LXR linux/mm/mincore.c

   1/*
   2 *      linux/mm/mincore.c
   3 *
   4 * Copyright (C) 1994-2006  Linus Torvalds
   5 */
   6
   7/*
   8 * The mincore() system call.
   9 */
  10#include <linux/pagemap.h>
  11#include <linux/gfp.h>
  12#include <linux/mm.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>
  18
  19#include <asm/uaccess.h>
  20#include <asm/pgtable.h>
  21
  22static void mincore_hugetlb_page_range(struct vm_area_struct *vma,
  23                                unsigned long addr, unsigned long end,
  24                                unsigned char *vec)
  25{
  26#ifdef CONFIG_HUGETLB_PAGE
  27        struct hstate *h;
  28
  29        h = hstate_vma(vma);
  30        while (1) {
  31                unsigned char present;
  32                pte_t *ptep;
  33                /*
  34                 * Huge pages are always in RAM for now, but
  35                 * theoretically it needs to be checked.
  36                 */
  37                ptep = huge_pte_offset(current->mm,
  38                                       addr & huge_page_mask(h));
  39                present = ptep && !huge_pte_none(huge_ptep_get(ptep));
  40                while (1) {
  41                        *vec = present;
  42                        vec++;
  43                        addr += PAGE_SIZE;
  44                        if (addr == end)
  45                                return;
  46                        /* check hugepage border */
  47                        if (!(addr & ~huge_page_mask(h)))
  48                                break;
  49                }
  50        }
  51#else
  52        BUG();
  53#endif
  54}
  55
  56/*
  57 * Later we can get more picky about what "in core" means precisely.
  58 * For now, simply check to see if the page is in the page cache,
  59 * and is up to date; i.e. that no page-in operation would be required
  60 * at this time if an application were to map and access this page.
  61 */
  62static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
  63{
  64        unsigned char present = 0;
  65        struct page *page;
  66
  67        /*
  68         * When tmpfs swaps out a page from a file, any process mapping that
  69         * file will not get a swp_entry_t in its pte, but rather it is like
  70         * any other file mapping (ie. marked !present and faulted in with
  71         * tmpfs's .fault). So swapped out tmpfs mappings are tested here.
  72         *
  73         * However when tmpfs moves the page from pagecache and into swapcache,
  74         * it is still in core, but the find_get_page below won't find it.
  75         * No big deal, but make a note of it.
  76         */
  77        page = find_get_page(mapping, pgoff);
  78        if (page) {
  79                present = PageUptodate(page);
  80                page_cache_release(page);
  81        }
  82
  83        return present;
  84}
  85
  86static void mincore_unmapped_range(struct vm_area_struct *vma,
  87                                unsigned long addr, unsigned long end,
  88                                unsigned char *vec)
  89{
  90        unsigned long nr = (end - addr) >> PAGE_SHIFT;
  91        int i;
  92
  93        if (vma->vm_file) {
  94                pgoff_t pgoff;
  95
  96                pgoff = linear_page_index(vma, addr);
  97                for (i = 0; i < nr; i++, pgoff++)
  98                        vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
  99        } else {
 100                for (i = 0; i < nr; i++)
 101                        vec[i] = 0;
 102        }
 103}
 104
 105static void mincore_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 106                        unsigned long addr, unsigned long end,
 107                        unsigned char *vec)
 108{
 109        unsigned long next;
 110        spinlock_t *ptl;
 111        pte_t *ptep;
 112
 113        ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 114        do {
 115                pte_t pte = *ptep;
 116                pgoff_t pgoff;
 117
 118                next = addr + PAGE_SIZE;
 119                if (pte_none(pte))
 120                        mincore_unmapped_range(vma, addr, next, vec);
 121                else if (pte_present(pte))
 122                        *vec = 1;
 123                else if (pte_file(pte)) {
 124                        pgoff = pte_to_pgoff(pte);
 125                        *vec = mincore_page(vma->vm_file->f_mapping, pgoff);
 126                } else { /* pte is a swap entry */
 127                        swp_entry_t entry = pte_to_swp_entry(pte);
 128
 129                        if (is_migration_entry(entry)) {
 130                                /* migration entries are always uptodate */
 131                                *vec = 1;
 132                        } else {
 133#ifdef CONFIG_SWAP
 134                                pgoff = entry.val;
 135                                *vec = mincore_page(&swapper_space, pgoff);
 136#else
 137                                WARN_ON(1);
 138                                *vec = 1;
 139#endif
 140                        }
 141                }
 142                vec++;
 143        } while (ptep++, addr = next, addr != end);
 144        pte_unmap_unlock(ptep - 1, ptl);
 145}
 146
 147static void mincore_pmd_range(struct vm_area_struct *vma, pud_t *pud,
 148                        unsigned long addr, unsigned long end,
 149                        unsigned char *vec)
 150{
 151        unsigned long next;
 152        pmd_t *pmd;
 153
 154        pmd = pmd_offset(pud, addr);
 155        do {
 156                next = pmd_addr_end(addr, end);
 157                if (pmd_trans_huge(*pmd)) {
 158                        if (mincore_huge_pmd(vma, pmd, addr, next, vec)) {
 159                                vec += (next - addr) >> PAGE_SHIFT;
