init.c

  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#include <linux/pgalloc.h>
 17
 18#include <asm/page.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				kernel_pte_init(p);
132			}
133			if (!p)
134				return -ENOMEM;
135
136			pmd_populate_kernel(&init_mm, pmd, p);
137		}
138		zero_pte_populate(pmd, addr, next);
139	} while (pmd++, addr = next, addr != end);
140
141	return 0;
142}
143
144static int __ref zero_pud_populate(p4d_t *p4d, unsigned long addr,
145				unsigned long end)
146{
147	pud_t *pud = pud_offset(p4d, addr);
148	unsigned long next;
149
150	do {
151		next = pud_addr_end(addr, end);
152		if (IS_ALIGNED(addr, PUD_SIZE) && end - addr >= PUD_SIZE) {
153			pmd_t *pmd;
154
155			pud_populate(&init_mm, pud,
156					lm_alias(kasan_early_shadow_pmd));
157			pmd = pmd_offset(pud, addr);
158			pmd_populate_kernel(&init_mm, pmd,
159					lm_alias(kasan_early_shadow_pte));
160			continue;
161		}
162
163		if (pud_none(*pud)) {
164			pmd_t *p;
165
166			if (slab_is_available()) {
167				p = pmd_alloc(&init_mm, pud, addr);
168				if (!p)
169					return -ENOMEM;
170			} else {
171				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
172				pmd_init(p);
173				pud_populate(&init_mm, pud, p);
174			}
175		}
176		zero_pmd_populate(pud, addr, next);
177	} while (pud++, addr = next, addr != end);
178
179	return 0;
180}
181
182static int __ref zero_p4d_populate(pgd_t *pgd, unsigned long addr,
183				unsigned long end)
184{
185	p4d_t *p4d = p4d_offset(pgd, addr);
186	unsigned long next;
187
188	do {
189		next = p4d_addr_end(addr, end);
190		if (IS_ALIGNED(addr, P4D_SIZE) && end - addr >= P4D_SIZE) {
191			pud_t *pud;
192			pmd_t *pmd;
193
194			p4d_populate_kernel(addr, p4d,
195					lm_alias(kasan_early_shadow_pud));
196			pud = pud_offset(p4d, addr);
197			pud_populate(&init_mm, pud,
198					lm_alias(kasan_early_shadow_pmd));
199			pmd = pmd_offset(pud, addr);
200			pmd_populate_kernel(&init_mm, pmd,
201					lm_alias(kasan_early_shadow_pte));
202			continue;
203		}
204
205		if (p4d_none(*p4d)) {
206			pud_t *p;
207
208			if (slab_is_available()) {
209				p = pud_alloc(&init_mm, p4d, addr);
210				if (!p)
211					return -ENOMEM;
212			} else {
213				p = early_alloc(PAGE_SIZE, NUMA_NO_NODE);
214				pud_init(p);
215				p4d_populate_kernel(addr, p4d, p);
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 */
230int __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			pgd_populate_kernel(addr, pgd,
255					lm_alias(kasan_early_shadow_p4d));
256			p4d = p4d_offset(pgd, addr);
257			p4d_populate_kernel(addr, p4d,
258					lm_alias(kasan_early_shadow_pud));
259			pud = pud_offset(p4d, addr);
260			pud_populate(&init_mm, pud,
261					lm_alias(kasan_early_shadow_pmd));
262			pmd = pmd_offset(pud, addr);
263			pmd_populate_kernel(&init_mm, pmd,
264					lm_alias(kasan_early_shadow_pte));
265			continue;
266		}
267
268		if (pgd_none(*pgd)) {
269
270			if (slab_is_available()) {
271				if (!p4d_alloc(&init_mm, pgd, addr))
272					return -ENOMEM;
273			} else {
274				pgd_populate_kernel(addr, pgd,
275					early_alloc(PAGE_SIZE, NUMA_NO_NODE));
276			}
277		}
278		zero_p4d_populate(pgd, addr, next);
279	} while (pgd++, addr = next, addr != end);
280
281	return 0;
282}
283
284static void kasan_free_pte(pte_t *pte_start, pmd_t *pmd)
285{
286	pte_t *pte;
287	int i;
288
289	for (i = 0; i < PTRS_PER_PTE; i++) {
290		pte = pte_start + i;
291		if (!pte_none(ptep_get(pte)))
292			return;
293	}
294
295	pte_free_kernel(&init_mm, pte_start);
296	pmd_clear(pmd);
297}
298
299static void kasan_free_pmd(pmd_t *pmd_start, pud_t *pud)
300{
301	pmd_t *pmd;
302	int i;
303
304	for (i = 0; i < PTRS_PER_PMD; i++) {
305		pmd = pmd_start + i;
306		if (!pmd_none(*pmd))
307			return;
308	}
309
310	pmd_free(&init_mm, pmd_start);
311	pud_clear(pud);
312}
313
314static void kasan_free_pud(pud_t *pud_start, p4d_t *p4d)
315{
316	pud_t *pud;
317	int i;
318
319	for (i = 0; i < PTRS_PER_PUD; i++) {
320		pud = pud_start + i;
321		if (!pud_none(*pud))
322			return;
323	}
324
325	pud_free(&init_mm, pud_start);
