4 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
5 * Copyright (C) 2008-2009 Red Hat, Inc.
6 * Copyright (C) 2015 Red Hat, Inc.
8 * This work is licensed under the terms of the GNU GPL, version 2. See
9 * the COPYING file in the top-level directory.
11 * Some part derived from fs/eventfd.c (anon inode setup) and
12 * mm/ksm.c (mm hashing).
15 #include <linux/hashtable.h>
16 #include <linux/sched.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>
30 enum userfaultfd_state {
35 struct userfaultfd_ctx {
36 /* pseudo fd refcounting */
38 /* waitqueue head for the userfaultfd page faults */
39 wait_queue_head_t fault_wqh;
40 /* waitqueue head for the pseudo fd to wakeup poll/read */
41 wait_queue_head_t fd_wqh;
42 /* userfaultfd syscall flags */
45 enum userfaultfd_state state;
48 /* mm with one ore more vmas attached to this userfaultfd_ctx */
52 struct userfaultfd_wait_queue {
56 * Only relevant when queued in fault_wqh and only used by the
57 * read operation to avoid reading the same userfault twice.
60 struct userfaultfd_ctx *ctx;
63 struct userfaultfd_wake_range {
68 static int userfaultfd_wake_function(wait_queue_t *wq, unsigned mode,
69 int wake_flags, void *key)
71 struct userfaultfd_wake_range *range = key;
73 struct userfaultfd_wait_queue *uwq;
74 unsigned long start, len;
76 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
78 /* len == 0 means wake all */
81 if (len && (start > uwq->msg.arg.pagefault.address ||
82 start + len <= uwq->msg.arg.pagefault.address))
84 ret = wake_up_state(wq->private, mode);
87 * Wake only once, autoremove behavior.
89 * After the effect of list_del_init is visible to the
90 * other CPUs, the waitqueue may disappear from under
91 * us, see the !list_empty_careful() in
92 * handle_userfault(). try_to_wake_up() has an
93 * implicit smp_mb__before_spinlock, and the
94 * wq->private is read before calling the extern
95 * function "wake_up_state" (which in turns calls
96 * try_to_wake_up). While the spin_lock;spin_unlock;
97 * wouldn't be enough, the smp_mb__before_spinlock is
98 * enough to avoid an explicit smp_mb() here.
100 list_del_init(&wq->task_list);
106 * userfaultfd_ctx_get - Acquires a reference to the internal userfaultfd
108 * @ctx: [in] Pointer to the userfaultfd context.
110 * Returns: In case of success, returns not zero.
112 static void userfaultfd_ctx_get(struct userfaultfd_ctx *ctx)
114 if (!atomic_inc_not_zero(&ctx->refcount))
119 * userfaultfd_ctx_put - Releases a reference to the internal userfaultfd
121 * @ctx: [in] Pointer to userfaultfd context.
123 * The userfaultfd context reference must have been previously acquired either
124 * with userfaultfd_ctx_get() or userfaultfd_ctx_fdget().
126 static void userfaultfd_ctx_put(struct userfaultfd_ctx *ctx)
128 if (atomic_dec_and_test(&ctx->refcount)) {
129 VM_BUG_ON(spin_is_locked(&ctx->fault_pending_wqh.lock));
130 VM_BUG_ON(waitqueue_active(&ctx->fault_pending_wqh));
131 VM_BUG_ON(spin_is_locked(&ctx->fault_wqh.lock));
132 VM_BUG_ON(waitqueue_active(&ctx->fault_wqh));
133 VM_BUG_ON(spin_is_locked(&ctx->fd_wqh.lock));
134 VM_BUG_ON(waitqueue_active(&ctx->fd_wqh));
140 static inline void msg_init(struct uffd_msg *msg)
142 BUILD_BUG_ON(sizeof(struct uffd_msg) != 32);
144 * Must use memset to zero out the paddings or kernel data is
145 * leaked to userland.
