`stm32f411`

The stm32f411 example uses a STM32F411EDISCOVERY BOARD.The board has four LEDs of which two LEDs are used in this example.

Note:

If you're using a different version of the board, you'll probably need to edit your firmware's partition-addresses to accommodate for differences.

Just make sure you don't change the names of files or the folder structure, as cargo xtask looks for these file/folder names.

Partitioning:

The first step in integrating rustBoot is flash-memory partitioning i.e. we divide the stm32f411's flash-memory into 4 partitions, taking into account the geometry of the flash memory.

You can read more about mcu partitioning here

In this example, we'll be using the following partitioning scheme. You can locate these constants in the constants module

#![allow(unused)]
fn main() {
#[cfg(feature = "stm32f411")]
pub const SECTOR_SIZE: usize = 0x20000;
#[cfg(feature = "stm32f411")]
pub const PARTITION_SIZE: usize = 0x20000;
#[cfg(feature = "stm32f411")]
pub const BOOT_PARTITION_ADDRESS: usize = 0x08020000;
#[cfg(feature = "stm32f411")]
pub const SWAP_PARTITION_ADDRESS: usize = 0x08060000;
#[cfg(feature = "stm32f411")]
pub const UPDATE_PARTITION_ADDRESS: usize = 0x08040000;
}

RUSTBOOT partition: contains the bootloader (its code and data) and a (test) public-key embedded as part of the bootloader image, starts at address 0x0800_0000.
BOOT partition: contains boot firmware, starts at address PARTITION_BOOT_ADDRESS.
UPDATE partition: contains update firmware, starts at address UPDATE_PARTITION_ADDRESS. The boot firmware is responsible for downloading and installing the update firmware into this partition via a secure channel.
SWAP partition: is the temporary swap space, starts at address SWAP_PARTITION_ADDRESS.

Compiling, Signing and Programming:

Now that we have properly partitioned the stm32f411's on-board flash-memory, the next step is - compiling, signing and programming

We will compile the following

bootloader
boot and update firmware

sign both pieces of firmware with a (test) private-key and finally create valid rustBoot mcu-images i.e. signed boot and update firmware images.

Note:

the ecc256.der file contains a public-key and a private-key, the first 64 bytes being the public-key and remaining 32 bytes make up the private-key.

This is a test key file and is to be used for testing purposes only.

Compiling, signing and programming can be performed via a single command

cargo stm32f411 build-sign-flash rustBoot [boot-ver] [updt-ver]

Note:

The updt-ver number should be greater than boot-ver.

This will build, sign and flash all 3 packages (i.e. bootloader + boot-fw + update-fw) onto the board.

Note:

The corresponding public-key is embedded in the bootloader's source.

In order to test this example, you'll have to install a couple of pre-requisites as it uses probe-run to flash the binary.

 cargo install probe-rs-cli 
 cargo install cargo-flash 
 cargo install cargo-binutils

Here's the command line output that should be produced.

yashwanthsingh@Yashwanths-MacBook-Pro rustBoot % cargo stm32f411 build-sign-flash rustBoot 1234 1235
    Finished dev [unoptimized + debuginfo] target(s) in 0.07s
     Running `target/debug/xtask stm32f411 build-sign-flash rustBoot 1234 1235`
$ cargo build --release
warning: unused config key `build.runner` in `/Users/yashwanthsingh/Yash/Projects/git_rustBoot_mcusigner/rustBoot/boards/firmware/stm32f411/boot_fw_blinky_green/.cargo/config.toml`
    Finished release [optimized] target(s) in 0.10s
$ cargo build --release
warning: unused config key `build.runner` in `/Users/yashwanthsingh/Yash/Projects/git_rustBoot_mcusigner/rustBoot/boards/firmware/stm32f411/updt_fw_blinky_red/.cargo/config.toml`
    Finished release [optimized] target(s) in 0.10s
$ cargo build --release
    Finished release [optimized] target(s) in 0.11s
$ rust-objcopy -I elf32-littlearm ../../target/thumbv7em-none-eabihf/release/stm32f411_bootfw -O binary stm32f411_bootfw.bin
$ rust-objcopy -I elf32-littlearm ../../target/thumbv7em-none-eabihf/release/stm32f411_updtfw -O binary stm32f411_updtfw.bin
$ cargo run mcu-image ../boards/sign_images/signed_images/stm32f411_bootfw.bin nistp256 ../boards/sign_images/keygen/ecc256.der 1234
    Finished dev [unoptimized + debuginfo] target(s) in 0.06s
     Running `/Users/yashwanthsingh/Yash/Projects/git_rustBoot_mcusigner/rustBoot/target/debug/rbsigner mcu-image ../boards/sign_images/signed_images/stm32f411_bootfw.bin nistp256 ../boards/sign_images/keygen/ecc256.der 1234`

