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1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef _LINUX_MMU_NOTIFIER_H3#define _LINUX_MMU_NOTIFIER_H4 5#include <linux/list.h>6#include <linux/spinlock.h>7#include <linux/mm_types.h>8#include <linux/mmap_lock.h>9#include <linux/srcu.h>10#include <linux/interval_tree.h>11 12struct mmu_notifier_subscriptions;13struct mmu_notifier;14struct mmu_notifier_range;15struct mmu_interval_notifier;16 17/**18 * enum mmu_notifier_event - reason for the mmu notifier callback19 * @MMU_NOTIFY_UNMAP: either munmap() that unmap the range or a mremap() that20 * move the range21 *22 * @MMU_NOTIFY_CLEAR: clear page table entry (many reasons for this like23 * madvise() or replacing a page by another one, ...).24 *25 * @MMU_NOTIFY_PROTECTION_VMA: update is due to protection change for the range26 * ie using the vma access permission (vm_page_prot) to update the whole range27 * is enough no need to inspect changes to the CPU page table (mprotect()28 * syscall)29 *30 * @MMU_NOTIFY_PROTECTION_PAGE: update is due to change in read/write flag for31 * pages in the range so to mirror those changes the user must inspect the CPU32 * page table (from the end callback).33 *34 * @MMU_NOTIFY_SOFT_DIRTY: soft dirty accounting (still same page and same35 * access flags). User should soft dirty the page in the end callback to make36 * sure that anyone relying on soft dirtiness catch pages that might be written37 * through non CPU mappings.38 *39 * @MMU_NOTIFY_RELEASE: used during mmu_interval_notifier invalidate to signal40 * that the mm refcount is zero and the range is no longer accessible.41 *42 * @MMU_NOTIFY_MIGRATE: used during migrate_vma_collect() invalidate to signal43 * a device driver to possibly ignore the invalidation if the44 * owner field matches the driver's device private pgmap owner.45 *46 * @MMU_NOTIFY_EXCLUSIVE: to signal a device driver that the device will no47 * longer have exclusive access to the page. When sent during creation of an48 * exclusive range the owner will be initialised to the value provided by the49 * caller of make_device_exclusive_range(), otherwise the owner will be NULL.50 */51enum mmu_notifier_event {52 MMU_NOTIFY_UNMAP = 0,53 MMU_NOTIFY_CLEAR,54 MMU_NOTIFY_PROTECTION_VMA,55 MMU_NOTIFY_PROTECTION_PAGE,56 MMU_NOTIFY_SOFT_DIRTY,57 MMU_NOTIFY_RELEASE,58 MMU_NOTIFY_MIGRATE,59 MMU_NOTIFY_EXCLUSIVE,60};61 62#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)63 64struct mmu_notifier_ops {65 /*66 * Called either by mmu_notifier_unregister or when the mm is67 * being destroyed by exit_mmap, always before all pages are68 * freed. This can run concurrently with other mmu notifier69 * methods (the ones invoked outside the mm context) and it70 * should tear down all secondary mmu mappings and freeze the71 * secondary mmu. If this method isn't implemented you've to72 * be sure that nothing could possibly write to the pages73 * through the secondary mmu by the time the last thread with74 * tsk->mm == mm exits.75 *76 * As side note: the pages freed after ->release returns could77 * be immediately reallocated by the gart at an alias physical78 * address with a different cache model, so if ->release isn't79 * implemented because all _software_ driven memory accesses80 * through the secondary mmu are terminated by the time the81 * last thread of this mm quits, you've also to be sure that82 * speculative _hardware_ operations can't allocate dirty83 * cachelines in the cpu that could not be snooped and made84 * coherent with the other read and write operations happening85 * through the gart alias address, so leading to memory86 * corruption.87 */88 void (*release)(struct mmu_notifier *subscription,89 struct mm_struct *mm);90 91 /*92 * clear_flush_young is called after the VM is93 * test-and-clearing the young/accessed bitflag in the94 * pte. This way the VM will provide proper aging to the95 * accesses to the page through the secondary MMUs and not96 * only to the ones through the Linux pte.97 * Start-end is necessary in case the secondary MMU is mapping the page98 * at a smaller granularity than the primary MMU.99 */100 int (*clear_flush_young)(struct mmu_notifier *subscription,101 struct mm_struct *mm,102 unsigned long start,103 unsigned long end);104 105 /*106 * clear_young is a lightweight version of clear_flush_young. Like the107 * latter, it is supposed to test-and-clear the young/accessed bitflag108 * in the secondary pte, but it may omit flushing the secondary tlb.109 */110 int (*clear_young)(struct mmu_notifier *subscription,111 