147 memset(msg, 0, sizeof(struct uffd_msg));
150 static inline struct uffd_msg userfault_msg(unsigned long address,
152 unsigned long reason)
156 msg.event = UFFD_EVENT_PAGEFAULT;
157 msg.arg.pagefault.address = address;
158 if (flags & FAULT_FLAG_WRITE)
160 * If UFFD_FEATURE_PAGEFAULT_FLAG_WRITE was set in the
161 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WRITE
162 * was not set in a UFFD_EVENT_PAGEFAULT, it means it
163 * was a read fault, otherwise if set it means it's
166 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WRITE;
167 if (reason & VM_UFFD_WP)
169 * If UFFD_FEATURE_PAGEFAULT_FLAG_WP was set in the
170 * uffdio_api.features and UFFD_PAGEFAULT_FLAG_WP was
171 * not set in a UFFD_EVENT_PAGEFAULT, it means it was
172 * a missing fault, otherwise if set it means it's a
173 * write protect fault.
175 msg.arg.pagefault.flags |= UFFD_PAGEFAULT_FLAG_WP;
180 * The locking rules involved in returning VM_FAULT_RETRY depending on
181 * FAULT_FLAG_ALLOW_RETRY, FAULT_FLAG_RETRY_NOWAIT and
182 * FAULT_FLAG_KILLABLE are not straightforward. The "Caution"
183 * recommendation in __lock_page_or_retry is not an understatement.
185 * If FAULT_FLAG_ALLOW_RETRY is set, the mmap_sem must be released
186 * before returning VM_FAULT_RETRY only if FAULT_FLAG_RETRY_NOWAIT is
189 * If FAULT_FLAG_ALLOW_RETRY is set but FAULT_FLAG_KILLABLE is not
190 * set, VM_FAULT_RETRY can still be returned if and only if there are
191 * fatal_signal_pending()s, and the mmap_sem must be released before
194 int handle_userfault(struct vm_area_struct *vma, unsigned long address,
195 unsigned int flags, unsigned long reason)
197 struct mm_struct *mm = vma->vm_mm;
198 struct userfaultfd_ctx *ctx;
199 struct userfaultfd_wait_queue uwq;
202 BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
204 ret = VM_FAULT_SIGBUS;
205 ctx = vma->vm_userfaultfd_ctx.ctx;
209 BUG_ON(ctx->mm != mm);
211 VM_BUG_ON(reason & ~(VM_UFFD_MISSING|VM_UFFD_WP));
212 VM_BUG_ON(!(reason & VM_UFFD_MISSING) ^ !!(reason & VM_UFFD_WP));
215 * If it's already released don't get it. This avoids to loop
216 * in __get_user_pages if userfaultfd_release waits on the
217 * caller of handle_userfault to release the mmap_sem.
219 if (unlikely(ACCESS_ONCE(ctx->released)))
223 * Check that we can return VM_FAULT_RETRY.
225 * NOTE: it should become possible to return VM_FAULT_RETRY
226 * even if FAULT_FLAG_TRIED is set without leading to gup()
227 * -EBUSY failures, if the userfaultfd is to be extended for
228 * VM_UFFD_WP tracking and we intend to arm the userfault
229 * without first stopping userland access to the memory. For
230 * VM_UFFD_MISSING userfaults this is enough for now.
232 if (unlikely(!(flags & FAULT_FLAG_ALLOW_RETRY))) {
234 * Validate the invariant that nowait must allow retry
235 * to be sure not to return SIGBUS erroneously on
236 * nowait invocations.
238 BUG_ON(flags & FAULT_FLAG_RETRY_NOWAIT);
239 #ifdef CONFIG_DEBUG_VM
240 if (printk_ratelimit()) {
242 "FAULT_FLAG_ALLOW_RETRY missing %x\n", flags);
250 * Handle nowait, not much to do other than tell it to retry
253 ret = VM_FAULT_RETRY;
254 if (flags & FAULT_FLAG_RETRY_NOWAIT)
257 /* take the reference before dropping the mmap_sem */
258 userfaultfd_ctx_get(ctx);
260 /* be gentle and immediately relinquish the mmap_sem */
261 up_read(&mm->mmap_sem);
263 init_waitqueue_func_entry(&uwq.wq, userfaultfd_wake_function);
264 uwq.wq.private = current;
265 uwq.msg = userfault_msg(address, flags, reason);
269 spin_lock(&ctx->fault_wqh.lock);
271 * After the __add_wait_queue the uwq is visible to userland
272 * through poll/read().
