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
142void __weak __meminit pmd_init(void *addr)
143{
144}
145
146static 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				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
174				pmd_init(p);
175				pud_populate(&init_mm, pud, p);
176			}
177		}
178		zero_pmd_populate(pud, addr, next);
179	} while (pud++, addr = next, addr != end);
180
181	return 0;
182}
183
184void __weak __meminit pud_init(void *addr)
185{
186}
187
188static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
189				unsigned long end)
190{
191	p4d_t *p4d = p4d_offset(pgd, addr);
192	unsigned long next;
193
194	do {
195		next = p4d_addr_end(addr, end);
196		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
197			pud_t *pud;
198			pmd_t *pmd;
199
200			p4d_populate(&init_mm, p4d,
201					lm_alias(kasan_early_shadow_pud));
202			pud = pud_offset(p4d, addr);
203			pud_populate(&init_mm, pud,
204					lm_alias(kasan_early_shadow_pmd));
205			pmd = pmd_offset(pud, addr);
206			pmd_populate_kernel(&init_mm, pmd,
207					lm_alias(kasan_early_shadow_pte));
208			continue;
209		}
210
211		if (p4d_none(*p4d)) {
212			pud_t *p;
213
214			if (slab_is_available()) {
215				p = pud_alloc(&init_mm, p4d, addr);
216				if (!p)
217					return -ENOMEM;
218			} else {
219				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
220				pud_init(p);
221				p4d_populate(&init_mm, p4d, p);
222			}
223		}
224		zero_pud_populate(p4d, addr, next);
225	} while (p4d++, addr = next, addr != end);
226
227	return 0;
228}
229
230/**
231 * kasan_populate_early_shadow - populate shadow memory region with
232 *                               kasan_early_shadow_page
233 * @shadow_start: start of the memory range to populate
234 * @shadow_end: end of the memory range to populate
235 */
236int __ref kasan_populate_early_shadow(const void *shadow_start,
237					const void *shadow_end)
238{
239	unsigned long addr = (unsigned long)shadow_start;
240	unsigned long end = (unsigned long)shadow_end;
241	pgd_t *pgd = pgd_offset_k(addr);
242	unsigned long next;
243
244	do {
245		next = pgd_addr_end(addr, end);
246
247		if (IS_ALIGNED(addr, PGDIR_SIZE) && end - addr >= PGDIR_SIZE) {
248			p4d_t *p4d;
249			pud_t *pud;
250			pmd_t *pmd;
251
252			/*
253			 * kasan_early_shadow_pud should be populated with pmds
254			 * at this moment.
255			 * [pud,pmd]_populate*() below needed only for
256			 * 3,2 - level page tables where we don't have
257			 * puds,pmds, so pgd_populate(), pud_populate()
258			 * is noops.
259			 */
260			pgd_populate(&init_mm, pgd,
261					lm_alias(kasan_early_shadow_p4d));
262			p4d = p4d_offset(pgd, addr);
263			p4d_populate(&init_mm, p4d,
264					lm_alias(kasan_early_shadow_pud));
265			pud = pud_offset(p4d, addr);
266			pud_populate(&init_mm, pud,
267					lm_alias(kasan_early_shadow_pmd));
268			pmd = pmd_offset(pud, addr);
269			pmd_populate_kernel(&init_mm, pmd,
270					lm_alias(kasan_early_shadow_pte));
271			continue;
272		}
273
274		if (pgd_none(*pgd)) {
275			p4d_t *p;
276
277			if (slab_is_available()) {
278				p = p4d_alloc(&init_mm, pgd, addr);
279				if (!p)
280					return -ENOMEM;
281			} else {
282				pgd_populate(&init_mm, pgd,
283					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
284			}
285		}
286		zero_p4d_populate(pgd, addr, next);
287	} while (pgd++, addr = next, addr != end);
288
289	return 0;
290}
291
292static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
293{
294	pte_t *pte;
295	int i;
296
297	for (i = 0; i < PTRS_PER_PTE; i++) {
298		pte = pte_start + i;
299		if (!pte_none(ptep_get(pte)))
300			return;
301	}
302
303	pte_free_kernel(&init_mm, (pte_t *)page_to_virt(pmd_page(*pmd)));
304	pmd_clear(pmd);
305}
306
307static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
