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1/*
2 * linux/mm/mmu_notifier.c
3 *
4 * Copyright (C) 2008 Qumranet, Inc.
5 * Copyright (C) 2008 SGI
6 * Christoph Lameter <clameter@sgi.com>
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>
14#include <linux/export.h>
15#include <linux/mm.h>
16#include <linux/err.h>
17#include <linux/srcu.h>
18#include <linux/rcupdate.h>
19#include <linux/sched.h>
20#include <linux/slab.h>
21
22/* global SRCU for all MMs */
23static struct srcu_struct srcu;
24
25/*
26 * This function can't run concurrently against mmu_notifier_register
27 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
28 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
29 * in parallel despite there being no task using this mm any more,
30 * through the vmas outside of the exit_mmap context, such as with
31 * vmtruncate. This serializes against mmu_notifier_unregister with
32 * the mmu_notifier_mm->lock in addition to SRCU and it serializes
33 * against the other mmu notifiers with SRCU. struct mmu_notifier_mm
34 * can't go away from under us as exit_mmap holds an mm_count pin
35 * itself.
36 */
37void __mmu_notifier_release(struct mm_struct *mm)
38{
39 struct mmu_notifier *mn;
40 int id;
41
42 /*
43 * SRCU here will block mmu_notifier_unregister until
44 * ->release returns.
45 */
46 id = srcu_read_lock(&srcu);
47 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist)
48 /*
49 * If ->release runs before mmu_notifier_unregister it must be
50 * handled, as it's the only way for the driver to flush all
51 * existing sptes and stop the driver from establishing any more
52 * sptes before all the pages in the mm are freed.
53 */
54 if (mn->ops->release)
55 mn->ops->release(mn, mm);
56 srcu_read_unlock(&srcu, id);
57
58 spin_lock(&mm->mmu_notifier_mm->lock);
59 while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
60 mn = hlist_entry(mm->mmu_notifier_mm->list.first,
61 struct mmu_notifier,
62 hlist);
63 /*
64 * We arrived before mmu_notifier_unregister so
65 * mmu_notifier_unregister will do nothing other than to wait
66 * for ->release to finish and for mmu_notifier_unregister to
67 * return.
68 */
69 hlist_del_init_rcu(&mn->hlist);
70 }
71 spin_unlock(&mm->mmu_notifier_mm->lock);
72
73 /*
74 * synchronize_srcu here prevents mmu_notifier_release from returning to
75 * exit_mmap (which would proceed with freeing all pages in the mm)
76 * until the ->release method returns, if it was invoked by
77 * mmu_notifier_unregister.
78 *
79 * The mmu_notifier_mm can't go away from under us because one mm_count
80 * is held by exit_mmap.
81 */
82 synchronize_srcu(&srcu);
83}
84
85/*
86 * If no young bitflag is supported by the hardware, ->clear_flush_young can
87 * unmap the address and return 1 or 0 depending if the mapping previously
88 * existed or not.
89 */
90int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
91 unsigned long address)
92{
93 struct mmu_notifier *mn;
94 int young = 0, id;
95
96 id = srcu_read_lock(&srcu);
97 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
98 if (mn->ops->clear_flush_young)
99 young |= mn->ops->clear_flush_young(mn, mm, address);
100 }
101 srcu_read_unlock(&srcu, id);
102
103 return young;
104}
105
106int __mmu_notifier_test_young(struct mm_struct *mm,
107 unsigned long address)
108{
109 struct mmu_notifier *mn;
110 int young = 0, id;
111
112 id = srcu_read_lock(&srcu);
113 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
114 if (mn->ops->test_young) {
115 young = mn->ops->test_young(mn, mm, address);
116 if (young)
117 break;
118 }
119 }
120 srcu_read_unlock(&srcu, id);
121
122 return young;
123}
124
125void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
126 pte_t pte)
127{
128 struct mmu_notifier *mn;
129 int id;
130
131 id = srcu_read_lock(&srcu);
132 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
133 if (mn->ops->change_pte)
134 mn->ops->change_pte(mn, mm, address, pte);
135 }
