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

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