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d65e8da9 RT |
1 | // SPDX-License-Identifier: BSD-2-Clause |
2 | /* | |
3 | * Copyright (C) 2017 The Android Open Source Project | |
4 | */ | |
5 | #include <common.h> | |
6 | #include <android_ab.h> | |
7 | #include <android_bootloader_message.h> | |
e6f6f9e6 | 8 | #include <blk.h> |
f7ae49fc | 9 | #include <log.h> |
336d4615 | 10 | #include <malloc.h> |
e6f6f9e6 | 11 | #include <part.h> |
d65e8da9 | 12 | #include <memalign.h> |
e6f6f9e6 | 13 | #include <linux/err.h> |
d65e8da9 | 14 | #include <u-boot/crc.h> |
3db71108 | 15 | #include <u-boot/crc.h> |
d65e8da9 RT |
16 | |
17 | /** | |
18 | * Compute the CRC-32 of the bootloader control struct. | |
19 | * | |
20 | * Only the bytes up to the crc32_le field are considered for the CRC-32 | |
21 | * calculation. | |
22 | * | |
23 | * @param[in] abc bootloader control block | |
24 | * | |
25 | * @return crc32 sum | |
26 | */ | |
27 | static uint32_t ab_control_compute_crc(struct bootloader_control *abc) | |
28 | { | |
29 | return crc32(0, (void *)abc, offsetof(typeof(*abc), crc32_le)); | |
30 | } | |
31 | ||
32 | /** | |
33 | * Initialize bootloader_control to the default value. | |
34 | * | |
35 | * It allows us to boot all slots in order from the first one. This value | |
36 | * should be used when the bootloader message is corrupted, but not when | |
37 | * a valid message indicates that all slots are unbootable. | |
38 | * | |
39 | * @param[in] abc bootloader control block | |
40 | * | |
41 | * @return 0 on success and a negative on error | |
42 | */ | |
43 | static int ab_control_default(struct bootloader_control *abc) | |
44 | { | |
45 | int i; | |
46 | const struct slot_metadata metadata = { | |
47 | .priority = 15, | |
48 | .tries_remaining = 7, | |
49 | .successful_boot = 0, | |
50 | .verity_corrupted = 0, | |
51 | .reserved = 0 | |
52 | }; | |
53 | ||
54 | if (!abc) | |
55 | return -EFAULT; | |
56 | ||
57 | memcpy(abc->slot_suffix, "a\0\0\0", 4); | |
58 | abc->magic = BOOT_CTRL_MAGIC; | |
59 | abc->version = BOOT_CTRL_VERSION; | |
60 | abc->nb_slot = NUM_SLOTS; | |
61 | memset(abc->reserved0, 0, sizeof(abc->reserved0)); | |
62 | for (i = 0; i < abc->nb_slot; ++i) | |
63 | abc->slot_info[i] = metadata; | |
64 | ||
65 | memset(abc->reserved1, 0, sizeof(abc->reserved1)); | |
66 | abc->crc32_le = ab_control_compute_crc(abc); | |
67 | ||
68 | return 0; | |
69 | } | |
70 | ||
71 | /** | |
72 | * Load the boot_control struct from disk into newly allocated memory. | |
73 | * | |
74 | * This function allocates and returns an integer number of disk blocks, | |
75 | * based on the block size of the passed device to help performing a | |
76 | * read-modify-write operation on the boot_control struct. | |
77 | * The boot_control struct offset (2 KiB) must be a multiple of the device | |
78 | * block size, for simplicity. | |
79 | * | |
80 | * @param[in] dev_desc Device where to read the boot_control struct from | |
81 | * @param[in] part_info Partition in 'dev_desc' where to read from, normally | |
82 | * the "misc" partition should be used | |
83 | * @param[out] pointer to pointer to bootloader_control data | |
84 | * @return 0 on success and a negative on error | |
85 | */ | |
86 | static int ab_control_create_from_disk(struct blk_desc *dev_desc, | |
0528979f | 87 | const struct disk_partition *part_info, |
d65e8da9 RT |
88 | struct bootloader_control **abc) |
89 | { | |
90 | ulong abc_offset, abc_blocks, ret; | |
91 | ||
92 | abc_offset = offsetof(struct bootloader_message_ab, slot_suffix); | |
93 | if (abc_offset % part_info->blksz) { | |
94 | log_err("ANDROID: Boot control block not block aligned.\n"); | |
95 | return -EINVAL; | |
96 | } | |
97 | abc_offset /= part_info->blksz; | |
98 | ||
99 | abc_blocks = DIV_ROUND_UP(sizeof(struct bootloader_control), | |
