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use crate::prelude::*;
use crate::{
store::StoreOpaque, AsContextMut, FrameInfo, Global, HeapType, Instance, Memory, Module,
StoreContextMut, Val, ValType, WasmBacktrace,
};
use std::{collections::HashMap, fmt};
/// Representation of a core dump of a WebAssembly module
///
/// When the Config::coredump_on_trap option is enabled this structure is
/// attached to the [`anyhow::Error`] returned from many Wasmtime functions that
/// execute WebAssembly such as [`Instance::new`] or [`Func::call`]. This can be
/// acquired with the [`anyhow::Error::downcast`] family of methods to
/// programmatically inspect the coredump. Otherwise since it's part of the
/// error returned this will get printed along with the rest of the error when
/// the error is logged.
///
/// Note that some state, such as Wasm locals or values on the operand stack,
/// may be optimized away by the compiler or otherwise not recovered in the
/// coredump.
///
/// Capturing of wasm coredumps can be configured through the
/// [`Config::coredump_on_trap`][crate::Config::coredump_on_trap] method.
///
/// For more information about errors in wasmtime see the documentation of the
/// [`Trap`][crate::Trap] type.
///
/// [`Func::call`]: crate::Func::call
/// [`Instance::new`]: crate::Instance::new
pub struct WasmCoreDump {
name: String,
modules: Vec<Module>,
instances: Vec<Instance>,
memories: Vec<Memory>,
globals: Vec<Global>,
backtrace: WasmBacktrace,
}
impl WasmCoreDump {
pub(crate) fn new(store: &mut StoreOpaque, backtrace: WasmBacktrace) -> WasmCoreDump {
let modules: Vec<_> = store.modules().all_modules().cloned().collect();
let instances: Vec<Instance> = store.all_instances().collect();
let store_memories: Vec<Memory> = store.all_memories().collect();
let mut store_globals: Vec<Global> = vec![];
store.for_each_global(|_store, global| store_globals.push(global));
WasmCoreDump {
name: String::from("store_name"),
modules,
instances,
memories: store_memories,
globals: store_globals,
backtrace,
}
}
/// The stack frames for this core dump.
///
/// Frames appear in callee to caller order, that is youngest to oldest
/// frames.
pub fn frames(&self) -> &[FrameInfo] {
self.backtrace.frames()
}
/// All modules instantiated inside the store when the core dump was
/// created.
pub fn modules(&self) -> &[Module] {
self.modules.as_ref()
}
/// All instances within the store when the core dump was created.
pub fn instances(&self) -> &[Instance] {
self.instances.as_ref()
}
/// All globals, instance- or host-defined, within the store when the core
/// dump was created.
pub fn globals(&self) -> &[Global] {
self.globals.as_ref()
}
/// All memories, instance- or host-defined, within the store when the core
/// dump was created.
pub fn memories(&self) -> &[Memory] {
self.memories.as_ref()
}
/// Serialize this core dump into [the standard core dump binary
/// format][spec].
///
/// The `name` parameter may be a file path, URL, or arbitrary name for the
/// "main" Wasm service or executable that was running in this store.
///
/// Once serialized, you can write this core dump to disk, send it over the
/// network, or pass it to other debugging tools that consume Wasm core
/// dumps.
///
/// [spec]: https://github.com/WebAssembly/tool-conventions/blob/main/Coredump.md
pub fn serialize(&self, mut store: impl AsContextMut, name: &str) -> Vec<u8> {
let store = store.as_context_mut();
self._serialize(store, name)
}
fn _serialize<T>(&self, mut store: StoreContextMut<'_, T>, name: &str) -> Vec<u8> {
let mut core_dump = wasm_encoder::Module::new();
core_dump.section(&wasm_encoder::CoreDumpSection::new(name));
// A map from each memory to its index in the core dump's memories
// section.
let mut memory_to_idx = HashMap::new();
let mut data = wasm_encoder::DataSection::new();
{
let mut memories = wasm_encoder::MemorySection::new();
for mem in self.memories() {
let memory_idx = memories.len();
memory_to_idx.insert(mem.hash_key(&store.0), memory_idx);
let ty = mem.ty(&store);
memories.memory(wasm_encoder::MemoryType {
minimum: mem.size(&store),
maximum: ty.maximum(),
memory64: ty.is_64(),
shared: ty.is_shared(),
page_size_log2: None,
});
// Attach the memory data, balancing number of data segments and
// binary size. We don't want to attach the whole memory in one
// big segment, since it likely contains a bunch of large runs
// of zeroes. But we can't encode the data without any potential
// runs of zeroes (i.e. including only non-zero data in our
// segments) because we can run up against the implementation
// limits for number of segments in a Wasm module this way. So
// to balance these conflicting desires, we break the memory up
// into reasonably-sized chunks and then trim runs of zeroes
// from the start and end of each chunk.
const CHUNK_SIZE: u32 = 4096;
for (i, chunk) in mem
.data(&store)
.chunks_exact(CHUNK_SIZE as usize)
.enumerate()
{
if let Some(start) = chunk.iter().position(|byte| *byte != 0) {
let end = chunk.iter().rposition(|byte| *byte != 0).unwrap() + 1;
let offset = (i as u32) * CHUNK_SIZE + (start as u32);
let offset = wasm_encoder::ConstExpr::i32_const(offset as i32);
data.active(memory_idx, &offset, chunk[start..end].iter().copied());
}
}
}
core_dump.section(&memories);
}
// A map from each global to its index in the core dump's globals
// section.
