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#ifdef CONFIG_SWAP
  74        if (shmem_mapping(mapping)) {
  75                page = find_get_entry(mapping, pgoff);
  76                /*
  77                 * shmem/tmpfs may return swap: account for swapcache
  78                 * page too.
  79                 */
  80                if (radix_tree_exceptional_entry(page)) {
  81                        swp_entry_t swp = radix_to_swp_entry(page);
  82                        page = find_get_page(swap_address_space(swp), swp.val);
  83                }
  84        } else
  85                page = find_get_page(mapping, pgoff);
  86#else
  87        page = find_get_page(mapping, pgoff);
  88#endif
  89        if (page) {
  90                present = PageUptodate(page);
  91                page_cache_release(page);
  92        }
  93
  94        return present;
  95}
  96
  97static void mincore_unmapped_range(struct vm_area_struct *vma,
  98                                unsigned long addr, unsigned long end,
  99                                unsigned char *vec)
 100{
 101        unsigned long nr = (end - addr) >> PAGE_SHIFT;
 102        int i;
 103
 104        if (vma->vm_file) {
 105                pgoff_t pgoff;
 106
 107                pgoff = linear_page_index(vma, addr);
 108                for (i = 0; i < nr; i++, pgoff++)
 109                        vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff);
 110        } else {
 111                for (i = 0; i < nr; i++)
 112                        vec[i] = 0;
 113        }
 114}
 115
 116static void mincore_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
 117                        unsigned long addr, unsigned long end,
 118                        unsigned char *vec)
 119{
 120        unsigned long next;
 121        spinlock_t *ptl;
 122        pte_t *ptep;
 123
 124        ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
 125        do {
 126                pte_t pte = *ptep;
 127                pgoff_t pgoff;
 128
 129                next = addr + PAGE_SIZE;
 130                if (pte_none(pte))
 131                        mincore_unmapped_range(vma, addr, next, vec);
 132                else if (pte_present(pte))
 133                        *vec = 1;
 134                else if (pte_file(pte)) {
 135                        pgoff = pte_to_pgoff(pte);
 136                        *vec = 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);
 139
 140                        if (is_migration_entry(entry)) {
 141                                /* migration entries are always uptodate */
 142                                *vec = 1;
 143                        } else {
 144#ifdef CONFIG_SWAP
 145                                pgoff = entry.val;
 146                                *vec = mincore_page(swap_address_space(entry),
 147                                        pgoff);
 148#else
 149                                WARN_ON(1);
 150                                *vec = 1;
 151#endif
 152                        }
 153                }
 154                vec++;
 155        } while (ptep++, addr = next, addr != end);
 156        pte_unmap_unlock(ptep - 1, ptl);
 157}
 158
 159static void mincore_pmd_range(struct vm_area_struct *vma, pud_t *pud,
 160                        unsigned long addr, unsigned long end,
 161                        unsigned char *vec)
 162{
 163        unsigned long next;
 164        pmd_t *pmd;
 165
 166        pmd = pmd_offset(pud, addr);
 167        do {
 168                next = pmd_addr_end(addr, end);
 169                if (pmd_trans_huge(*pmd)) {
 170                        if (mincore_huge_pmd(vma, pmd, addr, next, vec)) {
 171                                vec += (next - addr) >> PAGE_SHIFT;
 172                                continue;
 173                        }
 174                        /* fall through */
 175                }
 176                if (pmd_none_or_trans_huge_or_clear_bad(pmd))
 177                        mincore_unmapped_range(vma, addr, next, vec);
 178                else
 179                        mincore_pte_range(vma, pmd, addr, next, vec);
 180                vec += (next - addr) >> PAGE_SHIFT;
 181        } while (pmd++, addr = next, addr != end);
 182}
 183
 184static void mincore_pud_range(struct vm_area_struct *vma, pgd_t *pgd,
 185                        unsigned long addr, unsigned long end,
 186                        unsigned char *vec)
 187{
 188        unsigned long next;
 189        pud_t *pud;
 190
 191        pud = pud_offset(pgd, addr);
 192        do {
 193                next = pud_addr_end(addr, end);
 194                if (pud_none_or_clear_bad(pud))
 195                        mincore_unmapped_range(vma, addr, next, vec);
 196                else
 197                        mincore_pmd_range(vma, pud, addr, next, vec);
 198                vec += (next - addr) >> PAGE_SHIFT;
 199        } while (pud++, addr = next, addr != end);
 200}
 201
 202static void mincore_page_range(struct vm_area_struct *vma,
 203                        unsigned long addr, unsigned long end,
 204                        unsigned char *vec)
 205{
 206        unsigned long next;
 207        pgd_t *pgd;
 208
 209        pgd = pgd_offset(vma->vm_mm, addr);
 210        do {
 211                next = pgd_addr_end(addr, end);
 212                if (pgd_none_or_clear_bad(pgd))
 213                        mincore_unmapped_range(vma, addr, next, vec);
 214                else
 215                        mincore_pud_range(vma, pgd, addr, next, vec);
 216                vec += (next - addr) >> PAGE_SHIFT;
 217        } while (pgd++, addr = next, addr != end);
 218}
 219
 220/*
 221 * Do a chunk of "sys_mincore()". We've already checked
 222 * all the arguments, we hold the mmap semaphore: we should
 223 * just return the amount of info we're asked for.
