mm: move get_user_pages()-related code to separate file
mm/memory.c is overloaded: over 4k lines. get_user_pages() code is pretty much self-contained let's move it to separate file. No other changes made. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Kirill A. Shutemov
Linus Torvalds
parent
f4527c9086
commit
4bbd4c776a
4 changed files with 655 additions and 642 deletions
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@ -3,7 +3,7 @@
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#
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#
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mmu-y := nommu.o
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mmu-y := nommu.o
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mmu-$(CONFIG_MMU) := fremap.o highmem.o madvise.o memory.o mincore.o \
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mmu-$(CONFIG_MMU) := fremap.o gup.o highmem.o madvise.o memory.o mincore.o \
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mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
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mlock.o mmap.o mprotect.o mremap.o msync.o rmap.o \
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vmalloc.o pagewalk.o pgtable-generic.o
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vmalloc.o pagewalk.o pgtable-generic.o
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649
mm/gup.c
Normal file
649
mm/gup.c
Normal file
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@ -0,0 +1,649 @@
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/err.h>
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#include <linux/spinlock.h>
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#include <linux/hugetlb.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <linux/rmap.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include "internal.h"
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/**
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* follow_page_mask - look up a page descriptor from a user-virtual address
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* @vma: vm_area_struct mapping @address
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* @address: virtual address to look up
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* @flags: flags modifying lookup behaviour
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* @page_mask: on output, *page_mask is set according to the size of the page
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*
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* @flags can have FOLL_ flags set, defined in <linux/mm.h>
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*
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* Returns the mapped (struct page *), %NULL if no mapping exists, or
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* an error pointer if there is a mapping to something not represented
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* by a page descriptor (see also vm_normal_page()).
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*/
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struct page *follow_page_mask(struct vm_area_struct *vma,
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unsigned long address, unsigned int flags,
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unsigned int *page_mask)
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{
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *ptep, pte;
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spinlock_t *ptl;
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struct page *page;
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struct mm_struct *mm = vma->vm_mm;
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*page_mask = 0;
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page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
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if (!IS_ERR(page)) {
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BUG_ON(flags & FOLL_GET);
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goto out;
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}
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page = NULL;
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pgd = pgd_offset(mm, address);
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if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
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goto no_page_table;
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pud = pud_offset(pgd, address);
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if (pud_none(*pud))
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goto no_page_table;
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if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
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if (flags & FOLL_GET)
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goto out;
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page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
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goto out;
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}
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if (unlikely(pud_bad(*pud)))
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goto no_page_table;
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pmd = pmd_offset(pud, address);
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if (pmd_none(*pmd))
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goto no_page_table;
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if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
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page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
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if (flags & FOLL_GET) {
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/*
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* Refcount on tail pages are not well-defined and
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* shouldn't be taken. The caller should handle a NULL
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* return when trying to follow tail pages.
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*/
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if (PageHead(page))
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get_page(page);
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else {
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page = NULL;
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goto out;
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}
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}
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goto out;
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}
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if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
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goto no_page_table;
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if (pmd_trans_huge(*pmd)) {
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if (flags & FOLL_SPLIT) {
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split_huge_page_pmd(vma, address, pmd);
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goto split_fallthrough;
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}
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ptl = pmd_lock(mm, pmd);
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if (likely(pmd_trans_huge(*pmd))) {
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if (unlikely(pmd_trans_splitting(*pmd))) {
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spin_unlock(ptl);
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wait_split_huge_page(vma->anon_vma, pmd);
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} else {
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page = follow_trans_huge_pmd(vma, address,
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pmd, flags);
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spin_unlock(ptl);
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*page_mask = HPAGE_PMD_NR - 1;
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goto out;
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}
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} else
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spin_unlock(ptl);
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/* fall through */
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}
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split_fallthrough:
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if (unlikely(pmd_bad(*pmd)))
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goto no_page_table;
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ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
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pte = *ptep;
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if (!pte_present(pte)) {
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swp_entry_t entry;
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/*
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* KSM's break_ksm() relies upon recognizing a ksm page
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* even while it is being migrated, so for that case we
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* need migration_entry_wait().
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*/
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if (likely(!(flags & FOLL_MIGRATION)))
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goto no_page;
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if (pte_none(pte) || pte_file(pte))
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goto no_page;
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entry = pte_to_swp_entry(pte);
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if (!is_migration_entry(entry))
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goto no_page;
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pte_unmap_unlock(ptep, ptl);
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migration_entry_wait(mm, pmd, address);
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goto split_fallthrough;
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}
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if ((flags & FOLL_NUMA) && pte_numa(pte))
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goto no_page;
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if ((flags & FOLL_WRITE) && !pte_write(pte))
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goto unlock;
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page = vm_normal_page(vma, address, pte);
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if (unlikely(!page)) {
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if ((flags & FOLL_DUMP) ||
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!is_zero_pfn(pte_pfn(pte)))
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goto bad_page;
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page = pte_page(pte);
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}
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if (flags & FOLL_GET)
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get_page_foll(page);
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if (flags & FOLL_TOUCH) {
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if ((flags & FOLL_WRITE) &&
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!pte_dirty(pte) && !PageDirty(page))
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set_page_dirty(page);
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/*
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* pte_mkyoung() would be more correct here, but atomic care
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* is needed to avoid losing the dirty bit: it is easier to use
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* mark_page_accessed().
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*/
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mark_page_accessed(page);
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}
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if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
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/*
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* The preliminary mapping check is mainly to avoid the
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* pointless overhead of lock_page on the ZERO_PAGE
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* which might bounce very badly if there is contention.
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*
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* If the page is already locked, we don't need to
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* handle it now - vmscan will handle it later if and
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* when it attempts to reclaim the page.
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*/
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if (page->mapping && trylock_page(page)) {
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lru_add_drain(); /* push cached pages to LRU */
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/*
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* Because we lock page here, and migration is
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* blocked by the pte's page reference, and we
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* know the page is still mapped, we don't even
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* need to check for file-cache page truncation.
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*/
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mlock_vma_page(page);
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unlock_page(page);
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}
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}
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unlock:
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pte_unmap_unlock(ptep, ptl);
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out:
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return page;
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bad_page:
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pte_unmap_unlock(ptep, ptl);
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return ERR_PTR(-EFAULT);
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no_page:
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pte_unmap_unlock(ptep, ptl);
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if (!pte_none(pte))
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return page;
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no_page_table:
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/*
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* When core dumping an enormous anonymous area that nobody
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* has touched so far, we don't want to allocate unnecessary pages or
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* page tables. Return error instead of NULL to skip handle_mm_fault,
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* then get_dump_page() will return NULL to leave a hole in the dump.
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* But we can only make this optimization where a hole would surely
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* be zero-filled if handle_mm_fault() actually did handle it.
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*/
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if ((flags & FOLL_DUMP) &&
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(!vma->vm_ops || !vma->vm_ops->fault))
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return ERR_PTR(-EFAULT);
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return page;
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}
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static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
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{
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return stack_guard_page_start(vma, addr) ||
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stack_guard_page_end(vma, addr+PAGE_SIZE);
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}
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/**
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* __get_user_pages() - pin user pages in memory
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* @tsk: task_struct of target task
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* @mm: mm_struct of target mm
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* @start: starting user address
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* @nr_pages: number of pages from start to pin
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* @gup_flags: flags modifying pin behaviour
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* @pages: array that receives pointers to the pages pinned.
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* Should be at least nr_pages long. Or NULL, if caller
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* only intends to ensure the pages are faulted in.
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* @vmas: array of pointers to vmas corresponding to each page.
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* Or NULL if the caller does not require them.
