@@ -2637,7 +2637,6 @@ typedef int (*pte_fn_t)(pte_t *pte, unsigned long addr, void *data);
extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
unsigned long size, pte_fn_t fn, void *data);
-
#ifdef CONFIG_PAGE_POISONING
extern bool page_poisoning_enabled(void);
extern void kernel_poison_pages(struct page *page, int numpages, int enable);
@@ -2878,5 +2877,17 @@ static inline int pages_identical(struct page *page1, struct page *page2)
return !memcmp_pages(page1, page2);
}
+#ifdef CONFIG_MAPPING_DIRTY_HELPERS
+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);
+
+unsigned long wp_shared_mapping_range(struct address_space *mapping,
+ pgoff_t first_index, pgoff_t nr);
+#endif
+
#endif /* __KERNEL__ */
#endif /* _LINUX_MM_H */
@@ -736,4 +736,7 @@ config ARCH_HAS_PTE_SPECIAL
config ARCH_HAS_HUGEPD
bool
+config MAPPING_DIRTY_HELPERS
+ bool
+
endmenu
@@ -107,3 +107,4 @@ obj-$(CONFIG_PERCPU_STATS) += percpu-stats.o
obj-$(CONFIG_ZONE_DEVICE) += memremap.o
obj-$(CONFIG_HMM_MIRROR) += hmm.o
obj-$(CONFIG_MEMFD_CREATE) += memfd.o
+obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
new file mode 100644
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/pagewalk.h>
+#include <linux/hugetlb.h>
+#include <linux/bitops.h>
+#include <linux/mmu_notifier.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 virtual page 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 virtual page address
+ * @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. */
+static int wp_clean_pmd_entry(pmd_t *pmd, unsigned long addr, unsigned long end,
+ struct mm_walk *walk)
+{
+ /* Dirty-tracking should be handled on the pte level */
+ pmd_t pmdval = pmd_read_atomic(pmd);
+
+ 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. */
+static int wp_clean_pud_entry(pud_t *pud, unsigned long addr, unsigned long end,
+ struct mm_walk *walk)
+{
+ /* Dirty-tracking should be handled on the pte level */
+ pud_t pudval = READ_ONCE(*pud);
+
+ if (pud_trans_huge(pudval) || pud_devmap(pudval))
+ WARN_ON(pud_write(pudval) || pud_dirty(pudval));
+
+ 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.
+ *
+ * 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 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);