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/mm.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 21 #include <linux/uaccess.h> 22 #include <asm/pgtable.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 page = find_get_page(swap_address_space(swp), 72 swp_offset(swp)); 73 } 74 } else 75 page = find_get_page(mapping, pgoff); 76 #else 77 page = find_get_page(mapping, pgoff); 78 #endif 79 if (page) { 80 present = PageUptodate(page); 81 put_page(page); 82 } 83 84 return present; 85 } 86 87 static int __mincore_unmapped_range(unsigned long addr, unsigned long end, 88 struct vm_area_struct *vma, unsigned char *vec) 89 { 90 unsigned long nr = (end - addr) >> PAGE_SHIFT; 91 int i; 92 93 if (vma->vm_file) { 94 pgoff_t pgoff; 95 96 pgoff = linear_page_index(vma, addr); 97 for (i = 0; i < nr; i++, pgoff++) 98 vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); 99 } else { 100 for (i = 0; i < nr; i++) 101 vec[i] = 0; 102 } 103 return nr; 104 } 105 106 static int mincore_unmapped_range(unsigned long addr, unsigned long end, 107 struct mm_walk *walk) 108 { 109 walk->private += __mincore_unmapped_range(addr, end, 110 walk->vma, walk->private); 111 return 0; 112 } 113 114 static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 115 struct mm_walk *walk) 116 { 117 spinlock_t *ptl; 118 struct vm_area_struct *vma = walk->vma; 119 pte_t *ptep; 120 unsigned char *vec = walk->private; 121 int nr = (end - addr) >> PAGE_SHIFT; 122 123 ptl = pmd_trans_huge_lock(pmd, vma); 124 if (ptl) { 125 memset(vec, 1, nr); 126 spin_unlock(ptl); 127 goto out; 128 } 129 130 if (pmd_trans_unstable(pmd)) { 131 __mincore_unmapped_range(addr, end, vma, vec); 132 goto out; 133 } 134 135 ptep = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 136 for (; addr != end; ptep++, addr += PAGE_SIZE) { 137 pte_t pte = *ptep; 138 139 if (pte_none(pte)) 140 __mincore_unmapped_range(addr, addr + PAGE_SIZE, 141 vma, vec); 142 else if (pte_present(pte)) 143 *vec = 1; 144 else { /* pte is a swap entry */ 145 swp_entry_t entry = pte_to_swp_entry(pte); 146 147 if (non_swap_entry(entry)) { 148 /* 149 * migration or hwpoison entries are always 150 * uptodate 151 */ 152 *vec = 1; 153 } else { 154 #ifdef CONFIG_SWAP 155 *vec = mincore_page(swap_address_space(entry), 156 swp_offset(entry)); 157 #else 158 WARN_ON(1); 159 *vec = 1; 160 #endif 161 } 162 } 163 vec++; 164 } 165 pte_unmap_unlock(ptep - 1, ptl); 166 out: 167 walk->private += nr; 168 cond_resched(); 169 return 0; 170 } 171 172 static inline bool can_do_mincore(struct vm_area_struct *vma) 173 { 174 if (vma_is_anonymous(vma)) 175 return true; 176 if (!vma->vm_file) 177 return false; 178 /* 179 * Reveal pagecache information only for non-anonymous mappings that 180 * correspond to the files the calling process could (if tried) open 181 * for writing; otherwise we'd be including shared non-exclusive 182 * mappings, which opens a side channel. 183 */ 184 return inode_owner_or_capable(file_inode(vma->vm_file)) || 185 inode_permission(file_inode(vma->vm_file), MAY_WRITE) == 0; 186 } 187 188 /* 189 * Do a chunk of "sys_mincore()". We've already checked 190 * all the arguments, we hold the mmap semaphore: we should 191 * just return the amount of info we're asked for. 192 */ 193 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 194 { 195 struct vm_area_struct *vma; 196 unsigned long end; 197 int err; 198 struct mm_walk mincore_walk = { 199 .pmd_entry = mincore_pte_range, 200 .pte_hole = mincore_unmapped_range, 201 .hugetlb_entry = mincore_hugetlb, 202 .private = vec, 203 }; 204 205 vma = find_vma(current->mm, addr); 206 if (!vma || addr < vma->vm_start) 207 return -ENOMEM; 208 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 209 if (!can_do_mincore(vma)) { 210 unsigned long pages = DIV_ROUND_UP(end - addr, PAGE_SIZE); 211 memset(vec, 1, pages); 212 return pages; 213 } 214 mincore_walk.mm = vma->vm_mm; 215 err = walk_page_range(addr, end, &mincore_walk); 216 if (err < 0) 217 return err; 218 return (end - addr) >> PAGE_SHIFT; 219 } 220 221 /* 222 * The mincore(2) system call. 223 * 224 * mincore() returns the memory residency status of the pages in the 225 * current process's address space specified by [addr, addr + len). 226 * The status is returned in a vector of bytes. The least significant 227 * bit of each byte is 1 if the referenced page is in memory, otherwise 228 * it is zero. 229 * 230 * Because the status of a page can change after mincore() checks it 231 * but before it returns to the application, the returned vector may 232 * contain stale information. Only locked pages are guaranteed to 233 * remain in memory. 234 * 235 * return values: 236 * zero - success 237 * -EFAULT - vec points to an illegal address 238 * -EINVAL - addr is not a multiple of PAGE_SIZE 239 * -ENOMEM - Addresses in the range [addr, addr + len] are 240 * invalid for the address space of this process, or 241 * specify one or more pages which are not currently 242 * mapped 243 * -EAGAIN - A kernel resource was temporarily unavailable. 244 */ 245 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 246 unsigned char __user *, vec) 247 { 248 long retval; 249 unsigned long pages; 250 unsigned char *tmp; 251 252 /* Check the start address: needs to be page-aligned.. */ 253 if (start & ~PAGE_MASK) 254 return -EINVAL; 255 256 /* ..and we need to be passed a valid user-space range */ 257 if (!access_ok((void __user *) start, len)) 258 return -ENOMEM; 259 260 /* This also avoids any overflows on PAGE_ALIGN */ 261 pages = len >> PAGE_SHIFT; 262 pages += (offset_in_page(len)) != 0; 263 264 if (!access_ok(vec, pages)) 265 return -EFAULT; 266 267 tmp = (void *) __get_free_page(GFP_USER); 268 if (!tmp) 269 return -EAGAIN; 270 271 retval = 0; 272 while (pages) { 273 /* 274 * Do at most PAGE_SIZE entries per iteration, due to 275 * the temporary buffer size. 276 */ 277 down_read(¤t->mm->mmap_sem); 278 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 279 up_read(¤t->mm->mmap_sem); 280 281 if (retval <= 0) 282 break; 283 if (copy_to_user(vec, tmp, retval)) { 284 retval = -EFAULT; 285 break; 286 } 287 pages -= retval; 288 vec += retval; 289 start += retval << PAGE_SHIFT; 290 retval = 0; 291 } 292 free_page((unsigned long) tmp); 293 return retval; 294 } 295