Versal ACAP在线升级之Boot Image格式
1、简介
Xilinx FPGA、SOC器件和自适应计算加速平台（ACAPs）通常由多个硬件和软件二进制文件组成，用于启动这些设备后按照预期设计进行工作。这些二进制文件可以包括FPGA比特流、固件镜像、bootloader引导程序、操作系统和用户选择的应用程序，它们可以以非安全和安全的方式进行加载。
Bootgen是一个Xilinx工具，用于整合二进制文件并且生成设备引导镜像文件。同时Bootgen在给Xilinx设备创建boot images时，定义了输入的多种特征、属性和参数。
Bootgen同时提供了GUI接口和命令行选项。集成到Vitis中的GUI用于生成基本的boot images，除此之外的多数Bootgen选项都是命令行驱动的。驱动Bootgen的是一个boot image format（BIF）配置文件，后缀.bif。
2、Boot Image结构
2.1 说明
创建一个boot image包含如下两步：
（1）创建一个BIF文件；
（2）运行Bootgen可执行文件来创建一个boot image。
Xilinx不同系列的boot image格式是不同的，这里我们只学习记录下Versal ACAP的boot image，下图是Versal ACAP boot image的组件，也被称为Programmable Device Image（PDI）。
2.2 PMC
Versal ACAP中的平台管理控制器主要用于boot和配置。我们重点关注的是两个PMC MicroBlaze处理器（ROM code unit（RCU） / platform processing unit（PPU））处理的boot image。
（1）RCU
ROM code unit包含了一个三重冗余MicroBlaze处理器和一个ROM，该ROM中包含了BootROM可执行文件。BootROM可执行文件不能被改变。RCU中的MicroBlaze用于验证和运行BootROM可执行文件。RCU还负责启动后的安全监控，以及物理防克隆功能（physical unclonable function，PUF）管理
（2）PPU
Platform processing unit也包含了一个三重冗余MicroBlaze处理器，以及一个专用的384KB大小的PPU RAM。这个MicroBlaze用于运行平台加载和管理器（platform loader and manager）。
在Versal ACAP中，自适应引擎（PL）由rCDO和rNPI文件组成。rCDO文件主要包含CFrame数据以及PL和NoC电源域初始化命令。rNPI文件包含与NPI块相关的配置数据。NPI区块包括NoC元素：NMU、NSU、NPS、NCRB；DDR、XPHY、XPIO、GTY、MMCM等。
2.3 Versal ACAP Boot Header
在boot image的顶部就是Boot Header：
PMC的BootROM会使用这里的Boot Header。基于Boot Header里面的属性信息，PMC BootROM可以验证平台加载和管理器（PLM），并将PLM加载进PPU的RAM中。
Boot Header的前16字节用于检测SelectMAP总线。PMC的BootROM和PLM会忽略这些数据，因此Bootgen在进行checksum/SHA/RSA/加密等操作时不会包含这些数据。前16字节有以下3种情况：
-
X8: [LSB] 00 00 00 DD 11 22 33 44 55 66 77 88 99 AA BB CC [MSB]
-
X16: [LSB] 00 00 DD 00 22 11 44 33 66 55 88 77 AA 99 CC BB [MSB]
-
X32: [LSB] DD 00 00 00 44 33 22 11 88 77 66 55 CC BB AA 99 [MSB]
以实际的PDI文件为例：
默认的SelectMAP位宽就是X32。
Boot Header具体格式如下：
| Offset (Hex) |
Size (Bytes) |
Description |
Details |
| 0x00 |
16 |
SelectMAP bus width |
Used to determine if the SelectMAP bus width is x8, x16, or x32 |
| 0x10 |
4 |
QSPI bus width |
QSPI bus width description. This is required to identify the QSPI flash in single/dual stacked or dual parallel mode. 0xAA995566 in the little endian format. |
| 0x14 |
4 |
Image identification |
Boot image identification string. Contains 4 bytes X, N, L, X in byte order, which is 0x584c4e58 in the little endian format. |
| 0x18 |
4 |
Encryption key source |
This field is used to identify the AES key source: 0x00000000 0x00000000 - Unencrypted 0xA5C3C5A3 - eFUSE red key 0xA5C3C5A5 - eFUSE black key 0x3A5C3C5A - BBRAM red key 0x3A5C3C59 - BBRAM black key 0xA35C7C53 - Boot Header black key |
| 0x1C |
4 |
PLM source offset |
PLM source start address in PDI |
| 0x20 |
4 |
PMC data load address |
PMC CDO address to load |
| 0x24 |
4 |
PMC data length |
PMC CDO length |
| 0x28 |
4 |
Total PMC data length |
PMC CDO length including authentication and encryption overhead |
| 0x2C |
4 |
PLM length |
PLM original image size |
| 0x30 |
4 |
Total PLM length |
PLM image size including the authentication and encryption overhead |
| 0x34 |
4 |
Boot header attributes |
Boot Header Attributes |
| 0x38 |
32 |
Black key |
256-bit key, only valid when encryption status is set to black key in boot header |
| 0x58 |
12 |
Black IV |
Initialization vector used when decrypting the black key |
| 0x64 |
12 |
Secure header IV |
Secure header initialization vector |
| 0x70 |
4 |
