linux/mm/pagewalk.c
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   1#include <linux/mm.h>
   2#include <linux/highmem.h>
   3#include <linux/sched.h>
   4#include <linux/hugetlb.h>
   5
   6static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
   7                          struct mm_walk *walk)
   8{
   9        pte_t *pte;
  10        int err = 0;
  11
  12        pte = pte_offset_map(pmd, addr);
  13        for (;;) {
  14                err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
  15                if (err)
  16                       break;
  17                addr += PAGE_SIZE;
  18                if (addr == end)
  19                        break;
  20                pte++;
  21        }
  22
  23        pte_unmap(pte);
  24        return err;
  25}
  26
  27static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
  28                          struct mm_walk *walk)
  29{
  30        pmd_t *pmd;
  31        unsigned long next;
  32        int err = 0;
  33
  34        pmd = pmd_offset(pud, addr);
  35        do {
  36again:
  37                next = pmd_addr_end(addr, end);
  38                if (pmd_none(*pmd)) {
  39                        if (walk->pte_hole)
  40                                err = walk->pte_hole(addr, next, walk);
  41                        if (err)
  42                                break;
  43                        continue;
  44                }
  45                /*
  46                 * This implies that each ->pmd_entry() handler
  47                 * needs to know about pmd_trans_huge() pmds
  48                 */
  49                if (walk->pmd_entry)
  50                        err = walk->pmd_entry(pmd, addr, next, walk);
  51                if (err)
  52                        break;
  53
  54                /*
  55                 * Check this here so we only break down trans_huge
  56                 * pages when we _need_ to
  57                 */
  58                if (!walk->pte_entry)
  59                        continue;
  60
  61                split_huge_page_pmd_mm(walk->mm, addr, pmd);
  62                if (pmd_none_or_trans_huge_or_clear_bad(pmd))
  63                        goto again;
  64                err = walk_pte_range(pmd, addr, next, walk);
  65                if (err)
  66                        break;
  67        } while (pmd++, addr = next, addr != end);
  68
  69        return err;
  70}
  71
  72static int walk_pud_range(pgd_t *pgd, unsigned long addr, unsigned long end,
  73                          struct mm_walk *walk)
  74{
  75        pud_t *pud;
  76        unsigned long next;
  77        int err = 0;
  78
  79        pud = pud_offset(pgd, addr);
  80        do {
  81                next = pud_addr_end(addr, end);
  82                if (pud_none_or_clear_bad(pud)) {
  83                        if (walk->pte_hole)
  84                                err = walk->pte_hole(addr, next, walk);
  85                        if (err)
  86                                break;
  87                        continue;
  88                }
  89                if (walk->pud_entry)
  90                        err = walk->pud_entry(pud, addr, next, walk);
  91                if (!err && (walk->pmd_entry || walk->pte_entry))
  92                        err = walk_pmd_range(pud, addr, next, walk);
  93                if (err)
  94                        break;
  95        } while (pud++, addr = next, addr != end);
  96
  97        return err;
  98}
  99
 100#ifdef CONFIG_HUGETLB_PAGE
 101static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
 102                                       unsigned long end)
 103{
 104        unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
 105        return boundary < end ? boundary : end;
 106}
 107
 108static int walk_hugetlb_range(struct vm_area_struct *vma,
 109                              unsigned long addr, unsigned long end,
 110                              struct mm_walk *walk)
 111{
 112        struct hstate *h = hstate_vma(vma);
 113        unsigned long next;
 114        unsigned long hmask = huge_page_mask(h);
 115        pte_t *pte;
 116        int err = 0;
 117
 118        do {
 119                next = hugetlb_entry_end(h, addr, end);
 120                pte = huge_pte_offset(walk->mm, addr & hmask);
 121                if (pte && walk->hugetlb_entry)
 122                        err = walk->hugetlb_entry(pte, hmask, addr, next, walk);
 123                if (err)
 124                        return err;
