xref: /openbmc/linux/mm/kasan/init.c (revision 44900c3e) 
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 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
143 				unsigned long end)
144 {
145 	pud_t *pud = pud_offset(p4d, addr);
146 	unsigned long next;
147 
148 	do {
149 		next = pud_addr_end(addr, end);
150 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
151 			pmd_t *pmd;
152 
153 			pud_populate(&init_mm, pud,
154 					lm_alias(kasan_early_shadow_pmd));
155 			pmd = pmd_offset(pud, addr);
156 			pmd_populate_kernel(&init_mm, pmd,
157 					lm_alias(kasan_early_shadow_pte));
158 			continue;
159 		}
160 
161 		if (pud_none(*pud)) {
162 			pmd_t *p;
163 
164 			if (slab_is_available()) {
165 				p = pmd_alloc(&init_mm, pud, addr);
166 				if (!p)
167 					return -ENOMEM;
168 			} else {
169 				pud_populate(&init_mm, pud,
170 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
171 			}
172 		}
173 		zero_pmd_populate(pud, addr, next);
174 	} while (pud++, addr = next, addr != end);
175 
176 	return 0;
177 }
178 
179 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
180 				unsigned long end)
181 {
182 	p4d_t *p4d = p4d_offset(pgd, addr);
183 	unsigned long next;
184 
185 	do {
186 		next = p4d_addr_end(addr, end);
187 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
188 			pud_t *pud;
189 			pmd_t *pmd;
190 
191 			p4d_populate(&init_mm, p4d,
192 					lm_alias(kasan_early_shadow_pud));
193 			pud = pud_offset(p4d, addr);
194 			pud_populate(&init_mm, pud,
195 					lm_alias(kasan_early_shadow_pmd));
196 			pmd = pmd_offset(pud, addr);
197 			pmd_populate_kernel(&init_mm, pmd,
198 					lm_alias(kasan_early_shadow_pte));
199 			continue;
200 		}
201 
202 		if (p4d_none(*p4d)) {
203 			pud_t *p;
204 
205 			if (slab_is_available()) {
206 				p = pud_alloc(&init_mm, p4d, addr);
207 				if (!p)
208 					return -ENOMEM;
209 			} else {
210 				p4d_populate(&init_mm, p4d,
211 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
212 			}
213 		}
214 		zero_pud_populate(p4d, addr, next);
215 	} while (p4d++, addr = next, addr != end);
216 
217 	return 0;
218 }
219 
220 /**
221  * kasan_populate_early_shadow - populate shadow memory region with
222  *                               kasan_early_shadow_page
223  * @shadow_start: start of the memory range to populate
224  * @shadow_end: end of the memory range to populate
225  */
226 int __ref kasan_populate_early_shadow(const void *shadow_start,
227 					const void *shadow_end)
228 {
229 	unsigned long addr = (unsigned long)shadow_start;
230 	unsigned long end = (unsigned long)shadow_end;
231 	pgd_t *pgd = pgd_offset_k(addr);
232 	unsigned long next;
233 
234 	do {
235 		next = pgd_addr_end(addr, end);
236 
237 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
238 			p4d_t *p4d;
239 			pud_t *pud;
240 			pmd_t *pmd;
241 
242 			/*
243 			 * kasan_early_shadow_pud should be populated with pmds
244 			 * at this moment.
245 			 * [pud,pmd]_populate*() below needed only for
246 			 * 3,2 - level page tables where we don't have
247 			 * puds,pmds, so pgd_populate(), pud_populate()
248 			 * is noops.
249 			 */
250 			pgd_populate(&init_mm, pgd,
251 					lm_alias(kasan_early_shadow_p4d));
252 			p4d = p4d_offset(pgd, addr);
253 			p4d_populate(&init_mm, p4d,
254 					lm_alias(kasan_early_shadow_pud));
255 			pud = pud_offset(p4d, addr);
256 			pud_populate(&init_mm, pud,
257 					lm_alias(kasan_early_shadow_pmd));
258 			pmd = pmd_offset(pud, addr);
259 			pmd_populate_kernel(&init_mm, pmd,
260 					lm_alias(kasan_early_shadow_pte));
261 			continue;
262 		}
263 
264 		if (pgd_none(*pgd)) {
265 			p4d_t *p;
266 
267 			if (slab_is_available()) {
268 				p = p4d_alloc(&init_mm, pgd, addr);
269 				if (!p)
270 					return -ENOMEM;
271 			} else {
272 				pgd_populate(&init_mm, pgd,
273 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
274 			}
275 		}
276 		zero_p4d_populate(pgd, addr, next);
277 	} while (pgd++, addr = next, addr != end);
278 
279 	return 0;
280 }
281 
282 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
283 {
284 	pte_t *pte;
285 	int i;
286 
287 	for (i = 0; i < PTRS_PER_PTE; i++) {
288 		pte = pte_start + i;
289 		if (!pte_none(ptep_get(pte)))
290 			return;
291 	}
292 
293 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
294 	pmd_clear(pmd);
295 }
296 
297 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
298 {
299 	pmd_t *pmd;
300 	int i;
301 
302 	for (i = 0; i < PTRS_PER_PMD; i++) {
303 		pmd = pmd_start + i;
304 		if (!pmd_none(*pmd))
305 			return;
306 	}