PUF shutter value |
Length of the time the PUF samples before it closes the shutter Note: This shutter value must match the shutter value that was used during PUF registration. |
| 0x74 |
12 |
Secure Header IV for PMC Data |
The IV used to decrypt secure header of PMC data. |
| 0x80 |
68 |
Reserved |
Populate with zeroes. |
| 0xC4 |
4 |
Meta Header Offset |
Offset to the start of meta header |
| 0xC8-0x124 |
96 |
Reserved |
|
| 0x128 |
2048 |
Register init |
Stores register write pairs for system register initialization |
| 0x928 |
1544 |
PUF helper data |
PUF helper data |
| 0xF30 |
4 |
Checksum |
Header checksum |
| 0xF34 |
76 |
SHA3 padding |
SHA3 standard padding |
2.4 Boot Header Attributes
| Field Name |
Bit Offset |
Width |
Default Value |
Description |
| Reserved |
[31:18] |
14 |
0x0 |
Reserved for future use, Must be 0 |
| PUF Mode |
[17:16] |
2 |
0x0 |
0x3 - PUF 4K mode. 0x0 - PUF 12K mode. |
| Boot Header Authentication |
[15:14] |
2 |
0x0 |
0x3 - Authentication of the boot image is done, excluding verification of PPK hash and SPK ID. All others - Authentication will be decided based on eFUSE RSA/ECDSA bits. |
| Reserved |
[13:12] |
2 |
0x0 |
Reserved for future use, Must be 0 |
| DPA counter measure |
[11:10] |
2 |
0x0 |
0x3 - Enabled All others disabled. (eFUSE over rides this) |
| Checksum selection |
[9:8] |
2 |
0x0 |
0x0, 0x1, 0x2 - Reserved 0x3 - SHA3 is used as hash function to do Checksum. |
| PUF HD |
[7:6] |
2 |
0x0 |
0x3 - PUF HD is part of boot header All other - PUF HD is in eFUSE. |
| Reserved |
[5:0] |
6 |
0x0 |
Reserved |
2.5 Versal ACAP Image Header Table
要找到Image Header Table，需要先在Boot Header中找到0xC4 Meta Header Offset：
从实际的PDI 0xc4地址开始的4字节的值为0x00 0x04 0x9B 0xB0，那么Meta Header offset为0x0004_9BB0
Image Header表内容如下：
| Offset |
Name |
Description |
| 0x0 |
Version |
0x00040000(v4.0) : 1. Added AAD support for IHT. 2. Hash is included into the 32k secure chunk. 0x00030000(v3.0): updated secure chunk size to 32 KB from 64 KB 0x00020000(v2.00): IHT, PHT sizes doubled |
| 0x4 |
Total Number of Images |
Total number of images in the PDI |
| 0x8 |
Image header offset |
Address to start of first image header |
| 0xC |
Total Number of Partitions |
Total number of partitions in the PDI |
| 0x10 |
Partition Header Offset |
Offset to the start of partitions headers |
| 0x14 |
Secondary boot device address |
Indicates the address where secondary image is present. This is only valid if secondary boot device is present in attributes |
| 0x1C |
Image Header Table Attributes |
Refer to Table 22: Versal ACAP Image Header Table Attributes |
| 0x20 |
PDI ID |
Used to identify a PDI |
| 0x24 |
Parent ID |
ID of initial boot PDI. For boot PDI, it will be same as PDI ID |
| 0x28 |
Identification string |
Full PDI if present with boot header –“FPDI” Partial/Sub-system PDI – “PPDI” |
| 0x2C |
Headers size |
0-7: Image header table size in words 8-15: Image header size in words 16-23: Partition header size in words 24-31: Reserved |
| 0x30 |
Total meta header length |
Including authentication and encryption overhead (excluding IHT and including AC) |
| 0x34 -0x3C |
IV for encryption of meta header |
IV for decrypting SH of header table |
| 0x40 |
Encryption status |
