应用程序镜像格式

应用程序镜像结构

应用程序镜像包含以下内容：

esp_image_header_t 结构体描述了 SPI flash 的模式和内存段的数量。
esp_image_segment_header_t 结构体描述了每个段、每个段的长度及其在 ESP32-S3 内存中的位置，此描述后接长度为 data_len 的数据。镜像中每个段的数据偏移量的计算方式如下：
- 0 段的偏移量 = sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t)
- 1 段的偏移量 = 0 段的偏移量 + 0 段长度 + sizeof(esp_image_segment_header_t)
- 2 段的偏移量 = 1 段的偏移量 + 1 段长度 + sizeof(esp_image_segment_header_t)
- ...

segment_count 字段定义了每个段的数量，存储在 esp_image_header_t 中。各段段数量不能超过 ESP_IMAGE_MAX_SEGMENTS。

运行以下命令，获取镜像段列表：

esptool.py --chip esp32s3 image_info build/app.bin

esptool.py v2.3.1
Image version: 1
Entry point: 40080ea4
13 segments

Segment 1: len 0x13ce0 load 0x3f400020 file_offs 0x00000018 SOC_DROM
Segment 2: len 0x00000 load 0x3ff80000 file_offs 0x00013d00 SOC_RTC_DRAM
Segment 3: len 0x00000 load 0x3ff80000 file_offs 0x00013d08 SOC_RTC_DRAM
Segment 4: len 0x028e0 load 0x3ffb0000 file_offs 0x00013d10 DRAM
Segment 5: len 0x00000 load 0x3ffb28e0 file_offs 0x000165f8 DRAM
Segment 6: len 0x00400 load 0x40080000 file_offs 0x00016600 SOC_IRAM
Segment 7: len 0x09600 load 0x40080400 file_offs 0x00016a08 SOC_IRAM
Segment 8: len 0x62e4c load 0x400d0018 file_offs 0x00020010 SOC_IROM
Segment 9: len 0x06cec load 0x40089a00 file_offs 0x00082e64 SOC_IROM
Segment 10: len 0x00000 load 0x400c0000 file_offs 0x00089b58 SOC_RTC_IRAM
Segment 11: len 0x00004 load 0x50000000 file_offs 0x00089b60 SOC_RTC_DATA
Segment 12: len 0x00000 load 0x50000004 file_offs 0x00089b6c SOC_RTC_DATA
Segment 13: len 0x00000 load 0x50000004 file_offs 0x00089b74 SOC_RTC_DATA
Checksum: e8 (valid)
Validation Hash: 407089ca0eae2bbf83b4120979d3354b1c938a49cb7a0c997f240474ef2ec76b (valid)

应用程序启动时，ESP-IDF 日志中也会包含段的相关信息：

I (443) esp_image: segment 0: paddr=0x00020020 vaddr=0x3f400020 size=0x13ce0 ( 81120) map
I (489) esp_image: segment 1: paddr=0x00033d08 vaddr=0x3ff80000 size=0x00000 ( 0) load
I (530) esp_image: segment 2: paddr=0x00033d10 vaddr=0x3ff80000 size=0x00000 ( 0) load
I (571) esp_image: segment 3: paddr=0x00033d18 vaddr=0x3ffb0000 size=0x028e0 ( 10464) load
I (612) esp_image: segment 4: paddr=0x00036600 vaddr=0x3ffb28e0 size=0x00000 ( 0) load
I (654) esp_image: segment 5: paddr=0x00036608 vaddr=0x40080000 size=0x00400 ( 1024) load
I (695) esp_image: segment 6: paddr=0x00036a10 vaddr=0x40080400 size=0x09600 ( 38400) load
I (737) esp_image: segment 7: paddr=0x00040018 vaddr=0x400d0018 size=0x62e4c (405068) map
I (847) esp_image: segment 8: paddr=0x000a2e6c vaddr=0x40089a00 size=0x06cec ( 27884) load
I (888) esp_image: segment 9: paddr=0x000a9b60 vaddr=0x400c0000 size=0x00000 ( 0) load
I (929) esp_image: segment 10: paddr=0x000a9b68 vaddr=0x50000000 size=0x00004 ( 4) load
I (971) esp_image: segment 11: paddr=0x000a9b74 vaddr=0x50000004 size=0x00000 ( 0) load
I (1012) esp_image: segment 12: paddr=0x000a9b7c vaddr=0x50000004 size=0x00000 ( 0) load

