[u-boot.git] / common / android_ab.c

// SPDX-License-Identifier: BSD-2-Clause
/*
 * Copyright (C) 2017 The Android Open Source Project
 */
#include <common.h>
#include <android_ab.h>
#include <android_bootloader_message.h>
#include <linux/err.h>
#include <memalign.h>
#include <u-boot/crc.h>

/**
 * Compute the CRC-32 of the bootloader control struct.
 *
 * Only the bytes up to the crc32_le field are considered for the CRC-32
 * calculation.
 *
 * @param[in] abc bootloader control block
 *
 * @return crc32 sum
 */
static uint32_t ab_control_compute_crc(struct bootloader_control *abc)
{
	return crc32(0, (void *)abc, offsetof(typeof(*abc), crc32_le));
}

/**
 * Initialize bootloader_control to the default value.
 *
 * It allows us to boot all slots in order from the first one. This value
 * should be used when the bootloader message is corrupted, but not when
 * a valid message indicates that all slots are unbootable.
 *
 * @param[in] abc bootloader control block
 *
 * @return 0 on success and a negative on error
 */
static int ab_control_default(struct bootloader_control *abc)
{
	int i;
	const struct slot_metadata metadata = {
		.priority = 15,
		.tries_remaining = 7,
		.successful_boot = 0,
		.verity_corrupted = 0,
		.reserved = 0
	};

	if (!abc)
		return -EFAULT;

	memcpy(abc->slot_suffix, "a\0\0\0", 4);
	abc->magic = BOOT_CTRL_MAGIC;
	abc->version = BOOT_CTRL_VERSION;
	abc->nb_slot = NUM_SLOTS;
	memset(abc->reserved0, 0, sizeof(abc->reserved0));
	for (i = 0; i < abc->nb_slot; ++i)
		abc->slot_info[i] = metadata;

	memset(abc->reserved1, 0, sizeof(abc->reserved1));
	abc->crc32_le = ab_control_compute_crc(abc);

	return 0;
}

/**
 * Load the boot_control struct from disk into newly allocated memory.
 *
 * This function allocates and returns an integer number of disk blocks,
 * based on the block size of the passed device to help performing a
 * read-modify-write operation on the boot_control struct.
 * The boot_control struct offset (2 KiB) must be a multiple of the device
 * block size, for simplicity.
 *
 * @param[in] dev_desc Device where to read the boot_control struct from
 * @param[in] part_info Partition in 'dev_desc' where to read from, normally
 *			the "misc" partition should be used
 * @param[out] pointer to pointer to bootloader_control data
 * @return 0 on success and a negative on error
 */
static int ab_control_create_from_disk(struct blk_desc *dev_desc,
				       const disk_partition_t *part_info,
				       struct bootloader_control **abc)
{
	ulong abc_offset, abc_blocks, ret;

	abc_offset = offsetof(struct bootloader_message_ab, slot_suffix);
	if (abc_offset % part_info->blksz) {
		log_err("ANDROID: Boot control block not block aligned.\n");
		return -EINVAL;
	}
	abc_offset /= part_info->blksz;

	abc_blocks = DIV_ROUND_UP(sizeof(struct bootloader_control),
				  part_info->blksz);
	if (abc_offset + abc_blocks > part_info->size) {
		log_err("ANDROID: boot control partition too small. Need at");
		log_err(" least %lu blocks but have %lu blocks.\n",
			abc_offset + abc_blocks, part_info->size);
		return -EINVAL;
	}
	*abc = malloc_cache_aligned(abc_blocks * part_info->blksz);
	if (!*abc)
		return -ENOMEM;

	ret = blk_dread(dev_desc, part_info->start + abc_offset, abc_blocks,
			*abc);
	if (IS_ERR_VALUE(ret)) {
		log_err("ANDROID: Could not read from boot ctrl partition\n");
		free(*abc);
		return -EIO;
	}

	log_debug("ANDROID: Loaded ABC, %lu blocks\n", abc_blocks);

	return 0;
}

/**
 * Store the loaded boot_control block.
 *
 * Store back to the same location it was read from with
 * ab_control_create_from_misc().
 *
 * @param[in] dev_desc Device where we should write the boot_control struct
 * @param[in] part_info Partition on the 'dev_desc' where to write
 * @param[in] abc Pointer to the boot control struct and the extra bytes after
 *                it up to the nearest block boundary
 * @return 0 on success and a negative on error
 */
static int ab_control_store(struct blk_desc *dev_desc,
			    const disk_partition_t *part_info,
			    struct bootloader_control *abc)
{
	ulong abc_offset, abc_blocks, ret;

	abc_offset = offsetof(struct bootloader_message_ab, slot_suffix) /
		     part_info->blksz;
	abc_blocks = DIV_ROUND_UP(sizeof(struct bootloader_control),
				  part_info->blksz);
	ret = blk_dwrite(dev_desc, part_info->start + abc_offset, abc_blocks,
			 abc);
	if (IS_ERR_VALUE(ret)) {
		log_err("ANDROID: Could not write back the misc partition\n");
		return -EIO;
	}

	return 0;
}

/**
 * Compare two slots.
 *
 * The function determines slot which is should we boot from among the two.
 *
 * @param[in] a The first bootable slot metadata
 * @param[in] b The second bootable slot metadata
 * @return Negative if the slot "a" is better, positive of the slot "b" is
 *         better or 0 if they are equally good.
 */
static int ab_compare_slots(const struct slot_metadata *a,
			    const struct slot_metadata *b)
{
	/* Higher priority is better */
	if (a->priority != b->priority)
		return b->priority - a->priority;

