include/linux/mmu_notifier.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _LINUX_MMU_NOTIFIER_H
   3 #define _LINUX_MMU_NOTIFIER_H
   4
   5 #include <linux/list.h>
   6 #include <linux/spinlock.h>
   7 #include <linux/mm_types.h>
   8 #include <linux/srcu.h>
   9
  10 struct mmu_notifier;
  11 struct mmu_notifier_ops;
  12
  13 #ifdef CONFIG_MMU_NOTIFIER
  14
  15 /*
  16  * The mmu notifier_mm structure is allocated and installed in
  17  * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
  18  * critical section and it's released only when mm_count reaches zero
  19  * in mmdrop().
  20  */
  21 struct mmu_notifier_mm {
  22         /* all mmu notifiers registerd in this mm are queued in this list */
  23         struct hlist_head list;
  24         /* to serialize the list modifications and hlist_unhashed */
  25         spinlock_t lock;
  26 };
  27
  28 struct mmu_notifier_range {
  29         struct mm_struct *mm;
  30         unsigned long start;
  31         unsigned long end;
  32         bool blockable;
  33 };
  34
  35 struct mmu_notifier_ops {
  36         /*
  37          * Called either by mmu_notifier_unregister or when the mm is
  38          * being destroyed by exit_mmap, always before all pages are
  39          * freed. This can run concurrently with other mmu notifier
  40          * methods (the ones invoked outside the mm context) and it
  41          * should tear down all secondary mmu mappings and freeze the
  42          * secondary mmu. If this method isn't implemented you've to
  43          * be sure that nothing could possibly write to the pages
  44          * through the secondary mmu by the time the last thread with
  45          * tsk->mm == mm exits.
  46          *
  47          * As side note: the pages freed after ->release returns could
  48          * be immediately reallocated by the gart at an alias physical
  49          * address with a different cache model, so if ->release isn't
  50          * implemented because all _software_ driven memory accesses
  51          * through the secondary mmu are terminated by the time the
  52          * last thread of this mm quits, you've also to be sure that
  53          * speculative _hardware_ operations can't allocate dirty
  54          * cachelines in the cpu that could not be snooped and made
  55          * coherent with the other read and write operations happening
  56          * through the gart alias address, so leading to memory
  57          * corruption.
  58          */
  59         void (*release)(struct mmu_notifier *mn,
  60                         struct mm_struct *mm);
  61
  62         /*
  63          * clear_flush_young is called after the VM is
  64          * test-and-clearing the young/accessed bitflag in the
  65          * pte. This way the VM will provide proper aging to the
  66          * accesses to the page through the secondary MMUs and not
  67          * only to the ones through the Linux pte.
  68          * Start-end is necessary in case the secondary MMU is mapping the page
  69          * at a smaller granularity than the primary MMU.
  70          */
  71         int (*clear_flush_young)(struct mmu_notifier *mn,
  72                                  struct mm_struct *mm,
  73                                  unsigned long start,
  74                                  unsigned long end);
  75
  76         /*
  77          * clear_young is a lightweight version of clear_flush_young. Like the
  78          * latter, it is supposed to test-and-clear the young/accessed bitflag
  79          * in the secondary pte, but it may omit flushing the secondary tlb.
  80          */
  81         int (*clear_young)(struct mmu_notifier *mn,
  82                            struct mm_struct *mm,
  83                            unsigned long start,
  84                            unsigned long end);
  85
  86         /*
  87          * test_young is called to check the young/accessed bitflag in
  88          * the secondary pte. This is used to know if the page is
  89          * frequently used without actually clearing the flag or tearing
  90          * down the secondary mapping on the page.
  91          */
  92         int (*test_young)(struct mmu_notifier *mn,
  93                           struct mm_struct *mm,
  94                           unsigned long address);
  95
  96         /*
  97          * change_pte is called in cases that pte mapping to page is changed:
  98          * for example, when ksm remaps pte to point to a new shared page.