100 | part_info->blksz); | |
101 | if (abc_offset + abc_blocks > part_info->size) { | |
102 | log_err("ANDROID: boot control partition too small. Need at"); | |
103 | log_err(" least %lu blocks but have %lu blocks.\n", | |
104 | abc_offset + abc_blocks, part_info->size); | |
105 | return -EINVAL; | |
106 | } | |
107 | *abc = malloc_cache_aligned(abc_blocks * part_info->blksz); | |
108 | if (!*abc) | |
109 | return -ENOMEM; | |
110 | ||
111 | ret = blk_dread(dev_desc, part_info->start + abc_offset, abc_blocks, | |
112 | *abc); | |
113 | if (IS_ERR_VALUE(ret)) { | |
114 | log_err("ANDROID: Could not read from boot ctrl partition\n"); | |
115 | free(*abc); | |
116 | return -EIO; | |
117 | } | |
118 | ||
119 | log_debug("ANDROID: Loaded ABC, %lu blocks\n", abc_blocks); | |
120 | ||
121 | return 0; | |
122 | } | |
123 | ||
124 | /** | |
125 | * Store the loaded boot_control block. | |
126 | * | |
127 | * Store back to the same location it was read from with | |
128 | * ab_control_create_from_misc(). | |
129 | * | |
130 | * @param[in] dev_desc Device where we should write the boot_control struct | |
131 | * @param[in] part_info Partition on the 'dev_desc' where to write | |
132 | * @param[in] abc Pointer to the boot control struct and the extra bytes after | |
133 | * it up to the nearest block boundary | |
134 | * @return 0 on success and a negative on error | |
135 | */ | |
136 | static int ab_control_store(struct blk_desc *dev_desc, | |
0528979f | 137 | const struct disk_partition *part_info, |
d65e8da9 RT |
138 | struct bootloader_control *abc) |
139 | { | |
140 | ulong abc_offset, abc_blocks, ret; | |
141 | ||
142 | abc_offset = offsetof(struct bootloader_message_ab, slot_suffix) / | |
143 | part_info->blksz; | |
144 | abc_blocks = DIV_ROUND_UP(sizeof(struct bootloader_control), | |
145 | part_info->blksz); | |
146 | ret = blk_dwrite(dev_desc, part_info->start + abc_offset, abc_blocks, | |
147 | abc); | |
148 | if (IS_ERR_VALUE(ret)) { | |
149 | log_err("ANDROID: Could not write back the misc partition\n"); | |
150 | return -EIO; | |
151 | } | |
152 | ||
153 | return 0; | |
154 | } | |
155 | ||
156 | /** | |
157 | * Compare two slots. | |
158 | * | |
159 | * The function determines slot which is should we boot from among the two. | |
160 | * | |
161 | * @param[in] a The first bootable slot metadata | |
162 | * @param[in] b The second bootable slot metadata | |
163 | * @return Negative if the slot "a" is better, positive of the slot "b" is | |
164 | * better or 0 if they are equally good. | |
165 | */ | |
166 | static int ab_compare_slots(const struct slot_metadata *a, | |
167 | const struct slot_metadata *b) | |
168 | { | |
169 | /* Higher priority is better */ | |
170 | if (a->priority != b->priority) | |
171 | return b->priority - a->priority; | |
172 | ||
173 | /* Higher successful_boot value is better, in case of same priority */ | |
174 | if (a->successful_boot != b->successful_boot) | |
175 | return b->successful_boot - a->successful_boot; | |
176 | ||
177 | /* Higher tries_remaining is better to ensure round-robin */ | |
178 | if (a->tries_remaining != b->tries_remaining) | |
179 | return b->tries_remaining - a->tries_remaining; | |
180 | ||
181 | return 0; | |
182 | } | |
183 | ||
0528979f | 184 | int ab_select_slot(struct blk_desc *dev_desc, struct disk_partition *part_info) |
d65e8da9 RT |
185 | { |
186 | struct bootloader_control *abc = NULL; | |
187 | u32 crc32_le; | |
188 | int slot, i, ret; | |
189 | bool store_needed = false; | |
190 | char slot_suffix[4]; | |
191 | ||
192 | ret = ab_control_create_from_disk(dev_desc, part_info, &abc); | |
193 | if (ret < 0) { | |
194 | /* | |
195 | * This condition represents an actual problem with the code or | |
196 | * the board setup, like an invalid partition information. | |
197 | * Signal a repair mode and do not try to boot from either slot. | |
