1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/pagewalk.h>
3 #include <linux/highmem.h>
4 #include <linux/sched.h>
5 #include <linux/hugetlb.h>
6 
7 /*
8  * We want to know the real level where a entry is located ignoring any
9  * folding of levels which may be happening. For example if p4d is folded then
10  * a missing entry found at level 1 (p4d) is actually at level 0 (pgd).
11  */
real_depth(int depth)12 static int real_depth(int depth)
13 {
14 	if (depth == 3 && PTRS_PER_PMD == 1)
15 		depth = 2;
16 	if (depth == 2 && PTRS_PER_PUD == 1)
17 		depth = 1;
18 	if (depth == 1 && PTRS_PER_P4D == 1)
19 		depth = 0;
20 	return depth;
21 }
22 
walk_pte_range_inner(pte_t * pte,unsigned long addr,unsigned long end,struct mm_walk * walk)23 static int walk_pte_range_inner(pte_t *pte, unsigned long addr,
24 				unsigned long end, struct mm_walk *walk)
25 {
26 	const struct mm_walk_ops *ops = walk->ops;
27 	int err = 0;
28 
29 	for (;;) {
30 		err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
31 		if (err)
32 		       break;
33 		if (addr >= end - PAGE_SIZE)
34 			break;
35 		addr += PAGE_SIZE;
36 		pte++;
37 	}
38 	return err;
39 }
40 
walk_pte_range(pmd_t * pmd,unsigned long addr,unsigned long end,struct mm_walk * walk)41 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
42 			  struct mm_walk *walk)
43 {
44 	pte_t *pte;
45 	int err = 0;
46 	spinlock_t *ptl;
47 
48 	if (walk->no_vma) {
49 		pte = pte_offset_map(pmd, addr);
50 		err = walk_pte_range_inner(pte, addr, end, walk);
51 		pte_unmap(pte);
52 	} else {
53 		pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl);
54 		err = walk_pte_range_inner(pte, addr, end, walk);
55 		pte_unmap_unlock(pte, ptl);
56 	}
57 
58 	return err;
59 }
60 
61 #ifdef CONFIG_ARCH_HAS_HUGEPD
walk_hugepd_range(hugepd_t * phpd,unsigned long addr,unsigned long end,struct mm_walk * walk,int pdshift)62 static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
63 			     unsigned long end, struct mm_walk *walk, int pdshift)
64 {
65 	int err = 0;
66 	const struct mm_walk_ops *ops = walk->ops;
67 	int shift = hugepd_shift(*phpd);
68 	int page_size = 1 << shift;
69 
70 	if (!ops->pte_entry)
71 		return 0;
72 
73 	if (addr & (page_size - 1))
74 		return 0;
75 
76 	for (;;) {
77 		pte_t *pte;
78 
79 		spin_lock(&walk->mm->page_table_lock);
80 		pte = hugepte_offset(*phpd, addr, pdshift);
81 		err = ops->pte_entry(pte, addr, addr + page_size, walk);
82 		spin_unlock(&walk->mm->page_table_lock);
83 
84 		if (err)
85 			break;
86 		if (addr >= end - page_size)
87 			break;
88 		addr += page_size;
89 	}
90 	return err;
91 }
92 #else
walk_hugepd_range(hugepd_t * phpd,unsigned long addr,unsigned long end,struct mm_walk * walk,int pdshift)93 static int walk_hugepd_range(hugepd_t *phpd, unsigned long addr,
94 			     unsigned long end, struct mm_walk *walk, int pdshift)
95 {
96 	return 0;
97 }
98 #endif
99 
walk_pmd_range(pud_t * pud,unsigned long addr,unsigned long end,struct mm_walk * walk)100 static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
101 			  struct mm_walk *walk)
102 {
103 	pmd_t *pmd;
104 	unsigned long next;
105 	const struct mm_walk_ops *ops = walk->ops;
106 	int err = 0;
107 	int depth = real_depth(3);
108 
109 	pmd = pmd_offset(pud, addr);
110 	do {
111 again:
112 		next = pmd_addr_end(addr, end);
113 		if (pmd_none(*pmd) || (!walk->vma && !walk->no_vma)) {
114 			if (ops->pte_hole)
115 				err = ops->pte_hole(addr, next, depth, walk);
116 			if (err)
117 				break;
118 			continue;
119 		}
120 
121 		walk->action = ACTION_SUBTREE;
122 
123 		/*
