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 /* 26 #if !defined(AVB_INSIDE_LIBAVB_AB_H) && !defined(AVB_COMPILATION) 27 #error \ 28 "Never include this file directly, include libavb_ab/libavb_ab.h instead." 29 #endif 30 */ 31 32 #ifndef AVB_AB_FLOW_H_ 33 #define AVB_AB_FLOW_H_ 34 35 #include <android_avb/avb_ab_ops.h> 36 37 #ifdef __cplusplus 38 extern "C" { 39 #endif 40 41 /* Magic for the A/B struct when serialized. */ 42 #define AVB_AB_MAGIC "\0AB0" 43 #define AVB_AB_MAGIC_LEN 4 44 45 /* Versioning for the on-disk A/B metadata - keep in sync with avbtool. */ 46 #define AVB_AB_MAJOR_VERSION 1 47 #define AVB_AB_MINOR_VERSION 0 48 49 /* Size of AvbABData struct. */ 50 #define AVB_AB_DATA_SIZE 32 51 52 /* Maximum values for slot data */ 53 #define AVB_AB_MAX_PRIORITY 15 54 #define AVB_AB_MAX_TRIES_REMAINING 7 55 56 /* Struct used for recording per-slot metadata. 57 * 58 * When serialized, data is stored in network byte-order. 59 */ 60 typedef struct AvbABSlotData { 61 /* Slot priority. Valid values range from 0 to AVB_AB_MAX_PRIORITY, 62 * both inclusive with 1 being the lowest and AVB_AB_MAX_PRIORITY 63 * being the highest. The special value 0 is used to indicate the 64 * slot is unbootable. 65 */ 66 uint8_t priority; 67 68 /* Number of times left attempting to boot this slot ranging from 0 69 * to AVB_AB_MAX_TRIES_REMAINING. 70 */ 71 uint8_t tries_remaining; 72 73 /* Non-zero if this slot has booted successfully, 0 otherwise. */ 74 uint8_t successful_boot; 75 76 /* Reserved for future use. */ 77 uint8_t reserved[1]; 78 } AVB_ATTR_PACKED AvbABSlotData; 79 80 /* Struct used for recording A/B metadata. 81 * 82 * When serialized, data is stored in network byte-order. 83 */ 84 typedef struct AvbABData { 85 /* Magic number used for identification - see AVB_AB_MAGIC. */ 86 uint8_t magic[AVB_AB_MAGIC_LEN]; 87 88 /* Version of on-disk struct - see AVB_AB_{MAJOR,MINOR}_VERSION. */ 89 uint8_t version_major; 90 uint8_t version_minor; 91 92 /* Padding to ensure |slots| field start eight bytes in. */ 93 uint8_t reserved1[2]; 94 95 /* Per-slot metadata. */ 96 AvbABSlotData slots[2]; 97 98 /* Reserved for future use. */ 99 uint8_t last_boot; 100 uint8_t reserved2[11]; 101 102 /* CRC32 of all 28 bytes preceding this field. */ 103 uint32_t crc32; 104 } AVB_ATTR_PACKED AvbABData; 105 106 /* Copies |src| to |dest|, byte-swapping fields in the 107 * process. Returns false if the data is invalid (e.g. wrong magic, 108 * wrong CRC32 etc.), true otherwise. 109 */ 110 bool avb_ab_data_verify_and_byteswap(const AvbABData* src, AvbABData* dest); 111 112 /* Copies |src| to |dest|, byte-swapping fields in the process. Also 113 * updates the |crc32| field in |dest|. 114 */ 115 void avb_ab_data_update_crc_and_byteswap(const AvbABData* src, AvbABData* dest); 116 117 /* Initializes |data| such that it has two slots and both slots have 118 * maximum tries remaining. The CRC is not set. 119 */ 120 void avb_ab_data_init(AvbABData* data); 121 122 /* Reads A/B metadata from the 'misc' partition using |ops|. Returned 123 * data is properly byteswapped. Returns AVB_IO_RESULT_OK on 124 * success, error code otherwise. 125 * 126 * If the data read from disk is invalid (e.g. wrong magic or CRC 127 * checksum failure), the metadata will be reset using 128 * avb_ab_data_init() and then written to disk. 129 */ 130 AvbIOResult avb_ab_data_read(AvbABOps* ab_ops, AvbABData* data); 131 132 /* Writes A/B metadata to the 'misc' partition using |ops|. This will 133 * byteswap and update the CRC as needed. Returns AVB_IO_RESULT_OK on 134 * success, error code otherwise. 135 */ 136 AvbIOResult avb_ab_data_write(AvbABOps* ab_ops, const AvbABData* data); 137 138 /* Return codes used in avb_ab_flow(), see that function for 139 * documentation of each value. 140 */ 141 typedef enum { 142 AVB_AB_FLOW_RESULT_OK, 143 AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR, 144 AVB_AB_FLOW_RESULT_ERROR_OOM, 145 AVB_AB_FLOW_RESULT_ERROR_IO, 146 AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS, 147 AVB_AB_FLOW_RESULT_ERROR_INVALID_ARGUMENT 148 } AvbABFlowResult; 149 150 /* Get a textual representation of |result|. */ 151 const char* avb_ab_flow_result_to_string(AvbABFlowResult result); 152 153 /* High-level function to select a slot to boot. The following 154 * algorithm is used: 155 * 156 * 1. A/B metadata is loaded and validated using the 157 * read_ab_metadata() operation. Typically this means it's read from 158 * the 'misc' partition and if it's invalid then it's reset using 159 * avb_ab_data_init() and this reset metadata is returned. 160 * 161 * 2. All bootable slots listed in the A/B metadata are verified using 162 * avb_slot_verify(). If a slot is invalid or if it fails verification 163 * (and AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR is not set, see 164 * below), it will be marked as unbootable in the A/B metadata and the 165 * metadata will be saved to disk before returning. 