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/swapops.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 25 static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, 26 unsigned long end, struct mm_walk *walk) 27 { 28 #ifdef CONFIG_HUGETLB_PAGE 29 unsigned char present; 30 unsigned char *vec = walk->private; 31 32 /* 33 * Hugepages under user process are always in RAM and never 34 * swapped out, but theoretically it needs to be checked. 35 */ 36 present = pte && !huge_pte_none_mostly(huge_ptep_get(pte)); 37 for (; addr != end; vec++, addr += PAGE_SIZE) 38 *vec = present; 39 walk->private = vec; 40 #else 41 BUG(); 42 #endif 43 return 0; 44 } 45 46 /* 47 * Later we can get more picky about what "in core" means precisely. 48 * For now, simply check to see if the page is in the page cache, 49 * and is up to date; i.e. that no page-in operation would be required 50 * at this time if an application were to map and access this page. 51 */ 52 static unsigned char mincore_page(struct address_space *mapping, pgoff_t index) 53 { 54 unsigned char present = 0; 55 struct folio *folio; 56 57 /* 58 * When tmpfs swaps out a page from a file, any process mapping that 59 * file will not get a swp_entry_t in its pte, but rather it is like 60 * any other file mapping (ie. marked !present and faulted in with 61 * tmpfs's .fault). So swapped out tmpfs mappings are tested here. 62 */ 63 folio = filemap_get_incore_folio(mapping, index); 64 if (!IS_ERR(folio)) { 65 present = folio_test_uptodate(folio); 66 folio_put(folio); 67 } 68 69 return present; 70 } 71 72 static int __mincore_unmapped_range(unsigned long addr, unsigned long end, 73 struct vm_area_struct *vma, unsigned char *vec) 74 { 75 unsigned long nr = (end - addr) >> PAGE_SHIFT; 76 int i; 77 78 if (vma->vm_file) { 79 pgoff_t pgoff; 80 81 pgoff = linear_page_index(vma, addr); 82 for (i = 0; i < nr; i++, pgoff++) 83 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 84 } else { 85 for (i = 0; i < nr; i++) 86 vec[i] = 0; 87 } 88 return nr; 89 } 90 91 static int mincore_unmapped_range(unsigned long addr, unsigned long end, 92 __always_unused int depth, 93 struct mm_walk *walk) 94 { 95 walk->private += __mincore_unmapped_range(addr, end, 96 walk->vma, walk->private); 97 return 0; 98 } 99 100 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 101 struct mm_walk *walk) 102 { 103 spinlock_t *ptl; 104 struct vm_area_struct *vma = walk->vma; 105 pte_t *ptep; 106 unsigned char *vec = walk->private; 107 int nr = (end - addr) >> PAGE_SHIFT; 108 109 ptl = pmd_trans_huge_lock(pmd, vma); 110 if (ptl) { 111 memset(vec, 1, nr); 112 spin_unlock(ptl); 113 goto out; 114 } 115 116 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 117 if (!ptep) { 118 walk->action = ACTION_AGAIN; 119 return 0; 120 } 121 for (; addr != end; ptep++, addr += PAGE_SIZE) { 122 pte_t pte = ptep_get(ptep); 123 124 /* We need to do cache lookup too for pte markers */ 125 if (pte_none_mostly(pte)) 126 __mincore_unmapped_range(addr, addr + PAGE_SIZE, 127 vma, vec); 128 else if (pte_present(pte)) 129 *vec = 1; 130 else { /* pte is a swap entry */ 131 swp_entry_t entry = pte_to_swp_entry(pte); 132 133 if (non_swap_entry(entry)) { 134 /* 135 * migration or hwpoison entries are always 136 * uptodate 137 */ 138 *vec = 1; 139 } else { 140 #ifdef CONFIG_SWAP 141 *vec = mincore_page(swap_address_space(entry), 142 swp_offset(entry)); 143 #else 144 WARN_ON(1); 145 *vec = 1; 146 #endif 147 } 148 } 149 vec++; 150 } 151 pte_unmap_unlock(ptep - 1, ptl); 152 out: 153 walk->private += nr; 154 cond_resched(); 155 return 0; 156 } 157 158 static inline bool can_do_mincore(struct vm_area_struct *vma) 159 { 160 if (vma_is_anonymous(vma)) 161 return true; 162 if (!vma->vm_file) 163 return false; 164 /* 165 * Reveal pagecache information only for non-anonymous mappings that 166 * correspond to the files the calling process could (if tried) open 167 * for writing; otherwise we'd be including shared non-exclusive 168 * mappings, which opens a side channel. 