1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _LINUX_MMU_NOTIFIER_H 3 #define _LINUX_MMU_NOTIFIER_H 4 5 #include <linux/types.h> 6 #include <linux/list.h> 7 #include <linux/spinlock.h> 8 #include <linux/mm_types.h> 9 #include <linux/srcu.h> 10 11 struct mmu_notifier; 12 struct mmu_notifier_ops; 13 14 /* mmu_notifier_ops flags */ 15 #define MMU_INVALIDATE_DOES_NOT_BLOCK (0x01) 16 17 #ifdef CONFIG_MMU_NOTIFIER 18 19 /* 20 * The mmu notifier_mm structure is allocated and installed in 21 * mm->mmu_notifier_mm inside the mm_take_all_locks() protected 22 * critical section and it's released only when mm_count reaches zero 23 * in mmdrop(). 24 */ 25 struct mmu_notifier_mm { 26 /* all mmu notifiers registerd in this mm are queued in this list */ 27 struct hlist_head list; 28 /* to serialize the list modifications and hlist_unhashed */ 29 spinlock_t lock; 30 }; 31 32 struct mmu_notifier_ops { 33 /* 34 * Flags to specify behavior of callbacks for this MMU notifier. 35 * Used to determine which context an operation may be called. 36 * 37 * MMU_INVALIDATE_DOES_NOT_BLOCK: invalidate_range_* callbacks do not 38 * block 39 */ 40 int flags; 41 42 /* 43 * Called either by mmu_notifier_unregister or when the mm is 44 * being destroyed by exit_mmap, always before all pages are 45 * freed. This can run concurrently with other mmu notifier 46 * methods (the ones invoked outside the mm context) and it 47 * should tear down all secondary mmu mappings and freeze the 48 * secondary mmu. If this method isn't implemented you've to 49 * be sure that nothing could possibly write to the pages 50 * through the secondary mmu by the time the last thread with 51 * tsk->mm == mm exits. 52 * 53 * As side note: the pages freed after ->release returns could 54 * be immediately reallocated by the gart at an alias physical 55 * address with a different cache model, so if ->release isn't 56 * implemented because all _software_ driven memory accesses 57 * through the secondary mmu are terminated by the time the 58 * last thread of this mm quits, you've also to be sure that 59 * speculative _hardware_ operations can't allocate dirty 60 * cachelines in the cpu that could not be snooped and made 61 * coherent with the other read and write operations happening 62 * through the gart alias address, so leading to memory 63 * corruption. 64 */ 65 void (*release)(struct mmu_notifier *mn, 66 struct mm_struct *mm); 67 68 /* 69 * clear_flush_young is called after the VM is 70 * test-and-clearing the young/accessed bitflag in the 71 * pte. This way the VM will provide proper aging to the 72 * accesses to the page through the secondary MMUs and not 73 * only to the ones through the Linux pte. 74 * Start-end is necessary in case the secondary MMU is mapping the page 75 * at a smaller granularity than the primary MMU. 76 */ 77 int (*clear_flush_young)(struct mmu_notifier *mn, 78 struct mm_struct *mm, 79 unsigned long start, 80 unsigned long end); 81 82 /* 83 * clear_young is a lightweight version of clear_flush_young. Like the 84 * latter, it is supposed to test-and-clear the young/accessed bitflag 85 * in the secondary pte, but it may omit flushing the secondary tlb. 86 */ 87 int (*clear_young)(struct mmu_notifier *mn, 88 struct mm_struct *mm, 89 unsigned long start, 90 unsigned long end); 91 92 /* 93 * test_young is called to check the young/accessed bitflag in 94 * the secondary pte. This is used to know if the page is 95 * frequently used without actually clearing the flag or tearing 96 * down the secondary mapping on the page. 97 */ 98 int (*test_young)(struct mmu_notifier *mn, 99 struct mm_struct *mm, 100 unsigned long address); 101 102 /* 103 * change_pte is called in cases that pte mapping to page is changed: 104 * for example, when ksm remaps pte to point to a new shared page. 105 */ 106 void (*change_pte)(struct mmu_notifier *mn, 107 struct mm_struct *mm, 108 unsigned long address, 109 pte_t pte); 110 111 /* 112 * invalidate_range_start() and invalidate_range_end() must be 113 * paired and are called only when the mmap_sem and/or the 114 * locks protecting the reverse maps are held. If the subsystem 115 * can't guarantee that no additional references are taken to 116 * the pages in the range, it has to implement the 117 * invalidate_range() notifier to remove any references taken 118 * after invalidate_range_start(). 