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* @nonblocking: whether waiting for disk IO or mmap_sem contention
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*
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* Returns number of pages pinned. This may be fewer than the number
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* requested. If nr_pages is 0 or negative, returns 0. If no pages
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* were pinned, returns -errno. Each page returned must be released
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* with a put_page() call when it is finished with. vmas will only
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* remain valid while mmap_sem is held.
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*
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* Must be called with mmap_sem held for read or write.
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*
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* __get_user_pages walks a process's page tables and takes a reference to
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* each struct page that each user address corresponds to at a given
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* instant. That is, it takes the page that would be accessed if a user
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* thread accesses the given user virtual address at that instant.
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*
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* This does not guarantee that the page exists in the user mappings when
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* __get_user_pages returns, and there may even be a completely different
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* page there in some cases (eg. if mmapped pagecache has been invalidated
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* and subsequently re faulted). However it does guarantee that the page
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* won't be freed completely. And mostly callers simply care that the page
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* contains data that was valid *at some point in time*. Typically, an IO
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* or similar operation cannot guarantee anything stronger anyway because
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* locks can't be held over the syscall boundary.
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*
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* If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
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* the page is written to, set_page_dirty (or set_page_dirty_lock, as
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* appropriate) must be called after the page is finished with, and
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* before put_page is called.
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*
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* If @nonblocking != NULL, __get_user_pages will not wait for disk IO
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* or mmap_sem contention, and if waiting is needed to pin all pages,
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* *@nonblocking will be set to 0.
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*
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* In most cases, get_user_pages or get_user_pages_fast should be used
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* instead of __get_user_pages. __get_user_pages should be used only if
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* you need some special @gup_flags.
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*/
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long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
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unsigned long start, unsigned long nr_pages,
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unsigned int gup_flags, struct page **pages,
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struct vm_area_struct **vmas, int *nonblocking)
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{
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long i;
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unsigned long vm_flags;
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unsigned int page_mask;
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if (!nr_pages)
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return 0;
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VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
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/*
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* If FOLL_FORCE is set then do not force a full fault as the hinting
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* fault information is unrelated to the reference behaviour of a task
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* using the address space
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*/
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if (!(gup_flags & FOLL_FORCE))
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gup_flags |= FOLL_NUMA;
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i = 0;
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|
|
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do {
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struct vm_area_struct *vma;
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|
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vma = find_extend_vma(mm, start);
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if (!vma && in_gate_area(mm, start)) {
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unsigned long pg = start & PAGE_MASK;
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pgd_t *pgd;
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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|
|
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/* user gate pages are read-only */
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if (gup_flags & FOLL_WRITE)
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goto efault;
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if (pg > TASK_SIZE)
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pgd = pgd_offset_k(pg);
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|
else
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pgd = pgd_offset_gate(mm, pg);
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BUG_ON(pgd_none(*pgd));
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pud = pud_offset(pgd, pg);
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BUG_ON(pud_none(*pud));
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|
pmd = pmd_offset(pud, pg);
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|
if (pmd_none(*pmd))
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|
goto efault;
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|
VM_BUG_ON(pmd_trans_huge(*pmd));
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pte = pte_offset_map(pmd, pg);
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|
if (pte_none(*pte)) {
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|
pte_unmap(pte);
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|
goto efault;
|
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|
}
|
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|
vma = get_gate_vma(mm);
|
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|
if (pages) {
|
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|
struct page *page;
|
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|
|
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page = vm_normal_page(vma, start, *pte);
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|
if (!page) {
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|
if (!(gup_flags & FOLL_DUMP) &&
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|
is_zero_pfn(pte_pfn(*pte)))
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|
page = pte_page(*pte);
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|
else {
|
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|
pte_unmap(pte);
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|
goto efault;
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|
}
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}
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|
pages[i] = page;
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|
get_page(page);
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}
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|
pte_unmap(pte);
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|
page_mask = 0;
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|
goto next_page;
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||||||
|
}
|
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|
|
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|
if (!vma)
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|
goto efault;
|
||||||
|
vm_flags = vma->vm_flags;
|
||||||
|
if (vm_flags & (VM_IO | VM_PFNMAP))
|
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|
goto efault;
|
||||||
|
|
||||||
|
if (gup_flags & FOLL_WRITE) {
|
||||||
|
if (!(vm_flags & VM_WRITE)) {
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|
if (!(gup_flags & FOLL_FORCE))
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goto efault;
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||||||
|
/*
|
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|
* We used to let the write,force case do COW
|
||||||
|
* in a VM_MAYWRITE VM_SHARED !VM_WRITE vma, so
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||||||
|
* ptrace could set a breakpoint in a read-only
|
||||||
|
* mapping of an executable, without corrupting
|
||||||
|
* the file (yet only when that file had been
|
||||||
|
* opened for writing!). Anon pages in shared
|
||||||
|
* mappings are surprising: now just reject it.
|
||||||
|
*/
|
||||||
|
if (!is_cow_mapping(vm_flags)) {
|
||||||
|
WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
|
||||||
|
goto efault;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
} else {
|
||||||
|
if (!(vm_flags & VM_READ)) {
|
||||||
|
if (!(gup_flags & FOLL_FORCE))
|
||||||
|
goto efault;
|
||||||
|
/*
|
||||||
|
* Is there actually any vma we can reach here
|
||||||
|
* which does not have VM_MAYREAD set?
|
||||||
|
*/
|
||||||
|
if (!(vm_flags & VM_MAYREAD))
|
||||||
|
goto efault;
|
||||||
|
}
|
||||||
|
}
|
||||||
|
|
||||||
|
if (is_vm_hugetlb_page(vma)) {
|
||||||
|
i = follow_hugetlb_page(mm, vma, pages, vmas,
|
||||||
|
&start, &nr_pages, i, gup_flags);
|
||||||
|
continue;
|
||||||
|
}
|
||||||
|
|
||||||
|
do {
|
||||||
|
struct page *page;
|
||||||
|
unsigned int foll_flags = gup_flags;
|
||||||
|
unsigned int page_increm;
|
||||||
|
|
||||||
|
/*
|
||||||
|
* If we have a pending SIGKILL, don't keep faulting
|
||||||
|
* pages and potentially allocating memory.
