xref: /openbmc/linux/mm/kasan/init.c (revision d0e22329) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * This file contains some kasan initialization code.
4  *
5  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
6  * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  *
12  */
13 
14 #include <linux/memblock.h>
15 #include <linux/init.h>
16 #include <linux/kasan.h>
17 #include <linux/kernel.h>
18 #include <linux/mm.h>
19 #include <linux/pfn.h>
20 #include <linux/slab.h>
21 
22 #include <asm/page.h>
23 #include <asm/pgalloc.h>
24 
25 #include "kasan.h"
26 
27 /*
28  * This page serves two purposes:
29  *   - It used as early shadow memory. The entire shadow region populated
30  *     with this page, before we will be able to setup normal shadow memory.
31  *   - Latter it reused it as zero shadow to cover large ranges of memory
32  *     that allowed to access, but not handled by kasan (vmalloc/vmemmap ...).
33  */
34 unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
35 
36 #if CONFIG_PGTABLE_LEVELS > 4
37 p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
38 static inline bool kasan_p4d_table(pgd_t pgd)
39 {
40 	return pgd_page(pgd) == virt_to_page(lm_alias(kasan_early_shadow_p4d));
41 }
42 #else
43 static inline bool kasan_p4d_table(pgd_t pgd)
44 {
45 	return 0;
46 }
47 #endif
48 #if CONFIG_PGTABLE_LEVELS > 3
49 pud_t kasan_early_shadow_pud[PTRS_PER_PUD] __page_aligned_bss;
50 static inline bool kasan_pud_table(p4d_t p4d)
51 {
52 	return p4d_page(p4d) == virt_to_page(lm_alias(kasan_early_shadow_pud));
53 }
54 #else
55 static inline bool kasan_pud_table(p4d_t p4d)
56 {
57 	return 0;
58 }
59 #endif
60 #if CONFIG_PGTABLE_LEVELS > 2
61 pmd_t kasan_early_shadow_pmd[PTRS_PER_PMD] __page_aligned_bss;
62 static inline bool kasan_pmd_table(pud_t pud)
63 {
64 	return pud_page(pud) == virt_to_page(lm_alias(kasan_early_shadow_pmd));
65 }
66 #else
67 static inline bool kasan_pmd_table(pud_t pud)
68 {
69 	return 0;
70 }
71 #endif
72 pte_t kasan_early_shadow_pte[PTRS_PER_PTE] __page_aligned_bss;
73 
74 static inline bool kasan_pte_table(pmd_t pmd)
75 {
76 	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
77 }
78 
79 static inline bool kasan_early_shadow_page_entry(pte_t pte)
80 {
81 	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
82 }
83 
84 static __init void *early_alloc(size_t size, int node)
85 {
86 	return memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
87 					MEMBLOCK_ALLOC_ACCESSIBLE, node);
88 }
89 
90 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
91 				unsigned long end)
92 {
93 	pte_t *pte = pte_offset_kernel(pmd, addr);
94 	pte_t zero_pte;
95 
96 	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
97 				PAGE_KERNEL);
98 	zero_pte = pte_wrprotect(zero_pte);
99 
100 	while (addr + PAGE_SIZE <= end) {
101 		set_pte_at(&init_mm, addr, pte, zero_pte);
102 		addr += PAGE_SIZE;
103 		pte = pte_offset_kernel(pmd, addr);
104 	}
105 }
106 
107 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
108 				unsigned long end)
109 {
110 	pmd_t *pmd = pmd_offset(pud, addr);
111 	unsigned long next;
112 
113 	do {
114 		next = pmd_addr_end(addr, end);
115 
116 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
117 			pmd_populate_kernel(&init_mm, pmd,
118 					lm_alias(kasan_early_shadow_pte));
119 			continue;
120 		}
121 
122 		if (pmd_none(*pmd)) {
123 			pte_t *p;
124 
125 			if (slab_is_available())
126 				p = pte_alloc_one_kernel(&init_mm);
127 			else
128 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
129 			if (!p)
130 				return -ENOMEM;
131 
132 			pmd_populate_kernel(&init_mm, pmd, p);
133 		}
134 		zero_pte_populate(pmd, addr, next);
135 	} while (pmd++, addr = next, addr != end);
136 
137 	return 0;
138 }
139 
140 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
141 				unsigned long end)
142 {
143 	pud_t *pud = pud_offset(p4d, addr);
144 	unsigned long next;
145 
146 	do {
147 		next = pud_addr_end(addr, end);
148 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
149 			pmd_t *pmd;
150 
151 			pud_populate(&init_mm, pud,
152 					lm_alias(kasan_early_shadow_pmd));
153 			pmd = pmd_offset(pud, addr);
154 			pmd_populate_kernel(&init_mm, pmd,
155 					lm_alias(kasan_early_shadow_pte));
156 			continue;
157 		}
158 
159 		if (pud_none(*pud)) {
160 			pmd_t *p;
161 
162 			if (slab_is_available()) {
163 				p = pmd_alloc(&init_mm, pud, addr);
