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_devmap(*pmdp)); 144 pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp); 145 flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 146 return pmd; 147 } 148 149 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 150 pud_t pudp_huge_clear_flush(struct vm_area_struct *vma, unsigned long address, 151 pud_t *pudp) 152 { 153 pud_t pud; 154 155 VM_BUG_ON(address & ~HPAGE_PUD_MASK); 156 VM_BUG_ON(!pud_trans_huge(*pudp) && !pud_devmap(*pudp)); 157 pud = pudp_huge_get_and_clear(vma->vm_mm, address, pudp); 158 flush_pud_tlb_range(vma, address, address + HPAGE_PUD_SIZE); 159 return pud; 160 } 161 #endif 162 #endif 163 164 #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT 165 void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp, 166 pgtable_t pgtable) 167 { 168 assert_spin_locked(pmd_lockptr(mm, pmdp)); 169 170 /* FIFO */ 171 if (!pmd_huge_pte(mm, pmdp)) 172 INIT_LIST_HEAD(&pgtable->lru); 173 else 174 list_add(&pgtable->lru, &pmd_huge_pte(mm, pmdp)->lru); 175 pmd_huge_pte(mm, pmdp) = pgtable; 176 } 177 #endif 178 179 #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW 180 /* no "address" argument so destroys page coloring of some arch */ 181 pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp) 182 { 183 pgtable_t pgtable; 184 185 assert_spin_locked(pmd_lockptr(mm, pmdp)); 186 187 /* FIFO */ 188 pgtable = pmd_huge_pte(mm, pmdp); 189 pmd_huge_pte(mm, pmdp) = list_first_entry_or_null(&pgtable->lru, 190 struct page, lru); 191 if (pmd_huge_pte(mm, pmdp)) 192 list_del(&pgtable->lru); 193 return pgtable; 194 } 195 #endif 196 197 #ifndef __HAVE_ARCH_PMDP_INVALIDATE 198 pmd_t pmdp_invalidate(struct vm_area_struct *vma, unsigned long address, 199 pmd_t *pmdp) 200 { 201 VM_WARN_ON_ONCE(!pmd_present(*pmdp)); 202 pmd_t old = pmdp_establish(vma, address, pmdp, pmd_mkinvalid(*pmdp)); 203 flush_pmd_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 204 return old; 205 } 206 #endif 207 208 #ifndef __HAVE_ARCH_PMDP_INVALIDATE_AD 209 pmd_t pmdp_invalidate_ad(struct vm_area_struct *vma, unsigned long address, 210 pmd_t *pmdp) 211 { 212 VM_WARN_ON_ONCE(!pmd_present(*pmdp)); 213 return pmdp_invalidate(vma, address, pmdp); 214 } 215 #endif 216 217 #ifndef pmdp_collapse_flush 218 pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address, 219 pmd_t *pmdp) 220 { 221 /* 222 * pmd and hugepage pte format are same. So we could 223 * use the same function. 224 */ 225 pmd_t pmd; 226 227 VM_BUG_ON(address & ~HPAGE_PMD_MASK); 228 VM_BUG_ON(pmd_trans_huge(*pmdp)); 229 pmd = pmdp_huge_get_and_clear(vma->vm_mm, address, pmdp); 230 231 /* collapse entails shooting down ptes not pmd */ 232 flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE); 233 return pmd; 234 } 235 #endif 236 237 /* arch define pte_free_defer in asm/pgalloc.h for its own implementation */ 238 #ifndef pte_free_defer 239 static void pte_free_now(struct rcu_head *head) 240 { 241 struct page *page; 242 243 page = container_of(head, struct page, rcu_head); 244 pte_free(NULL /* mm not passed and not used */, (pgtable_t)page); 245 } 246 247 void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable) 248 { 249 struct page *page; 250 251 page = pgtable; 252 call_rcu(&page->rcu_head, pte_free_now); 253 } 254 #endif /* pte_free_defer */ 255 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ 256 257 #if defined(CONFIG_GUP_GET_PXX_LOW_HIGH) && \ 258 (defined(CONFIG_SMP) || defined(CONFIG_PREEMPT_RCU)) 259 /* 260 * See the comment above ptep_get_lockless() in include/linux/pgtable.h: 261 * the barriers in pmdp_get_lockless() cannot guarantee that the value in 262 * pmd_high actually belongs with the value in pmd_low; but holding interrupts 263 * off blocks the TLB flush between present updates, which guarantees that a 264 * successful __pte_offset_map() points to a page from matched halves. 