 224 */
 225static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec)
 226{
 227        struct vm_area_struct *vma;
 228        unsigned long end;
 229
 230        vma = find_vma(current->mm, addr);
 231        if (!vma || addr < vma->vm_start)
 232                return -ENOMEM;
 233
 234        end = min(vma->vm_end, addr + (pages << PAGE_SHIFT));
 235
 236        if (is_vm_hugetlb_page(vma))
 237                mincore_hugetlb_page_range(vma, addr, end, vec);
 238        else
 239                mincore_page_range(vma, addr, end, vec);
 240
 241        return (end - addr) >> PAGE_SHIFT;
 242}
 243
 244/*
 245 * The mincore(2) system call.
 246 *
 247 * mincore() returns the memory residency status of the pages in the
 248 * current process's address space specified by [addr, addr + len).
 249 * The status is returned in a vector of bytes.  The least significant
 250 * bit of each byte is 1 if the referenced page is in memory, otherwise
 251 * it is zero.
 252 *
 253 * Because the status of a page can change after mincore() checks it
 254 * but before it returns to the application, the returned vector may
 255 * contain stale information.  Only locked pages are guaranteed to
 256 * remain in memory.
 257 *
 258 * return values:
 259 *  zero    - success
 260 *  -EFAULT - vec points to an illegal address
 261 *  -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE
 262 *  -ENOMEM - Addresses in the range [addr, addr + len] are
 263 *              invalid for the address space of this process, or
 264 *              specify one or more pages which are not currently
 265 *              mapped
 266 *  -EAGAIN - A kernel resource was temporarily unavailable.
 267 */
 268SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
 269                unsigned char __user *, vec)
 270{
 271        long retval;
 272        unsigned long pages;
 273        unsigned char *tmp;
 274
 275        /* Check the start address: needs to be page-aligned.. */
 276        if (start & ~PAGE_CACHE_MASK)
 277                return -EINVAL;
 278
 279        /* ..and we need to be passed a valid user-space range */
 280        if (!access_ok(VERIFY_READ, (void __user *) start, len))
 281                return -ENOMEM;
 282
 283        /* This also avoids any overflows on PAGE_CACHE_ALIGN */
 284        pages = len >> PAGE_SHIFT;
 285        pages += (len & ~PAGE_MASK) != 0;
 286
 287        if (!access_ok(VERIFY_WRITE, vec, pages))
 288                return -EFAULT;
 289
 290        tmp = (void *) __get_free_page(GFP_USER);
 291        if (!tmp)
 292                return -EAGAIN;
 293
 294        retval = 0;
 295        while (pages) {
 296                /*
 297                 * Do at most PAGE_SIZE entries per iteration, due to
 298                 * the temporary buffer size.
 299                 */
 300                down_read(&current->mm->mmap_sem);
 301                retval = do_mincore(start, min(pages, PAGE_SIZE), tmp);
 302                up_read(&current->mm->mmap_sem);
 303
 304                if (retval <= 0)
 305                        break;
 306                if (copy_to_user(vec, tmp, retval)) {
 307                        retval = -EFAULT;
 308                        break;
 309                }
 310                pages -= retval;
 311                vec += retval;
 312                start += retval << PAGE_SHIFT;
 313                retval = 0;
 314        }
 315        free_page((unsigned long) tmp);
 316        return retval;
 317}
 318