308{
309	pmd_t *pmd;
310	int i;
311
312	for (i = 0; i < PTRS_PER_PMD; i++) {
313		pmd = pmd_start + i;
314		if (!pmd_none(*pmd))
315			return;
316	}
317
318	pmd_free(&init_mm, (pmd_t *)page_to_virt(pud_page(*pud)));
319	pud_clear(pud);
320}
321
322static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
323{
324	pud_t *pud;
325	int i;
326
327	for (i = 0; i < PTRS_PER_PUD; i++) {
328		pud = pud_start + i;
329		if (!pud_none(*pud))
330			return;
331	}
332
333	pud_free(&init_mm, (pud_t *)page_to_virt(p4d_page(*p4d)));
334	p4d_clear(p4d);
335}
336
337static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
338{
339	p4d_t *p4d;
340	int i;
341
342	for (i = 0; i < PTRS_PER_P4D; i++) {
343		p4d = p4d_start + i;
344		if (!p4d_none(*p4d))
345			return;
346	}
347
348	p4d_free(&init_mm, (p4d_t *)page_to_virt(pgd_page(*pgd)));
349	pgd_clear(pgd);
350}
351
352static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
353				unsigned long end)
354{
355	unsigned long next;
356	pte_t ptent;
357
358	for (; addr < end; addr = next, pte++) {
359		next = (addr + PAGE_SIZE) & PAGE_MASK;
360		if (next > end)
361			next = end;
362
363		ptent = ptep_get(pte);
364
365		if (!pte_present(ptent))
366			continue;
367
368		if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
369			continue;
370		pte_clear(&init_mm, addr, pte);
371	}
372}
373
374static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
375				unsigned long end)
376{
377	unsigned long next;
378
379	for (; addr < end; addr = next, pmd++) {
380		pte_t *pte;
381
382		next = pmd_addr_end(addr, end);
383
384		if (!pmd_present(*pmd))
385			continue;
386
387		if (kasan_pte_table(*pmd)) {
388			if (IS_ALIGNED(addr, PMD_SIZE) &&
389			    IS_ALIGNED(next, PMD_SIZE)) {
390				pmd_clear(pmd);
391				continue;
392			}
393		}
394		pte = pte_offset_kernel(pmd, addr);
395		kasan_remove_pte_table(pte, addr, next);
396		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
397	}
398}
399
400static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
401				unsigned long end)
402{
403	unsigned long next;
404
405	for (; addr < end; addr = next, pud++) {
406		pmd_t *pmd, *pmd_base;
407
408		next = pud_addr_end(addr, end);
409
410		if (!pud_present(*pud))
411			continue;
412
413		if (kasan_pmd_table(*pud)) {
414			if (IS_ALIGNED(addr, PUD_SIZE) &&
415			    IS_ALIGNED(next, PUD_SIZE)) {
416				pud_clear(pud);
417				continue;
418			}
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
427static 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		}
447		pud = pud_offset(p4d, addr);
448		kasan_remove_pud_table(pud, addr, next);
449		kasan_free_pud(pud_offset(p4d, 0), p4d);
450	}
451}
452
453void kasan_remove_zero_shadow(void *start, unsigned long size)
454{
455	unsigned long addr, end, next;
456	pgd_t *pgd;
457
458	addr = (unsigned long)kasan_mem_to_shadow(start);
459	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
460
461	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
462	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
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
482		p4d = p4d_offset(pgd, addr);
483		kasan_remove_p4d_table(p4d, addr, next);
484		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
485	}
486}
487
488int kasan_add_zero_shadow(void *start, unsigned long size)
489{
490	int ret;
491	void *shadow_start, *shadow_end;
492
493	shadow_start = kasan_mem_to_shadow(start);
494	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
495
496	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
497	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
498		return -EINVAL;
499
500	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
501	if (ret)
502		kasan_remove_zero_shadow(start, size);
503	return ret;
504}
505