1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * KMSAN shadow implementation.
4 *
5 * Copyright (C) 2017-2022 Google LLC
6 * Author: Alexander Potapenko <glider@google.com>
7 *
8 */
9
10 #include <asm/kmsan.h>
11 #include <asm/tlbflush.h>
12 #include <linux/cacheflush.h>
13 #include <linux/memblock.h>
14 #include <linux/mm_types.h>
15 #include <linux/slab.h>
16 #include <linux/smp.h>
17 #include <linux/stddef.h>
18
19 #include "../internal.h"
20 #include "kmsan.h"
21
22 #define shadow_page_for(page) ((page)->kmsan_shadow)
23
24 #define origin_page_for(page) ((page)->kmsan_origin)
25
26 static void *shadow_ptr_for(struct page *page)
27 {
28 return page_address(shadow_page_for(page));
29 }
30
31 static void *origin_ptr_for(struct page *page)
32 {
33 return page_address(origin_page_for(page));
34 }
35
36 static bool page_has_metadata(struct page *page)
37 {
38 return shadow_page_for(page) && origin_page_for(page);
39 }
40
41 static void set_no_shadow_origin_page(struct page *page)
42 {
43 shadow_page_for(page) = NULL;
44 origin_page_for(page) = NULL;
45 }
46
47 /*
48 * Dummy load and store pages to be used when the real metadata is unavailable.
49 * There are separate pages for loads and stores, so that every load returns a
50 * zero, and every store doesn't affect other loads.
51 */
52 static char dummy_load_page[PAGE_SIZE] __aligned(PAGE_SIZE);
53 static char dummy_store_page[PAGE_SIZE] __aligned(PAGE_SIZE);
54
55 static unsigned long vmalloc_meta(void *addr, bool is_origin)
56 {
57 unsigned long addr64 = (unsigned long)addr, off;
58
59 KMSAN_WARN_ON(is_origin && !IS_ALIGNED(addr64, KMSAN_ORIGIN_SIZE));
60 if (kmsan_internal_is_vmalloc_addr(addr)) {
61 off = addr64 - VMALLOC_START;
62 return off + (is_origin ? KMSAN_VMALLOC_ORIGIN_START :
63 KMSAN_VMALLOC_SHADOW_START);
64 }
65 if (kmsan_internal_is_module_addr(addr)) {
66 off = addr64 - MODULES_VADDR;
67 return off + (is_origin ? KMSAN_MODULES_ORIGIN_START :
68 KMSAN_MODULES_SHADOW_START);
69 }
70 return 0;
71 }
72
73 static struct page *virt_to_page_or_null(void *vaddr)
74 {
75 if (kmsan_virt_addr_valid(vaddr))
76 return virt_to_page(vaddr);
77 else
78 return NULL;
79 }
80
81 struct shadow_origin_ptr kmsan_get_shadow_origin_ptr(void *address, u64 size,
82 bool store)
83 {
84 struct shadow_origin_ptr ret;
85 void *shadow;
86
87 /*
88 * Even if we redirect this memory access to the dummy page, it will
89 * go out of bounds.
90 */
91 KMSAN_WARN_ON(size > PAGE_SIZE);
92
93 if (!kmsan_enabled)
94 goto return_dummy;
95
96 KMSAN_WARN_ON(!kmsan_metadata_is_contiguous(address, size));
97 shadow = kmsan_get_metadata(address, KMSAN_META_SHADOW);
98 if (!shadow)
99 goto return_dummy;
100
101 ret.shadow = shadow;
102 ret.origin = kmsan_get_metadata(address, KMSAN_META_ORIGIN);
103 return ret;
104
105 return_dummy:
106 if (store) {
107 /* Ignore this store. */
108 ret.shadow = dummy_store_page;
109 ret.origin = dummy_store_page;
110 } else {
111 /* This load will return zero. */
112 ret.shadow = dummy_load_page;
113 ret.origin = dummy_load_page;
114 }
115 return ret;
116 }
117
118 /*
119 * Obtain the shadow or origin pointer for the given address, or NULL if there's
120 * none. The caller must check the return value for being non-NULL if needed.
121 * The return value of this function should not depend on whether we're in the
122 * runtime or not.
123 */
124 void *kmsan_get_metadata(void *address, bool is_origin)
125 {
126 u64 addr = (u64)address, off;
127 struct page *page;
128 void *ret;
129
130 if (is_origin)
131 addr = ALIGN_DOWN(addr, KMSAN_ORIGIN_SIZE);
132 address = (void *)addr;
133 if (kmsan_internal_is_vmalloc_addr(address) ||
134 kmsan_internal_is_module_addr(address))
135 return (void *)vmalloc_meta(address, is_origin);
136
137 ret = arch_kmsan_get_meta_or_null(address, is_origin);
138 if (ret)
139 return ret;
140
141 page = virt_to_page_or_null(address);
142 if (!page)
143 return NULL;
144 if (!page_has_metadata(page))
145 return NULL;
146 off = offset_in_page(addr);
147
148 return (is_origin ? origin_ptr_for(page) : shadow_ptr_for(page)) + off;
149 }
150
151 void kmsan_copy_page_meta(struct page *dst, struct page *src)
152 {
153 if (!kmsan_enabled || kmsan_in_runtime())
154 return;
155 if (!dst || !page_has_metadata(dst))
156 return;
157 if (!src || !page_has_metadata(src)) {
158 kmsan_internal_unpoison_memory(page_address(dst), PAGE_SIZE,
159 /*checked*/ false);
160 return;
161 }
162
163 kmsan_enter_runtime();
164 __memcpy(shadow_ptr_for(dst), shadow_ptr_for(src), PAGE_SIZE);
165 __memcpy(origin_ptr_for(dst), origin_ptr_for(src), PAGE_SIZE);
166 kmsan_leave_runtime();
167 }
168 EXPORT_SYMBOL(kmsan_copy_page_meta);
169
170 void kmsan_alloc_page(struct page *page, unsigned int order, gfp_t flags)
171 {
172 bool initialized = (flags & __GFP_ZERO) || !kmsan_enabled;
173 struct page *shadow, *origin;
174 depot_stack_handle_t handle;
175 int pages = 1 << order;
176
177 if (!page)
178 return;
179
180 shadow = shadow_page_for(page);
181 origin = origin_page_for(page);
182
183 if (initialized) {
184 __memset(page_address(shadow), 0, PAGE_SIZE * pages);
185 __memset(page_address(origin), 0, PAGE_SIZE * pages);
186 return;
187 }
188
189 /* Zero pages allocated by the runtime should also be initialized. */
190 if (kmsan_in_runtime())
191 return;
192
193 __memset(page_address(shadow), -1, PAGE_SIZE * pages);
194 kmsan_enter_runtime();
195 handle = kmsan_save_stack_with_flags(flags, /*extra_bits*/ 0);
196 kmsan_leave_runtime();
197 /*
198 * Addresses are page-aligned, pages are contiguous, so it's ok
199 * to just fill the origin pages with @handle.
