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e07cda5f23
Let's add walk_page_range_vma(), which is similar to walk_page_vma(), however, is only interested in a subset of the VMA range. To be used in KSM code to stop using follow_page() next. Link: https://lkml.kernel.org/r/20221021101141.84170-8-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: John Hubbard <jhubbard@nvidia.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Peter Xu <peterx@redhat.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Vlastimil Babka <vbabka@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
633 lines
16 KiB
C
633 lines
16 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/pagewalk.h>
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#include <linux/highmem.h>
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#include <linux/sched.h>
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#include <linux/hugetlb.h>
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/*
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* We want to know the real level where a entry is located ignoring any
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* folding of levels which may be happening. For example if p4d is folded then
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* a missing entry found at level 1 (p4d) is actually at level 0 (pgd).
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*/
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static int real_depth(int depth)
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{
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if (depth == 3 && PTRS_PER_PMD == 1)
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depth = 2;
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if (depth == 2 && PTRS_PER_PUD == 1)
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depth = 1;
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if (depth == 1 && PTRS_PER_P4D == 1)
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depth = 0;
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return depth;
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}
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static int walk_pte_range_inner(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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const struct mm_walk_ops *ops = walk->ops;
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int err = 0;
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for (;;) {
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err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
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if (err)
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break;
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if (addr >= end - PAGE_SIZE)
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break;
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addr += PAGE_SIZE;
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pte++;
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}
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return err;
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}
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static int walk_pte_range(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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pte_t *pte;
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int err = 0;
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spinlock_t *ptl;
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if (walk->no_vma) {
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pte = pte_offset_map(pmd, addr);
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err = walk_pte_range_inner(pte, addr, end, walk);
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pte_unmap(pte);
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} else {
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pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
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err = walk_pte_range_inner(pte, addr, end, walk);
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pte_unmap_unlock(pte, ptl);
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}
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return err;
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}
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#ifdef CONFIG_ARCH_HAS_HUGEPD
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static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
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unsigned long end, struct mm_walk *walk, int pdshift)
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{
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int err = 0;
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const struct mm_walk_ops *ops = walk->ops;
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int shift = hugepd_shift(*phpd);
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int page_size = 1 << shift;
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if (!ops->pte_entry)
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return 0;
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if (addr & (page_size - 1))
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return 0;
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for (;;) {
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pte_t *pte;
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spin_lock(&walk->mm->page_table_lock);
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pte = hugepte_offset(*phpd, addr, pdshift);
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err = ops->pte_entry(pte, addr, addr + page_size, walk);
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spin_unlock(&walk->mm->page_table_lock);
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if (err)
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break;
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if (addr >= end - page_size)
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break;
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addr += page_size;
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}
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return err;
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}
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#else
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static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
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unsigned long end, struct mm_walk *walk, int pdshift)
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{
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return 0;
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}
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#endif
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static int walk_pmd_range(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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pmd_t *pmd;
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unsigned long next;
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const struct mm_walk_ops *ops = walk->ops;
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int err = 0;
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int depth = real_depth(3);
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pmd = pmd_offset(pud, addr);
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do {
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again:
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next = pmd_addr_end(addr, end);
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if (pmd_none(*pmd)) {
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if (ops->pte_hole)
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err = ops->pte_hole(addr, next, depth, walk);
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if (err)
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break;
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continue;
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}
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walk->action = ACTION_SUBTREE;
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/*
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* This implies that each ->pmd_entry() handler
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* needs to know about pmd_trans_huge() pmds
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*/
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if (ops->pmd_entry)
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err = ops->pmd_entry(pmd, addr, next, walk);
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if (err)
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break;
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if (walk->action == ACTION_AGAIN)
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goto again;
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/*
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* Check this here so we only break down trans_huge
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* pages when we _need_ to
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*/
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if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) ||
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walk->action == ACTION_CONTINUE ||
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!(ops->pte_entry))
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continue;
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if (walk->vma) {
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split_huge_pmd(walk->vma, pmd, addr);
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if (pmd_trans_unstable(pmd))
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goto again;
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}
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if (is_hugepd(__hugepd(pmd_val(*pmd))))
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err = walk_hugepd_range((hugepd_t *)pmd, addr, next, walk, PMD_SHIFT);
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else
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err = walk_pte_range(pmd, addr, next, walk);
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if (err)
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break;
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} while (pmd++, addr = next, addr != end);
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return err;
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}
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static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
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struct mm_walk *walk)
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{
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pud_t *pud;
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unsigned long next;
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const struct mm_walk_ops *ops = walk->ops;
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int err = 0;