struct mm_struct *mm,112 unsigned long start,113 unsigned long end);114 115 /*116 * test_young is called to check the young/accessed bitflag in117 * the secondary pte. This is used to know if the page is118 * frequently used without actually clearing the flag or tearing119 * down the secondary mapping on the page.120 */121 int (*test_young)(struct mmu_notifier *subscription,122 struct mm_struct *mm,123 unsigned long address);124 125 /*126 * invalidate_range_start() and invalidate_range_end() must be127 * paired and are called only when the mmap_lock and/or the128 * locks protecting the reverse maps are held. If the subsystem129 * can't guarantee that no additional references are taken to130 * the pages in the range, it has to implement the131 * invalidate_range() notifier to remove any references taken132 * after invalidate_range_start().133 *134 * Invalidation of multiple concurrent ranges may be135 * optionally permitted by the driver. Either way the136 * establishment of sptes is forbidden in the range passed to137 * invalidate_range_begin/end for the whole duration of the138 * invalidate_range_begin/end critical section.139 *140 * invalidate_range_start() is called when all pages in the141 * range are still mapped and have at least a refcount of one.142 *143 * invalidate_range_end() is called when all pages in the144 * range have been unmapped and the pages have been freed by145 * the VM.146 *147 * The VM will remove the page table entries and potentially148 * the page between invalidate_range_start() and149 * invalidate_range_end(). If the page must not be freed150 * because of pending I/O or other circumstances then the151 * invalidate_range_start() callback (or the initial mapping152 * by the driver) must make sure that the refcount is kept153 * elevated.154 *155 * If the driver increases the refcount when the pages are156 * initially mapped into an address space then either157 * invalidate_range_start() or invalidate_range_end() may158 * decrease the refcount. If the refcount is decreased on159 * invalidate_range_start() then the VM can free pages as page160 * table entries are removed. If the refcount is only161 * dropped on invalidate_range_end() then the driver itself162 * will drop the last refcount but it must take care to flush163 * any secondary tlb before doing the final free on the164 * page. Pages will no longer be referenced by the linux165 * address space but may still be referenced by sptes until166 * the last refcount is dropped.167 *168 * If blockable argument is set to false then the callback cannot169 * sleep and has to return with -EAGAIN if sleeping would be required.170 * 0 should be returned otherwise. Please note that notifiers that can171 * fail invalidate_range_start are not allowed to implement172 * invalidate_range_end, as there is no mechanism for informing the173 * notifier that its start failed.174 */175 int (*invalidate_range_start)(struct mmu_notifier *subscription,176 const struct mmu_notifier_range *range);177 void (*invalidate_range_end)(struct mmu_notifier *subscription,178 const struct mmu_notifier_range *range);179 180 /*181 * arch_invalidate_secondary_tlbs() is used to manage a non-CPU TLB182 * which shares page-tables with the CPU. The183 * invalidate_range_start()/end() callbacks should not be implemented as184 * invalidate_secondary_tlbs() already catches the points in time when185 * an external TLB needs to be flushed.186 *187 * This requires arch_invalidate_secondary_tlbs() to be called while188 * holding the ptl spin-lock and therefore this callback is not allowed189 * to sleep.190 *191 * This is called by architecture code whenever invalidating a TLB192 * entry. It is assumed that any secondary TLB has the same rules for193 * when invalidations are required. If this is not the case architecture194 * code will need to call this explicitly when required for secondary195 * TLB invalidation.196 */197 void (*arch_invalidate_secondary_tlbs)(198 struct mmu_notifier *subscription,199 struct mm_struct *mm,200 unsigned long start,201 unsigned long end);202 203 /*204 * These callbacks are used with the get/put interface to manage the205 * lifetime of the mmu_notifier memory. alloc_notifier() returns a new206 * notifier for use with the mm.207 *208 * free_notifier() is only called after the mmu_notifier has been209 * fully put, calls to any ops callback are prevented and no ops210 * callbacks are currently running. It is called from a SRCU callback211 * and cannot sleep.212 */213 struct mmu_notifier *(*alloc_notifier)(struct mm_struct *mm);214 void (*free_notifier)(struct mmu_notifier *subscription);215};216 217/*218 * The notifier chains are protected by mmap_lock and/or the reverse map219 * semaphores. Notifier chains are only changed when all reverse maps and220 * the mmap_lock locks are taken.221 *222 * Therefore notifier chains can only be traversed when either223 *224 * 1. mmap_lock is held.225 * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem).226 * 3. No other concurrent thread can access the list (release)227 */228struct mmu_notifier {229 struct hlist_node hlist;230 const struct mmu_notifier_ops *ops;231 struct mm_struct *mm;232 struct rcu_head rcu;233 unsigned int users;234};235 236/**237 * struct mmu_interval_notifier_ops238 * @invalidate: Upon return the caller must stop using any SPTEs within this239 * range. This function can sleep. Return false only if sleeping240 * was required but mmu_notifier_range_blockable(range) is false.241 */242struct mmu_interval_notifier_ops {243 bool (*invalidate)(struct mmu_interval_notifier *interval_sub,244 const struct mmu_notifier_range *range,245 unsigned long cur_seq);246};247 248struct mmu_interval_notifier {249 struct interval_tree_node interval_tree;250 const struct mmu_interval_notifier_ops *ops;251 struct mm_struct *mm;252 struct hlist_node deferred_item;253 unsigned long invalidate_seq;254};255 256#ifdef CONFIG_MMU_NOTIFIER257 258#ifdef CONFIG_LOCKDEP259extern struct lockdep_map __mmu_notifier_invalidate_range_start_map;260#endif261 262struct mmu_notifier_range {263 struct mm_struct *mm;264 unsigned long start;265 unsigned long end;266 unsigned flags;267 enum mmu_notifier_event event;268 void *owner;269};270 271static inline int mm_has_notifiers(struct mm_struct *mm)272{273 return unlikely(mm->notifier_subscriptions);274}275 276struct mmu_notifier *mmu_notifier_get_locked(const struct mmu_notifier_ops *ops,277 struct mm_struct *mm);278static inline struct mmu_notifier *279mmu_notifier_get(const struct mmu_notifier_ops *ops, struct mm_struct *mm)280{281 struct mmu_notifier *ret;282 283 mmap_write_lock(mm);284 ret = mmu_notifier_get_locked(ops, mm);285 mmap_write_unlock(mm);286 return ret;287}288void mmu_notifier_put(struct mmu_notifier *subscription);289void mmu_notifier_synchronize(void);290 291extern int mmu_notifier_register(struct mmu_notifier *subscription,292 struct mm_struct *mm);293extern int __mmu_notifier_register(struct mmu_notifier *subscription,294 struct mm_struct *mm);295extern void mmu_notifier_unregister(struct mmu_notifier *subscription,296 struct mm_struct *mm);297 298unsigned long299mmu_interval_read_begin(struct mmu_interval_notifier *interval_sub);300int mmu_interval_notifier_insert(struct mmu_interval_notifier *interval_sub,301 struct mm_struct *mm, unsigned long start,302 unsigned long length,303 const struct mmu_interval_notifier_ops *ops);304int mmu_interval_notifier_insert_locked(305 struct mmu_interval_notifier *interval_sub, struct mm_struct *mm,306 unsigned long start, unsigned long length,307 const struct mmu_interval_notifier_ops *ops);308void mmu_interval_notifier_remove(struct mmu_interval_notifier *interval_sub);309 310/**311 * mmu_interval_set_seq - Save the invalidation sequence312 * @interval_sub - The subscription passed to invalidate313 * @cur_seq - The cur_seq passed to the invalidate() callback314 *315 * This must be called unconditionally from the invalidate callback of a316 * struct mmu_interval_notifier_ops under the same lock that is used to call317 * mmu_interval_read_retry(). It updates the sequence number for later use by318 * mmu_interval_read_retry(). The provided cur_seq will always be odd.319 *320 * If the caller does not call mmu_interval_read_begin() or321 * mmu_interval_read_retry() then this call is not required.322 */323static inline void324mmu_interval_set_seq(struct mmu_interval_notifier *interval_sub,325 unsigned long cur_seq)326{327 WRITE_ONCE(interval_sub->invalidate_seq, cur_seq);328}329 330/**331 * mmu_interval_read_retry - End a read side critical section against a VA range332 * interval_sub: The subscription333 * seq: The return of the paired mmu_interval_read_begin()334 *335 * This MUST be called under a user provided lock that is also held336 * unconditionally by op->invalidate() when it calls mmu_interval_set_seq().337 *338 * Each call should be paired with a single mmu_interval_read_begin() and339 * should be used to conclude the read side.340 *341 * Returns true if an invalidation collided with this critical section, and342 * the caller should retry.343 */344static inline