xref: /openbmc/linux/mm/kasan/init.c (revision 7f877908) 
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 false;
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 false;
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 false;
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 	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
87 					   MEMBLOCK_ALLOC_ACCESSIBLE, node);
88 
89 	if (!ptr)
90 		panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
91 		      __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
92 
93 	return ptr;
94 }
95 
96 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
97 				unsigned long end)
98 {
99 	pte_t *pte = pte_offset_kernel(pmd, addr);
100 	pte_t zero_pte;
101 
102 	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
103 				PAGE_KERNEL);
104 	zero_pte = pte_wrprotect(zero_pte);
105 
106 	while (addr + PAGE_SIZE <= end) {
107 		set_pte_at(&init_mm, addr, pte, zero_pte);
108 		addr += PAGE_SIZE;
109 		pte = pte_offset_kernel(pmd, addr);
110 	}
111 }
112 
113 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
114 				unsigned long end)
115 {
116 	pmd_t *pmd = pmd_offset(pud, addr);
117 	unsigned long next;
118 
119 	do {
120 		next = pmd_addr_end(addr, end);
121 
122 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
123 			pmd_populate_kernel(&init_mm, pmd,
124 					lm_alias(kasan_early_shadow_pte));
125 			continue;
126 		}
127 
128 		if (pmd_none(*pmd)) {
129 			pte_t *p;
130 
131 			if (slab_is_available())
132 				p = pte_alloc_one_kernel(&init_mm);
133 			else
134 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
135 			if (!p)
136 				return -ENOMEM;
137 
138 			pmd_populate_kernel(&init_mm, pmd, p);
139 		}
140 		zero_pte_populate(pmd, addr, next);
141 	} while (pmd++, addr = next, addr != end);
142 
143 	return 0;
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 				pud_populate(&init_mm, pud,
174 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
175 			}
176 		}
177 		zero_pmd_populate(pud, addr, next);
178 	} while (pud++, addr = next, addr != end);
179 
180 	return 0;
181 }
182 
183 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
184 				unsigned long end)
185 {
186 	p4d_t *p4d = p4d_offset(pgd, addr);
187 	unsigned long next;
188 
189 	do {
190 		next = p4d_addr_end(addr, end);
191 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
192 			pud_t *pud;
193 			pmd_t *pmd;
194 
195 			p4d_populate(&init_mm, p4d,
196 					lm_alias(kasan_early_shadow_pud));
197 			pud = pud_offset(p4d, addr);
198 			pud_populate(&init_mm, pud,
199 					lm_alias(kasan_early_shadow_pmd));
200 			pmd = pmd_offset(pud, addr);
201 			pmd_populate_kernel(&init_mm, pmd,
202 					lm_alias(kasan_early_shadow_pte));
203 			continue;
204 		}
205 
206 		if (p4d_none(*p4d)) {
207 			pud_t *p;
208 
209 			if (slab_is_available()) {
210 				p = pud_alloc(&init_mm, p4d, addr);
211 				if (!p)
212 					return -ENOMEM;
213 			} else {
214 				p4d_populate(&init_mm, p4d,
215 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
216 			}
217 		}
218 		zero_pud_populate(p4d, addr, next);
219 	} while (p4d++, addr = next, addr != end);
220 
221 	return 0;
222 }
223 
224 /**
225  * kasan_populate_early_shadow - populate shadow memory region with
226  *                               kasan_early_shadow_page
227  * @shadow_start - start of the memory range to populate
228  * @shadow_end   - end of the memory range to populate
229  */
230 int __ref kasan_populate_early_shadow(const void *shadow_start,
231 					const void *shadow_end)
232 {
233 	unsigned long addr = (unsigned long)shadow_start;
234 	unsigned long end = (unsigned long)shadow_end;
235 	pgd_t *pgd = pgd_offset_k(addr);
236 	unsigned long next;
237 
238 	do {
239 		next = pgd_addr_end(addr, end);
240 
241 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
242 			p4d_t *p4d;
243 			pud_t *pud;
244 			pmd_t *pmd;
245 
246 			/*
247 			 * kasan_early_shadow_pud should be populated with pmds
248 			 * at this moment.
249 			 * [pud,pmd]_populate*() below needed only for
250 			 * 3,2 - level page tables where we don't have
251 			 * puds,pmds, so pgd_populate(), pud_populate()
252 			 * is noops.
253 			 *
254 			 * The ifndef is required to avoid build breakage.
255 			 *
256 			 * With 5level-fixup.h, pgd_populate() is not nop and
257 			 * we reference kasan_early_shadow_p4d. It's not defined
258 			 * unless 5-level paging enabled.
259 			 *
260 			 * The ifndef can be dropped once all KASAN-enabled
261 			 * architectures will switch to pgtable-nop4d.h.