有关内存段类型和地址范围的详细信息，请参阅 ESP32-S3 技术参考手册 > 系统和存储器 > 内部存储器 [PDF]。

镜像有一个校验和字节，位于最后一个段之后。此字节写在一个十六字节填充边界上，因此应用程序镜像可能需要填充。
如果在 esp_image_header_t 中设置了 hash_appended 字段，则会附加 SHA256 校验和字段。SHA256 哈希值的计算范围是从第一个字节开始，到这个字段为止。该字段长度为 32 字节。
如果选项 CONFIG_SECURE_SIGNED_APPS_SCHEME 设置为 ECDSA，那么应用程序镜像将有额外的 68 字节用于 ECDSA 签名，其中包括：
- 版本号（4 字节）
- 签名数据（64 字节）
如果选项 CONFIG_SECURE_SIGNED_APPS_SCHEME 设置为 RSA 或 ECDSA (V2)，则应用程序镜像将有一个额外的签名扇区，大小为 4K 字节。关于此签名扇区格式的更多内容，请参考 Signature Block Format。

应用程序描述

应用程序二进制文件的 DROM 段从 esp_app_desc_t 结构体开始，该结构体中包含了用于描述应用程序的特定字段，如下所示：

magic_word：esp_app_desc_t 结构体的魔术词
secure_version：参见防回滚
version：参见应用程序版本 1
project_name：通过 PROJECT_NAME 填充 1
time 和 date：编译时间和日期
idf_ver：ESP-IDF 的版本 1
app_elf_sha256：包含应用程序 ELF 文件的 sha256 哈希

1(1,2,3): 最大长度为 32 个字符，其中包括 null 终止符。也就是说，如果 PROJECT_NAME 的长度超过 31 个字符，超出的字符将被忽略。

这个结构体有助于识别通过空中升级 (OTA) 上传的镜像，因为其中包含一个固定的偏移量，大小为 sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t)。一旦设备接收到包含此结构体的第一个段，就能根据其中的充分信息来确定是否应继续更新。

要获取当前运行的应用程序的 esp_app_desc_t 结构体，请调用 esp_app_get_description()。

要获取另一个 OTA 分区的 esp_app_desc_t 结构体，请调用 esp_ota_get_partition_description()。

向应用程序添加自定义结构体

也可以自定义类似的结构体，并使其相对于镜像起始位置有一个固定的偏移量。

采用以下方式向镜像添加自定义结构体：

const __attribute__((section(".rodata_custom_desc"))) esp_custom_app_desc_t custom_app_desc = { ... }

自定义结构体的偏移量为 sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t) + sizeof(esp_app_desc_t)。

需在 CMakeLists.txt 中添加 target_link_libraries(${COMPONENT_TARGET} "-u custom_app_desc")，确保自定义结构体在未使用时也位于镜像中。

API 参考

Header File

components/bootloader_support/include/esp_app_format.h
This header file can be included with:
#include "esp_app_format.h"
This header file is a part of the API provided by the bootloader_support component. To declare that your component depends on bootloader_support, add the following to your CMakeLists.txt:
REQUIRES bootloader_support
or
PRIV_REQUIRES bootloader_support

Structures

struct esp_image_header_t

Main header of binary image.

Public Members

uint8_t magic: Magic word ESP_IMAGE_HEADER_MAGIC

uint8_t segment_count: Count of memory segments

uint8_t spi_mode: flash read mode (esp_image_spi_mode_t as uint8_t)

uint8_t spi_speed: flash frequency (esp_image_spi_freq_t as uint8_t)

uint8_t spi_size: flash chip size (esp_image_flash_size_t as uint8_t)

uint32_t entry_addr: Entry address

uint8_t wp_pin: WP pin when SPI pins set via efuse (read by ROM bootloader, the IDF bootloader uses software to configure the WP pin and sets this field to 0xEE=disabled)

uint8_t spi_pin_drv[3]: Drive settings for the SPI flash pins (read by ROM bootloader)

esp_chip_id_t chip_id: Chip identification number

uint8_t min_chip_rev: Minimal chip revision supported by image After the Major and Minor revision eFuses were introduced into the chips, this field is no longer used. But for compatibility reasons, we keep this field and the data in it. Use min_chip_rev_full instead. The software interprets this as a Major version for most of the chips and as a Minor version for the ESP32-C3.