166 * 167 * 3. If there are no bootable slots, the value 168 * AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS is returned. 169 * 170 * 4. For each bootable slot, the Stored Rollback Indexes are updated 171 * such that for each rollback index location, the Stored Rollback 172 * Index is the largest number smaller than or equal to the Rollback 173 * Index of each slot. 174 * 175 * 5. The bootable slot with the highest priority is selected and 176 * returned in |out_data|. If this slot is already marked as 177 * successful, the A/B metadata is not modified. However, if the slot 178 * is not marked as bootable its |tries_remaining| count is 179 * decremented and the A/B metadata is saved to disk before returning. 180 * In either case the value AVB_AB_FLOW_RESULT_OK is returning. 181 * 182 * The partitions to load is given in |requested_partitions| as a 183 * NULL-terminated array of NUL-terminated strings. Typically the 184 * |requested_partitions| array only contains a single item for the 185 * boot partition, 'boot'. 186 * 187 * If the device is unlocked (and _only_ if it's unlocked), the 188 * AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR flag should be set 189 * in the |flags| parameter. This will allow considering slots as 190 * verified even when avb_slot_verify() returns 191 * AVB_SLOT_VERIFY_RESULT_ERROR_PUBLIC_KEY_REJECTED, 192 * AVB_SLOT_VERIFY_RESULT_ERROR_VERIFICATION, or 193 * AVB_SLOT_VERIFY_RESULT_ERROR_ROLLBACK_INDEX for the slot in 194 * question. 195 * 196 * Note that neither androidboot.slot_suffix nor androidboot.slot are 197 * set in the |cmdline| field in |AvbSlotVerifyData| - you will have 198 * to pass these yourself. 199 * 200 * If a slot was selected and it verified then AVB_AB_FLOW_RESULT_OK 201 * is returned. 202 * 203 * If a slot was selected but it didn't verify then 204 * AVB_AB_FLOW_RESULT_OK_WITH_VERIFICATION_ERROR is returned. This can 205 * only happen when the AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR 206 * flag is set. 207 * 208 * If an I/O operation - such as loading/saving metadata or checking 209 * rollback indexes - fail, the value AVB_AB_FLOW_RESULT_ERROR_IO is 210 * returned. 211 * 212 * If memory allocation fails, AVB_AB_FLOW_RESULT_ERROR_OOM is 213 * returned. 214 * 215 * If invalid arguments are passed, 216 * AVB_AB_FLOW_RESULT_ERROR_INVALID_ARGUMENT is returned. For example 217 * this can happen if using AVB_HASHTREE_ERROR_MODE_LOGGING without 218 * AVB_SLOT_VERIFY_FLAGS_ALLOW_VERIFICATION_ERROR. 219 * 220 * Reasonable behavior for handling AVB_AB_FLOW_RESULT_ERROR_NO_BOOTABLE_SLOTS 221 * is to initiate device repair (which is device-dependent). 222 */ 223 AvbABFlowResult avb_ab_flow(AvbABOps* ab_ops, 224 const char* const* requested_partitions, 225 AvbSlotVerifyFlags flags, 226 AvbHashtreeErrorMode hashtree_error_mode, 227 AvbSlotVerifyData** out_data); 228 229 /* Marks the slot with the given slot number as active. Returns 230 * AVB_IO_RESULT_OK on success, error code otherwise. 231 * 232 * This function is typically used by the OS updater when completing 233 * an update. It can also used by the firmware for implementing the 234 * "set_active" command. 235 */ 236 AvbIOResult avb_ab_mark_slot_active(AvbABOps* ab_ops, unsigned int slot_number); 237 238 /* Marks the slot with the given slot number as unbootable. Returns 239 * AVB_IO_RESULT_OK on success, error code otherwise. 240 * 241 * This function is typically used by the OS updater before writing to 242 * a slot. 243 */ 244 AvbIOResult avb_ab_mark_slot_unbootable(AvbABOps* ab_ops, 245 unsigned int slot_number); 246 247 /* Marks the slot with the given slot number as having booted 248 * successfully. Returns AVB_IO_RESULT_OK on success, error code 249 * otherwise. 250 * 251 * Calling this on an unbootable slot is an error - AVB_IO_RESULT_OK 252 * will be returned yet the function will have no side-effects. 253 * 254 * This function is typically used by the OS updater after having 255 * confirmed that the slot works as intended. 256 */ 257 AvbIOResult avb_ab_mark_slot_successful(AvbABOps* ab_ops, 258 unsigned int slot_number); 259 260 /* 261 * Load metadata. 262 */ 263 AvbIOResult load_metadata(AvbABOps* ab_ops, 264 AvbABData* ab_data, 265 AvbABData* ab_data_orig); 266 267 /* Writes A/B metadata to disk only if it has changed - returns 268 * AVB_IO_RESULT_OK on success, error code otherwise. 269 */ 270 AvbIOResult save_metadata_if_changed(AvbABOps* ab_ops, 271 AvbABData* ab_data, 272 AvbABData* ab_data_orig); 273 274 #ifdef __cplusplus 275 } 276 #endif 277 278 #endif /* AVB_AB_FLOW_H_ */ 279