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Commit | Line | Data |
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cddb8a5c AA |
1 | /* |
2 | * linux/mm/mmu_notifier.c | |
3 | * | |
4 | * Copyright (C) 2008 Qumranet, Inc. | |
5 | * Copyright (C) 2008 SGI | |
93e205a7 | 6 | * Christoph Lameter <cl@linux.com> |
cddb8a5c AA |
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 | ||
12 | #include <linux/rculist.h> | |
13 | #include <linux/mmu_notifier.h> | |
b95f1b31 | 14 | #include <linux/export.h> |
cddb8a5c AA |
15 | #include <linux/mm.h> |
16 | #include <linux/err.h> | |
21a92735 | 17 | #include <linux/srcu.h> |
cddb8a5c AA |
18 | #include <linux/rcupdate.h> |
19 | #include <linux/sched.h> | |
6e84f315 | 20 | #include <linux/sched/mm.h> |
5a0e3ad6 | 21 | #include <linux/slab.h> |
cddb8a5c | 22 | |
21a92735 | 23 | /* global SRCU for all MMs */ |
dde8da6c | 24 | DEFINE_STATIC_SRCU(srcu); |
21a92735 | 25 | |
b972216e PZ |
26 | /* |
27 | * This function allows mmu_notifier::release callback to delay a call to | |
28 | * a function that will free appropriate resources. The function must be | |
29 | * quick and must not block. | |
30 | */ | |
31 | void mmu_notifier_call_srcu(struct rcu_head *rcu, | |
32 | void (*func)(struct rcu_head *rcu)) | |
33 | { | |
34 | call_srcu(&srcu, rcu, func); | |
35 | } | |
36 | EXPORT_SYMBOL_GPL(mmu_notifier_call_srcu); | |
37 | ||
38 | void mmu_notifier_synchronize(void) | |
39 | { | |
40 | /* Wait for any running method to finish. */ | |
41 | srcu_barrier(&srcu); | |
42 | } | |
43 | EXPORT_SYMBOL_GPL(mmu_notifier_synchronize); | |
44 | ||
cddb8a5c AA |
45 | /* |
46 | * This function can't run concurrently against mmu_notifier_register | |
47 | * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap | |
48 | * runs with mm_users == 0. Other tasks may still invoke mmu notifiers | |
49 | * in parallel despite there being no task using this mm any more, | |
50 | * through the vmas outside of the exit_mmap context, such as with | |
51 | * vmtruncate. This serializes against mmu_notifier_unregister with | |
21a92735 SG |
52 | * the mmu_notifier_mm->lock in addition to SRCU and it serializes |
53 | * against the other mmu notifiers with SRCU. struct mmu_notifier_mm | |
cddb8a5c AA |
54 | * can't go away from under us as exit_mmap holds an mm_count pin |
55 | * itself. | |
56 | */ | |
57 | void __mmu_notifier_release(struct mm_struct *mm) | |
58 | { | |
59 | struct mmu_notifier *mn; | |
21a92735 | 60 | int id; |
3ad3d901 XG |
61 | |
62 | /* | |
d34883d4 XG |
63 | * SRCU here will block mmu_notifier_unregister until |
64 | * ->release returns. | |
3ad3d901 | 65 | */ |
21a92735 | 66 | id = srcu_read_lock(&srcu); |
d34883d4 XG |
67 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) |
68 | /* | |
69 | * If ->release runs before mmu_notifier_unregister it must be | |
70 | * handled, as it's the only way for the driver to flush all | |
71 | * existing sptes and stop the driver from establishing any more | |
72 | * sptes before all the pages in the mm are freed. | |
73 | */ | |
74 | if (mn->ops->release) | |
75 | mn->ops->release(mn, mm); | |
d34883d4 | 76 | |
cddb8a5c AA |
77 | spin_lock(&mm->mmu_notifier_mm->lock); |
78 | while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) { | |
79 | mn = hlist_entry(mm->mmu_notifier_mm->list.first, | |
