c9a0ba81a0
* Implement interrupting wasm code, reimplement stack overflow This commit is a relatively large change for wasmtime with two main goals: * Primarily this enables interrupting executing wasm code with a trap, preventing infinite loops in wasm code. Note that resumption of the wasm code is not a goal of this commit. * Additionally this commit reimplements how we handle stack overflow to ensure that host functions always have a reasonable amount of stack to run on. This fixes an issue where we might longjmp out of a host function, skipping destructors. Lots of various odds and ends end up falling out in this commit once the two goals above were implemented. The strategy for implementing this was also lifted from Spidermonkey and existing functionality inside of Cranelift. I've tried to write up thorough documentation of how this all works in `crates/environ/src/cranelift.rs` where gnarly-ish bits are. A brief summary of how this works is that each function and each loop header now checks to see if they're interrupted. Interrupts and the stack overflow check are actually folded into one now, where function headers check to see if they've run out of stack and the sentinel value used to indicate an interrupt, checked in loop headers, tricks functions into thinking they're out of stack. An interrupt is basically just writing a value to a location which is read by JIT code. When interrupts are delivered and what triggers them has been left up to embedders of the `wasmtime` crate. The `wasmtime::Store` type has a method to acquire an `InterruptHandle`, where `InterruptHandle` is a `Send` and `Sync` type which can travel to other threads (or perhaps even a signal handler) to get notified from. It's intended that this provides a good degree of flexibility when interrupting wasm code. Note though that this does have a large caveat where interrupts don't work when you're interrupting host code, so if you've got a host import blocking for a long time an interrupt won't actually be received until the wasm starts running again. Some fallout included from this change is: * Unix signal handlers are no longer registered with `SA_ONSTACK`. Instead they run on the native stack the thread was already using. This is possible since stack overflow isn't handled by hitting the guard page, but rather it's explicitly checked for in wasm now. Native stack overflow will continue to abort the process as usual. * Unix sigaltstack management is now no longer necessary since we don't use it any more. * Windows no longer has any need to reset guard pages since we no longer try to recover from faults on guard pages. * On all targets probestack intrinsics are disabled since we use a different mechanism for catching stack overflow. * The C API has been updated with interrupts handles. An example has also been added which shows off how to interrupt a module. Closes #139 Closes #860 Closes #900 * Update comment about magical interrupt value * Store stack limit as a global value, not a closure * Run rustfmt * Handle review comments * Add a comment about SA_ONSTACK * Use `usize` for type of `INTERRUPTED` * Parse human-readable durations * Bring back sigaltstack handling Allows libstd to print out stack overflow on failure still. * Add parsing and emission of stack limit-via-preamble * Fix new example for new apis * Fix host segfault test in release mode * Fix new doc example
617 lines
20 KiB
Rust
617 lines
20 KiB
Rust
//! Offsets and sizes of various structs in wasmtime-runtime's vmcontext
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//! module.
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// Currently the `VMContext` allocation by field looks like this:
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//
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// struct VMContext {
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// interrupts: *const VMInterrupts,
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// signature_ids: [VMSharedSignatureIndex; module.num_signature_ids],
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// imported_functions: [VMFunctionImport; module.num_imported_functions],
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// imported_tables: [VMTableImport; module.num_imported_tables],
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// imported_memories: [VMMemoryImport; module.num_imported_memories],
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// imported_globals: [VMGlobalImport; module.num_imported_globals],
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// tables: [VMTableDefinition; module.num_defined_tables],
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// memories: [VMMemoryDefinition; module.num_defined_memories],
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// globals: [VMGlobalDefinition; module.num_defined_globals],
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// builtins: VMBuiltinFunctionsArray,
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// }
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use crate::module::ModuleLocal;
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use crate::BuiltinFunctionIndex;
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use cranelift_codegen::ir;
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use cranelift_wasm::{
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DefinedGlobalIndex, DefinedMemoryIndex, DefinedTableIndex, FuncIndex, GlobalIndex, MemoryIndex,
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SignatureIndex, TableIndex,
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};
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use more_asserts::assert_lt;
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use std::convert::TryFrom;
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/// Sentinel value indicating that wasm has been interrupted.
