29 lines
1.5 KiB
Markdown
29 lines
1.5 KiB
Markdown
# Reborn Runtime
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This is a simple program allowing ARM32 code to easily call "native" code.
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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 `trampoline` function inside `libmedia-layer-trampoline.so`.
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The runtime also automatically uses QEMU on x86_64 systems.
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## Terminology
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- "Guest" code is the main ARM32 program.
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- "Host" code is the native code located in `libmedia-layer-trampoline.so`.
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## Example
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There is a simple C example [here](./example). It sends a given string to the host, which returns the string's length multiplied by two.
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## Early Returning
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`raw_trampoline` supports returning before the host code has finished executing. This can be enabled by passing `true` to `allow_early_return`. However, this is only supported in certain circumstances, can cause race-conditions, and prevents the guest code from receiving the host's return value.
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## Syscall Versus Pipe Trampolines
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The runtime supports two methods of passing data between the guest and host.
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- System Call
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- Data is passed through a custom system-call added to QEMU.
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- Only supported on x86_64.
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- Pipes
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- Data is passed through standard UNIX pipes.
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- Supports early-returning.
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- Can be forced using an environmental variable.
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## Licensing
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The runtime itself is licensed with [GPLv2](./LICENSE) to comply with QEMU's license. However, the `raw_trampoline` function and associated headers are licensed with the [Unlicense](lib/LICENSE) as they do not directly link to the runtime. |