262 			 */
263 #ifndef __ARCH_HAS_5LEVEL_HACK
264 			pgd_populate(&init_mm, pgd,
265 					lm_alias(kasan_early_shadow_p4d));
266 #endif
267 			p4d = p4d_offset(pgd, addr);
268 			p4d_populate(&init_mm, p4d,
269 					lm_alias(kasan_early_shadow_pud));
270 			pud = pud_offset(p4d, addr);
271 			pud_populate(&init_mm, pud,
272 					lm_alias(kasan_early_shadow_pmd));
273 			pmd = pmd_offset(pud, addr);
274 			pmd_populate_kernel(&init_mm, pmd,
275 					lm_alias(kasan_early_shadow_pte));
276 			continue;
277 		}
278 
279 		if (pgd_none(*pgd)) {
280 			p4d_t *p;
281 
282 			if (slab_is_available()) {
283 				p = p4d_alloc(&init_mm, pgd, addr);
284 				if (!p)
285 					return -ENOMEM;
286 			} else {
287 				pgd_populate(&init_mm, pgd,
288 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
289 			}
290 		}
291 		zero_p4d_populate(pgd, addr, next);
292 	} while (pgd++, addr = next, addr != end);
293 
294 	return 0;
295 }
296 
297 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
298 {
299 	pte_t *pte;
300 	int i;
301 
302 	for (i = 0; i < PTRS_PER_PTE; i++) {
303 		pte = pte_start + i;
304 		if (!pte_none(*pte))
305 			return;
306 	}
307 
308 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
309 	pmd_clear(pmd);
310 }
311 
312 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
313 {
314 	pmd_t *pmd;
315 	int i;
316 
317 	for (i = 0; i < PTRS_PER_PMD; i++) {
318 		pmd = pmd_start + i;
319 		if (!pmd_none(*pmd))
320 			return;
321 	}
322 
323 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
324 	pud_clear(pud);
325 }
326 
327 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
328 {
329 	pud_t *pud;
330 	int i;
331 
332 	for (i = 0; i < PTRS_PER_PUD; i++) {
333 		pud = pud_start + i;
334 		if (!pud_none(*pud))
335 			return;
336 	}
337 
338 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
339 	p4d_clear(p4d);
340 }
341 
342 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
343 {
344 	p4d_t *p4d;
345 	int i;
346 
347 	for (i = 0; i < PTRS_PER_P4D; i++) {
348 		p4d = p4d_start + i;
349 		if (!p4d_none(*p4d))
350 			return;
351 	}
352 
353 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
354 	pgd_clear(pgd);
355 }
356 
357 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
358 				unsigned long end)
359 {
360 	unsigned long next;
361 
362 	for (; addr < end; addr = next, pte++) {
363 		next = (addr + PAGE_SIZE) & PAGE_MASK;
364 		if (next > end)
365 			next = end;
366 
367 		if (!pte_present(*pte))
368 			continue;
369 
370 		if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
371 			continue;
372 		pte_clear(&init_mm, addr, pte);
373 	}
374 }
375 
376 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
377 				unsigned long end)
378 {
379 	unsigned long next;
380 
381 	for (; addr < end; addr = next, pmd++) {
382 		pte_t *pte;
383 
384 		next = pmd_addr_end(addr, end);
385 
386 		if (!pmd_present(*pmd))
387 			continue;
388 
389 		if (kasan_pte_table(*pmd)) {
390 			if (IS_ALIGNED(addr, PMD_SIZE) &&
391 			    IS_ALIGNED(next, PMD_SIZE))
392 				pmd_clear(pmd);
393 			continue;
394 		}
395 		pte = pte_offset_kernel(pmd, addr);
396 		kasan_remove_pte_table(pte, addr, next);
397 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
398 	}
399 }
400 
401 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
402 				unsigned long end)
403 {
404 	unsigned long next;
405 
406 	for (; addr < end; addr = next, pud++) {
407 		pmd_t *pmd, *pmd_base;
408 
409 		next = pud_addr_end(addr, end);
410 
411 		if (!pud_present(*pud))
412 			continue;
413 
414 		if (kasan_pmd_table(*pud)) {
415 			if (IS_ALIGNED(addr, PUD_SIZE) &&
416 			    IS_ALIGNED(next, PUD_SIZE))
417 				pud_clear(pud);
418 			continue;
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 		pud = pud_offset(p4d, addr);
447 		kasan_remove_pud_table(pud, addr, next);
448 		kasan_free_pud(pud_offset(p4d, 0), p4d);
449 	}
450 }
451 
452 void kasan_remove_zero_shadow(void *start, unsigned long size)
453 {
454 	unsigned long addr, end, next;
455 	pgd_t *pgd;
456 
457 	addr = (unsigned long)kasan_mem_to_shadow(start);
458 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
459 
460 	if (WARN_ON((unsigned long)start %
461 			(KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
462 	    WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
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 		p4d = p4d_offset(pgd, addr);
482 		kasan_remove_p4d_table(p4d, addr, next);
483 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
484 	}
485 }
486 
487 int kasan_add_zero_shadow(void *start, unsigned long size)
488 {
489 	int ret;
490 	void *shadow_start, *shadow_end;
491 
492 	shadow_start = kasan_mem_to_shadow(start);
493 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
494 
495 	if (WARN_ON((unsigned long)start %
496 			(KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)) ||
497 	    WARN_ON(size % (KASAN_SHADOW_SCALE_SIZE * PAGE_SIZE)))
498 		return -EINVAL;
499 
500 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
501 	if (ret)
502 		kasan_remove_zero_shadow(shadow_start,
503 					size >> KASAN_SHADOW_SCALE_SHIFT);
504 	return ret;
505 }
506