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// Note that this has a bit of an odd definition. See the `insert_stack_check`
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// function in `cranelift/codegen/src/isa/x86/abi.rs` for more information
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pub const INTERRUPTED: usize = usize::max_value() - 32 * 1024;
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#[cfg(target_pointer_width = "32")]
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fn cast_to_u32(sz: usize) -> u32 {
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u32::try_from(sz).unwrap()
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}
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#[cfg(target_pointer_width = "64")]
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fn cast_to_u32(sz: usize) -> u32 {
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u32::try_from(sz).expect("overflow in cast from usize to u32")
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}
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/// Align an offset used in this module to a specific byte-width by rounding up
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fn align(offset: u32, width: u32) -> u32 {
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(offset + (width - 1)) / width * width
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}
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/// This class computes offsets to fields within `VMContext` and other
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/// related structs that JIT code accesses directly.
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pub struct VMOffsets {
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/// The size in bytes of a pointer on the target.
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pub pointer_size: u8,
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/// The number of signature declarations in the module.
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pub num_signature_ids: u32,
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/// The number of imported functions in the module.
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pub num_imported_functions: u32,
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/// The number of imported tables in the module.
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pub num_imported_tables: u32,
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/// The number of imported memories in the module.
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pub num_imported_memories: u32,
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/// The number of imported globals in the module.
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pub num_imported_globals: u32,
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/// The number of defined tables in the module.
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pub num_defined_tables: u32,
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/// The number of defined memories in the module.
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pub num_defined_memories: u32,
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/// The number of defined globals in the module.
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pub num_defined_globals: u32,
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}
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impl VMOffsets {
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/// Return a new `VMOffsets` instance, for a given pointer size.
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pub fn new(pointer_size: u8, module: &ModuleLocal) -> Self {
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Self {
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pointer_size,
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num_signature_ids: cast_to_u32(module.signatures.len()),
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num_imported_functions: cast_to_u32(module.num_imported_funcs),
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num_imported_tables: cast_to_u32(module.num_imported_tables),
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num_imported_memories: cast_to_u32(module.num_imported_memories),
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num_imported_globals: cast_to_u32(module.num_imported_globals),
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num_defined_tables: cast_to_u32(module.table_plans.len()),
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num_defined_memories: cast_to_u32(module.memory_plans.len()),
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num_defined_globals: cast_to_u32(module.globals.len()),
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}
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}
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}
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/// Offsets for `VMFunctionImport`.
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impl VMOffsets {
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/// The offset of the `body` field.
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#[allow(clippy::erasing_op)]
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pub fn vmfunction_import_body(&self) -> u8 {
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0 * self.pointer_size
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}
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/// The offset of the `vmctx` field.
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#[allow(clippy::identity_op)]
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pub fn vmfunction_import_vmctx(&self) -> u8 {
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1 * self.pointer_size
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}
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/// Return the size of `VMFunctionImport`.
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pub fn size_of_vmfunction_import(&self) -> u8 {
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2 * self.pointer_size
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}
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}
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/// Offsets for `*const VMFunctionBody`.
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impl VMOffsets {
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/// The size of the `current_elements` field.
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#[allow(clippy::identity_op)]
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pub fn size_of_vmfunction_body_ptr(&self) -> u8 {
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1 * self.pointer_size
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}
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}
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/// Offsets for `VMTableImport`.
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impl VMOffsets {
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/// The offset of the `from` field.
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#[allow(clippy::erasing_op)]
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pub fn vmtable_import_from(&self) -> u8 {
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0 * self.pointer_size
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}
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/// The offset of the `vmctx` field.
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#[allow(clippy::identity_op)]
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pub fn vmtable_import_vmctx(&self) -> u8 {
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1 * self.pointer_size
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}
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/// Return the size of `VMTableImport`.
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pub fn size_of_vmtable_import(&self) -> u8 {
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2 * self.pointer_size
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}
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}
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/// Offsets for `VMTableDefinition`.
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impl VMOffsets {
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/// The offset of the `base` field.
