Import a data symbol for libdl.so

This commit replaces the `__wasm_set_libraries` protocol with a direct
data symbol import of the structure necessary for `libdl.so`. This is
synthesized on-the-fly as a global which is imported into the final
module. The build is additionally updated to wasi-sdk-33

Author: alexcrichton

.github/actions/install-rust/action.yml

@@ -47,23 +47,23 @@ runs:
       shell: bash
 
     - run: |
-        curl -L -o wasi-sdk.tar.gz https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-27/wasi-sdk-27.0-x86_64-linux.tar.gz
+        curl -L -o wasi-sdk.tar.gz https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-33/wasi-sdk-33.0-x86_64-linux.tar.gz
         tar xf wasi-sdk.tar.gz
-        echo "WASI_SDK_PATH=`pwd`/wasi-sdk-27.0-x86_64-linux" >> $GITHUB_ENV
+        echo "WASI_SDK_PATH=`pwd`/wasi-sdk-33.0-x86_64-linux" >> $GITHUB_ENV
       if: runner.os == 'Linux'
       shell: bash
       working-directory: ${{ runner.tool_cache }}
     - run: |
-        curl -L -o wasi-sdk.tar.gz https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-27/wasi-sdk-27.0-x86_64-macos.tar.gz
+        curl -L -o wasi-sdk.tar.gz https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-33/wasi-sdk-33.0-x86_64-macos.tar.gz
         tar xf wasi-sdk.tar.gz
-        echo "WASI_SDK_PATH=`pwd`/wasi-sdk-27.0-x86_64-macos" >> $GITHUB_ENV
+        echo "WASI_SDK_PATH=`pwd`/wasi-sdk-33.0-x86_64-macos" >> $GITHUB_ENV
       if: runner.os == 'macOS'
       shell: bash
       working-directory: ${{ runner.tool_cache }}
     - run: |
-        curl -L -o wasi-sdk.tar.gz https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-27/wasi-sdk-27.0-x86_64-windows.tar.gz
+        curl -L -o wasi-sdk.tar.gz https://github.com/WebAssembly/wasi-sdk/releases/download/wasi-sdk-33/wasi-sdk-33.0-x86_64-windows.tar.gz
         tar xf wasi-sdk.tar.gz
-        echo "WASI_SDK_PATH=`pwd`/wasi-sdk-27.0-x86_64-windows" >> $GITHUB_ENV
+        echo "WASI_SDK_PATH=`pwd`/wasi-sdk-33.0-x86_64-windows" >> $GITHUB_ENV
       if: runner.os == 'Windows'
       shell: bash
       working-directory: ${{ runner.tool_cache }}

.github/workflows/main.yml

@@ -194,7 +194,7 @@ jobs:
         submodules: true
     - uses: ./.github/actions/install-rust
       with:
-        toolchain: 1.89.0
+        toolchain: 1.97.0
     - run: rustup target add wasm32-wasip1
     - run: cd crates/wit-component/dl && bash check.sh
 

crates/wit-component/dl/build.sh

@@ -7,7 +7,12 @@
 
 set -ex
 
-CARGO_PROFILE_RELEASE_LTO=true RUSTFLAGS="-C relocation-model=pic" cargo build --release --target=wasm32-wasip1
-$WASI_SDK_PATH/bin/clang -shared -o $1 -Wl,--whole-archive ../../../target/wasm32-wasip1/release/libdl.a -Wl,--no-whole-archive
+CARGO_PROFILE_RELEASE_LTO=true cargo build --release --target=wasm32-wasip2
+$WASI_SDK_PATH/bin/wasm32-wasip2-clang -shared \
+  -o $1 \
+  -Wl,--whole-archive \
+  ../../../target/wasm32-wasip2/release/libdl.a \
+  -Wl,--no-whole-archive \
+  -Wl,--allow-undefined
 cargo run --manifest-path ../../../Cargo.toml -- strip $1 -o $1
 cargo run --manifest-path ../../../Cargo.toml -- strip --delete name $1 -o $1

