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Remove the stack map registry.

Browse Source 
This commit removes the stack map registry and instead uses the existing
information from the store's module registry to lookup stack maps.

A trait is now used to pass the lookup context to the runtime, implemented by
`Store` to do the lookup.

With this change, module registration in `Store` is now entirely limited to
inserting the module into the module registry.
This commit is contained in:
Peter Huene
2021-04-14 13:45:56 -07:00
parent a2466b3c23
commit ea72c621f0
16 changed files with 158 additions and 264 deletions
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18
crates/environ/src/vmoffsets.rs
View File

@@ -6,7 +6,7 @@
// struct VMContext { // struct VMContext {
// interrupts: *const VMInterrupts, // interrupts: *const VMInterrupts,
// externref_activations_table: *mut VMExternRefActivationsTable, // externref_activations_table: *mut VMExternRefActivationsTable,
// stack_map_registry: *mut StackMapRegistry, // stack_map_lookup: *const dyn StackMapLookup,
// signature_ids: [VMSharedSignatureIndex; module.num_signature_ids], // signature_ids: [VMSharedSignatureIndex; module.num_signature_ids],
// imported_functions: [VMFunctionImport; module.num_imported_functions], // imported_functions: [VMFunctionImport; module.num_imported_functions],
// imported_tables: [VMTableImport; module.num_imported_tables], // imported_tables: [VMTableImport; module.num_imported_tables],
@@ -77,7 +77,7 @@ pub struct VMOffsets {
// precalculated offsets of various member fields // precalculated offsets of various member fields
interrupts: u32, interrupts: u32,
externref_activations_table: u32, externref_activations_table: u32,
stack_map_registry: u32, stack_map_lookup: u32,
signature_ids: u32, signature_ids: u32,
imported_functions: u32, imported_functions: u32,
imported_tables: u32, imported_tables: u32,
@@ -149,7 +149,7 @@ impl From<VMOffsetsFields> for VMOffsets {
num_defined_globals: fields.num_defined_globals, num_defined_globals: fields.num_defined_globals,
interrupts: 0, interrupts: 0,
externref_activations_table: 0, externref_activations_table: 0,
stack_map_registry: 0, stack_map_lookup: 0,
signature_ids: 0, signature_ids: 0,
imported_functions: 0, imported_functions: 0,
imported_tables: 0, imported_tables: 0,
@@ -168,13 +168,13 @@ impl From<VMOffsetsFields> for VMOffsets {
.interrupts .interrupts
.checked_add(u32::from(fields.pointer_size)) .checked_add(u32::from(fields.pointer_size))
.unwrap(); .unwrap();
ret.stack_map_registry = ret ret.stack_map_lookup = ret
.externref_activations_table .externref_activations_table
.checked_add(u32::from(fields.pointer_size)) .checked_add(u32::from(fields.pointer_size))
.unwrap(); .unwrap();
ret.signature_ids = ret ret.signature_ids = ret
.stack_map_registry .stack_map_lookup
.checked_add(u32::from(fields.pointer_size)) .checked_add(u32::from(fields.pointer_size * 2))
.unwrap(); .unwrap();
ret.imported_functions = ret ret.imported_functions = ret
.signature_ids .signature_ids
@@ -507,10 +507,10 @@ impl VMOffsets {
self.externref_activations_table self.externref_activations_table
} }
/// The offset of the `*mut StackMapRegistry` member. /// The offset of the `*const dyn StackMapLookup` member.
#[inline] #[inline]
pub fn vmctx_stack_map_registry(&self) -> u32 { pub fn vmctx_stack_map_lookup(&self) -> u32 {
self.stack_map_registry self.stack_map_lookup
} }
/// The offset of the `signature_ids` array. /// The offset of the `signature_ids` array.

11
crates/jit/src/instantiate.rs
View File

@@ -362,11 +362,18 @@ impl CompiledModule {
} }
/// Gets the function information for a given function index. /// Gets the function information for a given function index.
pub fn func_info(&self, index: DefinedFuncIndex) -> (&FunctionAddressMap, &[TrapInformation]) { pub fn func_info(
&self,
index: DefinedFuncIndex,
) -> (
&FunctionAddressMap,
&[TrapInformation],
&[StackMapInformation],
) {
self.artifacts self.artifacts
.funcs .funcs
.get(index) .get(index)
.map(|f| (&f.address_map, f.traps.as_ref())) .map(|f| (&f.address_map, f.traps.as_ref(), f.stack_maps.as_ref()))
.expect("defined function should be present") .expect("defined function should be present")
} }

