1 /* 2 * Copyright (C) 2016 The Android Open Source Project 3 * 4 * Permission is hereby granted, free of charge, to any person 5 * obtaining a copy of this software and associated documentation 6 * files (the "Software"), to deal in the Software without 7 * restriction, including without limitation the rights to use, copy, 8 * modify, merge, publish, distribute, sublicense, and/or sell copies 9 * of the Software, and to permit persons to whom the Software is 10 * furnished to do so, subject to the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be 13 * included in all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 22 * SOFTWARE. 23 */ 24 25 #if !defined(AVB_INSIDE_LIBAVB_AB_H) && !defined(AVB_COMPILATION) 26 #error \ 27 "Never include this file directly, include libavb_ab/libavb_ab.h instead." 28 #endif 29 30 #ifndef AVB_AB_FLOW_H_ 31 #define AVB_AB_FLOW_H_ 32 33 #include "avb_ab_ops.h" 34 35 #ifdef __cplusplus 36 extern "C" { 37 #endif 38 39 /* Magic for the A/B struct when serialized. */ 40 #define AVB_AB_MAGIC "\0AB0" 41 #define AVB_AB_MAGIC_LEN 4 42 43 /* Versioning for the on-disk A/B metadata - keep in sync with avbtool. */ 44 #define AVB_AB_MAJOR_VERSION 1 45 #define AVB_AB_MINOR_VERSION 0 46 47 /* Size of AvbABData struct. */ 48 #define AVB_AB_DATA_SIZE 32 49 50 /* Maximum values for slot data */ 51 #define AVB_AB_MAX_PRIORITY 15 52 #define AVB_AB_MAX_TRIES_REMAINING 7 53 54 /* Struct used for recording per-slot metadata. 55 * 56 * When serialized, data is stored in network byte-order. 57 */ 58 typedef struct AvbABSlotData { 59 /* Slot priority. Valid values range from 0 to AVB_AB_MAX_PRIORITY, 60 * both inclusive with 1 being the lowest and AVB_AB_MAX_PRIORITY 61 * being the highest. The special value 0 is used to indicate the 62 * slot is unbootable. 63 */ 64 uint8_t priority; 65 66 /* Number of times left attempting to boot this slot ranging from 0 67 * to AVB_AB_MAX_TRIES_REMAINING. 68 */ 69 uint8_t tries_remaining; 70 71 /* Non-zero if this slot has booted successfully, 0 otherwise. */ 72 uint8_t successful_boot; 73 74 /* Reserved for future use. */ 75 uint8_t reserved[1]; 76 } AVB_ATTR_PACKED AvbABSlotData; 77 78 /* Struct used for recording A/B metadata. 79 * 80 * When serialized, data is stored in network byte-order. 81 */ 82 typedef struct AvbABData { 83 /* Magic number used for identification - see AVB_AB_MAGIC. */ 84 uint8_t magic[AVB_AB_MAGIC_LEN]; 85 86 /* Version of on-disk struct - see AVB_AB_{MAJOR,MINOR}_VERSION. */ 87 uint8_t version_major; 88 uint8_t version_minor; 89 90 /* Padding to ensure |slots| field start eight bytes in. */ 91 uint8_t reserved1[2]; 92 93 /* Per-slot metadata. */ 94 AvbABSlotData slots[2]; 95 96 /* Reserved for future use. */ 97 uint8_t reserved2[12]; 98 99 /* CRC32 of all 28 bytes preceding this field. */ 100 uint32_t crc32; 101 } AVB_ATTR_PACKED AvbABData; 102 103 /* Copies |src| to |dest|, byte-swapping fields in the 104 * process. Returns false if the data is invalid (e.g. wrong magic, 105 * wrong CRC32 etc.), true otherwise. 106 */ 107 bool avb_ab_data_verify_and_byteswap(const AvbABData* src, AvbABData* dest); 108 109 /* Copies |src| to |dest|, byte-swapping fields in the process. Also 110 * updates the |crc32| field in |dest|. 111 */ 112 void avb_ab_data_update_crc_and_byteswap(const AvbABData* src, AvbABData* dest); 113 114 /* Initializes |data| such that it has two slots and both slots have 115 * maximum tries remaining. The CRC is not set. 116 */ 117 void avb_ab_data_init(AvbABData* data); 118 119 /* Reads A/B metadata from the 'misc' partition using |ops|. Returned 120 * data is properly byteswapped. Returns AVB_IO_RESULT_OK on 121 * success, error code otherwise. 122 * 123 * If the data read from disk is invalid (e.g. wrong magic or CRC 124 * checksum failure), the metadata will be reset using 125 * avb_ab_data_init() and then written to disk. 126 */ 127 AvbIOResult avb_ab_data_read(AvbABOps* ab_ops, AvbABData* data); 128 129 /* Writes A/B metadata to the 'misc' partition using |ops|. This will 130 * byteswap and update the CRC as needed. Returns AVB_IO_RESULT_OK on 131 * success, error code otherwise. 132 */ 133 AvbIOResult avb_ab_data_write(AvbABOps* ab_ops, const AvbABData* data); 134 135 /* Return codes used in avb_ab_flow(), see that function for 136 * documentation of each value. 