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 */
29unsigned char kasan_early_shadow_page[PAGE_SIZE] __page_aligned_bss;
30
31#if CONFIG_PGTABLE_LEVELS > 4
32p4d_t kasan_early_shadow_p4d[MAX_PTRS_PER_P4D] __page_aligned_bss;
33static 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
38static inline bool kasan_p4d_table(pgd_t pgd)
39{
40 return false;
41}
42#endif
43#if CONFIG_PGTABLE_LEVELS > 3
44pud_t kasan_early_shadow_pud[MAX_PTRS_PER_PUD] __page_aligned_bss;
45static 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
50static inline bool kasan_pud_table(p4d_t p4d)
51{
52 return false;
53}
54#endif
55#if CONFIG_PGTABLE_LEVELS > 2
56pmd_t kasan_early_shadow_pmd[MAX_PTRS_PER_PMD] __page_aligned_bss;
57static 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
62static inline bool kasan_pmd_table(pud_t pud)
63{
64 return false;
65}
66#endif
67pte_t kasan_early_shadow_pte[MAX_PTRS_PER_PTE + PTE_HWTABLE_PTRS]
68 __page_aligned_bss;
69
70static 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
75static 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
80static __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
92static 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
109static 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
142static 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
179static 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 */
226int __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
282static 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(*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
297static 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
312static 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
327static 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
342static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
343 unsigned long end)
344{
345 unsigned long next;
346
347 for (; addr < end; addr = next, pte++) {
348 next = (addr + PAGE_SIZE) & PAGE_MASK;
349 if (next > end)
350 next = end;
351
352 if (!pte_present(*pte))
353 continue;
354
355 if (WARN_ON(!kasan_early_shadow_page_entry(*pte)))
356 continue;
357 pte_clear(&init_mm, addr, pte);
358 }
359}
360
361static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
362 unsigned long end)
363{
364 unsigned long next;
365
366 for (; addr < end; addr = next, pmd++) {
367 pte_t *pte;
368
369 next = pmd_addr_end(addr, end);
370
371 if (!pmd_present(*pmd))
372 continue;
373
374 if (kasan_pte_table(*pmd)) {
375 if (IS_ALIGNED(addr, PMD_SIZE) &&
376 IS_ALIGNED(next, PMD_SIZE)) {
377 pmd_clear(pmd);
378 continue;
379 }
380 }
381 pte = pte_offset_kernel(pmd, addr);
382 kasan_remove_pte_table(pte, addr, next);
383 kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
384 }
385}
386
387static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
388 unsigned long end)
389{
390 unsigned long next;
391
392 for (; addr < end; addr = next, pud++) {
393 pmd_t *pmd, *pmd_base;
394
395 next = pud_addr_end(addr, end);
396
397 if (!pud_present(*pud))
398 continue;
399
400 if (kasan_pmd_table(*pud)) {
401 if (IS_ALIGNED(addr, PUD_SIZE) &&
402 IS_ALIGNED(next, PUD_SIZE)) {
403 pud_clear(pud);
404 continue;
405 }
406 }
407 pmd = pmd_offset(pud, addr);
408 pmd_base = pmd_offset(pud, 0);
409 kasan_remove_pmd_table(pmd, addr, next);
410 kasan_free_pmd(pmd_base, pud);
411 }
412}
413
414static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
415 unsigned long end)
416{
417 unsigned long next;
418
419 for (; addr < end; addr = next, p4d++) {
420 pud_t *pud;
421
422 next = p4d_addr_end(addr, end);
423
424 if (!p4d_present(*p4d))
425 continue;
426
427 if (kasan_pud_table(*p4d)) {
428 if (IS_ALIGNED(addr, P4D_SIZE) &&
429 IS_ALIGNED(next, P4D_SIZE)) {
430 p4d_clear(p4d);
431 continue;
432 }
433 }
434 pud = pud_offset(p4d, addr);
435 kasan_remove_pud_table(pud, addr, next);
436 kasan_free_pud(pud_offset(p4d, 0), p4d);
437 }
438}
439
440void kasan_remove_zero_shadow(void *start, unsigned long size)
441{
442 unsigned long addr, end, next;
443 pgd_t *pgd;
444
445 addr = (unsigned long)kasan_mem_to_shadow(start);
446 end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
447
448 if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
449 WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
450 return;
451
452 for (; addr < end; addr = next) {
453 p4d_t *p4d;
454
455 next = pgd_addr_end(addr, end);
456
457 pgd = pgd_offset_k(addr);
458 if (!pgd_present(*pgd))
459 continue;
460
461 if (kasan_p4d_table(*pgd)) {
462 if (IS_ALIGNED(addr, PGDIR_SIZE) &&
463 IS_ALIGNED(next, PGDIR_SIZE)) {
464 pgd_clear(pgd);
465 continue;
466 }
467 }
468
469 p4d = p4d_offset(pgd, addr);
470 kasan_remove_p4d_table(p4d, addr, next);
471 kasan_free_p4d(p4d_offset(pgd, 0), pgd);
472 }
473}
474
475int kasan_add_zero_shadow(void *start, unsigned long size)
476{
477 int ret;
478 void *shadow_start, *shadow_end;
479
480 shadow_start = kasan_mem_to_shadow(start);
481 shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
482
483 if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
484 WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
485 return -EINVAL;
486
487 ret = kasan_populate_early_shadow(shadow_start, shadow_end);
488 if (ret)
489 kasan_remove_zero_shadow(start, size);
490 return ret;
491}
492

source code of linux/mm/kasan/init.c