xref: /openbmc/linux/mm/kasan/init.c (revision dfe94d40) 
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[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[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[PTRS_PER_PTE] __page_aligned_bss;
68 
69 static inline bool kasan_pte_table(pmd_t pmd)
70 {
71 	return pmd_page(pmd) == virt_to_page(lm_alias(kasan_early_shadow_pte));
72 }
73 
74 static inline bool kasan_early_shadow_page_entry(pte_t pte)
75 {
76 	return pte_page(pte) == virt_to_page(lm_alias(kasan_early_shadow_page));
77 }
78 
79 static __init void *early_alloc(size_t size, int node)
80 {
81 	void *ptr = memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
82 					   MEMBLOCK_ALLOC_ACCESSIBLE, node);
83 
84 	if (!ptr)
85 		panic("%s: Failed to allocate %zu bytes align=%zx nid=%d from=%llx\n",
86 		      __func__, size, size, node, (u64)__pa(MAX_DMA_ADDRESS));
87 
88 	return ptr;
89 }
90 
91 static void __ref zero_pte_populate(pmd_t *pmd, unsigned long addr,
92 				unsigned long end)
93 {
94 	pte_t *pte = pte_offset_kernel(pmd, addr);
95 	pte_t zero_pte;
96 
97 	zero_pte = pfn_pte(PFN_DOWN(__pa_symbol(kasan_early_shadow_page)),
98 				PAGE_KERNEL);
99 	zero_pte = pte_wrprotect(zero_pte);
100 
101 	while (addr + PAGE_SIZE <= end) {
102 		set_pte_at(&init_mm, addr, pte, zero_pte);
103 		addr += PAGE_SIZE;
104 		pte = pte_offset_kernel(pmd, addr);
105 	}
106 }
107 
108 static int __ref zero_pmd_populate(pud_t *pud, unsigned long addr,
109 				unsigned long end)
110 {
111 	pmd_t *pmd = pmd_offset(pud, addr);
112 	unsigned long next;
113 
114 	do {
115 		next = pmd_addr_end(addr, end);
116 
117 		if (IS_ALIGNED(addr, PMD_SIZE) && end - addr >= PMD_SIZE) {
118 			pmd_populate_kernel(&init_mm, pmd,
119 					lm_alias(kasan_early_shadow_pte));
120 			continue;
121 		}
122 
123 		if (pmd_none(*pmd)) {
124 			pte_t *p;
125 
126 			if (slab_is_available())
127 				p = pte_alloc_one_kernel(&init_mm);
128 			else
129 				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
130 			if (!p)
131 				return -ENOMEM;
132 
133 			pmd_populate_kernel(&init_mm, pmd, p);
134 		}
135 		zero_pte_populate(pmd, addr, next);
136 	} while (pmd++, addr = next, addr != end);
137 
138 	return 0;
139 }
140 
141 static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
142 				unsigned long end)
143 {
144 	pud_t *pud = pud_offset(p4d, addr);
145 	unsigned long next;
146 
147 	do {
148 		next = pud_addr_end(addr, end);
149 		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
150 			pmd_t *pmd;
151 
152 			pud_populate(&init_mm, pud,
153 					lm_alias(kasan_early_shadow_pmd));
154 			pmd = pmd_offset(pud, addr);
155 			pmd_populate_kernel(&init_mm, pmd,
156 					lm_alias(kasan_early_shadow_pte));
157 			continue;
158 		}
159 
160 		if (pud_none(*pud)) {
161 			pmd_t *p;
162 
163 			if (slab_is_available()) {
164 				p = pmd_alloc(&init_mm, pud, addr);
165 				if (!p)
166 					return -ENOMEM;
167 			} else {
168 				pud_populate(&init_mm, pud,
169 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
170 			}
171 		}
172 		zero_pmd_populate(pud, addr, next);
173 	} while (pud++, addr = next, addr != end);
174 
175 	return 0;
176 }
177 
178 static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
179 				unsigned long end)
180 {
181 	p4d_t *p4d = p4d_offset(pgd, addr);
182 	unsigned long next;
183 
184 	do {
185 		next = p4d_addr_end(addr, end);
186 		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
187 			pud_t *pud;
188 			pmd_t *pmd;
189 
190 			p4d_populate(&init_mm, p4d,
191 					lm_alias(kasan_early_shadow_pud));
192 			pud = pud_offset(p4d, addr);
193 			pud_populate(&init_mm, pud,
194 					lm_alias(kasan_early_shadow_pmd));
195 			pmd = pmd_offset(pud, addr);