307 
308 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
309 	pud_clear(pud);
310 }
311 
312 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
313 {
314 	pud_t *pud;
315 	int i;
316 
317 	for (i = 0; i < PTRS_PER_PUD; i++) {
318 		pud = pud_start + i;
319 		if (!pud_none(*pud))
320 			return;
321 	}
322 
323 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
324 	p4d_clear(p4d);
325 }
326 
327 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
328 {
329 	p4d_t *p4d;
330 	int i;
331 
332 	for (i = 0; i < PTRS_PER_P4D; i++) {
333 		p4d = p4d_start + i;
334 		if (!p4d_none(*p4d))
335 			return;
336 	}
337 
338 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
339 	pgd_clear(pgd);
340 }
341 
342 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
343 				unsigned long end)
344 {
345 	unsigned long next;
346 	pte_t ptent;
347 
348 	for (; addr < end; addr = next, pte++) {
349 		next = (addr + PAGE_SIZE) & PAGE_MASK;
350 		if (next > end)
351 			next = end;
352 
353 		ptent = ptep_get(pte);
354 
355 		if (!pte_present(ptent))
356 			continue;
357 
358 		if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
359 			continue;
360 		pte_clear(&init_mm, addr, pte);
361 	}
362 }
363 
364 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
365 				unsigned long end)
366 {
367 	unsigned long next;
368 
369 	for (; addr < end; addr = next, pmd++) {
370 		pte_t *pte;
371 
372 		next = pmd_addr_end(addr, end);
373 
374 		if (!pmd_present(*pmd))
375 			continue;
376 
377 		if (kasan_pte_table(*pmd)) {
378 			if (IS_ALIGNED(addr, PMD_SIZE) &&
379 			    IS_ALIGNED(next, PMD_SIZE)) {
380 				pmd_clear(pmd);
381 				continue;
382 			}
383 		}
384 		pte = pte_offset_kernel(pmd, addr);
385 		kasan_remove_pte_table(pte, addr, next);
386 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
387 	}
388 }
389 
390 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
391 				unsigned long end)
392 {
393 	unsigned long next;
394 
395 	for (; addr < end; addr = next, pud++) {
396 		pmd_t *pmd, *pmd_base;
397 
398 		next = pud_addr_end(addr, end);
399 
400 		if (!pud_present(*pud))
401 			continue;
402 
403 		if (kasan_pmd_table(*pud)) {
404 			if (IS_ALIGNED(addr, PUD_SIZE) &&
405 			    IS_ALIGNED(next, PUD_SIZE)) {
406 				pud_clear(pud);
407 				continue;
408 			}
409 		}
410 		pmd = pmd_offset(pud, addr);
411 		pmd_base = pmd_offset(pud, 0);
412 		kasan_remove_pmd_table(pmd, addr, next);
413 		kasan_free_pmd(pmd_base, pud);
414 	}
415 }
416 
417 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
418 				unsigned long end)
419 {
420 	unsigned long next;
421 
422 	for (; addr < end; addr = next, p4d++) {
423 		pud_t *pud;
424 
425 		next = p4d_addr_end(addr, end);
426 
427 		if (!p4d_present(*p4d))
428 			continue;
429 
430 		if (kasan_pud_table(*p4d)) {
431 			if (IS_ALIGNED(addr, P4D_SIZE) &&
432 			    IS_ALIGNED(next, P4D_SIZE)) {
433 				p4d_clear(p4d);
434 				continue;
435 			}
436 		}
437 		pud = pud_offset(p4d, addr);
438 		kasan_remove_pud_table(pud, addr, next);
439 		kasan_free_pud(pud_offset(p4d, 0), p4d);
440 	}
441 }
442 
443 void kasan_remove_zero_shadow(void *start, unsigned long size)
444 {
445 	unsigned long addr, end, next;
446 	pgd_t *pgd;
447 
448 	addr = (unsigned long)kasan_mem_to_shadow(start);
449 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
450 
451 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
452 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
453 		return;
454 
455 	for (; addr < end; addr = next) {
456 		p4d_t *p4d;
457 
458 		next = pgd_addr_end(addr, end);
459 
460 		pgd = pgd_offset_k(addr);
461 		if (!pgd_present(*pgd))
462 			continue;
463 
464 		if (kasan_p4d_table(*pgd)) {
465 			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
466 			    IS_ALIGNED(next, PGDIR_SIZE)) {
467 				pgd_clear(pgd);
468 				continue;
469 			}
470 		}
471 
472 		p4d = p4d_offset(pgd, addr);
473 		kasan_remove_p4d_table(p4d, addr, next);
474 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
475 	}
476 }
477 
478 int kasan_add_zero_shadow(void *start, unsigned long size)
479 {
480 	int ret;
481 	void *shadow_start, *shadow_end;
482 
483 	shadow_start = kasan_mem_to_shadow(start);
484 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
485 
486 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
487 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
488 		return -EINVAL;
489 
490 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
491 	if (ret)
492 		kasan_remove_zero_shadow(start, size);
493 	return ret;
494 }
495