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wasm.rs
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wasm.rs
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use std::io::{self, Read, BufReader};
use std::fs::File;
use std::path::{Path};
use failure::{Error, err_msg};
use serde_json::{Value as Json, to_vec, de};
use serde::Serialize;
use wasmi::{self, load_from_buffer, ModuleInstance, ImportsBuilder, ModuleRef};
use wasmi::RuntimeValue::I32;
use wasmi::{MemoryRef};
use wasmi::{Externals, RuntimeValue, RuntimeArgs, ModuleImportResolver};
use wasmi::{FuncRef, ValueType, Signature, FuncInstance};
const PAGE_SIZE: usize = 65536; // for some reason it's not in interpreter
const PANIC_INDEX: usize = 0;
pub(in scheduler) struct Scheduler {
module: ModuleRef,
memory: MemoryRef,
scheduler_util: Util,
}
struct ReadMemory {
memory: MemoryRef,
offset: usize,
}
struct Resolver;
struct Util {
memory: MemoryRef,
}
pub(in scheduler) fn read(dir: &Path)
-> Result<Scheduler, Error>
{
// Here we load module using dedicated for this purpose
// `deserialize_file` function (which works only with modules)
let path = dir.join("scheduler.wasm");
let mut buf = Vec::new();
File::open(&path)
.and_then(|mut f| f.read_to_end(&mut buf))
.map_err(|e| err_msg(format!("Error reading {:?}: {}", path, e)))?;
let module = load_from_buffer(&buf)
.map_err(|e| err_msg(format!("error decoding wasm: {:?}", e)))?;
let module = ModuleInstance::new(
&module,
&ImportsBuilder::new()
.with_resolver("env", &Resolver),
).map_err(|e| err_msg(format!("error adding wasm module: {}", e)))?;
let memory = module.not_started_instance().export_by_name("memory")
.and_then(|x| x.as_memory().map(Clone::clone))
.ok_or_else(|| err_msg("no memory exported"))?;
let mut scheduler_util = Util { memory: memory.clone() };
let module = module.run_start(&mut scheduler_util)
.map_err(|e| err_msg(format!("error starting wasm module: {}", e)))?;
Ok(Scheduler { module, memory, scheduler_util })
}
impl Scheduler {
pub fn execute<S: Serialize>(&mut self, input: &S)
-> (Result<Json, Error>, String)
{
let bytes = match to_vec(input) {
Ok(bytes) => bytes,
Err(e) => return (Err(e.into()),
String::from("failed to encode input")),
};
let off = match
self.module.invoke_export("alloc",
&[I32(bytes.len() as i32)],
&mut self.scheduler_util)
{
Ok(Some(I32(off))) => off as u32,
Ok(x) => return (
Err(err_msg(format!("alloc invalid: {:?}", x))),
String::from("failed to allocate memory")),
Err(e) => return (
Err(err_msg(format!("failed to allocate memory: {}", e))),
String::from("failed to allocate memory")),
};
match self.memory.set(off, &bytes) {
Ok(()) => {},
Err(e) => return (
Err(err_msg(format!("failed to write memory: {}", e))),
String::from("failed to write memory")),
};
let roff = self.module.invoke_export("scheduler",
&[I32(off as i32), I32(bytes.len() as i32)],
&mut self.scheduler_util);
match self.module.invoke_export("dealloc",
&[I32(off as i32)],
&mut self.scheduler_util)
{
Ok(_) => {}
Err(e) => return (
Err(err_msg(format!("failed to deallocate memory: {}", e))),
String::from("failed to deallocate memory")),
};
let roff = match roff {
Ok(Some(I32(off))) => {
let memsize = self.memory.size() * PAGE_SIZE as u32;
if off as u32 >= memsize {
return (
Err(err_msg(format!("scheduler returned offset {} \
but memory size is {}", off, memsize))),
String::from("scheduler result error"))
