262 lines
9.4 KiB
C
262 lines
9.4 KiB
C
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/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Permission is hereby granted, free of charge, to any person
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* obtaining a copy of this software and associated documentation
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* files (the "Software"), to deal in the Software without
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* restriction, including without limitation the rights to use, copy,
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* modify, merge, publish, distribute, sublicense, and/or sell copies
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* of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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* BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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* ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#if !defined(AVB_INSIDE_LIBAVB_AB_H) && !defined(AVB_COMPILATION)
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#error \
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"Never include this file directly, include libavb_ab/libavb_ab.h instead."
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#endif
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#ifndef AVB_AB_FLOW_H_
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#define AVB_AB_FLOW_H_
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#include "avb_ab_ops.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* Magic for the A/B struct when serialized. */
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#define AVB_AB_MAGIC "\0AB0"
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#define AVB_AB_MAGIC_LEN 4
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/* Versioning for the on-disk A/B metadata - keep in sync with avbtool. */
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#define AVB_AB_MAJOR_VERSION 1
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#define AVB_AB_MINOR_VERSION 0
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/* Size of AvbABData struct. */
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#define AVB_AB_DATA_SIZE 32
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/* Maximum values for slot data */
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#define AVB_AB_MAX_PRIORITY 15
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#define AVB_AB_MAX_TRIES_REMAINING 7
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/* Struct used for recording per-slot metadata.
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*
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* When serialized, data is stored in network byte-order.
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*/
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typedef struct AvbABSlotData {
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/* Slot priority. Valid values range from 0 to AVB_AB_MAX_PRIORITY,
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* both inclusive with 1 being the lowest and AVB_AB_MAX_PRIORITY
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* being the highest. The special value 0 is used to indicate the
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* slot is unbootable.
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*/
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uint8_t priority;
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/* Number of times left attempting to boot this slot ranging from 0
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* to AVB_AB_MAX_TRIES_REMAINING.
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*/
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uint8_t tries_remaining;
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/* Non-zero if this slot has booted successfully, 0 otherwise. */
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uint8_t successful_boot;
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/* Reserved for future use. */
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uint8_t reserved[1];
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} AVB_ATTR_PACKED AvbABSlotData;
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/* Struct used for recording A/B metadata.
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*
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* When serialized, data is stored in network byte-order.
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*/
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typedef struct AvbABData {
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/* Magic number used for identification - see AVB_AB_MAGIC. */
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uint8_t magic[AVB_AB_MAGIC_LEN];
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/* Version of on-disk struct - see AVB_AB_{MAJOR,MINOR}_VERSION. */
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uint8_t version_major;
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uint8_t version_minor;
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/* Padding to ensure |slots| field start eight bytes in. */
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uint8_t reserved1[2];
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/* Per-slot metadata. */
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AvbABSlotData slots[2];
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/* Reserved for future use. */
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uint8_t reserved2[12];
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/* CRC32 of all 28 bytes preceding this field. */
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uint32_t crc32;
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} AVB_ATTR_PACKED AvbABData;
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/* Copies |src| to |dest|, byte-swapping fields in the
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* process. Returns false if the data is invalid (e.g. wrong magic,
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* wrong CRC32 etc.), true otherwise.
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*/
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bool avb_ab_data_verify_and_byteswap(const AvbABData* src, AvbABData* dest);
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/* Copies |src| to |dest|, byte-swapping fields in the process. Also
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* updates the |crc32| field in |dest|.
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*/
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void avb_ab_data_update_crc_and_byteswap(const AvbABData* src, AvbABData* dest);
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/* Initializes |data| such that it has two slots and both slots have
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* maximum tries remaining. The CRC is not set.
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*/
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void avb_ab_data_init(AvbABData* data);
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/* Reads A/B metadata from the 'misc' partition using |ops|. Returned
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* data is properly byteswapped. Returns AVB_IO_RESULT_OK on
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* success, error code otherwise.
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*
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* If the data read from disk is invalid (e.g. wrong magic or CRC
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* checksum failure), the metadata will be reset using
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* avb_ab_data_init() and then written to disk.
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*/
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AvbIOResult avb_ab_data_read(AvbABOps* ab_ops, AvbABData* data);
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/* Writes A/B metadata to the 'misc' partition using |ops|. This will
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* byteswap and update the CRC as needed. Returns AVB_IO_RESULT_OK on
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* success, error code otherwise.
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*/
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AvbIOResult avb_ab_data_write(AvbABOps* ab_ops, const AvbABData* data);
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/* Return codes used in avb_ab_flow(), see that function for
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* documentation of each value.