let mut global_to_idx = HashMap::new();
{
let mut globals = wasm_encoder::GlobalSection::new();
for g in self.globals() {
global_to_idx.insert(g.hash_key(&store.0), globals.len());
let ty = g.ty(&store);
let mutable = matches!(ty.mutability(), crate::Mutability::Var);
let val_type = match ty.content() {
ValType::I32 => wasm_encoder::ValType::I32,
ValType::I64 => wasm_encoder::ValType::I64,
ValType::F32 => wasm_encoder::ValType::F32,
ValType::F64 => wasm_encoder::ValType::F64,
ValType::V128 => wasm_encoder::ValType::V128,
// We encode all references as null in the core dump, so
// choose the common super type of all the actual function
// reference types. This lets us avoid needing to figure out
// what a concrete type reference's index is in the local
// core dump index space.
ValType::Ref(r) => match r.heap_type().top() {
HeapType::Extern => wasm_encoder::ValType::EXTERNREF,
HeapType::Func => wasm_encoder::ValType::FUNCREF,
HeapType::Any => wasm_encoder::ValType::Ref(wasm_encoder::RefType::ANYREF),
ty => unreachable!("not a top type: {ty:?}"),
},
};
let init = match g.get(&mut store) {
Val::I32(x) => wasm_encoder::ConstExpr::i32_const(x),
Val::I64(x) => wasm_encoder::ConstExpr::i64_const(x),
Val::F32(x) => {
wasm_encoder::ConstExpr::f32_const(unsafe { std::mem::transmute(x) })
}
Val::F64(x) => {
wasm_encoder::ConstExpr::f64_const(unsafe { std::mem::transmute(x) })
}
Val::V128(x) => wasm_encoder::ConstExpr::v128_const(x.as_u128() as i128),
Val::FuncRef(_) => {
wasm_encoder::ConstExpr::ref_null(wasm_encoder::HeapType::FUNC)
}
Val::ExternRef(_) => {
wasm_encoder::ConstExpr::ref_null(wasm_encoder::HeapType::EXTERN)
}
Val::AnyRef(_) => {
wasm_encoder::ConstExpr::ref_null(wasm_encoder::HeapType::ANY)
}
};
globals.global(
wasm_encoder::GlobalType {
val_type,
mutable,
shared: false,
},
&init,
);
}
core_dump.section(&globals);
}
core_dump.section(&data);
drop(data);
// A map from module id to its index within the core dump's modules
// section.
let mut module_to_index = HashMap::new();
{
let mut modules = wasm_encoder::CoreDumpModulesSection::new();
for module in self.modules() {
module_to_index.insert(module.id(), modules.len());
match module.name() {
Some(name) => modules.module(name),
None => modules.module(&format!("<anonymous-module-{}>", modules.len())),
};
}
core_dump.section(&modules);
}
// TODO: We can't currently recover instances from stack frames. We can
// recover module via the frame's PC, but if there are multiple
// instances of the same module, we don't know which instance the frame
// is associated with. Therefore, we do a best effort job: remember the
// last instance of each module and always choose that one. We record
// that information here.
let mut module_to_instance = HashMap::new();
{
let mut instances = wasm_encoder::CoreDumpInstancesSection::new();
for instance in self.instances() {
let module = instance.module(&store);
module_to_instance.insert(module.id(), instances.len());
let module_index = module_to_index[&module.id()];
let memories = instance
.all_memories(&mut store.0)
.collect::<Vec<_>>()
.into_iter()
.map(|(_i, memory)| memory_to_idx[&memory.hash_key(&store.0)])
.collect::<Vec<_>>();
let globals = instance
.all_globals(&mut store.0)
.collect::<Vec<_>>()
.into_iter()
.map(|(_i, global)| global_to_idx[&global.hash_key(&store.0)])
.collect::<Vec<_>>();
instances.instance(module_index, memories, globals);
}
core_dump.section(&instances);
}
{
let thread_name = "main";
let mut stack = wasm_encoder::CoreDumpStackSection::new(thread_name);
for frame in self.frames() {
// This isn't necessarily the right instance if there are
// multiple instances of the same module. See comment above
// `module_to_instance` for details.
let instance = module_to_instance[&frame.module().id()];
let func = frame.func_index();
let offset = frame
.func_offset()
.and_then(|o| u32::try_from(o).ok())
.unwrap_or(0);
// We can't currently recover locals and the operand stack. We
// should eventually be able to do that with Winch though.
let locals = [];
let operand_stack = [];
stack.frame(instance, func, offset, locals, operand_stack);
}
core_dump.section(&stack);
}
core_dump.finish()
}
}
impl fmt::Display for WasmCoreDump {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
writeln!(f, "wasm coredump generated while executing {}:", self.name)?;
writeln!(f, "modules:")?;
for module in self.modules.iter() {
writeln!(f, " {}", module.name().unwrap_or("<module>"))?;
}
writeln!(f, "instances:")?;
for instance in self.instances.iter() {
writeln!(f, " {instance:?}")?;
}
writeln!(f, "memories:")?;
for memory in self.memories.iter() {
writeln!(f, " {memory:?}")?;
}
writeln!(f, "globals:")?;
for global in self.globals.iter() {
writeln!(f, " {global:?}")?;
}
writeln!(f, "backtrace:")?;
write!(f, "{}", self.backtrace)?;
Ok(())
}
}
impl fmt::Debug for WasmCoreDump {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "<wasm core dump>")
}
}