	/* Higher successful_boot value is better, in case of same priority */
	if (a->successful_boot != b->successful_boot)
		return b->successful_boot - a->successful_boot;

	/* Higher tries_remaining is better to ensure round-robin */
	if (a->tries_remaining != b->tries_remaining)
		return b->tries_remaining - a->tries_remaining;

	return 0;
}

int ab_select_slot(struct blk_desc *dev_desc, disk_partition_t *part_info)
{
	struct bootloader_control *abc = NULL;
	u32 crc32_le;
	int slot, i, ret;
	bool store_needed = false;
	char slot_suffix[4];

	ret = ab_control_create_from_disk(dev_desc, part_info, &abc);
	if (ret < 0) {
		/*
		 * This condition represents an actual problem with the code or
		 * the board setup, like an invalid partition information.
		 * Signal a repair mode and do not try to boot from either slot.
		 */
		return ret;
	}

	crc32_le = ab_control_compute_crc(abc);
	if (abc->crc32_le != crc32_le) {
		log_err("ANDROID: Invalid CRC-32 (expected %.8x, found %.8x),",
			crc32_le, abc->crc32_le);
		log_err("re-initializing A/B metadata.\n");

		ret = ab_control_default(abc);
		if (ret < 0) {
			free(abc);
			return -ENODATA;
		}
		store_needed = true;
	}

	if (abc->magic != BOOT_CTRL_MAGIC) {
		log_err("ANDROID: Unknown A/B metadata: %.8x\n", abc->magic);
		free(abc);
		return -ENODATA;
	}

	if (abc->version > BOOT_CTRL_VERSION) {
		log_err("ANDROID: Unsupported A/B metadata version: %.8x\n",
			abc->version);
		free(abc);
		return -ENODATA;
	}

	/*
	 * At this point a valid boot control metadata is stored in abc,
	 * followed by other reserved data in the same block. We select a with
	 * the higher priority slot that
	 *  - is not marked as corrupted and
	 *  - either has tries_remaining > 0 or successful_boot is true.
	 * If the selected slot has a false successful_boot, we also decrement
	 * the tries_remaining until it eventually becomes unbootable because
	 * tries_remaining reaches 0. This mechanism produces a bootloader
	 * induced rollback, typically right after a failed update.
	 */

	/* Safety check: limit the number of slots. */
	if (abc->nb_slot > ARRAY_SIZE(abc->slot_info)) {
		abc->nb_slot = ARRAY_SIZE(abc->slot_info);
		store_needed = true;
	}

	slot = -1;
	for (i = 0; i < abc->nb_slot; ++i) {
		if (abc->slot_info[i].verity_corrupted ||
		    !abc->slot_info[i].tries_remaining) {
			log_debug("ANDROID: unbootable slot %d tries: %d, ",
				  i, abc->slot_info[i].tries_remaining);
			log_debug("corrupt: %d\n",
				  abc->slot_info[i].verity_corrupted);
			continue;
		}
		log_debug("ANDROID: bootable slot %d pri: %d, tries: %d, ",
			  i, abc->slot_info[i].priority,
			  abc->slot_info[i].tries_remaining);
		log_debug("corrupt: %d, successful: %d\n",
			  abc->slot_info[i].verity_corrupted,
			  abc->slot_info[i].successful_boot);

		if (slot < 0 ||
		    ab_compare_slots(&abc->slot_info[i],
				     &abc->slot_info[slot]) < 0) {
			slot = i;
		}
	}

	if (slot >= 0 && !abc->slot_info[slot].successful_boot) {
		log_err("ANDROID: Attempting slot %c, tries remaining %d\n",
			BOOT_SLOT_NAME(slot),
			abc->slot_info[slot].tries_remaining);
		abc->slot_info[slot].tries_remaining--;
		store_needed = true;
	}

	if (slot >= 0) {
		/*
		 * Legacy user-space requires this field to be set in the BCB.
		 * Newer releases load this slot suffix from the command line
		 * or the device tree.
		 */
		memset(slot_suffix, 0, sizeof(slot_suffix));
		slot_suffix[0] = BOOT_SLOT_NAME(slot);
		if (memcmp(abc->slot_suffix, slot_suffix,
			   sizeof(slot_suffix))) {
			memcpy(abc->slot_suffix, slot_suffix,
			       sizeof(slot_suffix));
			store_needed = true;
		}
	}

	if (store_needed) {
		abc->crc32_le = ab_control_compute_crc(abc);
		ab_control_store(dev_desc, part_info, abc);
	}
	free(abc);

	if (slot < 0)
		return -EINVAL;

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