196 			pmd_populate_kernel(&init_mm, pmd,
197 					lm_alias(kasan_early_shadow_pte));
198 			continue;
199 		}
200 
201 		if (p4d_none(*p4d)) {
202 			pud_t *p;
203 
204 			if (slab_is_available()) {
205 				p = pud_alloc(&init_mm, p4d, addr);
206 				if (!p)
207 					return -ENOMEM;
208 			} else {
209 				p4d_populate(&init_mm, p4d,
210 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
211 			}
212 		}
213 		zero_pud_populate(p4d, addr, next);
214 	} while (p4d++, addr = next, addr != end);
215 
216 	return 0;
217 }
218 
219 /**
220  * kasan_populate_early_shadow - populate shadow memory region with
221  *                               kasan_early_shadow_page
222  * @shadow_start - start of the memory range to populate
223  * @shadow_end   - end of the memory range to populate
224  */
225 int __ref kasan_populate_early_shadow(const void *shadow_start,
226 					const void *shadow_end)
227 {
228 	unsigned long addr = (unsigned long)shadow_start;
229 	unsigned long end = (unsigned long)shadow_end;
230 	pgd_t *pgd = pgd_offset_k(addr);
231 	unsigned long next;
232 
233 	do {
234 		next = pgd_addr_end(addr, end);
235 
236 		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
237 			p4d_t *p4d;
238 			pud_t *pud;
239 			pmd_t *pmd;
240 
241 			/*
242 			 * kasan_early_shadow_pud should be populated with pmds
243 			 * at this moment.
244 			 * [pud,pmd]_populate*() below needed only for
245 			 * 3,2 - level page tables where we don't have
246 			 * puds,pmds, so pgd_populate(), pud_populate()
247 			 * is noops.
248 			 */
249 			pgd_populate(&init_mm, pgd,
250 					lm_alias(kasan_early_shadow_p4d));
251 			p4d = p4d_offset(pgd, addr);
252 			p4d_populate(&init_mm, p4d,
253 					lm_alias(kasan_early_shadow_pud));
254 			pud = pud_offset(p4d, addr);
255 			pud_populate(&init_mm, pud,
256 					lm_alias(kasan_early_shadow_pmd));
257 			pmd = pmd_offset(pud, addr);
258 			pmd_populate_kernel(&init_mm, pmd,
259 					lm_alias(kasan_early_shadow_pte));
260 			continue;
261 		}
262 
263 		if (pgd_none(*pgd)) {
264 			p4d_t *p;
265 
266 			if (slab_is_available()) {
267 				p = p4d_alloc(&init_mm, pgd, addr);
268 				if (!p)
269 					return -ENOMEM;
270 			} else {
271 				pgd_populate(&init_mm, pgd,
272 					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
273 			}
274 		}
275 		zero_p4d_populate(pgd, addr, next);
276 	} while (pgd++, addr = next, addr != end);
277 
278 	return 0;
279 }
280 
281 static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
282 {
283 	pte_t *pte;
284 	int i;
285 
286 	for (i = 0; i < PTRS_PER_PTE; i++) {
287 		pte = pte_start + i;
288 		if (!pte_none(*pte))
289 			return;
290 	}
291 
292 	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
293 	pmd_clear(pmd);
294 }
295 
296 static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
297 {
298 	pmd_t *pmd;
299 	int i;
300 
301 	for (i = 0; i < PTRS_PER_PMD; i++) {
302 		pmd = pmd_start + i;
303 		if (!pmd_none(*pmd))
304 			return;
305 	}
306 
307 	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
308 	pud_clear(pud);
309 }
310 
311 static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
312 {
313 	pud_t *pud;
314 	int i;
315 
316 	for (i = 0; i < PTRS_PER_PUD; i++) {
317 		pud = pud_start + i;
318 		if (!pud_none(*pud))
319 			return;
320 	}
321 
322 	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
323 	p4d_clear(p4d);
324 }
325 
326 static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
327 {
328 	p4d_t *p4d;
329 	int i;
330 
331 	for (i = 0; i < PTRS_PER_P4D; i++) {
332 		p4d = p4d_start + i;
333 		if (!p4d_none(*p4d))
334 			return;
335 	}
336 
337 	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
338 	pgd_clear(pgd);
339 }
340 
341 static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
