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