f94 1194 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
86039bd3 1195 return ret ? ret : -EFAULT;
a9b85f94
AA
1196 ret += sizeof(msg);
1197 buf += sizeof(msg);
1198 count -= sizeof(msg);
86039bd3
AA
1199 /*
1200 * Allow to read more than one fault at time but only
1201 * block if waiting for the very first one.
1202 */
1203 no_wait = O_NONBLOCK;
1204 }
1205}
1206
1207static void __wake_userfault(struct userfaultfd_ctx *ctx,
1208 struct userfaultfd_wake_range *range)
1209{
15b726ef 1210 spin_lock(&ctx->fault_pending_wqh.lock);
86039bd3 1211 /* wake all in the range and autoremove */
15b726ef 1212 if (waitqueue_active(&ctx->fault_pending_wqh))
ac5be6b4 1213 __wake_up_locked_key(&ctx->fault_pending_wqh, TASK_NORMAL,
15b726ef
AA
1214 range);
1215 if (waitqueue_active(&ctx->fault_wqh))
c430d1e8 1216 __wake_up(&ctx->fault_wqh, TASK_NORMAL, 1, range);
15b726ef 1217 spin_unlock(&ctx->fault_pending_wqh.lock);
86039bd3
AA
1218}
1219
1220static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
1221 struct userfaultfd_wake_range *range)
1222{
2c5b7e1b
AA
1223 unsigned seq;
1224 bool need_wakeup;
1225
86039bd3
AA
1226 /*
1227 * To be sure waitqueue_active() is not reordered by the CPU
1228 * before the pagetable update, use an explicit SMP memory
1229 * barrier here. PT lock release or up_read(mmap_sem) still
1230 * have release semantics that can allow the
1231 * waitqueue_active() to be reordered before the pte update.
1232 */
1233 smp_mb();
1234
1235 /*
1236 * Use waitqueue_active because it's very frequent to
1237 * change the address space atomically even if there are no
1238 * userfaults yet. So we take the spinlock only when we're
1239 * sure we've userfaults to wake.
1240 */
2c5b7e1b
AA
1241 do {
1242 seq = read_seqcount_begin(&ctx->refile_seq);
1243 need_wakeup = waitqueue_active(&ctx->fault_pending_wqh) ||
1244 waitqueue_active(&ctx->fault_wqh);
1245 cond_resched();
1246 } while (read_seqcount_retry(&ctx->refile_seq, seq));
1247 if (need_wakeup)
86039bd3
AA
1248 __wake_userfault(ctx, range);
1249}
1250
1251static __always_inline int validate_range(struct mm_struct *mm,
1252 __u64 start, __u64 len)
1253{
1254 __u64 task_size = mm->task_size;
1255
1256 if (start & ~PAGE_MASK)
1257 return -EINVAL;
1258 if (len & ~PAGE_MASK)
1259 return -EINVAL;
1260 if (!len)
1261 return -EINVAL;
1262 if (start < mmap_min_addr)
1263 return -EINVAL;
1264 if (start >= task_size)
1265 return -EINVAL;
1266 if (len > task_size - start)
1267 return -EINVAL;
1268 return 0;
1269}
1270
ba6907db
MR
1271static inline bool vma_can_userfault(struct vm_area_struct *vma)
1272{
cac67329
MR
1273 return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
1274 vma_is_shmem(vma);
ba6907db
MR
1275}
1276
86039bd3
AA
1277static int userfaultfd_register(struct userfaultfd_ctx *ctx,
1278 unsigned long arg)
1279{
1280 struct mm_struct *mm = ctx->mm;
1281 struct vm_area_struct *vma, *prev, *cur;
1282 int ret;
1283 struct uffdio_register uffdio_register;
1284 struct uffdio_register __user *user_uffdio_register;
1285 unsigned long vm_flags, new_flags;
1286 bool found;
ce53e8e6 1287 bool basic_ioctls;
86039bd3
AA
1288 unsigned long start, end, vma_end;
1289
1290 user_uffdio_register = (struct uffdio_register __user *) arg;
1291
1292 ret = -EFAULT;
1293 if (copy_from_user(&uffdio_register, user_uffdio_register,
1294 sizeof(uffdio_register)-sizeof(__u64)))
1295 goto out;
1296
1297 ret = -EINVAL;
1298 if (!uffdio_register.mode)
1299 goto out;
1300 if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
1301 UFFDIO_REGISTER_MODE_WP))
1302 goto out;
1303 vm_flags = 0;
1304 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
1305 vm_flags |= VM_UFFD_MISSING;
1306 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
1307 vm_flags |= VM_UFFD_WP;
1308 /*
1309 * FIXME: remove the below error constraint by
1310 * implementing the wprotect tracking mode.