Encryption key source, only key source used for PLM is valid for meta header. 0x00000000 - Unencrypted 0xA5C3C5A3 - eFuse red key 0xA5C3C5A5 - eFUSE black key 0x3A5C3C5A - BBRAM red key 0x3A5C3C59 - BBRAM black key 0xA35C7C53 - Boot Header black key |
| 0x48 |
Meta Header AC Offset (Word) |
Word Offset to Meta Header Authentication Certificate |
| 0x4c |
Meta Header Black/IV |
IV that is used to encrypt the Black key used to encrypt the Meta Header. |
| 0x44 - 0x78 |
Reserved |
0x0 |
| 0x7C |
Checksum |
A sum of all the previous words in the image header table |
Image Header Table Attributes表如下：
| Bit Field |
Name |
Description |
| 31:14 |
Reserved |
0 |
| 14 |
PUF Helper Data Location |
Location of the PUF Helper Data efuse/BH |
| 12 |
dpacm enable |
DPA Counter Measure enable or not |
| 11:6 |
Secondary boot device |
Indicates the device on which rest of the data is present in. 0 - Same boot device (default) 1 - QSPI32 2 - QSPI24 3 - NAND 4 - SD0 5 - SD1 6 - SDLS 7 - MMC 8 - USB 9 - ETHERNET 10 - PCIe 11 - SATA 12 - OSPI 13 - SMAP 14 - SBI 15 - SD0RAW 16 - SD1RAW 17 - SDLSRAW 18 - MMCRAW 19 - MMC0 20 - MMC0RAW All others are reserved Note: These options are supported for various devices in Bootgen. For the exact list of secondary boot devices supported by any device, refer to its corresponding Systems Software Developers Guide (SSDG). |
| 5:0 |
Reserved |
从Image Header Table的地址0x1c查到Image Header Table Attributes的4字节内容为0x0000_0000：
2.6 Versal ACAP Image Header
要找到Image Header，需要先在Image Header Table中找到地址0x8 Image header offset的4字节内容：
4字节内容为0x0001_270c，即Image Header是从地址0x0001_270c开始：
Image Header内容如下：
| Offset |
Name |
Description |
| 0x0 |
First Partition Header |
Word offset to first partition header |
| 0x4 |
Number of Partitions |
Number of partitions present for this image |
| 0x8 |
Revoke ID |
Revoke ID for Meta Header |
| 0xC |
Image Attributes |
See Image Attributes table |
| 0x10-0x1C |
Image Name |
ASCII name of the image. Max of 16 characters. Fill with Zeros when padding is required. |
| 0x20 |
Image/Node ID |
Defines the resource node the image is initializing |
| 0x24 |
Unique ID |
Defines the affinity/compatibility identifier when required for a given device resource |
| 0x28 |
Parent Unique ID |
Defines the required parent resource UID for the configuration content of the image, if required |
| 0x2c |
Function ID |
Identifier used to capture the unique function of the image configuration data |
| 0x30 |
DDR Low Address for Image Copy |
The DDR lower 32-bit address where the image should be copied when memcpy is enabled in BIF |
| 0x34 |
DDR High Address for Image Copy |
The DDR higher 32-bit address where image should be copied when memcpy is enabled in BIF |
| 0x38 |
Reserved |
|
| 0x3C |
Checksum |
A sum of all the previous words. |
Image Header Attibutes内容如下：
| Bit Field |
Name |
Description |
| 31:9 |
Reserved |
0 |
| 8 |
Delay Hand off |
0 – Handoff the image now (default) 1 – Handoff the image later |
| 7 |
Delay load |
0 – Load the image now (default) 1 – Load the image later |
| 6 |
Copy to memory |
0 – No copy to memory (Default) 1 – Image to be copied to memory |
| 5:3 |
Image Owner |
0 - PLM (default) 1 - Non-PLM 2-7 – Reserved |
| 2:0 |
Reserved |
0 |
2.7 Versal ACAP Partition Header
要找到Partition Header，需要先在Image Header Table中找到地址0x10 Partition Header Offset的4字节内容：
4字节内容为0x0001_274c，即Partition Header是从地址0x0001_274c开始：