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#[allow(clippy::erasing_op)]
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pub fn vmtable_definition_base(&self) -> u8 {
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0 * self.pointer_size
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}
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/// The offset of the `current_elements` field.
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#[allow(clippy::identity_op)]
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pub fn vmtable_definition_current_elements(&self) -> u8 {
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1 * self.pointer_size
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}
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/// The size of the `current_elements` field.
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pub fn size_of_vmtable_definition_current_elements(&self) -> u8 {
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4
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}
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/// Return the size of `VMTableDefinition`.
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pub fn size_of_vmtable_definition(&self) -> u8 {
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2 * self.pointer_size
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}
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/// The type of the `current_elements` field.
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pub fn type_of_vmtable_definition_current_elements(&self) -> ir::Type {
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ir::Type::int(u16::from(self.size_of_vmtable_definition_current_elements()) * 8).unwrap()
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}
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}
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/// Offsets for `VMMemoryImport`.
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impl VMOffsets {
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/// The offset of the `from` field.
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#[allow(clippy::erasing_op)]
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pub fn vmmemory_import_from(&self) -> u8 {
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0 * self.pointer_size
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}
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/// The offset of the `vmctx` field.
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#[allow(clippy::identity_op)]
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pub fn vmmemory_import_vmctx(&self) -> u8 {
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1 * self.pointer_size
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}
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/// Return the size of `VMMemoryImport`.
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pub fn size_of_vmmemory_import(&self) -> u8 {
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2 * self.pointer_size
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}
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}
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/// Offsets for `VMMemoryDefinition`.
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impl VMOffsets {
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/// The offset of the `base` field.
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#[allow(clippy::erasing_op)]
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pub fn vmmemory_definition_base(&self) -> u8 {
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0 * self.pointer_size
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}
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/// The offset of the `current_length` field.
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#[allow(clippy::identity_op)]
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pub fn vmmemory_definition_current_length(&self) -> u8 {
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1 * self.pointer_size
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}
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/// The size of the `current_length` field.
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pub fn size_of_vmmemory_definition_current_length(&self) -> u8 {
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4
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}
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/// Return the size of `VMMemoryDefinition`.
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pub fn size_of_vmmemory_definition(&self) -> u8 {
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2 * self.pointer_size
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}
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/// The type of the `current_length` field.
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pub fn type_of_vmmemory_definition_current_length(&self) -> ir::Type {
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ir::Type::int(u16::from(self.size_of_vmmemory_definition_current_length()) * 8).unwrap()
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}
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}
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/// Offsets for `VMGlobalImport`.
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impl VMOffsets {
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/// The offset of the `from` field.
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#[allow(clippy::erasing_op)]
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pub fn vmglobal_import_from(&self) -> u8 {
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0 * self.pointer_size
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}
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/// Return the size of `VMGlobalImport`.
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#[allow(clippy::identity_op)]
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pub fn size_of_vmglobal_import(&self) -> u8 {
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1 * self.pointer_size
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}
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}
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/// Offsets for `VMGlobalDefinition`.
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impl VMOffsets {
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/// Return the size of `VMGlobalDefinition`; this is the size of the largest value type (i.e. a
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/// V128).
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pub fn size_of_vmglobal_definition(&self) -> u8 {
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16
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}
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}
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/// Offsets for `VMSharedSignatureIndex`.
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impl VMOffsets {
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/// Return the size of `VMSharedSignatureIndex`.
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pub fn size_of_vmshared_signature_index(&self) -> u8 {
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4
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}
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}
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/// Offsets for `VMInterrupts`.
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impl VMOffsets {
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/// Return the offset of the `stack_limit` field of `VMInterrupts`
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pub fn vminterrupts_stack_limit(&self) -> u8 {
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0
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}
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}
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/// Offsets for `VMCallerCheckedAnyfunc`.
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impl VMOffsets {
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/// The offset of the `func_ptr` field.
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#[allow(clippy::erasing_op)]
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pub fn vmcaller_checked_anyfunc_func_ptr(&self) -> u8 {
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0 * self.pointer_size
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}
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/// The offset of the `type_index` field.