1311 */
1312 ret = -EINVAL;
1313 goto out;
1314 }
1315
1316 ret = validate_range(mm, uffdio_register.range.start,
1317 uffdio_register.range.len);
1318 if (ret)
1319 goto out;
1320
1321 start = uffdio_register.range.start;
1322 end = start + uffdio_register.range.len;
1323
d2005e3f
ON
1324 ret = -ENOMEM;
1325 if (!mmget_not_zero(mm))
1326 goto out;
1327
86039bd3
AA
1328 down_write(&mm->mmap_sem);
1329 vma = find_vma_prev(mm, start, &prev);
86039bd3
AA
1330 if (!vma)
1331 goto out_unlock;
1332
1333 /* check that there's at least one vma in the range */
1334 ret = -EINVAL;
1335 if (vma->vm_start >= end)
1336 goto out_unlock;
1337
cab350af
MK
1338 /*
1339 * If the first vma contains huge pages, make sure start address
1340 * is aligned to huge page size.
1341 */
1342 if (is_vm_hugetlb_page(vma)) {
1343 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1344
1345 if (start & (vma_hpagesize - 1))
1346 goto out_unlock;
1347 }
1348
86039bd3
AA
1349 /*
1350 * Search for not compatible vmas.
86039bd3
AA
1351 */
1352 found = false;
ce53e8e6 1353 basic_ioctls = false;
86039bd3
AA
1354 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1355 cond_resched();
1356
1357 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1358 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1359
1360 /* check not compatible vmas */
1361 ret = -EINVAL;
ba6907db 1362 if (!vma_can_userfault(cur))
86039bd3 1363 goto out_unlock;
cab350af
MK
1364 /*
1365 * If this vma contains ending address, and huge pages
1366 * check alignment.
1367 */
1368 if (is_vm_hugetlb_page(cur) && end <= cur->vm_end &&
1369 end > cur->vm_start) {
1370 unsigned long vma_hpagesize = vma_kernel_pagesize(cur);
1371
1372 ret = -EINVAL;
1373
1374 if (end & (vma_hpagesize - 1))
1375 goto out_unlock;
1376 }
86039bd3
AA
1377
1378 /*
1379 * Check that this vma isn't already owned by a
1380 * different userfaultfd. We can't allow more than one
1381 * userfaultfd to own a single vma simultaneously or we
1382 * wouldn't know which one to deliver the userfaults to.
1383 */
1384 ret = -EBUSY;
1385 if (cur->vm_userfaultfd_ctx.ctx &&
1386 cur->vm_userfaultfd_ctx.ctx != ctx)
1387 goto out_unlock;
1388
cab350af
MK
1389 /*
1390 * Note vmas containing huge pages
1391 */
ce53e8e6
MR
1392 if (is_vm_hugetlb_page(cur))
1393 basic_ioctls = true;
cab350af 1394
86039bd3
AA
1395 found = true;
1396 }
1397 BUG_ON(!found);
1398
1399 if (vma->vm_start < start)
1400 prev = vma;
1401
1402 ret = 0;
1403 do {
1404 cond_resched();
1405
ba6907db 1406 BUG_ON(!vma_can_userfault(vma));
86039bd3
AA
1407 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
1408 vma->vm_userfaultfd_ctx.ctx != ctx);
1409
1410 /*
1411 * Nothing to do: this vma is already registered into this
1412 * userfaultfd and with the right tracking mode too.