124 		 * This implies that each ->pmd_entry() handler
125 		 * needs to know about pmd_trans_huge() pmds
126 		 */
127 		if (ops->pmd_entry)
128 			err = ops->pmd_entry(pmd, addr, next, walk);
129 		if (err)
130 			break;
131 
132 		if (walk->action == ACTION_AGAIN)
133 			goto again;
134 
135 		/*
136 		 * Check this here so we only break down trans_huge
137 		 * pages when we _need_ to
138 		 */
139 		if ((!walk->vma && (pmd_leaf(*pmd) || !pmd_present(*pmd))) ||
140 		    walk->action == ACTION_CONTINUE ||
141 		    !(ops->pte_entry))
142 			continue;
143 
144 		if (walk->vma) {
145 			split_huge_pmd(walk->vma, pmd, addr);
146 			if (pmd_trans_unstable(pmd))
147 				goto again;
148 		}
149 
150 		if (is_hugepd(__hugepd(pmd_val(*pmd))))
151 			err = walk_hugepd_range((hugepd_t *)pmd, addr, next, walk, PMD_SHIFT);
152 		else
153 			err = walk_pte_range(pmd, addr, next, walk);
154 		if (err)
155 			break;
156 	} while (pmd++, addr = next, addr != end);
157 
158 	return err;
159 }
160 
walk_pud_range(p4d_t * p4d,unsigned long addr,unsigned long end,struct mm_walk * walk)161 static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
162 			  struct mm_walk *walk)
163 {
164 	pud_t *pud;
165 	unsigned long next;
166 	const struct mm_walk_ops *ops = walk->ops;
167 	int err = 0;
168 	int depth = real_depth(2);
169 
170 	pud = pud_offset(p4d, addr);
171 	do {
172  again:
173 		next = pud_addr_end(addr, end);
174 		if (pud_none(*pud) || (!walk->vma && !walk->no_vma)) {
175 			if (ops->pte_hole)
176 				err = ops->pte_hole(addr, next, depth, walk);
177 			if (err)
178 				break;
179 			continue;
180 		}
181 
182 		walk->action = ACTION_SUBTREE;
183 
184 		if (ops->pud_entry)
185 			err = ops->pud_entry(pud, addr, next, walk);
186 		if (err)
187 			break;
188 
189 		if (walk->action == ACTION_AGAIN)
190 			goto again;
191 
192 		if ((!walk->vma && (pud_leaf(*pud) || !pud_present(*pud))) ||
193 		    walk->action == ACTION_CONTINUE ||
194 		    !(ops->pmd_entry || ops->pte_entry))
195 			continue;
196 
197 		if (walk->vma)
198 			split_huge_pud(walk->vma, pud, addr);
199 		if (pud_none(*pud))
200 			goto again;
201 
202 		if (is_hugepd(__hugepd(pud_val(*pud))))
203 			err = walk_hugepd_range((hugepd_t *)pud, addr, next, walk, PUD_SHIFT);
204 		else
205 			err = walk_pmd_range(pud, addr, next, walk);
206 		if (err)
207 			break;
208 	} while (pud++, addr = next, addr != end);
209 
210 	return err;
211 }
212 
walk_p4d_range(pgd_t * pgd,unsigned long addr,unsigned long end,struct mm_walk * walk)213 static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
214 			  struct mm_walk *walk)
215 {
216 	p4d_t *p4d;
217 	unsigned long next;
218 	const struct mm_walk_ops *ops = walk->ops;
219 	int err = 0;
220 	int depth = real_depth(1);
221 
222 	p4d = p4d_offset(pgd, addr);
223 	do {
224 		next = p4d_addr_end(addr, end);
225 		if (p4d_none_or_clear_bad(p4d)) {
226 			if (ops->pte_hole)
227 				err = ops->pte_hole(addr, next, depth, walk);
228 			if (err)
229 				break;
230 			continue;
231 		}
232 		if (ops->p4d_entry) {
233 			err = ops->p4d_entry(p4d, addr, next, walk);
234 			if (err)
235 				break;
236 		}
237 		if (is_hugepd(__hugepd(p4d_val(*p4d))))
238 			err = walk_hugepd_range((hugepd_t *)p4d, addr, next, walk, P4D_SHIFT);
239 		else if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
240 			err = walk_pud_range(p4d, addr, next, walk);
241 		if (err)
242 			break;
243 	} while (p4d++, addr = next, addr != end);
244 
245 	return err;
246 }
247 
walk_pgd_range(unsigned long addr,unsigned long end,struct mm_walk * walk)248 static int walk_pgd_range(unsigned long addr, unsigned long end,
