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/slab.h> 11 #include <linux/pagemap.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 22 /* 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. 27 */ 28 static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) 29 { 30 unsigned char present = 0; 31 struct page *page; 32 33 /* 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. 38 * 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. 42 */ 43 page = find_get_page(mapping, pgoff); 44 if (page) { 45 present = PageUptodate(page); 46 page_cache_release(page); 47 } 48 49 return present; 50 } 51 52 /* 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. 56 */ 57 static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pages) 58 { 59 pgd_t *pgd; 60 pud_t *pud; 61 pmd_t *pmd; 62 pte_t *ptep; 63 spinlock_t *ptl; 64 unsigned long nr; 65 int i; 66 pgoff_t pgoff; 67 struct vm_area_struct *vma = find_vma(current->mm, addr); 68 69 /* 70 * find_vma() didn't find anything above us, or we're 71 * in an unmapped hole in the address space: ENOMEM. 72 */ 73 if (!vma || addr < vma->vm_start) 74 return -ENOMEM; 75 76 #ifdef CONFIG_HUGETLB_PAGE 77 if (is_vm_hugetlb_page(vma)) { 78 struct hstate *h; 79 unsigned long nr_huge; 80 unsigned char present; 81 82 i = 0; 83 nr = min(pages, (vma->vm_end - addr) >> PAGE_SHIFT); 84 h = hstate_vma(vma); 85 nr_huge = ((addr + pages * PAGE_SIZE - 1) >> huge_page_shift(h)) 86 - (addr >> huge_page_shift(h)) + 1; 87 nr_huge = min(nr_huge, 88 (vma->vm_end - addr) >> huge_page_shift(h)); 89 while (1) { 90 /* hugepage always in RAM for now, 91 * but generally it needs to be check */ 92 ptep = huge_pte_offset(current->mm, 93 addr & huge_page_mask(h)); 94 present = !!(ptep && 95 !huge_pte_none(huge_ptep_get(ptep))); 96 while (1) { 97 vec[i++] = present; 98 addr += PAGE_SIZE; 99 /* reach buffer limit */ 100 if (i == nr) 101 return nr; 102 /* check hugepage border */ 103 if (!((addr & ~huge_page_mask(h)) 104 >> PAGE_SHIFT)) 105 break; 106 } 107 } 108 return nr; 109 } 110 #endif 111 112 /* 113 * Calculate how many pages there are left in the last level of the 114 * PTE array for our address. 115 */ 116 nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1)); 117 118 /* 119 * Don't overrun this vma 120 */ 121 nr = min(nr, (vma->vm_end - addr) >> PAGE_SHIFT); 122 123 /* 124 * Don't return more than the caller asked for 125 */ 126 nr = min(nr, pages); 127 128 pgd = pgd_offset(vma->vm_mm, addr); 129 if (pgd_none_or_clear_bad(pgd)) 130 goto none_mapped; 131 pud = pud_offset(pgd, addr); 132 if (pud_none_or_clear_bad(pud)) 133 goto none_mapped; 134 pmd = pmd_offset(pud, addr); 135 if (pmd_none_or_clear_bad(pmd)) 136 goto none_mapped; 137 138 ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 139 for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) { 140 unsigned char present; 141 pte_t pte = *ptep; 142 143 if (pte_present(pte)) { 144 present = 1; 145 146 } else if (pte_none(pte)) { 147 if (vma->vm_file) { 148 pgoff = linear_page_index(vma, addr); 149 present = mincore_page(vma->vm_file->f_mapping, 150 pgoff); 151 } else 152 present = 0; 153 154 } else if (pte_file(pte)) { 155 pgoff = pte_to_pgoff(pte); 156 present = mincore_page(vma->vm_file->f_mapping, pgoff); 157 158 } else { /* pte is a swap entry */ 159 swp_entry_t entry = pte_to_swp_entry(pte); 160 if (is_migration_entry(entry)) { 161 /* migration entries are always uptodate */ 162 present = 1; 163 } else { 164 #ifdef CONFIG_SWAP 165 pgoff = entry.val; 166 present = mincore_page(&swapper_space, pgoff); 167 #else 168 WARN_ON(1); 169 present = 1; 170 #endif 171 } 172 } 173 174 vec[i] = present; 175 } 176 pte_unmap_unlock(ptep-1, ptl); 177 178 return nr; 179 180 none_mapped: 181 if (vma->vm_file) { 182 pgoff = linear_page_index(vma, addr); 183 for (i = 0; i < nr; i++, pgoff++) 184 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 185 } else { 186 for (i = 0; i < nr; i++) 187 vec[i] = 0; 188 } 189 190 return nr; 191 } 192 193 /* 194 * The mincore(2) system call. 195 * 196 * mincore() returns the memory residency status of the pages in the 197 * current process's address space specified by [addr, addr + len). 198 * The status is returned in a vector of bytes. The least significant 199 * bit of each byte is 1 if the referenced page is in memory, otherwise 200 * it is zero. 201 * 202 * Because the status of a page can change after mincore() checks it 203 * but before it returns to the application, the returned vector may 204 * contain stale information. Only locked pages are guaranteed to 205 * remain in memory. 206 * 207 * return values: 208 * zero - success 209 * -EFAULT - vec points to an illegal address 210 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE 211 * -ENOMEM - Addresses in the range [addr, addr + len] are 212 * invalid for the address space of this process, or 213 * specify one or more pages which are not currently 214 * mapped 215 * -EAGAIN - A kernel resource was temporarily unavailable. 216 */ 217 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 218 unsigned char __user *, vec) 219 { 220 long retval; 221 unsigned long pages; 222 unsigned char *tmp; 223 224 /* Check the start address: needs to be page-aligned.. */ 225 if (start & ~PAGE_CACHE_MASK) 226 return -EINVAL; 227 228 /* ..and we need to be passed a valid user-space range */ 229 if (!access_ok(VERIFY_READ, (void __user *) start, len)) 230 return -ENOMEM; 231 232 /* This also avoids any overflows on PAGE_CACHE_ALIGN */ 233 pages = len >> PAGE_SHIFT; 234 pages += (len & ~PAGE_MASK) != 0; 235 236 if (!access_ok(VERIFY_WRITE, vec, pages)) 237 return -EFAULT; 238 239 tmp = (void *) __get_free_page(GFP_USER); 240 if (!tmp) 241 return -EAGAIN; 242 243 retval = 0; 244 while (pages) { 245 /* 246 * Do at most PAGE_SIZE entries per iteration, due to 247 * the temporary buffer size. 248 */ 249 down_read(¤t->mm->mmap_sem); 250 retval = do_mincore(start, tmp, min(pages, PAGE_SIZE)); 251 up_read(¤t->mm->mmap_sem); 252 253 if (retval <= 0) 254 break; 255 if (copy_to_user(vec, tmp, retval)) { 256 retval = -EFAULT; 257 break; 258 } 259 pages -= retval; 260 vec += retval; 261 start += retval << PAGE_SHIFT; 262 retval = 0; 263 } 264 free_page((unsigned long) tmp); 265 return retval; 266 } 267