feat(common): Improve native IO API

[clabby]

Overview

Right now, the IO API for the native platform in kona-common is inherently unsafe. Though, because it is behind the BasicKernelInterface trait, the API is not actually marked as unsafe lexically.

The reason the API is currently unsafe is because of our use of raw file descriptors. The FileDescriptor enum for the FPVM target is constant, and it is also Clone + Copy. However, on the native platform, file descriptors cannot be safely cloned or copied without checking for potential issues with creating a second handle to the fd.

This has resulted in a hacky workaround, where we hold onto the raw file descriptor, expect the host process to keep them alive for long enough, and construct + forget the file for read and write ops. While this works, the API is very unclear, and this invisible requirement of having the host keep the file descriptors alive is a bit annoying.

Instead, we should treat the FileDescriptor enum as an owned type. Cloning or copying it should be a falliable operation, i.e. OwnedFd::try_clone.

This will help improve the API to expose a truly safe native IO API, and prevent us from having to leak the Files in NativeIO.

[malik672]

@clabby this should work if a try_clone() is implemented right ?

[clabby]

@clabby this should work if a try_clone() is implemented right ?

We could definitely go that route, however it will be a fairly large API change. Right now, we assume the FileDescriptor enum is Copy, and the API is built up around that.

Ideally, we can move towards a TryCloneable type, though, and pass references through the preimage oracle / low-level kona-common IO API.

[malik672]

@clabby this should work if a try_clone() is implemented right ?

We could definitely go that route, however it will be a fairly large API change. Right now, we assume the FileDescriptor enum is Copy, and the API is built up around that.

Ideally, we can move towards a TryCloneable type, though, and pass references through the preimage oracle / low-level kona-common IO API.

Both approaches can work, and we can simply call the try_clone()inside the I/O functions when we want to duplicate, since we will only be duplicating when needed, something like: fd.try_clone()