119 * 120 * Invalidation of multiple concurrent ranges may be 121 * optionally permitted by the driver. Either way the 122 * establishment of sptes is forbidden in the range passed to 123 * invalidate_range_begin/end for the whole duration of the 124 * invalidate_range_begin/end critical section. 125 * 126 * invalidate_range_start() is called when all pages in the 127 * range are still mapped and have at least a refcount of one. 128 * 129 * invalidate_range_end() is called when all pages in the 130 * range have been unmapped and the pages have been freed by 131 * the VM. 132 * 133 * The VM will remove the page table entries and potentially 134 * the page between invalidate_range_start() and 135 * invalidate_range_end(). If the page must not be freed 136 * because of pending I/O or other circumstances then the 137 * invalidate_range_start() callback (or the initial mapping 138 * by the driver) must make sure that the refcount is kept 139 * elevated. 140 * 141 * If the driver increases the refcount when the pages are 142 * initially mapped into an address space then either 143 * invalidate_range_start() or invalidate_range_end() may 144 * decrease the refcount. If the refcount is decreased on 145 * invalidate_range_start() then the VM can free pages as page 146 * table entries are removed. If the refcount is only 147 * droppped on invalidate_range_end() then the driver itself 148 * will drop the last refcount but it must take care to flush 149 * any secondary tlb before doing the final free on the 150 * page. Pages will no longer be referenced by the linux 151 * address space but may still be referenced by sptes until 152 * the last refcount is dropped. 153 * 154 * If both of these callbacks cannot block, and invalidate_range 155 * cannot block, mmu_notifier_ops.flags should have 156 * MMU_INVALIDATE_DOES_NOT_BLOCK set. 157 */ 158 void (*invalidate_range_start)(struct mmu_notifier *mn, 159 struct mm_struct *mm, 160 unsigned long start, unsigned long end); 161 void (*invalidate_range_end)(struct mmu_notifier *mn, 162 struct mm_struct *mm, 163 unsigned long start, unsigned long end); 164 165 /* 166 * invalidate_range() is either called between 167 * invalidate_range_start() and invalidate_range_end() when the 168 * VM has to free pages that where unmapped, but before the 169 * pages are actually freed, or outside of _start()/_end() when 170 * a (remote) TLB is necessary. 171 * 172 * If invalidate_range() is used to manage a non-CPU TLB with 173 * shared page-tables, it not necessary to implement the 174 * invalidate_range_start()/end() notifiers, as 175 * invalidate_range() alread catches the points in time when an 176 * external TLB range needs to be flushed. For more in depth 177 * discussion on this see Documentation/vm/mmu_notifier.txt 178 * 179 * Note that this function might be called with just a sub-range 180 * of what was passed to invalidate_range_start()/end(), if 181 * called between those functions. 182 * 183 * If this callback cannot block, and invalidate_range_{start,end} 184 * cannot block, mmu_notifier_ops.flags should have 185 * MMU_INVALIDATE_DOES_NOT_BLOCK set. 186 */ 187 void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm, 188 unsigned long start, unsigned long end); 189 }; 190 191 /* 192 * The notifier chains are protected by mmap_sem and/or the reverse map 193 * semaphores. Notifier chains are only changed when all reverse maps and 194 * the mmap_sem locks are taken. 195 * 196 * Therefore notifier chains can only be traversed when either 197 * 198 * 1. mmap_sem is held. 199 * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem). 200 * 3. No other concurrent thread can access the list (release) 201 */ 202 struct mmu_notifier { 203 struct hlist_node hlist; 204 const struct mmu_notifier_ops *ops; 205 }; 206 207 static inline int mm_has_notifiers(struct mm_struct *mm) 208 { 209 return unlikely(mm->mmu_notifier_mm); 210 } 211 212 extern int mmu_notifier_register(struct mmu_notifier *mn, 213 struct mm_struct *mm); 214 extern int __mmu_notifier_register(struct mmu_notifier *mn, 215 struct mm_struct *mm); 216 extern void mmu_notifier_unregister(struct mmu_notifier *mn, 217 struct mm_struct *mm); 218 extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn, 219 struct mm_struct *mm); 220 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm); 221 extern void __mmu_notifier_release(struct