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#[allow(clippy::identity_op)]
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pub fn vmcaller_checked_anyfunc_type_index(&self) -> u8 {
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1 * self.pointer_size
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}
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/// The offset of the `vmctx` field.
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pub fn vmcaller_checked_anyfunc_vmctx(&self) -> u8 {
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2 * self.pointer_size
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}
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/// Return the size of `VMCallerCheckedAnyfunc`.
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pub fn size_of_vmcaller_checked_anyfunc(&self) -> u8 {
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3 * self.pointer_size
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}
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}
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/// Offsets for `VMContext`.
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impl VMOffsets {
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/// Return the offset to the `VMInterrupts` structure
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pub fn vmctx_interrupts(&self) -> u32 {
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0
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}
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/// The offset of the `signature_ids` array.
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pub fn vmctx_signature_ids_begin(&self) -> u32 {
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self.vmctx_interrupts()
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.checked_add(u32::from(self.pointer_size))
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.unwrap()
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}
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/// The offset of the `tables` array.
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#[allow(clippy::erasing_op)]
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pub fn vmctx_imported_functions_begin(&self) -> u32 {
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self.vmctx_signature_ids_begin()
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.checked_add(
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self.num_signature_ids
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.checked_mul(u32::from(self.size_of_vmshared_signature_index()))
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.unwrap(),
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)
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.unwrap()
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}
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/// The offset of the `tables` array.
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#[allow(clippy::identity_op)]
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pub fn vmctx_imported_tables_begin(&self) -> u32 {
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self.vmctx_imported_functions_begin()
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.checked_add(
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self.num_imported_functions
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.checked_mul(u32::from(self.size_of_vmfunction_import()))
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.unwrap(),
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)
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.unwrap()
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}
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/// The offset of the `memories` array.
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pub fn vmctx_imported_memories_begin(&self) -> u32 {
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self.vmctx_imported_tables_begin()
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.checked_add(
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self.num_imported_tables
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.checked_mul(u32::from(self.size_of_vmtable_import()))
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.unwrap(),
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)
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.unwrap()
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}
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/// The offset of the `globals` array.
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pub fn vmctx_imported_globals_begin(&self) -> u32 {
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self.vmctx_imported_memories_begin()
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.checked_add(
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self.num_imported_memories
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.checked_mul(u32::from(self.size_of_vmmemory_import()))
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.unwrap(),
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)
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.unwrap()
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}
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/// The offset of the `tables` array.
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pub fn vmctx_tables_begin(&self) -> u32 {
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self.vmctx_imported_globals_begin()
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.checked_add(
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self.num_imported_globals
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.checked_mul(u32::from(self.size_of_vmglobal_import()))
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.unwrap(),
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)
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.unwrap()
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}
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/// The offset of the `memories` array.
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pub fn vmctx_memories_begin(&self) -> u32 {
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self.vmctx_tables_begin()
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.checked_add(
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self.num_defined_tables
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.checked_mul(u32::from(self.size_of_vmtable_definition()))
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.unwrap(),
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)
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.unwrap()
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}
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/// The offset of the `globals` array.
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pub fn vmctx_globals_begin(&self) -> u32 {
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let offset = self
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.vmctx_memories_begin()
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.checked_add(
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self.num_defined_memories
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.checked_mul(u32::from(self.size_of_vmmemory_definition()))
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.unwrap(),
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)
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.unwrap();
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align(offset, 16)
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}
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/// The offset of the builtin functions array.
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pub fn vmctx_builtin_functions_begin(&self) -> u32 {
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self.vmctx_globals_begin()
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.checked_add(
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self.num_defined_globals
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.checked_mul(u32::from(self.size_of_vmglobal_definition()))
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.unwrap(),
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)
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.unwrap()
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}
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/// Return the size of the `VMContext` allocation.
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pub fn size_of_vmctx(&self) -> u32 {
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self.vmctx_builtin_functions_begin()
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.checked_add(
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BuiltinFunctionIndex::builtin_functions_total_number()
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.checked_mul(u32::from(self.pointer_size))
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.unwrap(),
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)
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.unwrap()
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}
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/// Return the offset to `VMSharedSignatureId` index `index`.
