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 index) 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 page = find_get_incore_page(mapping, index); 63 if (page) { 64 present = PageUptodate(page); 65 put_page(page); 66 } 67 68 return present; 69 } 70 71 static int __mincore_unmapped_range(unsigned long addr, unsigned long end, 72 struct vm_area_struct *vma, unsigned char *vec) 73 { 74 unsigned long nr = (end - addr) >> PAGE_SHIFT; 75 int i; 76 77 if (vma->vm_file) { 78 pgoff_t pgoff; 79 80 pgoff = linear_page_index(vma, addr); 81 for (i = 0; i < nr; i++, pgoff++) 82 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 83 } else { 84 for (i = 0; i < nr; i++) 85 vec[i] = 0; 86 } 87 return nr; 88 } 89 90 static int mincore_unmapped_range(unsigned long addr, unsigned long end, 91 __always_unused int depth, 92 struct mm_walk *walk) 93 { 94 walk->private += __mincore_unmapped_range(addr, end, 95 walk->vma, walk->private); 96 return 0; 97 } 98 99 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 100 struct mm_walk *walk) 101 { 102 spinlock_t *ptl; 103 struct vm_area_struct *vma = walk->vma; 104 pte_t *ptep; 105 unsigned char *vec = walk->private; 106 int nr = (end - addr) >> PAGE_SHIFT; 107 108 ptl = pmd_trans_huge_lock(pmd, vma); 109 if (ptl) { 110 memset(vec, 1, nr); 111 spin_unlock(ptl); 112 goto out; 113 } 114 115 if (pmd_trans_unstable(pmd)) { 116 __mincore_unmapped_range(addr, end, vma, vec); 117 goto out; 118 } 119 120 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 121 for (; addr != end; ptep++, addr += PAGE_SIZE) { 122 pte_t pte = *ptep; 123 124 if (pte_none(pte)) 125 __mincore_unmapped_range(addr, addr + PAGE_SIZE, 126 vma, vec); 127 else if (pte_present(pte)) 128 *vec = 1; 129 else { /* pte is a swap entry */ 130 swp_entry_t entry = pte_to_swp_entry(pte); 131 132 if (non_swap_entry(entry)) { 133 /* 134 * migration or hwpoison entries are always 135 * uptodate 136 */ 137 *vec = 1; 138 } else { 139 #ifdef CONFIG_SWAP 140 *vec = mincore_page(swap_address_space(entry), 141 swp_offset(entry)); 142 #else 143 WARN_ON(1); 144 *vec = 1; 145 #endif 146 } 147 } 148 vec++; 149 } 150 pte_unmap_unlock(ptep - 1, ptl); 151 out: 152 walk->private += nr; 153 cond_resched(); 154 return 0; 155 } 156 157 static inline bool can_do_mincore(struct vm_area_struct *vma) 158 { 159 if (vma_is_anonymous(vma)) 160 return true; 161 if (!vma->vm_file) 162 return false; 163 /* 164 * Reveal pagecache information only for non-anonymous mappings that 165 * correspond to the files the calling process could (if tried) open 166 * for writing; otherwise we'd be including shared non-exclusive 167 * mappings, which opens a side channel. 168 */ 169 return inode_owner_or_capable(&init_user_ns, 170 file_inode(vma->vm_file)) || 171 file_permission(vma->vm_file, MAY_WRITE) == 0; 172 } 173 174 static const struct mm_walk_ops mincore_walk_ops = { 175 .pmd_entry = mincore_pte_range, 176 .pte_hole = mincore_unmapped_range, 177 .hugetlb_entry = mincore_hugetlb, 178 }; 179 180 /* 181 * Do a chunk of "sys_mincore()". We've already checked 182 * all the arguments, we hold the mmap semaphore: we should 183 * just return the amount of info we're asked for. 184 */ 185 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 186 { 187 struct vm_area_struct *vma; 188 unsigned long end; 189 int err; 190 191 vma = find_vma(current->mm, addr); 192 if (!vma || addr < vma->vm_start) 193 return -ENOMEM; 194 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 195 if (!can_do_mincore(vma)) { 196 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); 197 memset(vec, 1, pages); 198 return pages; 199 } 200 err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec); 201 if (err < 0) 202 return err; 203 return (end - addr) >> PAGE_SHIFT; 204 } 205 206 /* 207 * The mincore(2) system call. 208 * 209 * mincore() returns the memory residency status of the pages in the 210 * current process's address space specified by [addr, addr + len). 211 * The status is returned in a vector of bytes. The least significant 212 * bit of each byte is 1 if the referenced page is in memory, otherwise 213 * it is zero. 214 * 215 * Because the status of a page can change after mincore() checks it 216 * but before it returns to the application, the returned vector may 217 * contain stale information. Only locked pages are guaranteed to 218 * remain in memory. 219 * 220 * return values: 221 * zero - success 222 * -EFAULT - vec points to an illegal address 223 * -EINVAL - addr is not a multiple of PAGE_SIZE 224 * -ENOMEM - Addresses in the range [addr, addr + len] are 225 * invalid for the address space of this process, or 226 * specify one or more pages which are not currently 227 * mapped 228 * -EAGAIN - A kernel resource was temporarily unavailable. 229 */ 230 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 231 unsigned char __user *, vec) 232 { 233 long retval; 234 unsigned long pages; 235 unsigned char *tmp; 236 237 start = untagged_addr(start); 238 239 /* Check the start address: needs to be page-aligned.. */ 240 if (start & ~PAGE_MASK) 241 return -EINVAL; 242 243 /* ..and we need to be passed a valid user-space range */ 244 if (!access_ok((void __user *) start, len)) 245 return -ENOMEM; 246 247 /* This also avoids any overflows on PAGE_ALIGN */ 248 pages = len >> PAGE_SHIFT; 249 pages += (offset_in_page(len)) != 0; 250 251 if (!access_ok(vec, pages)) 252 return -EFAULT; 253 254 tmp = (void *) __get_free_page(GFP_USER); 255 if (!tmp) 256 return -EAGAIN; 257 258 retval = 0; 259 while (pages) { 260 /* 261 * Do at most PAGE_SIZE entries per iteration, due to 262 * the temporary buffer size. 263 */ 264 mmap_read_lock(current->mm); 265 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 266 mmap_read_unlock(current->mm); 267 268 if (retval <= 0) 269 break; 270 if (copy_to_user(vec, tmp, retval)) { 271 retval = -EFAULT; 272 break; 273 } 274 pages -= retval; 275 vec += retval; 276 start += retval << PAGE_SHIFT; 277 retval = 0; 278 } 279 free_page((unsigned long) tmp); 280 return retval; 281 } 282