80 | struct mmu_notifier, | |
81 | hlist); | |
82 | /* | |
d34883d4 XG |
83 | * We arrived before mmu_notifier_unregister so |
84 | * mmu_notifier_unregister will do nothing other than to wait | |
85 | * for ->release to finish and for mmu_notifier_unregister to | |
86 | * return. | |
cddb8a5c AA |
87 | */ |
88 | hlist_del_init_rcu(&mn->hlist); | |
cddb8a5c AA |
89 | } |
90 | spin_unlock(&mm->mmu_notifier_mm->lock); | |
b972216e | 91 | srcu_read_unlock(&srcu, id); |
cddb8a5c AA |
92 | |
93 | /* | |
d34883d4 XG |
94 | * synchronize_srcu here prevents mmu_notifier_release from returning to |
95 | * exit_mmap (which would proceed with freeing all pages in the mm) | |
96 | * until the ->release method returns, if it was invoked by | |
97 | * mmu_notifier_unregister. | |
98 | * | |
99 | * The mmu_notifier_mm can't go away from under us because one mm_count | |
100 | * is held by exit_mmap. | |
cddb8a5c | 101 | */ |
21a92735 | 102 | synchronize_srcu(&srcu); |
cddb8a5c AA |
103 | } |
104 | ||
105 | /* | |
106 | * If no young bitflag is supported by the hardware, ->clear_flush_young can | |
107 | * unmap the address and return 1 or 0 depending if the mapping previously | |
108 | * existed or not. | |
109 | */ | |
110 | int __mmu_notifier_clear_flush_young(struct mm_struct *mm, | |
57128468 ALC |
111 | unsigned long start, |
112 | unsigned long end) | |
cddb8a5c AA |
113 | { |
114 | struct mmu_notifier *mn; | |
21a92735 | 115 | int young = 0, id; |
cddb8a5c | 116 | |
21a92735 | 117 | id = srcu_read_lock(&srcu); |
b67bfe0d | 118 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { |
cddb8a5c | 119 | if (mn->ops->clear_flush_young) |
57128468 | 120 | young |= mn->ops->clear_flush_young(mn, mm, start, end); |
cddb8a5c | 121 | } |
21a92735 | 122 | srcu_read_unlock(&srcu, id); |
cddb8a5c AA |
123 | |
124 | return young; | |
125 | } | |
126 | ||
1d7715c6 VD |
127 | int __mmu_notifier_clear_young(struct mm_struct *mm, |
128 | unsigned long start, | |
129 | unsigned long end) | |
130 | { | |
131 | struct mmu_notifier *mn; | |
132 | int young = 0, id; | |
133 | ||
134 | id = srcu_read_lock(&srcu); | |
135 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { | |
136 | if (mn->ops->clear_young) | |
137 | young |= mn->ops->clear_young(mn, mm, start, end); | |
138 | } | |
139 | srcu_read_unlock(&srcu, id); | |
140 | ||
141 | return young; | |
142 | } | |
143 | ||
8ee53820 AA |
144 | int __mmu_notifier_test_young(struct mm_struct *mm, |
145 | unsigned long address) | |
146 | { | |
147 | struct mmu_notifier *mn; | |
21a92735 | 148 | int young = 0, id; |
8ee53820 | 149 | |
21a92735 | 150 | id = srcu_read_lock(&srcu); |
b67bfe0d | 151 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { |
8ee53820 AA |
152 | if (mn->ops->test_young) { |
153 | young = mn->ops->test_young(mn, mm, address); | |
154 | if (young) | |
155 | break; | |
156 | } | |
157 | } | |
21a92735 | 158 | srcu_read_unlock(&srcu, id); |
8ee53820 AA |
159 | |
160 | return young; | |
161 | } | |
162 | ||
828502d3 IE |
163 | void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address, |
164 | pte_t pte) | |
165 | { | |
166 | struct mmu_notifier *mn; | |
21a92735 | 167 | int id; |
828502d3 | 168 | |
21a92735 | 169 | id = srcu_read_lock(&srcu); |
b67bfe0d | 170 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { |
828502d3 IE |
171 | if (mn->ops->change_pte) |
172 | mn->ops->change_pte(mn, mm, address, pte); | |
828502d3 | 173 | } |
21a92735 | 174 | srcu_read_unlock(&srcu, id); |
828502d3 IE |
175 | } |
176 | ||
93065ac7 MH |
177 | int __mmu_notifier_invalidate_range_start(struct mm_struct *mm, |
178 | unsigned long start, unsigned long end, | |
179 | bool blockable) | |
cddb8a5c AA |
180 | { |
181 | struct mmu_notifier *mn; | |
93065ac7 | 182 | int ret = 0; |
21a92735 | 183 | int id; |
cddb8a5c | 184 | |
21a92735 | 185 | id = srcu_read_lock(&srcu); |
b67bfe0d | 186 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { |
93065ac7 MH |
187 | if (mn->ops->invalidate_range_start) { |
188 | int _ret = mn->ops->invalidate_range_start(mn, mm, start, end, blockable); | |
189 | if (_ret) { | |
190 | pr_info("%pS callback failed with %d in %sblockable context.\n", | |
191 | mn->ops->invalidate_range_start, _ret, | |
192 | !blockable ? "non-" : ""); | |
193 | ret = _ret; | |
194 | } | |
195 | } | |
cddb8a5c | 196 | } |
21a92735 | 197 | srcu_read_unlock(&srcu, id); |
93065ac7 MH |
198 | |
199 | return ret; | |
cddb8a5c | 200 | } |
fa794199 | 201 | EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start); |
cddb8a5c AA |
202 | |
203 | void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, | |
4645b9fe JG |
204 | unsigned long start, |
205 | unsigned long end, | |
206 | bool only_end) | |
cddb8a5c AA |
207 | { |
208 | struct mmu_notifier *mn; | |
21a92735 | 209 | int id; |
cddb8a5c | 210 | |
21a92735 | 211 | id = srcu_read_lock(&srcu); |
b67bfe0d | 212 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { |
0f0a327f JR |
213 | /* |
214 | * Call invalidate_range here too to avoid the need for the | |
215 | * subsystem of having to register an invalidate_range_end | |
216 | * call-back when there is invalidate_range already. Usually a | |
217 | * subsystem registers either invalidate_range_start()/end() or | |
218 | * invalidate_range(), so this will be no additional overhead | |
219 | * (besides the pointer check). | |
4645b9fe JG |
220 | * |
221 | * We skip call to invalidate_range() if we know it is safe ie | |
222 | * call site use mmu_notifier_invalidate_range_only_end() which | |
223 | * is safe to do when we know that a call to invalidate_range() | |
224 | * already happen under page table lock. | |
0f0a327f | 225 | */ |
4645b9fe | 226 | if (!only_end && mn->ops->invalidate_range) |
0f0a327f | 227 | mn->ops->invalidate_range(mn, mm, start, end); |
cddb8a5c AA |
228 | if (mn->ops->invalidate_range_end) |
229 | mn->ops->invalidate_range_end(mn, mm, start, end); | |
230 | } | |
21a92735 | 231 | srcu_read_unlock(&srcu, id); |
cddb8a5c | 232 | } |
fa794199 | 233 | EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end); |
cddb8a5c | 234 | |
0f0a327f JR |
235 | void __mmu_notifier_invalidate_range(struct mm_struct *mm, |
236 | unsigned long start, unsigned long end) | |
237 | { | |
238 | struct mmu_notifier *mn; | |
239 | int id; | |
240 | ||
241 | id = srcu_read_lock(&srcu); | |
242 | hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) { | |
243 | if (mn->ops->invalidate_range) | |
244 | mn->ops->invalidate_range(mn, mm, start, end); | |
245 | } | |
246 | srcu_read_unlock(&srcu, id); | |
247 | } | |