136 srcu_read_unlock(&srcu, id);
137}
138
139void __mmu_notifier_invalidate_page(struct mm_struct *mm,
140 unsigned long address)
141{
142 struct mmu_notifier *mn;
143 int id;
144
145 id = srcu_read_lock(&srcu);
146 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
147 if (mn->ops->invalidate_page)
148 mn->ops->invalidate_page(mn, mm, address);
149 }
150 srcu_read_unlock(&srcu, id);
151}
152
153void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
154 unsigned long start, unsigned long end)
155{
156 struct mmu_notifier *mn;
157 int id;
158
159 id = srcu_read_lock(&srcu);
160 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
161 if (mn->ops->invalidate_range_start)
162 mn->ops->invalidate_range_start(mn, mm, start, end);
163 }
164 srcu_read_unlock(&srcu, id);
165}
166EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_start);
167
168void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
169 unsigned long start, unsigned long end)
170{
171 struct mmu_notifier *mn;
172 int id;
173
174 id = srcu_read_lock(&srcu);
175 hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
176 if (mn->ops->invalidate_range_end)
177 mn->ops->invalidate_range_end(mn, mm, start, end);
178 }
179 srcu_read_unlock(&srcu, id);
180}
181EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range_end);
182
183static int do_mmu_notifier_register(struct mmu_notifier *mn,
184 struct mm_struct *mm,
185 int take_mmap_sem)
186{
187 struct mmu_notifier_mm *mmu_notifier_mm;
188 int ret;
189
190 BUG_ON(atomic_read(&mm->mm_users) <= 0);
191
192 /*
193 * Verify that mmu_notifier_init() already run and the global srcu is
194 * initialized.
195 */
196 BUG_ON(!srcu.per_cpu_ref);
197
198 ret = -ENOMEM;
199 mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
200 if (unlikely(!mmu_notifier_mm))
201 goto out;
202
203 if (take_mmap_sem)
204 down_write(&mm->mmap_sem);
205 ret = mm_take_all_locks(mm);
206 if (unlikely(ret))
207 goto out_clean;
208
209 if (!mm_has_notifiers(mm)) {
210 INIT_HLIST_HEAD(&mmu_notifier_mm->list);
211 spin_lock_init(&mmu_notifier_mm->lock);
212
213 mm->mmu_notifier_mm = mmu_notifier_mm;
214 mmu_notifier_mm = NULL;
215 }
216 atomic_inc(&mm->mm_count);
217
218 /*
219 * Serialize the update against mmu_notifier_unregister. A
220 * side note: mmu_notifier_release can't run concurrently with
221 * us because we hold the mm_users pin (either implicitly as
222 * current->mm or explicitly with get_task_mm() or similar).
223 * We can't race against any other mmu notifier method either
224 * thanks to mm_take_all_locks().
225 */
226 spin_lock(&mm->mmu_notifier_mm->lock);
227 hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
228 spin_unlock(&mm->mmu_notifier_mm->lock);
229
230 mm_drop_all_locks(mm);
231out_clean:
232 if (take_mmap_sem)
233 up_write(&mm->mmap_sem);
234 kfree(mmu_notifier_mm);
235out:
236 BUG_ON(atomic_read(&mm->mm_users) <= 0);
237 return ret;
238}
239
240/*
241 * Must not hold mmap_sem nor any other VM related lock when calling
242 * this registration function. Must also ensure mm_users can't go down
243 * to zero while this runs to avoid races with mmu_notifier_release,
244 * so mm has to be current->mm or the mm should be pinned safely such
245 * as with get_task_mm(). If the mm is not current->mm, the mm_users
246 * pin should be released by calling mmput after mmu_notifier_register
247 * returns. mmu_notifier_unregister must be always called to
248 * unregister the notifier. mm_count is automatically pinned to allow
249 * mmu_notifier_unregister to safely run at any time later, before or
250 * after exit_mmap. ->release will always be called before exit_mmap
251 * frees the pages.
252 */
253int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
254{
255 return do_mmu_notifier_register(mn, mm, 1);
256}
257EXPORT_SYMBOL_GPL(mmu_notifier_register);
258
259/*
260 * Same as mmu_notifier_register but here the caller must hold the
261 * mmap_sem in write mode.