crates/wit-component/dl/check.sh

@@ -1,7 +1,7 @@
 set -ex
 
-bash ./build.sh ../../../target/wasm32-wasip1/release/tmp.so
-if diff ../../../target/wasm32-wasip1/release/tmp.so ../libdl.so; then
+bash ./build.sh ../../../target/wasm32-wasip2/release/tmp.so
+if diff ../../../target/wasm32-wasip2/release/tmp.so ../libdl.so; then
   exit 0
 else
   echo "libdl.so is out-of-date; please run crates/wit-component/dl/build.sh to update it">&2

crates/wit-component/dl/src/lib.rs

@@ -48,20 +48,17 @@ pub struct Libraries {
 }
 
 static mut ERROR: *const c_char = ptr::null();
-static mut LIBRARIES: *const Libraries = ptr::null();
+
+unsafe extern "C" {
+    #[link_name = "__wasm_libdl_libraries"]
+    static LIBRARIES: Libraries;
+}
 
 unsafe fn invalid_handle(library: *const c_void) -> bool {
     unsafe {
-        if LIBRARIES.is_null() {
-            panic!(
-                "`__wasm_set_libraries` should have been called during \
-             instantiation with a non-NULL value"
-            );
-        }
-
         let library = library as *const Library;
-        if (0..(*LIBRARIES).count)
-            .any(|index| (*LIBRARIES).libraries.add(usize::try_from(index).unwrap()) == library)
+        if (0..LIBRARIES.count)
+            .any(|index| LIBRARIES.libraries.add(usize::try_from(index).unwrap()) == library)
         {
             false
         } else {
@@ -95,13 +92,6 @@ pub extern "C" fn dlerror() -> *const c_char {
 #[unsafe(no_mangle)]
 pub unsafe extern "C" fn dlopen(name: *const c_char, flags: c_int) -> *const c_void {
     unsafe {
-        if LIBRARIES.is_null() {
-            panic!(
-                "`__wasm_set_libraries` should have been called during \
-             instantiation with a non-NULL value"
-            );
-        }
-
         if (flags & !(RTLD_LAZY | RTLD_NOW | RTLD_GLOBAL)) != 0 {
             // TODO
             ERROR = c"dlopen flags not yet supported".as_ptr();
@@ -111,8 +101,8 @@ pub unsafe extern "C" fn dlopen(name: *const c_char, flags: c_int) -> *const c_v
         let name = CStr::from_ptr(name);
         let name = name.to_bytes();
         let libraries = slice::from_raw_parts(
-            (*LIBRARIES).libraries,
-            usize::try_from((*LIBRARIES).count).unwrap(),
+            LIBRARIES.libraries,
+            usize::try_from(LIBRARIES.count).unwrap(),
         );
         if let Ok(index) = libraries.binary_search_by(|library| {
             slice::from_raw_parts(
@@ -166,17 +156,6 @@ pub unsafe extern "C" fn dlsym(library: *const c_void, name: *const c_char) -> *
     }
 }
 
-/// # Safety
-///
-/// `libraries` must be a valid pointer to a `Libraries` object, and this
-/// pointer must remain valid for the lifetime of the process.
-#[unsafe(no_mangle)]
-pub unsafe extern "C" fn __wasm_set_libraries(libraries: *const Libraries) {
-    unsafe {
-        LIBRARIES = libraries;
-    }
-}
-
 #[cfg(target_arch = "wasm32")]
 #[panic_handler]
 fn panic(_info: &core::panic::PanicInfo) -> ! {

crates/wit-component/libdl.so

@@ -354,25 +354,33 @@ fn make_env_module<'a>(
         exports.export(CABI_REALLOC, ExportKind::Func, index);
     }
 
+    let mut add_global_export = |name: &str, value, mutable| {
+        let index = globals.len();
+        globals.global(
+            wasm_encoder::GlobalType {
+                val_type: ValType::I32,
+                mutable,
+                shared: false,
+            },
+            &const_u32(value),
+        );
+        exports.export(name, ExportKind::Global, index);
+    };
+
     let dl_openables = DlOpenables::new(table_offset, memory_offset, metadata);
 