 160                                continue;
 161                        }
 162                        /* fall through */
 163                }
 164                if (pmd_none_or_clear_bad(pmd))
 165                        mincore_unmapped_range(vma, addr, next, vec);
 166                else
 167                        mincore_pte_range(vma, pmd, addr, next, vec);
 168                vec += (next - addr) >> PAGE_SHIFT;
 169        } while (pmd++, addr = next, addr != end);
 170}
 171
 172static void mincore_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
 173                        unsigned long addr, unsigned long end,
 174                        unsigned char *vec)
 175{
 176        unsigned long next;
 177        pud_t *pud;
 178
 179        pud = pud_offset(pgd, addr);
 180        do {
 181                next = pud_addr_end(addr, end);
 182                if (pud_none_or_clear_bad(pud))
 183                        mincore_unmapped_range(vma, addr, next, vec);
 184                else
 185                        mincore_pmd_range(vma, pud, addr, next, vec);
 186                vec += (next - addr) >> PAGE_SHIFT;
 187        } while (pud++, addr = next, addr != end);
 188}
 189
 190static void mincore_page_range(struct vm_area_struct *vma,
 191                        unsigned long addr, unsigned long end,
 192                        unsigned char *vec)
 193{
 194        unsigned long next;
 195        pgd_t *pgd;
 196
 197        pgd = pgd_offset(vma->vm_mm, addr);
 198        do {
 199                next = pgd_addr_end(addr, end);
 200                if (pgd_none_or_clear_bad(pgd))
 201                        mincore_unmapped_range(vma, addr, next, vec);
 202                else
 203                        mincore_pud_range(vma, pgd, addr, next, vec);
 204                vec += (next - addr) >> PAGE_SHIFT;
 205        } while (pgd++, addr = next, addr != end);
 206}
 207
 208/*
 209 * Do a chunk of "sys_mincore()". We've already checked
 210 * all the arguments, we hold the mmap semaphore: we should
 211 * just return the amount of info we're asked for.
 212 */
 213static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
 214{
 215        struct vm_area_struct *vma;
 216        unsigned long end;
 217
 218        vma = find_vma(current->mm, addr);
 219        if (!vma || addr < vma->vm_start)
 220                return -ENOMEM;
 221
 222        end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
 223
 224        if (is_vm_hugetlb_page(vma)) {
 225                mincore_hugetlb_page_range(vma, addr, end, vec);
 226                return (end - addr) >> PAGE_SHIFT;
 227        }
 228
 229        end = pmd_addr_end(addr, end);
 230
 231        if (is_vm_hugetlb_page(vma))
 232                mincore_hugetlb_page_range(vma, addr, end, vec);
 233        else
 234                mincore_page_range(vma, addr, end, vec);
 235
 236        return (end - addr) >> PAGE_SHIFT;
 237}
 238
 239/*
 240 * The mincore(2) system call.
 241 *
 242 * mincore() returns the memory residency status of the pages in the
 243 * current process's address space specified by [addr, addr + len).
 244 * The status is returned in a vector of bytes.  The least significant
 245 * bit of each byte is 1 if the referenced page is in memory, otherwise
 246 * it is zero.
 247 *
 248 * Because the status of a page can change after mincore() checks it
 249 * but before it returns to the application, the returned vector may
 250 * contain stale information.  Only locked pages are guaranteed to
 251 * remain in memory.
 252 *
 253 * return values:
 254 *  zero    - success
 255 *  -EFAULT - vec points to an illegal address
 256 *  -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
 257 *  -ENOMEM - Addresses in the range [addr, addr + len] are
 258 *              invalid for the address space of this process, or
 259 *              specify one or more pages which are not currently
 260 *              mapped
 261 *  -EAGAIN - A kernel resource was temporarily unavailable.
 262 */
 263SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
 264                unsigned char __user *, vec)
 265{
 266        long retval;
 267        unsigned long pages;
 268        unsigned char *tmp;
 269
 270        /* Check the start address: needs to be page-aligned.. */
 271        if (start & ~PAGE_CACHE_MASK)
 272                return -EINVAL;
 273
 274        /* ..and we need to be passed a valid user-space range */
 275        if (!access_ok(VERIFY_READ, (void __user *) start, len))
 276                return -ENOMEM;
 277
 278        /* This also avoids any overflows on PAGE_CACHE_ALIGN */
 279        pages = len >> PAGE_SHIFT;
 280        pages += (len & ~PAGE_MASK) != 0;
 281
 282        if (!access_ok(VERIFY_WRITE, vec, pages))
 283                return -EFAULT;
 284
 285        tmp = (void *) __get_free_page(GFP_USER);
 286        if (!tmp)
 287                return -EAGAIN;
 288
 289        retval = 0;
 290        while (pages) {
 291                /*
 292                 * Do at most PAGE_SIZE entries per iteration, due to
 293                 * the temporary buffer size.
 294                 */
 295                down_read(&current->mm->mmap_sem);
 296                retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
 297                up_read(&current->mm->mmap_sem);
 298
 299                if (retval <= 0)
 300                        break;
 301                if (copy_to_user(vec, tmp, retval)) {
 302                        retval = -EFAULT;
 303                        break;
 304                }
 305                pages -= retval;
 306                vec += retval;
 307                start += retval << PAGE_SHIFT;
 308                retval = 0;
 309        }
 310        free_page((unsigned long) tmp);
 311        return retval;
 312}
 313