uint16_t min_chip_rev_full: Minimal chip revision supported by image, in format: major * 100 + minor

uint16_t max_chip_rev_full: Maximal chip revision supported by image, in format: major * 100 + minor

uint8_t reserved[4]: Reserved bytes in additional header space, currently unused

uint8_t hash_appended: If 1, a SHA256 digest "simple hash" (of the entire image) is appended after the checksum. Included in image length. This digest is separate to secure boot and only used for detecting corruption. For secure boot signed images, the signature is appended after this (and the simple hash is included in the signed data).

struct esp_image_segment_header_t

Header of binary image segment.

Public Members

uint32_t load_addr: Address of segment

uint32_t data_len: Length of data

Macros

ESP_IMAGE_HEADER_MAGIC: The magic word for the esp_image_header_t structure.

ESP_IMAGE_MAX_SEGMENTS: Max count of segments in the image.

Enumerations

enum esp_chip_id_t

ESP chip ID.

Values:

enumerator ESP_CHIP_ID_ESP32: chip ID: ESP32

enumerator ESP_CHIP_ID_ESP32S2: chip ID: ESP32-S2

enumerator ESP_CHIP_ID_ESP32C3: chip ID: ESP32-C3

enumerator ESP_CHIP_ID_ESP32S3: chip ID: ESP32-S3

enumerator ESP_CHIP_ID_ESP32C2: chip ID: ESP32-C2

enumerator ESP_CHIP_ID_ESP32C6: chip ID: ESP32-C6

enumerator ESP_CHIP_ID_ESP32H2: chip ID: ESP32-H2

enumerator ESP_CHIP_ID_ESP32P4: chip ID: ESP32-P4

enumerator ESP_CHIP_ID_INVALID: Invalid chip ID (we defined it to make sure the esp_chip_id_t is 2 bytes size)

enum esp_image_spi_mode_t

SPI flash mode, used in esp_image_header_t.

Values:

enumerator ESP_IMAGE_SPI_MODE_QIO: SPI mode QIO

enumerator ESP_IMAGE_SPI_MODE_QOUT: SPI mode QOUT

enumerator ESP_IMAGE_SPI_MODE_DIO: SPI mode DIO

enumerator ESP_IMAGE_SPI_MODE_DOUT: SPI mode DOUT

enumerator ESP_IMAGE_SPI_MODE_FAST_READ: SPI mode FAST_READ

enumerator ESP_IMAGE_SPI_MODE_SLOW_READ: SPI mode SLOW_READ

enum esp_image_spi_freq_t

SPI flash clock division factor.

Values:

enumerator ESP_IMAGE_SPI_SPEED_DIV_2: The SPI flash clock frequency is divided by 2 of the clock source

enumerator ESP_IMAGE_SPI_SPEED_DIV_3: The SPI flash clock frequency is divided by 3 of the clock source

enumerator ESP_IMAGE_SPI_SPEED_DIV_4: The SPI flash clock frequency is divided by 4 of the clock source

enumerator ESP_IMAGE_SPI_SPEED_DIV_1: The SPI flash clock frequency equals to the clock source

enum esp_image_flash_size_t

Supported SPI flash sizes.

Values:

enumerator ESP_IMAGE_FLASH_SIZE_1MB: SPI flash size 1 MB

enumerator ESP_IMAGE_FLASH_SIZE_2MB: SPI flash size 2 MB

enumerator ESP_IMAGE_FLASH_SIZE_4MB: SPI flash size 4 MB

enumerator ESP_IMAGE_FLASH_SIZE_8MB: SPI flash size 8 MB

enumerator ESP_IMAGE_FLASH_SIZE_16MB: SPI flash size 16 MB

enumerator ESP_IMAGE_FLASH_SIZE_32MB: SPI flash size 32 MB

enumerator ESP_IMAGE_FLASH_SIZE_64MB: SPI flash size 64 MB

enumerator ESP_IMAGE_FLASH_SIZE_128MB: SPI flash size 128 MB

enumerator ESP_IMAGE_FLASH_SIZE_MAX: SPI flash size MAX

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