Root/mm/pagewalk.c

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(walk->mm, 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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