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int depth = real_depth(2);
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pud = pud_offset(p4d, addr);
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do {
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again:
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next = pud_addr_end(addr, end);
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if (pud_none(*pud)) {
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if (ops->pte_hole)
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err = ops->pte_hole(addr, next, depth, walk);
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if (err)
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break;
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continue;
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}
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walk->action = ACTION_SUBTREE;
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if (ops->pud_entry)
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err = ops->pud_entry(pud, addr, next, walk);
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if (err)
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break;
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if (walk->action == ACTION_AGAIN)
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goto again;
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if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) ||
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walk->action == ACTION_CONTINUE ||
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!(ops->pmd_entry || ops->pte_entry))
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continue;
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if (walk->vma)
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split_huge_pud(walk->vma, pud, addr);
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if (pud_none(*pud))
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goto again;
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if (is_hugepd(__hugepd(pud_val(*pud))))
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err = walk_hugepd_range((hugepd_t *)pud, addr, next, walk, PUD_SHIFT);
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else
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err = walk_pmd_range(pud, addr, next, walk);
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if (err)
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break;
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} while (pud++, addr = next, addr != end);
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return err;
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}
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static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
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struct mm_walk *walk)
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{
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p4d_t *p4d;
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unsigned long next;
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const struct mm_walk_ops *ops = walk->ops;
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int err = 0;
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int depth = real_depth(1);
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p4d = p4d_offset(pgd, addr);
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do {
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next = p4d_addr_end(addr, end);
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if (p4d_none_or_clear_bad(p4d)) {
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if (ops->pte_hole)
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err = ops->pte_hole(addr, next, depth, walk);
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if (err)
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break;
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continue;
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}
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if (ops->p4d_entry) {
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err = ops->p4d_entry(p4d, addr, next, walk);
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if (err)
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break;
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}
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if (is_hugepd(__hugepd(p4d_val(*p4d))))
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err = walk_hugepd_range((hugepd_t *)p4d, addr, next, walk, P4D_SHIFT);
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else if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
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err = walk_pud_range(p4d, addr, next, walk);
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if (err)
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break;
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} while (p4d++, addr = next, addr != end);
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return err;
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}
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static int walk_pgd_range(unsigned long addr, unsigned long end,
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struct mm_walk *walk)
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{
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pgd_t *pgd;
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unsigned long next;
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const struct mm_walk_ops *ops = walk->ops;
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int err = 0;
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if (walk->pgd)
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pgd = walk->pgd + pgd_index(addr);
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else
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pgd = pgd_offset(walk->mm, addr);
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do {
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next = pgd_addr_end(addr, end);
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if (pgd_none_or_clear_bad(pgd)) {
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if (ops->pte_hole)
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err = ops->pte_hole(addr, next, 0, walk);
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if (err)
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break;
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continue;
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}
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if (ops->pgd_entry) {
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err = ops->pgd_entry(pgd, addr, next, walk);
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if (err)
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break;
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}
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if (is_hugepd(__hugepd(pgd_val(*pgd))))
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err = walk_hugepd_range((hugepd_t *)pgd, addr, next, walk, PGDIR_SHIFT);
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else if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry)
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err = walk_p4d_range(pgd, addr, next, walk);
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if (err)
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break;
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} while (pgd++, addr = next, addr != end);
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return err;
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}
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#ifdef CONFIG_HUGETLB_PAGE
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static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
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unsigned long end)
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{
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unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
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return boundary < end ? boundary : end;
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}
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static int walk_hugetlb_range(unsigned long addr, unsigned long end,
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struct mm_walk *walk)
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{
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struct vm_area_struct *vma = walk->vma;
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struct hstate *h = hstate_vma(vma);
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unsigned long next;
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unsigned long hmask = huge_page_mask(h);
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unsigned long sz = huge_page_size(h);
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pte_t *pte;
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const struct mm_walk_ops *ops = walk->ops;
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int err = 0;
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do {
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next = hugetlb_entry_end(h, addr, end);
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pte = huge_pte_offset(walk->mm, addr & hmask, sz);
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if (pte)
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err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
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else if (ops->pte_hole)
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err = ops->pte_hole(addr, next, -1, walk);
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if (err)
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break;
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} while (addr = next, addr != end);
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return err;
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}
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#else /* CONFIG_HUGETLB_PAGE */
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static int walk_hugetlb_range(unsigned long addr, unsigned long end,
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struct mm_walk *walk)
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{
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return 0;
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}
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#endif /* CONFIG_HUGETLB_PAGE */
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/*
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* Decide whether we really walk over the current vma on [@start, @end)
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* or skip it via the returned value. Return 0 if we do walk over the
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* current vma, and return 1 if we skip the vma. Negative values means
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* error, where we abort the current walk.