137 */ 138 typedef enum { 139 AVB_AB_FLOW_RESULT_OK, 140 AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR, 141 AVB_AB_FLOW_RESULT_ERROR_OOM, 142 AVB_AB_FLOW_RESULT_ERROR_IO, 143 AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS 144 } AvbABFlowResult; 145 146 /* Get a textual representation of |result|. */ 147 const char* avb_ab_flow_result_to_string(AvbABFlowResult result); 148 149 /* High-level function to select a slot to boot. The following 150 * algorithm is used: 151 * 152 * 1. A/B metadata is loaded and validated using the 153 * read_ab_metadata() operation. Typically this means it's read from 154 * the 'misc' partition and if it's invalid then it's reset using 155 * avb_ab_data_init() and this reset metadata is returned. 156 * 157 * 2. All bootable slots listed in the A/B metadata are verified using 158 * avb_slot_verify(). If a slot is invalid or if it fails verification 159 * (and |allow_verification_error| is false, see below), it will be 160 * marked as unbootable in the A/B metadata and the metadata will be 161 * saved to disk before returning. 162 * 163 * 3. If there are no bootable slots, the value 164 * AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS is returned. 165 * 166 * 4. For each bootable slot, the Stored Rollback Indexes are updated 167 * such that for each rollback index location, the Stored Rollback 168 * Index is the largest number smaller than or equal to the Rollback 169 * Index of each slot. 170 * 171 * 5. The bootable slot with the highest priority is selected and 172 * returned in |out_data|. If this slot is already marked as 173 * successful, the A/B metadata is not modified. However, if the slot 174 * is not marked as bootable its |tries_remaining| count is 175 * decremented and the A/B metadata is saved to disk before returning. 176 * In either case the value AVB_AB_FLOW_RESULT_OK is returning. 177 * 178 * The partitions to load is given in |requested_partitions| as a 179 * NULL-terminated array of NUL-terminated strings. Typically the 180 * |requested_partitions| array only contains a single item for the 181 * boot partition, 'boot'. 182 * 183 * If the device is unlocked (and _only_ if it's unlocked), true 184 * should be passed in the |allow_verification_error| parameter. This 185 * will allow considering slots as verified even when 186 * avb_slot_verify() returns 187 * AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED, 188 * AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION, or 189 * AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX for the slot in 190 * question. 191 * 192 * Note that androidboot.slot_suffix is not set in the |cmdline| field 193 * in |AvbSlotVerifyData| - you will have to pass this command-line 194 * option yourself. 195 * 196 * If a slot was selected and it verified then AVB_AB_FLOW_RESULT_OK 197 * is returned. 198 * 199 * If a slot was selected but it didn't verify then 200 * AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR is returned. This can 201 * only happen when |allow_verification_error| is true. 202 * 203 * If an I/O operation - such as loading/saving metadata or checking 204 * rollback indexes - fail, the value AVB_AB_FLOW_RESULT_ERROR_IO is 205 * returned. 206 * 207 * If memory allocation fails, AVB_AB_FLOW_RESULT_ERROR_OOM is 208 * returned. 209 * 210 * Reasonable behavior for handling AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS 211 * is to initiate device repair (which is device-dependent). 212 */ 213 AvbABFlowResult avb_ab_flow(AvbABOps* ab_ops, 214 const char* const* requested_partitions, 215 bool allow_verification_error, 216 AvbSlotVerifyData** out_data); 217 218 /* Marks the slot with the given slot number as active. Returns 219 * AVB_IO_RESULT_OK on success, error code otherwise. 220 * 221 * This function is typically used by the OS updater when completing 222 * an update. It can also used by the firmware for implementing the 223 * "set_active" command. 224 */ 225 AvbIOResult avb_ab_mark_slot_active(AvbABOps* ab_ops, unsigned int slot_number); 226 227 /* Marks the slot with the given slot number as unbootable. Returns 228 * AVB_IO_RESULT_OK on success, error code otherwise. 229 * 230 * This function is typically used by the OS updater before writing to 231 * a slot. 232 */ 233 AvbIOResult avb_ab_mark_slot_unbootable(AvbABOps* ab_ops, 234 unsigned int slot_number); 235 236 /* Marks the slot with the given slot number as having booted 237 * successfully. Returns AVB_IO_RESULT_OK on success, error code 238 * otherwise. 239 * 240 * Calling this on an unbootable slot is an error - AVB_IO_RESULT_OK 241 * will be returned yet the function will have no side-effects. 242 * 243 * This function is typically used by the OS updater after having 244 * confirmed that the slot works as intended. 245 */ 246 AvbIOResult avb_ab_mark_slot_successful(AvbABOps* ab_ops, 247 unsigned int slot_number); 248 249 #ifdef __cplusplus 250 } 251 #endif 252 253 #endif /* AVB_AB_FLOW_H_ */ 254