262 */
263int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
264{
265 return do_mmu_notifier_register(mn, mm, 0);
266}
267EXPORT_SYMBOL_GPL(__mmu_notifier_register);
268
269/* this is called after the last mmu_notifier_unregister() returned */
270void __mmu_notifier_mm_destroy(struct mm_struct *mm)
271{
272 BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
273 kfree(mm->mmu_notifier_mm);
274 mm->mmu_notifier_mm = LIST_POISON1; /* debug */
275}
276
277/*
278 * This releases the mm_count pin automatically and frees the mm
279 * structure if it was the last user of it. It serializes against
280 * running mmu notifiers with SRCU and against mmu_notifier_unregister
281 * with the unregister lock + SRCU. All sptes must be dropped before
282 * calling mmu_notifier_unregister. ->release or any other notifier
283 * method may be invoked concurrently with mmu_notifier_unregister,
284 * and only after mmu_notifier_unregister returned we're guaranteed
285 * that ->release or any other method can't run anymore.
286 */
287void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
288{
289 BUG_ON(atomic_read(&mm->mm_count) <= 0);
290
291 if (!hlist_unhashed(&mn->hlist)) {
292 /*
293 * SRCU here will force exit_mmap to wait for ->release to
294 * finish before freeing the pages.
295 */
296 int id;
297
298 id = srcu_read_lock(&srcu);
299 /*
300 * exit_mmap will block in mmu_notifier_release to guarantee
301 * that ->release is called before freeing the pages.
302 */
303 if (mn->ops->release)
304 mn->ops->release(mn, mm);
305 srcu_read_unlock(&srcu, id);
306
307 spin_lock(&mm->mmu_notifier_mm->lock);
308 /*
309 * Can not use list_del_rcu() since __mmu_notifier_release
310 * can delete it before we hold the lock.
311 */
312 hlist_del_init_rcu(&mn->hlist);
313 spin_unlock(&mm->mmu_notifier_mm->lock);
314 }
315
316 /*
317 * Wait for any running method to finish, of course including
318 * ->release if it was run by mmu_notifier_release instead of us.
319 */
320 synchronize_srcu(&srcu);
321
322 BUG_ON(atomic_read(&mm->mm_count) <= 0);
323
324 mmdrop(mm);
325}
326EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
327
328static int __init mmu_notifier_init(void)
329{
330 return init_srcu_struct(&srcu);
331}
332subsys_initcall(mmu_notifier_init);
1/*
2 * linux/mm/mmu_notifier.c
3 *
4 * Copyright (C) 2008 Qumranet, Inc.
5 * Copyright (C) 2008 SGI
6 * Christoph Lameter <clameter@sgi.com>
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>
14#include <linux/export.h>
15#include <linux/mm.h>
16#include <linux/err.h>
17#include <linux/rcupdate.h>
18#include <linux/sched.h>
19#include <linux/slab.h>
20
21/*
22 * This function can't run concurrently against mmu_notifier_register
23 * because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
24 * runs with mm_users == 0. Other tasks may still invoke mmu notifiers
25 * in parallel despite there being no task using this mm any more,
26 * through the vmas outside of the exit_mmap context, such as with
27 * vmtruncate. This serializes against mmu_notifier_unregister with
28 * the mmu_notifier_mm->lock in addition to RCU and it serializes
29 * against the other mmu notifiers with RCU. struct mmu_notifier_mm
30 * can't go away from under us as exit_mmap holds an mm_count pin
31 * itself.
32 */
33void __mmu_notifier_release(struct mm_struct *mm)
34{
35 struct mmu_notifier *mn;
36 struct hlist_node *n;
37
38 /*
39 * RCU here will block mmu_notifier_unregister until
40 * ->release returns.
41 */
42 rcu_read_lock();
43 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist)
44 /*
45 * if ->release runs before mmu_notifier_unregister it
46 * must be handled as it's the only way for the driver
47 * to flush all existing sptes and stop the driver
48 * from establishing any more sptes before all the
49 * pages in the mm are freed.
50 */
51 if (mn->ops->release)
52 mn->ops->release(mn, mm);
53 rcu_read_unlock();
54
55 spin_lock(&mm->mmu_notifier_mm->lock);
56 while (unlikely(!hlist_empty(&mm->mmu_notifier_mm->list))) {
57 mn = hlist_entry(mm->mmu_notifier_mm->list.first,
58 struct mmu_notifier,
59 hlist);
60 /*
61 * We arrived before mmu_notifier_unregister so
62 * mmu_notifier_unregister will do nothing other than
63 * to wait ->release to finish and
64 * mmu_notifier_unregister to return.