  99          */
 100         void (*change_pte)(struct mmu_notifier *mn,
 101                            struct mm_struct *mm,
 102                            unsigned long address,
 103                            pte_t pte);
 104
 105         /*
 106          * invalidate_range_start() and invalidate_range_end() must be
 107          * paired and are called only when the mmap_sem and/or the
 108          * locks protecting the reverse maps are held. If the subsystem
 109          * can't guarantee that no additional references are taken to
 110          * the pages in the range, it has to implement the
 111          * invalidate_range() notifier to remove any references taken
 112          * after invalidate_range_start().
 113          *
 114          * Invalidation of multiple concurrent ranges may be
 115          * optionally permitted by the driver. Either way the
 116          * establishment of sptes is forbidden in the range passed to
 117          * invalidate_range_begin/end for the whole duration of the
 118          * invalidate_range_begin/end critical section.
 119          *
 120          * invalidate_range_start() is called when all pages in the
 121          * range are still mapped and have at least a refcount of one.
 122          *
 123          * invalidate_range_end() is called when all pages in the
 124          * range have been unmapped and the pages have been freed by
 125          * the VM.
 126          *
 127          * The VM will remove the page table entries and potentially
 128          * the page between invalidate_range_start() and
 129          * invalidate_range_end(). If the page must not be freed
 130          * because of pending I/O or other circumstances then the
 131          * invalidate_range_start() callback (or the initial mapping
 132          * by the driver) must make sure that the refcount is kept
 133          * elevated.
 134          *
 135          * If the driver increases the refcount when the pages are
 136          * initially mapped into an address space then either
 137          * invalidate_range_start() or invalidate_range_end() may
 138          * decrease the refcount. If the refcount is decreased on
 139          * invalidate_range_start() then the VM can free pages as page
 140          * table entries are removed.  If the refcount is only
 141          * droppped on invalidate_range_end() then the driver itself
 142          * will drop the last refcount but it must take care to flush
 143          * any secondary tlb before doing the final free on the
 144          * page. Pages will no longer be referenced by the linux
 145          * address space but may still be referenced by sptes until
 146          * the last refcount is dropped.
 147          *
 148          * If blockable argument is set to false then the callback cannot
 149          * sleep and has to return with -EAGAIN. 0 should be returned
 150          * otherwise. Please note that if invalidate_range_start approves
 151          * a non-blocking behavior then the same applies to
 152          * invalidate_range_end.
 153          *
 154          */
 155         int (*invalidate_range_start)(struct mmu_notifier *mn,
 156                                       const struct mmu_notifier_range *range);
 157         void (*invalidate_range_end)(struct mmu_notifier *mn,
 158                                      const struct mmu_notifier_range *range);
 159
 160         /*
 161          * invalidate_range() is either called between
 162          * invalidate_range_start() and invalidate_range_end() when the
 163          * VM has to free pages that where unmapped, but before the
 164          * pages are actually freed, or outside of _start()/_end() when
 165          * a (remote) TLB is necessary.
 166          *
 167          * If invalidate_range() is used to manage a non-CPU TLB with
 168          * shared page-tables, it not necessary to implement the
 169          * invalidate_range_start()/end() notifiers, as
 170          * invalidate_range() alread catches the points in time when an
 171          * external TLB range needs to be flushed. For more in depth
 172          * discussion on this see Documentation/vm/mmu_notifier.rst
 173          *
 174          * Note that this function might be called with just a sub-range
 175          * of what was passed to invalidate_range_start()/end(), if
 176          * called between those functions.
 177          */
 178         void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
 179                                  unsigned long start, unsigned long end);
 180 };
 181
 182 /*
 183  * The notifier chains are protected by mmap_sem and/or the reverse map
 184  * semaphores. Notifier chains are only changed when all reverse maps and
 185  * the mmap_sem locks are taken.
 186  *
 187  * Therefore notifier chains can only be traversed when either
 188  *
 189  * 1. mmap_sem is held.
 190  * 2. One of the reverse map locks is held (i_mmap_rwsem or anon_vma->rwsem).
