how-to-build-a-hyperlight-guest-binary.md

Building a Hyperlight guest binary

This document explains how to build a binary to be used as a Hyperlight guest.

When building a guest, one needs to follow some rules so that the resulting binary can be used with Hyperlight:

• the binary must not use the standard library
• the expected entrypoint function signature is void hyperlight_main(void) or pub fn hyperlight_main()
• Hyperlight expects hl_Vec* c_guest_dispatch_function(const hl_FunctionCall *functioncall) or pub fn guest_dispatch_function(function_call: FunctionCall) -> Result<Vec<u8>> to be defined in the binary so that in case the host calls a function that is not registered by the guest, this function is called instead.
• to be callable by the host, a function needs to be registered by the guest in the hyperlight_main function.

Rust guest binary

In the case of a binary that is written in Rust, one needs to make use of the Hyperlight crate, hyperlight_guest that contains the types and APIs that enable the guest to:

• register functions that can be called by the host application
• call host functions that have been registered by the host.

C guest binary

For the binary written in C, the generated C bindings can be downloaded from the latest release page that contain: the hyperlight_guest.h header and the C API library. The hyperlight_guest.h header contains the corresponding APIs to register guest functions and call host functions from within the guest.