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1// SPDX-License-Identifier: GPL-2.02#include <linux/pagewalk.h>3#include <linux/hugetlb.h>4#include <linux/bitops.h>5#include <linux/mmu_notifier.h>6#include <linux/mm_inline.h>7#include <asm/cacheflush.h>8#include <asm/tlbflush.h>9 10/**11 * struct wp_walk - Private struct for pagetable walk callbacks12 * @range: Range for mmu notifiers13 * @tlbflush_start: Address of first modified pte14 * @tlbflush_end: Address of last modified pte + 115 * @total: Total number of modified ptes16 */17struct wp_walk {18 struct mmu_notifier_range range;19 unsigned long tlbflush_start;20 unsigned long tlbflush_end;21 unsigned long total;22};23 24/**25 * wp_pte - Write-protect a pte26 * @pte: Pointer to the pte27 * @addr: The start of protecting virtual address28 * @end: The end of protecting virtual address29 * @walk: pagetable walk callback argument30 *31 * The function write-protects a pte and records the range in32 * virtual address space of touched ptes for efficient range TLB flushes.33 */34static int wp_pte(pte_t *pte, unsigned long addr, unsigned long end,35 struct mm_walk *walk)36{37 struct wp_walk *wpwalk = walk->private;38 pte_t ptent = ptep_get(pte);39 40 if (pte_write(ptent)) {41 pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte);42 43 ptent = pte_wrprotect(old_pte);44 ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);45 wpwalk->total++;46 wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);47 wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,48 addr + PAGE_SIZE);49 }50 51 return 0;52}53 54/**55 * struct clean_walk - Private struct for the clean_record_pte function.56 * @base: struct wp_walk we derive from57 * @bitmap_pgoff: Address_space Page offset of the first bit in @bitmap58 * @bitmap: Bitmap with one bit for each page offset in the address_space range59 * covered.60 * @start: Address_space page offset of first modified pte relative61 * to @bitmap_pgoff62 * @end: Address_space page offset of last modified pte relative63 * to @bitmap_pgoff64 */65struct clean_walk {66 struct wp_walk base;67 pgoff_t bitmap_pgoff;68 unsigned long *bitmap;69 pgoff_t start;70 pgoff_t end;71};72 73#define to_clean_walk(_wpwalk) container_of(_wpwalk, struct clean_walk, base)74 75/**76 * clean_record_pte - Clean a pte and record its address space offset in a77 * bitmap78 * @pte: Pointer to the pte79 * @addr: The start of virtual address to be clean80 * @end: The end of virtual address to be clean81 * @walk: pagetable walk callback argument82 *83 * The function cleans a pte and records the range in84 * virtual address space of touched ptes for efficient TLB flushes.85 * It also records dirty ptes in a bitmap representing page offsets86 * in the address_space, as well as the first and last of the bits87 * touched.88 */89static int clean_record_pte(pte_t *pte, unsigned long addr,90 unsigned long end, struct mm_walk *walk)91{92 struct wp_walk *wpwalk = walk->private;93 struct clean_walk *cwalk = to_clean_walk(wpwalk);94 pte_t ptent = ptep_get(pte);95 96 if (pte_dirty(ptent)) {97 pgoff_t pgoff = ((addr - walk->vma->vm_start) >> PAGE_SHIFT) +98 walk->vma->vm_pgoff - cwalk->bitmap_pgoff;99 pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte);100 101 ptent = pte_mkclean(old_pte);102 ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent);103 104 wpwalk->total++;105 wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr);106 wpwalk->tlbflush_end = max(wpwalk->tlbflush_end,107 addr + PAGE_SIZE);108 109 __set_bit(pgoff, cwalk->bitmap);110 cwalk->start = min(cwalk->start, pgoff);111 cwalk->end = max(cwalk->end, pgoff + 1);112 }113 114 return 0;115}116 117/*118 * wp_clean_pmd_entry - The