| // SPDX-License-Identifier: GPL-2.0 |
| #include <linux/pagewalk.h> |
| #include <linux/hugetlb.h> |
| #include <linux/bitops.h> |
| #include <linux/mmu_notifier.h> |
| #include <linux/mm_inline.h> |
| #include <asm/cacheflush.h> |
| #include <asm/tlbflush.h> |
| |
| /** |
| * struct wp_walk - Private struct for pagetable walk callbacks |
| * @range: Range for mmu notifiers |
| * @tlbflush_start: Address of first modified pte |
| * @tlbflush_end: Address of last modified pte + 1 |
| * @total: Total number of modified ptes |
| */ |
| struct wp_walk { |
| struct mmu_notifier_range range; |
| unsigned long tlbflush_start; |
| unsigned long tlbflush_end; |
| unsigned long total; |
| }; |
| |
| /** |
| * wp_pte - Write-protect a pte |
| * @pte: Pointer to the pte |
| * @addr: The start of protecting virtual address |
| * @end: The end of protecting virtual address |
| * @walk: pagetable walk callback argument |
| * |
| * The function write-protects a pte and records the range in |
| * virtual address space of touched ptes for efficient range TLB flushes. |
| */ |
| static int wp_pte(pte_t *pte, unsigned long addr, unsigned long end, |
| struct mm_walk *walk) |
| { |
| struct wp_walk *wpwalk = walk->private; |
| pte_t ptent = *pte; |
| |
| if (pte_write(ptent)) { |
| pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte); |
| |
| ptent = pte_wrprotect(old_pte); |
| ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent); |
| wpwalk->total++; |
| wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr); |
| wpwalk->tlbflush_end = max(wpwalk->tlbflush_end, |
| addr + PAGE_SIZE); |
| } |
| |
| return 0; |
| } |
| |
| /** |
| * struct clean_walk - Private struct for the clean_record_pte function. |
| * @base: struct wp_walk we derive from |
| * @bitmap_pgoff: Address_space Page offset of the first bit in @bitmap |
| * @bitmap: Bitmap with one bit for each page offset in the address_space range |
| * covered. |
| * @start: Address_space page offset of first modified pte relative |
| * to @bitmap_pgoff |
| * @end: Address_space page offset of last modified pte relative |
| * to @bitmap_pgoff |
| */ |
| struct clean_walk { |
| struct wp_walk base; |
| pgoff_t bitmap_pgoff; |
| unsigned long *bitmap; |
| pgoff_t start; |
| pgoff_t end; |
| }; |
| |
| #define to_clean_walk(_wpwalk) container_of(_wpwalk, struct clean_walk, base) |
| |
| /** |
| * clean_record_pte - Clean a pte and record its address space offset in a |
| * bitmap |
| * @pte: Pointer to the pte |
| * @addr: The start of virtual address to be clean |
| * @end: The end of virtual address to be clean |
| * @walk: pagetable walk callback argument |
| * |
| * The function cleans a pte and records the range in |
| * virtual address space of touched ptes for efficient TLB flushes. |
| * It also records dirty ptes in a bitmap representing page offsets |
| * in the address_space, as well as the first and last of the bits |
| * touched. |
| */ |
| static int clean_record_pte(pte_t *pte, unsigned long addr, |
| unsigned long end, struct mm_walk *walk) |
| { |
| struct wp_walk *wpwalk = walk->private; |
| struct clean_walk *cwalk = to_clean_walk(wpwalk); |
| pte_t ptent = *pte; |
| |
| if (pte_dirty(ptent)) { |
| pgoff_t pgoff = ((addr - walk->vma->vm_start) >> PAGE_SHIFT) + |
| walk->vma->vm_pgoff - cwalk->bitmap_pgoff; |
| pte_t old_pte = ptep_modify_prot_start(walk->vma, addr, pte); |
| |
| ptent = pte_mkclean(old_pte); |
| ptep_modify_prot_commit(walk->vma, addr, pte, old_pte, ptent); |
| |
| wpwalk->total++; |
| wpwalk->tlbflush_start = min(wpwalk->tlbflush_start, addr); |
| wpwalk->tlbflush_end = max(wpwalk->tlbflush_end, |
| addr + PAGE_SIZE); |
| |
| __set_bit(pgoff, cwalk->bitmap); |
| cwalk->start = min(cwalk->start, pgoff); |
| cwalk->end = max(cwalk->end, pgoff + 1); |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * wp_clean_pmd_entry - The pagewalk pmd callback. |
| * |