|
||||||
|
*/
|
||||||
|
if (unlikely(fatal_signal_pending(current)))
|
||||||
|
return i ? i : -ERESTARTSYS;
|
||||||
|
|
||||||
|
cond_resched();
|
||||||
|
while (!(page = follow_page_mask(vma, start,
|
||||||
|
foll_flags, &page_mask))) {
|
||||||
|
int ret;
|
||||||
|
unsigned int fault_flags = 0;
|
||||||
|
|
||||||
|
/* For mlock, just skip the stack guard page. */
|
||||||
|
if (foll_flags & FOLL_MLOCK) {
|
||||||
|
if (stack_guard_page(vma, start))
|
||||||
|
goto next_page;
|
||||||
|
}
|
||||||
|
if (foll_flags & FOLL_WRITE)
|
||||||
|
fault_flags |= FAULT_FLAG_WRITE;
|
||||||
|
if (nonblocking)
|
||||||
|
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
|
||||||
|
if (foll_flags & FOLL_NOWAIT)
|
||||||
|
fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
|
||||||
|
|
||||||
|
ret = handle_mm_fault(mm, vma, start,
|
||||||
|
fault_flags);
|
||||||
|
|
||||||
|
if (ret & VM_FAULT_ERROR) {
|
||||||
|
if (ret & VM_FAULT_OOM)
|
||||||
|
return i ? i : -ENOMEM;
|
||||||
|
if (ret & (VM_FAULT_HWPOISON |
|
||||||
|
VM_FAULT_HWPOISON_LARGE)) {
|
||||||
|
if (i)
|
||||||
|
return i;
|
||||||
|
else if (gup_flags & FOLL_HWPOISON)
|
||||||
|
return -EHWPOISON;
|
||||||
|
else
|
||||||
|
return -EFAULT;
|
||||||
|
}
|
||||||
|
if (ret & VM_FAULT_SIGBUS)
|
||||||
|
goto efault;
|
||||||
|
BUG();
|
||||||
|
}
|
||||||
|
|
||||||
|
if (tsk) {
|
||||||
|
if (ret & VM_FAULT_MAJOR)
|
||||||
|
tsk->maj_flt++;
|
||||||
|
else
|
||||||
|
tsk->min_flt++;
|
||||||
|
}
|
||||||
|
|
||||||
|
if (ret & VM_FAULT_RETRY) {
|
||||||
|
if (nonblocking)
|
||||||
|
*nonblocking = 0;
|
||||||
|
return i;
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* The VM_FAULT_WRITE bit tells us that
|
||||||
|
* do_wp_page has broken COW when necessary,
|
||||||
|
* even if maybe_mkwrite decided not to set
|
||||||
|
* pte_write. We can thus safely do subsequent
|
||||||
|
* page lookups as if they were reads. But only
|
||||||
|
* do so when looping for pte_write is futile:
|
||||||
|
* in some cases userspace may also be wanting
|
||||||
|
* to write to the gotten user page, which a
|
||||||
|
* read fault here might prevent (a readonly
|
||||||
|
* page might get reCOWed by userspace write).
|
||||||
|
*/
|
||||||
|
if ((ret & VM_FAULT_WRITE) &&
|
||||||
|
!(vma->vm_flags & VM_WRITE))
|
||||||
|
foll_flags &= ~FOLL_WRITE;
|
||||||
|
|
||||||
|
cond_resched();
|
||||||
|
}
|
||||||
|
if (IS_ERR(page))
|
||||||
|
return i ? i : PTR_ERR(page);
|
||||||
|
if (pages) {
|
||||||
|
pages[i] = page;
|
||||||
|
|
||||||
|
flush_anon_page(vma, page, start);
|
||||||
|
flush_dcache_page(page);
|
||||||
|
page_mask = 0;
|
||||||
|
}
|
||||||
|
next_page:
|
||||||
|
if (vmas) {
|
||||||
|
vmas[i] = vma;
|
||||||
|
page_mask = 0;
|
||||||
|
}
|
||||||
|
page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
|
||||||
|
if (page_increm > nr_pages)
|
||||||
|
page_increm = nr_pages;
|
||||||
|
i += page_increm;
|
||||||
|
start += page_increm * PAGE_SIZE;
|
||||||
|
nr_pages -= page_increm;
|
||||||
|
} while (nr_pages && start < vma->vm_end);
|
||||||
|
} while (nr_pages);
|
||||||
|
return i;
|
||||||
|
efault:
|
||||||
|
return i ? : -EFAULT;
|
||||||
|
}
|
||||||
|
EXPORT_SYMBOL(__get_user_pages);
|
||||||
|
|
||||||
|
/*
|
||||||
|
* fixup_user_fault() - manually resolve a user page fault
|
||||||
|
* @tsk: the task_struct to use for page fault accounting, or
|
||||||
|
* NULL if faults are not to be recorded.
|
||||||
|
* @mm: mm_struct of target mm
|
||||||
|
* @address: user address
|
||||||
|
* @fault_flags:flags to pass down to handle_mm_fault()
|
||||||
|
*
|
||||||
|
* This is meant to be called in the specific scenario where for locking reasons
|
||||||
|
* we try to access user memory in atomic context (within a pagefault_disable()
|
||||||
|
* section), this returns -EFAULT, and we want to resolve the user fault before
|
||||||
|
* trying again.
|
||||||
|
*
|
||||||
|
* Typically this is meant to be used by the futex code.
|
||||||
|
*
|
||||||
|
* The main difference with get_user_pages() is that this function will
|
||||||
|
* unconditionally call handle_mm_fault() which will in turn perform all the
|
||||||
|
* necessary SW fixup of the dirty and young bits in the PTE, while
|
||||||
|
* handle_mm_fault() only guarantees to update these in the struct page.
|
||||||
|
*
|
||||||
|
* This is important for some architectures where those bits also gate the
|
||||||
|
* access permission to the page because they are maintained in software. On
|
||||||
|
* such architectures, gup() will not be enough to make a subsequent access
|
||||||
|
* succeed.
|
||||||
|
*
|
||||||
|
* This should be called with the mm_sem held for read.
|
||||||
|
*/
|
||||||
|
int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
|
||||||
|
unsigned long address, unsigned int fault_flags)
|
||||||
|
{
|
||||||
|
struct vm_area_struct *vma;
|
||||||
|
vm_flags_t vm_flags;
|
||||||
|
int ret;
|
||||||
|
|
||||||
|
vma = find_extend_vma(mm, address);
|
||||||
|
if (!vma || address < vma->vm_start)
|
||||||
|
return -EFAULT;
|
||||||
|
|
||||||
|
vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
|
||||||
|
if (!(vm_flags & vma->vm_flags))
|
||||||
|
return -EFAULT;
|
||||||
|
|
||||||
|
ret = handle_mm_fault(mm, vma, address, fault_flags);
|
||||||
|
if (ret & VM_FAULT_ERROR) {
|
||||||
|
if (ret & VM_FAULT_OOM)
|
||||||
|
return -ENOMEM;
|
||||||
|
if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
|
||||||
|
return -EHWPOISON;
|
||||||
|
if (ret & VM_FAULT_SIGBUS)
|
||||||
|
return -EFAULT;
|
||||||
|
BUG();
|
||||||
|
}
|
||||||
|
if (tsk) {
|
||||||
|
if (ret & VM_FAULT_MAJOR)
|
||||||
|
tsk->maj_flt++;
|
||||||
|
else
|
||||||
|
tsk->min_flt++;
|
||||||
|
}
|
||||||
|
return 0;
|
||||||
|
}
|
||||||
|
|
||||||
|
/*
|
||||||
|
* get_user_pages() - pin user pages in memory
|
||||||
|
* @tsk: the task_struct to use for page fault accounting, or
|
||||||
|
* NULL if faults are not to be recorded.
|
||||||
|
* @mm: mm_struct of target mm
|
||||||
|
* @start: starting user address
|
||||||
|
* @nr_pages: number of pages from start to pin
|
||||||
|
* @write: whether pages will be written to by the caller
|
||||||
|
* @force: whether to force access even when user mapping is currently
|
||||||
|
* protected (but never forces write access to shared mapping).
|
||||||
|
* @pages: array that receives pointers to the pages pinned.
|
||||||
|
* Should be at least nr_pages long. Or NULL, if caller
|
||||||
|
* only intends to ensure the pages are faulted in.
|
||||||
|
* @vmas: array of pointers to vmas corresponding to each page.
|
||||||
|
* Or NULL if the caller does not require them.
|
||||||
|
*
|
||||||
|
* Returns number of pages pinned. This may be fewer than the number
|
||||||
|
* requested. If nr_pages is 0 or negative, returns 0. If no pages
|
||||||
|
* were pinned, returns -errno. Each page returned must be released
|
||||||
|
* with a put_page() call when it is finished with. vmas will only
|
||||||
|
* remain valid while mmap_sem is held.
|
||||||
|
*
|
||||||
|
* Must be called with mmap_sem held for read or write.
