1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/mm.h> 3 #include <linux/highmem.h> 4 #include <linux/sched.h> 5 #include <linux/hugetlb.h> 6 7 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 8 struct mm_walk *walk) 9 { 10 pte_t *pte; 11 int err = 0; 12 13 pte = pte_offset_map(pmd, addr); 14 for (;;) { 15 err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk); 16 if (err) 17 break; 18 addr += PAGE_SIZE; 19 if (addr == end) 20 break; 21 pte++; 22 } 23 24 pte_unmap(pte); 25 return err; 26 } 27 28 static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, 29 struct mm_walk *walk) 30 { 31 pmd_t *pmd; 32 unsigned long next; 33 int err = 0; 34 35 pmd = pmd_offset(pud, addr); 36 do { 37 again: 38 next = pmd_addr_end(addr, end); 39 if (pmd_none(*pmd) || !walk->vma) { 40 if (walk->pte_hole) 41 err = walk->pte_hole(addr, next, walk); 42 if (err) 43 break; 44 continue; 45 } 46 /* 47 * This implies that each ->pmd_entry() handler 48 * needs to know about pmd_trans_huge() pmds 49 */ 50 if (walk->pmd_entry) 51 err = walk->pmd_entry(pmd, addr, next, walk); 52 if (err) 53 break; 54 55 /* 56 * Check this here so we only break down trans_huge 57 * pages when we _need_ to 58 */ 59 if (!walk->pte_entry) 60 continue; 61 62 split_huge_pmd(walk->vma, pmd, addr); 63 if (pmd_trans_unstable(pmd)) 64 goto again; 65 err = walk_pte_range(pmd, addr, next, walk); 66 if (err) 67 break; 68 } while (pmd++, addr = next, addr != end); 69 70 return err; 71 } 72 73 static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, 74 struct mm_walk *walk) 75 { 76 pud_t *pud; 77 unsigned long next; 78 int err = 0; 79 80 pud = pud_offset(p4d, addr); 81 do { 82 again: 83 next = pud_addr_end(addr, end); 84 if (pud_none(*pud) || !walk->vma) { 85 if (walk->pte_hole) 86 err = walk->pte_hole(addr, next, walk); 87 if (err) 88 break; 89 continue; 90 } 91 92 if (walk->pud_entry) { 93 spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma); 94 95 if (ptl) { 96 err = walk->pud_entry(pud, addr, next, walk); 97 spin_unlock(ptl); 98 if (err) 99 break; 100 continue; 101 } 102 } 103 104 split_huge_pud(walk->vma, pud, addr); 105 if (pud_none(*pud)) 106 goto again; 107 108 if (walk->pmd_entry || walk->pte_entry) 109 err = walk_pmd_range(pud, addr, next, walk); 110 if (err) 111 break; 112 } while (pud++, addr = next, addr != end); 113 114 return err; 115 } 116 117 static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end, 118 struct mm_walk *walk) 119 { 120 p4d_t *p4d; 121 unsigned long next; 122 int err = 0; 123 124 p4d = p4d_offset(pgd, addr); 125 do { 126 next = p4d_addr_end(addr, end); 127 if (p4d_none_or_clear_bad(p4d)) { 128 if (walk->pte_hole) 129 err = walk->pte_hole(addr, next, walk); 130 if (err) 131 break; 132 continue; 133 } 134 if (walk->pmd_entry || walk->pte_entry) 135 err = walk_pud_range(p4d, addr, next, walk); 136 if (err) 137 break; 138 } while (p4d++, addr = next, addr != end); 139 140 return err; 141 } 142 143 static int walk_pgd_range(unsigned long addr, unsigned long end, 144 struct mm_walk *walk) 145 { 146 pgd_t *pgd; 147 unsigned long next; 148 int err = 0; 149 150 pgd = pgd_offset(walk->mm, addr); 151 do { 152 next = pgd_addr_end(addr, end); 153 if (pgd_none_or_clear_bad(pgd)) { 154 if (walk->pte_hole) 155 err = walk->pte_hole(addr, next, walk); 156 if (err) 157 break; 158 continue; 159 } 160 if (walk->pmd_entry || walk->pte_entry) 161 err = walk_p4d_range(pgd, addr, next, walk); 162 if (err) 163 break; 164 } while (pgd++, addr = next, addr != end); 165 166 return err; 167 } 168 169 #ifdef CONFIG_HUGETLB_PAGE 170 static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr, 171 unsigned long end) 172 { 173 unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h); 174 return boundary < end ? boundary : end; 175 } 176 177 static int walk_hugetlb_range(unsigned long addr, unsigned long end, 178 struct mm_walk *walk) 179 { 180 struct vm_area_struct *vma = walk->vma; 181 struct hstate *h = hstate_vma(vma); 182 unsigned long next; 183 unsigned long hmask = huge_page_mask(h); 184 unsigned long sz = huge_page_size(h); 185 pte_t *pte; 186 int err = 0; 187 188 do { 189 next = hugetlb_entry_end(h, addr, end); 190 pte = huge_pte_offset(walk->mm, addr & hmask, sz); 191 192 if (pte) 193 err = walk->hugetlb_entry(pte, hmask, addr, next, walk); 194 else if (walk->pte_hole) 195 err = walk->pte_hole(addr, next, walk); 196 197 if (err) 198 break; 199 } while (addr = next, addr != end); 200 201 return err; 202 } 203 204 #else /* CONFIG_HUGETLB_PAGE */ 205 static int walk_hugetlb_range(unsigned long addr, unsigned long end, 206 struct mm_walk *walk) 207 { 208 