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/shmem_fs.h> 18 #include <linux/hugetlb.h> 19 20 #include <linux/uaccess.h> 21 #include <asm/pgtable.h> 22 23 static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, 24 unsigned long end, struct mm_walk *walk) 25 { 26 #ifdef CONFIG_HUGETLB_PAGE 27 unsigned char present; 28 unsigned char *vec = walk->private; 29 30 /* 31 * Hugepages under user process are always in RAM and never 32 * swapped out, but theoretically it needs to be checked. 33 */ 34 present = pte && !huge_pte_none(huge_ptep_get(pte)); 35 for (; addr != end; vec++, addr += PAGE_SIZE) 36 *vec = present; 37 walk->private = vec; 38 #else 39 BUG(); 40 #endif 41 return 0; 42 } 43 44 /* 45 * Later we can get more picky about what "in core" means precisely. 46 * For now, simply check to see if the page is in the page cache, 47 * and is up to date; i.e. that no page-in operation would be required 48 * at this time if an application were to map and access this page. 49 */ 50 static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) 51 { 52 unsigned char present = 0; 53 struct page *page; 54 55 /* 56 * When tmpfs swaps out a page from a file, any process mapping that 57 * file will not get a swp_entry_t in its pte, but rather it is like 58 * any other file mapping (ie. marked !present and faulted in with 59 * tmpfs's .fault). So swapped out tmpfs mappings are tested here. 60 */ 61 #ifdef CONFIG_SWAP 62 if (shmem_mapping(mapping)) { 63 page = find_get_entry(mapping, pgoff); 64 /* 65 * shmem/tmpfs may return swap: account for swapcache 66 * page too. 67 */ 68 if (radix_tree_exceptional_entry(page)) { 69 swp_entry_t swp = radix_to_swp_entry(page); 70 page = find_get_page(swap_address_space(swp), 71 swp_offset(swp)); 72 } 73 } else 74 page = find_get_page(mapping, pgoff); 75 #else 76 page = find_get_page(mapping, pgoff); 77 #endif 78 if (page) { 79 present = PageUptodate(page); 80 put_page(page); 81 } 82 83 return present; 84 } 85 86 static int __mincore_unmapped_range(unsigned long addr, unsigned long end, 87 struct vm_area_struct *vma, unsigned char *vec) 88 { 89 unsigned long nr = (end - addr) >> PAGE_SHIFT; 90 int i; 91 92 if (vma->vm_file) { 93 pgoff_t pgoff; 94 95 pgoff = linear_page_index(vma, addr); 96 for (i = 0; i < nr; i++, pgoff++) 97 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 98 } else { 99 for (i = 0; i < nr; i++) 100 vec[i] = 0; 101 } 102 return nr; 103 } 104 105 static int mincore_unmapped_range(unsigned long addr, unsigned long end, 106 struct mm_walk *walk) 107 { 108 walk->private += __mincore_unmapped_range(addr, end, 109 walk->vma, walk->private); 110 return 0; 111 } 112 113 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 114 struct mm_walk *walk) 115 { 116 spinlock_t *ptl; 117 struct vm_area_struct *vma = walk->vma; 118 pte_t *ptep; 119 unsigned char *vec = walk->private; 120 int nr = (end - addr) >> PAGE_SHIFT; 121 122 ptl = pmd_trans_huge_lock(pmd, vma); 123 if (ptl) { 124 memset(vec, 1, nr); 125 spin_unlock(ptl); 126 goto out; 127 } 128 129 if (pmd_trans_unstable(pmd)) { 130 __mincore_unmapped_range(addr, end, vma, vec); 131 goto out; 132 } 133 134 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 135 for (; addr != end; ptep++, addr += PAGE_SIZE) { 136 pte_t pte = *ptep; 137 138 if (pte_none(pte)) 139 __mincore_unmapped_range(addr, addr + PAGE_SIZE, 140 vma, vec); 141 else if (pte_present(pte)) 142 *vec = 1; 143 else { /* pte is a swap entry */ 144 swp_entry_t entry = pte_to_swp_entry(pte); 145 