Root/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

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