| commit | 4bd723712734373cd63ae516f16713c3d872d28e | [log] [tgz] |
|---|---|---|
| author | Laura Abbott <laura@labbott.name> | Wed Feb 19 13:33:54 2020 -0500 |
| committer | Laura Abbott <laura@labbott.name> | Wed Feb 19 16:42:50 2020 -0500 |
| tree | a65d7b7d2d8d457b8ed0cbf93753684dd25dfb6c | |
| parent | 371334f5ccc8d2d31219fa317f05dc99bddabbc1 [diff] |
Use the absolute addresses for calculation in entry assembly Because RISC-V does not currently have full relocation support, the addresses in the crt0 header are the exact addreses, not offsets. This means we don't need to offset by the stack top again to get the app heap start. Adjust the assembly to account for this.
Rust userland library for Tock (WIP)
Tested with tock Release 1.4.1.
The library works in principle on most boards, but there is currently the showstopper bug #28 that prevents the generation of relocatable code. This means that all applications must be installed at the flash address they are compiled with, which usually means that they must be compiled especially for your board and that there can only be one application written in rust at a time and it must be installed as the first application on the board, unless you want to play games with linker scripts. There are some layout_*.ld files provided that allow to run the examples on common boards. Due to MPU region alignment issues they may not work for applications that use a lot of RAM, in that case you may have to change the SRAM start address to fit your application.
This project is nascent and still under heavy development, but first steps:
Ensure you have rustup installed.
Clone the repository:
git clone https://github.com/tock/libtock-rs cd libtock-rs
Install elf2tab:
cargo install -f elf2tab --version 0.4.0
Add dependencies for cross-compilation. Currently, only few platforms have been configured, e.g.:
rustup target add thumbv7em-none-eabi # For an nRF52 DK board
rustup target add riscv32imc-unknown-none-elf # For an OpenTitan board
Use cargo r<arch> to compile and run an example app. The full command is platform dependent and looks as follows for the blink example:
PLATFORM=nrf52 cargo rthumbv7em blink # For an nRF52 DK board
PLATFORM=opentitan cargo rriscv32imc blink # For an OpenTitan board
For an unknown platform, you may have to create your own memory layout definition. Place the layout definition file at layout_<platform>.ld and do not forget to enhance the tockloader_flags dispatching section in flash.sh. You are welcome to create a PR, s.t. the number of supported platforms grows.
The easiest way to start using libtock-rs is adding an example to the examples folder. The boiler plate code you would write is
#![no_std] use libtock::result::TockResult; #[libtock::main] async fn main() -> TockResult<()> { // Your code }
If you want to use heap based allocation you will have to add
extern crate alloc;
to the preamble and store your example in the examples-alloc folder.
To run on the code on your board you can use
PLATFORM=<platform> cargo r<arch> <your_app> [--features=alloc]
This script does the following steps for you:
Instead of specifying an environment variable each time you can permanently configure your platform by writing its name into a file named platform, e.g.
echo nrf52 > platform
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