Naive short circuiting implementation for user panics and results. (#167

) * Add panic and result catching * exit process on panic and user runtime error * Complete initial implementation
wasmerio · Feb 8, 2019 · 1886b3d · 1886b3d
1 parent 4e1bc48
commit 1886b3d
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Showing 10 changed files with 172 additions and 61 deletions.
diff --git a/lib/clif-backend/src/module.rs b/lib/clif-backend/src/module.rs
@@ -16,7 +16,7 @@ use wasmer_runtime_core::{
     cache::{Cache, Error as CacheError},
 };
 use wasmer_runtime_core::{
-    backend::{Backend, FuncResolver, ProtectedCaller, Token},
+    backend::{Backend, FuncResolver, ProtectedCaller, Token, UserTrapper},
     error::{CompileResult, RuntimeResult},
     module::{ModuleInfo, ModuleInner, StringTable},
     structures::{Map, TypedIndex},
@@ -51,6 +51,10 @@ impl ProtectedCaller for Placeholder {
     ) -> RuntimeResult<Vec<Value>> {
         Ok(vec![])
     }
+
+    fn get_early_trapper(&self) -> Box<dyn UserTrapper> {
+        unimplemented!()
+    }
 }
 
 /// This contains all of the items in a `ModuleInner` except the `func_resolver`.

diff --git a/lib/clif-backend/src/signal/mod.rs b/lib/clif-backend/src/signal/mod.rs
@@ -2,9 +2,9 @@ use crate::relocation::{TrapData, TrapSink};
 use crate::trampoline::Trampolines;
 use hashbrown::HashSet;
 use libc::c_void;
-use std::sync::Arc;
+use std::{cell::Cell, sync::Arc};
 use wasmer_runtime_core::{
-    backend::{ProtectedCaller, Token},
+    backend::{ProtectedCaller, Token, UserTrapper},
     error::RuntimeResult,
     export::Context,
     module::{ExportIndex, ModuleInfo, ModuleInner},
@@ -24,6 +24,19 @@ pub use self::unix::*;
 #[cfg(windows)]
 pub use self::windows::*;
 
+thread_local! {
+    pub static TRAP_EARLY_DATA: Cell<Option<String>> = Cell::new(None);
+}
+
+pub struct Trapper;
+
+impl UserTrapper for Trapper {
+    unsafe fn do_early_trap(&self, msg: String) -> ! {
+        TRAP_EARLY_DATA.with(|cell| cell.set(Some(msg)));
+        trigger_trap()
+    }
+}
+
 pub struct Caller {
     func_export_set: HashSet<FuncIndex>,
     handler_data: HandlerData,
@@ -118,6 +131,10 @@ impl ProtectedCaller for Caller {
             })
             .collect())
     }
+
+    fn get_early_trapper(&self) -> Box<dyn UserTrapper> {
+        Box::new(Trapper)
+    }
 }
 
 fn get_func_from_index(

diff --git a/lib/clif-backend/src/signal/unix.rs b/lib/clif-backend/src/signal/unix.rs
@@ -9,7 +9,7 @@
 //! are very special, the async signal unsafety of Rust's TLS implementation generally does not affect the correctness here
 //! unless you have memory unsafety elsewhere in your code.
 //!
-use crate::relocation::{TrapCode, TrapData, TrapSink};
+use crate::relocation::{TrapCode, TrapData};
 use crate::signal::HandlerData;
 use libc::{c_int, c_void, siginfo_t};
 use nix::sys::signal::{
@@ -60,6 +60,12 @@ thread_local! {
     pub static CURRENT_EXECUTABLE_BUFFER: Cell<*const c_void> = Cell::new(ptr::null());
 }
 