Update type:    Firmware
Curve type:       nistp256
Input image:      stm32f411_bootfw.bin
Public key:       ecc256.der
Image version:    1234
Output image:     stm32f411_bootfw_v1234_signed.bin
Calculating sha256 digest...
Signing the firmware...
Done.
Output image successfully created with 1908 bytes.

$ cargo run mcu-image ../boards/sign_images/signed_images/stm32f411_updtfw.bin nistp256 ../boards/sign_images/keygen/ecc256.der 1235
    Finished dev [unoptimized + debuginfo] target(s) in 0.10s
     Running `/Users/yashwanthsingh/Yash/Projects/git_rustBoot_mcusigner/rustBoot/target/debug/rbsigner mcu-image ../boards/sign_images/signed_images/stm32f411_updtfw.bin nistp256 ../boards/sign_images/keygen/ecc256.der 1235`

Update type:    Firmware
Curve type:       nistp256
Input image:      stm32f411_updtfw.bin
Public key:       ecc256.der
Image version:    1235
Output image:     stm32f411_updtfw_v1235_signed.bin
Calculating sha256 digest...
Signing the firmware...
Done.
Output image successfully created with 1996 bytes.

$ probe-rs-cli erase --chip stm32f411vetx
$ probe-rs-cli download --format Bin --base-address 0x8020000 --chip stm32f411vetx stm32f411_bootfw_v1234_signed.bin
     Erasing sectors ✔ [00:00:01] [############################] 128.00KiB/128.00KiB @ 65.02KiB/s (eta 0s )
 Programming pages   ✔ [00:00:00] [##############################]  2.00KiB/ 2.00KiB @     677B/s (eta 0s )
    Finished in 2.057s
$ probe-rs-cli download --format Bin --base-address 0x8040000 --chip stm32f411vetx stm32f411_updtfw_v1235_signed.bin
     Erasing sectors ✔ [00:00:01] [############################] 128.00KiB/128.00KiB @ 65.15KiB/s (eta 0s )
 Programming pages   ✔ [00:00:00] [##############################]  2.00KiB/ 2.00KiB @     679B/s (eta 0s )
    Finished in 2.052s
$ cargo flash --chip stm32f411vetx --release
    Finished release [optimized] target(s) in 0.08s
    Flashing /Users/yashwanthsingh/Yash/Projects/git_rustBoot_mcusigner/rustBoot/boards/target/thumbv7em-none-eabihf/release/stm32f411
     Erasing sectors ✔ [00:00:01] [##############################] 48.00KiB/48.00KiB @ 40.79KiB/s (eta 0s )
 Programming pages   ✔ [00:00:01] [##############################] 43.00KiB/43.00KiB @ 17.31KiB/s (eta 0s )
    Finished in 2.267s
yashwanthsingh@Yashwanths-MacBook-Pro rustBoot %

Verifying:

blinky leds are used to confirm that rustBoot works as expected. Here's the flow

Upon supplying power to the board, rustBoot takes over
- validates the firmware image stored in the BOOT partition
- verifies the signature attached against a known public key stored in the rustBoot image.
If the signature checks out, rustBoot boots into the bootfw and blinks a green-led for a few seconds,
- post which, the boot firmware triggers the update and performs a system reset.
Upon reset, the rustBoot again takes over
- validates the firmware image stored in the UPDATE partition
- swaps the contents of the BOOT and the UPDATE partitions
- marks the new firmware in the BOOT partition as in state STATE_TESTING
- boots into the UPDATE'd firmware
Now that execution-control has been transferred to the UPDATE'd firmware
- it will attempt to blink a red-led
- and set a confirmation flag to indicate that the update was successful.
- post which, it continuously blinks a red-led.

rustBoot Documentation

stm32f411

Partitioning:

Compiling, Signing and Programming:

Verifying:

`stm32f411`