1413 */
1414 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
1415 (vma->vm_flags & vm_flags) == vm_flags)
1416 goto skip;
1417
1418 if (vma->vm_start > start)
1419 start = vma->vm_start;
1420 vma_end = min(end, vma->vm_end);
1421
1422 new_flags = (vma->vm_flags & ~vm_flags) | vm_flags;
1423 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1424 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1425 vma_policy(vma),
1426 ((struct vm_userfaultfd_ctx){ ctx }));
1427 if (prev) {
1428 vma = prev;
1429 goto next;
1430 }
1431 if (vma->vm_start < start) {
1432 ret = split_vma(mm, vma, start, 1);
1433 if (ret)
1434 break;
1435 }
1436 if (vma->vm_end > end) {
1437 ret = split_vma(mm, vma, end, 0);
1438 if (ret)
1439 break;
1440 }
1441 next:
1442 /*
1443 * In the vma_merge() successful mprotect-like case 8:
1444 * the next vma was merged into the current one and
1445 * the current one has not been updated yet.
1446 */
1447 vma->vm_flags = new_flags;
1448 vma->vm_userfaultfd_ctx.ctx = ctx;
1449
1450 skip:
1451 prev = vma;
1452 start = vma->vm_end;
1453 vma = vma->vm_next;
1454 } while (vma && vma->vm_start < end);
1455out_unlock:
1456 up_write(&mm->mmap_sem);
d2005e3f 1457 mmput(mm);
86039bd3
AA
1458 if (!ret) {
1459 /*
1460 * Now that we scanned all vmas we can already tell
1461 * userland which ioctls methods are guaranteed to
1462 * succeed on this range.
1463 */
ce53e8e6 1464 if (put_user(basic_ioctls ? UFFD_API_RANGE_IOCTLS_BASIC :
cab350af 1465 UFFD_API_RANGE_IOCTLS,
86039bd3
AA
1466 &user_uffdio_register->ioctls))
1467 ret = -EFAULT;
1468 }
1469out:
1470 return ret;
1471}
1472
1473static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
1474 unsigned long arg)
1475{
1476 struct mm_struct *mm = ctx->mm;
1477 struct vm_area_struct *vma, *prev, *cur;
1478 int ret;
1479 struct uffdio_range uffdio_unregister;
1480 unsigned long new_flags;
1481 bool found;
1482 unsigned long start, end, vma_end;
1483 const void __user *buf = (void __user *)arg;
1484
1485 ret = -EFAULT;
1486 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
1487 goto out;
1488
1489 ret = validate_range(mm, uffdio_unregister.start,
1490 uffdio_unregister.len);
1491 if (ret)
1492 goto out;
1493
1494 start = uffdio_unregister.start;
1495 end = start + uffdio_unregister.len;
1496
d2005e3f
ON
1497 ret = -ENOMEM;
1498 if (!mmget_not_zero(mm))
1499 goto out;
1500
86039bd3
AA
1501 down_write(&mm->mmap_sem);
1502 vma = find_vma_prev(mm, start, &prev);
86039bd3
AA
1503 if (!vma)
1504 goto out_unlock;
1505
1506 /* check that there's at least one vma in the range */
1507 ret = -EINVAL;
1508 if (vma->vm_start >= end)
1509 goto out_unlock;
1510
cab350af
MK
1511 /*
1512 * If the first vma contains huge pages, make sure start address
1513 * is aligned to huge page size.
1514 */
1515 if (is_vm_hugetlb_page(vma)) {
1516 unsigned long vma_hpagesize = vma_kernel_pagesize(vma);
1517
1518 if (start & (vma_hpagesize - 1))
1519 goto out_unlock;
1520 }
1521
86039bd3
AA
1522 /*
1523 * Search for not compatible vmas.
