1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * This file contains kasan initialization code for ARM.
4 *
5 * Copyright (c) 2018 Samsung Electronics Co., Ltd.
6 * Author: Andrey Ryabinin <ryabinin.a.a@gmail.com>
7 * Author: Linus Walleij <linus.walleij@linaro.org>
8 */
9
10 #define pr_fmt(fmt) "kasan: " fmt
11 #include <linux/kasan.h>
12 #include <linux/kernel.h>
13 #include <linux/memblock.h>
14 #include <linux/sched/task.h>
15 #include <linux/start_kernel.h>
16 #include <linux/pgtable.h>
17 #include <asm/cputype.h>
18 #include <asm/highmem.h>
19 #include <asm/mach/map.h>
20 #include <asm/page.h>
21 #include <asm/pgalloc.h>
22 #include <asm/procinfo.h>
23 #include <asm/proc-fns.h>
24
25 #include "mm.h"
26
27 static pgd_t tmp_pgd_table[PTRS_PER_PGD] __initdata __aligned(PGD_SIZE);
28
29 pmd_t tmp_pmd_table[PTRS_PER_PMD] __page_aligned_bss;
30
31 static __init void *kasan_alloc_block_raw(size_t size)
32 {
33 return memblock_alloc_try_nid_raw(size, size, __pa(MAX_DMA_ADDRESS),
34 MEMBLOCK_ALLOC_NOLEAKTRACE, NUMA_NO_NODE);
35 }
36
37 static __init void *kasan_alloc_block(size_t size)
38 {
39 return memblock_alloc_try_nid(size, size, __pa(MAX_DMA_ADDRESS),
40 MEMBLOCK_ALLOC_NOLEAKTRACE, NUMA_NO_NODE);
41 }
42
43 static void __init kasan_pte_populate(pmd_t *pmdp, unsigned long addr,
44 unsigned long end, bool early)
45 {
46 unsigned long next;
47 pte_t *ptep = pte_offset_kernel(pmdp, addr);
48
49 do {
50 pte_t entry;
51 void *p;
52
53 next = addr + PAGE_SIZE;
54
55 if (!early) {
56 if (!pte_none(READ_ONCE(*ptep)))
57 continue;
58
59 p = kasan_alloc_block_raw(PAGE_SIZE);
60 if (!p) {
61 panic("%s failed to allocate shadow page for address 0x%lx\n",
62 __func__, addr);
63 return;
64 }
65 memset(p, KASAN_SHADOW_INIT, PAGE_SIZE);
66 entry = pfn_pte(virt_to_pfn(p),
67 __pgprot(pgprot_val(PAGE_KERNEL)));
68 } else if (pte_none(READ_ONCE(*ptep))) {
69 /*
70 * The early shadow memory is mapping all KASan
71 * operations to one and the same page in memory,
72 * "kasan_early_shadow_page" so that the instrumentation
73 * will work on a scratch area until we can set up the
74 * proper KASan shadow memory.
75 */
76 entry = pfn_pte(virt_to_pfn(kasan_early_shadow_page),
77 __pgprot(_L_PTE_DEFAULT | L_PTE_DIRTY | L_PTE_XN));
78 } else {
79 /*
80 * Early shadow mappings are PMD_SIZE aligned, so if the
81 * first entry is already set, they must all be set.
82 */
83 return;
84 }
85
86 set_pte_at(&init_mm, addr, ptep, entry);
87 } while (ptep++, addr = next, addr != end);
88 }
89
90 /*
91 * The pmd (page middle directory) is only used on LPAE
92 */
93 static void __init kasan_pmd_populate(pud_t *pudp, unsigned long addr,
94 unsigned long end, bool early)
95 {
96 unsigned long next;
97 pmd_t *pmdp = pmd_offset(pudp, addr);
98
99 do {
100 if (pmd_none(*pmdp)) {
101 /*
102 * We attempt to allocate a shadow block for the PMDs
103 * used by the PTEs for this address if it isn't already
104 * allocated.
