1 // SPDX-License-Identifier: GPL-2.0-only
3 * linux/mm/mmu_notifier.c
5 * Copyright (C) 2008 Qumranet, Inc.
6 * Copyright (C) 2008 SGI
7 * Christoph Lameter <cl@linux.com>
10 #include <linux/rculist.h>
11 #include <linux/mmu_notifier.h>
12 #include <linux/export.h>
14 #include <linux/err.h>
15 #include <linux/srcu.h>
16 #include <linux/rcupdate.h>
17 #include <linux/sched.h>
18 #include <linux/sched/mm.h>
19 #include <linux/slab.h>
21 /* global SRCU for all MMs */
22 DEFINE_STATIC_SRCU(srcu
);
25 * This function allows mmu_notifier::release callback to delay a call to
26 * a function that will free appropriate resources. The function must be
27 * quick and must not block.
29 void mmu_notifier_call_srcu(struct rcu_head
*rcu
,
30 void (*func
)(struct rcu_head
*rcu
))
32 call_srcu(&srcu
, rcu
, func
);
34 EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu
);
37 * This function can't run concurrently against mmu_notifier_register
38 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
39 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
40 * in parallel despite there being no task using this mm any more,
41 * through the vmas outside of the exit_mmap context, such as with
42 * vmtruncate. This serializes against mmu_notifier_unregister with
43 * the mmu_notifier_mm->lock in addition to SRCU and it serializes
44 * against the other mmu notifiers with SRCU. struct mmu_notifier_mm
45 * can't go away from under us as exit_mmap holds an mm_count pin
48 void __mmu_notifier_release(struct mm_struct
*mm
)
50 struct mmu_notifier
*mn
;
54 * SRCU here will block mmu_notifier_unregister until
57 id
= srcu_read_lock(&srcu
);
58 hlist_for_each_entry_rcu(mn
, &mm
->mmu_notifier_mm
->list
, hlist
)
60 * If ->release runs before mmu_notifier_unregister it must be
61 * handled, as it's the only way for the driver to flush all
62 * existing sptes and stop the driver from establishing any more
63 * sptes before all the pages in the mm are freed.
66 mn
->ops
->release(mn
, mm
);
68 spin_lock(&mm
->mmu_notifier_mm
->lock
);
69 while (unlikely(!hlist_empty(&mm
->mmu_notifier_mm
->list
))) {
70 mn
= hlist_entry(mm
->mmu_notifier_mm
->list
.first
,
74 * We arrived before mmu_notifier_unregister so
75 * mmu_notifier_unregister will do nothing other than to wait
76 * for ->release to finish and for mmu_notifier_unregister to
79 hlist_del_init_rcu(&mn
->hlist
);
81 spin_unlock(&mm
->mmu_notifier_mm
->lock
);
82 srcu_read_unlock(&srcu
, id
);
85 * synchronize_srcu here prevents mmu_notifier_release from returning to
86 * exit_mmap (which would proceed with freeing all pages in the mm)
87 * until the ->release method returns, if it was invoked by
88 * mmu_notifier_unregister.
90 * The mmu_notifier_mm can't go away from under us because one mm_count
91 * is held by exit_mmap.
93 synchronize_srcu(&srcu
);
97 * If no young bitflag is supported by the hardware, ->clear_flush_young can
98 * unmap the address and return 1 or 0 depending if the mapping previously
101 int __mmu_notifier_clear_flush_young(struct mm_struct
*mm
,
105 struct mmu_notifier
*mn
;
108 id
= srcu_read_lock(&srcu
);
109 hlist_for_each_entry_rcu(mn
, &mm
->mmu_notifier_mm
->list
, hlist
) {
110 if (mn
->ops
->clear_flush_young
)
111 young
|= mn
->ops
->clear_flush_young(mn
, mm
, start
, end
);
113 srcu_read_unlock(&srcu
, id
);
118 int __mmu_notifier_clear_young(struct mm_struct
*mm
,
122 struct mmu_notifier
*mn
;
125 id
= srcu_read_lock(&srcu
);
126 hlist_for_each_entry_rcu(mn
, &mm
->mmu_notifier_mm
->list
, hlist
) {
127 if (mn
->ops
->clear_young
)
128 young
|= mn
->ops
->clear_young(mn
, mm
, start
, end
);
130 srcu_read_unlock(&srcu
, id
);
135 int __mmu_notifier_test_young(struct mm_struct
*mm
,