326	p4d_clear(p4d);
327}
328
329static void kasan_free_p4d(p4d_t *p4d_start, pgd_t *pgd)
330{
331	p4d_t *p4d;
332	int i;
333
334	for (i = 0; i < PTRS_PER_P4D; i++) {
335		p4d = p4d_start + i;
336		if (!p4d_none(*p4d))
337			return;
338	}
339
340	p4d_free(&init_mm, p4d_start);
341	pgd_clear(pgd);
342}
343
344static void kasan_remove_pte_table(pte_t *pte, unsigned long addr,
345				unsigned long end)
346{
347	unsigned long next;
348	pte_t ptent;
349
350	for (; addr < end; addr = next, pte++) {
351		next = (addr + PAGE_SIZE) & PAGE_MASK;
352		if (next > end)
353			next = end;
354
355		ptent = ptep_get(pte);
356
357		if (!pte_present(ptent))
358			continue;
359
360		if (WARN_ON(!kasan_early_shadow_page_entry(ptent)))
361			continue;
362		pte_clear(&init_mm, addr, pte);
363	}
364}
365
366static void kasan_remove_pmd_table(pmd_t *pmd, unsigned long addr,
367				unsigned long end)
368{
369	unsigned long next;
370
371	for (; addr < end; addr = next, pmd++) {
372		pte_t *pte;
373
374		next = pmd_addr_end(addr, end);
375
376		if (!pmd_present(*pmd))
377			continue;
378
379		if (kasan_pte_table(*pmd)) {
380			if (IS_ALIGNED(addr, PMD_SIZE) &&
381			    IS_ALIGNED(next, PMD_SIZE)) {
382				pmd_clear(pmd);
383				continue;
384			}
385		}
386		pte = pte_offset_kernel(pmd, addr);
387		kasan_remove_pte_table(pte, addr, next);
388		kasan_free_pte(pte_offset_kernel(pmd, 0), pmd);
389	}
390}
391
392static void kasan_remove_pud_table(pud_t *pud, unsigned long addr,
393				unsigned long end)
394{
395	unsigned long next;
396
397	for (; addr < end; addr = next, pud++) {
398		pmd_t *pmd, *pmd_base;
399
400		next = pud_addr_end(addr, end);
401
402		if (!pud_present(*pud))
403			continue;
404
405		if (kasan_pmd_table(*pud)) {
406			if (IS_ALIGNED(addr, PUD_SIZE) &&
407			    IS_ALIGNED(next, PUD_SIZE)) {
408				pud_clear(pud);
409				continue;
410			}
411		}
412		pmd = pmd_offset(pud, addr);
413		pmd_base = pmd_offset(pud, 0);
414		kasan_remove_pmd_table(pmd, addr, next);
415		kasan_free_pmd(pmd_base, pud);
416	}
417}
418
419static void kasan_remove_p4d_table(p4d_t *p4d, unsigned long addr,
420				unsigned long end)
421{
422	unsigned long next;
423
424	for (; addr < end; addr = next, p4d++) {
425		pud_t *pud;
426
427		next = p4d_addr_end(addr, end);
428
429		if (!p4d_present(*p4d))
430			continue;
431
432		if (kasan_pud_table(*p4d)) {
433			if (IS_ALIGNED(addr, P4D_SIZE) &&
434			    IS_ALIGNED(next, P4D_SIZE)) {
435				p4d_clear(p4d);
436				continue;
437			}
438		}
439		pud = pud_offset(p4d, addr);
440		kasan_remove_pud_table(pud, addr, next);
441		kasan_free_pud(pud_offset(p4d, 0), p4d);
442	}
443}
444
445void kasan_remove_zero_shadow(void *start, unsigned long size)
446{
447	unsigned long addr, end, next;
448	pgd_t *pgd;
449
450	addr = (unsigned long)kasan_mem_to_shadow(start);
451	end = addr + (size >> KASAN_SHADOW_SCALE_SHIFT);
452
453	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
454	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
455		return;
456
457	for (; addr < end; addr = next) {
458		p4d_t *p4d;
459
460		next = pgd_addr_end(addr, end);
461
462		pgd = pgd_offset_k(addr);
463		if (!pgd_present(*pgd))
464			continue;
465
466		if (kasan_p4d_table(*pgd)) {
467			if (IS_ALIGNED(addr, PGDIR_SIZE) &&
468			    IS_ALIGNED(next, PGDIR_SIZE)) {
469				pgd_clear(pgd);
470				continue;
471			}
472		}
473
474		p4d = p4d_offset(pgd, addr);
475		kasan_remove_p4d_table(p4d, addr, next);
476		kasan_free_p4d(p4d_offset(pgd, 0), pgd);
477	}
478}
479
480int kasan_add_zero_shadow(void *start, unsigned long size)
481{
482	int ret;
483	void *shadow_start, *shadow_end;
484
485	shadow_start = kasan_mem_to_shadow(start);
486	shadow_end = shadow_start + (size >> KASAN_SHADOW_SCALE_SHIFT);
487
488	if (WARN_ON((unsigned long)start % KASAN_MEMORY_PER_SHADOW_PAGE) ||
489	    WARN_ON(size % KASAN_MEMORY_PER_SHADOW_PAGE))
490		return -EINVAL;
491
492	ret = kasan_populate_early_shadow(shadow_start, shadow_end);
493	if (ret)
494		kasan_remove_zero_shadow(start, size);
495	return ret;
496}