|
||||||
|
*
|
||||||
|
* get_user_pages walks a process's page tables and takes a reference to
|
||||||
|
* each struct page that each user address corresponds to at a given
|
||||||
|
* instant. That is, it takes the page that would be accessed if a user
|
||||||
|
* thread accesses the given user virtual address at that instant.
|
||||||
|
*
|
||||||
|
* This does not guarantee that the page exists in the user mappings when
|
||||||
|
* get_user_pages returns, and there may even be a completely different
|
||||||
|
* page there in some cases (eg. if mmapped pagecache has been invalidated
|
||||||
|
* and subsequently re faulted). However it does guarantee that the page
|
||||||
|
* won't be freed completely. And mostly callers simply care that the page
|
||||||
|
* contains data that was valid *at some point in time*. Typically, an IO
|
||||||
|
* or similar operation cannot guarantee anything stronger anyway because
|
||||||
|
* locks can't be held over the syscall boundary.
|
||||||
|
*
|
||||||
|
* If write=0, the page must not be written to. If the page is written to,
|
||||||
|
* set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
|
||||||
|
* after the page is finished with, and before put_page is called.
|
||||||
|
*
|
||||||
|
* get_user_pages is typically used for fewer-copy IO operations, to get a
|
||||||
|
* handle on the memory by some means other than accesses via the user virtual
|
||||||
|
* addresses. The pages may be submitted for DMA to devices or accessed via
|
||||||
|
* their kernel linear mapping (via the kmap APIs). Care should be taken to
|
||||||
|
* use the correct cache flushing APIs.
|
||||||
|
*
|
||||||
|
* See also get_user_pages_fast, for performance critical applications.
|
||||||
|
*/
|
||||||
|
long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
|
||||||
|
unsigned long start, unsigned long nr_pages, int write,
|
||||||
|
int force, struct page **pages, struct vm_area_struct **vmas)
|
||||||
|
{
|
||||||
|
int flags = FOLL_TOUCH;
|
||||||
|
|
||||||
|
if (pages)
|
||||||
|
flags |= FOLL_GET;
|
||||||
|
if (write)
|
||||||
|
flags |= FOLL_WRITE;
|
||||||
|
if (force)
|
||||||
|
flags |= FOLL_FORCE;
|
||||||
|
|
||||||
|
return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
|
||||||
|
NULL);
|
||||||
|
}
|
||||||
|
EXPORT_SYMBOL(get_user_pages);
|
||||||
|
|
||||||
|
/**
|
||||||
|
* get_dump_page() - pin user page in memory while writing it to core dump
|
||||||
|
* @addr: user address
|
||||||
|
*
|
||||||
|
* Returns struct page pointer of user page pinned for dump,
|
||||||
|
* to be freed afterwards by page_cache_release() or put_page().
|
||||||
|
*
|
||||||
|
* Returns NULL on any kind of failure - a hole must then be inserted into
|
||||||
|
* the corefile, to preserve alignment with its headers; and also returns
|
||||||
|
* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
|
||||||
|
* allowing a hole to be left in the corefile to save diskspace.
|
||||||
|
*
|
||||||
|
* Called without mmap_sem, but after all other threads have been killed.
|
||||||
|
*/
|
||||||
|
#ifdef CONFIG_ELF_CORE
|
||||||
|
struct page *get_dump_page(unsigned long addr)
|
||||||
|
{
|
||||||
|
struct vm_area_struct *vma;
|
||||||
|
struct page *page;
|
||||||
|
|
||||||
|
if (__get_user_pages(current, current->mm, addr, 1,
|
||||||
|
FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
|
||||||
|
NULL) < 1)
|
||||||
|
return NULL;
|
||||||
|
flush_cache_page(vma, addr, page_to_pfn(page));
|
||||||
|
return page;
|
||||||
|
}
|
||||||
|
#endif /* CONFIG_ELF_CORE */
|
||||||
|
|
@ -169,6 +169,11 @@ static inline unsigned long page_order(struct page *page)
|
||||||
return page_private(page);
|
return page_private(page);
|
||||||
}
|
}
|
||||||
|
|
||||||
|
static inline bool is_cow_mapping(vm_flags_t flags)
|
||||||
|
{
|
||||||
|
return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
|
||||||
|
}
|
||||||
|
|
||||||
/* mm/util.c */
|
/* mm/util.c */
|
||||||
void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
|
void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
|
||||||
struct vm_area_struct *prev, struct rb_node *rb_parent);
|
struct vm_area_struct *prev, struct rb_node *rb_parent);
|
||||||
|
|
|
||||||
641
mm/memory.c
641
mm/memory.c
|
|
@ -698,11 +698,6 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
|
||||||
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
|
add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
|
||||||
}
|
}
|
||||||
|
|
||||||
static inline bool is_cow_mapping(vm_flags_t flags)
|
|
||||||
{
|
|
||||||
return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
/*
|
||||||
* vm_normal_page -- This function gets the "struct page" associated with a pte.
|
* vm_normal_page -- This function gets the "struct page" associated with a pte.
|
||||||
*
|
*
|
||||||
|
|
@ -1458,642 +1453,6 @@ int zap_vma_ptes(struct vm_area_struct *vma, unsigned long address,
|
||||||
}
|
}
|
||||||
EXPORT_SYMBOL_GPL(zap_vma_ptes);
|
EXPORT_SYMBOL_GPL(zap_vma_ptes);
|
||||||
|
|
||||||
/**
|
|
||||||
* follow_page_mask - look up a page descriptor from a user-virtual address
|
|
||||||
* @vma: vm_area_struct mapping @address
|
|
||||||
* @address: virtual address to look up
|
|
||||||
* @flags: flags modifying lookup behaviour
|
|
||||||
* @page_mask: on output, *page_mask is set according to the size of the page
|
|
||||||
*
|
|
||||||
* @flags can have FOLL_ flags set, defined in <linux/mm.h>
|
|
||||||
*
|
|
||||||
* Returns the mapped (struct page *), %NULL if no mapping exists, or
|
|
||||||
* an error pointer if there is a mapping to something not represented
|
|
||||||
* by a page descriptor (see also vm_normal_page()).
|
|
||||||
*/
|
|
||||||
struct page *follow_page_mask(struct vm_area_struct *vma,
|
|
||||||
unsigned long address, unsigned int flags,
|
|
||||||
unsigned int *page_mask)
|
|
||||||
{
|
|
||||||
pgd_t *pgd;
|
|
||||||
pud_t *pud;
|
|
||||||
pmd_t *pmd;
|
|
||||||
pte_t *ptep, pte;
|
|
||||||
spinlock_t *ptl;
|
|
||||||
struct page *page;
|
|
||||||
struct mm_struct *mm = vma->vm_mm;
|
|
||||||
|
|
||||||
*page_mask = 0;
|
|
||||||
|
|
||||||
page = follow_huge_addr(mm, address, flags & FOLL_WRITE);
|
|
||||||
if (!IS_ERR(page)) {
|
|
||||||
BUG_ON(flags & FOLL_GET);
|
|
||||||
goto out;
|
|
||||||
}
|
|
||||||
|
|
||||||
page = NULL;
|
|
||||||
pgd = pgd_offset(mm, address);
|
|
||||||
if (pgd_none(*pgd) || unlikely(pgd_bad(*pgd)))
|
|
||||||
goto no_page_table;
|
|
||||||
|
|
||||||
pud = pud_offset(pgd, address);
|
|
||||||
if (pud_none(*pud))
|
|
||||||
goto no_page_table;
|
|
||||||
if (pud_huge(*pud) && vma->vm_flags & VM_HUGETLB) {
|
|
||||||
if (flags & FOLL_GET)
|
|
||||||
goto out;
|
|
||||||
page = follow_huge_pud(mm, address, pud, flags & FOLL_WRITE);
|
|
||||||
goto out;
|
|
||||||
}
|
|
||||||
if (unlikely(pud_bad(*pud)))
|
|
||||||
goto no_page_table;
|
|
||||||
|
|
||||||
pmd = pmd_offset(pud, address);
|
|
||||||
if (pmd_none(*pmd))
|
|
||||||
goto no_page_table;
|
|
||||||
if (pmd_huge(*pmd) && vma->vm_flags & VM_HUGETLB) {
|
|
||||||
page = follow_huge_pmd(mm, address, pmd, flags & FOLL_WRITE);
|
|
||||||
if (flags & FOLL_GET) {
|
|
||||||
/*
|
|
||||||
* Refcount on tail pages are not well-defined and
|
|
||||||
* shouldn't be taken. The caller should handle a NULL
|
|
||||||
* return when trying to follow tail pages.