86039bd3
AA
1524 */
1525 found = false;
1526 ret = -EINVAL;
1527 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
1528 cond_resched();
1529
1530 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
1531 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
1532
1533 /*
1534 * Check not compatible vmas, not strictly required
1535 * here as not compatible vmas cannot have an
1536 * userfaultfd_ctx registered on them, but this
1537 * provides for more strict behavior to notice
1538 * unregistration errors.
1539 */
ba6907db 1540 if (!vma_can_userfault(cur))
86039bd3
AA
1541 goto out_unlock;
1542
1543 found = true;
1544 }
1545 BUG_ON(!found);
1546
1547 if (vma->vm_start < start)
1548 prev = vma;
1549
1550 ret = 0;
1551 do {
1552 cond_resched();
1553
ba6907db 1554 BUG_ON(!vma_can_userfault(vma));
86039bd3
AA
1555
1556 /*
1557 * Nothing to do: this vma is already registered into this
1558 * userfaultfd and with the right tracking mode too.
1559 */
1560 if (!vma->vm_userfaultfd_ctx.ctx)
1561 goto skip;
1562
1563 if (vma->vm_start > start)
1564 start = vma->vm_start;
1565 vma_end = min(end, vma->vm_end);
1566
09fa5296
AA
1567 if (userfaultfd_missing(vma)) {
1568 /*
1569 * Wake any concurrent pending userfault while
1570 * we unregister, so they will not hang
1571 * permanently and it avoids userland to call
1572 * UFFDIO_WAKE explicitly.
1573 */
1574 struct userfaultfd_wake_range range;
1575 range.start = start;
1576 range.len = vma_end - start;
1577 wake_userfault(vma->vm_userfaultfd_ctx.ctx, &range);
1578 }
1579
86039bd3
AA
1580 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
1581 prev = vma_merge(mm, prev, start, vma_end, new_flags,
1582 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
1583 vma_policy(vma),
1584 NULL_VM_UFFD_CTX);
1585 if (prev) {
1586 vma = prev;
1587 goto next;
1588 }
1589 if (vma->vm_start < start) {
1590 ret = split_vma(mm, vma, start, 1);
1591 if (ret)
1592 break;
1593 }
1594 if (vma->vm_end > end) {
1595 ret = split_vma(mm, vma, end, 0);
1596 if (ret)
1597 break;
1598 }
1599 next:
1600 /*
1601 * In the vma_merge() successful mprotect-like case 8:
1602 * the next vma was merged into the current one and
1603 * the current one has not been updated yet.
1604 */
1605 vma->vm_flags = new_flags;
1606 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
1607
1608 skip:
1609 prev = vma;
1610 start = vma->vm_end;
1611 vma = vma->vm_next;
1612 } while (vma && vma->vm_start < end);
1613out_unlock:
1614 up_write(&mm->mmap_sem);
d2005e3f 1615 mmput(mm);
86039bd3
AA
1616out:
1617 return ret;
1618}
1619
1620/*
ba85c702
AA
1621 * userfaultfd_wake may be used in combination with the
1622 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches.
86039bd3
AA
1623 */
1624static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
1625 unsigned long arg)
1626{
1627 int ret;
1628 struct uffdio_range uffdio_wake;
1629 struct userfaultfd_wake_range range;
1630 const void __user *buf = (void __user *)arg;
1631
1632 ret = -EFAULT;
1633 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
1634 goto out;
1635
1636 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
1637 if (ret)
1638 goto out;
1639
1640 range.start = uffdio_wake.start;
1641 range.len = uffdio_wake.len;
1642
1643 /*
1644 * len == 0 means wake all and we don't want to wake all here,
1645 * so check it again to be sure.
