xref: /openbmc/linux/mm/kasan/init.c (revision f2a55d08) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * This file contains KASAN shadow initialization code.
4  *
5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7  */
8 
9 #include <linux/memblock.h>
10 #include <linux/init.h>
11 #include <linux/kasan.h>
12 #include <linux/kernel.h>
13 #include <linux/mm.h>
14 #include <linux/pfn.h>
15 #include <linux/slab.h>
16 
17 #include <asm/page.h>
18 #include <asm/pgalloc.h>
19 
20 #include "kasan.h"
21 
22 /*
23  * This page serves two purposes:
24  *   - It used as early shadow memory. The entire shadow region populated
25  *     with this page, before we will be able to setup normal shadow memory.
26  *   - Latter it reused it as zero shadow to cover large ranges of memory
27  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
28  */
29 unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
30 
31 #if CONFIG_PGTABLE_LEVELS > 4
32 p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
33 static inline bool kasan_p4d_table(pgd_t pgd)
34 {
35 	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
36 }
37 #else
38 static inline bool kasan_p4d_table(pgd_t pgd)
39 {
40 	return false;
41 }
42 #endif
43 #if CONFIG_PGTABLE_LEVELS > 3
44 pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
45 static inline bool kasan_pud_table(p4d_t p4d)
46 {
47 	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
48 }
49 #else
50 static inline bool kasan_pud_table(p4d_t p4d)
51 {
52 	return false;
53 }
54 #endif
55 #if CONFIG_PGTABLE_LEVELS > 2
56 pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
57 static inline bool kasan_pmd_table(pud_t pud)
58 {
59 	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
60 }
61 #else
62 static inline bool kasan_pmd_table(pud_t pud)
63 {
64 	return false;
65 }
66 #endif
67 pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
68 	__page_aligned_bss;
69 
70 static inline bool kasan_pte_table(pmd_t pmd)
71 {
72 	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
73 }
74 
75 static inline bool kasan_early_shadow_page_entry(pte_t pte)
76 {
77 	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
78 }
79 
80 static __init void *early_alloc(size_t size, int node)
81 {
82 	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
83 					   MEMBLOCK_ALLOC_ACCESSIBLE, node);
84 
85 	if (!ptr)
86 		panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
87 		      __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
88 
89 	return ptr;
90 }
91 
92 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
93 				unsigned long end)
94 {
95 	pte_t *pte = pte_offset_kernel(pmd, addr);
96 	pte_t zero_pte;
97 
98 	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
99 				PAGE_KERNEL);
100 	zero_pte = pte_wrprotect(zero_pte);
101 
102 	while (addr + PAGE_SIZE <= end) {
103 		set_pte_at(&init_mm, addr, pte, zero_pte);
104 		addr += PAGE_SIZE;
105 		pte = pte_offset_kernel(pmd, addr);
106 	}
107 }
108 
109 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
110 				unsigned long end)
111 {
112 	pmd_t *pmd = pmd_offset(pud, addr);
113 	unsigned long next;
114 
115 	do {
116 		next = pmd_addr_end(addr, end);
117 
118 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
119 			pmd_populate_kernel(&init_mm, pmd,
120 					lm_alias(kasan_early_shadow_pte));
121 			continue;
122 		}
123 
124 		if (pmd_none(*pmd)) {
125 			pte_t *p;
126 
127 			if (slab_is_available())
128 				p = pte_alloc_one_kernel(&init_mm);
129 			else
130 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
131 			if (!p)
132 				return -ENOMEM;
133 
134 			pmd_populate_kernel(&init_mm, pmd, p);
135 		}
136 		zero_pte_populate(pmd, addr, next);
137 	} while (pmd++, addr = next, addr != end);
138 
139 	return 0;
140 }
141 
142 void __weak __meminit pmd_init(void *addr)
143 {
144 }
145 
146 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
147 				unsigned long end)
148 {
149 	pud_t *pud = pud_offset(p4d, addr);
150 	unsigned long next;
151 
152 	do {
153 		next = pud_addr_end(addr, end);
154 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
155 			pmd_t *pmd;
156 
157 			pud_populate(&init_mm, pud,
158 					lm_alias(kasan_early_shadow_pmd));
159 			pmd = pmd_offset(pud, addr);
160 			pmd_populate_kernel(&init_mm, pmd,
161 					lm_alias(kasan_early_shadow_pte));
