Crate risc0_build
source ·Expand description
Build RISC Zero zkVM guest code and provide handles to the host side
In order for the host to execute guest code in the RISC Zero zkVM, the host must be provided a compiled RISC-V ELF file and the corresponding MethodID. This crate contains the functions needed to take zkVM guest code, build a corresponding ELF file and MethodID, and make the MethodID and a path to the ELF file available for the host to use.
Using risc0-build to build guest methods
Using this crate can be a bit delicate, so we encourage you to follow along
in our RISC Zero Rust Starter repository.
In that repository, risc0-build
is used in the
methods
directory.
Guest methods are embedded for the host to use by calling embed_methods
(or embed_methods_with_options) in a build script.
An example build.rs
file would look like
fn main() {
risc0_build::embed_methods();
}
This requires including risc0-build
as a build dependency. You will also
need add a [package.metadata.risc0]
section to your cargo file. In this
section, put a methods
field with a list of relative paths containing the
guest code. For example, if your guest code is in the guest
directory,
then Cargo.toml
might include
[build-dependencies]
risc0-build = "1.0.0-rc.1"
[package.metadata.risc0]
methods = ["guest"]
This builds a file methods.rs
in your cargo output directory which you
must then include for the host to use. For example, you might make a file
src/lib.rs
containing
include!(concat!(env!("OUT_DIR"), "/methods.rs"));
This process will generate a method ID (*_ID
) and a path to an ELF file
(*_PATH
). The names will be derived from the name of the file containing
the guest method, which will be converted to ALL_CAPS to comply with rust
naming conventions. Thus, in the starter example,
where the guest method is in
multiply.rs
,
the method ID is named methods::MULTIPLY_ID
and the path to the ELF file
is named methods::MULTIPLY_PATH
.
These are included at the beginning of the
host code:
use methods::{MULTIPLY_ID, MULTIPLY_PATH};
Structs
embed_methods_with_options
.