169 */ 170 return inode_owner_or_capable(&nop_mnt_idmap, 171 file_inode(vma->vm_file)) || 172 file_permission(vma->vm_file, MAY_WRITE) == 0; 173 } 174 175 static const struct mm_walk_ops mincore_walk_ops = { 176 .pmd_entry = mincore_pte_range, 177 .pte_hole = mincore_unmapped_range, 178 .hugetlb_entry = mincore_hugetlb, 179 .walk_lock = PGWALK_RDLOCK, 180 }; 181 182 /* 183 * Do a chunk of "sys_mincore()". We've already checked 184 * all the arguments, we hold the mmap semaphore: we should 185 * just return the amount of info we're asked for. 186 */ 187 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 188 { 189 struct vm_area_struct *vma; 190 unsigned long end; 191 int err; 192 193 vma = vma_lookup(current->mm, addr); 194 if (!vma) 195 return -ENOMEM; 196 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 197 if (!can_do_mincore(vma)) { 198 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); 199 memset(vec, 1, pages); 200 return pages; 201 } 202 err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec); 203 if (err < 0) 204 return err; 205 return (end - addr) >> PAGE_SHIFT; 206 } 207 208 /* 209 * The mincore(2) system call. 210 * 211 * mincore() returns the memory residency status of the pages in the 212 * current process's address space specified by [addr, addr + len). 213 * The status is returned in a vector of bytes. The least significant 214 * bit of each byte is 1 if the referenced page is in memory, otherwise 215 * it is zero. 216 * 217 * Because the status of a page can change after mincore() checks it 218 * but before it returns to the application, the returned vector may 219 * contain stale information. Only locked pages are guaranteed to 220 * remain in memory. 221 * 222 * return values: 223 * zero - success 224 * -EFAULT - vec points to an illegal address 225 * -EINVAL - addr is not a multiple of PAGE_SIZE 226 * -ENOMEM - Addresses in the range [addr, addr + len] are 227 * invalid for the address space of this process, or 228 * specify one or more pages which are not currently 229 * mapped 230 * -EAGAIN - A kernel resource was temporarily unavailable. 231 */ 232 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 233 unsigned char __user *, vec) 234 { 235 long retval; 236 unsigned long pages; 237 unsigned char *tmp; 238 239 start = untagged_addr(start); 240 241 /* Check the start address: needs to be page-aligned.. */ 242 if (start & ~PAGE_MASK) 243 return -EINVAL; 244 245 /* ..and we need to be passed a valid user-space range */ 246 if (!access_ok((void __user *) start, len)) 247 return -ENOMEM; 248 249 /* This also avoids any overflows on PAGE_ALIGN */ 250 pages = len >> PAGE_SHIFT; 251 pages += (offset_in_page(len)) != 0; 252 253 if (!access_ok(vec, pages)) 254 return -EFAULT; 255 256 tmp = (void *) __get_free_page(GFP_USER); 257 if (!tmp) 258 return -EAGAIN; 259 260 retval = 0; 261 while (pages) { 262 /* 263 * Do at most PAGE_SIZE entries per iteration, due to 264 * the temporary buffer size. 265 */ 266 mmap_read_lock(current->mm); 267 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 268 mmap_read_unlock(current->mm); 269 270 if (retval <= 0) 271 break; 272 if (copy_to_user(vec, tmp, retval)) { 273 retval = -EFAULT; 274 break; 275 } 276 pages -= retval; 277 vec += retval; 278 start += retval << PAGE_SHIFT; 279 retval = 0; 280 } 281 free_page((unsigned long) tmp); 282 return retval; 283 } 284