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(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 page *page; 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 page = find_get_incore_page(mapping, index); 64 if (page) { 65 present = PageUptodate(page); 66 put_page(page); 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 if (pmd_trans_unstable(pmd)) { 117 __mincore_unmapped_range(addr, end, vma, vec); 118 goto out; 119 } 120 121 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 122 for (; addr != end; ptep++, addr += PAGE_SIZE) { 123 pte_t pte = *ptep; 124 125 if (pte_none(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(&init_user_ns, 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 }; 180 181 /* 182 * Do a chunk of "sys_mincore()". We've already checked 183 * all the arguments, we hold the mmap semaphore: we should 184 * just return the amount of info we're asked for. 185 */ 186 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 187 { 188 struct vm_area_struct *vma; 189 unsigned long end; 190 int err; 191 192 vma = find_vma(current->mm, addr); 193 if (!vma || addr < vma->vm_start) 194 return -ENOMEM; 195 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 196 if (!can_do_mincore(vma)) { 197 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); 198 memset(vec, 1, pages); 199 return pages; 200 } 201 err = walk_page_range(vma->vm_mm, addr, end, &mincore_walk_ops, vec); 202 if (err < 0) 203 return err; 204 return (end - addr) >> PAGE_SHIFT; 205 } 206 207 /* 208 * The mincore(2) system call. 209 * 210 * mincore() returns the memory residency status of the pages in the 211 * current process's address space specified by [addr, addr + len). 212 * The status is returned in a vector of bytes. The least significant 213 * bit of each byte is 1 if the referenced page is in memory, otherwise 214 * it is zero. 215 * 216 * Because the status of a page can change after mincore() checks it 217 * but before it returns to the application, the returned vector may 218 * contain stale information. Only locked pages are guaranteed to 219 * remain in memory. 220 * 221 * return values: 222 * zero - success 223 * -EFAULT - vec points to an illegal address 224 * -EINVAL - addr is not a multiple of PAGE_SIZE 225 * -ENOMEM - Addresses in the range [addr, addr + len] are 226 * invalid for the address space of this process, or 227 * specify one or more pages which are not currently 228 * mapped 229 * -EAGAIN - A kernel resource was temporarily unavailable. 230 */ 231 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 232 unsigned char __user *, vec) 233 { 234 long retval; 235 unsigned long pages; 236 unsigned char *tmp; 237 238 start = untagged_addr(start); 239 240 /* Check the start address: needs to be page-aligned.. */ 241 if (start & ~PAGE_MASK) 242 return -EINVAL; 243 244 /* ..and we need to be passed a valid user-space range */ 245 if (!access_ok((void __user *) start, len)) 246 return -ENOMEM; 247 248 /* This also avoids any overflows on PAGE_ALIGN */ 249 pages = len >> PAGE_SHIFT; 250 pages += (offset_in_page(len)) != 0; 251 252 if (!access_ok(vec, pages)) 253 return -EFAULT; 254 255 tmp = (void *) __get_free_page(GFP_USER); 256 if (!tmp) 257 return -EAGAIN; 258 259 retval = 0; 260 while (pages) { 261 /* 262 * Do at most PAGE_SIZE entries per iteration, due to 263 * the temporary buffer size. 264 */ 265 mmap_read_lock(current->mm); 266 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 267 mmap_read_unlock(current->mm); 268 269 if (retval <= 0) 270 break; 271 if (copy_to_user(vec, tmp, retval)) { 272 retval = -EFAULT; 273 break; 274 } 275 pages -= retval; 276 vec += retval; 277 start += retval << PAGE_SHIFT; 278 retval = 0; 279 } 280 free_page((unsigned long) tmp); 281 return retval; 282 } 283