mm_struct *mm); 222 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm, 223 unsigned long start, 224 unsigned long end); 225 extern int __mmu_notifier_clear_young(struct mm_struct *mm, 226 unsigned long start, 227 unsigned long end); 228 extern int __mmu_notifier_test_young(struct mm_struct *mm, 229 unsigned long address); 230 extern void __mmu_notifier_change_pte(struct mm_struct *mm, 231 unsigned long address, pte_t pte); 232 extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm, 233 unsigned long start, unsigned long end); 234 extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm, 235 unsigned long start, unsigned long end, 236 bool only_end); 237 extern void __mmu_notifier_invalidate_range(struct mm_struct *mm, 238 unsigned long start, unsigned long end); 239 extern bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm); 240 241 static inline void mmu_notifier_release(struct mm_struct *mm) 242 { 243 if (mm_has_notifiers(mm)) 244 __mmu_notifier_release(mm); 245 } 246 247 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm, 248 unsigned long start, 249 unsigned long end) 250 { 251 if (mm_has_notifiers(mm)) 252 return __mmu_notifier_clear_flush_young(mm, start, end); 253 return 0; 254 } 255 256 static inline int mmu_notifier_clear_young(struct mm_struct *mm, 257 unsigned long start, 258 unsigned long end) 259 { 260 if (mm_has_notifiers(mm)) 261 return __mmu_notifier_clear_young(mm, start, end); 262 return 0; 263 } 264 265 static inline int mmu_notifier_test_young(struct mm_struct *mm, 266 unsigned long address) 267 { 268 if (mm_has_notifiers(mm)) 269 return __mmu_notifier_test_young(mm, address); 270 return 0; 271 } 272 273 static inline void mmu_notifier_change_pte(struct mm_struct *mm, 274 unsigned long address, pte_t pte) 275 { 276 if (mm_has_notifiers(mm)) 277 __mmu_notifier_change_pte(mm, address, pte); 278 } 279 280 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm, 281 unsigned long start, unsigned long end) 282 { 283 if (mm_has_notifiers(mm)) 284 __mmu_notifier_invalidate_range_start(mm, start, end); 285 } 286 287 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, 288 unsigned long start, unsigned long end) 289 { 290 if (mm_has_notifiers(mm)) 291 __mmu_notifier_invalidate_range_end(mm, start, end, false); 292 } 293 294 static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm, 295 unsigned long start, unsigned long end) 296 { 297 if (mm_has_notifiers(mm)) 298 __mmu_notifier_invalidate_range_end(mm, start, end, true); 299 } 300 301 static inline void mmu_notifier_invalidate_range(struct mm_struct *mm, 302 unsigned long start, unsigned long end) 303 { 304 if (mm_has_notifiers(mm)) 305 __mmu_notifier_invalidate_range(mm, start, end); 306 } 307 308 static inline void mmu_notifier_mm_init(struct mm_struct *mm) 309 { 310 mm->mmu_notifier_mm = NULL; 311 } 312 313 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm) 314 { 315 if (mm_has_notifiers(mm)) 316 __mmu_notifier_mm_destroy(mm); 317 } 318 319 #define ptep_clear_flush_young_notify(__vma, __address, __ptep) \ 320 ({ \ 321 int __young; \ 322 struct vm_area_struct *___vma = __vma; \ 323 unsigned long ___address = __address; \ 324 __young = ptep_clear_flush_young(___vma, ___address, __ptep); \ 325 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \ 326 ___address, \ 327 ___address + \ 328 PAGE_SIZE); \ 329 __young; \ 330 }) 331 332 #define pmdp_clear_flush_young_notify(__vma, __address, __pmdp) \ 333 ({ \ 334 int __young; \ 335 struct vm_area_struct *___vma = __vma; \ 336 unsigned long ___address = __address; \ 337 __young = pmdp_clear_flush_young(___vma, ___address, __pmdp); \ 338 __young |= mmu_notifier_clear_flush_young(___vma->vm_mm, \ 339 ___address, \ 340 ___address + \ 341 PMD_SIZE); \ 342 __young; \ 343 }) 344 345 #define ptep_clear_young_notify(__vma, __address, __ptep) \ 346 ({ \ 347 int __young; \ 348 struct vm_area_struct *___vma = __vma; \ 349 unsigned long ___address = __address; \ 350 __young = ptep_test_and_clear_young(___vma, ___address, __ptep);\ 351 __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \ 352 ___address + PAGE_SIZE); \ 353 __young; \ 354 }) 355 356 #define pmdp_clear_young_notify(__vma, __address, __pmdp) \ 357 ({ \ 358 int __young; \ 359 struct vm_area_struct *___vma = __vma; \ 360 unsigned long ___address = __address; \ 361 __young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\ 362 __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address, \ 363 ___address + PMD_SIZE); \ 364 __young; \ 365 }) 366 367 #define ptep_clear_flush_notify(__vma, __address, __ptep) \ 368 ({ \ 369 unsigned long ___addr = __address & PAGE_MASK; \ 370 struct mm_struct *___mm = (__vma)->vm_mm; \ 371 pte_t ___pte; \ 372 \ 373 ___pte = ptep_clear_flush(__vma, __address, __ptep); \ 374 mmu_notifier_invalidate_range(___mm, ___addr, \ 375 ___addr + PAGE_SIZE); \ 376 \ 377 ___pte; \ 378 }) 379 380 #define pmdp_huge_clear_flush_notify(__vma, __haddr, __pmd) \ 381 ({ \ 382 unsigned long ___haddr = __haddr & HPAGE_PMD_MASK; \ 383 struct mm_struct *___mm = (__vma)->vm_mm; \ 384 pmd_t ___pmd; \ 385 \ 386 ___pmd = pmdp_huge_clear_flush(__vma, __haddr, __pmd); \ 387 mmu_notifier_invalidate_range(___mm, ___haddr, \ 388 ___haddr + HPAGE_PMD_SIZE); \ 389 \ 390 ___pmd; \ 391 }) 392 393 #define pudp_huge_clear_flush_notify(__vma, __haddr, __pud) \ 394 ({ \ 395 unsigned long ___haddr = __haddr & HPAGE_PUD_MASK; \ 396 struct mm_struct *___mm = (__vma)->vm_mm; \ 397 pud_t ___pud; \ 398 \ 399 ___pud = pudp_huge_clear_flush(__vma, __haddr, __pud); \ 400 mmu_notifier_invalidate_range(___mm, ___haddr, \ 401 ___haddr + HPAGE_PUD_SIZE); \ 402 \ 403 ___pud; \ 404 }) 405 406 /* 407 * set_pte_at_notify() sets the pte _after_ running the notifier. 408 * This is safe to start by updating the secondary MMUs, because the primary MMU 409 * pte invalidate must have already happened with a ptep_clear_flush() before 410 * set_pte_at_notify() has been invoked. Updating the secondary MMUs first is 411 * required when we change both the protection of the mapping from read-only to 412 * read-write and the pfn (like during copy on write page faults). Otherwise the 413 * old page would remain mapped readonly in the secondary MMUs after the new 414 * page is already writable by some CPU through the primary MMU. 415 */ 416 #define set_pte_at_notify(__mm, __address, __ptep, __pte) \ 417 ({ \ 418 struct mm_struct *___mm = __mm; \ 419 unsigned long ___address = __address; \ 420 pte_t ___pte = __pte; \ 421 \ 422 mmu_notifier_change_pte(___mm, ___address, ___pte); \ 423 set_pte_at(___mm, ___address, __ptep, ___pte); \ 424 }) 425 426 extern void mmu_notifier_call_srcu(struct rcu_head *rcu, 427 void (*func)(struct rcu_head *rcu)); 428 extern void mmu_notifier_synchronize(void); 429 430 #else /* CONFIG_MMU_NOTIFIER */ 431 432 static inline int mm_has_notifiers(struct mm_struct *mm) 433 { 434 return 0; 435 } 436 437 static inline void mmu_notifier_release(struct mm_struct *mm) 438 { 439 } 440 441 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm, 442 unsigned long start, 443 unsigned long end) 444 { 445 return 0; 446 } 447 448 static inline int mmu_notifier_test_young(struct mm_struct *mm, 449 unsigned long address) 450 { 451 return 0; 452 } 453 454 static inline void mmu_notifier_change_pte(struct mm_struct *mm, 455 unsigned long address, pte_t pte) 456 { 457 } 458 459 static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm, 460 unsigned long start, unsigned long end) 461 { 462 } 463 464 static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm, 465 unsigned long start, unsigned long end) 466 { 467 } 468 469 static inline void mmu_notifier_invalidate_range_only_end(struct mm_struct *mm, 470 unsigned long start, unsigned long end) 471 { 472 } 473 474 static inline void mmu_notifier_invalidate_range(struct mm_struct *mm, 475 unsigned long start, unsigned long end) 476 { 477 } 478 479 static inline bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm) 480 { 481 return false; 482 } 483 484 static inline void mmu_notifier_mm_init(struct mm_struct *mm) 485 { 486 } 487 488 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm) 489 { 490 } 491 492 #define ptep_clear_flush_young_notify ptep_clear_flush_young 493 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young 494 #define ptep_clear_young_notify ptep_test_and_clear_young 495 #define pmdp_clear_young_notify pmdp_test_and_clear_young 496 #define ptep_clear_flush_notify ptep_clear_flush 497 #define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush 498 #define pudp_huge_clear_flush_notify pudp_huge_clear_flush 499 #define set_pte_at_notify set_pte_at 500 501 #endif /* CONFIG_MMU_NOTIFIER */ 502 503 #endif /* _LINUX_MMU_NOTIFIER_H */ 504