105 */
106 void *p = early ? kasan_early_shadow_pte :
107 kasan_alloc_block(PAGE_SIZE);
108
109 if (!p) {
110 panic("%s failed to allocate shadow block for address 0x%lx\n",
111 __func__, addr);
112 return;
113 }
114 pmd_populate_kernel(&init_mm, pmdp, p);
115 flush_pmd_entry(pmdp);
116 }
117
118 next = pmd_addr_end(addr, end);
119 kasan_pte_populate(pmdp, addr, next, early);
120 } while (pmdp++, addr = next, addr != end);
121 }
122
123 static void __init kasan_pgd_populate(unsigned long addr, unsigned long end,
124 bool early)
125 {
126 unsigned long next;
127 pgd_t *pgdp;
128 p4d_t *p4dp;
129 pud_t *pudp;
130
131 pgdp = pgd_offset_k(addr);
132
133 do {
134 /*
135 * Allocate and populate the shadow block of p4d folded into
136 * pud folded into pmd if it doesn't already exist
137 */
138 if (!early && pgd_none(*pgdp)) {
139 void *p = kasan_alloc_block(PAGE_SIZE);
140
141 if (!p) {
142 panic("%s failed to allocate shadow block for address 0x%lx\n",
143 __func__, addr);
144 return;
145 }
146 pgd_populate(&init_mm, pgdp, p);
147 }
148
149 next = pgd_addr_end(addr, end);
150 /*
151 * We just immediately jump over the p4d and pud page
152 * directories since we believe ARM32 will never gain four
153 * nor five level page tables.
154 */
155 p4dp = p4d_offset(pgdp, addr);
156 pudp = pud_offset(p4dp, addr);
157
158 kasan_pmd_populate(pudp, addr, next, early);
159 } while (pgdp++, addr = next, addr != end);
160 }
161
162 extern struct proc_info_list *lookup_processor_type(unsigned int);
163
164 void __init kasan_early_init(void)
165 {
166 struct proc_info_list *list;
167
168 /*
169 * locate processor in the list of supported processor
170 * types. The linker builds this table for us from the
171 * entries in arch/arm/mm/proc-*.S
172 */
173 list = lookup_processor_type(read_cpuid_id());
174 if (list) {
175 #ifdef MULTI_CPU
176 processor = *list->proc;
177 #endif
178 }
179
180 BUILD_BUG_ON((KASAN_SHADOW_END - (1UL << 29)) != KASAN_SHADOW_OFFSET);
181 /*
182 * We walk the page table and set all of the shadow memory to point
183 * to the scratch page.
184 */
185 kasan_pgd_populate(KASAN_SHADOW_START, KASAN_SHADOW_END, true);
186 }
187
188 static void __init clear_pgds(unsigned long start,
189 unsigned long end)
190 {
191 for (; start && start < end; start += PMD_SIZE)
192 pmd_clear(pmd_off_k(start));
193 }
194
195 static int __init create_mapping(void *start, void *end)
196 {
197 void *shadow_start, *shadow_end;
198
199 shadow_start = kasan_mem_to_shadow(start);
200 shadow_end = kasan_mem_to_shadow(end);
201
202 pr_info("Mapping kernel virtual memory block: %px-%px at shadow: %px-%px\n",
203 start, end, shadow_start, shadow_end);
204
205 kasan_pgd_populate((unsigned long)shadow_start & PAGE_MASK,
206 PAGE_ALIGN((unsigned long)shadow_end), false);
207 return 0;
208 }
209
210 void __init kasan_init(void)
211 {
212 phys_addr_t pa_start, pa_end;
213 u64 i;
214
215 /*
216 * We are going to perform proper setup of shadow memory.
217 *
218 * At first we should unmap early shadow (clear_pgds() call bellow).
219 * However, instrumented code can't execute without shadow memory.
220 *
221 * To keep the early shadow memory MMU tables around while setting up
222 * the proper shadow memory, we copy swapper_pg_dir (the initial page
223 * table) to tmp_pgd_table and use that to keep the early shadow memory
224 * mapped until the full shadow setup is finished. Then we swap back
225 * to the proper swapper_pg_dir.