 191  * 3. No other concurrent thread can access the list (release)
 192  */
 193 struct mmu_notifier {
 194         struct hlist_node hlist;
 195         const struct mmu_notifier_ops *ops;
 196 };
 197
 198 static inline int mm_has_notifiers(struct mm_struct *mm)
 199 {
 200         return unlikely(mm->mmu_notifier_mm);
 201 }
 202
 203 extern int mmu_notifier_register(struct mmu_notifier *mn,
 204                                  struct mm_struct *mm);
 205 extern int __mmu_notifier_register(struct mmu_notifier *mn,
 206                                    struct mm_struct *mm);
 207 extern void mmu_notifier_unregister(struct mmu_notifier *mn,
 208                                     struct mm_struct *mm);
 209 extern void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
 210                                                struct mm_struct *mm);
 211 extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
 212 extern void __mmu_notifier_release(struct mm_struct *mm);
 213 extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
 214                                           unsigned long start,
 215                                           unsigned long end);
 216 extern int __mmu_notifier_clear_young(struct mm_struct *mm,
 217                                       unsigned long start,
 218                                       unsigned long end);
 219 extern int __mmu_notifier_test_young(struct mm_struct *mm,
 220                                      unsigned long address);
 221 extern void __mmu_notifier_change_pte(struct mm_struct *mm,
 222                                       unsigned long address, pte_t pte);
 223 extern int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *r);
 224 extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r,
 225                                   bool only_end);
 226 extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
 227                                   unsigned long start, unsigned long end);
 228
 229 static inline void mmu_notifier_release(struct mm_struct *mm)
 230 {
 231         if (mm_has_notifiers(mm))
 232                 __mmu_notifier_release(mm);
 233 }
 234
 235 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 236                                           unsigned long start,
 237                                           unsigned long end)
 238 {
 239         if (mm_has_notifiers(mm))
 240                 return __mmu_notifier_clear_flush_young(mm, start, end);
 241         return 0;
 242 }
 243
 244 static inline int mmu_notifier_clear_young(struct mm_struct *mm,
 245                                            unsigned long start,
 246                                            unsigned long end)
 247 {
 248         if (mm_has_notifiers(mm))
 249                 return __mmu_notifier_clear_young(mm, start, end);
 250         return 0;
 251 }
 252
 253 static inline int mmu_notifier_test_young(struct mm_struct *mm,
 254                                           unsigned long address)
 255 {
 256         if (mm_has_notifiers(mm))
 257                 return __mmu_notifier_test_young(mm, address);
 258         return 0;
 259 }
 260
 261 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
 262                                            unsigned long address, pte_t pte)
 263 {
 264         if (mm_has_notifiers(mm))
 265                 __mmu_notifier_change_pte(mm, address, pte);
 266 }
 267
 268 static inline void
 269 mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
 270 {
 271         if (mm_has_notifiers(range->mm)) {
 272                 range->blockable = true;
 273                 __mmu_notifier_invalidate_range_start(range);
 274         }
 275 }
 276
 277 static inline int
 278 mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
 279 {
 280         if (mm_has_notifiers(range->mm)) {
 281                 range->blockable = false;
 282                 return __mmu_notifier_invalidate_range_start(range);
 283         }
 284         return 0;
 285 }
 286
 287 static inline void
 288 mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
 289 {
 290         if (mm_has_notifiers(range->mm))
 291                 __mmu_notifier_invalidate_range_end(range, false);
 292 }
 293
 294 static inline void
 295 mmu_notifier_invalidate_range_only_end(struct mmu_notifier_range *range)
 296 {
 297         if (mm_has_notifiers(range->mm))
 298                 __mmu_notifier_invalidate_range_end(range, 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
 320 static inline void mmu_notifier_range_init(struct mmu_notifier_range *range,
 321                                            struct mm_struct *mm,
 322                                            unsigned long start,
 323                                            unsigned long end)
 324 {
 325         range->mm = mm;
 326         range->start = start;
 327         range->end = end;
 328 }
 329
 330 #define ptep_clear_flush_young_notify(__vma, __address, __ptep)         \
 331 ({                                                                      \
 332         int __young;                                                    \
 333         struct vm_area_struct *___vma = __vma;                          \
 334         unsigned long ___address = __address;                           \
 335         __young = ptep_clear_flush_young(___vma, ___address, __ptep);   \
