No way to test guest syscall code

[lrettig]

Right now this code is cfg-gated, both in the SDK:

athena/vm/sdk/src/lib.rs

Lines 6 to 18 in 461e631

	cfg_if! {
	if #[cfg(target_os = "zkvm")] {
	mod spawn;
	pub use spawn::spawn;
	mod call;
	pub use call::call;
	mod deploy;
	pub use deploy::deploy;
	mod io;
	pub use io::read_storage;
	pub use io::write_storage;
	}
	}

as well as in the underlying syscode implementation:

athena/vm/entrypoint/src/syscalls/host.rs

Lines 18 to 42 in 461e631

	pub fn call(
	address: *const u32,
	input_ptr: *const u32,
	input_len: usize,
	method_ptr: *const u32,
	method_len: usize,
	amount: *const u32,
	) {
	#[cfg(target_os = "zkvm")]
	unsafe {
	asm!(
	"ecall",
	in("t0") crate::syscalls::HOST_CALL,
	in("a0") address,
	in("a1") input_ptr,
	in("a2") input_len,
	in("a3") method_ptr,
	in("a4") method_len,
	in("a5") amount,
	)
	}
	#[cfg(not(target_os = "zkvm"))]
	unreachable!()
	}

The former won't even compile for the host; the latter will compile but can't be executed.

@poszu any ideas how we can allow testing of this code?

Related: #109, #107

[poszu]

I'm unsure, they would need to be executed in a VM. However, this code is just a few lines of raw assembly. I think we can get away with reviewing these functions "with eyes" and depending on all other tests to execute them for now.