+pub unsafe fn trigger_trap() -> ! {
+    let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
+
+    longjmp(jmp_buf as *mut c_void, 0)
+}
+
 pub fn call_protected<T>(handler_data: &HandlerData, f: impl FnOnce() -> T) -> RuntimeResult<T> {
     unsafe {
         let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
@@ -72,54 +78,59 @@ pub fn call_protected<T>(handler_data: &HandlerData, f: impl FnOnce() -> T) -> R
         let signum = setjmp(jmp_buf as *mut _);
         if signum != 0 {
             *jmp_buf = prev_jmp_buf;
-            let (faulting_addr, inst_ptr) = CAUGHT_ADDRESSES.with(|cell| cell.get());
-
-            if let Some(TrapData {
-                trapcode,
-                srcloc: _,
-            }) = handler_data.lookup(inst_ptr)
-            {
-                Err(match Signal::from_c_int(signum) {
-                    Ok(SIGILL) => match trapcode {
-                        TrapCode::BadSignature => RuntimeError::IndirectCallSignature {
-                            table: TableIndex::new(0),
-                        },
-                        TrapCode::IndirectCallToNull => RuntimeError::IndirectCallToNull {
-                            table: TableIndex::new(0),
+
+            if let Some(msg) = super::TRAP_EARLY_DATA.with(|cell| cell.replace(None)) {
+                Err(RuntimeError::User { msg })
+            } else {
+                let (faulting_addr, inst_ptr) = CAUGHT_ADDRESSES.with(|cell| cell.get());
+
+                if let Some(TrapData {
+                    trapcode,
+                    srcloc: _,
+                }) = handler_data.lookup(inst_ptr)
+                {
+                    Err(match Signal::from_c_int(signum) {
+                        Ok(SIGILL) => match trapcode {
+                            TrapCode::BadSignature => RuntimeError::IndirectCallSignature {
+                                table: TableIndex::new(0),
+                            },
+                            TrapCode::IndirectCallToNull => RuntimeError::IndirectCallToNull {
+                                table: TableIndex::new(0),
+                            },
+                            TrapCode::HeapOutOfBounds => RuntimeError::OutOfBoundsAccess {
+                                memory: MemoryIndex::new(0),
+                                addr: None,
+                            },
+                            TrapCode::TableOutOfBounds => RuntimeError::TableOutOfBounds {
+                                table: TableIndex::new(0),
+                            },
+                            _ => RuntimeError::Unknown {
+                                msg: "unknown trap".to_string(),
+                            },
                         },
-                        TrapCode::HeapOutOfBounds => RuntimeError::OutOfBoundsAccess {
+                        Ok(SIGSEGV) | Ok(SIGBUS) => RuntimeError::OutOfBoundsAccess {
                             memory: MemoryIndex::new(0),
                             addr: None,
                         },
-                        TrapCode::TableOutOfBounds => RuntimeError::TableOutOfBounds {
-                            table: TableIndex::new(0),
-                        },
-                        _ => RuntimeError::Unknown {
-                            msg: "unknown trap".to_string(),
-                        },
-                    },
-                    Ok(SIGSEGV) | Ok(SIGBUS) => RuntimeError::OutOfBoundsAccess {
-                        memory: MemoryIndex::new(0),
-                        addr: None,
-                    },
-                    Ok(SIGFPE) => RuntimeError::IllegalArithmeticOperation,
-                    _ => unimplemented!(),
-                }
-                .into())
-            } else {
-                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",
-                };
-                // When the trap-handler is fully implemented, this will return more information.
-                Err(RuntimeError::Unknown {
-                    msg: format!("trap at {:p} - {}", faulting_addr, signal),
+                        Ok(SIGFPE) => RuntimeError::IllegalArithmeticOperation,
+                        _ => unimplemented!(),
+                    }
+                    .into())
+                } else {
+                    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",
+                    };
+                    // When the trap-handler is fully implemented, this will return more information.
+                    Err(RuntimeError::Unknown {
+                        msg: format!("trap at {:p} - {}", faulting_addr, signal),
+                    }
+                    .into())
                 }
-                .into())
             }
         } else {
             let ret = f(); // TODO: Switch stack?

