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 /* 173 * Do a chunk of "sys_mincore()". We've already checked 174 * all the arguments, we hold the mmap semaphore: we should 175 * just return the amount of info we're asked for. 176 */ 177 static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) 178 { 179 struct vm_area_struct *vma; 180 unsigned long end; 181 int err; 182 struct mm_walk mincore_walk = { 183 .pmd_entry = mincore_pte_range, 184 .pte_hole = mincore_unmapped_range, 185 .hugetlb_entry = mincore_hugetlb, 186 .private = vec, 187 }; 188 189 vma = find_vma(current->mm, addr); 190 if (!vma || addr < vma->vm_start) 191 return -ENOMEM; 192 mincore_walk.mm = vma->vm_mm; 193 end = min(vma->vm_end, addr + (pages << PAGE_SHIFT)); 194 err = walk_page_range(addr, end, &mincore_walk); 195 if (err < 0) 196 return err; 197 return (end - addr) >> PAGE_SHIFT; 198 } 199 200 /* 201 * The mincore(2) system call. 202 * 203 * mincore() returns the memory residency status of the pages in the 204 * current process's address space specified by [addr, addr + len). 205 * The status is returned in a vector of bytes. The least significant 206 * bit of each byte is 1 if the referenced page is in memory, otherwise 207 * it is zero. 208 * 209 * Because the status of a page can change after mincore() checks it 210 * but before it returns to the application, the returned vector may 211 * contain stale information. Only locked pages are guaranteed to 212 * remain in memory. 213 * 214 * return values: 215 * zero - success 216 * -EFAULT - vec points to an illegal address 217 * -EINVAL - addr is not a multiple of PAGE_SIZE 218 * -ENOMEM - Addresses in the range [addr, addr + len] are 219 * invalid for the address space of this process, or 220 * specify one or more pages which are not currently 221 * mapped 222 * -EAGAIN - A kernel resource was temporarily unavailable. 223 */ 224 SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, 225 unsigned char __user *, vec) 226 { 227 long retval; 228 unsigned long pages; 229 unsigned char *tmp; 230 231 /* Check the start address: needs to be page-aligned.. */ 232 if (start & ~PAGE_MASK) 233 return -EINVAL; 234 235 /* ..and we need to be passed a valid user-space range */ 236 if (!access_ok(VERIFY_READ, (void __user *) start, len)) 237 return -ENOMEM; 238 239 /* This also avoids any overflows on PAGE_ALIGN */ 240 pages = len >> PAGE_SHIFT; 241 pages += (offset_in_page(len)) != 0; 242 243 if (!access_ok(VERIFY_WRITE, vec, pages)) 244 return -EFAULT; 245 246 tmp = (void *) __get_free_page(GFP_USER); 247 if (!tmp) 248 return -EAGAIN; 249 250 retval = 0; 251 while (pages) { 252 /* 253 * Do at most PAGE_SIZE entries per iteration, due to 254 * the temporary buffer size. 255 */ 256 down_read(¤t->mm->mmap_sem); 257 retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); 258 up_read(¤t->mm->mmap_sem); 259 260 if (retval <= 0) 261 break; 262 if (copy_to_user(vec, tmp, retval)) { 263 retval = -EFAULT; 264 break; 265 } 266 pages -= retval; 267 vec += retval; 268 start += retval << PAGE_SHIFT; 269 retval = 0; 270 } 271 free_page((unsigned long) tmp); 272 return retval; 273 } 274