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