Add host component bindgen macros

Cargo.toml

@@ -8,6 +8,8 @@ default-members = [
 members = [
     "src/hyperlight_guest_capi",
     "fuzz",
+    "src/hyperlight_component_util",
+    "src/hyperlight_component_macro",
 ]
 # Guests have custom linker flags, so we need to exclude them from the workspace
 exclude = [
@@ -30,6 +32,8 @@ hyperlight-common = { path = "src/hyperlight_common", version = "0.2.0", default
 hyperlight-host = { path = "src/hyperlight_host", version = "0.2.0", default-features = false }
 hyperlight-guest = { path = "src/hyperlight_guest", version = "0.2.0", default-features = false }
 hyperlight-testing = { path = "src/hyperlight_testing", default-features = false }
+hyperlight-component-util = { path = "src/hyperlight_component_util" }
+hyperlight-component-macro = { path = "src/hyperlight_component_macro" }
 
 [workspace.lints.rust]
 unsafe_op_in_unsafe_fn = "deny"

src/hyperlight_common/Cargo.toml

@@ -21,10 +21,12 @@ log = "0.4.26"
 tracing = { version = "0.1.41", optional = true }
 strum = {version = "0.27",  default-features = false, features = ["derive"]}
 arbitrary = {version = "1.4.1", optional = true, features = ["derive"]}
+spin = "0.9.8"
 
 [features]
 default = ["tracing"]
 fuzzing = ["dep:arbitrary"]
+std = []
 
 [dev-dependencies]
 hyperlight-testing = { workspace = true }

src/hyperlight_common/src/lib.rs

@@ -36,3 +36,5 @@ pub mod flatbuffer_wrappers;
 mod flatbuffers;
 /// cbindgen:ignore
 pub mod mem;
+
+pub mod resource;

src/hyperlight_common/src/resource.rs

@@ -0,0 +1,154 @@
+//! Shared operations around resources
+
+// "Needless" lifetimes are useful for clarity
+#![allow(clippy::needless_lifetimes)]
+
+use alloc::sync::Arc;
+
+#[cfg(feature = "std")]
+extern crate std;
+use core::marker::{PhantomData, Send};
+use core::ops::Deref;
+#[cfg(feature = "std")]
+use std::sync::{RwLock, RwLockReadGuard};
+
+#[cfg(not(feature = "std"))]
+use spin::{RwLock, RwLockReadGuard};
+
+/// The semantics of component model resources are, pleasingly,
+/// roughly compatible with those of Rust. Less pleasingly, it's not
+/// terribly easy to show that statically.
+///
+/// In particular, if the host calls into the guest and gives it a
+/// borrow of a resource, reentrant host function calls that use that
+/// borrow need to be able to resolve the original reference and use
+/// it in an appropriately scoped manner, but it is not simple to do
+/// this, because the core Hyperlight machinery doesn't offer an easy
+/// way to augment the host's context for the span of time of a guest
+/// function call.  This may be worth revisiting at some time, but in
+/// the meantime, it's easier to just do it dynamically.
+///
+/// # Safety
+/// Informally: this only creates SharedRead references, so having a
+/// bunch of them going at once is fine.  Safe Rust in the host can't
+/// use any earlier borrows (potentially invalidating these) until
+/// borrow passed into [`ResourceEntry::lend`] has expired.  Because
+/// that borrow outlives the [`LentResourceGuard`], it will not expire
+/// until that destructor is called. That destructor ensures that (a)
+/// there are no outstanding [`BorrowedResourceGuard`]s alive (since
+/// they would be holding the read side of the [`RwLock`] if they
+/// were), and that (b) the shared flag has been set to false, so
+/// [`ResourceEntry::borrow`] will never create another borrow
+pub enum ResourceEntry<T> {
+    Empty,
+    Owned(T),
+    Borrowed(Arc<RwLock<bool>>, *const T),
+}
+unsafe impl<T: Send> Send for ResourceEntry<T> {}
+
+pub struct LentResourceGuard<'a> {
+    flag: Arc<RwLock<bool>>,
+    already_revoked: bool,
+    _phantom: core::marker::PhantomData<&'a mut ()>,
+}
+impl<'a> LentResourceGuard<'a> {
+    pub fn revoke_nonblocking(&mut self) -> bool {
+        #[cfg(feature = "std")]
+        let Ok(mut flag) = self.flag.try_write() else {
+            return false;
+        };
+        #[cfg(not(feature = "std"))]
+        let Some(mut flag) = self.flag.try_write() else {
+            return false;
+        };
+        *flag = false;
+        self.already_revoked = true;
+        true
+    }
+}
+impl<'a> Drop for LentResourceGuard<'a> {
+    fn drop(&mut self) {
+        if !self.already_revoked {
+            #[allow(unused_mut)] // it isn't actually unused
+            let mut guard = self.flag.write();
+            #[cfg(feature = "std")]
+            // If a mutex that is just protecting us from our own
+            // mistakes is poisoned, something is so seriously
+            // wrong that dying is a sensible response.
+            #[allow(clippy::unwrap_used)]
+            {
+                *guard.unwrap() = false;
+            }
+            #[cfg(not(feature = "std"))]
+            {
+                *guard = false;
+            }
+        }
+    }
+}
+pub struct BorrowedResourceGuard<'a, T> {
+    _flag: Option<RwLockReadGuard<'a, bool>>,
+    reference: &'a T,
+}
+impl<'a, T> Deref for BorrowedResourceGuard<'a, T> {
+    type Target = T;
+    fn deref(&self) -> &T {
+        self.reference
+    }
+}
+impl<T> ResourceEntry<T> {
+    pub fn give(x: T) -> ResourceEntry<T> {
+        ResourceEntry::Owned(x)
+    }
+    pub fn lend<'a>(x: &'a T) -> (LentResourceGuard<'a>, ResourceEntry<T>) {
+        let flag = Arc::new(RwLock::new(true));
+        (
+            LentResourceGuard {
+                flag: flag.clone(),
+                already_revoked: false,
+                _phantom: PhantomData {},
+            },
+            ResourceEntry::Borrowed(flag, x as *const T),
+        )
+    }
+    pub fn borrow<'a>(&'a self) -> Option<BorrowedResourceGuard<'a, T>> {
+        match self {
+            ResourceEntry::Empty => None,
+            ResourceEntry::Owned(t) => Some(BorrowedResourceGuard {
+                _flag: None,
+                reference: t,
+            }),
+            ResourceEntry::Borrowed(flag, t) => {
+                let guard = flag.read();
+                // If a mutex that is just protecting us from our own
+                // mistakes is poisoned, something is so seriously
+                // wrong that dying is a sensible response.
+                #[allow(clippy::unwrap_used)]
+                let flag = {
+                    #[cfg(feature = "std")]
+                    {
+                        guard.unwrap()
+                    }
+                    #[cfg(not(feature = "std"))]
+                    {
+                        guard
+                    }
+                };
+                if *flag {
+                    Some(BorrowedResourceGuard {
+                        _flag: Some(flag),
+                        reference: unsafe { &**t },
+                    })
+                } else {
+                    None
+                }
+            }
+        }
+    }
+    pub fn take(&mut self) -> Option<T> {
+        match core::mem::replace(self, ResourceEntry::Empty) {
+            ResourceEntry::Owned(t) => Some(t),
+            _ => None,
+        }
+    }
+}