274 __add_wait_queue(&ctx->fault_wqh, &uwq.wq);
275 set_current_state(TASK_KILLABLE);
276 spin_unlock(&ctx->fault_wqh.lock);
278 if (likely(!ACCESS_ONCE(ctx->released) &&
279 !fatal_signal_pending(current))) {
280 wake_up_poll(&ctx->fd_wqh, POLLIN);
282 ret |= VM_FAULT_MAJOR;
285 __set_current_state(TASK_RUNNING);
286 /* see finish_wait() comment for why list_empty_careful() */
287 if (!list_empty_careful(&uwq.wq.task_list)) {
288 spin_lock(&ctx->fault_wqh.lock);
289 list_del_init(&uwq.wq.task_list);
290 spin_unlock(&ctx->fault_wqh.lock);
294 * ctx may go away after this if the userfault pseudo fd is
297 userfaultfd_ctx_put(ctx);
303 static int userfaultfd_release(struct inode *inode, struct file *file)
305 struct userfaultfd_ctx *ctx = file->private_data;
306 struct mm_struct *mm = ctx->mm;
307 struct vm_area_struct *vma, *prev;
308 /* len == 0 means wake all */
309 struct userfaultfd_wake_range range = { .len = 0, };
310 unsigned long new_flags;
312 ACCESS_ONCE(ctx->released) = true;
315 * Flush page faults out of all CPUs. NOTE: all page faults
316 * must be retried without returning VM_FAULT_SIGBUS if
317 * userfaultfd_ctx_get() succeeds but vma->vma_userfault_ctx
318 * changes while handle_userfault released the mmap_sem. So
319 * it's critical that released is set to true (above), before
320 * taking the mmap_sem for writing.
322 down_write(&mm->mmap_sem);
324 for (vma = mm->mmap; vma; vma = vma->vm_next) {
326 BUG_ON(!!vma->vm_userfaultfd_ctx.ctx ^
327 !!(vma->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
328 if (vma->vm_userfaultfd_ctx.ctx != ctx) {
332 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
333 prev = vma_merge(mm, prev, vma->vm_start, vma->vm_end,
334 new_flags, vma->anon_vma,
335 vma->vm_file, vma->vm_pgoff,
342 vma->vm_flags = new_flags;
343 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
345 up_write(&mm->mmap_sem);
348 * After no new page faults can wait on this fault_wqh, flush
349 * the last page faults that may have been already waiting on
352 spin_lock(&ctx->fault_wqh.lock);
353 __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, 0, &range);
354 spin_unlock(&ctx->fault_wqh.lock);
356 wake_up_poll(&ctx->fd_wqh, POLLHUP);
357 userfaultfd_ctx_put(ctx);
361 /* fault_wqh.lock must be hold by the caller */
362 static inline unsigned int find_userfault(struct userfaultfd_ctx *ctx,
363 struct userfaultfd_wait_queue **uwq)
366 struct userfaultfd_wait_queue *_uwq;
367 unsigned int ret = 0;
369 VM_BUG_ON(!spin_is_locked(&ctx->fault_wqh.lock));
371 list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) {
372 _uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
377 * If there's at least a pending and
378 * we don't care which one it is,
379 * break immediately and leverage the
380 * efficiency of the LIFO walk.
384 * If we need to find which one was pending we
385 * keep walking until we find the first not
386 * pending one, so we read() them in FIFO order.
391 * break the loop at the first not pending
392 * one, there cannot be pending userfaults
393 * after the first not pending one, because
394 * all new pending ones are inserted at the
395 * head and we walk it in LIFO.
403 static unsigned int userfaultfd_poll(struct file *file, poll_table *wait)
405 struct userfaultfd_ctx *ctx = file->private_data;
408 poll_wait(file, &ctx->fd_wqh, wait);
410 switch (ctx->state) {
411 case UFFD_STATE_WAIT_API:
413 case UFFD_STATE_RUNNING:
415 * poll() never guarantees that read won't block.
416 * userfaults can be waken before they're read().
