129 lines
3.8 KiB
Markdown
129 lines
3.8 KiB
Markdown
# MCUBoot Implementation Guide
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Documentation of the steps taken to implement MCUBoot on a Nucleo G431RB development board.
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## Environnment config
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Use the environment written in flake.nix by running `nix develop`
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## Set up Zephyr
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Zephyr is the RTOS that uses the MCUboot bootloader being set up.
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[Getting started with Zephyr](https://docs.zephyrproject.org/latest/develop/getting_started/index.html)
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```sh
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west init zephyrproject
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cd zepyhrproject
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west update
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west zephyr-export
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cd zepyhr
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west sdk install
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```
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## MCUBoot POC Implementation
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MCUBoot is a bootloader for Zephyr, which allows multiple firmwares to exist on a board. MCUBoot can dynamically switch which firmware is active. This is useful in the event of one firmware failing.
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[Abstract MCUBoot Guide](https://docs.mcuboot.com/readme-zephyr.html)
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```sh
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west build -p always -b nucleo_g431rb samples/basic/blinky
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west flash --runner pyocd # had to su root first to run this (after running nix develop)
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```
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## Configure partition sizes
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The devicetree specification file declares the hardware configuration. The flash storage needs three partitions, one for boot, and two for the two firmwares it will hold.
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[DeviceTree Specification documentation](https://docs.zephyrproject.org/latest/build/dts/intro-scope-purpose.html)
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[Partitioning examples](https://docs.zephyrproject.org/latest/build/dts/api/bindings/mtd/fixed-partitions.html)
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The board I'm using has its DeviceTree Specification in `zephyr/boards/st/nucleo_g431rb/nucleo_g431rb.dts`
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I created a partition for MCUBoot, two firmware slots, and additional storage in the flash storage.
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```c
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&flash0 {
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partitions {
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#address-cells = <1>;
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#size-cells = <1>;
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ranges;
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boot_partition: partition@0 {
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compatible = "zephyr,mapped-partition";
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label = "mcuboot";
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reg = <0x00000000 0x00008000>;
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};
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slot0_partition: partition@8000 {
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compatible = "zephyr,mapped-partition";
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label = "image-0";
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reg = <0x00008000 0x00010000>;
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};
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slot1_partition: partition@10000 {
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compatible = "zephyr,mapped-partition";
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label = "image-1";
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reg = <0x00010000 0x0018000>;
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};
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storage_partition: partition@18000 {
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compatible = "zephyr,mapped-partition";
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label = "storage";
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reg = <0x00018000 0x00020000>;
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};
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};
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};
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```
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## Try to build MCUBoot
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```sh
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west build -p always -b nucleo_g431rb bootloader/mcuboot/boot/zephyr
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```
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old below
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```
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# Create a private key: https://docs.mcuboot.com/readme-zephyr.html
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python ./bootloader/mcuboot/scripts/imgtool.py keygen -k private.pem -t rsa-2048
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# Create its public key
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openssl rsa -in private.pem -pubout > public.pem
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# Set up signing: https://docs.mcuboot.com/readme-zephyr.html
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# ./bootloader/mcuboot/samples/zephyr/Makefile
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python bootloader/mcuboot/scripts/imgtool.py sign \
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--key mykey.pem \
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--header-size 0x200 \
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--align 8 \
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--version 1.2 \
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--slot-size 0x8000 \
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./
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# Add the key file path to the KConfig https://docs.zephyrproject.org/latest/build/kconfig/setting.html
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echo "
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# Set the key file
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CONFIG_BOOT_SIGNATURE_KEY_FILE=public.pem" >> "./zephyr/boards/st/nucleo_g431rb/nucleo_g431rb_defconfig"
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west build -p always -b nucleo_g431rb bootloader/mcuboot/boot/zephyr -d build/mcuboot -- -DEXTRA_CONF_FILE=mcuboot-nucleo-g431rb.conf
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west flash -d build/mcuboot --runner pyocd # (as root, with nix develop)
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cd zephyr
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# Package 1
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west build -p always -b nucleo_g431rb samples/basic/blinky -d build/app -- -DCONFIG_BOOTLOADER_MCUBOOT=y -DCONFIG_MCUBOOT_GENERATE_UNSIGNED_IMAGE=y
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west flash -d build/app --runner pyocd # (as root, with nix develop)
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# Package 2
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west build -p always -b nucleo_g431rb samples/basic/blinkyslow -d build/blinkyslow -- -DCONFIG_BOOTLOADER_MCUBOOT=y -DCONFIG_MCUBOOT_GENERATE_UNSIGNED_IMAGE=y
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pyocd flash --target stm32g431rbtx --base-address 0x08014800 build/blinkyslow/zephyr/zephyr.signed.hex
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``` |