 336         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
 337                                                   ___address,           \
 338                                                   ___address +          \
 339                                                         PAGE_SIZE);     \
 340         __young;                                                        \
 341 })
 342
 343 #define pmdp_clear_flush_young_notify(__vma, __address, __pmdp)         \
 344 ({                                                                      \
 345         int __young;                                                    \
 346         struct vm_area_struct *___vma = __vma;                          \
 347         unsigned long ___address = __address;                           \
 348         __young = pmdp_clear_flush_young(___vma, ___address, __pmdp);   \
 349         __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
 350                                                   ___address,           \
 351                                                   ___address +          \
 352                                                         PMD_SIZE);      \
 353         __young;                                                        \
 354 })
 355
 356 #define ptep_clear_young_notify(__vma, __address, __ptep)               \
 357 ({                                                                      \
 358         int __young;                                                    \
 359         struct vm_area_struct *___vma = __vma;                          \
 360         unsigned long ___address = __address;                           \
 361         __young = ptep_test_and_clear_young(___vma, ___address, __ptep);\
 362         __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,  \
 363                                             ___address + PAGE_SIZE);    \
 364         __young;                                                        \
 365 })
 366
 367 #define pmdp_clear_young_notify(__vma, __address, __pmdp)               \
 368 ({                                                                      \
 369         int __young;                                                    \
 370         struct vm_area_struct *___vma = __vma;                          \
 371         unsigned long ___address = __address;                           \
 372         __young = pmdp_test_and_clear_young(___vma, ___address, __pmdp);\
 373         __young |= mmu_notifier_clear_young(___vma->vm_mm, ___address,  \
 374                                             ___address + PMD_SIZE);     \
 375         __young;                                                        \
 376 })
 377
 378 #define ptep_clear_flush_notify(__vma, __address, __ptep)               \
 379 ({                                                                      \
 380         unsigned long ___addr = __address & PAGE_MASK;                  \
 381         struct mm_struct *___mm = (__vma)->vm_mm;                       \
 382         pte_t ___pte;                                                   \
 383                                                                         \
 384         ___pte = ptep_clear_flush(__vma, __address, __ptep);            \
 385         mmu_notifier_invalidate_range(___mm, ___addr,                   \
 386                                         ___addr + PAGE_SIZE);           \
 387                                                                         \
 388         ___pte;                                                         \
 389 })
 390
 391 #define pmdp_huge_clear_flush_notify(__vma, __haddr, __pmd)             \
 392 ({                                                                      \
 393         unsigned long ___haddr = __haddr & HPAGE_PMD_MASK;              \
 394         struct mm_struct *___mm = (__vma)->vm_mm;                       \
 395         pmd_t ___pmd;                                                   \
 396                                                                         \
 397         ___pmd = pmdp_huge_clear_flush(__vma, __haddr, __pmd);          \
 398         mmu_notifier_invalidate_range(___mm, ___haddr,                  \
 399                                       ___haddr + HPAGE_PMD_SIZE);       \
 400                                                                         \
 401         ___pmd;                                                         \
 402 })
 403
 404 #define pudp_huge_clear_flush_notify(__vma, __haddr, __pud)             \
 405 ({                                                                      \
 406         unsigned long ___haddr = __haddr & HPAGE_PUD_MASK;              \
 407         struct mm_struct *___mm = (__vma)->vm_mm;                       \
 408         pud_t ___pud;                                                   \
 409                                                                         \
 410         ___pud = pudp_huge_clear_flush(__vma, __haddr, __pud);          \
 411         mmu_notifier_invalidate_range(___mm, ___haddr,                  \
 412                                       ___haddr + HPAGE_PUD_SIZE);       \
 413                                                                         \
 414         ___pud;                                                         \
 415 })
 416
 417 /*
 418  * set_pte_at_notify() sets the pte _after_ running the notifier.
