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diff --git a/libavb_ab/avb_ab_flow.h b/libavb_ab/avb_ab_flow.h new file mode 100644 index 0000000..b2584d8 --- a/dev/null +++ b/libavb_ab/avb_ab_flow.h @@ -0,0 +1,253 @@ +/* + * Copyright (C) 2016 The Android Open Source Project + * + * Permission is hereby granted, free of charge, to any person + * obtaining a copy of this software and associated documentation + * files (the "Software"), to deal in the Software without + * restriction, including without limitation the rights to use, copy, + * modify, merge, publish, distribute, sublicense, and/or sell copies + * of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be + * included in all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, + * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF + * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND + * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS + * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN + * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN + * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ + +#if !defined(AVB_INSIDE_LIBAVB_AB_H) && !defined(AVB_COMPILATION) +#error \ + "Never include this file directly, include libavb_ab/libavb_ab.h instead." +#endif + +#ifndef AVB_AB_FLOW_H_ +#define AVB_AB_FLOW_H_ + +#include "avb_ab_ops.h" + +#ifdef __cplusplus +extern "C" { +#endif + +/* Magic for the A/B struct when serialized. */ +#define AVB_AB_MAGIC "\0AB0" +#define AVB_AB_MAGIC_LEN 4 + +/* Versioning for the on-disk A/B metadata - keep in sync with avbtool. */ +#define AVB_AB_MAJOR_VERSION 1 +#define AVB_AB_MINOR_VERSION 0 + +/* Size of AvbABData struct. */ +#define AVB_AB_DATA_SIZE 32 + +/* Maximum values for slot data */ +#define AVB_AB_MAX_PRIORITY 15 +#define AVB_AB_MAX_TRIES_REMAINING 7 + +/* Struct used for recording per-slot metadata. + * + * When serialized, data is stored in network byte-order. + */ +typedef struct AvbABSlotData { + /* Slot priority. Valid values range from 0 to AVB_AB_MAX_PRIORITY, + * both inclusive with 1 being the lowest and AVB_AB_MAX_PRIORITY + * being the highest. The special value 0 is used to indicate the + * slot is unbootable. + */ + uint8_t priority; + + /* Number of times left attempting to boot this slot ranging from 0 + * to AVB_AB_MAX_TRIES_REMAINING. + */ + uint8_t tries_remaining; + + /* Non-zero if this slot has booted successfully, 0 otherwise. */ + uint8_t successful_boot; + + /* Reserved for future use. */ + uint8_t reserved[1]; +} AVB_ATTR_PACKED AvbABSlotData; + +/* Struct used for recording A/B metadata. + * + * When serialized, data is stored in network byte-order. + */ +typedef struct AvbABData { + /* Magic number used for identification - see AVB_AB_MAGIC. */ + uint8_t magic[AVB_AB_MAGIC_LEN]; + + /* Version of on-disk struct - see AVB_AB_{MAJOR,MINOR}_VERSION. */ + uint8_t version_major; + uint8_t version_minor; + + /* Padding to ensure |slots| field start eight bytes in. */ + uint8_t reserved1[2]; + + /* Per-slot metadata. */ + AvbABSlotData slots[2]; + + /* Reserved for future use. */ + uint8_t reserved2[12]; + + /* CRC32 of all 28 bytes preceding this field. */ + uint32_t crc32; +} AVB_ATTR_PACKED AvbABData; + +/* Copies |src| to |dest|, byte-swapping fields in the + * process. Returns false if the data is invalid (e.g. wrong magic, + * wrong CRC32 etc.), true otherwise. + */ +bool avb_ab_data_verify_and_byteswap(const AvbABData* src, AvbABData* dest); + +/* Copies |src| to |dest|, byte-swapping fields in the process. Also + * updates the |crc32| field in |dest|. + */ +void avb_ab_data_update_crc_and_byteswap(const AvbABData* src, AvbABData* dest); + +/* Initializes |data| such that it has two slots and both slots have + * maximum tries remaining. The CRC is not set. + */ +void avb_ab_data_init(AvbABData* data); + +/* Reads A/B metadata from the 'misc' partition using |ops|. Returned + * data is properly byteswapped. Returns AVB_IO_RESULT_OK on + * success, error code otherwise. + * + * If the data read from disk is invalid (e.g. wrong magic or CRC + * checksum failure), the metadata will be reset using + * avb_ab_data_init() and then written to disk. + */ +AvbIOResult avb_ab_data_read(AvbABOps* ab_ops, AvbABData* data); + +/* Writes A/B metadata to the 'misc' partition using |ops|. This will + * byteswap and update the CRC as needed. Returns AVB_IO_RESULT_OK on + * success, error code otherwise. + */ +AvbIOResult avb_ab_data_write(AvbABOps* ab_ops, const AvbABData* data); + +/* Return codes used in avb_ab_flow(), see that function for + * documentation of each value. + */ +typedef enum { + AVB_AB_FLOW_RESULT_OK, + AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR, + AVB_AB_FLOW_RESULT_ERROR_OOM, + AVB_AB_FLOW_RESULT_ERROR_IO, + AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS +} AvbABFlowResult; + +/* Get a textual representation of |result|. */ +const char* avb_ab_flow_result_to_string(AvbABFlowResult result); + +/* High-level function to select a slot to boot. The following + * algorithm is used: + * + * 1. A/B metadata is loaded and validated using the + * read_ab_metadata() operation. Typically this means it's read from + * the 'misc' partition and if it's invalid then it's reset using + * avb_ab_data_init() and this reset metadata is returned. + * + * 2. All bootable slots listed in the A/B metadata are verified using + * avb_slot_verify(). If a slot is invalid or if it fails verification + * (and |allow_verification_error| is false, see below), it will be + * marked as unbootable in the A/B metadata and the metadata will be + * saved to disk before returning. + * + * 3. If there are no bootable slots, the value + * AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS is returned. + * + * 4. For each bootable slot, the Stored Rollback Indexes are updated + * such that for each rollback index location, the Stored Rollback + * Index is the largest number smaller than or equal to the Rollback + * Index of each slot. + * + * 5. The bootable slot with the highest priority is selected and + * returned in |out_data|. If this slot is already marked as + * successful, the A/B metadata is not modified. However, if the slot + * is not marked as bootable its |tries_remaining| count is + * decremented and the A/B metadata is saved to disk before returning. + * In either case the value AVB_AB_FLOW_RESULT_OK is returning. + * + * The partitions to load is given in |requested_partitions| as a + * NULL-terminated array of NUL-terminated strings. Typically the + * |requested_partitions| array only contains a single item for the + * boot partition, 'boot'. + * + * If the device is unlocked (and _only_ if it's unlocked), true + * should be passed in the |allow_verification_error| parameter. This + * will allow considering slots as verified even when + * avb_slot_verify() returns + * AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED, + * AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION, or + * AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX for the slot in + * question. + * + * Note that androidboot.slot_suffix is not set in the |cmdline| field + * in |AvbSlotVerifyData| - you will have to pass this command-line + * option yourself. + * + * If a slot was selected and it verified then AVB_AB_FLOW_RESULT_OK + * is returned. + * + * If a slot was selected but it didn't verify then + * AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR is returned. This can + * only happen when |allow_verification_error| is true. + * + * If an I/O operation - such as loading/saving metadata or checking + * rollback indexes - fail, the value AVB_AB_FLOW_RESULT_ERROR_IO is + * returned. + * + * If memory allocation fails, AVB_AB_FLOW_RESULT_ERROR_OOM is + * returned. + * + * Reasonable behavior for handling AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS + * is to initiate device repair (which is device-dependent). + */ +AvbABFlowResult avb_ab_flow(AvbABOps* ab_ops, + const char* const* requested_partitions, + bool allow_verification_error, + AvbSlotVerifyData** out_data); + +/* Marks the slot with the given slot number as active. Returns + * AVB_IO_RESULT_OK on success, error code otherwise. + * + * This function is typically used by the OS updater when completing + * an update. It can also used by the firmware for implementing the + * "set_active" command. + */ +AvbIOResult avb_ab_mark_slot_active(AvbABOps* ab_ops, unsigned int slot_number); + +/* Marks the slot with the given slot number as unbootable. Returns + * AVB_IO_RESULT_OK on success, error code otherwise. + * + * This function is typically used by the OS updater before writing to + * a slot. + */ +AvbIOResult avb_ab_mark_slot_unbootable(AvbABOps* ab_ops, + unsigned int slot_number); + +/* Marks the slot with the given slot number as having booted + * successfully. Returns AVB_IO_RESULT_OK on success, error code + * otherwise. + * + * Calling this on an unbootable slot is an error - AVB_IO_RESULT_OK + * will be returned yet the function will have no side-effects. + * + * This function is typically used by the OS updater after having + * confirmed that the slot works as intended. + */ +AvbIOResult avb_ab_mark_slot_successful(AvbABOps* ab_ops, + unsigned int slot_number); + +#ifdef __cplusplus +} +#endif + +#endif /* AVB_AB_FLOW_H_ */ |