1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * mm/pgtable-generic.c 4 * 5 * Generic pgtable methods declared in linux/pgtable.h 6 * 7 * Copyright (C) 2010 Linus Torvalds 8 */ 9 10 #include <linux/pagemap.h> 11 #include <linux/hugetlb.h> 12 #include <linux/pgtable.h> 13 #include <linux/swap.h> 14 #include <linux/swapops.h> 15 #include <linux/mm_inline.h> 16 #include <asm/pgalloc.h> 17 #include <asm/tlb.h> 18 19 /* 20 * If a p?d_bad entry is found while walking page tables, report 21 * the error, before resetting entry to p?d_none. Usually (but 22 * very seldom) called out from the p?d_none_or_clear_bad macros. 23 */ 24 25 void pgd_clear_bad(pgd_t *pgd) 26 { 27 pgd_ERROR(*pgd); 28 pgd_clear(pgd); 29 } 30 31 #ifndef __PAGETABLE_P4D_FOLDED 32 void p4d_clear_bad(p4d_t *p4d) 33 { 34 p4d_ERROR(*p4d); 35 p4d_clear(p4d); 36 } 37 #endif 38 39 #ifndef __PAGETABLE_PUD_FOLDED 40 void pud_clear_bad(pud_t *pud) 41 { 42 pud_ERROR(*pud); 43 pud_clear(pud); 44 } 45 #endif 46 47 /* 48 * Note that the pmd variant below can't be stub'ed out just as for p4d/pud 49 * above. pmd folding is special and typically pmd_* macros refer to upper 50 * level even when folded 51 */ 52 void pmd_clear_bad(pmd_t *pmd) 53 { 54 pmd_ERROR(*pmd); 55 pmd_clear(pmd); 56 } 57 58 #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS 59 /* 60 * Only sets the access flags (dirty, accessed), as well as write 61 * permission. Furthermore, we know it always gets set to a "more 62 * permissive" setting, which allows most architectures to optimize 63 * this. We return whether the PTE actually changed, which in turn 64 * instructs the caller to do things like update__mmu_cache. This 65 * used to be done in the caller, but sparc needs minor faults to 66 * force that call on sun4c so we changed this macro slightly 67 */ 68 int ptep_set_access_flags(struct vm_area_struct *vma, 69 unsigned long address, pte_t *ptep, 70 pte_t entry, int dirty) 71 { 72 int changed = !pte_same(ptep_get(ptep), entry); 73 if (changed) { 74 set_pte_at(vma->vm_mm, address, ptep, entry); 75 flush_tlb_fix_spurious_fault(vma, address, ptep); 76 } 77 return changed; 78 } 79 #endif 80 81 #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH 82 int ptep_clear_flush_young(struct vm_area_struct *vma, 83 unsigned long address, pte_t *ptep) 84 { 85 int young; 86 young = ptep_test_and_clear_young(vma, address, ptep); 87 if (young) 88 flush_tlb_page(vma, address); 89 return young; 90 } 91 #endif 92 93 #ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH 94 pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address, 95 pte_t *ptep) 96 { 97 struct mm_struct *mm = (vma)->vm_mm; 98 pte_t pte; 99 pte = ptep_get_and_clear(mm, address, ptep); 100 if (pte_accessible(mm, pte)) 101 flush_tlb_page(vma, address); 102 return pte; 103 } 104 #endif 105 106 #ifdef CONFIG_TRANSPARENT_HUGEPAGE 107 108 #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS 109 int pmdp_set_access_flags(struct vm_area_struct *vma, 110 unsigned long address, pmd_t *pmdp, 111 pmd_t entry, int dirty) 112 { 113 int changed = !pmd_same(*pmdp, entry); 114 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 115 if (changed) { 116 set_pmd_at(vma->vm_mm, address, pmdp, entry); 117 flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 118 } 119 return changed; 120 } 121 #endif 122 123 #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH 124 int pmdp_clear_flush_young(struct vm_area_struct *vma, 125 unsigned long address, pmd_t *pmdp) 126 { 127 int young; 128 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 129 young = pmdp_test_and_clear_young(vma, address, pmdp); 130 if (young) 131 flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 132 return young; 133 } 134 #endif 135 136 #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH 137 pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address, 138 pmd_t *pmdp) 139 { 140 pmd_t pmd; 141 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 142 VM_BUG_ON(pmd_present(*pmdp) && !pmd_trans_huge(*pmdp)); 143 pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp); 144 flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 145 return pmd; 146 } 147 148 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 149 pud_t pudp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address, 150 pud_t *pudp) 151 { 152 pud_t pud; 153 154 VM_BUG_ON(address & ~HPAGE_PUD_MASK); 155 VM_BUG_ON(!pud_trans_huge(*pudp)); 156 pud = pudp_huge_get_and_clear(vma->vm_mm, address, pudp); 157 flush_pud_tlb_range(vma, address, address + HPAGE_PUD_SIZE); 158 return pud; 159 } 