164 				if (!p)
165 					return -ENOMEM;
166 			} else {
167 				pud_populate(&init_mm, pud,
168 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
169 			}
170 		}
171 		zero_pmd_populate(pud, addr, next);
172 	} while (pud++, addr = next, addr != end);
173 
174 	return 0;
175 }
176 
177 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
178 				unsigned long end)
179 {
180 	p4d_t *p4d = p4d_offset(pgd, addr);
181 	unsigned long next;
182 
183 	do {
184 		next = p4d_addr_end(addr, end);
185 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
186 			pud_t *pud;
187 			pmd_t *pmd;
188 
189 			p4d_populate(&init_mm, p4d,
190 					lm_alias(kasan_early_shadow_pud));
191 			pud = pud_offset(p4d, addr);
192 			pud_populate(&init_mm, pud,
193 					lm_alias(kasan_early_shadow_pmd));
194 			pmd = pmd_offset(pud, addr);
195 			pmd_populate_kernel(&init_mm, pmd,
196 					lm_alias(kasan_early_shadow_pte));
197 			continue;
198 		}
199 
200 		if (p4d_none(*p4d)) {
201 			pud_t *p;
202 
203 			if (slab_is_available()) {
204 				p = pud_alloc(&init_mm, p4d, addr);
205 				if (!p)
206 					return -ENOMEM;
207 			} else {
208 				p4d_populate(&init_mm, p4d,
209 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
210 			}
211 		}
212 		zero_pud_populate(p4d, addr, next);
213 	} while (p4d++, addr = next, addr != end);
214 
215 	return 0;
216 }
217 
218 /**
219  * kasan_populate_early_shadow - populate shadow memory region with
220  *                               kasan_early_shadow_page
221  * @shadow_start - start of the memory range to populate
222  * @shadow_end   - end of the memory range to populate
223  */
224 int __ref kasan_populate_early_shadow(const void *shadow_start,
225 					const void *shadow_end)
226 {
227 	unsigned long addr = (unsigned long)shadow_start;
228 	unsigned long end = (unsigned long)shadow_end;
229 	pgd_t *pgd = pgd_offset_k(addr);
230 	unsigned long next;
231 
232 	do {
233 		next = pgd_addr_end(addr, end);
234 
235 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
236 			p4d_t *p4d;
237 			pud_t *pud;
238 			pmd_t *pmd;
239 
240 			/*
241 			 * kasan_early_shadow_pud should be populated with pmds
242 			 * at this moment.
243 			 * [pud,pmd]_populate*() below needed only for
244 			 * 3,2 - level page tables where we don't have
245 			 * puds,pmds, so pgd_populate(), pud_populate()
246 			 * is noops.
247 			 *
248 			 * The ifndef is required to avoid build breakage.
249 			 *
250 			 * With 5level-fixup.h, pgd_populate() is not nop and
251 			 * we reference kasan_early_shadow_p4d. It's not defined
252 			 * unless 5-level paging enabled.
253 			 *
254 			 * The ifndef can be dropped once all KASAN-enabled
255 			 * architectures will switch to pgtable-nop4d.h.
256 			 */
257 #ifndef __ARCH_HAS_5LEVEL_HACK
258 			pgd_populate(&init_mm, pgd,
259 					lm_alias(kasan_early_shadow_p4d));
260 #endif
261 			p4d = p4d_offset(pgd, addr);
262 			p4d_populate(&init_mm, p4d,
263 					lm_alias(kasan_early_shadow_pud));
264 			pud = pud_offset(p4d, addr);
265 			pud_populate(&init_mm, pud,
266 					lm_alias(kasan_early_shadow_pmd));
267 			pmd = pmd_offset(pud, addr);
268 			pmd_populate_kernel(&init_mm, pmd,
269 					lm_alias(kasan_early_shadow_pte));
270 			continue;
271 		}
272 
273 		if (pgd_none(*pgd)) {
274 			p4d_t *p;
275 
276 			if (slab_is_available()) {
277 				p = p4d_alloc(&init_mm, pgd, addr);
278 				if (!p)
279 					return -ENOMEM;
280 			} else {
281 				pgd_populate(&init_mm, pgd,
282 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
283 			}
284 		}
285 		zero_p4d_populate(pgd, addr, next);
286 	} while (pgd++, addr = next, addr != end);
287 
288 	return 0;
289 }
290 
291 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
292 {
293 	pte_t *pte;
294 	int i;
295 
296 	for (i = 0; i < PTRS_PER_PTE; i++) {
297 		pte = pte_start + i;
298 		if (!pte_none(*pte))
299 			return;
300 	}
301 
302 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
303 	pmd_clear(pmd);
304 }
305 
306 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
307 {
308 	pmd_t *pmd;
309 	int i;
310 
311 	for (i = 0; i < PTRS_PER_PMD; i++) {
312 		pmd = pmd_start + i;
313 		if (!pmd_none(*pmd))
314 			return;
315 	}
316 
317 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
318 	pud_clear(pud);
319 }
320 
321 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
322 {
323 	pud_t *pud;
324 	int i;
325 