pagewalk pmd callback.119 *120 * Dirty-tracking should take place on the PTE level, so121 * WARN() if encountering a dirty huge pmd.122 * Furthermore, never split huge pmds, since that currently123 * causes dirty info loss. The pagefault handler should do124 * that if needed.125 */126static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,127 struct mm_walk *walk)128{129 pmd_t pmdval = pmdp_get_lockless(pmd);130 131 /* Do not split a huge pmd, present or migrated */132 if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval)) {133 WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval));134 walk->action = ACTION_CONTINUE;135 }136 return 0;137}138 139/*140 * wp_clean_pud_entry - The pagewalk pud callback.141 *142 * Dirty-tracking should take place on the PTE level, so143 * WARN() if encountering a dirty huge puds.144 * Furthermore, never split huge puds, since that currently145 * causes dirty info loss. The pagefault handler should do146 * that if needed.147 */148static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,149 struct mm_walk *walk)150{151#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD152 pud_t pudval = READ_ONCE(*pud);153 154 /* Do not split a huge pud */155 if (pud_trans_huge(pudval) || pud_devmap(pudval)) {156 WARN_ON(pud_write(pudval) || pud_dirty(pudval));157 walk->action = ACTION_CONTINUE;158 }159#endif160 return 0;161}162 163/*164 * wp_clean_pre_vma - The pagewalk pre_vma callback.165 *166 * The pre_vma callback performs the cache flush, stages the tlb flush167 * and calls the necessary mmu notifiers.168 */169static int wp_clean_pre_vma(unsigned long start, unsigned long end,170 struct mm_walk *walk)171{172 struct wp_walk *wpwalk = walk->private;173 174 wpwalk->tlbflush_start = end;175 wpwalk->tlbflush_end = start;176 177 mmu_notifier_range_init(&wpwalk->range, MMU_NOTIFY_PROTECTION_PAGE, 0,178 walk->mm, start, end);179 mmu_notifier_invalidate_range_start(&wpwalk->range);180 flush_cache_range(walk->vma, start, end);181 182 /*183 * We're not using tlb_gather_mmu() since typically184 * only a small subrange of PTEs are affected, whereas185 * tlb_gather_mmu() records the full range.186 */187 inc_tlb_flush_pending(walk->mm);188 189 return 0;190}191 192/*193 * wp_clean_post_vma - The pagewalk post_vma callback.194 *195 * The post_vma callback performs the tlb flush and calls necessary mmu196 * notifiers.197 */198static void wp_clean_post_vma(struct mm_walk *walk)199{200 struct wp_walk *wpwalk = walk->private;201 202 if (mm_tlb_flush_nested(walk->mm))203 flush_tlb_range(walk->vma, wpwalk->range.start,204 wpwalk->range.end);205 else if (wpwalk->tlbflush_end > wpwalk->tlbflush_start)206 flush_tlb_range(walk->vma, wpwalk->tlbflush_start,207 wpwalk->tlbflush_end);208 209 mmu_notifier_invalidate_range_end(&wpwalk->range);210 dec_tlb_flush_pending(walk->mm);211}212 213/*214 * wp_clean_test_walk - The pagewalk test_walk callback.215 *216 * Won't perform dirty-tracking on COW, read-only or HUGETLB vmas.217 */218static int wp_clean_test_walk(unsigned long start, unsigned long end,219 struct mm_walk *walk)220{221 unsigned long vm_flags = READ_ONCE(walk->vma->vm_flags);222 223 /* Skip non-applicable VMAs */224 if ((vm_flags & (VM_SHARED | VM_MAYWRITE | VM_HUGETLB)) !