Make Linux shim generic on file system

[CvvT]

I was trying to add 9p fs and use it for SNP runner, then I realized our Linux shim decides the fs to use not runner. This PR makes Linux shim generic on fs so that runner can pick whatever fs.

[jaybosamiya-ms]

Thanks Weiteng, this is similar to a (broader) refactoring I was planning do but haven't had a chance to finish it up. There are some minor cleanups possible here, but I don't want to block you especially since I plan to do some of that cleanup later on anyways. Please feel free to merge, thanks!

[jaybosamiya-ms]

This portion is the key change, as I understand it, right?

This is similar to a (broader) refactoring I was planning do but haven't had a chance to finish it up. That refactoring can build on top of this one and can clean it up, so please feel free to merge this as is.

[jaybosamiya-ms]

I assume you've already tested this, but any particular reason it needs to be Send + Sync + 'static? Can we relax any/all of them? It'd be nice to have it be the weakest requirements needed. If it cannot be weakened by removing those traits, that is fine, but just checking.

[CvvT]

'static is required by Box

litebox/litebox_shim_linux/src/syscalls/process.rs

Lines 550 to 568 in 1e6a790

	struct NewThreadArgs<FS: ShimFS> {
	/// Task struct that maintains all per-thread data
	task: Task<FS>,
	}
	impl<FS: ShimFS> litebox::shim::InitThread for NewThreadArgs<FS> {
	type ExecutionContext = litebox_common_linux::PtRegs;
	fn init(
	self: alloc::boxed::Box<Self>,
	) -> alloc::boxed::Box<dyn litebox::shim::EnterShim<ExecutionContext = Self::ExecutionContext>>
	{
	let Self { task } = *self;
	Box::new(crate::LinuxShimEntrypoints {
	task,
	_not_send: core::marker::PhantomData,
	})
	}

Send and Sync are required by Arc in multiple places for sharing across threads, e.g.,

litebox/litebox_shim_linux/src/syscalls/epoll.rs

Line 43 in 1e6a790

Unix(Arc<crate::syscalls::unix::UnixSocket<FS>>),

[github-actions]

🤖 SemverChecks 🤖 ⚠️ Potential breaking API changes detected ⚠️

Click for details

--- failure trait_requires_more_generic_type_params: trait now requires more generic type parameters ---

Description:
A trait now requires more generic type parameters than it used to. Uses of this trait that supplied the previously-required number of generic types will be broken. To fix this, consider supplying default values for newly-added generic types.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-new-parameter-no-default
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.46.0/src/lints/trait_requires_more_generic_type_params.ron

Failed in:
  trait LinuxShim (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:222
  trait LinuxShimBuilder (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:143
  trait LinuxShimEntrypoints (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:78
  trait LoadedProgram (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:300

--- failure type_requires_more_generic_type_params: type now requires more generic type parameters ---

Description:
A type now requires more generic type parameters than it used to. Uses of this type that supplied the previously-required number of generic types will be broken. To fix this, consider supplying default values for newly-added generic types.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#trait-new-parameter-no-default
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.46.0/src/lints/type_requires_more_generic_type_params.ron

Failed in:
  Struct LinuxShim (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:222
  Struct LinuxShimBuilder (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:143
  Struct LinuxShimEntrypoints (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:78
  Struct LoadedProgram (0 -> 1 required generic types) in /home/runner/work/litebox/litebox/litebox_shim_linux/src/lib.rs:300