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pub fn vmctx_vmshared_signature_id(&self, index: SignatureIndex) -> u32 {
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assert_lt!(index.as_u32(), self.num_signature_ids);
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self.vmctx_signature_ids_begin()
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.checked_add(
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index
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.as_u32()
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.checked_mul(u32::from(self.size_of_vmshared_signature_index()))
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.unwrap(),
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)
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.unwrap()
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}
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/// Return the offset to `VMFunctionImport` index `index`.
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pub fn vmctx_vmfunction_import(&self, index: FuncIndex) -> u32 {
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assert_lt!(index.as_u32(), self.num_imported_functions);
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self.vmctx_imported_functions_begin()
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.checked_add(
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index
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.as_u32()
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.checked_mul(u32::from(self.size_of_vmfunction_import()))
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.unwrap(),
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)
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.unwrap()
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}
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/// Return the offset to `VMTableImport` index `index`.
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pub fn vmctx_vmtable_import(&self, index: TableIndex) -> u32 {
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assert_lt!(index.as_u32(), self.num_imported_tables);
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self.vmctx_imported_tables_begin()
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.checked_add(
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index
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.as_u32()
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.checked_mul(u32::from(self.size_of_vmtable_import()))
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.unwrap(),
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)
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.unwrap()
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}
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/// Return the offset to `VMMemoryImport` index `index`.
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pub fn vmctx_vmmemory_import(&self, index: MemoryIndex) -> u32 {
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assert_lt!(index.as_u32(), self.num_imported_memories);
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self.vmctx_imported_memories_begin()
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.checked_add(
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index
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.as_u32()
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.checked_mul(u32::from(self.size_of_vmmemory_import()))
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.unwrap(),
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)
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.unwrap()
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}
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/// Return the offset to `VMGlobalImport` index `index`.
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pub fn vmctx_vmglobal_import(&self, index: GlobalIndex) -> u32 {
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assert_lt!(index.as_u32(), self.num_imported_globals);
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|
self.vmctx_imported_globals_begin()
|
|
.checked_add(
|
|
index
|
|
.as_u32()
|
|
.checked_mul(u32::from(self.size_of_vmglobal_import()))
|
|
.unwrap(),
|
|
)
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to `VMTableDefinition` index `index`.
|
|
pub fn vmctx_vmtable_definition(&self, index: DefinedTableIndex) -> u32 {
|
|
assert_lt!(index.as_u32(), self.num_defined_tables);
|
|
self.vmctx_tables_begin()
|
|
.checked_add(
|
|
index
|
|
.as_u32()
|
|
.checked_mul(u32::from(self.size_of_vmtable_definition()))
|
|
.unwrap(),
|
|
)
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to `VMMemoryDefinition` index `index`.
|
|
pub fn vmctx_vmmemory_definition(&self, index: DefinedMemoryIndex) -> u32 {
|
|
assert_lt!(index.as_u32(), self.num_defined_memories);
|
|
self.vmctx_memories_begin()
|
|
.checked_add(
|
|
index
|
|
.as_u32()
|
|
.checked_mul(u32::from(self.size_of_vmmemory_definition()))
|
|
.unwrap(),
|
|
)
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `VMGlobalDefinition` index `index`.
|
|
pub fn vmctx_vmglobal_definition(&self, index: DefinedGlobalIndex) -> u32 {
|
|
assert_lt!(index.as_u32(), self.num_defined_globals);
|
|
self.vmctx_globals_begin()
|
|
.checked_add(
|
|
index
|
|
.as_u32()
|
|
.checked_mul(u32::from(self.size_of_vmglobal_definition()))
|
|
.unwrap(),
|
|
)
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `body` field in `*const VMFunctionBody` index `index`.
|
|
pub fn vmctx_vmfunction_import_body(&self, index: FuncIndex) -> u32 {
|
|
self.vmctx_vmfunction_import(index)
|
|
.checked_add(u32::from(self.vmfunction_import_body()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `vmctx` field in `*const VMFunctionBody` index `index`.
