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