162 			continue;
163 		}
164 
165 		if (pud_none(*pud)) {
166 			pmd_t *p;
167 
168 			if (slab_is_available()) {
169 				p = pmd_alloc(&init_mm, pud, addr);
170 				if (!p)
171 					return -ENOMEM;
172 			} else {
173 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
174 				pmd_init(p);
175 				pud_populate(&init_mm, pud, p);
176 			}
177 		}
178 		zero_pmd_populate(pud, addr, next);
179 	} while (pud++, addr = next, addr != end);
180 
181 	return 0;
182 }
183 
184 void __weak __meminit pud_init(void *addr)
185 {
186 }
187 
188 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
189 				unsigned long end)
190 {
191 	p4d_t *p4d = p4d_offset(pgd, addr);
192 	unsigned long next;
193 
194 	do {
195 		next = p4d_addr_end(addr, end);
196 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
197 			pud_t *pud;
198 			pmd_t *pmd;
199 
200 			p4d_populate(&init_mm, p4d,
201 					lm_alias(kasan_early_shadow_pud));
202 			pud = pud_offset(p4d, addr);
203 			pud_populate(&init_mm, pud,
204 					lm_alias(kasan_early_shadow_pmd));
205 			pmd = pmd_offset(pud, addr);
206 			pmd_populate_kernel(&init_mm, pmd,
207 					lm_alias(kasan_early_shadow_pte));
208 			continue;
209 		}
210 
211 		if (p4d_none(*p4d)) {
212 			pud_t *p;
213 
214 			if (slab_is_available()) {
215 				p = pud_alloc(&init_mm, p4d, addr);
216 				if (!p)
217 					return -ENOMEM;
218 			} else {
219 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
220 				pud_init(p);
221 				p4d_populate(&init_mm, p4d, p);
222 			}
223 		}
224 		zero_pud_populate(p4d, addr, next);
225 	} while (p4d++, addr = next, addr != end);
226 
227 	return 0;
228 }
229 
230 /**
231  * kasan_populate_early_shadow - populate shadow memory region with
232  *                               kasan_early_shadow_page
233  * @shadow_start: start of the memory range to populate
234  * @shadow_end: end of the memory range to populate
235  */
236 int __ref kasan_populate_early_shadow(const void *shadow_start,
237 					const void *shadow_end)
238 {
239 	unsigned long addr = (unsigned long)shadow_start;
240 	unsigned long end = (unsigned long)shadow_end;
241 	pgd_t *pgd = pgd_offset_k(addr);
242 	unsigned long next;
243 
244 	do {
245 		next = pgd_addr_end(addr, end);
246 
247 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
248 			p4d_t *p4d;
249 			pud_t *pud;
250 			pmd_t *pmd;
251 
252 			/*
253 			 * kasan_early_shadow_pud should be populated with pmds
254 			 * at this moment.
255 			 * [pud,pmd]_populate*() below needed only for
256 			 * 3,2 - level page tables where we don't have
257 			 * puds,pmds, so pgd_populate(), pud_populate()
258 			 * is noops.
259 			 */
260 			pgd_populate(&init_mm, pgd,
261 					lm_alias(kasan_early_shadow_p4d));
262 			p4d = p4d_offset(pgd, addr);
263 			p4d_populate(&init_mm, p4d,
264 					lm_alias(kasan_early_shadow_pud));
265 			pud = pud_offset(p4d, addr);
266 			pud_populate(&init_mm, pud,
267 					lm_alias(kasan_early_shadow_pmd));
268 			pmd = pmd_offset(pud, addr);
269 			pmd_populate_kernel(&init_mm, pmd,
270 					lm_alias(kasan_early_shadow_pte));
271 			continue;
272 		}
273 
274 		if (pgd_none(*pgd)) {
275 			p4d_t *p;
276 
277 			if (slab_is_available()) {
278 				p = p4d_alloc(&init_mm, pgd, addr);
279 				if (!p)
280 					return -ENOMEM;
281 			} else {
282 				pgd_populate(&init_mm, pgd,
283 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
284 			}
285 		}
286 		zero_p4d_populate(pgd, addr, next);
287 	} while (pgd++, addr = next, addr != end);
288 
289 	return 0;
290 }
291 
292 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
293 {
294 	pte_t *pte;
295 	int i;
296 
297 	for (i = 0; i < PTRS_PER_PTE; i++) {
298 		pte = pte_start + i;
299 		if (!pte_none(ptep_get(pte)))
300 			return;
301 	}
302 
303 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
304 	pmd_clear(pmd);
305 }
306 
307 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
308 {
309 	pmd_t *pmd;
310 	int i;
311 
312 	for (i = 0; i < PTRS_PER_PMD; i++) {
313 		pmd = pmd_start + i;
314 		if (!pmd_none(*pmd))
315 			return;
316 	}
317 
318 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
319 	pud_clear(pud);
320 }
321 
322 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
323 {
324 	pud_t *pud;
325 	int i;
326 
327 	for (i = 0; i < PTRS_PER_PUD; i++) {