198 | */ | |
199 | return ret; | |
200 | } | |
201 | ||
202 | crc32_le = ab_control_compute_crc(abc); | |
203 | if (abc->crc32_le != crc32_le) { | |
204 | log_err("ANDROID: Invalid CRC-32 (expected %.8x, found %.8x),", | |
205 | crc32_le, abc->crc32_le); | |
206 | log_err("re-initializing A/B metadata.\n"); | |
207 | ||
208 | ret = ab_control_default(abc); | |
209 | if (ret < 0) { | |
210 | free(abc); | |
211 | return -ENODATA; | |
212 | } | |
213 | store_needed = true; | |
214 | } | |
215 | ||
216 | if (abc->magic != BOOT_CTRL_MAGIC) { | |
217 | log_err("ANDROID: Unknown A/B metadata: %.8x\n", abc->magic); | |
218 | free(abc); | |
219 | return -ENODATA; | |
220 | } | |
221 | ||
222 | if (abc->version > BOOT_CTRL_VERSION) { | |
223 | log_err("ANDROID: Unsupported A/B metadata version: %.8x\n", | |
224 | abc->version); | |
225 | free(abc); | |
226 | return -ENODATA; | |
227 | } | |
228 | ||
229 | /* | |
230 | * At this point a valid boot control metadata is stored in abc, | |
231 | * followed by other reserved data in the same block. We select a with | |
232 | * the higher priority slot that | |
233 | * - is not marked as corrupted and | |
234 | * - either has tries_remaining > 0 or successful_boot is true. | |
235 | * If the selected slot has a false successful_boot, we also decrement | |
236 | * the tries_remaining until it eventually becomes unbootable because | |
237 | * tries_remaining reaches 0. This mechanism produces a bootloader | |
238 | * induced rollback, typically right after a failed update. | |
239 | */ | |
240 | ||
241 | /* Safety check: limit the number of slots. */ | |
242 | if (abc->nb_slot > ARRAY_SIZE(abc->slot_info)) { | |
243 | abc->nb_slot = ARRAY_SIZE(abc->slot_info); | |
244 | store_needed = true; | |
245 | } | |
246 | ||
247 | slot = -1; | |
248 | for (i = 0; i < abc->nb_slot; ++i) { | |
249 | if (abc->slot_info[i].verity_corrupted || | |
250 | !abc->slot_info[i].tries_remaining) { | |
251 | log_debug("ANDROID: unbootable slot %d tries: %d, ", | |
252 | i, abc->slot_info[i].tries_remaining); | |
253 | log_debug("corrupt: %d\n", | |
254 | abc->slot_info[i].verity_corrupted); | |
255 | continue; | |
256 | } | |
257 | log_debug("ANDROID: bootable slot %d pri: %d, tries: %d, ", | |
258 | i, abc->slot_info[i].priority, | |
259 | abc->slot_info[i].tries_remaining); | |
260 | log_debug("corrupt: %d, successful: %d\n", | |
261 | abc->slot_info[i].verity_corrupted, | |
262 | abc->slot_info[i].successful_boot); | |
263 | ||
264 | if (slot < 0 || | |
265 | ab_compare_slots(&abc->slot_info[i], | |
266 | &abc->slot_info[slot]) < 0) { | |
267 | slot = i; | |
268 | } | |
269 | } | |
270 | ||
271 | if (slot >= 0 && !abc->slot_info[slot].successful_boot) { | |
272 | log_err("ANDROID: Attempting slot %c, tries remaining %d\n", | |
273 | BOOT_SLOT_NAME(slot), | |
274 | abc->slot_info[slot].tries_remaining); | |
275 | abc->slot_info[slot].tries_remaining--; | |
276 | store_needed = true; | |
277 | } | |
278 | ||
279 | if (slot >= 0) { | |
280 | /* | |
281 | * Legacy user-space requires this field to be set in the BCB. | |
282 | * Newer releases load this slot suffix from the command line | |
283 | * or the device tree. | |
284 | */ | |
285 | memset(slot_suffix, 0, sizeof(slot_suffix)); | |
286 | slot_suffix[0] = BOOT_SLOT_NAME(slot); | |
287 | if (memcmp(abc->slot_suffix, slot_suffix, | |
288 | sizeof(slot_suffix))) { | |
289 | memcpy(abc->slot_suffix, slot_suffix, | |
290 | sizeof(slot_suffix)); | |
291 | store_needed = true; | |
292 | } | |
293 | } | |
294 | ||
295 | if (store_needed) { | |
296 | abc->crc32_le = ab_control_compute_crc(abc); | |
297 | ab_control_store(dev_desc, part_info, abc); | |
298 | } | |
299 | free(abc); | |
300 | ||
301 | if (slot < 0) | |
302 | return -EINVAL; | |
303 | ||
304 | return slot; | |
305 | } |