1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/mm/mincore.c 4 * 5 * Copyright (C) 1994-2006 Linus Torvalds 6 */ 7 8 /* 9 * The mincore() system call. 10 */ 11 #include <linux/pagemap.h> 12 #include <linux/gfp.h> 13 #include <linux/pagewalk.h> 14 #include <linux/mman.h> 15 #include <linux/syscalls.h> 16 #include <linux/swap.h> 17 #include <linux/leafops.h> 18 #include <linux/shmem_fs.h> 19 #include <linux/hugetlb.h> 20 #include <linux/pgtable.h> 21 22 #include <linux/uaccess.h> 23 #include "swap.h" 24 #include "internal.h" 25 26 static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, 27 unsigned long end, struct mm_walk *walk) 28 { 29 #ifdef CONFIG_HUGETLB_PAGE 30 unsigned char present; 31 unsigned char *vec = walk->private; 32 spinlock_t *ptl; 33 34 ptl = huge_pte_lock(hstate_vma(walk->vma), walk->mm, pte); 35 36 /* 37 * Hugepages under user process are always in RAM and never 38 * swapped out, but theoretically it needs to be checked. 39 */ 40 if (!pte) { 41 present = 0; 42 } else { 43 const pte_t ptep = huge_ptep_get(walk->mm, addr, pte); 44 45 if (huge_pte_none(ptep) || pte_is_marker(ptep)) 46 present = 0; 47 else 48 present = 1; 49 } 50 51 for (; addr != end; vec++, addr += PAGE_SIZE) 52 *vec = present; 53 walk->private = vec; 54 spin_unlock(ptl); 55 #else 56 BUG(); 57 #endif 58 return 0; 59 } 60 61 static unsigned char mincore_swap(swp_entry_t entry, bool shmem) 62 { 63 struct swap_info_struct *si; 64 struct folio *folio = NULL; 65 unsigned char present = 0; 66 67 if (!IS_ENABLED(CONFIG_SWAP)) { 68 WARN_ON(1); 69 return 0; 70 } 71 72 /* 73 * Shmem mapping may contain swapin error entries, which are 74 * absent. Page table may contain migration or hwpoison 75 * entries which are always uptodate. 76 */ 77 if (!softleaf_is_swap(entry)) 78 return !shmem; 79 80 /* 81 * Shmem mapping lookup is lockless, so we need to grab the swap 82 * device. mincore page table walk locks the PTL, and the swap 83 * device is stable, avoid touching the si for better performance. 84 */ 85 if (shmem) { 86 si = get_swap_device(entry); 87 if (!si) 88 return 0; 89 } 90 folio = swap_cache_get_folio(entry); 91 if (shmem) 92 put_swap_device(si); 93 /* The swap cache space contains either folio, shadow or NULL */ 94 if (folio && !xa_is_value(folio)) { 95 present = folio_test_uptodate(folio); 96 folio_put(folio); 97 } 98 99 return present; 100 } 101 102 /* 103 * Later we can get more picky about what "in core" means precisely. 104 * For now, simply check to see if the page is in the page cache, 105 * and is up to date; i.e. that no page-in operation would be required 106 * at this time if an application were to map and access this page. 107 */ 108 static unsigned char mincore_page(struct address_space *mapping, pgoff_t index) 109 { 110 unsigned char present = 0; 111 struct folio *folio; 112 113 /* 114 * When tmpfs swaps out a page from a file, any process mapping that 115 * file will not get a swp_entry_t in its pte, but rather it is like 116 * any other file mapping (ie. marked !present and faulted in with 117 * tmpfs's .fault). So swapped out tmpfs mappings are tested here. 118 */ 119 folio = filemap_get_entry(mapping, index); 120 if (folio) { 121 if (xa_is_value(folio)) { 122 if (shmem_mapping(mapping)) 123 return mincore_swap(radix_to_swp_entry(folio), 124 true); 125 else 126 return 0; 127 } 128 present = folio_test_uptodate(folio); 129 folio_put(folio); 130 } 131 132 return present; 133 } 134 135 static int __mincore_unmapped_range(unsigned long addr, unsigned long end, 136 struct vm_area_struct *vma, unsigned char *vec) 137 { 138 unsigned long nr = (end - addr) >> PAGE_SHIFT; 139 int i; 140 141 if (vma->vm_file) { 142 pgoff_t pgoff; 143 144 pgoff = linear_page_index(vma, addr); 145 for (i = 0; i < nr; i++, pgoff++) 146 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 147 } else { 148 for (i = 0; i < nr; i++) 149 vec[i] = 0; 150 } 151 return nr; 152 } 153 154 static int mincore_unmapped_range(unsigned long addr, unsigned long end, 155 __always_unused int depth, 156 struct mm_walk *walk) 157 { 158 walk->private += __mincore_unmapped_range(addr, end, 159 walk->vma, walk->private); 160 return 0; 161 } 162 163 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 164 struct mm_walk *walk) 165 { 166 spinlock_t *ptl; 167 struct vm_area_struct *vma = walk->vma; 168 pte_t *ptep; 169 unsigned char *vec = walk->private; 170 int nr = (end - addr) >> PAGE_SHIFT; 171 int step, i; 172 173 ptl = pmd_trans_huge_lock(pmd, vma); 174 if (ptl) { 175 memset(vec, 1, nr); 176 spin_unlock(ptl); 177 goto out; 178 } 179 180 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 181 if (!ptep) { 182 walk->action = ACTION_AGAIN; 