146 if (non_swap_entry(entry)) { 147 /* 148 * migration or hwpoison entries are always 149 * uptodate 150 */ 151 *vec = 1; 152 } else { 153 #ifdef CONFIG_SWAP 154 *vec = mincore_page(swap_address_space(entry), 155 swp_offset(entry)); 156 #else 157 WARN_ON(1); 158 *vec = 1; 159 #endif 160 } 161 } 162 vec++; 163 } 164 pte_unmap_unlock(ptep - 1, ptl); 165 out: 166 walk->private += nr; 167 cond_resched(); 168 return 0; 169 } 170 171 /* 172 * Do a chunk of "sys_mincore()". We've already checked 173 * all the arguments, we hold the mmap semaphore: we should 174 * just return the amount of info we're asked for. 175 */ 176 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 177 { 178 struct vm_area_struct *vma; 179 unsigned long end; 180 int err; 181 struct mm_walk mincore_walk = { 182 .pmd_entry = mincore_pte_range, 183 .pte_hole = mincore_unmapped_range, 184 .hugetlb_entry = mincore_hugetlb, 185 .private = vec, 186 }; 187 188 vma = find_vma(current->mm, addr); 189 if (!vma || addr < vma->vm_start) 190 return -ENOMEM; 191 mincore_walk.mm = vma->vm_mm; 192 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 193 err = walk_page_range(addr, end, &mincore_walk); 194 if (err < 0) 195 return err; 196 return (end - addr) >> PAGE_SHIFT; 197 } 198 199 /* 200 * The mincore(2) system call. 201 * 202 * mincore() returns the memory residency status of the pages in the 203 * current process's address space specified by [addr, addr + len). 204 * The status is returned in a vector of bytes. The least significant 205 * bit of each byte is 1 if the referenced page is in memory, otherwise 206 * it is zero. 207 * 208 * Because the status of a page can change after mincore() checks it 209 * but before it returns to the application, the returned vector may 210 * contain stale information. Only locked pages are guaranteed to 211 * remain in memory. 212 * 213 * return values: 214 * zero - success 215 * -EFAULT - vec points to an illegal address 216 * -EINVAL - addr is not a multiple of PAGE_SIZE 217 * -ENOMEM - Addresses in the range [addr, addr + len] are 218 * invalid for the address space of this process, or 219 * specify one or more pages which are not currently 220 * mapped 221 * -EAGAIN - A kernel resource was temporarily unavailable. 222 */ 223 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 224 unsigned char __user *, vec) 225 { 226 long retval; 227 unsigned long pages; 228 unsigned char *tmp; 229 230 /* Check the start address: needs to be page-aligned.. */ 231 if (start & ~PAGE_MASK) 232 return -EINVAL; 233 234 /* ..and we need to be passed a valid user-space range */ 235 if (!access_ok(VERIFY_READ, (void __user *) start, len)) 236 return -ENOMEM; 237 238 /* This also avoids any overflows on PAGE_ALIGN */ 239 pages = len >> PAGE_SHIFT; 240 pages += (offset_in_page(len)) != 0; 241 242 if (!access_ok(VERIFY_WRITE, vec, pages)) 243 return -EFAULT; 244 245 tmp = (void *) __get_free_page(GFP_USER); 246 if (!tmp) 247 return -EAGAIN; 248 249 retval = 0; 250 while (pages) { 251 /* 252 * Do at most PAGE_SIZE entries per iteration, due to 253 * the temporary buffer size. 254 */ 255 down_read(¤t->mm->mmap_sem); 256 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 257 up_read(¤t->mm->mmap_sem); 258 259 if (retval <= 0) 260 break; 261 if (copy_to_user(vec, tmp, retval)) { 262 retval = -EFAULT; 263 break; 264 } 265 pages -= retval; 266 vec += retval; 267 start += retval << PAGE_SHIFT; 268 retval = 0; 269 } 270 free_page((unsigned long) tmp); 271 return retval; 272 } 273