Improved trap catching with call_protected macro

src/macros.rs

@@ -4,12 +4,7 @@
 #[macro_export]
 macro_rules! get_instance_function {
     ($instance:expr, $func_index:expr) => {{
-        use crate::sighandler::install_sighandler;
         use std::mem;
-
-        unsafe {
-            install_sighandler();
-        };
         let func_addr = $instance.get_function_pointer($func_index);
         unsafe { mem::transmute(func_addr) }
     }};

src/main.rs

@@ -25,9 +25,10 @@ use structopt::StructOpt;
 
 #[macro_use]
 mod macros;
+#[macro_use]
+mod recovery;
 pub mod apis;
 pub mod common;
-mod recovery;
 pub mod sighandler;
 #[cfg(test)]
 mod spectests;
@@ -86,7 +87,7 @@ fn execute_wasm(wasm_path: PathBuf) -> Result<(), String> {
         };
         let main: extern "C" fn(u32, u32, &webassembly::Instance) =
             get_instance_function!(instance, func_index);
-        main(0, 0, &instance);
+        return call_protected!(main(0, 0, &instance)).map_err(|err| format!("{}", err));
     } else {
         let func_index =
             instance
@@ -95,10 +96,10 @@ fn execute_wasm(wasm_path: PathBuf) -> Result<(), String> {
                     Some(&webassembly::Export::Function(index)) => index,
                     _ => panic!("Main function not found"),
                 });
-        instance.start_func(func_index).unwrap();
+        let main: extern "C" fn(&webassembly::Instance) =
+            get_instance_function!(instance, func_index);
+        return call_protected!(main(&instance)).map_err(|err| format!("{}", err));
     }
-
-    Ok(())
 }
 
 fn run(options: Run) {

src/recovery.rs

@@ -5,35 +5,63 @@
 //! unless you have memory unsafety elsewhere in your code.
 
 use std::cell::UnsafeCell;
+use nix::sys::signal::{Signal, SIGFPE, SIGILL, SIGSEGV, SIGBUS};
+use super::webassembly::ErrorKind;
+use super::sighandler::install_sighandler;
 
 extern "C" {
-    fn setjmp(env: *mut ::nix::libc::c_void) -> ::nix::libc::c_int;
+    pub 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) -> !;
 }
 
 const SETJMP_BUFFER_LEN: usize = 27;
 
 thread_local! {
-    static SETJMP_BUFFER: UnsafeCell<[::nix::libc::c_int; SETJMP_BUFFER_LEN]> = UnsafeCell::new([0; SETJMP_BUFFER_LEN]);
+    pub static SETJMP_BUFFER: UnsafeCell<[::nix::libc::c_int; SETJMP_BUFFER_LEN]> = UnsafeCell::new([0; SETJMP_BUFFER_LEN]);
 }
 
+// We need a macro since the arguments we will provide to the funciton
+// (and the return value) are not fixed to just one case: f(x) -> y
+// but multiple: f(x) -> y, f(a,b) -> c, ...
+// And right now it's impossible to handle with Rust function type system
+
 /// Calls a WebAssembly function with longjmp receiver installed. If a non-WebAssembly function is passed in,
-/// the behavior of protected_call is undefined.
-pub unsafe fn protected_call<T, R>(f: fn(T) -> R, p: T) -> Result<R, i32> {
-    let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
-    let prev_jmp_buf = *jmp_buf;
+/// the behavior of call_protected is undefined.
+#[macro_export]
+macro_rules! call_protected {
+    ($x:expr) => {unsafe {
+        use crate::webassembly::ErrorKind;
+        use crate::recovery::{SETJMP_BUFFER, setjmp};
+        use crate::sighandler::install_sighandler;
 
-    let signum = setjmp(jmp_buf as *mut ::nix::libc::c_void);
-    if signum != 0 {
-        *jmp_buf = prev_jmp_buf;
-        Err(signum)
-    } else {
-        let ret = f(p); // TODO: Switch stack?
-        *jmp_buf = prev_jmp_buf;
-        Ok(ret)
-    }
+        use nix::sys::signal::{Signal, SIGFPE, SIGILL, SIGSEGV, SIGBUS};
+
+        let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
+        let prev_jmp_buf = *jmp_buf;
+
+        install_sighandler();
+
+        let signum = setjmp(jmp_buf as *mut ::nix::libc::c_void);
+        if signum != 0 {
+            *jmp_buf = prev_jmp_buf;
+            let signal = match Signal::from_c_int(signum) {
+                Ok(SIGFPE) => "floating-point exception",
+                Ok(SIGILL) => "illegal instruction",
+                Ok(SIGSEGV) => "segmentation violation",
+                Ok(SIGBUS) => "bus error",
+                Err(_) => "error while getting the Signal",
+                _ => "unkown trapped signal",
+            };
+            Err(ErrorKind::RuntimeError(format!("trap - {}", signal)))
+        } else {
+            let ret = $x; // TODO: Switch stack?
+            *jmp_buf = prev_jmp_buf;
+            Ok(ret)
+        }
+    }}
 }
 
+
 /// Unwinds to last protected_call.
 pub unsafe fn do_unwind(signum: i32) -> ! {
     // Since do_unwind is only expected to get called from WebAssembly code which doesn't hold any host resources (locks etc.)

src/webassembly/instance.rs

@@ -519,16 +519,13 @@ impl Instance {
         get_function_addr(&func_index, &self.import_functions, &self.functions)
     }
 
-    pub fn start_func(&self, func_index: FuncIndex) -> Result<(), i32> {
-        let func: fn(&Instance) = get_instance_function!(&self, func_index);
-        unsafe { recovery::protected_call(func, self) }
-    }
-
-    pub fn start(&self) -> Result<(), i32> {
+    pub fn start(&self) -> Result<(), ErrorKind> {
         if let Some(func_index) = self.start_func {
-            self.start_func(func_index)
-        } else {
-            panic!("start func not found")
+            let func: fn(&Instance) = get_instance_function!(&self, func_index);
+            call_protected!(func(self))
+        }
+        else {
+            Ok(())
         }
     }