| * Dirty-tracking should take place on the PTE level, so |
| * WARN() if encountering a dirty huge pmd. |
| * Furthermore, never split huge pmds, since that currently |
| * causes dirty info loss. The pagefault handler should do |
| * that if needed. |
| */ |
| static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end, |
| struct mm_walk *walk) |
| { |
| pmd_t pmdval = pmd_read_atomic(pmd); |
| |
| if (!pmd_trans_unstable(&pmdval)) |
| return 0; |
| |
| if (pmd_none(pmdval)) { |
| walk->action = ACTION_AGAIN; |
| return 0; |
| } |
| |
| /* Huge pmd, present or migrated */ |
| walk->action = ACTION_CONTINUE; |
| if (pmd_trans_huge(pmdval) || pmd_devmap(pmdval)) |
| WARN_ON(pmd_write(pmdval) || pmd_dirty(pmdval)); |
| |
| return 0; |
| } |
| |
| /* |
| * wp_clean_pud_entry - The pagewalk pud callback. |
| * |
| * Dirty-tracking should take place on the PTE level, so |
| * WARN() if encountering a dirty huge puds. |
| * Furthermore, never split huge puds, since that currently |
| * causes dirty info loss. The pagefault handler should do |
| * that if needed. |
| */ |
| static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end, |
| struct mm_walk *walk) |
| { |
| pud_t pudval = READ_ONCE(*pud); |
| |
| if (!pud_trans_unstable(&pudval)) |
| return 0; |
| |
| if (pud_none(pudval)) { |
| walk->action = ACTION_AGAIN; |
| return 0; |
| } |
| |
| #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD |
| /* Huge pud */ |
| walk->action = ACTION_CONTINUE; |
| if (pud_trans_huge(pudval) || pud_devmap(pudval)) |
| WARN_ON(pud_write(pudval) || pud_dirty(pudval)); |
| #endif |
| |
| return 0; |
| } |
| |
| /* |
| * wp_clean_pre_vma - The pagewalk pre_vma callback. |
| * |
| * The pre_vma callback performs the cache flush, stages the tlb flush |
| * and calls the necessary mmu notifiers. |
| */ |
| static int wp_clean_pre_vma(unsigned long start, unsigned long end, |
| struct mm_walk *walk) |
| { |
| struct wp_walk *wpwalk = walk->private; |
| |
| wpwalk->tlbflush_start = end; |
| wpwalk->tlbflush_end = start; |
| |
| mmu_notifier_range_init(&wpwalk->range, MMU_NOTIFY_PROTECTION_PAGE, 0, |
| walk->vma, walk->mm, start, end); |
| mmu_notifier_invalidate_range_start(&wpwalk->range); |
| flush_cache_range(walk->vma, start, end); |
| |
| /* |
| * We're not using tlb_gather_mmu() since typically |
| * only a small subrange of PTEs are affected, whereas |
| * tlb_gather_mmu() records the full range. |
| */ |
| inc_tlb_flush_pending(walk->mm); |
| |
| return 0; |
| } |
| |
| /* |
| * wp_clean_post_vma - The pagewalk post_vma callback. |
| * |
| * The post_vma callback performs the tlb flush and calls necessary mmu |
| * notifiers. |
| */ |
| static void wp_clean_post_vma(struct mm_walk *walk) |
| { |
| struct wp_walk *wpwalk = walk->private; |
| |
| if (mm_tlb_flush_nested(walk->mm)) |
| flush_tlb_range(walk->vma, wpwalk->range.start, |
| wpwalk->range.end); |
| else if (wpwalk->tlbflush_end > wpwalk->tlbflush_start) |
| flush_tlb_range(walk->vma, wpwalk->tlbflush_start, |
| wpwalk->tlbflush_end); |
| |
| mmu_notifier_invalidate_range_end(&wpwalk->range); |
| dec_tlb_flush_pending(walk->mm); |
| } |
| |
| /* |
| * wp_clean_test_walk - The pagewalk test_walk callback. |
| * |
| * Won't perform dirty-tracking on COW, read-only or HUGETLB vmas. |
| */ |
| static int wp_clean_test_walk(unsigned long start, unsigned long end, |
| struct mm_walk *walk) |
| { |
| unsigned long vm_flags = READ_ONCE(walk->vma->vm_flags); |
| |
| /* Skip non-applicable VMAs */ |
| if ((vm_flags & (VM_SHARED | VM_MAYWRITE | VM_HUGETLB)) != |
| (VM_SHARED | VM_MAYWRITE)) |
| return 1; |
| |
| return 0; |
| } |
| |
| static const struct mm_walk_ops clean_walk_ops = { |
| .pte_entry = clean_record_pte, |
| .pmd_entry = wp_clean_pmd_entry, |
| .pud_entry = wp_clean_pud_entry, |
| .test_walk = wp_clean_test_walk, |
| .pre_vma = wp_clean_pre_vma, |
| .post_vma = wp_clean_post_vma |
| }; |
| |