diff --git a/lib/runtime-core/src/backend.rs b/lib/runtime-core/src/backend.rs
@@ -82,6 +82,12 @@ pub trait ProtectedCaller: Send + Sync {
         vmctx: *mut vm::Ctx,
         _: Token,
     ) -> RuntimeResult<Vec<Value>>;
+
+    fn get_early_trapper(&self) -> Box<dyn UserTrapper>;
+}
+
+pub trait UserTrapper {
+    unsafe fn do_early_trap(&self, msg: String) -> !;
 }
 
 pub trait FuncResolver: Send + Sync {

diff --git a/lib/runtime-core/src/error.rs b/lib/runtime-core/src/error.rs
@@ -97,6 +97,9 @@ pub enum RuntimeError {
         table: TableIndex,
     },
     IllegalArithmeticOperation,
+    User {
+        msg: String,
+    },
     Unknown {
         msg: String,
     },

diff --git a/lib/runtime-core/src/instance.rs b/lib/runtime-core/src/instance.rs
@@ -7,7 +7,6 @@ use crate::{
     import::{ImportObject, LikeNamespace},
     memory::Memory,
     module::{ExportIndex, Module, ModuleInner},
-    sig_registry::SigRegistry,
     table::Table,
     typed_func::{Func, Safe, WasmTypeList},
     types::{FuncIndex, FuncSig, GlobalIndex, LocalOrImport, MemoryIndex, TableIndex, Value},

diff --git a/lib/runtime-core/src/module.rs b/lib/runtime-core/src/module.rs
@@ -3,6 +3,7 @@ use crate::{
     error::Result,
     import::ImportObject,
     structures::{Map, TypedIndex},
+    typed_func::EARLY_TRAPPER,
     types::{
         FuncIndex, FuncSig, GlobalDescriptor, GlobalIndex, GlobalInit, ImportedFuncIndex,
         ImportedGlobalIndex, ImportedMemoryIndex, ImportedTableIndex, Initializer,
@@ -63,6 +64,10 @@ pub struct Module(#[doc(hidden)] pub Arc<ModuleInner>);
 
 impl Module {
     pub(crate) fn new(inner: Arc<ModuleInner>) -> Self {
+        unsafe {
+            EARLY_TRAPPER
+                .with(|ucell| *ucell.get() = Some(inner.protected_caller.get_early_trapper()));
+        }
         Module(inner)
     }
 

diff --git a/lib/runtime-core/src/typed_func.rs b/lib/runtime-core/src/typed_func.rs
@@ -1,11 +1,16 @@
 use crate::{
+    backend::UserTrapper,
     error::RuntimeError,
     export::{Context, Export, FuncPointer},
     import::IsExport,
     types::{FuncSig, Type, WasmExternType},
     vm::Ctx,
 };
-use std::{marker::PhantomData, mem, ptr, sync::Arc};
+use std::{cell::UnsafeCell, fmt, marker::PhantomData, mem, panic, ptr, sync::Arc};
+
+thread_local! {
+    pub static EARLY_TRAPPER: UnsafeCell<Option<Box<dyn UserTrapper>>> = UnsafeCell::new(None);
+}
 
 pub trait Safeness {}
 pub struct Safe;
@@ -28,9 +33,44 @@ where
     Args: WasmTypeList,
     Rets: WasmTypeList,
 {
-    fn to_raw(self) -> *const ();
+    fn to_raw(&self) -> *const ();
+}
+
+pub trait TrapEarly<Rets>
+where
+    Rets: WasmTypeList,
+{
+    fn report(self) -> Result<Rets, String>;
+}
+
+impl<Rets> TrapEarly<Rets> for Rets
+where
+    Rets: WasmTypeList,
+{
+    fn report(self) -> Result<Rets, String> {
+        Ok(self)
+    }
 }
 