1646 */
1647 VM_BUG_ON(!range.len);
1648
1649 wake_userfault(ctx, &range);
1650 ret = 0;
1651
1652out:
1653 return ret;
1654}
1655
ad465cae
AA
1656static int userfaultfd_copy(struct userfaultfd_ctx *ctx,
1657 unsigned long arg)
1658{
1659 __s64 ret;
1660 struct uffdio_copy uffdio_copy;
1661 struct uffdio_copy __user *user_uffdio_copy;
1662 struct userfaultfd_wake_range range;
1663
1664 user_uffdio_copy = (struct uffdio_copy __user *) arg;
1665
df2cc96e
MR
1666 ret = -EAGAIN;
1667 if (READ_ONCE(ctx->mmap_changing))
1668 goto out;
1669
ad465cae
AA
1670 ret = -EFAULT;
1671 if (copy_from_user(&uffdio_copy, user_uffdio_copy,
1672 /* don't copy "copy" last field */
1673 sizeof(uffdio_copy)-sizeof(__s64)))
1674 goto out;
1675
1676 ret = validate_range(ctx->mm, uffdio_copy.dst, uffdio_copy.len);
1677 if (ret)
1678 goto out;
1679 /*
1680 * double check for wraparound just in case. copy_from_user()
1681 * will later check uffdio_copy.src + uffdio_copy.len to fit
1682 * in the userland range.
1683 */
1684 ret = -EINVAL;
1685 if (uffdio_copy.src + uffdio_copy.len <= uffdio_copy.src)
1686 goto out;
1687 if (uffdio_copy.mode & ~UFFDIO_COPY_MODE_DONTWAKE)
1688 goto out;
d2005e3f
ON
1689 if (mmget_not_zero(ctx->mm)) {
1690 ret = mcopy_atomic(ctx->mm, uffdio_copy.dst, uffdio_copy.src,
df2cc96e 1691 uffdio_copy.len, &ctx->mmap_changing);
d2005e3f 1692 mmput(ctx->mm);
96333187 1693 } else {
e86b298b 1694 return -ESRCH;
d2005e3f 1695 }
ad465cae
AA
1696 if (unlikely(put_user(ret, &user_uffdio_copy->copy)))
1697 return -EFAULT;
1698 if (ret < 0)
1699 goto out;
1700 BUG_ON(!ret);
1701 /* len == 0 would wake all */
1702 range.len = ret;
1703 if (!(uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE)) {
1704 range.start = uffdio_copy.dst;
1705 wake_userfault(ctx, &range);
1706 }
1707 ret = range.len == uffdio_copy.len ? 0 : -EAGAIN;
1708out:
1709 return ret;
1710}
1711
1712static int userfaultfd_zeropage(struct userfaultfd_ctx *ctx,
1713 unsigned long arg)
1714{
1715 __s64 ret;
1716 struct uffdio_zeropage uffdio_zeropage;
1717 struct uffdio_zeropage __user *user_uffdio_zeropage;
1718 struct userfaultfd_wake_range range;
1719
1720 user_uffdio_zeropage = (struct uffdio_zeropage __user *) arg;
1721
df2cc96e
MR
1722 ret = -EAGAIN;
1723 if (READ_ONCE(ctx->mmap_changing))
1724 goto out;
1725
ad465cae
AA
1726 ret = -EFAULT;
1727 if (copy_from_user(&uffdio_zeropage, user_uffdio_zeropage,
1728 /* don't copy "zeropage" last field */
1729 sizeof(uffdio_zeropage)-sizeof(__s64)))
1730 goto out;
1731
1732 ret = validate_range(ctx->mm, uffdio_zeropage.range.start,
1733 uffdio_zeropage.range.len);
1734 if (ret)
1735 goto out;
1736 ret = -EINVAL;
1737 if (uffdio_zeropage.mode & ~UFFDIO_ZEROPAGE_MODE_DONTWAKE)
1738 goto out;
1739
d2005e3f
ON
1740 if (mmget_not_zero(ctx->mm)) {
1741 ret = mfill_zeropage(ctx->mm, uffdio_zeropage.range.start,
df2cc96e
MR
1742 uffdio_zeropage.range.len,
1743 &ctx->mmap_changing);
d2005e3f 1744 mmput(ctx->mm);
9d95aa4b 1745 } else {
e86b298b 1746 return -ESRCH;
d2005e3f 1747 }
ad465cae
AA
1748 if (unlikely(put_user(ret, &user_uffdio_zeropage->zeropage)))
1749 return -EFAULT;
1750 if (ret < 0)
1751 goto out;
1752 /* len == 0 would wake all */
1753 BUG_ON(!ret);
1754 range.len = ret;
1755 if (!(uffdio_zeropage.mode & UFFDIO_ZEROPAGE_MODE_DONTWAKE)) {
1756 range.start = uffdio_zeropage.range.start;
1757 wake_userfault(ctx, &range);
1758 }
1759 ret = range.len == uffdio_zeropage.range.len ? 0 : -EAGAIN;
1760out:
1761 return ret;
1762}
1763
9cd75c3c
PE
1764static inline unsigned int uffd_ctx_features(__u64 user_features)
1765{
1766 /*
1767 * For the current set of features the bits just coincide
1768 */
1769 return (unsigned int)user_features;
1770}
1771
86039bd3
AA
1772/*
1773 * userland asks for a certain API version and we return which bits
1774 * and ioctl commands are implemented in this kernel for such API
1775 * version or -EINVAL if unknown.