|
|
||||||
*/
|
|
||||||
if (PageHead(page))
|
|
||||||
get_page(page);
|
|
||||||
else {
|
|
||||||
page = NULL;
|
|
||||||
goto out;
|
|
||||||
}
|
|
||||||
}
|
|
||||||
goto out;
|
|
||||||
}
|
|
||||||
if ((flags & FOLL_NUMA) && pmd_numa(*pmd))
|
|
||||||
goto no_page_table;
|
|
||||||
if (pmd_trans_huge(*pmd)) {
|
|
||||||
if (flags & FOLL_SPLIT) {
|
|
||||||
split_huge_page_pmd(vma, address, pmd);
|
|
||||||
goto split_fallthrough;
|
|
||||||
}
|
|
||||||
ptl = pmd_lock(mm, pmd);
|
|
||||||
if (likely(pmd_trans_huge(*pmd))) {
|
|
||||||
if (unlikely(pmd_trans_splitting(*pmd))) {
|
|
||||||
spin_unlock(ptl);
|
|
||||||
wait_split_huge_page(vma->anon_vma, pmd);
|
|
||||||
} else {
|
|
||||||
page = follow_trans_huge_pmd(vma, address,
|
|
||||||
pmd, flags);
|
|
||||||
spin_unlock(ptl);
|
|
||||||
*page_mask = HPAGE_PMD_NR - 1;
|
|
||||||
goto out;
|
|
||||||
}
|
|
||||||
} else
|
|
||||||
spin_unlock(ptl);
|
|
||||||
/* fall through */
|
|
||||||
}
|
|
||||||
split_fallthrough:
|
|
||||||
if (unlikely(pmd_bad(*pmd)))
|
|
||||||
goto no_page_table;
|
|
||||||
|
|
||||||
ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
|
|
||||||
|
|
||||||
pte = *ptep;
|
|
||||||
if (!pte_present(pte)) {
|
|
||||||
swp_entry_t entry;
|
|
||||||
/*
|
|
||||||
* KSM's break_ksm() relies upon recognizing a ksm page
|
|
||||||
* even while it is being migrated, so for that case we
|
|
||||||
* need migration_entry_wait().
|
|
||||||
*/
|
|
||||||
if (likely(!(flags & FOLL_MIGRATION)))
|
|
||||||
goto no_page;
|
|
||||||
if (pte_none(pte) || pte_file(pte))
|
|
||||||
goto no_page;
|
|
||||||
entry = pte_to_swp_entry(pte);
|
|
||||||
if (!is_migration_entry(entry))
|
|
||||||
goto no_page;
|
|
||||||
pte_unmap_unlock(ptep, ptl);
|
|
||||||
migration_entry_wait(mm, pmd, address);
|
|
||||||
goto split_fallthrough;
|
|
||||||
}
|
|
||||||
if ((flags & FOLL_NUMA) && pte_numa(pte))
|
|
||||||
goto no_page;
|
|
||||||
if ((flags & FOLL_WRITE) && !pte_write(pte))
|
|
||||||
goto unlock;
|
|
||||||
|
|
||||||
page = vm_normal_page(vma, address, pte);
|
|
||||||
if (unlikely(!page)) {
|
|
||||||
if ((flags & FOLL_DUMP) ||
|
|
||||||
!is_zero_pfn(pte_pfn(pte)))
|
|
||||||
goto bad_page;
|
|
||||||
page = pte_page(pte);
|
|
||||||
}
|
|
||||||
|
|
||||||
if (flags & FOLL_GET)
|
|
||||||
get_page_foll(page);
|
|
||||||
if (flags & FOLL_TOUCH) {
|
|
||||||
if ((flags & FOLL_WRITE) &&
|
|
||||||
!pte_dirty(pte) && !PageDirty(page))
|
|
||||||
set_page_dirty(page);
|
|
||||||
/*
|
|
||||||
* pte_mkyoung() would be more correct here, but atomic care
|
|
||||||
* is needed to avoid losing the dirty bit: it is easier to use
|
|
||||||
* mark_page_accessed().
|
|
||||||
*/
|
|
||||||
mark_page_accessed(page);
|
|
||||||
}
|
|
||||||
if ((flags & FOLL_MLOCK) && (vma->vm_flags & VM_LOCKED)) {
|
|
||||||
/*
|
|
||||||
* The preliminary mapping check is mainly to avoid the
|
|
||||||
* pointless overhead of lock_page on the ZERO_PAGE
|
|
||||||
* which might bounce very badly if there is contention.
|
|
||||||
*
|
|
||||||
* If the page is already locked, we don't need to
|
|
||||||
* handle it now - vmscan will handle it later if and
|
|
||||||
* when it attempts to reclaim the page.
|
|
||||||
*/
|
|
||||||
if (page->mapping && trylock_page(page)) {
|
|
||||||
lru_add_drain(); /* push cached pages to LRU */
|
|
||||||
/*
|
|
||||||
* Because we lock page here, and migration is
|
|
||||||
* blocked by the pte's page reference, and we
|
|
||||||
* know the page is still mapped, we don't even
|
|
||||||
* need to check for file-cache page truncation.
|
|
||||||
*/
|
|
||||||
mlock_vma_page(page);
|
|
||||||
unlock_page(page);
|
|
||||||
}
|
|
||||||
}
|
|
||||||
unlock:
|
|
||||||
pte_unmap_unlock(ptep, ptl);
|
|
||||||
out:
|
|
||||||
return page;
|
|
||||||
|
|
||||||
bad_page:
|
|
||||||
pte_unmap_unlock(ptep, ptl);
|
|
||||||
return ERR_PTR(-EFAULT);
|
|
||||||
|
|
||||||
no_page:
|
|
||||||
pte_unmap_unlock(ptep, ptl);
|
|
||||||
if (!pte_none(pte))
|
|
||||||
return page;
|
|
||||||
|
|
||||||
no_page_table:
|
|
||||||
/*
|
|
||||||
* When core dumping an enormous anonymous area that nobody
|
|
||||||
* has touched so far, we don't want to allocate unnecessary pages or
|
|
||||||
* page tables. Return error instead of NULL to skip handle_mm_fault,
|
|
||||||
* then get_dump_page() will return NULL to leave a hole in the dump.
|
|
||||||
* But we can only make this optimization where a hole would surely
|
|
||||||
* be zero-filled if handle_mm_fault() actually did handle it.