328 		pud = pud_start + i;
329 		if (!pud_none(*pud))
330 			return;
331 	}
332 
333 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
334 	p4d_clear(p4d);
335 }
336 
337 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
338 {
339 	p4d_t *p4d;
340 	int i;
341 
342 	for (i = 0; i < PTRS_PER_P4D; i++) {
343 		p4d = p4d_start + i;
344 		if (!p4d_none(*p4d))
345 			return;
346 	}
347 
348 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
349 	pgd_clear(pgd);
350 }
351 
352 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
353 				unsigned long end)
354 {
355 	unsigned long next;
356 	pte_t ptent;
357 
358 	for (; addr < end; addr = next, pte++) {
359 		next = (addr + PAGE_SIZE) & PAGE_MASK;
360 		if (next > end)
361 			next = end;
362 
363 		ptent = ptep_get(pte);
364 
365 		if (!pte_present(ptent))
366 			continue;
367 
368 		if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
369 			continue;
370 		pte_clear(&init_mm, addr, pte);
371 	}
372 }
373 
374 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
375 				unsigned long end)
376 {
377 	unsigned long next;
378 
379 	for (; addr < end; addr = next, pmd++) {
380 		pte_t *pte;
381 
382 		next = pmd_addr_end(addr, end);
383 
384 		if (!pmd_present(*pmd))
385 			continue;
386 
387 		if (kasan_pte_table(*pmd)) {
388 			if (IS_ALIGNED(addr, PMD_SIZE) &&
389 			    IS_ALIGNED(next, PMD_SIZE)) {
390 				pmd_clear(pmd);
391 				continue;
392 			}
393 		}
394 		pte = pte_offset_kernel(pmd, addr);
395 		kasan_remove_pte_table(pte, addr, next);
396 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
397 	}
398 }
399 
400 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
401 				unsigned long end)
402 {
403 	unsigned long next;
404 
405 	for (; addr < end; addr = next, pud++) {
406 		pmd_t *pmd, *pmd_base;
407 
408 		next = pud_addr_end(addr, end);
409 
410 		if (!pud_present(*pud))
411 			continue;
412 
413 		if (kasan_pmd_table(*pud)) {
414 			if (IS_ALIGNED(addr, PUD_SIZE) &&
415 			    IS_ALIGNED(next, PUD_SIZE)) {
416 				pud_clear(pud);
417 				continue;
418 			}
419 		}
420 		pmd = pmd_offset(pud, addr);
421 		pmd_base = pmd_offset(pud, 0);
422 		kasan_remove_pmd_table(pmd, addr, next);
423 		kasan_free_pmd(pmd_base, pud);
424 	}
425 }
426 
427 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
428 				unsigned long end)
429 {
430 	unsigned long next;
431 
432 	for (; addr < end; addr = next, p4d++) {
433 		pud_t *pud;
434 
435 		next = p4d_addr_end(addr, end);
436 
437 		if (!p4d_present(*p4d))
438 			continue;
439 
440 		if (kasan_pud_table(*p4d)) {
441 			if (IS_ALIGNED(addr, P4D_SIZE) &&
442 			    IS_ALIGNED(next, P4D_SIZE)) {
443 				p4d_clear(p4d);
444 				continue;
445 			}
446 		}
447 		pud = pud_offset(p4d, addr);
448 		kasan_remove_pud_table(pud, addr, next);
449 		kasan_free_pud(pud_offset(p4d, 0), p4d);
450 	}
451 }
452 
453 void kasan_remove_zero_shadow(void *start, unsigned long size)
454 {
455 	unsigned long addr, end, next;
456 	pgd_t *pgd;
457 
458 	addr = (unsigned long)kasan_mem_to_shadow(start);
459 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
460 
461 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
462 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
463 		return;
464 
465 	for (; addr < end; addr = next) {
466 		p4d_t *p4d;
467 
468 		next = pgd_addr_end(addr, end);
469 
470 		pgd = pgd_offset_k(addr);
471 		if (!pgd_present(*pgd))
472 			continue;
473 
474 		if (kasan_p4d_table(*pgd)) {
475 			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
476 			    IS_ALIGNED(next, PGDIR_SIZE)) {
477 				pgd_clear(pgd);
478 				continue;
479 			}
480 		}
481 
482 		p4d = p4d_offset(pgd, addr);
483 		kasan_remove_p4d_table(p4d, addr, next);
484 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
485 	}
486 }
487 
488 int kasan_add_zero_shadow(void *start, unsigned long size)
489 {
490 	int ret;
491 	void *shadow_start, *shadow_end;
492 
493 	shadow_start = kasan_mem_to_shadow(start);
494 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
495 
496 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
497 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
498 		return -EINVAL;
499 
500 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
501 	if (ret)
502 		kasan_remove_zero_shadow(start, size);
503 	return ret;
504 }
505