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https://github.com/fluencelabs/wasmer
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Recover safely from WebAssembly-generated traps
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parent
4015fb6193
commit
227a3ee6d6
@ -28,6 +28,7 @@ use structopt::StructOpt;
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mod macros;
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pub mod apis;
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pub mod common;
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mod recovery;
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pub mod sighandler;
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#[cfg(test)]
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mod spectests;
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@ -95,9 +96,7 @@ fn execute_wasm(wasm_path: PathBuf) -> Result<(), String> {
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Some(&webassembly::Export::Function(index)) => index,
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_ => panic!("Main function not found"),
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});
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let main: extern "C" fn(&webassembly::Instance) =
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get_instance_function!(instance, func_index);
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main(&instance);
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instance.start_func(func_index).unwrap();
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}
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Ok(())
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41
src/recovery.rs
Normal file
41
src/recovery.rs
Normal file
@ -0,0 +1,41 @@
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//! When a WebAssembly module triggers any traps, we perform recovery here.
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use std::cell::UnsafeCell;
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extern "C" {
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fn setjmp(env: *mut ::nix::libc::c_void) -> ::nix::libc::c_int;
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fn longjmp(env: *mut ::nix::libc::c_void, val: ::nix::libc::c_int) -> !;
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}
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const SETJMP_BUFFER_LEN: usize = 27;
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thread_local! {
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static SETJMP_BUFFER: UnsafeCell<[::nix::libc::c_int; SETJMP_BUFFER_LEN]> = UnsafeCell::new([0; SETJMP_BUFFER_LEN]);
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}
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/// Calls a function with longjmp receiver installed. The function must be compiled from WebAssembly;
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/// Otherwise, the behavior is undefined.
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pub unsafe fn protected_call<T, R>(f: fn(T) -> R, p: T) -> Result<R, i32> {
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let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
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let prev_jmp_buf = *jmp_buf;
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let signum = setjmp(jmp_buf as *mut ::nix::libc::c_void);
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if signum != 0 {
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*jmp_buf = prev_jmp_buf;
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Err(signum)
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} else {
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let ret = f(p);
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*jmp_buf = prev_jmp_buf;
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Ok(ret)
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}
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}
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/// Unwinds to last protected_call.
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pub unsafe fn do_unwind(signum: i32) -> ! {
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let jmp_buf = SETJMP_BUFFER.with(|buf| buf.get());
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if *jmp_buf == [0; SETJMP_BUFFER_LEN] {
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::std::process::abort();
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}
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longjmp(jmp_buf as *mut ::nix::libc::c_void, signum)
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}
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@ -4,12 +4,11 @@
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//!
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//! Please read more about this here: https://github.com/CraneStation/wasmtime/issues/15
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//! This code is inspired by: https://github.com/pepyakin/wasmtime/commit/625a2b6c0815b21996e111da51b9664feb174622
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use super::recovery;
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use nix::sys::signal::{
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sigaction, SaFlags, SigAction, SigHandler, SigSet, Signal, SIGBUS, SIGFPE, SIGILL, SIGSEGV,
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sigaction, SaFlags, SigAction, SigHandler, SigSet, SIGBUS, SIGFPE, SIGILL, SIGSEGV,
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};
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static mut SETJMP_BUFFER: [::nix::libc::c_int; 27] = [0; 27];
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pub unsafe fn install_sighandler() {
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let sa = SigAction::new(
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SigHandler::Handler(signal_trap_handler),
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@ -20,29 +19,10 @@ pub unsafe fn install_sighandler() {
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sigaction(SIGILL, &sa).unwrap();
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sigaction(SIGSEGV, &sa).unwrap();
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sigaction(SIGBUS, &sa).unwrap();
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let signum = setjmp((&mut SETJMP_BUFFER[..]).as_mut_ptr() as *mut ::nix::libc::c_void);
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if signum != 0 {
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let signal = Signal::from_c_int(signum).unwrap();
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match signal {
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SIGFPE => panic!("floating-point exception"),
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SIGILL => panic!("illegal instruction"),
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SIGSEGV => panic!("segmentation violation"),
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SIGBUS => panic!("bus error"),
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_ => panic!("signal error: {:?}", signal),
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};
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}
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}
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extern "C" {
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fn setjmp(env: *mut ::nix::libc::c_void) -> ::nix::libc::c_int;
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fn longjmp(env: *mut ::nix::libc::c_void, val: ::nix::libc::c_int);
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}
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extern "C" fn signal_trap_handler(signum: ::nix::libc::c_int) {
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unsafe {
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longjmp(
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(&mut SETJMP_BUFFER).as_mut_ptr() as *mut ::nix::libc::c_void,
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signum,
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);
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recovery::do_unwind(signum);
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}
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}
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@ -22,6 +22,7 @@ use std::slice;
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use std::sync::Arc;
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use super::super::common::slice::{BoundedSlice, UncheckedSlice};
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use super::super::recovery;
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use super::errors::ErrorKind;
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use super::import_object::{ImportObject, ImportValue};
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use super::math_intrinsics;
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@ -225,7 +226,8 @@ impl Instance {
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// let r = *Arc::from_raw(isa_ptr);
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compile_function(&*options.isa, function_body).unwrap()
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// unimplemented!()
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}).collect();
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})
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.collect();
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for compiled_func in compiled_funcs.into_iter() {
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let CompiledFunction {
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@ -475,7 +477,8 @@ impl Instance {
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&mem[..],
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mem.current as usize * LinearMemory::WASM_PAGE_SIZE,
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)
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}).collect();
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})
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.collect();
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let globals_pointer: GlobalsSlice = globals[..].into();
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let data_pointers = DataPointers {
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@ -513,10 +516,16 @@ impl Instance {
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get_function_addr(&func_index, &self.import_functions, &self.functions)
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}
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pub fn start(&self) {
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if let Some(func_index) = self.start_func {
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pub fn start_func(&self, func_index: FuncIndex) -> Result<(), i32> {
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let func: fn(&Instance) = get_instance_function!(&self, func_index);
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func(self)
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unsafe { recovery::protected_call(func, self) }
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}
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pub fn start(&self) -> Result<(), i32> {
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if let Some(func_index) = self.start_func {
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self.start_func(func_index)
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} else {
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panic!("start func not found")
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}
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}
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