|
|
||||||
*/
|
|
||||||
if ((flags & FOLL_DUMP) &&
|
|
||||||
(!vma->vm_ops || !vma->vm_ops->fault))
|
|
||||||
return ERR_PTR(-EFAULT);
|
|
||||||
return page;
|
|
||||||
}
|
|
||||||
|
|
||||||
static inline int stack_guard_page(struct vm_area_struct *vma, unsigned long addr)
|
|
||||||
{
|
|
||||||
return stack_guard_page_start(vma, addr) ||
|
|
||||||
stack_guard_page_end(vma, addr+PAGE_SIZE);
|
|
||||||
}
|
|
||||||
|
|
||||||
/**
|
|
||||||
* __get_user_pages() - pin user pages in memory
|
|
||||||
* @tsk: task_struct of target task
|
|
||||||
* @mm: mm_struct of target mm
|
|
||||||
* @start: starting user address
|
|
||||||
* @nr_pages: number of pages from start to pin
|
|
||||||
* @gup_flags: flags modifying pin behaviour
|
|
||||||
* @pages: array that receives pointers to the pages pinned.
|
|
||||||
* Should be at least nr_pages long. Or NULL, if caller
|
|
||||||
* only intends to ensure the pages are faulted in.
|
|
||||||
* @vmas: array of pointers to vmas corresponding to each page.
|
|
||||||
* Or NULL if the caller does not require them.
|
|
||||||
* @nonblocking: whether waiting for disk IO or mmap_sem contention
|
|
||||||
*
|
|
||||||
* Returns number of pages pinned. This may be fewer than the number
|
|
||||||
* requested. If nr_pages is 0 or negative, returns 0. If no pages
|
|
||||||
* were pinned, returns -errno. Each page returned must be released
|
|
||||||
* with a put_page() call when it is finished with. vmas will only
|
|
||||||
* remain valid while mmap_sem is held.
|
|
||||||
*
|
|
||||||
* Must be called with mmap_sem held for read or write.
|
|
||||||
*
|
|
||||||
* __get_user_pages walks a process's page tables and takes a reference to
|
|
||||||
* each struct page that each user address corresponds to at a given
|
|
||||||
* instant. That is, it takes the page that would be accessed if a user
|
|
||||||
* thread accesses the given user virtual address at that instant.
|
|
||||||
*
|
|
||||||
* This does not guarantee that the page exists in the user mappings when
|
|
||||||
* __get_user_pages returns, and there may even be a completely different
|
|
||||||
* page there in some cases (eg. if mmapped pagecache has been invalidated
|
|
||||||
* and subsequently re faulted). However it does guarantee that the page
|
|
||||||
* won't be freed completely. And mostly callers simply care that the page
|
|
||||||
* contains data that was valid *at some point in time*. Typically, an IO
|
|
||||||
* or similar operation cannot guarantee anything stronger anyway because
|
|
||||||
* locks can't be held over the syscall boundary.
|
|
||||||
*
|
|
||||||
* If @gup_flags & FOLL_WRITE == 0, the page must not be written to. If
|
|
||||||
* the page is written to, set_page_dirty (or set_page_dirty_lock, as
|
|
||||||
* appropriate) must be called after the page is finished with, and
|
|
||||||
* before put_page is called.
|
|
||||||
*
|
|
||||||
* If @nonblocking != NULL, __get_user_pages will not wait for disk IO
|
|
||||||
* or mmap_sem contention, and if waiting is needed to pin all pages,
|
|
||||||
* *@nonblocking will be set to 0.
|
|
||||||
*
|
|
||||||
* In most cases, get_user_pages or get_user_pages_fast should be used
|
|
||||||
* instead of __get_user_pages. __get_user_pages should be used only if
|
|
||||||
* you need some special @gup_flags.
|
|
||||||
*/
|
|
||||||
long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
|
|
||||||
unsigned long start, unsigned long nr_pages,
|
|
||||||
unsigned int gup_flags, struct page **pages,
|
|
||||||
struct vm_area_struct **vmas, int *nonblocking)
|
|
||||||
{
|
|
||||||
long i;
|
|
||||||
unsigned long vm_flags;
|
|
||||||
unsigned int page_mask;
|
|
||||||
|
|
||||||
if (!nr_pages)
|
|
||||||
return 0;
|
|
||||||
|
|
||||||
VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
|
|
||||||
|
|
||||||
/*
|
|
||||||
* If FOLL_FORCE is set then do not force a full fault as the hinting
|
|
||||||
* fault information is unrelated to the reference behaviour of a task
|
|
||||||
* using the address space
|
|
||||||
*/
|
|
||||||
if (!(gup_flags & FOLL_FORCE))
|
|
||||||
gup_flags |= FOLL_NUMA;
|
|
||||||
|
|
||||||
i = 0;
|
|
||||||
|
|
||||||
do {
|
|
||||||
struct vm_area_struct *vma;
|
|
||||||
|
|
||||||
vma = find_extend_vma(mm, start);
|
|
||||||
if (!vma && in_gate_area(mm, start)) {
|
|
||||||
unsigned long pg = start & PAGE_MASK;
|
|
||||||
pgd_t *pgd;
|
|
||||||
pud_t *pud;
|
|
||||||
pmd_t *pmd;
|
|
||||||
pte_t *pte;
|
|
||||||
|
|
||||||
/* user gate pages are read-only */
|
|
||||||
if (gup_flags & FOLL_WRITE)
|
|
||||||
goto efault;
|
|
||||||
if (pg > TASK_SIZE)
|
|
||||||
pgd = pgd_offset_k(pg);
|
|
||||||
else
|
|
||||||
pgd = pgd_offset_gate(mm, pg);
|
|
||||||
BUG_ON(pgd_none(*pgd));
|
|
||||||
pud = pud_offset(pgd, pg);
|
|
||||||
BUG_ON(pud_none(*pud));
|
|
||||||
pmd = pmd_offset(pud, pg);
|
|
||||||
if (pmd_none(*pmd))
|
|
||||||
goto efault;
|
|
||||||
VM_BUG_ON(pmd_trans_huge(*pmd));
|
|
||||||
pte = pte_offset_map(pmd, pg);
|
|
||||||
if (pte_none(*pte)) {
|
|
||||||
pte_unmap(pte);
|
|
||||||
goto efault;
|
|
||||||
}
|
|
||||||
vma = get_gate_vma(mm);
|
|
||||||
if (pages) {
|
|
||||||
struct page *page;
|
|
||||||
|
|
||||||
page = vm_normal_page(vma, start, *pte);
|
|
||||||
if (!page) {
|
|
||||||
if (!(gup_flags & FOLL_DUMP) &&
|
|
||||||
is_zero_pfn(pte_pfn(*pte)))
|
|
||||||
page = pte_page(*pte);
|
|
||||||
else {
|
|
||||||
pte_unmap(pte);
|
|
||||||
goto efault;
|
|
||||||
}
|
|
||||||
}
|
|
||||||
pages[i] = page;
|
|
||||||
get_page(page);
|
|
||||||
}
|
|
||||||
pte_unmap(pte);
|
|
||||||
page_mask = 0;
|
|
||||||
goto next_page;
|
|
||||||
}
|
|
||||||
|
|
||||||
if (!vma)
|
|
||||||
goto efault;
|
|
||||||
vm_flags = vma->vm_flags;
|
|
||||||
if (vm_flags & (VM_IO | VM_PFNMAP))
|
|
||||||
goto efault;
|
|
||||||
|
|
||||||
if (gup_flags & FOLL_WRITE) {
|
|
||||||
if (!(vm_flags & VM_WRITE)) {
|
|
||||||
if (!(gup_flags & FOLL_FORCE))
|
|
||||||
goto efault;
|
|
||||||
/*
|
|
||||||
* We used to let the write,force case do COW
|
|
||||||
* in a VM_MAYWRITE VM_SHARED !VM_WRITE vma, so
|
|
||||||
* ptrace could set a breakpoint in a read-only
|
|
||||||
* mapping of an executable, without corrupting
|
|
||||||
* the file (yet only when that file had been
|
|
||||||
* opened for writing!). Anon pages in shared
|
|
||||||
* mappings are surprising: now just reject it.