160 #endif 161 #endif 162 163 #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT 164 void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp, 165 pgtable_t pgtable) 166 { 167 assert_spin_locked(pmd_lockptr(mm, pmdp)); 168 169 /* FIFO */ 170 if (!pmd_huge_pte(mm, pmdp)) 171 INIT_LIST_HEAD(&pgtable->lru); 172 else 173 list_add(&pgtable->lru, &pmd_huge_pte(mm, pmdp)->lru); 174 pmd_huge_pte(mm, pmdp) = pgtable; 175 } 176 #endif 177 178 #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW 179 /* no "address" argument so destroys page coloring of some arch */ 180 pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp) 181 { 182 pgtable_t pgtable; 183 184 assert_spin_locked(pmd_lockptr(mm, pmdp)); 185 186 /* FIFO */ 187 pgtable = pmd_huge_pte(mm, pmdp); 188 pmd_huge_pte(mm, pmdp) = list_first_entry_or_null(&pgtable->lru, 189 struct page, lru); 190 if (pmd_huge_pte(mm, pmdp)) 191 list_del(&pgtable->lru); 192 return pgtable; 193 } 194 #endif 195 196 #ifndef __HAVE_ARCH_PMDP_INVALIDATE 197 pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, 198 pmd_t *pmdp) 199 { 200 VM_WARN_ON_ONCE(!pmd_present(*pmdp)); 201 pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp)); 202 flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 203 return old; 204 } 205 #endif 206 207 #ifndef __HAVE_ARCH_PMDP_INVALIDATE_AD 208 pmd_t pmdp_invalidate_ad(struct vm_area_struct *vma, unsigned long address, 209 pmd_t *pmdp) 210 { 211 VM_WARN_ON_ONCE(!pmd_present(*pmdp)); 212 return pmdp_invalidate(vma, address, pmdp); 213 } 214 #endif 215 216 #ifndef pmdp_collapse_flush 217 pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address, 218 pmd_t *pmdp) 219 { 220 /* 221 * pmd and hugepage pte format are same. So we could 222 * use the same function. 223 */ 224 pmd_t pmd; 225 226 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 227 VM_BUG_ON(pmd_trans_huge(*pmdp)); 228 pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp); 229 230 /* collapse entails shooting down ptes not pmd */ 231 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 232 return pmd; 233 } 234 #endif 235 236 /* arch define pte_free_defer in asm/pgalloc.h for its own implementation */ 237 #ifndef pte_free_defer 238 static void pte_free_now(struct rcu_head *head) 239 { 240 struct page *page; 241 242 page = container_of(head, struct page, rcu_head); 243 pte_free(NULL /* mm not passed and not used */, (pgtable_t)page); 244 } 245 246 void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable) 247 { 248 struct page *page; 249 250 page = pgtable; 251 call_rcu(&page->rcu_head, pte_free_now); 252 } 253 #endif /* pte_free_defer */ 254 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ 255 256 #if defined(CONFIG_GUP_GET_PXX_LOW_HIGH) && \ 257 (defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RCU)) 258 /* 259 * See the comment above ptep_get_lockless() in include/linux/pgtable.h: 260 * the barriers in pmdp_get_lockless() cannot guarantee that the value in 261 * pmd_high actually belongs with the value in pmd_low; but holding interrupts 262 * off blocks the TLB flush between present updates, which guarantees that a 263 * successful __pte_offset_map() points to a page from matched halves. 264 */ 265 static unsigned long pmdp_get_lockless_start(void) 266 { 267 unsigned long irqflags; 268 269 local_irq_save(irqflags); 270 return irqflags; 271 } 272 static void pmdp_get_lockless_end(unsigned long irqflags) 273 { 274 local_irq_restore(irqflags); 275 } 276 #else 277 static unsigned long pmdp_get_lockless_start(void) { return 0; } 278 static void pmdp_get_lockless_end(unsigned long irqflags) { } 279 #endif 280 281 pte_t *___pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) 282 { 283 unsigned long irqflags; 284 pmd_t pmdval; 285 286 rcu_read_lock(); 287 irqflags = pmdp_get_lockless_start(); 288 pmdval = pmdp_get_lockless(pmd); 289 pmdp_get_lockless_end(irqflags); 290 291 if (pmdvalp) 292 *pmdvalp = pmdval; 293 if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval))) 294 goto nomap; 295 if (unlikely(pmd_trans_huge(pmdval))) 296 goto nomap; 297 if (unlikely(pmd_bad(pmdval))) { 298 pmd_clear_bad(pmd); 299 goto nomap; 300 } 301 return __pte_map(&pmdval, addr); 302 nomap: 303 rcu_read_unlock(); 304 return NULL; 305 } 306 307 pte_t *pte_offset_map_ro_nolock(struct mm_struct *mm, pmd_t *pmd, 308 unsigned long addr, spinlock_t **ptlp) 309 { 310 pmd_t pmdval; 311 pte_t *pte; 312 313 pte = __pte_offset_map(pmd, addr, &pmdval); 314 if (likely(pte)) 315 *ptlp = pte_lockptr(mm, &pmdval); 316 return pte; 317 } 318 319 pte_t *pte_offset_map_rw_nolock(struct