bool345mmu_interval_read_retry(struct mmu_interval_notifier *interval_sub,346 unsigned long seq)347{348 return interval_sub->invalidate_seq != seq;349}350 351/**352 * mmu_interval_check_retry - Test if a collision has occurred353 * interval_sub: The subscription354 * seq: The return of the matching mmu_interval_read_begin()355 *356 * This can be used in the critical section between mmu_interval_read_begin()357 * and mmu_interval_read_retry(). A return of true indicates an invalidation358 * has collided with this critical region and a future359 * mmu_interval_read_retry() will return true.360 *361 * False is not reliable and only suggests a collision may not have362 * occurred. It can be called many times and does not have to hold the user363 * provided lock.364 *365 * This call can be used as part of loops and other expensive operations to366 * expedite a retry.367 */368static inline bool369mmu_interval_check_retry(struct mmu_interval_notifier *interval_sub,370 unsigned long seq)371{372 /* Pairs with the WRITE_ONCE in mmu_interval_set_seq() */373 return READ_ONCE(interval_sub->invalidate_seq) != seq;374}375 376extern void __mmu_notifier_subscriptions_destroy(struct mm_struct *mm);377extern void __mmu_notifier_release(struct mm_struct *mm);378extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,379 unsigned long start,380 unsigned long end);381extern int __mmu_notifier_clear_young(struct mm_struct *mm,382 unsigned long start,383 unsigned long end);384extern int __mmu_notifier_test_young(struct mm_struct *mm,385 unsigned long address);386extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r);387extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r);388extern void __mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,389 unsigned long start, unsigned long end);390extern bool391mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range *range);392 393static inline bool394mmu_notifier_range_blockable(const struct mmu_notifier_range *range)395{396 return (range->flags & MMU_NOTIFIER_RANGE_BLOCKABLE);397}398 399static inline void mmu_notifier_release(struct mm_struct *mm)400{401 if (mm_has_notifiers(mm))402 __mmu_notifier_release(mm);403}404 405static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,406 unsigned long start,407 unsigned long end)408{409 if (mm_has_notifiers(mm))410 return __mmu_notifier_clear_flush_young(mm, start, end);411 return 0;412}413 414static inline int mmu_notifier_clear_young(struct mm_struct *mm,415 unsigned long start,416 unsigned long end)417{418 if (mm_has_notifiers(mm))419 return __mmu_notifier_clear_young(mm, start, end);420 return 0;421}422 423static inline int mmu_notifier_test_young(struct mm_struct *mm,424 unsigned long address)425{426 if (mm_has_notifiers(mm))427 return __mmu_notifier_test_young(mm, address);428 return 0;429}430 431static inline void432mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)433{434 might_sleep();435 436 lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);437 if (mm_has_notifiers(range->mm)) {438 range->flags |= MMU_NOTIFIER_RANGE_BLOCKABLE;439 __mmu_notifier_invalidate_range_start(range);440 }441 lock_map_release(&__mmu_notifier_invalidate_range_start_map);442}443 444/*445 * This version of mmu_notifier_invalidate_range_start() avoids blocking, but it446 * can return an error if a notifier can't proceed without blocking, in which447 * case you're not allowed to modify PTEs in the specified range.448 *449 * This is mainly intended for OOM handling.450 */451static inline int __must_check452mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)453{454 int ret = 0;455 456 lock_map_acquire(&__mmu_notifier_invalidate_range_start_map);457 if (mm_has_notifiers(range->mm)) {458 range->flags &= ~MMU_NOTIFIER_RANGE_BLOCKABLE;459 ret = __mmu_notifier_invalidate_range_start(range);460 }461 lock_map_release(&__mmu_notifier_invalidate_range_start_map);462 return ret;463}464 465static inline void466mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)467{468 if (mmu_notifier_range_blockable(range))469 might_sleep();470 471 if (mm_has_notifiers(range->mm))472 __mmu_notifier_invalidate_range_end(range);473}474 475static inline void mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,476 unsigned long start, unsigned long end)477{478 if (mm_has_notifiers(mm))479 __mmu_notifier_arch_invalidate_secondary_tlbs(mm, start, end);480}481 482static inline void mmu_notifier_subscriptions_init(struct mm_struct *mm)483{484 mm->notifier_subscriptions = NULL;485}486 487static inline void mmu_notifier_subscriptions_destroy(struct