282 lines
7.0 KiB
C
282 lines
7.0 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* linux/mm/mincore.c
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*
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* Copyright (C) 1994-2006 Linus Torvalds
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*/
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/*
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* The mincore() system call.
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*/
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#include <linux/pagemap.h>
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#include <linux/gfp.h>
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#include <linux/pagewalk.h>
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#include <linux/mman.h>
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#include <linux/syscalls.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/shmem_fs.h>
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#include <linux/hugetlb.h>
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#include <linux/pgtable.h>
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#include <linux/uaccess.h>
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static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr,
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unsigned long end, struct mm_walk *walk)
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{
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#ifdef CONFIG_HUGETLB_PAGE
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unsigned char present;
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unsigned char *vec = walk->private;
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/*
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* Hugepages under user process are always in RAM and never
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* swapped out, but theoretically it needs to be checked.
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*/
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present = pte && !huge_pte_none(huge_ptep_get(pte));
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for (; addr != end; vec++, addr += PAGE_SIZE)
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*vec = present;
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walk->private = vec;
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#else
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BUG();
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#endif
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return 0;
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}
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/*
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* Later we can get more picky about what "in core" means precisely.
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* For now, simply check to see if the page is in the page cache,
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* and is up to date; i.e. that no page-in operation would be required
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* at this time if an application were to map and access this page.
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*/
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static unsigned char mincore_page(struct address_space *mapping, pgoff_t index)
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{
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unsigned char present = 0;
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struct page *page;
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/*
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* When tmpfs swaps out a page from a file, any process mapping that
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* file will not get a swp_entry_t in its pte, but rather it is like
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* any other file mapping (ie. marked !present and faulted in with
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* tmpfs's .fault). So swapped out tmpfs mappings are tested here.
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*/
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page = find_get_incore_page(mapping, index);
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if (page) {
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present = PageUptodate(page);
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put_page(page);
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}
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return present;
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}
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static int __mincore_unmapped_range(unsigned long addr, unsigned long end,
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struct vm_area_struct *vma, unsigned char *vec)
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{
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unsigned long nr = (end - addr) >> PAGE_SHIFT;
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int i;
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if (vma->vm_file) {
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pgoff_t pgoff;
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pgoff = linear_page_index(vma, addr);
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for (i = 0; i < nr; i++, pgoff++)
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vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
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} else {
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for (i = 0; i < nr; i++)
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vec[i] = 0;
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}
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return nr;
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}
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static int mincore_unmapped_range(unsigned long addr, unsigned long end,
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__always_unused int depth,
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struct mm_walk *walk)
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{
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walk->private += __mincore_unmapped_range(addr, end,
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walk->vma, walk->private);
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return 0;
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}
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static int mincore_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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spinlock_t *ptl;
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struct vm_area_struct *vma = walk->vma;
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pte_t *ptep;
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unsigned char *vec = walk->private;
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int nr = (end - addr) >> PAGE_SHIFT;
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ptl = pmd_trans_huge_lock(pmd, vma);
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if (ptl) {
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memset(vec, 1, nr);
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spin_unlock(ptl);
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goto out;
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}
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if (pmd_trans_unstable(pmd)) {
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__mincore_unmapped_range(addr, end, vma, vec);
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goto out;
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}
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ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
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for (; addr != end; ptep++, addr += PAGE_SIZE) {
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pte_t pte = *ptep;
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if (pte_none(pte))
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__mincore_unmapped_range(addr, addr + PAGE_SIZE,
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vma, vec);
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else if (pte_present(pte))
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*vec = 1;
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else { /* pte is a swap entry */
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swp_entry_t entry = pte_to_swp_entry(pte);
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if (non_swap_entry(entry)) {
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/*
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* migration or hwpoison entries are always
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* uptodate
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*/
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*vec = 1;
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} else {
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#ifdef CONFIG_SWAP
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*vec = mincore_page(swap_address_space(entry),
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swp_offset(entry));
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#else
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WARN_ON(1);
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*vec = 1;
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#endif
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}
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}
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vec++;
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}
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pte_unmap_unlock(ptep - 1, ptl);
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out:
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walk->private += nr;
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cond_resched();
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return 0;
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}
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static inline bool can_do_mincore(struct vm_area_struct *vma)
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{
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if (vma_is_anonymous(vma))
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return true;
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if (!vma->vm_file)
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return false;
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/*
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* Reveal pagecache information only for non-anonymous mappings that
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* correspond to the files the calling process could (if tried) open
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* for writing; otherwise we'd be including shared non-exclusive
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* mappings, which opens a side channel.