1776 */
1777static int userfaultfd_api(struct userfaultfd_ctx *ctx,
1778 unsigned long arg)
1779{
1780 struct uffdio_api uffdio_api;
1781 void __user *buf = (void __user *)arg;
1782 int ret;
65603144 1783 __u64 features;
86039bd3
AA
1784
1785 ret = -EINVAL;
1786 if (ctx->state != UFFD_STATE_WAIT_API)
1787 goto out;
1788 ret = -EFAULT;
a9b85f94 1789 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
86039bd3 1790 goto out;
65603144
AA
1791 features = uffdio_api.features;
1792 if (uffdio_api.api != UFFD_API || (features & ~UFFD_API_FEATURES)) {
86039bd3
AA
1793 memset(&uffdio_api, 0, sizeof(uffdio_api));
1794 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1795 goto out;
1796 ret = -EINVAL;
1797 goto out;
1798 }
65603144
AA
1799 /* report all available features and ioctls to userland */
1800 uffdio_api.features = UFFD_API_FEATURES;
86039bd3
AA
1801 uffdio_api.ioctls = UFFD_API_IOCTLS;
1802 ret = -EFAULT;
1803 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
1804 goto out;
1805 ctx->state = UFFD_STATE_RUNNING;
65603144
AA
1806 /* only enable the requested features for this uffd context */
1807 ctx->features = uffd_ctx_features(features);
86039bd3
AA
1808 ret = 0;
1809out:
1810 return ret;
1811}
1812
1813static long userfaultfd_ioctl(struct file *file, unsigned cmd,
1814 unsigned long arg)
1815{
1816 int ret = -EINVAL;
1817 struct userfaultfd_ctx *ctx = file->private_data;
1818
e6485a47
AA
1819 if (cmd != UFFDIO_API && ctx->state == UFFD_STATE_WAIT_API)
1820 return -EINVAL;
1821
86039bd3
AA
1822 switch(cmd) {
1823 case UFFDIO_API:
1824 ret = userfaultfd_api(ctx, arg);
1825 break;
1826 case UFFDIO_REGISTER:
1827 ret = userfaultfd_register(ctx, arg);
1828 break;
1829 case UFFDIO_UNREGISTER:
1830 ret = userfaultfd_unregister(ctx, arg);
1831 break;
1832 case UFFDIO_WAKE:
1833 ret = userfaultfd_wake(ctx, arg);
1834 break;
ad465cae
AA
1835 case UFFDIO_COPY:
1836 ret = userfaultfd_copy(ctx, arg);
1837 break;
1838 case UFFDIO_ZEROPAGE:
1839 ret = userfaultfd_zeropage(ctx, arg);
1840 break;
86039bd3
AA
1841 }
1842 return ret;
1843}
1844
1845#ifdef CONFIG_PROC_FS
1846static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
1847{
1848 struct userfaultfd_ctx *ctx = f->private_data;
ac6424b9 1849 wait_queue_entry_t *wq;
86039bd3
AA
1850 unsigned long pending = 0, total = 0;
1851
15b726ef 1852 spin_lock(&ctx->fault_pending_wqh.lock);
2055da97 1853 list_for_each_entry(wq, &ctx->fault_pending_wqh.head, entry) {
15b726ef
AA
1854 pending++;
1855 total++;
1856 }
2055da97 1857 list_for_each_entry(wq, &ctx->fault_wqh.head, entry) {
86039bd3
AA
1858 total++;
1859 }
15b726ef 1860 spin_unlock(&ctx->fault_pending_wqh.lock);
86039bd3
AA
1861
1862 /*
1863 * If more protocols will be added, there will be all shown
1864 * separated by a space. Like this:
1865 * protocols: aa:... bb:...