248 | EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range); | |
249 | ||
cddb8a5c AA |
250 | static int do_mmu_notifier_register(struct mmu_notifier *mn, |
251 | struct mm_struct *mm, | |
252 | int take_mmap_sem) | |
253 | { | |
254 | struct mmu_notifier_mm *mmu_notifier_mm; | |
255 | int ret; | |
256 | ||
257 | BUG_ON(atomic_read(&mm->mm_users) <= 0); | |
258 | ||
35cfa2b0 GS |
259 | ret = -ENOMEM; |
260 | mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL); | |
261 | if (unlikely(!mmu_notifier_mm)) | |
262 | goto out; | |
263 | ||
cddb8a5c AA |
264 | if (take_mmap_sem) |
265 | down_write(&mm->mmap_sem); | |
266 | ret = mm_take_all_locks(mm); | |
267 | if (unlikely(ret)) | |
35cfa2b0 | 268 | goto out_clean; |
cddb8a5c AA |
269 | |
270 | if (!mm_has_notifiers(mm)) { | |
271 | INIT_HLIST_HEAD(&mmu_notifier_mm->list); | |
272 | spin_lock_init(&mmu_notifier_mm->lock); | |
e0f3c3f7 | 273 | |
cddb8a5c | 274 | mm->mmu_notifier_mm = mmu_notifier_mm; |
35cfa2b0 | 275 | mmu_notifier_mm = NULL; |
cddb8a5c | 276 | } |
f1f10076 | 277 | mmgrab(mm); |
cddb8a5c AA |
278 | |
279 | /* | |
280 | * Serialize the update against mmu_notifier_unregister. A | |
281 | * side note: mmu_notifier_release can't run concurrently with | |
282 | * us because we hold the mm_users pin (either implicitly as | |
283 | * current->mm or explicitly with get_task_mm() or similar). | |
284 | * We can't race against any other mmu notifier method either | |
285 | * thanks to mm_take_all_locks(). | |
286 | */ | |
287 | spin_lock(&mm->mmu_notifier_mm->lock); | |
288 | hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list); | |
289 | spin_unlock(&mm->mmu_notifier_mm->lock); | |
290 | ||
291 | mm_drop_all_locks(mm); | |
35cfa2b0 | 292 | out_clean: |
cddb8a5c AA |
293 | if (take_mmap_sem) |
294 | up_write(&mm->mmap_sem); | |
35cfa2b0 GS |
295 | kfree(mmu_notifier_mm); |
296 | out: | |
cddb8a5c AA |
297 | BUG_ON(atomic_read(&mm->mm_users) <= 0); |
298 | return ret; | |
299 | } | |
300 | ||
301 | /* | |
302 | * Must not hold mmap_sem nor any other VM related lock when calling | |
303 | * this registration function. Must also ensure mm_users can't go down | |
304 | * to zero while this runs to avoid races with mmu_notifier_release, | |
305 | * so mm has to be current->mm or the mm should be pinned safely such | |
306 | * as with get_task_mm(). If the mm is not current->mm, the mm_users | |
307 | * pin should be released by calling mmput after mmu_notifier_register | |
308 | * returns. mmu_notifier_unregister must be always called to | |
309 | * unregister the notifier. mm_count is automatically pinned to allow | |
310 | * mmu_notifier_unregister to safely run at any time later, before or | |
311 | * after exit_mmap. ->release will always be called before exit_mmap | |
312 | * frees the pages. | |
313 | */ | |
314 | int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm) | |
315 | { | |
316 | return do_mmu_notifier_register(mn, mm, 1); | |
317 | } | |
318 | EXPORT_SYMBOL_GPL(mmu_notifier_register); | |
319 | ||
320 | /* | |
321 | * Same as mmu_notifier_register but here the caller must hold the | |
322 | * mmap_sem in write mode. | |
323 | */ | |
324 | int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm) | |
325 | { | |
326 | return do_mmu_notifier_register(mn, mm, 0); | |
327 | } | |
328 | EXPORT_SYMBOL_GPL(__mmu_notifier_register); | |