342 				unsigned long end)
343 {
344 	unsigned long next;
345 
346 	for (; addr < end; addr = next, pte++) {
347 		next = (addr + PAGE_SIZE) & PAGE_MASK;
348 		if (next > end)
349 			next = end;
350 
351 		if (!pte_present(*pte))
352 			continue;
353 
354 		if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
355 			continue;
356 		pte_clear(&init_mm, addr, pte);
357 	}
358 }
359 
360 static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
361 				unsigned long end)
362 {
363 	unsigned long next;
364 
365 	for (; addr < end; addr = next, pmd++) {
366 		pte_t *pte;
367 
368 		next = pmd_addr_end(addr, end);
369 
370 		if (!pmd_present(*pmd))
371 			continue;
372 
373 		if (kasan_pte_table(*pmd)) {
374 			if (IS_ALIGNED(addr, PMD_SIZE) &&
375 			    IS_ALIGNED(next, PMD_SIZE))
376 				pmd_clear(pmd);
377 			continue;
378 		}
379 		pte = pte_offset_kernel(pmd, addr);
380 		kasan_remove_pte_table(pte, addr, next);
381 		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
382 	}
383 }
384 
385 static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
386 				unsigned long end)
387 {
388 	unsigned long next;
389 
390 	for (; addr < end; addr = next, pud++) {
391 		pmd_t *pmd, *pmd_base;
392 
393 		next = pud_addr_end(addr, end);
394 
395 		if (!pud_present(*pud))
396 			continue;
397 
398 		if (kasan_pmd_table(*pud)) {
399 			if (IS_ALIGNED(addr, PUD_SIZE) &&
400 			    IS_ALIGNED(next, PUD_SIZE))
401 				pud_clear(pud);
402 			continue;
403 		}
404 		pmd = pmd_offset(pud, addr);
405 		pmd_base = pmd_offset(pud, 0);
406 		kasan_remove_pmd_table(pmd, addr, next);
407 		kasan_free_pmd(pmd_base, pud);
408 	}
409 }
410 
411 static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
412 				unsigned long end)
413 {
414 	unsigned long next;
415 
416 	for (; addr < end; addr = next, p4d++) {
417 		pud_t *pud;
418 
419 		next = p4d_addr_end(addr, end);
420 
421 		if (!p4d_present(*p4d))
422 			continue;
423 
424 		if (kasan_pud_table(*p4d)) {
425 			if (IS_ALIGNED(addr, P4D_SIZE) &&
426 			    IS_ALIGNED(next, P4D_SIZE))
427 				p4d_clear(p4d);
428 			continue;
429 		}
430 		pud = pud_offset(p4d, addr);
431 		kasan_remove_pud_table(pud, addr, next);
432 		kasan_free_pud(pud_offset(p4d, 0), p4d);
433 	}
434 }
435 
436 void kasan_remove_zero_shadow(void *start, unsigned long size)
437 {
438 	unsigned long addr, end, next;
439 	pgd_t *pgd;
440 
441 	addr = (unsigned long)kasan_mem_to_shadow(start);
442 	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
443 
444 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
445 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
446 		return;
447 
448 	for (; addr < end; addr = next) {
449 		p4d_t *p4d;
450 
451 		next = pgd_addr_end(addr, end);
452 
453 		pgd = pgd_offset_k(addr);
454 		if (!pgd_present(*pgd))
455 			continue;
456 
457 		if (kasan_p4d_table(*pgd)) {
458 			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
459 			    IS_ALIGNED(next, PGDIR_SIZE))
460 				pgd_clear(pgd);
461 			continue;
462 		}
463 
464 		p4d = p4d_offset(pgd, addr);
465 		kasan_remove_p4d_table(p4d, addr, next);
466 		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
467 	}
468 }
469 
470 int kasan_add_zero_shadow(void *start, unsigned long size)
471 {
472 	int ret;
473 	void *shadow_start, *shadow_end;
474 
475 	shadow_start = kasan_mem_to_shadow(start);
476 	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
477 
478 	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
479 	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
480 		return -EINVAL;
481 
482 	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
483 	if (ret)
484 		kasan_remove_zero_shadow(shadow_start,
485 					size >> KASAN_SHADOW_SCALE_SHIFT);
486 	return ret;
487 }
488