runtime/README.md

# Reborn Runtime
This is a simple program allowing ARM32 code to easily call "native" code.

By running an ARM32 program inside this runtime, it gains the ability to call `raw_trampoline()`. This function copies its arguments and passes them to the "host" code.

The runtime also automatically uses QEMU on non-ARM systems.

## Terminology
- "Guest" code is the main ARM32 program. It is running inside the runtime.
- "Host" code is the native code located in `libtrampoline.so`. It is running "alongside" the runtime.

## Example
There is a simple C example [here](./example).

## Syscall Vs. Pipe Trampolines
The runtime supports two methods of passing data between the guest and host.
- System Call
  - Data is passed through a custom system-call added to QEMU.
  - Only supported on x86_64.
- Pipes
  - Data is passed through standard UNIX pipes.
  - Can be forced using an environmental variable.

## Licensing
The runtime itself is licensed with [GPLv2](./LICENSE) to comply with [QEMU's license](https://wiki.qemu.org/License). However, the `lib` directory is licensed with the [Unlicense](lib/LICENSE) as it does not directly link to the runtime.