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*/
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typedef enum {
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AVB_AB_FLOW_RESULT_OK,
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AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR,
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AVB_AB_FLOW_RESULT_ERROR_OOM,
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AVB_AB_FLOW_RESULT_ERROR_IO,
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AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS,
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AVB_AB_FLOW_RESULT_ERROR_INVALID_ARGUMENT
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} AvbABFlowResult;
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/* Get a textual representation of |result|. */
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const char* avb_ab_flow_result_to_string(AvbABFlowResult result);
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/* High-level function to select a slot to boot. The following
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* algorithm is used:
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*
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* 1. A/B metadata is loaded and validated using the
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* read_ab_metadata() operation. Typically this means it's read from
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* the 'misc' partition and if it's invalid then it's reset using
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* avb_ab_data_init() and this reset metadata is returned.
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*
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* 2. All bootable slots listed in the A/B metadata are verified using
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* avb_slot_verify(). If a slot is invalid or if it fails verification
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* (and AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR is not set, see
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* below), it will be marked as unbootable in the A/B metadata and the
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* metadata will be saved to disk before returning.
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*
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* 3. If there are no bootable slots, the value
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* AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS is returned.
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*
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* 4. For each bootable slot, the Stored Rollback Indexes are updated
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* such that for each rollback index location, the Stored Rollback
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* Index is the largest number smaller than or equal to the Rollback
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* Index of each slot.
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*
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* 5. The bootable slot with the highest priority is selected and
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* returned in |out_data|. If this slot is already marked as
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* successful, the A/B metadata is not modified. However, if the slot
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* is not marked as bootable its |tries_remaining| count is
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* decremented and the A/B metadata is saved to disk before returning.
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* In either case the value AVB_AB_FLOW_RESULT_OK is returning.
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*
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* The partitions to load is given in |requested_partitions| as a
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* NULL-terminated array of NUL-terminated strings. Typically the
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* |requested_partitions| array only contains a single item for the
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* boot partition, 'boot'.
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*
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* If the device is unlocked (and _only_ if it's unlocked), the
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* AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR flag should be set
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* in the |flags| parameter. This will allow considering slots as
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* verified even when avb_slot_verify() returns
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* AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED,
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* AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION, or
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* AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX for the slot in
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* question.
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*
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* Note that neither androidboot.slot_suffix nor androidboot.slot are
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* set in the |cmdline| field in |AvbSlotVerifyData| - you will have
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* to pass these yourself.
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*
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* If a slot was selected and it verified then AVB_AB_FLOW_RESULT_OK
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* is returned.
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*
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* If a slot was selected but it didn't verify then
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* AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR is returned. This can
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* only happen when the AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR
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* flag is set.
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*
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* If an I/O operation - such as loading/saving metadata or checking
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* rollback indexes - fail, the value AVB_AB_FLOW_RESULT_ERROR_IO is
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* returned.
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*
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* If memory allocation fails, AVB_AB_FLOW_RESULT_ERROR_OOM is
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* returned.
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*
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* If invalid arguments are passed,
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* AVB_AB_FLOW_RESULT_ERROR_INVALID_ARGUMENT is returned. For example
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* this can happen if using AVB_HASHTREE_ERROR_MODE_LOGGING without
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* AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR.
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*
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* Reasonable behavior for handling AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS
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* is to initiate device repair (which is device-dependent).
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*/
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AvbABFlowResult avb_ab_flow(AvbABOps* ab_ops,
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const char* const* requested_partitions,
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AvbSlotVerifyFlags flags,
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AvbHashtreeErrorMode hashtree_error_mode,
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AvbSlotVerifyData** out_data);
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/* Marks the slot with the given slot number as active. Returns
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* AVB_IO_RESULT_OK on success, error code otherwise.
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*
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* This function is typically used by the OS updater when completing
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* an update. It can also used by the firmware for implementing the
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* "set_active" command.
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*/
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AvbIOResult avb_ab_mark_slot_active(AvbABOps* ab_ops, unsigned int slot_number);
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/* Marks the slot with the given slot number as unbootable. Returns
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* AVB_IO_RESULT_OK on success, error code otherwise.
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*
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* This function is typically used by the OS updater before writing to
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* a slot.
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*/
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AvbIOResult avb_ab_mark_slot_unbootable(AvbABOps* ab_ops,
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unsigned int slot_number);
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/* Marks the slot with the given slot number as having booted
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* successfully. Returns AVB_IO_RESULT_OK on success, error code
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* otherwise.
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*
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* Calling this on an unbootable slot is an error - AVB_IO_RESULT_OK
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* will be returned yet the function will have no side-effects.
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*
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* This function is typically used by the OS updater after having
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* confirmed that the slot works as intended.
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*/
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AvbIOResult avb_ab_mark_slot_successful(AvbABOps* ab_ops,
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unsigned int slot_number);
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#ifdef __cplusplus
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}
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#endif
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#endif /* AVB_AB_FLOW_H_ */
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