|
|
||||||
*/
|
|
||||||
if (!is_cow_mapping(vm_flags)) {
|
|
||||||
WARN_ON_ONCE(vm_flags & VM_MAYWRITE);
|
|
||||||
goto efault;
|
|
||||||
}
|
|
||||||
}
|
|
||||||
} else {
|
|
||||||
if (!(vm_flags & VM_READ)) {
|
|
||||||
if (!(gup_flags & FOLL_FORCE))
|
|
||||||
goto efault;
|
|
||||||
/*
|
|
||||||
* Is there actually any vma we can reach here
|
|
||||||
* which does not have VM_MAYREAD set?
|
|
||||||
*/
|
|
||||||
if (!(vm_flags & VM_MAYREAD))
|
|
||||||
goto efault;
|
|
||||||
}
|
|
||||||
}
|
|
||||||
|
|
||||||
if (is_vm_hugetlb_page(vma)) {
|
|
||||||
i = follow_hugetlb_page(mm, vma, pages, vmas,
|
|
||||||
&start, &nr_pages, i, gup_flags);
|
|
||||||
continue;
|
|
||||||
}
|
|
||||||
|
|
||||||
do {
|
|
||||||
struct page *page;
|
|
||||||
unsigned int foll_flags = gup_flags;
|
|
||||||
unsigned int page_increm;
|
|
||||||
|
|
||||||
/*
|
|
||||||
* If we have a pending SIGKILL, don't keep faulting
|
|
||||||
* pages and potentially allocating memory.
|
|
||||||
*/
|
|
||||||
if (unlikely(fatal_signal_pending(current)))
|
|
||||||
return i ? i : -ERESTARTSYS;
|
|
||||||
|
|
||||||
cond_resched();
|
|
||||||
while (!(page = follow_page_mask(vma, start,
|
|
||||||
foll_flags, &page_mask))) {
|
|
||||||
int ret;
|
|
||||||
unsigned int fault_flags = 0;
|
|
||||||
|
|
||||||
/* For mlock, just skip the stack guard page. */
|
|
||||||
if (foll_flags & FOLL_MLOCK) {
|
|
||||||
if (stack_guard_page(vma, start))
|
|
||||||
goto next_page;
|
|
||||||
}
|
|
||||||
if (foll_flags & FOLL_WRITE)
|
|
||||||
fault_flags |= FAULT_FLAG_WRITE;
|
|
||||||
if (nonblocking)
|
|
||||||
fault_flags |= FAULT_FLAG_ALLOW_RETRY;
|
|
||||||
if (foll_flags & FOLL_NOWAIT)
|
|
||||||
fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
|
|
||||||
|
|
||||||
ret = handle_mm_fault(mm, vma, start,
|
|
||||||
fault_flags);
|
|
||||||
|
|
||||||
if (ret & VM_FAULT_ERROR) {
|
|
||||||
if (ret & VM_FAULT_OOM)
|
|
||||||
return i ? i : -ENOMEM;
|
|
||||||
if (ret & (VM_FAULT_HWPOISON |
|
|
||||||
VM_FAULT_HWPOISON_LARGE)) {
|
|
||||||
if (i)
|
|
||||||
return i;
|
|
||||||
else if (gup_flags & FOLL_HWPOISON)
|
|
||||||
return -EHWPOISON;
|
|
||||||
else
|
|
||||||
return -EFAULT;
|
|
||||||
}
|
|
||||||
if (ret & VM_FAULT_SIGBUS)
|
|
||||||
goto efault;
|
|
||||||
BUG();
|
|
||||||
}
|
|
||||||
|
|
||||||
if (tsk) {
|
|
||||||
if (ret & VM_FAULT_MAJOR)
|
|
||||||
tsk->maj_flt++;
|
|
||||||
else
|
|
||||||
tsk->min_flt++;
|
|
||||||
}
|
|
||||||
|
|
||||||
if (ret & VM_FAULT_RETRY) {
|
|
||||||
if (nonblocking)
|
|
||||||
*nonblocking = 0;
|
|
||||||
return i;
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* The VM_FAULT_WRITE bit tells us that
|
|
||||||
* do_wp_page has broken COW when necessary,
|
|
||||||
* even if maybe_mkwrite decided not to set
|
|
||||||
* pte_write. We can thus safely do subsequent
|
|
||||||
* page lookups as if they were reads. But only
|
|
||||||
* do so when looping for pte_write is futile:
|
|
||||||
* in some cases userspace may also be wanting
|
|
||||||
* to write to the gotten user page, which a
|
|
||||||
* read fault here might prevent (a readonly
|
|
||||||
* page might get reCOWed by userspace write).
|
|
||||||
*/
|
|
||||||
if ((ret & VM_FAULT_WRITE) &&
|
|
||||||
!(vma->vm_flags & VM_WRITE))
|
|
||||||
foll_flags &= ~FOLL_WRITE;
|
|
||||||
|
|
||||||
cond_resched();
|
|
||||||
}
|
|
||||||
if (IS_ERR(page))
|
|
||||||
return i ? i : PTR_ERR(page);
|
|
||||||
if (pages) {
|
|
||||||
pages[i] = page;
|
|
||||||
|
|
||||||
flush_anon_page(vma, page, start);
|
|
||||||
flush_dcache_page(page);
|
|
||||||
page_mask = 0;
|
|
||||||
}
|
|
||||||
next_page:
|
|
||||||
if (vmas) {
|
|
||||||
vmas[i] = vma;
|
|
||||||
page_mask = 0;
|
|
||||||
}
|
|
||||||
page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
|
|
||||||
if (page_increm > nr_pages)
|
|
||||||
page_increm = nr_pages;
|
|
||||||
i += page_increm;
|
|
||||||
start += page_increm * PAGE_SIZE;
|
|
||||||
nr_pages -= page_increm;
|
|
||||||
} while (nr_pages && start < vma->vm_end);
|
|
||||||
} while (nr_pages);
|
|
||||||
return i;
|
|
||||||
efault:
|
|
||||||
return i ? : -EFAULT;
|
|
||||||
}
|
|
||||||
EXPORT_SYMBOL(__get_user_pages);
|
|
||||||
|
|
||||||
/*
|
|
||||||
* fixup_user_fault() - manually resolve a user page fault
|
|
||||||
* @tsk: the task_struct to use for page fault accounting, or
|
|
||||||
* NULL if faults are not to be recorded.
|
|
||||||
* @mm: mm_struct of target mm
|
|
||||||
* @address: user address
|
|
||||||
* @fault_flags:flags to pass down to handle_mm_fault()
|
|
||||||
*
|
|
||||||
* This is meant to be called in the specific scenario where for locking reasons
|
|
||||||
* we try to access user memory in atomic context (within a pagefault_disable()
|
|
||||||
* section), this returns -EFAULT, and we want to resolve the user fault before
|
|
||||||
* trying again.
|
|
||||||
*
|
|
||||||
* Typically this is meant to be used by the futex code.
|
|
||||||
*
|
|
||||||
* The main difference with get_user_pages() is that this function will
|
|
||||||
* unconditionally call handle_mm_fault() which will in turn perform all the
|
|
||||||
* necessary SW fixup of the dirty and young bits in the PTE, while
|
|
||||||
* handle_mm_fault() only guarantees to update these in the struct page.
|
|
||||||
*
|
|
||||||
* This is important for some architectures where those bits also gate the
|
|
||||||
* access permission to the page because they are maintained in software. On
|
|
||||||
* such architectures, gup() will not be enough to make a subsequent access
|
|
||||||
* succeed.