418 if (unlikely(!(file->f_flags & O_NONBLOCK)))
420 spin_lock(&ctx->fault_wqh.lock);
421 ret = find_userfault(ctx, NULL);
422 spin_unlock(&ctx->fault_wqh.lock);
429 static ssize_t userfaultfd_ctx_read(struct userfaultfd_ctx *ctx, int no_wait,
430 struct uffd_msg *msg)
433 DECLARE_WAITQUEUE(wait, current);
434 struct userfaultfd_wait_queue *uwq = NULL;
436 /* always take the fd_wqh lock before the fault_wqh lock */
437 spin_lock(&ctx->fd_wqh.lock);
438 __add_wait_queue(&ctx->fd_wqh, &wait);
440 set_current_state(TASK_INTERRUPTIBLE);
441 spin_lock(&ctx->fault_wqh.lock);
442 if (find_userfault(ctx, &uwq)) {
444 * The fault_wqh.lock prevents the uwq to
445 * disappear from under us.
447 uwq->pending = false;
448 /* careful to always initialize msg if ret == 0 */
450 spin_unlock(&ctx->fault_wqh.lock);
454 spin_unlock(&ctx->fault_wqh.lock);
455 if (signal_pending(current)) {
463 spin_unlock(&ctx->fd_wqh.lock);
465 spin_lock(&ctx->fd_wqh.lock);
467 __remove_wait_queue(&ctx->fd_wqh, &wait);
468 __set_current_state(TASK_RUNNING);
469 spin_unlock(&ctx->fd_wqh.lock);
474 static ssize_t userfaultfd_read(struct file *file, char __user *buf,
475 size_t count, loff_t *ppos)
477 struct userfaultfd_ctx *ctx = file->private_data;
478 ssize_t _ret, ret = 0;
480 int no_wait = file->f_flags & O_NONBLOCK;
482 if (ctx->state == UFFD_STATE_WAIT_API)
484 BUG_ON(ctx->state != UFFD_STATE_RUNNING);
487 if (count < sizeof(msg))
488 return ret ? ret : -EINVAL;
489 _ret = userfaultfd_ctx_read(ctx, no_wait, &msg);
491 return ret ? ret : _ret;
492 if (copy_to_user((__u64 __user *) buf, &msg, sizeof(msg)))
493 return ret ? ret : -EFAULT;
496 count -= sizeof(msg);
498 * Allow to read more than one fault at time but only
499 * block if waiting for the very first one.
501 no_wait = O_NONBLOCK;
505 static void __wake_userfault(struct userfaultfd_ctx *ctx,
506 struct userfaultfd_wake_range *range)
508 unsigned long start, end;
510 start = range->start;
511 end = range->start + range->len;
513 spin_lock(&ctx->fault_wqh.lock);
514 /* wake all in the range and autoremove */
515 __wake_up_locked_key(&ctx->fault_wqh, TASK_NORMAL, 0, range);
516 spin_unlock(&ctx->fault_wqh.lock);
519 static __always_inline void wake_userfault(struct userfaultfd_ctx *ctx,
520 struct userfaultfd_wake_range *range)
523 * To be sure waitqueue_active() is not reordered by the CPU
524 * before the pagetable update, use an explicit SMP memory
525 * barrier here. PT lock release or up_read(mmap_sem) still
526 * have release semantics that can allow the
527 * waitqueue_active() to be reordered before the pte update.
532 * Use waitqueue_active because it's very frequent to
533 * change the address space atomically even if there are no
534 * userfaults yet. So we take the spinlock only when we're
535 * sure we've userfaults to wake.