1866 */
1867 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
045098e9 1868 pending, total, UFFD_API, ctx->features,
86039bd3
AA
1869 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
1870}
1871#endif
1872
1873static const struct file_operations userfaultfd_fops = {
1874#ifdef CONFIG_PROC_FS
1875 .show_fdinfo = userfaultfd_show_fdinfo,
1876#endif
1877 .release = userfaultfd_release,
1878 .poll = userfaultfd_poll,
1879 .read = userfaultfd_read,
1880 .unlocked_ioctl = userfaultfd_ioctl,
1881 .compat_ioctl = userfaultfd_ioctl,
1882 .llseek = noop_llseek,
1883};
1884
3004ec9c
AA
1885static void init_once_userfaultfd_ctx(void *mem)
1886{
1887 struct userfaultfd_ctx *ctx = (struct userfaultfd_ctx *) mem;
1888
1889 init_waitqueue_head(&ctx->fault_pending_wqh);
1890 init_waitqueue_head(&ctx->fault_wqh);
9cd75c3c 1891 init_waitqueue_head(&ctx->event_wqh);
3004ec9c 1892 init_waitqueue_head(&ctx->fd_wqh);
2c5b7e1b 1893 seqcount_init(&ctx->refile_seq);
3004ec9c
AA
1894}
1895
284cd241 1896SYSCALL_DEFINE1(userfaultfd, int, flags)
86039bd3 1897{
86039bd3 1898 struct userfaultfd_ctx *ctx;
284cd241 1899 int fd;
86039bd3
AA
1900
1901 BUG_ON(!current->mm);
1902
1903 /* Check the UFFD_* constants for consistency. */
1904 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
1905 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
1906
86039bd3 1907 if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
284cd241 1908 return -EINVAL;
86039bd3 1909
3004ec9c 1910 ctx = kmem_cache_alloc(userfaultfd_ctx_cachep, GFP_KERNEL);
86039bd3 1911 if (!ctx)
284cd241 1912 return -ENOMEM;
86039bd3
AA
1913
1914 atomic_set(&ctx->refcount, 1);
86039bd3 1915 ctx->flags = flags;
9cd75c3c 1916 ctx->features = 0;
86039bd3
AA
1917 ctx->state = UFFD_STATE_WAIT_API;
1918 ctx->released = false;
df2cc96e 1919 ctx->mmap_changing = false;
86039bd3
AA
1920 ctx->mm = current->mm;
1921 /* prevent the mm struct to be freed */
f1f10076 1922 mmgrab(ctx->mm);
86039bd3 1923
284cd241
EB
1924 fd = anon_inode_getfd("[userfaultfd]", &userfaultfd_fops, ctx,
1925 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
1926 if (fd < 0) {
d2005e3f 1927 mmdrop(ctx->mm);
3004ec9c 1928 kmem_cache_free(userfaultfd_ctx_cachep, ctx);
c03e946f 1929 }
86039bd3 1930 return fd;
86039bd3 1931}
3004ec9c
AA
1932
1933static int __init userfaultfd_init(void)
1934{
1935 userfaultfd_ctx_cachep = kmem_cache_create("userfaultfd_ctx_cache",
1936 sizeof(struct userfaultfd_ctx),
1937 0,
1938 SLAB_HWCACHE_ALIGN|SLAB_PANIC,
1939 init_once_userfaultfd_ctx);
1940 return 0;
1941}
1942__initcall(userfaultfd_init);