Cap-Build Preprocessor for Syscall Imports

[Latrasis]

As described in #141, see comment we need a cap9-build lib utility that:

• Decodes a .wasm module processed by wasm-build
• Searches for:

(import "env" "cap9_syscall_low" (func $env.storage_write (type $t0)))

• Replaces $cap9_syscall_low import declaration with a statically linked system-call with:

(func $cap9_syscall_low (type $t0) (param $p0 i32) (param $p1 i32) (param $p2 i32) (param $p3 i32) (result i32)
    call $env.gasleft
    call $env.sender
    get_local $p0
    get_local $p1
    get_local $p2
    get_local $p3
    call $env.dcall)

Lib

Library should be included in a separate cargo folder named: "cap9-build" and added as a dev-dependency in Cargo.toml. Use as a binary might not be necessary if integration tests allow using the lib as a dev-dependency.

Tests

Tests should be included:

• For cap9-build tests in kernel-ewasm/cap9-build/tests/
• For all other tests use cap9_build as a lib in kernel-ewasm/tests/**

[JakeOShannessy]

A quick note, "use a binary might not be necessary" if build.rs allows its use as a dev dependency. cap9-build is part of the workflow for creating procedures, not just tests (as with wasm-build). From the information in the pwasm tutorial it seems that build.rs doesn't support the necessary features for wasm-build (and therefore cap9-build) although I haven't investigated this thoroughly myself.

[Latrasis]

I was looking through how [ #link] attributes work, and I'm wondering if it's possible to statically import a wasm binary using the wasm_import_module attribute.

[Latrasis]

@JakeOShannessy This looks like it's completed?