537 if (waitqueue_active(&ctx->fault_wqh))
538 __wake_userfault(ctx, range);
541 static __always_inline int validate_range(struct mm_struct *mm,
542 __u64 start, __u64 len)
544 __u64 task_size = mm->task_size;
546 if (start & ~PAGE_MASK)
548 if (len & ~PAGE_MASK)
552 if (start < mmap_min_addr)
554 if (start >= task_size)
556 if (len > task_size - start)
561 static int userfaultfd_register(struct userfaultfd_ctx *ctx,
564 struct mm_struct *mm = ctx->mm;
565 struct vm_area_struct *vma, *prev, *cur;
567 struct uffdio_register uffdio_register;
568 struct uffdio_register __user *user_uffdio_register;
569 unsigned long vm_flags, new_flags;
571 unsigned long start, end, vma_end;
573 user_uffdio_register = (struct uffdio_register __user *) arg;
576 if (copy_from_user(&uffdio_register, user_uffdio_register,
577 sizeof(uffdio_register)-sizeof(__u64)))
581 if (!uffdio_register.mode)
583 if (uffdio_register.mode & ~(UFFDIO_REGISTER_MODE_MISSING|
584 UFFDIO_REGISTER_MODE_WP))
587 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_MISSING)
588 vm_flags |= VM_UFFD_MISSING;
589 if (uffdio_register.mode & UFFDIO_REGISTER_MODE_WP) {
590 vm_flags |= VM_UFFD_WP;
592 * FIXME: remove the below error constraint by
593 * implementing the wprotect tracking mode.
599 ret = validate_range(mm, uffdio_register.range.start,
600 uffdio_register.range.len);
604 start = uffdio_register.range.start;
605 end = start + uffdio_register.range.len;
607 down_write(&mm->mmap_sem);
608 vma = find_vma_prev(mm, start, &prev);
614 /* check that there's at least one vma in the range */
616 if (vma->vm_start >= end)
620 * Search for not compatible vmas.
622 * FIXME: this shall be relaxed later so that it doesn't fail
623 * on tmpfs backed vmas (in addition to the current allowance
624 * on anonymous vmas).
627 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
630 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
631 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
633 /* check not compatible vmas */
639 * Check that this vma isn't already owned by a
640 * different userfaultfd. We can't allow more than one
641 * userfaultfd to own a single vma simultaneously or we
642 * wouldn't know which one to deliver the userfaults to.
645 if (cur->vm_userfaultfd_ctx.ctx &&
646 cur->vm_userfaultfd_ctx.ctx != ctx)
653 if (vma->vm_start < start)
661 BUG_ON(vma->vm_userfaultfd_ctx.ctx &&
662 vma->vm_userfaultfd_ctx.ctx != ctx);
665 * Nothing to do: this vma is already registered into this
666 * userfaultfd and with the right tracking mode too.
668 if (vma->vm_userfaultfd_ctx.ctx == ctx &&
669 (vma->vm_flags & vm_flags) == vm_flags)
672 if (vma->vm_start > start)
673 start = vma->vm_start;
674 vma_end = min(end, vma->vm_end);
676 new_flags = (vma->vm_flags & ~vm_flags) | vm_flags;
677 prev = vma_merge(mm, prev, start, vma_end, new_flags,
678 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
680 ((struct vm_userfaultfd_ctx){ ctx }));
685 if (vma->vm_start < start) {
686 ret = split_vma(mm, vma, start, 1);
690 if (vma->vm_end > end) {
691 ret = split_vma(mm, vma, end, 0);
697 * In the vma_merge() successful mprotect-like case 8:
698 * the next vma was merged into the current one and
699 * the current one has not been updated yet.
701 vma->vm_flags = new_flags;
702 vma->vm_userfaultfd_ctx.ctx = ctx;
708 } while (vma && vma->vm_start < end);
710 up_write(&mm->mmap_sem);
713 * Now that we scanned all vmas we can already tell
714 * userland which ioctls methods are guaranteed to
715 * succeed on this range.
717 if (put_user(UFFD_API_RANGE_IOCTLS,
718 &user_uffdio_register->ioctls))
725 static int userfaultfd_unregister(struct userfaultfd_ctx *ctx,
728 struct mm_struct *mm = ctx->mm;
729 struct vm_area_struct *vma, *prev, *cur;
731 struct uffdio_range uffdio_unregister;
732 unsigned long new_flags;
734 unsigned long start, end, vma_end;
735 const void __user *buf = (void __user *)arg;
738 if (copy_from_user(&uffdio_unregister, buf, sizeof(uffdio_unregister)))
741 ret = validate_range(mm, uffdio_unregister.start,
742 uffdio_unregister.len);
746 start = uffdio_unregister.start;
747 end = start + uffdio_unregister.len;
749 down_write(&mm->mmap_sem);
750 vma = find_vma_prev(mm, start, &prev);
756 /* check that there's at least one vma in the range */
758 if (vma->vm_start >= end)
762 * Search for not compatible vmas.
