Proof of Concept

filetests/call_indirect.wat

@@ -17,7 +17,7 @@
   )
   (func $minus_1 (param i64) (result i64)
     get_local 0
-    i64.const 1
+    i64.const 2
     i64.sub
   )
 

lib/execute/Cargo.toml

@@ -13,3 +13,4 @@ cranelift-wasm = "0.18.1"
 region = "0.3.0"
 wasmtime-environ = { path = "../environ" }
 memmap = "0.6.2"
+nix = "0.11"

lib/execute/src/execute.rs

@@ -9,6 +9,7 @@ use std::ptr::{self, write_unaligned};
 use wasmtime_environ::{
     compile_module, Compilation, Module, ModuleTranslation, Relocation, RelocationTarget,
 };
+use nix::sys::signal::{sigaction, SigAction, SIGILL, SaFlags, SigSet, SigHandler};
 
 /// Executes a module that has been translated with the `wasmtime-environ` environment
 /// implementation.
@@ -149,8 +150,30 @@ pub fn execute(
     // the generated code.Thanks to this, we can transmute the code region into a first-class
     // Rust function and call it.
     unsafe {
-        let start_func = transmute::<_, fn(*const *mut u8)>(code_buf.as_ptr());
-        start_func(vmctx.as_ptr());
+        let sa = SigAction::new(SigHandler::Handler(catch_sigill), SaFlags::empty(), SigSet::empty());
+        sigaction(SIGILL, &sa).unwrap();
+
+        let result = setjmp((&mut setjmp_buffer[..]).as_mut_ptr() as *mut ::nix::libc::c_void);
+        if result == 0 {
+            let start_func = transmute::<_, fn(*const *mut u8)>(code_buf.as_ptr());
+            start_func(vmctx.as_ptr());
+        } else {
+            panic!("error: {}", result);
+        }
     }
     Ok(())
 }
+
+// why 27?
+static mut setjmp_buffer: [::nix::libc::c_int; 27] = [0; 27];
+
+extern "C" {
+	fn setjmp(env: *mut ::nix::libc::c_void) -> ::nix::libc::c_int;
+	fn longjmp(env: *mut ::nix::libc::c_void, val: ::nix::libc::c_int);
+}
+
+extern "C" fn catch_sigill(_: ::nix::libc::c_int) {
+    unsafe {
+        longjmp((&mut setjmp_buffer).as_mut_ptr() as *mut ::nix::libc::c_void, 3);
+    }
+}

lib/execute/src/lib.rs

@@ -17,6 +17,7 @@ extern crate cranelift_wasm;
 extern crate memmap;
 extern crate region;
 extern crate wasmtime_environ;
+extern crate nix;
 
 mod execute;
 mod instance;