| static const struct mm_walk_ops wp_walk_ops = { |
| .pte_entry = wp_pte, |
| .pmd_entry = wp_clean_pmd_entry, |
| .pud_entry = wp_clean_pud_entry, |
| .test_walk = wp_clean_test_walk, |
| .pre_vma = wp_clean_pre_vma, |
| .post_vma = wp_clean_post_vma |
| }; |
| |
| /** |
| * wp_shared_mapping_range - Write-protect all ptes in an address space range |
| * @mapping: The address_space we want to write protect |
| * @first_index: The first page offset in the range |
| * @nr: Number of incremental page offsets to cover |
| * |
| * Note: This function currently skips transhuge page-table entries, since |
| * it's intended for dirty-tracking on the PTE level. It will warn on |
| * encountering transhuge write-enabled entries, though, and can easily be |
| * extended to handle them as well. |
| * |
| * Return: The number of ptes actually write-protected. Note that |
| * already write-protected ptes are not counted. |
| */ |
| unsigned long wp_shared_mapping_range(struct address_space *mapping, |
| pgoff_t first_index, pgoff_t nr) |
| { |
| struct wp_walk wpwalk = { .total = 0 }; |
| |
| i_mmap_lock_read(mapping); |
| WARN_ON(walk_page_mapping(mapping, first_index, nr, &wp_walk_ops, |
| &wpwalk)); |
| i_mmap_unlock_read(mapping); |
| |
| return wpwalk.total; |
| } |
| EXPORT_SYMBOL_GPL(wp_shared_mapping_range); |
| |
| /** |
| * clean_record_shared_mapping_range - Clean and record all ptes in an |
| * address space range |
| * @mapping: The address_space we want to clean |
| * @first_index: The first page offset in the range |
| * @nr: Number of incremental page offsets to cover |
| * @bitmap_pgoff: The page offset of the first bit in @bitmap |
| * @bitmap: Pointer to a bitmap of at least @nr bits. The bitmap needs to |
| * cover the whole range @first_index..@first_index + @nr. |
| * @start: Pointer to number of the first set bit in @bitmap. |
| * is modified as new bits are set by the function. |
| * @end: Pointer to the number of the last set bit in @bitmap. |
| * none set. The value is modified as new bits are set by the function. |
| * |
| * Note: When this function returns there is no guarantee that a CPU has |
| * not already dirtied new ptes. However it will not clean any ptes not |
| * reported in the bitmap. The guarantees are as follows: |
| * a) All ptes dirty when the function starts executing will end up recorded |
| * in the bitmap. |
| * b) All ptes dirtied after that will either remain dirty, be recorded in the |
| * bitmap or both. |
| * |
| * If a caller needs to make sure all dirty ptes are picked up and none |
| * additional are added, it first needs to write-protect the address-space |
| * range and make sure new writers are blocked in page_mkwrite() or |
| * pfn_mkwrite(). And then after a TLB flush following the write-protection |
| * pick up all dirty bits. |
| * |
| * This function currently skips transhuge page-table entries, since |
| * it's intended for dirty-tracking on the PTE level. It will warn on |
| * encountering transhuge dirty entries, though, and can easily be extended |
| * to handle them as well. |
| * |
| * Return: The number of dirty ptes actually cleaned. |
| */ |
| unsigned long clean_record_shared_mapping_range(struct address_space *mapping, |
| pgoff_t first_index, pgoff_t nr, |
| pgoff_t bitmap_pgoff, |
| unsigned long *bitmap, |
| pgoff_t *start, |
| pgoff_t *end) |
| { |
| bool none_set = (*start >= *end); |
| struct clean_walk cwalk = { |
| .base = { .total = 0 }, |
| .bitmap_pgoff = bitmap_pgoff, |
| .bitmap = bitmap, |
| .start = none_set ? nr : *start, |
| .end = none_set ? 0 : *end, |
| }; |
| |
| i_mmap_lock_read(mapping); |
| WARN_ON(walk_page_mapping(mapping, first_index, nr, &clean_walk_ops, |
| &cwalk.base)); |
| i_mmap_unlock_read(mapping); |
| |
| *start = cwalk.start; |
| *end = cwalk.end; |
| |
| return cwalk.base.total; |
| } |
| EXPORT_SYMBOL_GPL(clean_record_shared_mapping_range); |