226 */
227
228 memcpy(tmp_pgd_table, swapper_pg_dir, sizeof(tmp_pgd_table));
229 #ifdef CONFIG_ARM_LPAE
230 /* We need to be in the same PGD or this won't work */
231 BUILD_BUG_ON(pgd_index(KASAN_SHADOW_START) !=
232 pgd_index(KASAN_SHADOW_END));
233 memcpy(tmp_pmd_table,
234 (void*)pgd_page_vaddr(*pgd_offset_k(KASAN_SHADOW_START)),
235 sizeof(tmp_pmd_table));
236 set_pgd(&tmp_pgd_table[pgd_index(KASAN_SHADOW_START)],
237 __pgd(__pa(tmp_pmd_table) | PMD_TYPE_TABLE | L_PGD_SWAPPER));
238 #endif
239 cpu_switch_mm(tmp_pgd_table, &init_mm);
240 local_flush_tlb_all();
241
242 clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
243
244 if (!IS_ENABLED(CONFIG_KASAN_VMALLOC))
245 kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_START),
246 kasan_mem_to_shadow((void *)VMALLOC_END));
247
248 kasan_populate_early_shadow(kasan_mem_to_shadow((void *)VMALLOC_END),
249 kasan_mem_to_shadow((void *)-1UL) + 1);
250
251 for_each_mem_range(i, &pa_start, &pa_end) {
252 void *start = __va(pa_start);
253 void *end = __va(pa_end);
254
255 /* Do not attempt to shadow highmem */
256 if (pa_start >= arm_lowmem_limit) {
257 pr_info("Skip highmem block at %pa-%pa\n", &pa_start, &pa_end);
258 continue;
259 }
260 if (pa_end > arm_lowmem_limit) {
261 pr_info("Truncating shadow for memory block at %pa-%pa to lowmem region at %pa\n",
262 &pa_start, &pa_end, &arm_lowmem_limit);
263 end = __va(arm_lowmem_limit);
264 }
265 if (start >= end) {
266 pr_info("Skipping invalid memory block %pa-%pa (virtual %p-%p)\n",
267 &pa_start, &pa_end, start, end);
268 continue;
269 }
270
271 create_mapping(start, end);
272 }
273
274 /*
275 * 1. The module global variables are in MODULES_VADDR ~ MODULES_END,
276 * so we need to map this area if CONFIG_KASAN_VMALLOC=n. With
277 * VMALLOC support KASAN will manage this region dynamically,
278 * refer to kasan_populate_vmalloc() and ARM's implementation of
279 * module_alloc().
280 * 2. PKMAP_BASE ~ PKMAP_BASE+PMD_SIZE's shadow and MODULES_VADDR
281 * ~ MODULES_END's shadow is in the same PMD_SIZE, so we can't
282 * use kasan_populate_zero_shadow.
283 */
284 if (!IS_ENABLED(CONFIG_KASAN_VMALLOC) && IS_ENABLED(CONFIG_MODULES))
285 create_mapping((void *)MODULES_VADDR, (void *)(MODULES_END));
286 create_mapping((void *)PKMAP_BASE, (void *)(PKMAP_BASE + PMD_SIZE));
287
288 /*
289 * KAsan may reuse the contents of kasan_early_shadow_pte directly, so
290 * we should make sure that it maps the zero page read-only.
291 */
292 for (i = 0; i < PTRS_PER_PTE; i++)
293 set_pte_at(&init_mm, KASAN_SHADOW_START + i*PAGE_SIZE,
294 &kasan_early_shadow_pte[i],
295 pfn_pte(virt_to_pfn(kasan_early_shadow_page),
296 __pgprot(pgprot_val(PAGE_KERNEL)
297 | L_PTE_RDONLY)));
298
299 cpu_switch_mm(swapper_pg_dir, &init_mm);
300 local_flush_tlb_all();
301
302 memset(kasan_early_shadow_page, 0, PAGE_SIZE);
303 pr_info("Kernel address sanitizer initialized\n");
304 init_task.kasan_depth = 0;
305 }
306
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