764 * FIXME: this shall be relaxed later so that it doesn't fail
765 * on tmpfs backed vmas (in addition to the current allowance
766 * on anonymous vmas).
770 for (cur = vma; cur && cur->vm_start < end; cur = cur->vm_next) {
773 BUG_ON(!!cur->vm_userfaultfd_ctx.ctx ^
774 !!(cur->vm_flags & (VM_UFFD_MISSING | VM_UFFD_WP)));
777 * Check not compatible vmas, not strictly required
778 * here as not compatible vmas cannot have an
779 * userfaultfd_ctx registered on them, but this
780 * provides for more strict behavior to notice
781 * unregistration errors.
790 if (vma->vm_start < start)
800 * Nothing to do: this vma is already registered into this
801 * userfaultfd and with the right tracking mode too.
803 if (!vma->vm_userfaultfd_ctx.ctx)
806 if (vma->vm_start > start)
807 start = vma->vm_start;
808 vma_end = min(end, vma->vm_end);
810 new_flags = vma->vm_flags & ~(VM_UFFD_MISSING | VM_UFFD_WP);
811 prev = vma_merge(mm, prev, start, vma_end, new_flags,
812 vma->anon_vma, vma->vm_file, vma->vm_pgoff,
819 if (vma->vm_start < start) {
820 ret = split_vma(mm, vma, start, 1);
824 if (vma->vm_end > end) {
825 ret = split_vma(mm, vma, end, 0);
831 * In the vma_merge() successful mprotect-like case 8:
832 * the next vma was merged into the current one and
833 * the current one has not been updated yet.
835 vma->vm_flags = new_flags;
836 vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
842 } while (vma && vma->vm_start < end);
844 up_write(&mm->mmap_sem);
850 * userfaultfd_wake is needed in case an userfault is in flight by the
851 * time a UFFDIO_COPY (or other ioctl variants) completes. The page
852 * may be well get mapped and the page fault if repeated wouldn't lead
853 * to a userfault anymore, but before scheduling in TASK_KILLABLE mode
854 * handle_userfault() doesn't recheck the pagetables and it doesn't
855 * serialize against UFFDO_COPY (or other ioctl variants). Ultimately
856 * the knowledge of which pages are mapped is left to userland who is
857 * responsible for handling the race between read() userfaults and
858 * background UFFDIO_COPY (or other ioctl variants), if done by
859 * separate concurrent threads.
861 * userfaultfd_wake may be used in combination with the
862 * UFFDIO_*_MODE_DONTWAKE to wakeup userfaults in batches.
864 static int userfaultfd_wake(struct userfaultfd_ctx *ctx,
868 struct uffdio_range uffdio_wake;
869 struct userfaultfd_wake_range range;
870 const void __user *buf = (void __user *)arg;
873 if (copy_from_user(&uffdio_wake, buf, sizeof(uffdio_wake)))
876 ret = validate_range(ctx->mm, uffdio_wake.start, uffdio_wake.len);
880 range.start = uffdio_wake.start;
881 range.len = uffdio_wake.len;
884 * len == 0 means wake all and we don't want to wake all here,
885 * so check it again to be sure.
887 VM_BUG_ON(!range.len);
889 wake_userfault(ctx, &range);
897 * userland asks for a certain API version and we return which bits
898 * and ioctl commands are implemented in this kernel for such API
899 * version or -EINVAL if unknown.