|
|
pub fn vmctx_vmfunction_import_vmctx(&self, index: FuncIndex) -> u32 {
|
|
self.vmctx_vmfunction_import(index)
|
|
.checked_add(u32::from(self.vmfunction_import_vmctx()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `from` field in `VMTableImport` index `index`.
|
|
pub fn vmctx_vmtable_import_from(&self, index: TableIndex) -> u32 {
|
|
self.vmctx_vmtable_import(index)
|
|
.checked_add(u32::from(self.vmtable_import_from()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `base` field in `VMTableDefinition` index `index`.
|
|
pub fn vmctx_vmtable_definition_base(&self, index: DefinedTableIndex) -> u32 {
|
|
self.vmctx_vmtable_definition(index)
|
|
.checked_add(u32::from(self.vmtable_definition_base()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `current_elements` field in `VMTableDefinition` index `index`.
|
|
pub fn vmctx_vmtable_definition_current_elements(&self, index: DefinedTableIndex) -> u32 {
|
|
self.vmctx_vmtable_definition(index)
|
|
.checked_add(u32::from(self.vmtable_definition_current_elements()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `from` field in `VMMemoryImport` index `index`.
|
|
pub fn vmctx_vmmemory_import_from(&self, index: MemoryIndex) -> u32 {
|
|
self.vmctx_vmmemory_import(index)
|
|
.checked_add(u32::from(self.vmmemory_import_from()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `vmctx` field in `VMMemoryImport` index `index`.
|
|
pub fn vmctx_vmmemory_import_vmctx(&self, index: MemoryIndex) -> u32 {
|
|
self.vmctx_vmmemory_import(index)
|
|
.checked_add(u32::from(self.vmmemory_import_vmctx()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `base` field in `VMMemoryDefinition` index `index`.
|
|
pub fn vmctx_vmmemory_definition_base(&self, index: DefinedMemoryIndex) -> u32 {
|
|
self.vmctx_vmmemory_definition(index)
|
|
.checked_add(u32::from(self.vmmemory_definition_base()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `current_length` field in `VMMemoryDefinition` index `index`.
|
|
pub fn vmctx_vmmemory_definition_current_length(&self, index: DefinedMemoryIndex) -> u32 {
|
|
self.vmctx_vmmemory_definition(index)
|
|
.checked_add(u32::from(self.vmmemory_definition_current_length()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to the `from` field in `VMGlobalImport` index `index`.
|
|
pub fn vmctx_vmglobal_import_from(&self, index: GlobalIndex) -> u32 {
|
|
self.vmctx_vmglobal_import(index)
|
|
.checked_add(u32::from(self.vmglobal_import_from()))
|
|
.unwrap()
|
|
}
|
|
|
|
/// Return the offset to builtin function in `VMBuiltinFunctionsArray` index `index`.
|
|
pub fn vmctx_builtin_function(&self, index: BuiltinFunctionIndex) -> u32 {
|
|
self.vmctx_builtin_functions_begin()
|
|
.checked_add(
|
|
index
|
|
.index()
|
|
.checked_mul(u32::from(self.pointer_size))
|
|
.unwrap(),
|
|
)
|
|
.unwrap()
|
|
}
|
|
}
|
|
|
|
/// Target specific type for shared signature index.
|
|
#[derive(Debug, Copy, Clone)]
|
|
pub struct TargetSharedSignatureIndex(u32);
|
|
|
|
impl TargetSharedSignatureIndex {
|
|
/// Constructs `TargetSharedSignatureIndex`.
|
|
pub fn new(value: u32) -> Self {
|
|
Self(value)
|
|
}
|
|
|
|
/// Returns index value.
|
|
pub fn index(self) -> u32 {
|
|
self.0
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod tests {
|
|
use crate::vmoffsets::align;
|
|
|
|
#[test]
|
|
fn alignment() {
|
|
fn is_aligned(x: u32) -> bool {
|
|
x % 16 == 0
|
|
}
|
|
assert!(is_aligned(align(0, 16)));
|
|
assert!(is_aligned(align(32, 16)));
|
|
assert!(is_aligned(align(33, 16)));
|
|
assert!(is_aligned(align(31, 16)));
|
|
}
|
|
}
|