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), swp.val); 70 } 71 } else 72 page = find_get_page(mapping, pgoff); 73 #else 74 page = find_get_page(mapping, pgoff); 75 #endif 76 if (page) { 77 present = PageUptodate(page); 78 put_page(page); 79 } 80 81 return present; 82 } 83 84 static int __mincore_unmapped_range(unsigned long addr, unsigned long end, 85 struct vm_area_struct *vma, unsigned char *vec) 86 { 87 unsigned long nr = (end - addr) >> PAGE_SHIFT; 88 int i; 89 90 if (vma->vm_file) { 91 pgoff_t pgoff; 92 93 pgoff = linear_page_index(vma, addr); 94 for (i = 0; i < nr; i++, pgoff++) 95 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 96 } else { 97 for (i = 0; i < nr; i++) 98 vec[i] = 0; 99 } 100 return nr; 101 } 102 103 static int mincore_unmapped_range(unsigned long addr, unsigned long end, 104 struct mm_walk *walk) 105 { 106 walk->private += __mincore_unmapped_range(addr, end, 107 walk->vma, walk->private); 108 return 0; 109 } 110 111 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 112 struct mm_walk *walk) 113 { 114 spinlock_t *ptl; 115 struct vm_area_struct *vma = walk->vma; 116 pte_t *ptep; 117 unsigned char *vec = walk->private; 118 int nr = (end - addr) >> PAGE_SHIFT; 119 120 ptl = pmd_trans_huge_lock(pmd, vma); 121 if (ptl) { 122 memset(vec, 1, nr); 123 spin_unlock(ptl); 124 goto out; 125 } 126 127 if (pmd_trans_unstable(pmd)) { 128 __mincore_unmapped_range(addr, end, vma, vec); 129 goto out; 130 } 131 132 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 133 for (; addr != end; ptep++, addr += PAGE_SIZE) { 134 pte_t pte = *ptep; 135 136 if (pte_none(pte)) 137 __mincore_unmapped_range(addr, addr + PAGE_SIZE, 138 vma, vec); 139 else if (pte_present(pte)) 140 *vec = 1; 141 else { /* pte is a swap entry */ 142 swp_entry_t entry = pte_to_swp_entry(pte); 143 144 if (non_swap_entry(entry)) { 145 /* 146 * migration or hwpoison entries are always 147 * uptodate 148 */ 149 *vec = 1; 150 } else { 151 #ifdef CONFIG_SWAP 152 *vec = mincore_page(swap_address_space(entry), 153 entry.val); 154 #else 155 WARN_ON(1); 156 *vec = 1; 157 #endif 158 } 159 } 160 vec++; 161 } 162 pte_unmap_unlock(ptep - 1, ptl); 163 out: 164 walk->private += nr; 165 cond_resched(); 166 return 0; 167 } 168 169 /* 170 * Do a chunk of "sys_mincore()". We've already checked 171 * all the arguments, we hold the mmap semaphore: we should 172 * just return the amount of info we're asked for. 173 */ 174 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 175 { 176 struct vm_area_struct *vma; 177 unsigned long end; 178 int err; 179 struct mm_walk mincore_walk = { 180 .pmd_entry = mincore_pte_range, 181 .pte_hole = mincore_unmapped_range, 182 .hugetlb_entry = mincore_hugetlb, 183 .private = vec, 184 }; 185 186 vma = find_vma(current->mm, addr); 187 if (!vma || addr < vma->vm_start) 188 return -ENOMEM; 189 mincore_walk.mm = vma->vm_mm; 190 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 191 err = walk_page_range(addr, end, &mincore_walk); 192 if (err < 0) 193 return err; 194 return (end - addr) >> PAGE_SHIFT; 195 } 196 197 /* 198 * The mincore(2) system call. 199 * 200 * mincore() returns the memory residency status of the pages in the 201 * current process's address space specified by [addr, addr + len). 202 * The status is returned in a vector of bytes. The least significant 203 * bit of each byte is 1 if the referenced page is in memory, otherwise 204 * it is zero. 205 * 206 * Because the status of a page can change after mincore() checks it 207 * but before it returns to the application, the returned vector may 208 * contain stale information. Only locked pages are guaranteed to 209 * remain in memory. 210 * 211 * return values: 212 * zero - success 213 * -EFAULT - vec points to an illegal address 214 * -EINVAL - addr is not a multiple of PAGE_SIZE 215 * -ENOMEM - Addresses in the range [addr, addr + len] are 216 * invalid for the address space of this process, or 217 * specify one or more pages which are not currently 218 * mapped 219 * -EAGAIN - A kernel resource was temporarily unavailable. 220 */ 221 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 222 unsigned char __user *, vec) 223 { 224 long retval; 225 unsigned long pages; 226 unsigned char *tmp; 227 228 /* Check the start address: needs to be page-aligned.. */ 229 if (start & ~PAGE_MASK) 230 return -EINVAL; 231 232 /* ..and we need to be passed a valid user-space range */ 233 if (!access_ok(VERIFY_READ, (void __user *) start, len)) 234 return -ENOMEM; 235 236 /* This also avoids any overflows on PAGE_ALIGN */ 237 pages = len >> PAGE_SHIFT; 238 pages += (offset_in_page(len)) != 0; 239 240 if (!access_ok(VERIFY_WRITE, vec, pages)) 241 return -EFAULT; 242 243 tmp = (void *) __get_free_page(GFP_USER); 244 if (!tmp) 245 return -EAGAIN; 246 247 retval = 0; 248 while (pages) { 249 /* 250 * Do at most PAGE_SIZE entries per iteration, due to 251 * the temporary buffer size. 252 */ 253 down_read(¤t->mm->mmap_sem); 254 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 255 up_read(¤t->mm->mmap_sem); 256 257 if (retval <= 0) 258 break; 259 if (copy_to_user(vec, tmp, retval)) { 260 retval = -EFAULT; 261 break; 262 } 263 pages -= retval; 264 vec += retval; 265 start += retval << PAGE_SHIFT; 266 retval = 0; 267 } 268 free_page((unsigned long) tmp); 269 return retval; 270 } 271