249 			  struct mm_walk *walk)
250 {
251 	pgd_t *pgd;
252 	unsigned long next;
253 	const struct mm_walk_ops *ops = walk->ops;
254 	int err = 0;
255 
256 	if (walk->pgd)
257 		pgd = walk->pgd + pgd_index(addr);
258 	else
259 		pgd = pgd_offset(walk->mm, addr);
260 	do {
261 		next = pgd_addr_end(addr, end);
262 		if (pgd_none_or_clear_bad(pgd)) {
263 			if (ops->pte_hole)
264 				err = ops->pte_hole(addr, next, 0, walk);
265 			if (err)
266 				break;
267 			continue;
268 		}
269 		if (ops->pgd_entry) {
270 			err = ops->pgd_entry(pgd, addr, next, walk);
271 			if (err)
272 				break;
273 		}
274 		if (is_hugepd(__hugepd(pgd_val(*pgd))))
275 			err = walk_hugepd_range((hugepd_t *)pgd, addr, next, walk, PGDIR_SHIFT);
276 		else if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry || ops->pte_entry)
277 			err = walk_p4d_range(pgd, addr, next, walk);
278 		if (err)
279 			break;
280 	} while (pgd++, addr = next, addr != end);
281 
282 	return err;
283 }
284 
285 #ifdef CONFIG_HUGETLB_PAGE
hugetlb_entry_end(struct hstate * h,unsigned long addr,unsigned long end)286 static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr,
287 				       unsigned long end)
288 {
289 	unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h);
290 	return boundary < end ? boundary : end;
291 }
292 
walk_hugetlb_range(unsigned long addr,unsigned long end,struct mm_walk * walk)293 static int walk_hugetlb_range(unsigned long addr, unsigned long end,
294 			      struct mm_walk *walk)
295 {
296 	struct vm_area_struct *vma = walk->vma;
297 	struct hstate *h = hstate_vma(vma);
298 	unsigned long next;
299 	unsigned long hmask = huge_page_mask(h);
300 	unsigned long sz = huge_page_size(h);
301 	pte_t *pte;
302 	const struct mm_walk_ops *ops = walk->ops;
303 	int err = 0;
304 
305 	do {
306 		next = hugetlb_entry_end(h, addr, end);
307 		pte = huge_pte_offset(walk->mm, addr & hmask, sz);
308 
309 		if (pte)
310 			err = ops->hugetlb_entry(pte, hmask, addr, next, walk);
311 		else if (ops->pte_hole)
312 			err = ops->pte_hole(addr, next, -1, walk);
313 
314 		if (err)
315 			break;
316 	} while (addr = next, addr != end);
317 
318 	return err;
319 }
320 
321 #else /* CONFIG_HUGETLB_PAGE */
walk_hugetlb_range(unsigned long addr,unsigned long end,struct mm_walk * walk)322 static int walk_hugetlb_range(unsigned long addr, unsigned long end,
323 			      struct mm_walk *walk)
324 {
325 	return 0;
326 }
327 
328 #endif /* CONFIG_HUGETLB_PAGE */
329 
330 /*
331  * Decide whether we really walk over the current vma on [@start, @end)
332  * or skip it via the returned value. Return 0 if we do walk over the
333  * current vma, and return 1 if we skip the vma. Negative values means
334  * error, where we abort the current walk.
335  */
walk_page_test(unsigned long start,unsigned long end,struct mm_walk * walk)336 static int walk_page_test(unsigned long start, unsigned long end,
337 			struct mm_walk *walk)
338 {
339 	struct vm_area_struct *vma = walk->vma;
340 	const struct mm_walk_ops *ops = walk->ops;
341 
342 	if (ops->test_walk)
343 		return ops->test_walk(start, end, walk);
344 
345 	/*
346 	 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP
347 	 * range, so we don't walk over it as we do for normal vmas. However,
348 	 * Some callers are interested in handling hole range and they don't
349 	 * want to just ignore any single address range. Such users certainly
350 	 * define their ->pte_hole() callbacks, so let's delegate them to handle
351 	 * vma(VM_PFNMAP).