src/hyperlight_component_macro/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "hyperlight-component-macro"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+homepage.workspace = true
+repository.workspace = true
+readme.workspace = true
+description = """
+Procedural macros to generate Hyperlight host and guest bindings from component types
+"""
+
+[lib]
+name = "hyperlight_component_macro"
+proc-macro = true
+
+[dependencies]
+wasmparser = { version = "0.224.0" }
+quote = { version = "1.0.38" }
+proc-macro2 = { version = "1.0.93" }
+syn = { version = "2.0.96" }
+itertools = { version = "0.14.0" }
+prettyplease = { version = "0.2.31" }
+hyperlight-component-util = { workspace = true }

src/hyperlight_component_macro/src/lib.rs

@@ -0,0 +1,18 @@
+extern crate proc_macro;
+
+use hyperlight_component_util::*;
+
+#[proc_macro]
+pub fn host_bindgen(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let path: Option<syn::LitStr> = syn::parse_macro_input!(input as Option<syn::LitStr>);
+    let path = path
+        .map(|x| x.value().into())
+        .unwrap_or_else(|| std::env::var_os("HYPERLIGHT_WASM_WORLD").unwrap());
+    util::read_wit_type_from_file(path, |kebab_name, ct| {
+        let decls = emit::run_state(false, |s| {
+            rtypes::emit_toplevel(s, &kebab_name, ct);
+            host::emit_toplevel(s, &kebab_name, ct);
+        });
+        util::emit_decls(decls).into()
+    })
+}

src/hyperlight_component_util/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "hyperlight-component-util"
+version.workspace = true
+edition.workspace = true
+rust-version.workspace = true
+license.workspace = true
+homepage.workspace = true
+repository.workspace = true
+readme.workspace = true
+description = """
+Shared implementation for the procedural macros that generate Hyperlight host and guest bindings from component types
+"""
+
+[lib]
+name = "hyperlight_component_util"
+
+[dependencies]
+wasmparser = { version = "0.224.0" }
+quote = { version = "1.0.38" }
+proc-macro2 = { version = "1.0.93" }
+syn = { version = "2.0.96" }
+itertools = { version = "0.14.0" }
+prettyplease = { version = "0.2.31" }