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*/
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static int walk_page_test(unsigned long start, unsigned long end,
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struct mm_walk *walk)
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{
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struct vm_area_struct *vma = walk->vma;
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const struct mm_walk_ops *ops = walk->ops;
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if (ops->test_walk)
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return ops->test_walk(start, end, walk);
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/*
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* vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
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* range, so we don't walk over it as we do for normal vmas. However,
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* Some callers are interested in handling hole range and they don't
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* want to just ignore any single address range. Such users certainly
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* define their ->pte_hole() callbacks, so let's delegate them to handle
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* vma(VM_PFNMAP).
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*/
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if (vma->vm_flags & VM_PFNMAP) {
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int err = 1;
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if (ops->pte_hole)
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err = ops->pte_hole(start, end, -1, walk);
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return err ? err : 1;
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}
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return 0;
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}
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static int __walk_page_range(unsigned long start, unsigned long end,
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struct mm_walk *walk)
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{
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int err = 0;
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struct vm_area_struct *vma = walk->vma;
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const struct mm_walk_ops *ops = walk->ops;
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if (ops->pre_vma) {
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err = ops->pre_vma(start, end, walk);
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if (err)
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return err;
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}
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if (is_vm_hugetlb_page(vma)) {
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if (ops->hugetlb_entry)
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err = walk_hugetlb_range(start, end, walk);
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} else
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err = walk_pgd_range(start, end, walk);
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if (ops->post_vma)
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ops->post_vma(walk);
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return err;
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}
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/**
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* walk_page_range - walk page table with caller specific callbacks
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* @mm: mm_struct representing the target process of page table walk
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* @start: start address of the virtual address range
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* @end: end address of the virtual address range
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* @ops: operation to call during the walk
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* @private: private data for callbacks' usage
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*
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* Recursively walk the page table tree of the process represented by @mm
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* within the virtual address range [@start, @end). During walking, we can do
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* some caller-specific works for each entry, by setting up pmd_entry(),
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* pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
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* callbacks, the associated entries/pages are just ignored.
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* The return values of these callbacks are commonly defined like below:
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*
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* - 0 : succeeded to handle the current entry, and if you don't reach the
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* end address yet, continue to walk.
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* - >0 : succeeded to handle the current entry, and return to the caller
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* with caller specific value.
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* - <0 : failed to handle the current entry, and return to the caller
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* with error code.
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*
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* Before starting to walk page table, some callers want to check whether
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* they really want to walk over the current vma, typically by checking
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* its vm_flags. walk_page_test() and @ops->test_walk() are used for this
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* purpose.
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*
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* If operations need to be staged before and committed after a vma is walked,
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* there are two callbacks, pre_vma() and post_vma(). Note that post_vma(),
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* since it is intended to handle commit-type operations, can't return any
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* errors.
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*
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* struct mm_walk keeps current values of some common data like vma and pmd,
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* which are useful for the access from callbacks. If you want to pass some
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* caller-specific data to callbacks, @private should be helpful.
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*
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* Locking:
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* Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock,
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* because these function traverse vma list and/or access to vma's data.
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*/
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int walk_page_range(struct mm_struct *mm, unsigned long start,
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unsigned long end, const struct mm_walk_ops *ops,
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void *private)
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{
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int err = 0;
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unsigned long next;
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struct vm_area_struct *vma;
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struct mm_walk walk = {
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.ops = ops,
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.mm = mm,
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.private = private,
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};
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if (start >= end)
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return -EINVAL;
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if (!walk.mm)
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return -EINVAL;
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mmap_assert_locked(walk.mm);
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vma = find_vma(walk.mm, start);
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do {
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if (!vma) { /* after the last vma */
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walk.vma = NULL;
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next = end;
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if (ops->pte_hole)
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err = ops->pte_hole(start, next, -1, &walk);
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} else if (start < vma->vm_start) { /* outside vma */
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walk.vma = NULL;
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next = min(end, vma->vm_start);
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if (ops->pte_hole)
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err = ops->pte_hole(start, next, -1, &walk);
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} else { /* inside vma */
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walk.vma = vma;
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next = min(end, vma->vm_end);
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vma = find_vma(mm, vma->vm_end);
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err = walk_page_test(start, next, &walk);
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if (err > 0) {
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/*
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* positive return values are purely for
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* controlling the pagewalk, so should never
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* be passed to the callers.