352 	 */
353 	if (vma->vm_flags & VM_PFNMAP) {
354 		int err = 1;
355 		if (ops->pte_hole)
356 			err = ops->pte_hole(start, end, -1, walk);
357 		return err ? err : 1;
358 	}
359 	return 0;
360 }
361 
__walk_page_range(unsigned long start,unsigned long end,struct mm_walk * walk)362 static int __walk_page_range(unsigned long start, unsigned long end,
363 			struct mm_walk *walk)
364 {
365 	int err = 0;
366 	struct vm_area_struct *vma = walk->vma;
367 	const struct mm_walk_ops *ops = walk->ops;
368 
369 	if (vma && ops->pre_vma) {
370 		err = ops->pre_vma(start, end, walk);
371 		if (err)
372 			return err;
373 	}
374 
375 	if (vma && is_vm_hugetlb_page(vma)) {
376 		if (ops->hugetlb_entry)
377 			err = walk_hugetlb_range(start, end, walk);
378 	} else
379 		err = walk_pgd_range(start, end, walk);
380 
381 	if (vma && ops->post_vma)
382 		ops->post_vma(walk);
383 
384 	return err;
385 }
386 
387 /**
388  * walk_page_range - walk page table with caller specific callbacks
389  * @mm:		mm_struct representing the target process of page table walk
390  * @start:	start address of the virtual address range
391  * @end:	end address of the virtual address range
392  * @ops:	operation to call during the walk
393  * @private:	private data for callbacks' usage
394  *
395  * Recursively walk the page table tree of the process represented by @mm
396  * within the virtual address range [@start, @end). During walking, we can do
397  * some caller-specific works for each entry, by setting up pmd_entry(),
398  * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these
399  * callbacks, the associated entries/pages are just ignored.
400  * The return values of these callbacks are commonly defined like below:
401  *
402  *  - 0  : succeeded to handle the current entry, and if you don't reach the
403  *         end address yet, continue to walk.
404  *  - >0 : succeeded to handle the current entry, and return to the caller
405  *         with caller specific value.
406  *  - <0 : failed to handle the current entry, and return to the caller
407  *         with error code.
408  *
409  * Before starting to walk page table, some callers want to check whether
410  * they really want to walk over the current vma, typically by checking
411  * its vm_flags. walk_page_test() and @ops->test_walk() are used for this
412  * purpose.
413  *
414  * If operations need to be staged before and committed after a vma is walked,
415  * there are two callbacks, pre_vma() and post_vma(). Note that post_vma(),
416  * since it is intended to handle commit-type operations, can't return any
417  * errors.
418  *
419  * struct mm_walk keeps current values of some common data like vma and pmd,
420  * which are useful for the access from callbacks. If you want to pass some
421  * caller-specific data to callbacks, @private should be helpful.
422  *
423  * Locking:
424  *   Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock,
425  *   because these function traverse vma list and/or access to vma's data.
426  */
walk_page_range(struct mm_struct * mm,unsigned long start,unsigned long end,const struct mm_walk_ops * ops,void * private)427 int walk_page_range(struct mm_struct *mm, unsigned long start,
428 		unsigned long end, const struct mm_walk_ops *ops,
429 		void *private)
430 {
431 	int err = 0;
432 	unsigned long next;
433 	struct vm_area_struct *vma;
434 	struct mm_walk walk = {
435 		.ops		= ops,
436 		.mm		= mm,
437 		.private	= private,
438 	};
439 
440 	if (start >= end)
441 		return -EINVAL;
442 
443 	if (!walk.mm)
444 		return -EINVAL;
445 
446 	mmap_assert_locked(walk.mm);
447 
448 	vma = find_vma(walk.mm, start);
449 	do {
450 		if (!vma) { /* after the last vma */
451 			walk.vma = NULL;
452 			next = end;
453 		} else if (start < vma->vm_start) { /* outside vma */
454 			walk.vma = NULL;
455 			next = min(end, vma->vm_start);
456 		} else { /* inside vma */
457 			walk.vma = vma;
458 			next = min(end, vma->vm_end);
459 			vma = vma->vm_next;
460 
461 			err = walk_page_test(start, next, &walk);
462 			if (err > 0) {
463 				/*
464 				 * positive return values are purely for
465 				 * controlling the pagewalk, so should never
466 				 * be passed to the callers.
467 				 */
468 				err = 0;
469 				continue;
470 			}
471 			if (err < 0)
472 				break;
473 		}
474 		if (walk.vma || walk.ops->pte_hole)
475 			err = __walk_page_range(start, next, &walk);
476 		if (err)
477 			break;
478 	} while (start = next, start < end);
479 	return err;
480 }
481 
482 /*
483  * Similar to walk_page_range() but can walk any page tables even if they are
484  * not backed by VMAs. Because 'unusual' entries may be walked this function
485  * will also not lock the PTEs for the pte_entry() callback. This is useful for
486  * walking the kernel pages tables or page tables for firmware.
