Remove host function definition region dependency by jsturtevant · Pull Request #389 · hyperlight-dev/hyperlight-wasm

jsturtevant · 2026-02-24T22:30:58Z

Instead of using a shared memory region or a host function callback
to provide host function definitions to the guest, the host now pushes
the serialized definitions directly as a parameter to InitWasmRuntime.

fixes #388

Instead of using a shared memory region or a host function callback to provide host function definitions to the guest, the host now pushes the serialized definitions directly as a parameter to InitWasmRuntime. Signed-off-by: James Sturtevant <jsturtevant@gmail.com>

rust_wasm_samples, hyperlight_wasm_macro, and component_sample were missing empty [workspace] tables in their Cargo.toml files. Without this, Cargo resolves to the main checkout's workspace root when run from a git worktree, causing 'believes it's in a workspace' errors. wasm_runtime already had this marker. Signed-off-by: James Sturtevant <jsturtevant@gmail.com>

ludfjig

I think this looks good

src/wasm_runtime/src/module.rs

Copilot

Pull request overview

This PR removes the guest’s dependency on a dedicated “host function definition region” by having the host serialize host function definitions and pass them directly into the guest’s InitWasmRuntime call, aligning with upstream HL-core changes (issue #388).

Changes:

Update the guest wasm runtime to parse HostFunctionDetails from InitWasmRuntime parameters (VecBytes) instead of reading from a shared region / callback.
Update the host sandbox initialization to track + serialize registered host function definitions and pass them into InitWasmRuntime.
Remove SandboxBuilder::with_function_definition_size and document the breaking change; add [workspace] stanzas to excluded crates to avoid workspace resolution issues.

Reviewed changes

Copilot reviewed 12 out of 13 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/wasm_runtime/src/module.rs	`InitWasmRuntime` now expects a VecBytes parameter containing serialized host function details and registers host funcs from it.
src/wasm_runtime/src/hostfuncs.rs	Removes the old `get_host_function_details()` path.
src/wasm_runtime/src/component.rs	Updates `InitWasmRuntime` signature in the component runtime interface (now takes VecBytes).
src/hyperlight_wasm/src/sandbox/proto_wasm_sandbox.rs	Tracks host function definitions as they’re registered; serializes and passes them to `InitWasmRuntime`.
src/hyperlight_wasm/src/sandbox/sandbox_builder.rs	Removes the builder API for host function definition region sizing.
src/hyperlight_wasm/src/sandbox/loaded_wasm_sandbox.rs	Adds a regression test ensuring missing host functions fail module load.
src/hyperlight_wasm/Cargo.toml	Adds `hyperlight-common` dependency used for flatbuffer wrapper types.
Cargo.toml	Adds `hyperlight-common` to workspace dependencies.
Cargo.lock	Locks `hyperlight-common` dependency.
src/rust_wasm_samples/Cargo.toml	Adds `[workspace]` to make the crate a standalone workspace root when built directly.
src/hyperlight_wasm_macro/Cargo.toml	Adds `[workspace]` to make the crate a standalone workspace root when built directly.
src/component_sample/Cargo.toml	Adds `[workspace]` to make the crate a standalone workspace root when built directly.
CHANGELOG.md	Documents the breaking removal of `SandboxBuilder::with_function_definition_size`.

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src/hyperlight_wasm/src/sandbox/proto_wasm_sandbox.rs

src/wasm_runtime/src/module.rs

Signed-off-by: James Sturtevant <jsturtevant@gmail.com>

dblnz

LGTM!
I left some small comments that are not necessary to be addressed in this PR.

dblnz · 2026-03-05T08:52:49Z

src/component_sample/Cargo.toml


 [package.metadata.component.target.dependencies]

+[workspace] # indicate that this crate is not part of any workspace


This is to avoid building it with the main workspace?

dblnz · 2026-03-05T09:08:21Z

src/hyperlight_wasm_macro/Cargo.toml

 prettyplease = { version = "0.2.37" }
 hyperlight-component-util = { version = "0.12.0" }
+
+[workspace] # indicate that this crate is not part of any workspace


The same reason as the other added [workspace], to avoid building with the entire project?

I think these were already in the exclude table in the workspace root Cargo.toml, which means that it was just a bit broken to have that but not this.

dblnz · 2026-03-05T09:14:03Z

src/wasm_runtime/src/module.rs


 #[instrument(skip_all, level = "Info")]
-fn init_wasm_runtime() -> Result<Vec<u8>> {
+fn init_wasm_runtime(function_call: &FunctionCall) -> Result<Vec<u8>> {


Nit: This could be done in another PR for all guest functions, but as we've touched this, can we switch to using the macros?
I think it'll be a nicer format, easier for reviewing changes and removes the need for checking the FunctionCall ourselves.

#[guest_function("InitWasmRuntime")] fn init_wasm_runtime(hfd: hostfuncs::HostFunctionDetails) -> i32 {

Note: I am not sure the deserialization to HostFunctionDetails will work out of the box, but still, a big part of the logic below goes awa.

I've just seen the comment Ludvig left about this, it's on the same thing, so disregard it

syntactically

Mostly LGTM, except for the comment about HostPrint.

syntactically · 2026-03-05T13:24:57Z

src/hyperlight_wasm/src/sandbox/proto_wasm_sandbox.rs

-        Ok(Self { inner: Some(inner) })
+
+        // HostPrint is always registered by UninitializedSandbox, so include it by default
+        let host_function_definitions = vec![HostFunctionDefinition {


I'm not convinced this should be here. HostPrint is sort of an internal implementation detail? I don't think that wasm modules should be able to just import it automatically with no way to remove that.

syntactically · 2026-03-05T13:36:05Z

src/hyperlight_wasm/src/sandbox/proto_wasm_sandbox.rs


+use hyperlight_common::flatbuffer_wrappers::function_types::{ParameterType, ReturnType};
+use hyperlight_common::flatbuffer_wrappers::host_function_definition::HostFunctionDefinition;
+use hyperlight_common::flatbuffer_wrappers::host_function_details::HostFunctionDetails;


I guess the only place where these structs cross the host/guest boundary is now hlwasm/hljs downstreams, which makes it feel a little weird that they are still defined in hlcommon. I don't think we need to do anything about this right now since IIRC it's pretty urgent to get this in so we can prepare for release, but perhaps it's worth thinking about...

syntactically · 2026-03-05T13:37:23Z

src/hyperlight_wasm_macro/Cargo.toml

 prettyplease = { version = "0.2.37" }
 hyperlight-component-util = { version = "0.12.0" }
+
+[workspace] # indicate that this crate is not part of any workspace


I think these were already in the exclude table in the workspace root Cargo.toml, which means that it was just a bit broken to have that but not this.

jsturtevant added 2 commits February 24, 2026 14:24

jsturtevant added the kind/bugfix label Feb 24, 2026

ludfjig previously approved these changes Feb 24, 2026

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ludfjig requested a review from Copilot February 24, 2026 22:44

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jsturtevant mentioned this pull request Mar 3, 2026

use the #[guest_func] macro on init_wasm_runtime instead of manually calling register_function? #395

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Address feedback

c5b5956

Signed-off-by: James Sturtevant <jsturtevant@gmail.com>

jsturtevant dismissed ludfjig’s stale review via c5b5956 March 3, 2026 01:59

dblnz approved these changes Mar 5, 2026

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syntactically reviewed Mar 5, 2026

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		[package.metadata.component.target.dependencies]

		[workspace] # indicate that this crate is not part of any workspace

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jsturtevant commented Feb 24, 2026

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