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*/
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err = 0;
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continue;
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}
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if (err < 0)
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break;
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err = __walk_page_range(start, next, &walk);
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}
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if (err)
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break;
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} while (start = next, start < end);
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return err;
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}
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/**
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* walk_page_range_novma - walk a range of pagetables not backed by a vma
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* @mm: mm_struct representing the target process of page table walk
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* @start: start address of the virtual address range
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* @end: end address of the virtual address range
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* @ops: operation to call during the walk
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* @pgd: pgd to walk if different from mm->pgd
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* @private: private data for callbacks' usage
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*
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* Similar to walk_page_range() but can walk any page tables even if they are
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* not backed by VMAs. Because 'unusual' entries may be walked this function
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* will also not lock the PTEs for the pte_entry() callback. This is useful for
|
|
* walking the kernel pages tables or page tables for firmware.
|
|
*/
|
|
int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
|
|
unsigned long end, const struct mm_walk_ops *ops,
|
|
pgd_t *pgd,
|
|
void *private)
|
|
{
|
|
struct mm_walk walk = {
|
|
.ops = ops,
|
|
.mm = mm,
|
|
.pgd = pgd,
|
|
.private = private,
|
|
.no_vma = true
|
|
};
|
|
|
|
if (start >= end || !walk.mm)
|
|
return -EINVAL;
|
|
|
|
mmap_assert_write_locked(walk.mm);
|
|
|
|
return walk_pgd_range(start, end, &walk);
|
|
}
|
|
|
|
int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
|
|
unsigned long end, const struct mm_walk_ops *ops,
|
|
void *private)
|
|
{
|
|
struct mm_walk walk = {
|
|
.ops = ops,
|
|
.mm = vma->vm_mm,
|
|
.vma = vma,
|
|
.private = private,
|
|
};
|
|
|
|
if (start >= end || !walk.mm)
|
|
return -EINVAL;
|
|
if (start < vma->vm_start || end > vma->vm_end)
|
|
return -EINVAL;
|
|
|
|
mmap_assert_locked(walk.mm);
|
|
return __walk_page_range(start, end, &walk);
|
|
}
|
|
|
|
int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
|
|
void *private)
|
|
{
|
|
struct mm_walk walk = {
|
|
.ops = ops,
|
|
.mm = vma->vm_mm,
|
|
.vma = vma,
|
|
.private = private,
|
|
};
|
|
|
|
if (!walk.mm)
|
|
return -EINVAL;
|
|
|
|
mmap_assert_locked(walk.mm);
|
|
return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
|
|
}
|
|
|
|
/**
|
|
* walk_page_mapping - walk all memory areas mapped into a struct address_space.
|
|
* @mapping: Pointer to the struct address_space
|
|
* @first_index: First page offset in the address_space
|
|
* @nr: Number of incremental page offsets to cover
|
|
* @ops: operation to call during the walk
|
|
* @private: private data for callbacks' usage
|
|
*
|
|
* This function walks all memory areas mapped into a struct address_space.
|
|
* The walk is limited to only the given page-size index range, but if
|
|
* the index boundaries cross a huge page-table entry, that entry will be
|
|
* included.
|
|
*
|
|
* Also see walk_page_range() for additional information.
|
|
*
|
|
* Locking:
|
|
* This function can't require that the struct mm_struct::mmap_lock is held,
|
|
* since @mapping may be mapped by multiple processes. Instead
|
|
* @mapping->i_mmap_rwsem must be held. This might have implications in the
|
|
* callbacks, and it's up tho the caller to ensure that the
|
|
* struct mm_struct::mmap_lock is not needed.
|
|
*
|
|
* Also this means that a caller can't rely on the struct
|
|
* vm_area_struct::vm_flags to be constant across a call,
|
|
* except for immutable flags. Callers requiring this shouldn't use
|
|
* this function.
|
|
*
|
|
* Return: 0 on success, negative error code on failure, positive number on
|
|
* caller defined premature termination.
|
|
*/
|
|
int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
|
|
pgoff_t nr, const struct mm_walk_ops *ops,
|
|
void *private)
|
|
{
|
|
struct mm_walk walk = {
|
|
.ops = ops,
|
|
.private = private,
|
|
};
|
|
struct vm_area_struct *vma;
|
|
pgoff_t vba, vea, cba, cea;
|
|
unsigned long start_addr, end_addr;
|
|
int err = 0;
|
|
|
|
lockdep_assert_held(&mapping->i_mmap_rwsem);
|
|
vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
|
|
first_index + nr - 1) {
|
|
/* Clip to the vma */
|
|
vba = vma->vm_pgoff;
|
|
vea = vba + vma_pages(vma);
|
|
cba = first_index;
|
|
cba = max(cba, vba);
|
|
cea = first_index + nr;
|
|
cea = min(cea, vea);
|
|
|
|
start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
|
|
end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
|
|
if (start_addr >= end_addr)
|
|
continue;
|
|
|
|
walk.vma = vma;
|
|
walk.mm = vma->vm_mm;
|
|
|
|
err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
|
|
if (err > 0) {
|
|
err = 0;
|
|
break;
|
|
} else if (err < 0)
|
|
break;
|
|
|
|
err = __walk_page_range(start_addr, end_addr, &walk);
|
|
if (err)
|
|
break;
|
|
}
|
|
|
|
return err;
|
|
}
|