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10 KiB
10 KiB
layout of boot.img
Image Content Index
1. header part
item size in bytes position
+-----------------------------------------------------------+ --> 0
|<MAGIC HEADER> | 8 |
|--------------------------------+--------------------------| --> 8
|<kernel length> | 4 |
|--------------------------------+--------------------------| --> 12
|<kernel offset> | 4 |
|--------------------------------+--------------------------| --> 16 (0x10)
|<ramdisk length> | 4 |
|--------------------------------+--------------------------| --> 20
|<ramdisk offset> | 4 |
|--------------------------------+--------------------------| --> 24
|<second bootloader length> | 4 |
|--------------------------------+--------------------------| --> 28
|<second bootloader offset> | 4 |
|--------------------------------+--------------------------| --> 32 (0x20)
|<tags offset> | 4 |
|--------------------------------+--------------------------| --> 36
|<page size> | 4 |
|--------------------------------+--------------------------| --> 40
|<header version> | 4 (value in [0,1,2]) |
|--------------------------------+--------------------------| --> 44
|<os version & os patch level> | 4 |
|--------------------------------+--------------------------| --> 48 (0x30)
|<board name> | 16 |
|--------------------------------+--------------------------| --> 64 (0x40)
|<cmdline part 1> | 512 |
|--------------------------------+--------------------------| --> 576 (0x240)
|<hash digest> | 32 |
|--------------------------------+--------------------------| --> 608 (0x260)
|<cmdline part 2> | 1024 |
|--------------------------------+--------------------------| --> 1632 (0x660)
|<recovery dtbo length> [v1] | 4 |
|--------------------------------+--------------------------| --> 1636
|<recovery dtbo offset> [v1] | 8 |
|--------------------------------+--------------------------| --> 1644
|<header size> [v1] | 4 (v1: value=1648) |
| | (v2: value=1660) |
|--------------------------------+--------------------------| --> 1648 (0x670)
|<dtb length> [v2] | 4 |
|--------------------------------+--------------------------| --> 1652
|<dtb offset> [v2] | 8 |
|--------------------------------+--------------------------| --> 1660 (0x67c)
|<padding> | min(n * page_size |
| | - header_size) |
+--------------------------------+--------------------------+ --> pagesize
2. data part
+-----------------------------------------------------------+ --> pagesize
|<kernel> | kernel length |
|--------------------------------+--------------------------|
|<padding> | min(n * page_size - len) |
+-----------------------------------------------------------+
+-----------------------------------------------------------+
|<ramdisk> | ramdisk length |
|--------------------------------+--------------------------|
|<padding> | min(n * page_size - len) |
+-----------------------------------------------------------+
+-----------------------------------------------------------+
|<second bootloader> | second bootloader length |
|--------------------------------+--------------------------|
|<padding> | min(n * page_size - len) |
+-----------------------------------------------------------+
+-----------------------------------------------------------+
|<recovery dtbo> [v1] | recovery dtbo length |
|--------------------------------+--------------------------|
|<padding> [v1] | min(n * page_size - len) |
+-----------------------------------------------------------+
+-----------------------------------------------------------+
|<dtb> [v2] | dtb length |
|--------------------------------+--------------------------|
|<padding> [v2] | min(n * page_size - len) |
+-----------------------------------------------------------+ --> end of data part
3. signature part
3.1 Boot Image Signature (VBoot 1.0)
+--------------------------------+--------------------------+ --> end of data part
|<signature> | signature length |
|--------------------------------+--------------------------+
|<padding> | defined by boot_signer |
+--------------------------------+--------------------------+
3.2 AVB Footer (VBoot 2.0)
item size in bytes position
+------+--------------------------------+-------------------------+ --> end of data part (say locaton +0)
| | VBMeta Header | total 256 |
| | | |
| | - Header Magic "AVB0" | 4 |
| | - avb_version Major | 4 |
| | - avb_version Minor | 4 |
| | - authentication_blob_size | 8 |
| | - auxiliary blob size | 8 |
| | - algorithm type | 4 |
| | - hash_offset | 8 |
| | - hash_size | 8 |
| | - signature_offset | 8 |
| | - signature_size | 8 |
| | - pub_key_offset | 8 |
|VBMeta| - pub_key_size | 8 |
| Blob | - pub_key_metadata_offset | 8 |
| | - pub_key_metadata_size | 8 |
| | - descriptors_offset | 8 |
| | - descriptors_size | 8 |
| | - rollback_index | 8 |
| | - flags | 4 |
| | - RESERVED | 4 |
| | - release string | 47 |
| | - NULL | 1 |
| | - RESERVED | 80 |
| |--------------------------------+-------------------------+ --> + 256
| | Authentication Blob | |
| | - Hash of Header & Aux Blob | alg.hash_num_bytes | --> + 256 + hash_offset
| | - Signature of Hash | alg.signature_num_bytes | --> + 256 + signature_offset
| | - Padding | align by 64 |
| +--------------------------------+-------------------------+
| | Auxiliary Blob | |
| | - descriptors | | --> + 256 + authentication_blob_size + descriptors_offset
| | - pub key | | --> + 256 + authentication_blob_size + pub_key_offset
| | - pub key meta data | | --> + 256 + authentication_blob_size + pub_key_metadata_offset
| | - padding | align by 64 |
| +--------------------------------+-------------------------+
| | Padding | align by block_size |
+------+--------------------------------+-------------------------+ --> + (block_size * n)
+---------------------------------------+-------------------------+
| | |
| | |
| DONOT CARE CHUNK | |
| | |
| | |
+--------------------------------------- -------------------------+
+---------------------------------------+-------------------------+ --> partition_size - block_size
| Padding | block_size - 64 |
+---------------------------------------+-------------------------+ --> partition_size - 64
| AVB Footer | total 64 |
| | |
| - Footer Magic "AVBf" | 4 |
| - Footer Major Version | 4 |
| - Footer Minor Version | 4 |
| - Original image size | 8 |
| - VBMeta offset | 8 |
| - VBMeta size | 8 |
| - Padding | 28 |
+---------------------------------------+-------------------------+ --> partition_size