901 static int userfaultfd_api(struct userfaultfd_ctx *ctx,
904 struct uffdio_api uffdio_api;
905 void __user *buf = (void __user *)arg;
909 if (ctx->state != UFFD_STATE_WAIT_API)
912 if (copy_from_user(&uffdio_api, buf, sizeof(uffdio_api)))
914 if (uffdio_api.api != UFFD_API || uffdio_api.features) {
915 memset(&uffdio_api, 0, sizeof(uffdio_api));
916 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
921 uffdio_api.features = UFFD_API_FEATURES;
922 uffdio_api.ioctls = UFFD_API_IOCTLS;
924 if (copy_to_user(buf, &uffdio_api, sizeof(uffdio_api)))
926 ctx->state = UFFD_STATE_RUNNING;
932 static long userfaultfd_ioctl(struct file *file, unsigned cmd,
936 struct userfaultfd_ctx *ctx = file->private_data;
940 ret = userfaultfd_api(ctx, arg);
942 case UFFDIO_REGISTER:
943 ret = userfaultfd_register(ctx, arg);
945 case UFFDIO_UNREGISTER:
946 ret = userfaultfd_unregister(ctx, arg);
949 ret = userfaultfd_wake(ctx, arg);
955 #ifdef CONFIG_PROC_FS
956 static void userfaultfd_show_fdinfo(struct seq_file *m, struct file *f)
958 struct userfaultfd_ctx *ctx = f->private_data;
960 struct userfaultfd_wait_queue *uwq;
961 unsigned long pending = 0, total = 0;
963 spin_lock(&ctx->fault_wqh.lock);
964 list_for_each_entry(wq, &ctx->fault_wqh.task_list, task_list) {
965 uwq = container_of(wq, struct userfaultfd_wait_queue, wq);
970 spin_unlock(&ctx->fault_wqh.lock);
973 * If more protocols will be added, there will be all shown
974 * separated by a space. Like this:
975 * protocols: aa:... bb:...
977 seq_printf(m, "pending:\t%lu\ntotal:\t%lu\nAPI:\t%Lx:%x:%Lx\n",
978 pending, total, UFFD_API, UFFD_API_FEATURES,
979 UFFD_API_IOCTLS|UFFD_API_RANGE_IOCTLS);
983 static const struct file_operations userfaultfd_fops = {
984 #ifdef CONFIG_PROC_FS
985 .show_fdinfo = userfaultfd_show_fdinfo,
987 .release = userfaultfd_release,
988 .poll = userfaultfd_poll,
989 .read = userfaultfd_read,
990 .unlocked_ioctl = userfaultfd_ioctl,
991 .compat_ioctl = userfaultfd_ioctl,
992 .llseek = noop_llseek,
996 * userfaultfd_file_create - Creates an userfaultfd file pointer.
997 * @flags: Flags for the userfaultfd file.
999 * This function creates an userfaultfd file pointer, w/out installing
1000 * it into the fd table. This is useful when the userfaultfd file is
1001 * used during the initialization of data structures that require
1002 * extra setup after the userfaultfd creation. So the userfaultfd
1003 * creation is split into the file pointer creation phase, and the
1004 * file descriptor installation phase. In this way races with
1005 * userspace closing the newly installed file descriptor can be
1006 * avoided. Returns an userfaultfd file pointer, or a proper error
1009 static struct file *userfaultfd_file_create(int flags)
1012 struct userfaultfd_ctx *ctx;
1014 BUG_ON(!current->mm);
1016 /* Check the UFFD_* constants for consistency. */
1017 BUILD_BUG_ON(UFFD_CLOEXEC != O_CLOEXEC);
1018 BUILD_BUG_ON(UFFD_NONBLOCK != O_NONBLOCK);
1020 file = ERR_PTR(-EINVAL);
1021 if (flags & ~UFFD_SHARED_FCNTL_FLAGS)
1024 file = ERR_PTR(-ENOMEM);
1025 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
1029 atomic_set(&ctx->refcount, 1);
1030 init_waitqueue_head(&ctx->fault_wqh);
1031 init_waitqueue_head(&ctx->fd_wqh);
1033 ctx->state = UFFD_STATE_WAIT_API;
1034 ctx->released = false;
1035 ctx->mm = current->mm;
1036 /* prevent the mm struct to be freed */
1037 atomic_inc(&ctx->mm->mm_users);
1039 file = anon_inode_getfile("[userfaultfd]", &userfaultfd_fops, ctx,
1040 O_RDWR | (flags & UFFD_SHARED_FCNTL_FLAGS));
1047 SYSCALL_DEFINE1(userfaultfd, int, flags)
1052 error = get_unused_fd_flags(flags & UFFD_SHARED_FCNTL_FLAGS);
1057 file = userfaultfd_file_create(flags);
1059 error = PTR_ERR(file);
1060 goto err_put_unused_fd;
1062 fd_install(fd, file);