65 */
66 hlist_del_init_rcu(&mn->hlist);
67 }
68 spin_unlock(&mm->mmu_notifier_mm->lock);
69
70 /*
71 * synchronize_rcu here prevents mmu_notifier_release to
72 * return to exit_mmap (which would proceed freeing all pages
73 * in the mm) until the ->release method returns, if it was
74 * invoked by mmu_notifier_unregister.
75 *
76 * The mmu_notifier_mm can't go away from under us because one
77 * mm_count is hold by exit_mmap.
78 */
79 synchronize_rcu();
80}
81
82/*
83 * If no young bitflag is supported by the hardware, ->clear_flush_young can
84 * unmap the address and return 1 or 0 depending if the mapping previously
85 * existed or not.
86 */
87int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
88 unsigned long address)
89{
90 struct mmu_notifier *mn;
91 struct hlist_node *n;
92 int young = 0;
93
94 rcu_read_lock();
95 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
96 if (mn->ops->clear_flush_young)
97 young |= mn->ops->clear_flush_young(mn, mm, address);
98 }
99 rcu_read_unlock();
100
101 return young;
102}
103
104int __mmu_notifier_test_young(struct mm_struct *mm,
105 unsigned long address)
106{
107 struct mmu_notifier *mn;
108 struct hlist_node *n;
109 int young = 0;
110
111 rcu_read_lock();
112 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
113 if (mn->ops->test_young) {
114 young = mn->ops->test_young(mn, mm, address);
115 if (young)
116 break;
117 }
118 }
119 rcu_read_unlock();
120
121 return young;
122}
123
124void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
125 pte_t pte)
126{
127 struct mmu_notifier *mn;
128 struct hlist_node *n;
129
130 rcu_read_lock();
131 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
132 if (mn->ops->change_pte)
133 mn->ops->change_pte(mn, mm, address, pte);
134 /*
135 * Some drivers don't have change_pte,
136 * so we must call invalidate_page in that case.
137 */
138 else if (mn->ops->invalidate_page)
139 mn->ops->invalidate_page(mn, mm, address);
140 }
141 rcu_read_unlock();
142}
143
144void __mmu_notifier_invalidate_page(struct mm_struct *mm,
145 unsigned long address)
146{
147 struct mmu_notifier *mn;
148 struct hlist_node *n;
149
150 rcu_read_lock();
151 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
152 if (mn->ops->invalidate_page)
153 mn->ops->invalidate_page(mn, mm, address);
154 }
155 rcu_read_unlock();
156}
157
158void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
159 unsigned long start, unsigned long end)
160{
161 struct mmu_notifier *mn;
162 struct hlist_node *n;
163
164 rcu_read_lock();
165 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
166 if (mn->ops->invalidate_range_start)
167 mn->ops->invalidate_range_start(mn, mm, start, end);
168 }
169 rcu_read_unlock();
170}
171
172void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
173 unsigned long start, unsigned long end)
174{
175 struct mmu_notifier *mn;
176 struct hlist_node *n;
177
178 rcu_read_lock();
179 hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list, hlist) {
180 if (mn->ops->invalidate_range_end)
181 mn->ops->invalidate_range_end(mn, mm, start, end);
182 }
183 rcu_read_unlock();
184}
185
186static int do_mmu_notifier_register(struct mmu_notifier *mn,
187 struct mm_struct *mm,
188 int take_mmap_sem)
189{
190 struct mmu_notifier_mm *mmu_notifier_mm;
191 int ret;
192
193 BUG_ON(atomic_read(&mm->mm_users) <= 0);
194
195 ret = -ENOMEM;
196 mmu_notifier_mm = kmalloc(sizeof(struct mmu_notifier_mm), GFP_KERNEL);
197 if (unlikely(!mmu_notifier_mm))
198 goto out;
199
200 if (take_mmap_sem)
201 down_write(&mm->mmap_sem);
202 ret = mm_take_all_locks(mm);
203 if (unlikely(ret))
204 goto out_cleanup;
205
206 if (!mm_has_notifiers(mm)) {
207 INIT_HLIST_HEAD(&mmu_notifier_mm->list);
208 spin_lock_init(&mmu_notifier_mm->lock);
209 mm->mmu_notifier_mm = mmu_notifier_mm;
210 mmu_notifier_mm = NULL;
211 }
212 atomic_inc(&mm->mm_count);
213
214 /*
215 * Serialize the update against mmu_notifier_unregister. A
216 * side note: mmu_notifier_release can't run concurrently with
217 * us because we hold the mm_users pin (either implicitly as
218 * current->mm or explicitly with get_task_mm() or similar).