329 | ||
330 | /* this is called after the last mmu_notifier_unregister() returned */ | |
331 | void __mmu_notifier_mm_destroy(struct mm_struct *mm) | |
332 | { | |
333 | BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list)); | |
334 | kfree(mm->mmu_notifier_mm); | |
335 | mm->mmu_notifier_mm = LIST_POISON1; /* debug */ | |
336 | } | |
337 | ||
338 | /* | |
339 | * This releases the mm_count pin automatically and frees the mm | |
340 | * structure if it was the last user of it. It serializes against | |
21a92735 SG |
341 | * running mmu notifiers with SRCU and against mmu_notifier_unregister |
342 | * with the unregister lock + SRCU. All sptes must be dropped before | |
cddb8a5c AA |
343 | * calling mmu_notifier_unregister. ->release or any other notifier |
344 | * method may be invoked concurrently with mmu_notifier_unregister, | |
345 | * and only after mmu_notifier_unregister returned we're guaranteed | |
346 | * that ->release or any other method can't run anymore. | |
347 | */ | |
348 | void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm) | |
349 | { | |
350 | BUG_ON(atomic_read(&mm->mm_count) <= 0); | |
351 | ||
cddb8a5c | 352 | if (!hlist_unhashed(&mn->hlist)) { |
d34883d4 XG |
353 | /* |
354 | * SRCU here will force exit_mmap to wait for ->release to | |
355 | * finish before freeing the pages. | |
356 | */ | |
21a92735 | 357 | int id; |
3ad3d901 | 358 | |
d34883d4 | 359 | id = srcu_read_lock(&srcu); |
cddb8a5c | 360 | /* |
d34883d4 XG |
361 | * exit_mmap will block in mmu_notifier_release to guarantee |
362 | * that ->release is called before freeing the pages. | |
cddb8a5c AA |
363 | */ |
364 | if (mn->ops->release) | |
365 | mn->ops->release(mn, mm); | |
d34883d4 | 366 | srcu_read_unlock(&srcu, id); |
3ad3d901 | 367 | |
d34883d4 | 368 | spin_lock(&mm->mmu_notifier_mm->lock); |
751efd86 | 369 | /* |
d34883d4 XG |
370 | * Can not use list_del_rcu() since __mmu_notifier_release |
371 | * can delete it before we hold the lock. | |
751efd86 | 372 | */ |
d34883d4 | 373 | hlist_del_init_rcu(&mn->hlist); |
cddb8a5c | 374 | spin_unlock(&mm->mmu_notifier_mm->lock); |
d34883d4 | 375 | } |
cddb8a5c AA |
376 | |
377 | /* | |
d34883d4 | 378 | * Wait for any running method to finish, of course including |
83a35e36 | 379 | * ->release if it was run by mmu_notifier_release instead of us. |
cddb8a5c | 380 | */ |
21a92735 | 381 | synchronize_srcu(&srcu); |
cddb8a5c AA |
382 | |
383 | BUG_ON(atomic_read(&mm->mm_count) <= 0); | |
384 | ||
385 | mmdrop(mm); | |
386 | } | |
387 | EXPORT_SYMBOL_GPL(mmu_notifier_unregister); | |
21a92735 | 388 | |
b972216e PZ |
389 | /* |
390 | * Same as mmu_notifier_unregister but no callback and no srcu synchronization. | |
391 | */ | |
392 | void mmu_notifier_unregister_no_release(struct mmu_notifier *mn, | |
393 | struct mm_struct *mm) | |
394 | { | |
395 | spin_lock(&mm->mmu_notifier_mm->lock); | |
396 | /* | |
397 | * Can not use list_del_rcu() since __mmu_notifier_release | |
398 | * can delete it before we hold the lock. | |
399 | */ | |
400 | hlist_del_init_rcu(&mn->hlist); | |
401 | spin_unlock(&mm->mmu_notifier_mm->lock); | |
402 | ||
403 | BUG_ON(atomic_read(&mm->mm_count) <= 0); | |
404 | mmdrop(mm); | |
405 | } | |
406 | EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release); |