+impl<Rets, E> TrapEarly<Rets> for Result<Rets, E>
+where
+    Rets: WasmTypeList,
+    E: fmt::Debug,
+{
+    fn report(self) -> Result<Rets, String> {
+        self.map_err(|err| format!("Error: {:?}", err))
+    }
+}
+
+// pub fn Func<'a, Args, Rets, F>(f: F) -> Func<'a, Args, Rets, Unsafe>
+// where
+//     Args: WasmTypeList,
+//     Rets: WasmTypeList,
+//     F: ExternalFunction<Args, Rets>
+// {
+//     Func::new(f)
+// }
+
 pub struct Func<'a, Args = (), Rets = (), Safety: Safeness = Safe> {
     f: *const (),
     ctx: *mut Ctx,
@@ -143,18 +183,41 @@ macro_rules! impl_traits {
             }
         }
 
-        impl< $( $x: WasmExternType, )* Rets: WasmTypeList, FN: Fn( $( $x, )* &mut Ctx) -> Rets> ExternalFunction<($( $x ),*), Rets> for FN {
+        impl< $( $x: WasmExternType, )* Rets: WasmTypeList, Trap: TrapEarly<Rets>, FN: Fn( $( $x, )* &mut Ctx) -> Trap> ExternalFunction<($( $x ),*), Rets> for FN {
             #[allow(non_snake_case)]
-            fn to_raw(self) -> *const () {
+            fn to_raw(&self) -> *const () {
                 assert_eq!(mem::size_of::<Self>(), 0, "you cannot use a closure that captures state for `Func`.");
 
-                extern fn wrap<$( $x: WasmExternType, )* Rets: WasmTypeList, FN: Fn( $( $x, )* &mut Ctx) -> Rets>( $( $x: $x, )* ctx: &mut Ctx) -> Rets::CStruct {
+                extern fn wrap<$( $x: WasmExternType, )* Rets: WasmTypeList, Trap: TrapEarly<Rets>, FN: Fn( $( $x, )* &mut Ctx) -> Trap>( $( $x: $x, )* ctx: &mut Ctx) -> Rets::CStruct {
                     let f: FN = unsafe { mem::transmute_copy(&()) };
-                    let rets = f( $( $x, )* ctx);
-                    rets.into_c_struct()
+
+                    let msg = match panic::catch_unwind(panic::AssertUnwindSafe(|| {
+                        f( $( $x, )* ctx).report()
+                    })) {
+                        Ok(Ok(returns)) => return returns.into_c_struct(),
+                        Ok(Err(err)) => err,
+                        Err(err) => {
+                            if let Some(s) = err.downcast_ref::<&str>() {
+                                s.to_string()
+                            } else if let Some(s) = err.downcast_ref::<String>() {
+                                s.clone()
+                            } else {
+                                "a panic occurred, but no additional information is available".to_string()
+                            }
+                        },
+                    };
+
+                    unsafe {
+                        if let Some(early_trapper) = &*EARLY_TRAPPER.with(|ucell| ucell.get()) {
+                            early_trapper.do_early_trap(msg)
+                        } else {
+                            eprintln!("panic handling not setup");
+                            std::process::exit(1)
+                        }
+                    }
                 }
 
-                wrap::<$( $x, )* Rets, Self> as *const ()
+                wrap::<$( $x, )* Rets, Trap, Self> as *const ()
             }
         }
 

diff --git a/lib/runtime-core/src/vm.rs b/lib/runtime-core/src/vm.rs
@@ -493,7 +493,7 @@ mod vm_ctx_tests {
 
     fn generate_module() -> ModuleInner {
         use super::Func;
-        use crate::backend::{Backend, FuncResolver, ProtectedCaller, Token};
+        use crate::backend::{Backend, FuncResolver, ProtectedCaller, Token, UserTrapper};
         use crate::error::RuntimeResult;
         use crate::types::{FuncIndex, LocalFuncIndex, Value};
         use hashbrown::HashMap;
@@ -520,6 +520,9 @@ mod vm_ctx_tests {
             ) -> RuntimeResult<Vec<Value>> {
                 Ok(vec![])
             }
+            fn get_early_trapper(&self) -> Box<dyn UserTrapper> {
+                unimplemented!()
+            }
         }
 
         ModuleInner {