136 unsigned long address
)
138 struct mmu_notifier
*mn
;
141 id
= srcu_read_lock(&srcu
);
142 hlist_for_each_entry_rcu(mn
, &mm
->mmu_notifier_mm
->list
, hlist
) {
143 if (mn
->ops
->test_young
) {
144 young
= mn
->ops
->test_young(mn
, mm
, address
);
149 srcu_read_unlock(&srcu
, id
);
154 void __mmu_notifier_change_pte(struct mm_struct
*mm
, unsigned long address
,
157 struct mmu_notifier
*mn
;
160 id
= srcu_read_lock(&srcu
);
161 hlist_for_each_entry_rcu(mn
, &mm
->mmu_notifier_mm
->list
, hlist
) {
162 if (mn
->ops
->change_pte
)
163 mn
->ops
->change_pte(mn
, mm
, address
, pte
);
165 srcu_read_unlock(&srcu
, id
);
168 int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range
*range
)
170 struct mmu_notifier
*mn
;
174 id
= srcu_read_lock(&srcu
);
175 hlist_for_each_entry_rcu(mn
, &range
->mm
->mmu_notifier_mm
->list
, hlist
) {
176 if (mn
->ops
->invalidate_range_start
) {
177 int _ret
= mn
->ops
->invalidate_range_start(mn
, range
);
179 pr_info("%pS callback failed with %d in %sblockable context.\n",
180 mn
->ops
->invalidate_range_start
, _ret
,
181 !mmu_notifier_range_blockable(range
) ? "non-" : "");
186 srcu_read_unlock(&srcu
, id
);
190 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start
);
192 void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range
*range
,
195 struct mmu_notifier
*mn
;
198 id
= srcu_read_lock(&srcu
);
199 hlist_for_each_entry_rcu(mn
, &range
->mm
->mmu_notifier_mm
->list
, hlist
) {
201 * Call invalidate_range here too to avoid the need for the
202 * subsystem of having to register an invalidate_range_end
203 * call-back when there is invalidate_range already. Usually a
204 * subsystem registers either invalidate_range_start()/end() or
205 * invalidate_range(), so this will be no additional overhead
206 * (besides the pointer check).
208 * We skip call to invalidate_range() if we know it is safe ie
209 * call site use mmu_notifier_invalidate_range_only_end() which
210 * is safe to do when we know that a call to invalidate_range()
211 * already happen under page table lock.
213 if (!only_end
&& mn
->ops
->invalidate_range
)
214 mn
->ops
->invalidate_range(mn
, range
->mm
,
217 if (mn
->ops
->invalidate_range_end
)
218 mn
->ops
->invalidate_range_end(mn
, range
);
220 srcu_read_unlock(&srcu
, id
);
222 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end
);
224 void __mmu_notifier_invalidate_range(struct mm_struct
*mm
,
225 unsigned long start
, unsigned long end
)
227 struct mmu_notifier
*mn
;
230 id
= srcu_read_lock(&srcu
);
231 hlist_for_each_entry_rcu(mn
, &mm
->mmu_notifier_mm
->list
, hlist
) {
232 if (mn
->ops
->invalidate_range
)
233 mn
->ops
->invalidate_range(mn
, mm
, start
, end
);
235 srcu_read_unlock(&srcu
, id
);
237 EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range
);
239 static int do_mmu_notifier_register(struct mmu_notifier
*mn
,
240 struct mm_struct
*mm
,
243 struct mmu_notifier_mm
*mmu_notifier_mm
;
246 BUG_ON(atomic_read(&mm
->mm_users
) <= 0);
249 mmu_notifier_mm
= kmalloc(sizeof(struct mmu_notifier_mm
), GFP_KERNEL
);
250 if (unlikely(!mmu_notifier_mm
))
254 down_write(&mm
->mmap_sem
);
255 ret
= mm_take_all_locks(mm
);
259 if (!mm_has_notifiers(mm
)) {
260 INIT_HLIST_HEAD(&mmu_notifier_mm
->list
);
261 spin_lock_init(&mmu_notifier_mm
->lock
);
263 mm
->mmu_notifier_mm
= mmu_notifier_mm
;
264 mmu_notifier_mm
= NULL
;
269 * Serialize the update against mmu_notifier_unregister. A
270 * side note: mmu_notifier_release can't run concurrently with
271 * us because we hold the mm_users pin (either implicitly as
272 * current->mm or explicitly with get_task_mm() or similar).
273 * We can't race against any other mmu notifier method either
274 * thanks to mm_take_all_locks().