+    if metadata.iter().any(|m| m.needs_libdl_libraries) {
+        add_global_export(
+            metadata::LIBDL_LIBRARIES,
+            dl_openables.libraries_address,
+            true,
+        );
+    }
+
     table_offset += dl_openables.function_count;
     memory_offset += u32::try_from(dl_openables.buffer.len()).unwrap();
 
     let memory_size = {
-        let mut add_global_export = |name: &str, value, mutable| {
-            let index = globals.len();
-            globals.global(
-                wasm_encoder::GlobalType {
-                    val_type: ValType::I32,
-                    mutable,
-                    shared: false,
-                },
-                &const_u32(value),
-            );
-            exports.export(name, ExportKind::Global, index);
-        };
-
         if metadata.iter().any(|m| m.needs_stack_pointer) {
             add_global_export(metadata::STACK_POINTER, stack_size_bytes, true);
         }
@@ -566,7 +574,6 @@ fn make_init_module(
     types.ty().function([], []);
     let thunk_ty = 0;
     types.ty().function([ValType::I32], []);
-    let one_i32_param_ty = 1;
     let mut type_offset = 2;
 
     for metadata in metadata {
@@ -736,18 +743,6 @@ fn make_init_module(
             )));
         }
 
-        if metadata.has_set_libraries {
-            ctor_calls.push(Ins::I32Const(
-                i32::try_from(dl_openables.libraries_address).unwrap(),
-            ));
-            ctor_calls.push(Ins::Call(add_function_import(
-                &mut imports,
-                metadata.name,
-                metadata::SET_LIBRARIES,
-                one_i32_param_ty,
-            )));
-        }
-
         for import in &metadata.memory_address_imports {
             let (exporter, _) = find_offset_exporter(import, exporters)?;
 
@@ -1756,6 +1751,7 @@ impl Linker {
                         metadata::HEAP_END,
                         metadata::STACK_HIGH,
                         metadata::STACK_LOW,
+                        metadata::LIBDL_LIBRARIES,
                     ]
                     .into_iter()
                     .map(|name| Item {

crates/wit-component/src/linking.rs

@@ -32,7 +32,7 @@ pub const APPLY_DATA_RELOCS: &str = "__wasm_apply_data_relocs";
 pub const CALL_CTORS: &str = "__wasm_call_ctors";
 pub const INITIALIZE: &str = "_initialize";
 pub const START: &str = "_start";
-pub const SET_LIBRARIES: &str = "__wasm_set_libraries";
+pub const LIBDL_LIBRARIES: &str = "__wasm_libdl_libraries";
 pub const INIT_TASK: &str = "__wasm_init_task";
 pub const INIT_ASYNC_TASK: &str = "__wasm_init_async_task";
 
@@ -210,8 +210,8 @@ pub struct Metadata<'a> {
     /// Whether this module exports `_start`
     pub has_wasi_start: bool,
 
-    /// Whether this module exports `__wasm_set_libraries`
-    pub has_set_libraries: bool,
+    /// Whether this module imports `__wasm_libdl_libraries`
+    pub needs_libdl_libraries: bool,
 
     /// Whether this module exports `__wasm_init_task`
     pub has_init_task: bool,
@@ -286,7 +286,7 @@ impl<'a> Metadata<'a> {
             has_ctors: false,
             has_initialize: false,
             has_wasi_start: false,
-            has_set_libraries: false,
+            needs_libdl_libraries: false,
             has_init_task: false,
             has_component_exports,
             is_asyncified: false,
@@ -463,6 +463,10 @@ impl<'a> Metadata<'a> {
                                         self::HEAP_END => result.needs_heap_end = true,
                                         self::STACK_HIGH => result.needs_stack_high = true,
                                         self::STACK_LOW => result.needs_stack_low = true,
+                                        self::LIBDL_LIBRARIES => {
+                                            result.needs_libdl_libraries = true;
+                                        }
+
                                         _ => {
                                             result.memory_address_imports.insert(name);
                                         }
@@ -547,7 +551,6 @@ impl<'a> Metadata<'a> {
                             self::CALL_CTORS => result.has_ctors = true,
                             self::INITIALIZE => result.has_initialize = true,
                             self::START => result.has_wasi_start = true,
-                            self::SET_LIBRARIES => result.has_set_libraries = true,
                             _ => {
                                 if export.name == self::INIT_TASK {
                                     result.has_init_task = true;