# 引导加载程序镜像的格式

[English]

引导加载程序镜像与应用程序镜像具有相同的结构，参见 应用程序镜像结构。二者唯一的区别在于 描述引导加载程序的结构体 不同。

要查看关于引导加载程序镜像的更多内容，请运行以下命令：

    esptool.py --chip esp32p4 image_info build/bootloader/bootloader.bin --version 2

输出结果如下形式所示：

    File size: 26576 (bytes)

    ESP32 image header
    ==================
    Image version: 1
    Entry point: 0x40080658
    Segments: 4
    Flash size: 2MB
    Flash freq: 40m
    Flash mode: DIO

    ESP32 extended image header
    ===========================
    WP pin: 0xee
    Flash pins drive settings: clk_drv: 0x0, q_drv: 0x0, d_drv: 0x0, cs0_drv: 0x0, hd_drv: 0x0, wp_drv: 0x0
    Chip ID: 0
    Minimal chip revision: v0.0, (legacy min_rev = 0)
    Maximal chip revision: v3.99

    Segments information
    ====================
    Segment   Length   Load addr   File offs  Memory types
    -------  -------  ----------  ----------  ------------
        1  0x01bb0  0x3fff0030  0x00000018  BYTE_ACCESSIBLE, DRAM, DIRAM_DRAM
        2  0x03c90  0x40078000  0x00001bd0  CACHE_APP
        3  0x00004  0x40080400  0x00005868  IRAM
        4  0x00f2c  0x40080404  0x00005874  IRAM

    ESP32 image footer
    ==================
    Checksum: 0x65 (valid)
    Validation hash: 6f31a7f8512f26f6bce7c3b270f93bf6cf1ee4602c322998ca8ce27433527e92 (valid)

    Bootloader information
    ======================
    Bootloader version: 1
    ESP-IDF: v5.1-dev-4304-gcb51a3b-dirty
    Compile time: Mar 30 2023 19:14:17

## 引导加载程序描述

引导加载程序二进制文件的 `DRAM0` 段起始位置为 `esp_bootloader_desc_t` 结构体，其中包含描述引导加载程序的特定字段。此结构体位置具有固定偏移量，大小为 sizeof(`esp_image_header_t`) + sizeof(`esp_image_segment_header_t`)。

> - `magic_byte`：esp_bootloader_desc 结构体的魔术字节

> - `reserved`：保留供 IDF 未来使用

> - `version`：引导加载程序版本，参见 CONFIG_BOOTLOADER_PROJECT_VER

> - `idf_ver`：IDF 版本。[1]

> - `date` 和 `time`：编译日期和时间

> - `reserved2`：保留供 IDF 未来使用

[1]

最大长度为 32 个字符，包括空终止符。

如需从正在运行的引导加载程序中获取 `esp_bootloader_desc_t` 结构体，请使用 `esp_bootloader_get_description()`。

如需从正在运行的应用程序中获取 `esp_bootloader_desc_t` 结构体，请使用 `esp_ota_get_bootloader_description()`。

## API参考

### Header File

- components/esp_bootloader_format/include/esp_bootloader_desc.h

- This header file can be included with:

  >     #include "esp_bootloader_desc.h"

- This header file is a part of the API provided by the `esp_bootloader_format` component. To declare that your component depends on `esp_bootloader_format`, add the following to your CMakeLists.txt:

  >     REQUIRES esp_bootloader_format

  > or

  >     PRIV_REQUIRES esp_bootloader_format

### Functions

const esp_bootloader_desc_t *esp_bootloader_get_description(void)

  Return esp_bootloader_desc structure.

  Intended for use by the bootloader.

  返回:

    Pointer to esp_bootloader_desc structure.

### Structures

struct esp_bootloader_desc_t

  Bootloader description structure.

  Public Members

  uint8_t magic_byte

    Magic byte ESP_BOOTLOADER_DESC_MAGIC_BYTE

  uint8_t reserved[3]

    reserved for IDF

  uint32_t version

    Bootloader version

  char idf_ver[32]

    Version IDF

  char date_time[24]

    Compile date and time

  uint8_t reserved2[16]

    reserved for IDF

### Macros

ESP_BOOTLOADER_DESC_MAGIC_BYTE

  The magic byte for the esp_bootloader_desc structure that is in DRAM.

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