183 return 0; 184 } 185 for (; addr != end; ptep += step, addr += step * PAGE_SIZE) { 186 pte_t pte = ptep_get(ptep); 187 188 step = 1; 189 /* We need to do cache lookup too for markers */ 190 if (pte_none(pte) || pte_is_marker(pte)) 191 __mincore_unmapped_range(addr, addr + PAGE_SIZE, 192 vma, vec); 193 else if (pte_present(pte)) { 194 unsigned int batch = pte_batch_hint(ptep, pte); 195 196 if (batch > 1) { 197 unsigned int max_nr = (end - addr) >> PAGE_SHIFT; 198 199 step = min_t(unsigned int, batch, max_nr); 200 } 201 202 for (i = 0; i < step; i++) 203 vec[i] = 1; 204 } else { /* pte is a swap entry */ 205 const softleaf_t entry = softleaf_from_pte(pte); 206 207 *vec = mincore_swap(entry, false); 208 } 209 vec += step; 210 } 211 pte_unmap_unlock(ptep - 1, ptl); 212 out: 213 walk->private += nr; 214 cond_resched(); 215 return 0; 216 } 217 218 static inline bool can_do_mincore(struct vm_area_struct *vma) 219 { 220 if (vma_is_anonymous(vma)) 221 return true; 222 if (!vma->vm_file) 223 return false; 224 /* 225 * Reveal pagecache information only for non-anonymous mappings that 226 * correspond to the files the calling process could (if tried) open 227 * for writing; otherwise we'd be including shared non-exclusive 228 * mappings, which opens a side channel. 229 */ 230 return inode_owner_or_capable(&nop_mnt_idmap, 231 file_inode(vma->vm_file)) || 232 file_permission(vma->vm_file, MAY_WRITE) == 0; 233 } 234 235 static const struct mm_walk_ops mincore_walk_ops = { 236 .pmd_entry = mincore_pte_range, 237 .pte_hole = mincore_unmapped_range, 238 .hugetlb_entry = mincore_hugetlb, 239 .walk_lock = PGWALK_RDLOCK, 240 }; 241 242 /* 243 * Do a chunk of "sys_mincore()". We've already checked 244 * all the arguments, we hold the mmap semaphore: we should 245 * just return the amount of info we're asked for. 246 */ 247 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 248 { 249 struct vm_area_struct *vma; 250 unsigned long end; 251 int err; 252 253 vma = vma_lookup(current->mm, addr); 254 if (!vma) 255 return -ENOMEM; 256 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 257 if (!can_do_mincore(vma)) { 258 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); 259 memset(vec, 1, pages); 260 return pages; 261 } 262 err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec); 263 if (err < 0) 264 return err; 265 return (end - addr) >> PAGE_SHIFT; 266 } 267 268 /* 269 * The mincore(2) system call. 270 * 271 * mincore() returns the memory residency status of the pages in the 272 * current process's address space specified by [addr, addr + len). 273 * The status is returned in a vector of bytes. The least significant 274 * bit of each byte is 1 if the referenced page is in memory, otherwise 275 * it is zero. 276 * 277 * Because the status of a page can change after mincore() checks it 278 * but before it returns to the application, the returned vector may 279 * contain stale information. Only locked pages are guaranteed to 280 * remain in memory. 281 * 282 * return values: 283 * zero - success 284 * -EFAULT - vec points to an illegal address 285 * -EINVAL - addr is not a multiple of PAGE_SIZE 286 * -ENOMEM - Addresses in the range [addr, addr + len] are 287 * invalid for the address space of this process, or 288 * specify one or more pages which are not currently 289 * mapped 290 * -EAGAIN - A kernel resource was temporarily unavailable. 291 */ 292 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 293 unsigned char __user *, vec) 294 { 295 long retval; 296 unsigned long pages; 297 unsigned char *tmp; 298 299 start = untagged_addr(start); 300 301 /* Check the start address: needs to be page-aligned.. */ 302 if (unlikely(start & ~PAGE_MASK)) 303 return -EINVAL; 304 305 /* ..and we need to be passed a valid user-space range */ 306 if (!access_ok((void __user *) start, len)) 307 return -ENOMEM; 308 309 /* This also avoids any overflows on PAGE_ALIGN */ 310 pages = len >> PAGE_SHIFT; 311 pages += (offset_in_page(len)) != 0; 312 313 if (!access_ok(vec, pages)) 314 return -EFAULT; 315 316 tmp = (void *) __get_free_page(GFP_USER); 317 if (!tmp) 318 return -EAGAIN; 319 320 retval = 0; 321 while (pages) { 322 /* 323 * Do at most PAGE_SIZE entries per iteration, due to 324 * the temporary buffer size. 325 */ 326 mmap_read_lock(current->mm); 327 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 328 mmap_read_unlock(current->mm); 329 330 if (retval <= 0) 331 break; 332 if (copy_to_user(vec, tmp, retval)) { 333 retval = -EFAULT; 334 break; 335 } 336 pages -= retval; 337 vec += retval; 338 start += retval << PAGE_SHIFT; 339 retval = 0; 340 } 341 free_page((unsigned long) tmp); 342 return retval; 343 } 344