mm_struct *mm)488{489 if (mm_has_notifiers(mm))490 __mmu_notifier_subscriptions_destroy(mm);491}492 493 494static inline void mmu_notifier_range_init(struct mmu_notifier_range *range,495 enum mmu_notifier_event event,496 unsigned flags,497 struct mm_struct *mm,498 unsigned long start,499 unsigned long end)500{501 range->event = event;502 range->mm = mm;503 range->start = start;504 range->end = end;505 range->flags = flags;506}507 508static inline void mmu_notifier_range_init_owner(509 struct mmu_notifier_range *range,510 enum mmu_notifier_event event, unsigned int flags,511 struct mm_struct *mm, unsigned long start,512 unsigned long end, void *owner)513{514 mmu_notifier_range_init(range, event, flags, mm, start, end);515 range->owner = owner;516}517 518#define ptep_clear_flush_young_notify(__vma, __address, __ptep) \519({ \520 int __young; \521 struct vm_area_struct *___vma = __vma; \522 unsigned long ___address = __address; \523 __young = ptep_clear_flush_young(___vma, ___address, __ptep); \524 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \525 ___address, \526 ___address + \527 PAGE_SIZE); \528 __young; \529})530 531#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp) \532({ \533 int __young; \534 struct vm_area_struct *___vma = __vma; \535 unsigned long ___address = __address; \536 __young = pmdp_clear_flush_young(___vma, ___address, __pmdp); \537 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \538 ___address, \539 ___address + \540 PMD_SIZE); \541 __young; \542})543 544#define ptep_clear_young_notify(__vma, __address, __ptep) \545({ \546 int __young; \547 struct vm_area_struct *___vma = __vma; \548 unsigned long ___address = __address; \549 __young = ptep_test_and_clear_young(___vma, ___address, __ptep);\550 __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \551 ___address + PAGE_SIZE); \552 __young; \553})554 555#define pmdp_clear_young_notify(__vma, __address, __pmdp) \556({ \557 int __young; \558 struct vm_area_struct *___vma = __vma; \559 unsigned long ___address = __address; \560 __young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\561 __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \562 ___address + PMD_SIZE); \563 __young; \564})565 566#else /* CONFIG_MMU_NOTIFIER */567 568struct mmu_notifier_range {569 unsigned long start;570 unsigned long end;571};572 573static inline void _mmu_notifier_range_init(struct mmu_notifier_range *range,574 unsigned long start,575 unsigned long end)576{577 range->start = start;578 range->end = end;579}580 581#define mmu_notifier_range_init(range,event,flags,mm,start,end) \582 _mmu_notifier_range_init(range, start, end)583#define mmu_notifier_range_init_owner(range, event, flags, mm, start, \584 end, owner) \585 _mmu_notifier_range_init(range, start, end)586 587static inline bool588mmu_notifier_range_blockable(const struct mmu_notifier_range *range)589{590 return true;591}592 593static inline int mm_has_notifiers(struct mm_struct *mm)594{595 return 0;596}597 598static inline void mmu_notifier_release(struct mm_struct *mm)599{600}601 602static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,603 unsigned long start,604 unsigned long end)605{606 return 0;607}608 609static inline int mmu_notifier_test_young(struct mm_struct *mm,610 unsigned long address)611{612 return 0;613}614 615static inline void616mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)617{618}619 620static inline int621mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)622{623 return 0;624}625 626static inline627void mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)628{629}630 631static inline void mmu_notifier_arch_invalidate_secondary_tlbs(struct mm_struct *mm,632 unsigned long start, unsigned long end)633{634}635 636static inline void mmu_notifier_subscriptions_init(struct mm_struct *mm)637{638}639 640static inline void mmu_notifier_subscriptions_destroy(struct mm_struct *mm)641{642}643 644#define mmu_notifier_range_update_to_read_only(r) false645 646#define ptep_clear_flush_young_notify ptep_clear_flush_young647#define pmdp_clear_flush_young_notify pmdp_clear_flush_young648#define ptep_clear_young_notify ptep_test_and_clear_young649#define pmdp_clear_young_notify pmdp_test_and_clear_young650#define ptep_clear_flush_notify ptep_clear_flush651#define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush652#define pudp_huge_clear_flush_notify pudp_huge_clear_flush653 654static inline void mmu_notifier_synchronize(void)655{656}657 658#endif /* CONFIG_MMU_NOTIFIER */659 660#endif /* _LINUX_MMU_NOTIFIER_H */661