4 * Copyright (C) 1994-2006 Linus Torvalds
8 * The mincore() system call.
10 #include <linux/pagemap.h>
11 #include <linux/gfp.h>
13 #include <linux/mman.h>
14 #include <linux/syscalls.h>
15 #include <linux/swap.h>
16 #include <linux/swapops.h>
17 #include <linux/hugetlb.h>
19 #include <asm/uaccess.h>
20 #include <asm/pgtable.h>
23 * Later we can get more picky about what "in core" means precisely.
24 * For now, simply check to see if the page is in the page cache,
25 * and is up to date; i.e. that no page-in operation would be required
26 * at this time if an application were to map and access this page.
28 static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
30 unsigned char present = 0;
34 * When tmpfs swaps out a page from a file, any process mapping that
35 * file will not get a swp_entry_t in its pte, but rather it is like
36 * any other file mapping (ie. marked !present and faulted in with
37 * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
39 * However when tmpfs moves the page from pagecache and into swapcache,
40 * it is still in core, but the find_get_page below won't find it.
41 * No big deal, but make a note of it.
43 page = find_get_page(mapping, pgoff);
45 present = PageUptodate(page);
46 page_cache_release(page);
53 * Do a chunk of "sys_mincore()". We've already checked
54 * all the arguments, we hold the mmap semaphore: we should
55 * just return the amount of info we're asked for.
57 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
67 struct vm_area_struct *vma;
69 vma = find_vma(current->mm, addr);
70 if (!vma || addr < vma->vm_start)
73 nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT);
75 #ifdef CONFIG_HUGETLB_PAGE
76 if (is_vm_hugetlb_page(vma)) {
82 unsigned char present;
84 * Huge pages are always in RAM for now, but
85 * theoretically it needs to be checked.
87 ptep = huge_pte_offset(current->mm,
88 addr & huge_page_mask(h));
89 present = ptep && !huge_pte_none(huge_ptep_get(ptep));
93 /* reach buffer limit */
96 /* check hugepage border */
97 if (!(addr & ~huge_page_mask(h)))
106 * Calculate how many pages there are left in the last level of the
107 * PTE array for our address.
109 nr = min(nr, PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1)));
111 pgd = pgd_offset(vma->vm_mm, addr);
112 if (pgd_none_or_clear_bad(pgd))
114 pud = pud_offset(pgd, addr);
115 if (pud_none_or_clear_bad(pud))
117 pmd = pmd_offset(pud, addr);
118 if (pmd_none_or_clear_bad(pmd))
121 ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
122 for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) {
127 pgoff = linear_page_index(vma, addr);
128 vec[i] = mincore_page(vma->vm_file->f_mapping,
132 } else if (pte_present(pte))
134 else if (pte_file(pte)) {
135 pgoff = pte_to_pgoff(pte);
136 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
137 } else { /* pte is a swap entry */
138 swp_entry_t entry = pte_to_swp_entry(pte);
140 if (is_migration_entry(entry)) {
141 /* migration entries are always uptodate */
146 vec[i] = mincore_page(&swapper_space, pgoff);
154 pte_unmap_unlock(ptep - 1, ptl);
160 pgoff = linear_page_index(vma, addr);
161 for (i = 0; i < nr; i++, pgoff++)
162 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
164 for (i = 0; i < nr; i++)
172 * The mincore(2) system call.
174 * mincore() returns the memory residency status of the pages in the
175 * current process's address space specified by [addr, addr + len).
176 * The status is returned in a vector of bytes. The least significant
177 * bit of each byte is 1 if the referenced page is in memory, otherwise
180 * Because the status of a page can change after mincore() checks it
181 * but before it returns to the application, the returned vector may
182 * contain stale information. Only locked pages are guaranteed to
187 * -EFAULT - vec points to an illegal address
188 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
189 * -ENOMEM - Addresses in the range [addr, addr + len] are
190 * invalid for the address space of this process, or
191 * specify one or more pages which are not currently
193 * -EAGAIN - A kernel resource was temporarily unavailable.
195 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
196 unsigned char __user *, vec)
202 /* Check the start address: needs to be page-aligned.. */
203 if (start & ~PAGE_CACHE_MASK)
206 /* ..and we need to be passed a valid user-space range */
207 if (!access_ok(VERIFY_READ, (void __user *) start, len))
210 /* This also avoids any overflows on PAGE_CACHE_ALIGN */
211 pages = len >> PAGE_SHIFT;
212 pages += (len & ~PAGE_MASK) != 0;
214 if (!access_ok(VERIFY_WRITE, vec, pages))
217 tmp = (void *) __get_free_page(GFP_USER);
224 * Do at most PAGE_SIZE entries per iteration, due to
225 * the temporary buffer size.
227 down_read(¤t->mm->mmap_sem);
228 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
229 up_read(¤t->mm->mmap_sem);
233 if (copy_to_user(vec, tmp, retval)) {
239 start += retval << PAGE_SHIFT;
242 free_page((unsigned long) tmp);