return 0; 209 } 210 211 #endif /* CONFIG_HUGETLB_PAGE */ 212 213 /* 214 * Decide whether we really walk over the current vma on [@start, @end) 215 * or skip it via the returned value. Return 0 if we do walk over the 216 * current vma, and return 1 if we skip the vma. Negative values means 217 * error, where we abort the current walk. 218 */ 219 static int walk_page_test(unsigned long start, unsigned long end, 220 struct mm_walk *walk) 221 { 222 struct vm_area_struct *vma = walk->vma; 223 224 if (walk->test_walk) 225 return walk->test_walk(start, end, walk); 226 227 /* 228 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP 229 * range, so we don't walk over it as we do for normal vmas. However, 230 * Some callers are interested in handling hole range and they don't 231 * want to just ignore any single address range. Such users certainly 232 * define their ->pte_hole() callbacks, so let's delegate them to handle 233 * vma(VM_PFNMAP). 234 */ 235 if (vma->vm_flags & VM_PFNMAP) { 236 int err = 1; 237 if (walk->pte_hole) 238 err = walk->pte_hole(start, end, walk); 239 return err ? err : 1; 240 } 241 return 0; 242 } 243 244 static int __walk_page_range(unsigned long start, unsigned long end, 245 struct mm_walk *walk) 246 { 247 int err = 0; 248 struct vm_area_struct *vma = walk->vma; 249 250 if (vma && is_vm_hugetlb_page(vma)) { 251 if (walk->hugetlb_entry) 252 err = walk_hugetlb_range(start, end, walk); 253 } else 254 err = walk_pgd_range(start, end, walk); 255 256 return err; 257 } 258 259 /** 260 * walk_page_range - walk page table with caller specific callbacks 261 * 262 * Recursively walk the page table tree of the process represented by @walk->mm 263 * within the virtual address range [@start, @end). During walking, we can do 264 * some caller-specific works for each entry, by setting up pmd_entry(), 265 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these 266 * callbacks, the associated entries/pages are just ignored. 267 * The return values of these callbacks are commonly defined like below: 268 * 269 * - 0 : succeeded to handle the current entry, and if you don't reach the 270 * end address yet, continue to walk. 271 * - >0 : succeeded to handle the current entry, and return to the caller 272 * with caller specific value. 273 * - <0 : failed to handle the current entry, and return to the caller 274 * with error code. 275 * 276 * Before starting to walk page table, some callers want to check whether 277 * they really want to walk over the current vma, typically by checking 278 * its vm_flags. walk_page_test() and @walk->test_walk() are used for this 279 * purpose. 280 * 281 * struct mm_walk keeps current values of some common data like vma and pmd, 282 * which are useful for the access from callbacks. If you want to pass some 283 * caller-specific data to callbacks, @walk->private should be helpful. 284 * 285 * Locking: 286 * Callers of walk_page_range() and walk_page_vma() should hold 287 * @walk->mm->mmap_sem, because these function traverse vma list and/or 288 * access to vma's data. 289 */ 290 int walk_page_range(unsigned long start, unsigned long end, 291 struct mm_walk *walk) 292 { 293 int err = 0; 294 unsigned long next; 295 struct vm_area_struct *vma; 296 297 if (start >= end) 298 return -EINVAL; 299 300 if (!walk->mm) 301 return -EINVAL; 302 303 VM_BUG_ON_MM(!rwsem_is_locked(&walk->mm->mmap_sem), walk->mm); 304 305 vma = find_vma(walk->mm, start); 306 do { 307 if (!vma) { /* after the last vma */ 308 walk->vma = NULL; 309 next = end; 310 } else if (start < vma->vm_start) { /* outside vma */ 311 walk->vma = NULL; 312 next = min(end, vma->vm_start); 313 } else { /* inside vma */ 314 walk->vma = vma; 315 next = min(end, vma->vm_end); 316 vma = vma->vm_next; 317 318 err = walk_page_test(start, next, walk); 319 if (err > 0) { 320 /* 321 * positive return values are purely for 322 * controlling the pagewalk, so should never 323 * be passed to the callers. 324 */ 325 err = 0; 326 continue; 327 } 328 if (err < 0) 329 break; 330 } 331 if (walk->vma || walk->pte_hole) 332 err = __walk_page_range(start, next, walk); 333 if (err) 334 break; 335 } while (start = next, start < end); 336 return err; 337 } 338 339 int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk) 340 { 341 int err; 342 343 if (!walk->mm) 344 return -EINVAL; 345 346 VM_BUG_ON(!rwsem_is_locked(&walk->mm->mmap_sem)); 347 VM_BUG_ON(!vma); 348 walk->vma = vma; 349 err = walk_page_test(vma->vm_start, vma->vm_end, walk); 350 if (err > 0) 351 return 0; 352 if (err < 0) 353 return err; 354 return __walk_page_range(vma->vm_start, vma->vm_end, walk); 355 } 356