276 spin_lock(&mm
->mmu_notifier_mm
->lock
);
277 hlist_add_head_rcu(&mn
->hlist
, &mm
->mmu_notifier_mm
->list
);
278 spin_unlock(&mm
->mmu_notifier_mm
->lock
);
280 mm_drop_all_locks(mm
);
283 up_write(&mm
->mmap_sem
);
284 kfree(mmu_notifier_mm
);
286 BUG_ON(atomic_read(&mm
->mm_users
) <= 0);
291 * Must not hold mmap_sem nor any other VM related lock when calling
292 * this registration function. Must also ensure mm_users can't go down
293 * to zero while this runs to avoid races with mmu_notifier_release,
294 * so mm has to be current->mm or the mm should be pinned safely such
295 * as with get_task_mm(). If the mm is not current->mm, the mm_users
296 * pin should be released by calling mmput after mmu_notifier_register
297 * returns. mmu_notifier_unregister must be always called to
298 * unregister the notifier. mm_count is automatically pinned to allow
299 * mmu_notifier_unregister to safely run at any time later, before or
300 * after exit_mmap. ->release will always be called before exit_mmap
303 int mmu_notifier_register(struct mmu_notifier
*mn
, struct mm_struct
*mm
)
305 return do_mmu_notifier_register(mn
, mm
, 1);
307 EXPORT_SYMBOL_GPL(mmu_notifier_register
);
310 * Same as mmu_notifier_register but here the caller must hold the
311 * mmap_sem in write mode.
313 int __mmu_notifier_register(struct mmu_notifier
*mn
, struct mm_struct
*mm
)
315 return do_mmu_notifier_register(mn
, mm
, 0);
317 EXPORT_SYMBOL_GPL(__mmu_notifier_register
);
319 /* this is called after the last mmu_notifier_unregister() returned */
320 void __mmu_notifier_mm_destroy(struct mm_struct
*mm
)
322 BUG_ON(!hlist_empty(&mm
->mmu_notifier_mm
->list
));
323 kfree(mm
->mmu_notifier_mm
);
324 mm
->mmu_notifier_mm
= LIST_POISON1
; /* debug */
328 * This releases the mm_count pin automatically and frees the mm
329 * structure if it was the last user of it. It serializes against
330 * running mmu notifiers with SRCU and against mmu_notifier_unregister
331 * with the unregister lock + SRCU. All sptes must be dropped before
332 * calling mmu_notifier_unregister. ->release or any other notifier
333 * method may be invoked concurrently with mmu_notifier_unregister,
334 * and only after mmu_notifier_unregister returned we're guaranteed
335 * that ->release or any other method can't run anymore.
337 void mmu_notifier_unregister(struct mmu_notifier
*mn
, struct mm_struct
*mm
)
339 BUG_ON(atomic_read(&mm
->mm_count
) <= 0);
341 if (!hlist_unhashed(&mn
->hlist
)) {
343 * SRCU here will force exit_mmap to wait for ->release to
344 * finish before freeing the pages.
348 id
= srcu_read_lock(&srcu
);
350 * exit_mmap will block in mmu_notifier_release to guarantee
351 * that ->release is called before freeing the pages.
353 if (mn
->ops
->release
)
354 mn
->ops
->release(mn
, mm
);
355 srcu_read_unlock(&srcu
, id
);
357 spin_lock(&mm
->mmu_notifier_mm
->lock
);
359 * Can not use list_del_rcu() since __mmu_notifier_release
360 * can delete it before we hold the lock.
362 hlist_del_init_rcu(&mn
->hlist
);
363 spin_unlock(&mm
->mmu_notifier_mm
->lock
);
367 * Wait for any running method to finish, of course including
368 * ->release if it was run by mmu_notifier_release instead of us.
370 synchronize_srcu(&srcu
);
372 BUG_ON(atomic_read(&mm
->mm_count
) <= 0);
376 EXPORT_SYMBOL_GPL(mmu_notifier_unregister
);
379 * Same as mmu_notifier_unregister but no callback and no srcu synchronization.
381 void mmu_notifier_unregister_no_release(struct mmu_notifier
*mn
,
382 struct mm_struct
*mm
)
384 spin_lock(&mm
->mmu_notifier_mm
->lock
);
386 * Can not use list_del_rcu() since __mmu_notifier_release
387 * can delete it before we hold the lock.
389 hlist_del_init_rcu(&mn
->hlist
);
390 spin_unlock(&mm
->mmu_notifier_mm
->lock
);
392 BUG_ON(atomic_read(&mm
->mm_count
) <= 0);
395 EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release
);
398 mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range
*range
)
400 if (!range
->vma
|| range
->event
!= MMU_NOTIFY_PROTECTION_VMA
)
402 /* Return true if the vma still have the read flag set. */
403 return range
->vma
->vm_flags
& VM_READ
;
405 EXPORT_SYMBOL_GPL(mmu_notifier_range_update_to_read_only
);