|
|
||||||
*
|
|
||||||
* This should be called with the mm_sem held for read.
|
|
||||||
*/
|
|
||||||
int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
|
|
||||||
unsigned long address, unsigned int fault_flags)
|
|
||||||
{
|
|
||||||
struct vm_area_struct *vma;
|
|
||||||
vm_flags_t vm_flags;
|
|
||||||
int ret;
|
|
||||||
|
|
||||||
vma = find_extend_vma(mm, address);
|
|
||||||
if (!vma || address < vma->vm_start)
|
|
||||||
return -EFAULT;
|
|
||||||
|
|
||||||
vm_flags = (fault_flags & FAULT_FLAG_WRITE) ? VM_WRITE : VM_READ;
|
|
||||||
if (!(vm_flags & vma->vm_flags))
|
|
||||||
return -EFAULT;
|
|
||||||
|
|
||||||
ret = handle_mm_fault(mm, vma, address, fault_flags);
|
|
||||||
if (ret & VM_FAULT_ERROR) {
|
|
||||||
if (ret & VM_FAULT_OOM)
|
|
||||||
return -ENOMEM;
|
|
||||||
if (ret & (VM_FAULT_HWPOISON | VM_FAULT_HWPOISON_LARGE))
|
|
||||||
return -EHWPOISON;
|
|
||||||
if (ret & VM_FAULT_SIGBUS)
|
|
||||||
return -EFAULT;
|
|
||||||
BUG();
|
|
||||||
}
|
|
||||||
if (tsk) {
|
|
||||||
if (ret & VM_FAULT_MAJOR)
|
|
||||||
tsk->maj_flt++;
|
|
||||||
else
|
|
||||||
tsk->min_flt++;
|
|
||||||
}
|
|
||||||
return 0;
|
|
||||||
}
|
|
||||||
|
|
||||||
/*
|
|
||||||
* get_user_pages() - pin user pages in memory
|
|
||||||
* @tsk: the task_struct to use for page fault accounting, or
|
|
||||||
* NULL if faults are not to be recorded.
|
|
||||||
* @mm: mm_struct of target mm
|
|
||||||
* @start: starting user address
|
|
||||||
* @nr_pages: number of pages from start to pin
|
|
||||||
* @write: whether pages will be written to by the caller
|
|
||||||
* @force: whether to force access even when user mapping is currently
|
|
||||||
* protected (but never forces write access to shared mapping).
|
|
||||||
* @pages: array that receives pointers to the pages pinned.
|
|
||||||
* Should be at least nr_pages long. Or NULL, if caller
|
|
||||||
* only intends to ensure the pages are faulted in.
|
|
||||||
* @vmas: array of pointers to vmas corresponding to each page.
|
|
||||||
* Or NULL if the caller does not require them.
|
|
||||||
*
|
|
||||||
* Returns number of pages pinned. This may be fewer than the number
|
|
||||||
* requested. If nr_pages is 0 or negative, returns 0. If no pages
|
|
||||||
* were pinned, returns -errno. Each page returned must be released
|
|
||||||
* with a put_page() call when it is finished with. vmas will only
|
|
||||||
* remain valid while mmap_sem is held.
|
|
||||||
*
|
|
||||||
* Must be called with mmap_sem held for read or write.
|
|
||||||
*
|
|
||||||
* get_user_pages walks a process's page tables and takes a reference to
|
|
||||||
* each struct page that each user address corresponds to at a given
|
|
||||||
* instant. That is, it takes the page that would be accessed if a user
|
|
||||||
* thread accesses the given user virtual address at that instant.
|
|
||||||
*
|
|
||||||
* This does not guarantee that the page exists in the user mappings when
|
|
||||||
* get_user_pages returns, and there may even be a completely different
|
|
||||||
* page there in some cases (eg. if mmapped pagecache has been invalidated
|
|
||||||
* and subsequently re faulted). However it does guarantee that the page
|
|
||||||
* won't be freed completely. And mostly callers simply care that the page
|
|
||||||
* contains data that was valid *at some point in time*. Typically, an IO
|
|
||||||
* or similar operation cannot guarantee anything stronger anyway because
|
|
||||||
* locks can't be held over the syscall boundary.
|
|
||||||
*
|
|
||||||
* If write=0, the page must not be written to. If the page is written to,
|
|
||||||
* set_page_dirty (or set_page_dirty_lock, as appropriate) must be called
|
|
||||||
* after the page is finished with, and before put_page is called.
|
|
||||||
*
|
|
||||||
* get_user_pages is typically used for fewer-copy IO operations, to get a
|
|
||||||
* handle on the memory by some means other than accesses via the user virtual
|
|
||||||
* addresses. The pages may be submitted for DMA to devices or accessed via
|
|
||||||
* their kernel linear mapping (via the kmap APIs). Care should be taken to
|
|
||||||
* use the correct cache flushing APIs.
|
|
||||||
*
|
|
||||||
* See also get_user_pages_fast, for performance critical applications.
|
|
||||||
*/
|
|
||||||
long get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
|
|
||||||
unsigned long start, unsigned long nr_pages, int write,
|
|
||||||
int force, struct page **pages, struct vm_area_struct **vmas)
|
|
||||||
{
|
|
||||||
int flags = FOLL_TOUCH;
|
|
||||||
|
|
||||||
if (pages)
|
|
||||||
flags |= FOLL_GET;
|
|
||||||
if (write)
|
|
||||||
flags |= FOLL_WRITE;
|
|
||||||
if (force)
|
|
||||||
flags |= FOLL_FORCE;
|
|
||||||
|
|
||||||
return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas,
|
|
||||||
NULL);
|
|
||||||
}
|
|
||||||
EXPORT_SYMBOL(get_user_pages);
|
|
||||||
|
|
||||||
/**
|
|
||||||
* get_dump_page() - pin user page in memory while writing it to core dump
|
|
||||||
* @addr: user address
|
|
||||||
*
|
|
||||||
* Returns struct page pointer of user page pinned for dump,
|
|
||||||
* to be freed afterwards by page_cache_release() or put_page().
|
|
||||||
*
|
|
||||||
* Returns NULL on any kind of failure - a hole must then be inserted into
|
|
||||||
* the corefile, to preserve alignment with its headers; and also returns
|
|
||||||
* NULL wherever the ZERO_PAGE, or an anonymous pte_none, has been found -
|
|
||||||
* allowing a hole to be left in the corefile to save diskspace.
|
|
||||||
*
|
|
||||||
* Called without mmap_sem, but after all other threads have been killed.
|
|
||||||
*/
|
|
||||||
#ifdef CONFIG_ELF_CORE
|
|
||||||
struct page *get_dump_page(unsigned long addr)
|
|
||||||
{
|
|
||||||
struct vm_area_struct *vma;
|
|
||||||
struct page *page;
|
|
||||||
|
|
||||||
if (__get_user_pages(current, current->mm, addr, 1,
|
|
||||||
FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma,
|
|
||||||
NULL) < 1)
|
|
||||||
return NULL;
|
|
||||||
flush_cache_page(vma, addr, page_to_pfn(page));
|
|
||||||
return page;
|
|
||||||
}
|
|
||||||
#endif /* CONFIG_ELF_CORE */
|
|
||||||
|
|
||||||
pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
|
pte_t *__get_locked_pte(struct mm_struct *mm, unsigned long addr,
|
||||||
spinlock_t **ptl)
|
spinlock_t **ptl)
|
||||||
{
|
{
|
||||||
|
|
|
||||||
Loading…
Reference in a new issue