}
off as u32
}
Ok(x) => return (
Err(err_msg(format!("bad scheduler result: {:?}", x))),
String::from("scheduler result error")),
Err(e) => return (
Err(err_msg(format!("bad scheduler result: {}", e))),
String::from("scheduler result error")),
};
let reader = ReadMemory {
memory: self.memory.clone(),
offset: roff as usize,
};
let de = de::Deserializer::from_reader(BufReader::new(reader));
let (result, debug) = match de.into_iter().next() {
Some(Ok((result, debug))) => (result, debug),
None => return (
Err(err_msg(format!("failed to \
deserialize scheduler result: no value decoded"))),
String::from("deserialize error")),
Some(Err(e)) => return (
Err(err_msg(format!("failed to \
deserialize scheduler result: {}", e))),
String::from("deserialize error")),
};
match self.module.invoke_export("dealloc",
&[I32(roff as i32)], &mut self.scheduler_util)
{
Ok(_) => {}
Err(e) => return (
Err(err_msg(format!("failed to deallocate memory: {}", e))),
String::from("failed to deallocate memory")),
};
(Ok(result), debug)
}
}
impl io::Read for ReadMemory {
fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
let ref mut off = self.offset;
let memsize = self.memory.size() as usize * PAGE_SIZE;
debug_assert!(*off <= memsize);
let dest = if *off + buf.len() > memsize {
buf.split_at_mut(memsize - *off).0
} else {
buf
};
match self.memory.get_into(*off as u32, dest) {
Ok(()) => {
*off += dest.len();
Ok(dest.len())
}
Err(e) => Err(io::Error::new(io::ErrorKind::Other, e.to_string())),
}
}
}
impl ModuleImportResolver for Resolver {
fn resolve_func(&self, field_name: &str, signature: &Signature)
-> Result<FuncRef, wasmi::Error>
{
match field_name {
"log_panic"
if signature == &Signature::new(&[ValueType::I32; 5][..], None)
=> Ok(FuncInstance::alloc_host(signature.clone(), PANIC_INDEX)),
"log_panic" => Err(wasmi::Error::Instantiation(
format!("Export {} expects invalid signature {:?}",
field_name, signature)
)),
_ => Err(wasmi::Error::Instantiation(
format!("Export {} not found", field_name),
))
}
}
}
impl Externals for Util {
fn invoke_index(&mut self, index: usize, args: RuntimeArgs)
-> Result<Option<RuntimeValue>, wasmi::Error>
{
match index {
PANIC_INDEX => {
// panic(payload_str, payload_len, file_ptr, file_len, line);
let payload_ptr: Result<u32, _> = args.nth(0);
let payload_len: Result<u32, _> = args.nth(1);
let file_ptr: Result<u32, _> = args.nth(2);
let file_len: Result<u32, _> = args.nth(3);
let line: Result<u32, _> = args.nth(4);
let payload = match (payload_ptr, payload_len) {
(_, Ok(0)) | (_, Err(_)) | (Err(_), _) => {
"<non-str payload>".into()
}
(Ok(off), Ok(len)) => {
let mut buf = vec![0u8; len as usize];
match self.memory.get_into(off, &mut buf) {
Ok(()) => String::from_utf8_lossy(&buf).to_string(),
Err(e) => {
debug!("Error reading panic payload: {}", e);
"<can't read payload>".into()
}
}
}
};
let filename = match (file_ptr, file_len) {
(_, Ok(0)) | (_, Err(_)) | (Err(_), _) => {
"<unknown file>".into()
}
(Ok(off), Ok(len)) => {
let mut buf = vec![0u8; len as usize];
match self.memory.get_into(off, &mut buf) {
Ok(()) => String::from_utf8_lossy(&buf).to_string(),
Err(e) => {
debug!("Error reading panic filename: {}", e);
"<can't read filename>".into()
}
}
}
};
error!("Scheduler panicked at {:?}:{}: {:?}",
filename, line.unwrap_or(0), payload);
Ok(None)
}
_ => panic!("Unimplemented function at {}", index),
}
}
}