 419  * This is safe to start by updating the secondary MMUs, because the primary MMU
 420  * pte invalidate must have already happened with a ptep_clear_flush() before
 421  * set_pte_at_notify() has been invoked.  Updating the secondary MMUs first is
 422  * required when we change both the protection of the mapping from read-only to
 423  * read-write and the pfn (like during copy on write page faults). Otherwise the
 424  * old page would remain mapped readonly in the secondary MMUs after the new
 425  * page is already writable by some CPU through the primary MMU.
 426  */
 427 #define set_pte_at_notify(__mm, __address, __ptep, __pte)               \
 428 ({                                                                      \
 429         struct mm_struct *___mm = __mm;                                 \
 430         unsigned long ___address = __address;                           \
 431         pte_t ___pte = __pte;                                           \
 432                                                                         \
 433         mmu_notifier_change_pte(___mm, ___address, ___pte);             \
 434         set_pte_at(___mm, ___address, __ptep, ___pte);                  \
 435 })
 436
 437 extern void mmu_notifier_call_srcu(struct rcu_head *rcu,
 438                                    void (*func)(struct rcu_head *rcu));
 439
 440 #else /* CONFIG_MMU_NOTIFIER */
 441
 442 struct mmu_notifier_range {
 443         unsigned long start;
 444         unsigned long end;
 445 };
 446
 447 static inline void _mmu_notifier_range_init(struct mmu_notifier_range *range,
 448                                             unsigned long start,
 449                                             unsigned long end)
 450 {
 451         range->start = start;
 452         range->end = end;
 453 }
 454
 455 #define mmu_notifier_range_init(range, mm, start, end) \
 456         _mmu_notifier_range_init(range, start, end)
 457
 458
 459 static inline int mm_has_notifiers(struct mm_struct *mm)
 460 {
 461         return 0;
 462 }
 463
 464 static inline void mmu_notifier_release(struct mm_struct *mm)
 465 {
 466 }
 467
 468 static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
 469                                           unsigned long start,
 470                                           unsigned long end)
 471 {
 472         return 0;
 473 }
 474
 475 static inline int mmu_notifier_test_young(struct mm_struct *mm,
 476                                           unsigned long address)
 477 {
 478         return 0;
 479 }
 480
 481 static inline void mmu_notifier_change_pte(struct mm_struct *mm,
 482                                            unsigned long address, pte_t pte)
 483 {
 484 }
 485
 486 static inline void
 487 mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
 488 {
 489 }
 490
 491 static inline int
 492 mmu_notifier_invalidate_range_start_nonblock(struct mmu_notifier_range *range)
 493 {
 494         return 0;
 495 }
 496
 497 static inline
 498 void mmu_notifier_invalidate_range_end(struct mmu_notifier_range *range)
 499 {
 500 }
 501
 502 static inline void
 503 mmu_notifier_invalidate_range_only_end(struct mmu_notifier_range *range)
 504 {
 505 }
 506
 507 static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
 508                                   unsigned long start, unsigned long end)
 509 {
 510 }
 511
 512 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 513 {
 514 }
 515
 516 static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 517 {
 518 }
 519
 520 #define ptep_clear_flush_young_notify ptep_clear_flush_young
 521 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young
 522 #define ptep_clear_young_notify ptep_test_and_clear_young
 523 #define pmdp_clear_young_notify pmdp_test_and_clear_young
 524 #define ptep_clear_flush_notify ptep_clear_flush
 525 #define pmdp_huge_clear_flush_notify pmdp_huge_clear_flush
 526 #define pudp_huge_clear_flush_notify pudp_huge_clear_flush
 527 #define set_pte_at_notify set_pte_at
 528
 529 #endif /* CONFIG_MMU_NOTIFIER */
 530
 531 #endif /* _LINUX_MMU_NOTIFIER_H */