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*/
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return inode_owner_or_capable(&init_user_ns,
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file_inode(vma->vm_file)) ||
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file_permission(vma->vm_file, MAY_WRITE) == 0;
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}
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static const struct mm_walk_ops mincore_walk_ops = {
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.pmd_entry = mincore_pte_range,
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.pte_hole = mincore_unmapped_range,
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.hugetlb_entry = mincore_hugetlb,
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};
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/*
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* Do a chunk of "sys_mincore()". We've already checked
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* all the arguments, we hold the mmap semaphore: we should
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* just return the amount of info we're asked for.
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*/
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static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
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{
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struct vm_area_struct *vma;
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unsigned long end;
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int err;
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vma = find_vma(current->mm, addr);
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if (!vma || addr < vma->vm_start)
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return -ENOMEM;
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end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
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if (!can_do_mincore(vma)) {
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unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE);
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memset(vec, 1, pages);
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return pages;
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}
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err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec);
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if (err < 0)
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return err;
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return (end - addr) >> PAGE_SHIFT;
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}
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/*
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* The mincore(2) system call.
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*
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* mincore() returns the memory residency status of the pages in the
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* current process's address space specified by [addr, addr + len).
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* The status is returned in a vector of bytes. The least significant
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* bit of each byte is 1 if the referenced page is in memory, otherwise
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* it is zero.
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*
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* Because the status of a page can change after mincore() checks it
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* but before it returns to the application, the returned vector may
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* contain stale information. Only locked pages are guaranteed to
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* remain in memory.
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*
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* return values:
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* zero - success
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* -EFAULT - vec points to an illegal address
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* -EINVAL - addr is not a multiple of PAGE_SIZE
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* -ENOMEM - Addresses in the range [addr, addr + len] are
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* invalid for the address space of this process, or
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* specify one or more pages which are not currently
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* mapped
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* -EAGAIN - A kernel resource was temporarily unavailable.
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*/
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SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
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unsigned char __user *, vec)
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{
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long retval;
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unsigned long pages;
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unsigned char *tmp;
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start = untagged_addr(start);
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/* Check the start address: needs to be page-aligned.. */
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if (start & ~PAGE_MASK)
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return -EINVAL;
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/* ..and we need to be passed a valid user-space range */
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if (!access_ok((void __user *) start, len))
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return -ENOMEM;
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/* This also avoids any overflows on PAGE_ALIGN */
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pages = len >> PAGE_SHIFT;
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pages += (offset_in_page(len)) != 0;
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if (!access_ok(vec, pages))
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return -EFAULT;
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tmp = (void *) __get_free_page(GFP_USER);
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if (!tmp)
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return -EAGAIN;
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retval = 0;
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while (pages) {
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/*
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* Do at most PAGE_SIZE entries per iteration, due to
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* the temporary buffer size.
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*/
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mmap_read_lock(current->mm);
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retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
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mmap_read_unlock(current->mm);
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if (retval <= 0)
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break;
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if (copy_to_user(vec, tmp, retval)) {
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retval = -EFAULT;
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break;
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}
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pages -= retval;
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vec += retval;
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start += retval << PAGE_SHIFT;
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retval = 0;
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}
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free_page((unsigned long) tmp);
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return retval;
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}
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