265 */ 266 static unsigned long pmdp_get_lockless_start(void) 267 { 268 unsigned long irqflags; 269 270 local_irq_save(irqflags); 271 return irqflags; 272 } 273 static void pmdp_get_lockless_end(unsigned long irqflags) 274 { 275 local_irq_restore(irqflags); 276 } 277 #else 278 static unsigned long pmdp_get_lockless_start(void) { return 0; } 279 static void pmdp_get_lockless_end(unsigned long irqflags) { } 280 #endif 281 282 pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp) 283 { 284 unsigned long irqflags; 285 pmd_t pmdval; 286 287 rcu_read_lock(); 288 irqflags = pmdp_get_lockless_start(); 289 pmdval = pmdp_get_lockless(pmd); 290 pmdp_get_lockless_end(irqflags); 291 292 if (pmdvalp) 293 *pmdvalp = pmdval; 294 if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval))) 295 goto nomap; 296 if (unlikely(pmd_trans_huge(pmdval) || pmd_devmap(pmdval))) 297 goto nomap; 298 if (unlikely(pmd_bad(pmdval))) { 299 pmd_clear_bad(pmd); 300 goto nomap; 301 } 302 return __pte_map(&pmdval, addr); 303 nomap: 304 rcu_read_unlock(); 305 return NULL; 306 } 307 308 pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd, 309 unsigned long addr, spinlock_t **ptlp) 310 { 311 pmd_t pmdval; 312 pte_t *pte; 313 314 pte = __pte_offset_map(pmd, addr, &pmdval); 315 if (likely(pte)) 316 *ptlp = pte_lockptr(mm, &pmdval); 317 return pte; 318 } 319 320 /* 321 * pte_offset_map_lock(mm, pmd, addr, ptlp), and its internal implementation 322 * __pte_offset_map_lock() below, is usually called with the pmd pointer for 323 * addr, reached by walking down the mm's pgd, p4d, pud for addr: either while 324 * holding mmap_lock or vma lock for read or for write; or in truncate or rmap 325 * context, while holding file's i_mmap_lock or anon_vma lock for read (or for 326 * write). In a few cases, it may be used with pmd pointing to a pmd_t already 327 * copied to or constructed on the stack. 328 * 329 * When successful, it returns the pte pointer for addr, with its page table 330 * kmapped if necessary (when CONFIG_HIGHPTE), and locked against concurrent 331 * modification by software, with a pointer to that spinlock in ptlp (in some 332 * configs mm->page_table_lock, in SPLIT_PTLOCK configs a spinlock in table's 333 * struct page). pte_unmap_unlock(pte, ptl) to unlock and unmap afterwards. 334 * 335 * But it is unsuccessful, returning NULL with *ptlp unchanged, if there is no 336 * page table at *pmd: if, for example, the page table has just been removed, 337 * or replaced by the huge pmd of a THP. (When successful, *pmd is rechecked 338 * after acquiring the ptlock, and retried internally if it changed: so that a 339 * page table can be safely removed or replaced by THP while holding its lock.) 340 * 341 * pte_offset_map(pmd, addr), and its internal helper __pte_offset_map() above, 342 * just returns the pte pointer for addr, its page table kmapped if necessary; 343 * or NULL if there is no page table at *pmd. It does not attempt to lock the 344 * page table, so cannot normally be used when the page table is to be updated, 345 * or when entries read must be stable. But it does take rcu_read_lock(): so 346 * that even when page table is racily removed, it remains a valid though empty 347 * and disconnected table. Until pte_unmap(pte) unmaps and rcu_read_unlock()s 348 * afterwards. 349 * 350 * pte_offset_map_nolock(mm, pmd, addr, ptlp), above, is like pte_offset_map(); 351 * but when successful, it also outputs a pointer to the spinlock in ptlp - as 352 * pte_offset_map_lock() does, but in this case without locking it. This helps 353 * the caller to avoid a later pte_lockptr(mm, *pmd), which might by that time 354 * act on a changed *pmd: pte_offset_map_nolock() provides the correct spinlock 355 * pointer for the page table that it returns. In principle, the caller should 356 * recheck *pmd once the lock is taken; in practice, no callsite needs that - 357 * either the mmap_lock for write, or pte_same() check on contents, is enough. 358 * 359 * Note that free_pgtables(), used after unmapping detached vmas, or when 360 * exiting the whole mm, does not take page table lock before freeing a page 361 * table, and may not use RCU at all: "outsiders" like khugepaged should avoid 362 * pte_offset_map() and co once the vma is detached from mm or mm_users is zero. 363 */ 364 pte_t *__pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd, 365 unsigned long addr, spinlock_t **ptlp) 366 { 367 spinlock_t *ptl; 368 pmd_t pmdval; 369 pte_t *pte; 370 again: 371 pte = __pte_offset_map(pmd, addr, &pmdval); 372 if (unlikely(!pte)) 373 return pte; 374 ptl = pte_lockptr(mm, &pmdval); 375 spin_lock(ptl); 376 if (likely(pmd_same(pmdval, pmdp_get_lockless(pmd)))) { 377 *ptlp = ptl; 378 return pte; 379 } 380 pte_unmap_unlock(pte, ptl); 381 goto again; 382 } 383