mm_struct *mm, pmd_t *pmd, 320 unsigned long addr, pmd_t *pmdvalp, 321 spinlock_t **ptlp) 322 { 323 pte_t *pte; 324 325 VM_WARN_ON_ONCE(!pmdvalp); 326 pte = __pte_offset_map(pmd, addr, pmdvalp); 327 if (likely(pte)) 328 *ptlp = pte_lockptr(mm, pmdvalp); 329 return pte; 330 } 331 332 /* 333 * pte_offset_map_lock(mm, pmd, addr, ptlp), and its internal implementation 334 * __pte_offset_map_lock() below, is usually called with the pmd pointer for 335 * addr, reached by walking down the mm's pgd, p4d, pud for addr: either while 336 * holding mmap_lock or vma lock for read or for write; or in truncate or rmap 337 * context, while holding file's i_mmap_lock or anon_vma lock for read (or for 338 * write). In a few cases, it may be used with pmd pointing to a pmd_t already 339 * copied to or constructed on the stack. 340 * 341 * When successful, it returns the pte pointer for addr, with its page table 342 * kmapped if necessary (when CONFIG_HIGHPTE), and locked against concurrent 343 * modification by software, with a pointer to that spinlock in ptlp (in some 344 * configs mm->page_table_lock, in SPLIT_PTLOCK configs a spinlock in table's 345 * struct page). pte_unmap_unlock(pte, ptl) to unlock and unmap afterwards. 346 * 347 * But it is unsuccessful, returning NULL with *ptlp unchanged, if there is no 348 * page table at *pmd: if, for example, the page table has just been removed, 349 * or replaced by the huge pmd of a THP. (When successful, *pmd is rechecked 350 * after acquiring the ptlock, and retried internally if it changed: so that a 351 * page table can be safely removed or replaced by THP while holding its lock.) 352 * 353 * pte_offset_map(pmd, addr), and its internal helper __pte_offset_map() above, 354 * just returns the pte pointer for addr, its page table kmapped if necessary; 355 * or NULL if there is no page table at *pmd. It does not attempt to lock the 356 * page table, so cannot normally be used when the page table is to be updated, 357 * or when entries read must be stable. But it does take rcu_read_lock(): so 358 * that even when page table is racily removed, it remains a valid though empty 359 * and disconnected table. Until pte_unmap(pte) unmaps and rcu_read_unlock()s 360 * afterwards. 361 * 362 * pte_offset_map_ro_nolock(mm, pmd, addr, ptlp), above, is like pte_offset_map(); 363 * but when successful, it also outputs a pointer to the spinlock in ptlp - as 364 * pte_offset_map_lock() does, but in this case without locking it. This helps 365 * the caller to avoid a later pte_lockptr(mm, *pmd), which might by that time 366 * act on a changed *pmd: pte_offset_map_ro_nolock() provides the correct spinlock 367 * pointer for the page table that it returns. Even after grabbing the spinlock, 368 * we might be looking either at a page table that is still mapped or one that 369 * was unmapped and is about to get freed. But for R/O access this is sufficient. 370 * So it is only applicable for read-only cases where any modification operations 371 * to the page table are not allowed even if the corresponding spinlock is held 372 * afterwards. 373 * 374 * pte_offset_map_rw_nolock(mm, pmd, addr, pmdvalp, ptlp), above, is like 375 * pte_offset_map_ro_nolock(); but when successful, it also outputs the pdmval. 376 * It is applicable for may-write cases where any modification operations to the 377 * page table may happen after the corresponding spinlock is held afterwards. 378 * But the users should make sure the page table is stable like checking pte_same() 379 * or checking pmd_same() by using the output pmdval before performing the write 380 * operations. 381 * 382 * Note: "RO" / "RW" expresses the intended semantics, not that the *kmap* will 383 * be read-only/read-write protected. 384 * 385 * Note that free_pgtables(), used after unmapping detached vmas, or when 386 * exiting the whole mm, does not take page table lock before freeing a page 387 * table, and may not use RCU at all: "outsiders" like khugepaged should avoid 388 * pte_offset_map() and co once the vma is detached from mm or mm_users is zero. 389 */ 390 pte_t *__pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd, 391 unsigned long addr, spinlock_t **ptlp) 392 { 393 spinlock_t *ptl; 394 pmd_t pmdval; 395 pte_t *pte; 396 again: 397 pte = __pte_offset_map(pmd, addr, &pmdval); 398 if (unlikely(!pte)) 399 return pte; 400 ptl = pte_lockptr(mm, &pmdval); 401 spin_lock(ptl); 402 if (likely(pmd_same(pmdval, pmdp_get_lockless(pmd)))) { 403 *ptlp = ptl; 404 return pte; 405 } 406 pte_unmap_unlock(pte, ptl); 407 goto again; 408 } 409