219 * We can't race against any other mmu notifier method either
220 * thanks to mm_take_all_locks().
221 */
222 spin_lock(&mm->mmu_notifier_mm->lock);
223 hlist_add_head(&mn->hlist, &mm->mmu_notifier_mm->list);
224 spin_unlock(&mm->mmu_notifier_mm->lock);
225
226 mm_drop_all_locks(mm);
227out_cleanup:
228 if (take_mmap_sem)
229 up_write(&mm->mmap_sem);
230 /* kfree() does nothing if mmu_notifier_mm is NULL */
231 kfree(mmu_notifier_mm);
232out:
233 BUG_ON(atomic_read(&mm->mm_users) <= 0);
234 return ret;
235}
236
237/*
238 * Must not hold mmap_sem nor any other VM related lock when calling
239 * this registration function. Must also ensure mm_users can't go down
240 * to zero while this runs to avoid races with mmu_notifier_release,
241 * so mm has to be current->mm or the mm should be pinned safely such
242 * as with get_task_mm(). If the mm is not current->mm, the mm_users
243 * pin should be released by calling mmput after mmu_notifier_register
244 * returns. mmu_notifier_unregister must be always called to
245 * unregister the notifier. mm_count is automatically pinned to allow
246 * mmu_notifier_unregister to safely run at any time later, before or
247 * after exit_mmap. ->release will always be called before exit_mmap
248 * frees the pages.
249 */
250int mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
251{
252 return do_mmu_notifier_register(mn, mm, 1);
253}
254EXPORT_SYMBOL_GPL(mmu_notifier_register);
255
256/*
257 * Same as mmu_notifier_register but here the caller must hold the
258 * mmap_sem in write mode.
259 */
260int __mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
261{
262 return do_mmu_notifier_register(mn, mm, 0);
263}
264EXPORT_SYMBOL_GPL(__mmu_notifier_register);
265
266/* this is called after the last mmu_notifier_unregister() returned */
267void __mmu_notifier_mm_destroy(struct mm_struct *mm)
268{
269 BUG_ON(!hlist_empty(&mm->mmu_notifier_mm->list));
270 kfree(mm->mmu_notifier_mm);
271 mm->mmu_notifier_mm = LIST_POISON1; /* debug */
272}
273
274/*
275 * This releases the mm_count pin automatically and frees the mm
276 * structure if it was the last user of it. It serializes against
277 * running mmu notifiers with RCU and against mmu_notifier_unregister
278 * with the unregister lock + RCU. All sptes must be dropped before
279 * calling mmu_notifier_unregister. ->release or any other notifier
280 * method may be invoked concurrently with mmu_notifier_unregister,
281 * and only after mmu_notifier_unregister returned we're guaranteed
282 * that ->release or any other method can't run anymore.
283 */
284void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
285{
286 BUG_ON(atomic_read(&mm->mm_count) <= 0);
287
288 if (!hlist_unhashed(&mn->hlist)) {
289 /*
290 * RCU here will force exit_mmap to wait ->release to finish
291 * before freeing the pages.
292 */
293 rcu_read_lock();
294
295 /*
296 * exit_mmap will block in mmu_notifier_release to
297 * guarantee ->release is called before freeing the
298 * pages.
299 */
300 if (mn->ops->release)
301 mn->ops->release(mn, mm);
302 rcu_read_unlock();
303
304 spin_lock(&mm->mmu_notifier_mm->lock);
305 hlist_del_rcu(&mn->hlist);
306 spin_unlock(&mm->mmu_notifier_mm->lock);
307 }
308
309 /*
310 * Wait any running method to finish, of course including
311 * ->release if it was run by mmu_notifier_relase instead of us.
312 */
313 synchronize_rcu();
314
315 BUG_ON(atomic_read(&mm->mm_count) <= 0);
316
317 mmdrop(mm);
318}
319EXPORT_SYMBOL_GPL(mmu_notifier_unregister);