487  */
walk_page_range_novma(struct mm_struct * mm,unsigned long start,unsigned long end,const struct mm_walk_ops * ops,pgd_t * pgd,void * private)488 int walk_page_range_novma(struct mm_struct *mm, unsigned long start,
489 			  unsigned long end, const struct mm_walk_ops *ops,
490 			  pgd_t *pgd,
491 			  void *private)
492 {
493 	struct mm_walk walk = {
494 		.ops		= ops,
495 		.mm		= mm,
496 		.pgd		= pgd,
497 		.private	= private,
498 		.no_vma		= true
499 	};
500 
501 	if (start >= end || !walk.mm)
502 		return -EINVAL;
503 
504 	mmap_assert_locked(walk.mm);
505 
506 	return __walk_page_range(start, end, &walk);
507 }
508 
walk_page_vma(struct vm_area_struct * vma,const struct mm_walk_ops * ops,void * private)509 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
510 		void *private)
511 {
512 	struct mm_walk walk = {
513 		.ops		= ops,
514 		.mm		= vma->vm_mm,
515 		.vma		= vma,
516 		.private	= private,
517 	};
518 	int err;
519 
520 	if (!walk.mm)
521 		return -EINVAL;
522 
523 	mmap_assert_locked(walk.mm);
524 
525 	err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
526 	if (err > 0)
527 		return 0;
528 	if (err < 0)
529 		return err;
530 	return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
531 }
532 
533 /**
534  * walk_page_mapping - walk all memory areas mapped into a struct address_space.
535  * @mapping: Pointer to the struct address_space
536  * @first_index: First page offset in the address_space
537  * @nr: Number of incremental page offsets to cover
538  * @ops:	operation to call during the walk
539  * @private:	private data for callbacks' usage
540  *
541  * This function walks all memory areas mapped into a struct address_space.
542  * The walk is limited to only the given page-size index range, but if
543  * the index boundaries cross a huge page-table entry, that entry will be
544  * included.
545  *
546  * Also see walk_page_range() for additional information.
547  *
548  * Locking:
549  *   This function can't require that the struct mm_struct::mmap_lock is held,
550  *   since @mapping may be mapped by multiple processes. Instead
551  *   @mapping->i_mmap_rwsem must be held. This might have implications in the
552  *   callbacks, and it's up tho the caller to ensure that the
553  *   struct mm_struct::mmap_lock is not needed.
554  *
555  *   Also this means that a caller can't rely on the struct
556  *   vm_area_struct::vm_flags to be constant across a call,
557  *   except for immutable flags. Callers requiring this shouldn't use
558  *   this function.
559  *
560  * Return: 0 on success, negative error code on failure, positive number on
561  * caller defined premature termination.
562  */
walk_page_mapping(struct address_space * mapping,pgoff_t first_index,pgoff_t nr,const struct mm_walk_ops * ops,void * private)563 int walk_page_mapping(struct address_space *mapping, pgoff_t first_index,
564 		      pgoff_t nr, const struct mm_walk_ops *ops,
565 		      void *private)
566 {
567 	struct mm_walk walk = {
568 		.ops		= ops,
569 		.private	= private,
570 	};
571 	struct vm_area_struct *vma;
572 	pgoff_t vba, vea, cba, cea;
573 	unsigned long start_addr, end_addr;
574 	int err = 0;
575 
576 	lockdep_assert_held(&mapping->i_mmap_rwsem);
577 	vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index,
578 				  first_index + nr - 1) {
579 		/* Clip to the vma */
580 		vba = vma->vm_pgoff;
581 		vea = vba + vma_pages(vma);
582 		cba = first_index;
583 		cba = max(cba, vba);
584 		cea = first_index + nr;
585 		cea = min(cea, vea);
586 
587 		start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start;
588 		end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start;
589 		if (start_addr >= end_addr)
590 			continue;
591 
592 		walk.vma = vma;
593 		walk.mm = vma->vm_mm;
594 
595 		err = walk_page_test(vma->vm_start, vma->vm_end, &walk);
596 		if (err > 0) {
597 			err = 0;
598 			break;
599 		} else if (err < 0)
600 			break;
601 
602 		err = __walk_page_range(start_addr, end_addr, &walk);
603 		if (err)
604 			break;
605 	}
606 
607 	return err;
608 }
609