Experimental kernel for embedded devices written in Rust

Last update: Dec 13, 2022

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Overview

bkernel is an experimental kernel for embedded devices written in Rust. I'm mostly trying out Rust now to see how it applies to kernel development.

Prerequisites

Note for Nix users

There is shell.nix for you. Just drop in with nix-shell and all dependencies are there (including nightly rust).

Note: it won't work for platforms other than x86-64_linux. You should change rust-nightly hash in shell.nix.

gcc-arm-none-eabi toolchain

You need an gcc-arm-none-eabi toolchain before you can build the kernel.

If you don't know where to get one, you can get it there:

Download one for your platform
Unpack
Add <path_to_toolchain>/bin to your $PATH variable

Rust version

This project needs lots of nightly features:

asm
core intrinsics
const fn
lang items
allocator
conservative impl trait
integer atomics
fixed size array

Nightly builds are not backward-compatible, so only the latest version is supported (it changes every 6 weeks). That's why you need a reasonably up-to-date nightly rust.

Rust sources

bkernel needs Rust sources to build libcore for the target. If you don't have one, don't worry: it will be automatically downloaded to rust directory.

If you have Rust git repo on you computer, you can point to it with:

export RUSTDIR=/path/to/rust

Note: building bkernel will checkout rust to a commit your rustc was compiled with.

Build instructions

Just invoke make.

Make targets

make build all binaries, documentation and run tests;
make build only build kernel;
make test run tests;
make doc build documentation;
make flash flash kernel;
make reset reset the device;
make device_test run device tests. $DEVICE can be set to point to the device tty (defaults to /dev/ttyUSB0).

Running

After booting the kernel you should see all LEDs are turned on and a terminal is running on PB6/PB7 pins.

The following commands are supported:

hi - says hello
+3/-3/+4/-4/+5/-5/+6/-6 - turn on/off LD3/4/5/6
temp - read temperature and humidity from HTU21D sensor
panic - throw a panic
help - for more commands

Device tests

There are device tests that are executed with expect. It must be installed on your system.

You must flash the device before testing.

To run device tests, execute:

make device_test

make device_test DEVICE=/dev/ttyUSB0

Note: device path can be different on your platform.

Issues

If you have any issues or questions with the bkernel, just open an issue or mail me at [email protected].

License

The bkernel source code is licensed by a modified GNU General Public License - the modification taking a form of an exception. The exception permits the source code of applications that use bkernel and are distributed as executables to remain closed source, thus permitting the use of bkernel in commercial applications without necessitating that the whole application be open sourced. The exception can only be used if you wish to combine bkernel with a proprietary product, and you comply with the terms stated in the exception itself.

The full text of the bkernel license is available here.

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Comments

error[E0277]: the trait bound `core::cell::Cell<*mut bscheduler::Task<'static>>: core::marker::Sync` is not satisfied

I used nix-shell and then just make. it ended up with the following:

[nix-shell:~/home/dev/bkernel]$ make
git clone https://github.com/rust-lang/rust
Cloning into 'rust'...
remote: Counting objects: 616556, done.
remote: Compressing objects: 100% (3/3), done.
remote: Total 616556 (delta 0), reused 0 (delta 0), pack-reused 616553
Receiving objects: 100% (616556/616556), 283.88 MiB | 1.29 MiB/s, done.
Resolving deltas: 100% (497849/497849), done.
Checking connectivity... done.
cd rust && [ "$(git rev-parse HEAD)" = "a059cb2f3344c0a9efae17dde3d0e16a55ce93db" ] || git checkout -q a059cb2f3344c0a9efae17dde3d0e16a55ce93db || ( git fetch && git checkout -q a059cb2f3344c0a9efae17dde3d0e16a55ce93db )
mkdir -p lib/thumbv7em-none-eabi
rustc -g -Z no-landing-pads --target thumbv7em-none-eabi -C opt-level=3 -L lib/thumbv7em-none-eabi rust/src/libcore/lib.rs --out-dir lib/thumbv7em-none-eabi
rustc -g -Z no-landing-pads --target thumbv7em-none-eabi -C opt-level=3 -L lib/thumbv7em-none-eabi rust/src/liballoc/lib.rs --out-dir lib/thumbv7em-none-eabi
cargo rustc --target=thumbv7em-none-eabi --release -- -Z no-landing-pads
    Updating registry `https://github.com/rust-lang/crates.io-index`
   Compiling bscheduler v0.0.1 (file:///home/rosen/home/dev/bkernel/bscheduler)
   Compiling smalloc v0.0.1 (file:///home/rosen/home/dev/bkernel/smalloc)
   Compiling stm32f4 v0.0.1 (file:///home/rosen/home/dev/bkernel/stm32f4)
   Compiling bkernel v0.0.1 (file:///home/rosen/home/dev/bkernel)
   Compiling linkmem v0.1.0 (file:///home/rosen/home/dev/bkernel/linkmem)
error[E0277]: the trait bound `core::cell::Cell<*mut bscheduler::Task<'static>>: core::marker::Sync` is not satisfied
 --> src/scheduler.rs:6:1
  |
6 | static SCHEDULER: Scheduler<'static> = Scheduler::new();
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ trait `core::cell::Cell<*mut bscheduler::Task<'static>>: core::marker::Sync` not satisfied
  |
  = note: `core::cell::Cell<*mut bscheduler::Task<'static>>` cannot be shared between threads safely
  = note: required because it appears within the type `bscheduler::Scheduler<'static>`
  = note: shared static variables must have a type that implements `Sync`

error[E0277]: the trait bound `core::cell::Cell<u32>: core::marker::Sync` is not satisfied
 --> src/scheduler.rs:6:1
  |
6 | static SCHEDULER: Scheduler<'static> = Scheduler::new();
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ trait `core::cell::Cell<u32>: core::marker::Sync` not satisfied
  |
  = note: `core::cell::Cell<u32>` cannot be shared between threads safely
  = note: required because it appears within the type `bscheduler::Scheduler<'static>`
  = note: shared static variables must have a type that implements `Sync`

error: aborting due to 2 previous errors

error: Could not compile `bkernel`.

To learn more, run the command again with --verbose.
Makefile:35: recipe for target 'target/thumbv7em-none-eabi/release/libkernel.a' failed
make: *** [target/thumbv7em-none-eabi/release/libkernel.a] Error 101

opened by rosenk 3

The scope of the unsafe block can be appropriately reduced

In this function you use the unsafe keyword for almost the entrie function body.

We need to mark unsafe operations more precisely using unsafe keyword. Keeping unsafe blocks small can bring many benefits. For example, when mistakes happen, we can locate any errors related to memory safety within an unsafe block. This is the balance between Safe and Unsafe Rust. The separation is designed to make using Safe Rust as ergonomic as possible, but requires extra effort and care when writing Unsafe Rust. @rasendubi Hope this PR can help you. Best regards. References https://doc.rust-lang.org/nomicon/safe-unsafe-meaning.html https://doc.rust-lang.org/book/ch19-01-unsafe-rust.html

opened by peamaeq 0