200 */
201 for (int i = 0; i < PAGE_SIZE * pages / sizeof(handle); i++)
202 ((depot_stack_handle_t *)page_address(origin))[i] = handle;
203 }
204
205 void kmsan_free_page(struct page *page, unsigned int order)
206 {
207 if (!kmsan_enabled || kmsan_in_runtime())
208 return;
209 kmsan_enter_runtime();
210 kmsan_internal_poison_memory(page_address(page),
211 page_size(page),
212 GFP_KERNEL,
213 KMSAN_POISON_CHECK | KMSAN_POISON_FREE);
214 kmsan_leave_runtime();
215 }
216
217 int kmsan_vmap_pages_range_noflush(unsigned long start, unsigned long end,
218 pgprot_t prot, struct page **pages,
219 unsigned int page_shift)
220 {
221 unsigned long shadow_start, origin_start, shadow_end, origin_end;
222 struct page **s_pages, **o_pages;
223 int nr, mapped, err = 0;
224
225 if (!kmsan_enabled)
226 return 0;
227
228 shadow_start = vmalloc_meta((void *)start, KMSAN_META_SHADOW);
229 shadow_end = vmalloc_meta((void *)end, KMSAN_META_SHADOW);
230 if (!shadow_start)
231 return 0;
232
233 nr = (end - start) / PAGE_SIZE;
234 s_pages = kcalloc(nr, sizeof(*s_pages), GFP_KERNEL);
235 o_pages = kcalloc(nr, sizeof(*o_pages), GFP_KERNEL);
236 if (!s_pages || !o_pages) {
237 err = -ENOMEM;
238 goto ret;
239 }
240 for (int i = 0; i < nr; i++) {
241 s_pages[i] = shadow_page_for(pages[i]);
242 o_pages[i] = origin_page_for(pages[i]);
243 }
244 prot = PAGE_KERNEL;
245
246 origin_start = vmalloc_meta((void *)start, KMSAN_META_ORIGIN);
247 origin_end = vmalloc_meta((void *)end, KMSAN_META_ORIGIN);
248 kmsan_enter_runtime();
249 mapped = __vmap_pages_range_noflush(shadow_start, shadow_end, prot,
250 s_pages, page_shift);
251 if (mapped) {
252 err = mapped;
253 goto ret;
254 }
255 mapped = __vmap_pages_range_noflush(origin_start, origin_end, prot,
256 o_pages, page_shift);
257 if (mapped) {
258 err = mapped;
259 goto ret;
260 }
261 kmsan_leave_runtime();
262 flush_tlb_kernel_range(shadow_start, shadow_end);
263 flush_tlb_kernel_range(origin_start, origin_end);
264 flush_cache_vmap(shadow_start, shadow_end);
265 flush_cache_vmap(origin_start, origin_end);
266
267 ret:
268 kfree(s_pages);
269 kfree(o_pages);
270 return err;
271 }
272
273 /* Allocate metadata for pages allocated at boot time. */
274 void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
275 {
276 struct page *shadow_p, *origin_p;
277 void *shadow, *origin;
278 struct page *page;
279 u64 size;
280
281 start = (void *)PAGE_ALIGN_DOWN((u64)start);
282 size = PAGE_ALIGN((u64)end - (u64)start);
283 shadow = memblock_alloc(size, PAGE_SIZE);
284 origin = memblock_alloc(size, PAGE_SIZE);
285
286 if (!shadow || !origin)
287 panic("%s: Failed to allocate metadata memory for early boot range of size %llu",
288 __func__, size);
289
290 for (u64 addr = 0; addr < size; addr += PAGE_SIZE) {
291 page = virt_to_page_or_null((char *)start + addr);
292 shadow_p = virt_to_page((char *)shadow + addr);
293 set_no_shadow_origin_page(shadow_p);
294 shadow_page_for(page) = shadow_p;
295 origin_p = virt_to_page((char *)origin + addr);
296 set_no_shadow_origin_page(origin_p);
297 origin_page_for(page) = origin_p;
298 }
299 }
300
301 void kmsan_setup_meta(struct page *page, struct page *shadow,
302 struct page *origin, int order)
303 {
304 for (int i = 0; i < (1 << order); i++) {
305 set_no_shadow_origin_page(&shadow[i]);
306 set_no_shadow_origin_page(&origin[i]);
307 shadow_page_for(&page[i]) = &shadow[i];
308 origin_page_for(&page[i]) = &origin[i];
309 }
310 }
311
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