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

ludfjig · 2026-02-24T22:38:49Z

src/wasm_runtime/src/module.rs

    register_function(GuestFunctionDefinition::new(
        "InitWasmRuntime".to_string(),
-        vec![],
+        vec![ParameterType::VecBytes],


Not strictly related to your PR, but can we use the #[guest_func] macro on init_wasm_runtime instead of manually calling register_function?

maybe teh same applies to all usages of register_function

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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Copilot · 2026-02-24T22:48:49Z

src/hyperlight_wasm/src/sandbox/proto_wasm_sandbox.rs

+        // Track the host function definition for pushing to guest at load time
+        self.host_function_definitions.push(HostFunctionDefinition {
+            function_name: name.to_string(),
+            parameter_types: Some(Args::TYPE.to_vec()),
+            return_type: Output::TYPE,
+        });


host_function_definitions is built by blindly pushing entries, but you also pre-seed it with a HostPrint definition in new(). If a caller later registers a host function named HostPrint via register(...)/register_host_function(...), the list will contain duplicates and the guest init_wasm_runtime will attempt to linker.func_new the same name twice, which should error and prevent the runtime from loading. Consider enforcing uniqueness by name (e.g., replace existing definition instead of pushing, or special-case HostPrint).

Suggested change

// Track the host function definition for pushing to guest at load time

self.host_function_definitions.push(HostFunctionDefinition {

function_name: name.to_string(),

parameter_types: Some(Args::TYPE.to_vec()),

return_type: Output::TYPE,

});

// Track the host function definition for pushing to guest at load time,

// ensuring uniqueness by function name.

if let Some(existing) = self

.host_function_definitions

.iter_mut()

.find(|def| def.function_name == name)

{

existing.parameter_types = Some(Args::TYPE.to_vec());

existing.return_type = Output::TYPE;

} else {

self.host_function_definitions

.push(HostFunctionDefinition {

function_name: name.to_string(),

parameter_types: Some(Args::TYPE.to_vec()),

return_type: Output::TYPE,

});

}

I did think about this, but wasn't sure what the best thing to do was. Anyone have any thoughts? This feels like it could lead to some strange bugs as well

Copilot · 2026-02-24T22:48:50Z

src/hyperlight_wasm/src/sandbox/proto_wasm_sandbox.rs

+        // Track the host function definition for pushing to guest at load time
+        self.host_function_definitions.push(HostFunctionDefinition {
+            function_name: name.as_ref().to_string(),
+            parameter_types: Some(Args::TYPE.to_vec()),
+            return_type: Output::TYPE,
+        });


The logic to append a HostFunctionDefinition is duplicated in both Registerable::register_host_function and the inherent ProtoWasmSandbox::register method. This duplication makes it easy for the two paths to drift (e.g., one adds de-dup or normalization and the other doesn’t). Consider extracting a small helper (or having one method delegate to the other) so the tracking behavior stays consistent.

Copilot · 2026-02-24T22:48:50Z

src/wasm_runtime/src/module.rs

+        _ => {
+            return Err(HyperlightGuestError::new(
+                ErrorCode::GuestFunctionParameterTypeMismatch,
+                "InitWasmRuntime: first parameter must be VecBytes".to_string(),
+            ))
+        }


When parameters is present but empty, this returns "InitWasmRuntime: first parameter must be VecBytes", which is a bit misleading (the real issue is that no parameters were provided). Consider explicitly handling the empty-vec case and returning a clearer error (e.g., "expected 1 parameter") to make debugging host/guest ABI mismatches easier.

Suggested change

_ => {

return Err(HyperlightGuestError::new(

ErrorCode::GuestFunctionParameterTypeMismatch,

"InitWasmRuntime: first parameter must be VecBytes".to_string(),

))

}

Some(_) => {

return Err(HyperlightGuestError::new(

ErrorCode::GuestFunctionParameterTypeMismatch,

"InitWasmRuntime: first parameter must be VecBytes".to_string(),

))

}

None => {

return Err(HyperlightGuestError::new(

ErrorCode::GuestFunctionParameterTypeMismatch,

"InitWasmRuntime: expected 1 parameter".to_string(),

))

}

jsturtevant added 2 commits February 24, 2026 14:24

jsturtevant added the kind/bugfix label Feb 24, 2026

ludfjig approved these changes Feb 24, 2026

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Remove host function definition region dependency #389

Remove host function definition region dependency #389
jsturtevant wants to merge 2 commits intohyperlight-dev:mainfrom
jsturtevant:rally/388-remove-host-function-definition-region

jsturtevant commented Feb 24, 2026

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jsturtevant commented Feb 24, 2026

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Pull request overview

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