mirror of
https://github.com/brain-hackers/u-boot-brain
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306 lines
8.7 KiB
C
306 lines
8.7 KiB
C
// SPDX-License-Identifier: BSD-2-Clause
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/*
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* Copyright (C) 2017 The Android Open Source Project
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*/
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#include <common.h>
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#include <android_ab.h>
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#include <android_bootloader_message.h>
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#include <blk.h>
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#include <log.h>
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#include <malloc.h>
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#include <part.h>
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#include <memalign.h>
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#include <linux/err.h>
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#include <u-boot/crc.h>
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#include <u-boot/crc.h>
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/**
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* Compute the CRC-32 of the bootloader control struct.
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*
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* Only the bytes up to the crc32_le field are considered for the CRC-32
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* calculation.
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*
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* @param[in] abc bootloader control block
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*
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* @return crc32 sum
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*/
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static uint32_t ab_control_compute_crc(struct bootloader_control *abc)
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{
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return crc32(0, (void *)abc, offsetof(typeof(*abc), crc32_le));
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}
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/**
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* Initialize bootloader_control to the default value.
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*
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* It allows us to boot all slots in order from the first one. This value
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* should be used when the bootloader message is corrupted, but not when
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* a valid message indicates that all slots are unbootable.
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*
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* @param[in] abc bootloader control block
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*
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* @return 0 on success and a negative on error
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*/
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static int ab_control_default(struct bootloader_control *abc)
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{
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int i;
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const struct slot_metadata metadata = {
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.priority = 15,
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.tries_remaining = 7,
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.successful_boot = 0,
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.verity_corrupted = 0,
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.reserved = 0
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};
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if (!abc)
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return -EFAULT;
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memcpy(abc->slot_suffix, "a\0\0\0", 4);
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abc->magic = BOOT_CTRL_MAGIC;
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abc->version = BOOT_CTRL_VERSION;
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abc->nb_slot = NUM_SLOTS;
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memset(abc->reserved0, 0, sizeof(abc->reserved0));
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for (i = 0; i < abc->nb_slot; ++i)
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abc->slot_info[i] = metadata;
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memset(abc->reserved1, 0, sizeof(abc->reserved1));
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abc->crc32_le = ab_control_compute_crc(abc);
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return 0;
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}
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/**
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* Load the boot_control struct from disk into newly allocated memory.
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*
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* This function allocates and returns an integer number of disk blocks,
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* based on the block size of the passed device to help performing a
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* read-modify-write operation on the boot_control struct.
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* The boot_control struct offset (2 KiB) must be a multiple of the device
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* block size, for simplicity.
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*
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* @param[in] dev_desc Device where to read the boot_control struct from
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* @param[in] part_info Partition in 'dev_desc' where to read from, normally
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* the "misc" partition should be used
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* @param[out] pointer to pointer to bootloader_control data
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* @return 0 on success and a negative on error
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*/
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static int ab_control_create_from_disk(struct blk_desc *dev_desc,
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const struct disk_partition *part_info,
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struct bootloader_control **abc)
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{
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ulong abc_offset, abc_blocks, ret;
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abc_offset = offsetof(struct bootloader_message_ab, slot_suffix);
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if (abc_offset % part_info->blksz) {
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log_err("ANDROID: Boot control block not block aligned.\n");
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return -EINVAL;
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}
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abc_offset /= part_info->blksz;
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abc_blocks = DIV_ROUND_UP(sizeof(struct bootloader_control),
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part_info->blksz);
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if (abc_offset + abc_blocks > part_info->size) {
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log_err("ANDROID: boot control partition too small. Need at");
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log_err(" least %lu blocks but have %lu blocks.\n",
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abc_offset + abc_blocks, part_info->size);
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return -EINVAL;
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}
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*abc = malloc_cache_aligned(abc_blocks * part_info->blksz);
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if (!*abc)
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return -ENOMEM;
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ret = blk_dread(dev_desc, part_info->start + abc_offset, abc_blocks,
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*abc);
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if (IS_ERR_VALUE(ret)) {
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log_err("ANDROID: Could not read from boot ctrl partition\n");
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free(*abc);
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return -EIO;
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}
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log_debug("ANDROID: Loaded ABC, %lu blocks\n", abc_blocks);
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return 0;
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}
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/**
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* Store the loaded boot_control block.
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*
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* Store back to the same location it was read from with
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* ab_control_create_from_misc().
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*
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* @param[in] dev_desc Device where we should write the boot_control struct
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* @param[in] part_info Partition on the 'dev_desc' where to write
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* @param[in] abc Pointer to the boot control struct and the extra bytes after
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* it up to the nearest block boundary
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* @return 0 on success and a negative on error
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*/
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static int ab_control_store(struct blk_desc *dev_desc,
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const struct disk_partition *part_info,
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struct bootloader_control *abc)
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{
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ulong abc_offset, abc_blocks, ret;
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abc_offset = offsetof(struct bootloader_message_ab, slot_suffix) /
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part_info->blksz;
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abc_blocks = DIV_ROUND_UP(sizeof(struct bootloader_control),
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part_info->blksz);
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ret = blk_dwrite(dev_desc, part_info->start + abc_offset, abc_blocks,
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abc);
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if (IS_ERR_VALUE(ret)) {
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log_err("ANDROID: Could not write back the misc partition\n");
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return -EIO;
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}
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return 0;
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}
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/**
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* Compare two slots.
