Badger Kernel is a kernel providing multithreading on Arm platforms. (Badger because badgers have stripes and stripes are vaguely like threads)
A minimal userspace is included to show how to use the kernel and test its functionality. There is no filesystem, this is provided by semihosting.
Current targets are:
- Arm (Armv7A Cortex A-15 virt)
- Thumb (Armv7E-M Cortex-M4)
- AArch64 (Cortex A-57 virt, Raspberry Pi 4)
For implementation details see the design doc.
- Cooperative multitasking
- Timer based thread switching
- Loading ELF programs, including position independent code
- Message passing
- Mutexes and condition variables
- Thread local storage
- Memory allocation
- File handling (via semihosting)
- Signal handling
- Permissions and errno for error handling
- Access to thread registers for tracing
- User space threads (fibers)
- Stack under/overflow detection
Install cmake, ninja and an arm-none-eabi or aarch64-none-elf toolchain. Arm developer releases are the best way to get these.
AArch64:
Arm/Thumb:
Install QEMU with Arm support (comes with AArch64 as well):
sudo apt-get install qemu-system-arm
See the CI config for the currently tested versions of all of the tools.
Then configure and build according to which toolchain you installed:
cmake . -G Ninja -DBUILD_PLATFORM=aarch64
<or>
cmake . -G Ninja -DBUILD_PLATFORM=arm
<or>
cmake . -G Ninja -DBUILD_PLATFORM=thumb
ninja
Demos are how we test Badger Kernel. For example, to run the yielding demo:
ninja run_yielding
Each demo has run_<demo>, debug_<demo> and test_<demo> ninja targets.
To test all the demos use lit (https://pypi.org/project/lit/) or just run ninja.
For a full list see the demos.md.
There is a interactive shell, do ninja run_shell to use it. There's some basic commands provided and it can run loadable programs as commands. (see demos/shell for examples)
--------------------
----- BK Shell -----
--------------------
$ help
Builtins:
help quit run
Programs:
echo ps ls
$ help run
run <program name>
$ echo Hello Badger Kernel!
Hello Badger Kernel!
$ ps
| shell (0)
State | suspended (2)
Child | ps (1)
| ps (1)
State | running (1)
Parent | shell (0)