=225 (VM_SHARED | VM_MAYWRITE))226 return 1;227 228 return 0;229}230 231static const struct mm_walk_ops clean_walk_ops = {232 .pte_entry = clean_record_pte,233 .pmd_entry = wp_clean_pmd_entry,234 .pud_entry = wp_clean_pud_entry,235 .test_walk = wp_clean_test_walk,236 .pre_vma = wp_clean_pre_vma,237 .post_vma = wp_clean_post_vma238};239 240static const struct mm_walk_ops wp_walk_ops = {241 .pte_entry = wp_pte,242 .pmd_entry = wp_clean_pmd_entry,243 .pud_entry = wp_clean_pud_entry,244 .test_walk = wp_clean_test_walk,245 .pre_vma = wp_clean_pre_vma,246 .post_vma = wp_clean_post_vma247};248 249/**250 * wp_shared_mapping_range - Write-protect all ptes in an address space range251 * @mapping: The address_space we want to write protect252 * @first_index: The first page offset in the range253 * @nr: Number of incremental page offsets to cover254 *255 * Note: This function currently skips transhuge page-table entries, since256 * it's intended for dirty-tracking on the PTE level. It will warn on257 * encountering transhuge write-enabled entries, though, and can easily be258 * extended to handle them as well.259 *260 * Return: The number of ptes actually write-protected. Note that261 * already write-protected ptes are not counted.262 */263unsigned long wp_shared_mapping_range(struct address_space *mapping,264 pgoff_t first_index, pgoff_t nr)265{266 struct wp_walk wpwalk = { .total = 0 };267 268 i_mmap_lock_read(mapping);269 WARN_ON(walk_page_mapping(mapping, first_index, nr, &wp_walk_ops,270 &wpwalk));271 i_mmap_unlock_read(mapping);272 273 return wpwalk.total;274}275EXPORT_SYMBOL_GPL(wp_shared_mapping_range);276 277/**278 * clean_record_shared_mapping_range - Clean and record all ptes in an279 * address space range280 * @mapping: The address_space we want to clean281 * @first_index: The first page offset in the range282 * @nr: Number of incremental page offsets to cover283 * @bitmap_pgoff: The page offset of the first bit in @bitmap284 * @bitmap: Pointer to a bitmap of at least @nr bits. The bitmap needs to285 * cover the whole range @first_index..@first_index + @nr.286 * @start: Pointer to number of the first set bit in @bitmap.287 * is modified as new bits are set by the function.288 * @end: Pointer to the number of the last set bit in @bitmap.289 * none set. The value is modified as new bits are set by the function.290 *291 * When this function returns there is no guarantee that a CPU has292 * not already dirtied new ptes. However it will not clean any ptes not293 * reported in the bitmap. The guarantees are as follows:294 *295 * * All ptes dirty when the function starts executing will end up recorded296 * in the bitmap.297 * * All ptes dirtied after that will either remain dirty, be recorded in the298 * bitmap or both.299 *300 * If a caller needs to make sure all dirty ptes are picked up and none301 * additional are added, it first needs to write-protect the address-space302 * range and make sure new writers are blocked in page_mkwrite() or303 * pfn_mkwrite(). And then after a TLB flush following the write-protection304 * pick up all dirty bits.305 *306 * This function currently skips transhuge page-table entries, since307 * it's intended for dirty-tracking on the PTE level. It will warn on308 * encountering transhuge dirty entries, though, and can easily be extended309 * to handle them as well.310 *311 * Return: The number of dirty ptes actually cleaned.312 */313unsigned long clean_record_shared_mapping_range(struct address_space *mapping,314 pgoff_t first_index, pgoff_t nr,315 pgoff_t bitmap_pgoff,316 unsigned long *bitmap,317 pgoff_t *start,318 pgoff_t *end)319{320 bool none_set = (*start >= *end);321 struct clean_walk cwalk = {322 .base = { .total = 0 },323 .bitmap_pgoff = bitmap_pgoff,324 .bitmap = bitmap,325 .start = none_set ? nr : *start,326 .end = none_set ? 0 : *end,327 };328 329 i_mmap_lock_read(mapping);330 WARN_ON(walk_page_mapping(mapping, first_index, nr, &clean_walk_ops,331 &cwalk.base));332 i_mmap_unlock_read(mapping);333 334 *start = cwalk.start;335 *end = cwalk.end;336 337 return cwalk.base.total;338}339EXPORT_SYMBOL_GPL(clean_record_shared_mapping_range);340