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*
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* The function determines slot which is should we boot from among the two.
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*
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* @param[in] a The first bootable slot metadata
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* @param[in] b The second bootable slot metadata
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* @return Negative if the slot "a" is better, positive of the slot "b" is
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* better or 0 if they are equally good.
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*/
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static int ab_compare_slots(const struct slot_metadata *a,
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const struct slot_metadata *b)
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{
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/* Higher priority is better */
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if (a->priority != b->priority)
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return b->priority - a->priority;
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/* Higher successful_boot value is better, in case of same priority */
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if (a->successful_boot != b->successful_boot)
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return b->successful_boot - a->successful_boot;
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/* Higher tries_remaining is better to ensure round-robin */
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if (a->tries_remaining != b->tries_remaining)
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return b->tries_remaining - a->tries_remaining;
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return 0;
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}
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int ab_select_slot(struct blk_desc *dev_desc, struct disk_partition *part_info)
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{
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struct bootloader_control *abc = NULL;
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u32 crc32_le;
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int slot, i, ret;
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bool store_needed = false;
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char slot_suffix[4];
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ret = ab_control_create_from_disk(dev_desc, part_info, &abc);
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if (ret < 0) {
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/*
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* This condition represents an actual problem with the code or
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* the board setup, like an invalid partition information.
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* Signal a repair mode and do not try to boot from either slot.
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*/
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return ret;
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}
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crc32_le = ab_control_compute_crc(abc);
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if (abc->crc32_le != crc32_le) {
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log_err("ANDROID: Invalid CRC-32 (expected %.8x, found %.8x),",
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crc32_le, abc->crc32_le);
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log_err("re-initializing A/B metadata.\n");
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ret = ab_control_default(abc);
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if (ret < 0) {
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free(abc);
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return -ENODATA;
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}
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store_needed = true;
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}
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if (abc->magic != BOOT_CTRL_MAGIC) {
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log_err("ANDROID: Unknown A/B metadata: %.8x\n", abc->magic);
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free(abc);
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return -ENODATA;
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}
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if (abc->version > BOOT_CTRL_VERSION) {
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log_err("ANDROID: Unsupported A/B metadata version: %.8x\n",
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abc->version);
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free(abc);
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return -ENODATA;
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}
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/*
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* At this point a valid boot control metadata is stored in abc,
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* followed by other reserved data in the same block. We select a with
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* the higher priority slot that
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* - is not marked as corrupted and
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* - either has tries_remaining > 0 or successful_boot is true.
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* If the selected slot has a false successful_boot, we also decrement
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* the tries_remaining until it eventually becomes unbootable because
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* tries_remaining reaches 0. This mechanism produces a bootloader
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* induced rollback, typically right after a failed update.
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*/
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/* Safety check: limit the number of slots. */
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if (abc->nb_slot > ARRAY_SIZE(abc->slot_info)) {
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abc->nb_slot = ARRAY_SIZE(abc->slot_info);
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store_needed = true;
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}
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slot = -1;
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for (i = 0; i < abc->nb_slot; ++i) {
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if (abc->slot_info[i].verity_corrupted ||
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!abc->slot_info[i].tries_remaining) {
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log_debug("ANDROID: unbootable slot %d tries: %d, ",
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i, abc->slot_info[i].tries_remaining);
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log_debug("corrupt: %d\n",
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abc->slot_info[i].verity_corrupted);
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continue;
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}
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log_debug("ANDROID: bootable slot %d pri: %d, tries: %d, ",
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i, abc->slot_info[i].priority,
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abc->slot_info[i].tries_remaining);
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log_debug("corrupt: %d, successful: %d\n",
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abc->slot_info[i].verity_corrupted,
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abc->slot_info[i].successful_boot);
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if (slot < 0 ||
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ab_compare_slots(&abc->slot_info[i],
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&abc->slot_info[slot]) < 0) {
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slot = i;
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}
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}
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if (slot >= 0 && !abc->slot_info[slot].successful_boot) {
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log_err("ANDROID: Attempting slot %c, tries remaining %d\n",
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BOOT_SLOT_NAME(slot),
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abc->slot_info[slot].tries_remaining);
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abc->slot_info[slot].tries_remaining--;
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store_needed = true;
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}
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if (slot >= 0) {
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/*
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* Legacy user-space requires this field to be set in the BCB.
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* Newer releases load this slot suffix from the command line
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* or the device tree.
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*/
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memset(slot_suffix, 0, sizeof(slot_suffix));
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slot_suffix[0] = BOOT_SLOT_NAME(slot);
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if (memcmp(abc->slot_suffix, slot_suffix,
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sizeof(slot_suffix))) {
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memcpy(abc->slot_suffix, slot_suffix,
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sizeof(slot_suffix));
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store_needed = true;
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}
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}
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if (store_needed) {
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abc->crc32_le = ab_control_compute_crc(abc);
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ab_control_store(dev_desc, part_info, abc);
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}
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free(abc);
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if (slot < 0)
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return -EINVAL;
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return slot;
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}
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