Customize esp32c6-bootloader for rust-based bare-metal firmware

[frabervo]

Hello,

I want to implement a secure update process for a Rust-based firmware. To do this, I want to play with the second-stage bootloader.

Is it possible to find out how the esp32c6's bootloader in the repository-ressources was built in order to reproduce it and perhaps adapt it to my needs?

Thanks for you responses.

[MabezDev]

The bootloader currently comes from esp-idf: https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-guides/bootloader.html. You'll need to clone and build the bootloader (see https://github.com/espressif/esp-idf/tree/master/components/bootloader). Once you've customized it, you can use your custom bootloader by using the --bootloader flag with espflash.

[frabervo]

I tried to custom the bootloader as mentioned above.

The actual status is the following: bootloader customized (default setting) with the esp-idf version 5.1 works fine on the esp32c6.

But the bootloader customized with the esp-idf version 5.4 doesn't work. The application remain the same as with the version esp-idf 5.1 . I receive the following error:

I (60) boot:  1 phy_ini�ESP-ROM:esp32c6-20220919
Build:Sep 19 2022
rst:0x1 (POWERON),boot:0xe (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x40875720,len:0x1694
load:0x4086c110,len:0xe84
load:0x4086e610,len:0x2f44
entry 0x4086c11a
I (23) boot: ESP-IDF v5.4-446-g5c75a994da 2nd stage bootloader
I (24) boot: compile time Feb 13 2025 12:44:52
I (24) boot: chip revision: v0.0
I (25) boot: efuse block revision: v0.2
I (28) boot.esp32c6: SPI Speed      : 80MHz
I (32) boot.esp32c6: SPI Mode       : DIO
I (36) boot.esp32c6: SPI Flash Size : 8MB
I (40) boot: Enabling RNG early entropy source...
I (44) boot: Partition Table:
I (47) boot: ## Label            Usage          Type ST Offset   Length
I (53) boot:  0 nvs              WiFi data        01 02 00009000 00006000
I (60) boot:  1 phy_init         RF data          01 01 0000f000 00001000
I (66) boot:  2 factory          factory app      00 00 00010000 007f0000
I (73) boot: End of partition table
E (76) esp_image: Failed to fetch app description header!
E (81) boot: Factory app partition is not bootable
E (85) boot: No bootable app partitions in the partition table

Is there an indication in the application binary which esp-idf version should be used?