326 	for (i = 0; i < PTRS_PER_PUD; i++) {
327 		pud = pud_start + i;
328 		if (!pud_none(*pud))
329 			return;
330 	}
331 
332 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
333 	p4d_clear(p4d);
334 }
335 
336 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
337 {
338 	p4d_t *p4d;
339 	int i;
340 
341 	for (i = 0; i < PTRS_PER_P4D; i++) {
342 		p4d = p4d_start + i;
343 		if (!p4d_none(*p4d))
344 			return;
345 	}
346 
347 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
348 	pgd_clear(pgd);
349 }
350 
351 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
352 				unsigned long end)
353 {
354 	unsigned long next;
355 
356 	for (; addr < end; addr = next, pte++) {
357 		next = (addr + PAGE_SIZE) & PAGE_MASK;
358 		if (next > end)
359 			next = end;
360 
361 		if (!pte_present(*pte))
362 			continue;
363 
364 		if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
365 			continue;
366 		pte_clear(&init_mm, addr, pte);
367 	}
368 }
369 
370 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
371 				unsigned long end)
372 {
373 	unsigned long next;
374 
375 	for (; addr < end; addr = next, pmd++) {
376 		pte_t *pte;
377 
378 		next = pmd_addr_end(addr, end);
379 
380 		if (!pmd_present(*pmd))
381 			continue;
382 
383 		if (kasan_pte_table(*pmd)) {
384 			if (IS_ALIGNED(addr, PMD_SIZE) &&
385 			    IS_ALIGNED(next, PMD_SIZE))
386 				pmd_clear(pmd);
387 			continue;
388 		}
389 		pte = pte_offset_kernel(pmd, addr);
390 		kasan_remove_pte_table(pte, addr, next);
391 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
392 	}
393 }
394 
395 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
396 				unsigned long end)
397 {
398 	unsigned long next;
399 
400 	for (; addr < end; addr = next, pud++) {
401 		pmd_t *pmd, *pmd_base;
402 
403 		next = pud_addr_end(addr, end);
404 
405 		if (!pud_present(*pud))
406 			continue;
407 
408 		if (kasan_pmd_table(*pud)) {
409 			if (IS_ALIGNED(addr, PUD_SIZE) &&
410 			    IS_ALIGNED(next, PUD_SIZE))
411 				pud_clear(pud);
412 			continue;
413 		}
414 		pmd = pmd_offset(pud, addr);
415 		pmd_base = pmd_offset(pud, 0);
416 		kasan_remove_pmd_table(pmd, addr, next);
417 		kasan_free_pmd(pmd_base, pud);
418 	}
419 }
420 
421 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
422 				unsigned long end)
423 {
424 	unsigned long next;
425 
426 	for (; addr < end; addr = next, p4d++) {
427 		pud_t *pud;
428 
429 		next = p4d_addr_end(addr, end);
430 
431 		if (!p4d_present(*p4d))
432 			continue;
433 
434 		if (kasan_pud_table(*p4d)) {
435 			if (IS_ALIGNED(addr, P4D_SIZE) &&
436 			    IS_ALIGNED(next, P4D_SIZE))
437 				p4d_clear(p4d);
438 			continue;
439 		}
440 		pud = pud_offset(p4d, addr);
441 		kasan_remove_pud_table(pud, addr, next);
442 		kasan_free_pud(pud_offset(p4d, 0), p4d);
443 	}
444 }
445 
446 void kasan_remove_zero_shadow(void *start, unsigned long size)
447 {
448 	unsigned long addr, end, next;
449 	pgd_t *pgd;
450 
451 	addr = (unsigned long)kasan_mem_to_shadow(start);
452 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
453 
454 	if (WARN_ON((unsigned long)start %
455 			(KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
456 	    WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
457 		return;
458 
459 	for (; addr < end; addr = next) {
460 		p4d_t *p4d;
461 
462 		next = pgd_addr_end(addr, end);
463 
464 		pgd = pgd_offset_k(addr);
465 		if (!pgd_present(*pgd))
466 			continue;
467 
468 		if (kasan_p4d_table(*pgd)) {
469 			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
470 			    IS_ALIGNED(next, PGDIR_SIZE))
471 				pgd_clear(pgd);
472 			continue;
473 		}
474 
475 		p4d = p4d_offset(pgd, addr);
476 		kasan_remove_p4d_table(p4d, addr, next);
477 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
478 	}
479 }
480 
481 int kasan_add_zero_shadow(void *start, unsigned long size)
482 {
483 	int ret;
484 	void *shadow_start, *shadow_end;
485 
486 	shadow_start = kasan_mem_to_shadow(start);
487 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
488 
489 	if (WARN_ON((unsigned long)start %
490 			(KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
491 	    WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
492 		return -EINVAL;
493 
494 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
495 	if (ret)
496 		kasan_remove_zero_shadow(shadow_start,
497 					size >> KASAN_SHADOW_SCALE_SHIFT);
498 	return ret;
499 }
500