 125        } while (addr = next, addr != end);
 126
 127        return 0;
 128}
 129
 130static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
 131{
 132        struct vm_area_struct *vma;
 133
 134        /* We don't need vma lookup at all. */
 135        if (!walk->hugetlb_entry)
 136                return NULL;
 137
 138        VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem));
 139        vma = find_vma(walk->mm, addr);
 140        if (vma && vma->vm_start <= addr && is_vm_hugetlb_page(vma))
 141                return vma;
 142
 143        return NULL;
 144}
 145
 146#else /* CONFIG_HUGETLB_PAGE */
 147static struct vm_area_struct* hugetlb_vma(unsigned long addr, struct mm_walk *walk)
 148{
 149        return NULL;
 150}
 151
 152static int walk_hugetlb_range(struct vm_area_struct *vma,
 153                              unsigned long addr, unsigned long end,
 154                              struct mm_walk *walk)
 155{
 156        return 0;
 157}
 158
 159#endif /* CONFIG_HUGETLB_PAGE */
 160
 161
 162
 163/**
 164 * walk_page_range - walk a memory map's page tables with a callback
 165 * @addr: starting address
 166 * @end: ending address
 167 * @walk: set of callbacks to invoke for each level of the tree
 168 *
 169 * Recursively walk the page table for the memory area in a VMA,
 170 * calling supplied callbacks. Callbacks are called in-order (first
 171 * PGD, first PUD, first PMD, first PTE, second PTE... second PMD,
 172 * etc.). If lower-level callbacks are omitted, walking depth is reduced.
 173 *
 174 * Each callback receives an entry pointer and the start and end of the
 175 * associated range, and a copy of the original mm_walk for access to
 176 * the ->private or ->mm fields.
 177 *
 178 * Usually no locks are taken, but splitting transparent huge page may
 179 * take page table lock. And the bottom level iterator will map PTE
 180 * directories from highmem if necessary.
 181 *
 182 * If any callback returns a non-zero value, the walk is aborted and
 183 * the return value is propagated back to the caller. Otherwise 0 is returned.
 184 *
 185 * walk->mm->mmap_sem must be held for at least read if walk->hugetlb_entry
 186 * is !NULL.
 187 */
 188int walk_page_range(unsigned long addr, unsigned long end,
 189                    struct mm_walk *walk)
 190{
 191        pgd_t *pgd;
 192        unsigned long next;
 193        int err = 0;
 194
 195        if (addr >= end)
 196                return err;
 197
 198        if (!walk->mm)
 199                return -EINVAL;
 200
 201        pgd = pgd_offset(walk->mm, addr);
 202        do {
 203                struct vm_area_struct *vma;
 204
 205                next = pgd_addr_end(addr, end);
 206
 207                /*
 208                 * handle hugetlb vma individually because pagetable walk for
 209                 * the hugetlb page is dependent on the architecture and
 210                 * we can't handled it in the same manner as non-huge pages.
 211                 */
 212                vma = hugetlb_vma(addr, walk);
 213                if (vma) {
 214                        if (vma->vm_end < next)
 215                                next = vma->vm_end;
 216                        /*
 217                         * Hugepage is very tightly coupled with vma, so
 218                         * walk through hugetlb entries within a given vma.
 219                         */
 220                        err = walk_hugetlb_range(vma, addr, next, walk);
 221                        if (err)
 222                                break;
 223                        pgd = pgd_offset(walk->mm, next);
 224                        continue;
 225                }
 226
 227                if (pgd_none_or_clear_bad(pgd)) {
 228                        if (walk->pte_hole)
 229                                err = walk->pte_hole(addr, next, walk);
 230                        if (err)
 231                                break;
 232                        pgd++;
 233                        continue;
 234                }
 235                if (walk->pgd_entry)
 236                        err = walk->pgd_entry(pgd, addr, next, walk);
 237                if (!err &&
 238                    (walk->pud_entry || walk->pmd_entry || walk->pte_entry))
 239                        err = walk_pud_range(pgd, addr, next, walk);
 240                if (err)
 241                        break;
 242                pgd++;
 243        } while (addr = next, addr != end);
 244
 245        return err;
 246}
 247
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