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 18 #include <asm/uaccess.h> 19 #include <asm/pgtable.h> 20 21 /* 22 * Later we can get more picky about what "in core" means precisely. 23 * For now, simply check to see if the page is in the page cache, 24 * and is up to date; i.e. that no page-in operation would be required 25 * at this time if an application were to map and access this page. 26 */ 27 static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) 28 { 29 unsigned char present = 0; 30 struct page *page; 31 32 /* 33 * When tmpfs swaps out a page from a file, any process mapping that 34 * file will not get a swp_entry_t in its pte, but rather it is like 35 * any other file mapping (ie. marked !present and faulted in with 36 * tmpfs's .nopage). So swapped out tmpfs mappings are tested here. 37 * 38 * However when tmpfs moves the page from pagecache and into swapcache, 39 * it is still in core, but the find_get_page below won't find it. 40 * No big deal, but make a note of it. 41 */ 42 page = find_get_page(mapping, pgoff); 43 if (page) { 44 present = PageUptodate(page); 45 page_cache_release(page); 46 } 47 48 return present; 49 } 50 51 /* 52 * Do a chunk of "sys_mincore()". We've already checked 53 * all the arguments, we hold the mmap semaphore: we should 54 * just return the amount of info we're asked for. 55 */ 56 static long do_mincore(unsigned long addr, unsigned char *vec, unsigned long pages) 57 { 58 pgd_t *pgd; 59 pud_t *pud; 60 pmd_t *pmd; 61 pte_t *ptep; 62 spinlock_t *ptl; 63 unsigned long nr; 64 int i; 65 pgoff_t pgoff; 66 struct vm_area_struct *vma = find_vma(current->mm, addr); 67 68 /* 69 * find_vma() didn't find anything above us, or we're 70 * in an unmapped hole in the address space: ENOMEM. 71 */ 72 if (!vma || addr < vma->vm_start) 73 return -ENOMEM; 74 75 /* 76 * Calculate how many pages there are left in the last level of the 77 * PTE array for our address. 78 */ 79 nr = PTRS_PER_PTE - ((addr >> PAGE_SHIFT) & (PTRS_PER_PTE-1)); 80 if (nr > pages) 81 nr = pages; 82 83 pgd = pgd_offset(vma->vm_mm, addr); 84 if (pgd_none_or_clear_bad(pgd)) 85 goto none_mapped; 86 pud = pud_offset(pgd, addr); 87 if (pud_none_or_clear_bad(pud)) 88 goto none_mapped; 89 pmd = pmd_offset(pud, addr); 90 if (pmd_none_or_clear_bad(pmd)) 91 goto none_mapped; 92 93 ptep = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); 94 for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) { 95 unsigned char present; 96 pte_t pte = *ptep; 97 98 if (pte_present(pte)) { 99 present = 1; 100 101 } else if (pte_none(pte)) { 102 if (vma->vm_file) { 103 pgoff = linear_page_index(vma, addr); 104 present = mincore_page(vma->vm_file->f_mapping, 105 pgoff); 106 } else 107 present = 0; 108 109 } else if (pte_file(pte)) { 110 pgoff = pte_to_pgoff(pte); 111 present = mincore_page(vma->vm_file->f_mapping, pgoff); 112 113 } else { /* pte is a swap entry */ 114 swp_entry_t entry = pte_to_swp_entry(pte); 115 if (is_migration_entry(entry)) { 116 /* migration entries are always uptodate */ 117 present = 1; 118 } else { 119 pgoff = entry.val; 120 present = mincore_page(&swapper_space, pgoff); 121 } 122 } 123 } 124 pte_unmap_unlock(ptep-1, ptl); 125 126 return nr; 127 128 none_mapped: 129 if (vma->vm_file) { 130 pgoff = linear_page_index(vma, addr); 131 for (i = 0; i < nr; i++, pgoff++) 132 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 133 } 134 135 return nr; 136 } 137 138 /* 139 * The mincore(2) system call. 140 * 141 * mincore() returns the memory residency status of the pages in the 142 * current process's address space specified by [addr, addr + len). 143 * The status is returned in a vector of bytes. The least significant 144 * bit of each byte is 1 if the referenced page is in memory, otherwise 145 * it is zero. 146 * 147 * Because the status of a page can change after mincore() checks it 148 * but before it returns to the application, the returned vector may 149 * contain stale information. Only locked pages are guaranteed to 150 * remain in memory. 151 * 152 * return values: 153 * zero - success 154 * -EFAULT - vec points to an illegal address 155 * -EINVAL - addr is not a multiple of PAGE_CACHE_SIZE 156 * -ENOMEM - Addresses in the range [addr, addr + len] are 157 * invalid for the address space of this process, or 158 * specify one or more pages which are not currently 159 * mapped 160 * -EAGAIN - A kernel resource was temporarily unavailable. 161 */ 162 asmlinkage long sys_mincore(unsigned long start, size_t len, 163 unsigned char __user * vec) 164 { 165 long retval; 166 unsigned long pages; 167 unsigned char *tmp; 168 169 /* Check the start address: needs to be page-aligned.. */ 170 if (start & ~PAGE_CACHE_MASK) 171 return -EINVAL; 172 173 /* ..and we need to be passed a valid user-space range */ 174 if (!access_ok(VERIFY_READ, (void __user *) start, len)) 175 return -ENOMEM; 176 177 /* This also avoids any overflows on PAGE_CACHE_ALIGN */ 178 pages = len >> PAGE_SHIFT; 179 pages += (len & ~PAGE_MASK) != 0; 180 181 if (!access_ok(VERIFY_WRITE, vec, pages)) 182 return -EFAULT; 183 184 tmp = (void *) __get_free_page(GFP_USER); 185 if (!tmp) 186 return -EAGAIN; 187 188 retval = 0; 189 while (pages) { 190 /* 191 * Do at most PAGE_SIZE entries per iteration, due to 192 * the temporary buffer size. 193 */ 194 down_read(¤t->mm->mmap_sem); 195 retval = do_mincore(start, tmp, min(pages, PAGE_SIZE)); 196 up_read(¤t->mm->mmap_sem); 197 198 if (retval <= 0) 199 break; 200 if (copy_to_user(vec, tmp, retval)) { 201 retval = -EFAULT; 202 break; 203 } 204 pages -= retval; 205 vec += retval; 206 start += retval << PAGE_SHIFT; 207 retval = 0; 208 } 209 free_page((unsigned long) tmp); 210 return retval; 211 } 212