201
crates/runtime/src/externref.rs
View File

@@ -103,14 +103,12 @@ use std::alloc::Layout;
use std::any::Any; use std::any::Any;
use std::cell::{Cell, RefCell, UnsafeCell}; use std::cell::{Cell, RefCell, UnsafeCell};
use std::cmp::Ordering; use std::cmp::Ordering;
use std::collections::BTreeMap;
use std::collections::HashSet; use std::collections::HashSet;
use std::hash::{Hash, Hasher}; use std::hash::{Hash, Hasher};
use std::mem; use std::mem;
use std::ops::Deref; use std::ops::Deref;
use std::ptr::{self, NonNull}; use std::ptr::{self, NonNull};
use std::rc::Rc; use wasmtime_environ::ir::StackMap;
use wasmtime_environ::{ir::StackMap, StackMapInformation};
/// An external reference to some opaque data. /// An external reference to some opaque data.
/// ///
@@ -596,10 +594,10 @@ impl VMExternRefActivationsTable {
pub unsafe fn insert_with_gc( pub unsafe fn insert_with_gc(
&self, &self,
externref: VMExternRef, externref: VMExternRef,
stack_maps_registry: &StackMapRegistry, stack_map_lookup: &dyn StackMapLookup,
) { ) {
if let Err(externref) = self.try_insert(externref) { if let Err(externref) = self.try_insert(externref) {
self.gc_and_insert_slow(externref, stack_maps_registry); self.gc_and_insert_slow(externref, stack_map_lookup);
} }
} }
@@ -607,9 +605,9 @@ impl VMExternRefActivationsTable {
unsafe fn gc_and_insert_slow( unsafe fn gc_and_insert_slow(
&self, &self,
externref: VMExternRef, externref: VMExternRef,
stack_maps_registry: &StackMapRegistry, stack_map_lookup: &dyn StackMapLookup,
) { ) {
gc(stack_maps_registry, self); gc(stack_map_lookup, self);
// Might as well insert right into the hash set, rather than the bump // Might as well insert right into the hash set, rather than the bump
// chunk, since we are already on a slow path and we get de-duplication // chunk, since we are already on a slow path and we get de-duplication
@@ -743,182 +741,21 @@ impl VMExternRefActivationsTable {
} }
} }
/// A registry of stack maps for currently active Wasm modules. /// Used by the runtime to lookup a stack map from a PC value.
#[derive(Default)] pub trait StackMapLookup {
pub struct StackMapRegistry { /// Lookup the stack map at a program counter (PC) value.
inner: RefCell<StackMapRegistryInner>, fn lookup(&self, pc: usize) -> Option<*const StackMap>;
} }
#[derive(Default)] pub(crate) struct EmptyStackMapLookup;
struct StackMapRegistryInner {
/// A map from the highest pc in a module, to its stack maps.
///
/// For details, see the comment above `GlobalModuleRegistry`.
ranges: BTreeMap<usize, ModuleStackMaps>,
}
#[derive(Debug)] impl StackMapLookup for EmptyStackMapLookup {
struct ModuleStackMaps { fn lookup(&self, _pc: usize) -> Option<*const StackMap> {
/// The range of PCs that this module covers. Different modules must always None
/// have distinct ranges.
range: std::ops::Range<usize>,
/// A map from a PC in this module (that is a GC safepoint) to its
/// associated stack map. If `None` then it means that the PC is the start
/// of a range which has no stack map.
pc_to_stack_map: Vec<(usize, Option<Rc<StackMap>>)>,
}
impl StackMapRegistry {
/// Register the stack maps for a given module.
///
/// The stack maps should be given as an iterator over a function's PC range
/// in memory (that is, where the JIT actually allocated and emitted the
/// function's code at), and the stack maps and code offsets within that
/// range for each of its GC safepoints.
pub fn register_stack_maps<'a>(
&self,
stack_maps: impl IntoIterator<Item = (std::ops::Range<usize>, &'a [StackMapInformation])>,
) {
let mut min = usize::max_value();
let mut max = 0;
let mut pc_to_stack_map = vec![];
let mut last_is_none_marker = true;
for (range, infos) in stack_maps {
let len = range.end - range.start;
min = std::cmp::min(min, range.start);
max = std::cmp::max(max, range.end);
// Add a marker between functions indicating that this function's pc
// starts with no stack map so when our binary search later on finds
// a pc between the start of the function and the function's first
// stack map it doesn't think the previous stack map is our stack
// map.
//
// We skip this if the previous entry pushed was also a `None`
// marker, in which case the starting pc already has no stack map.
// This is also skipped if the first `code_offset` is zero since
// what we'll push applies for the first pc anyway.
if !last_is_none_marker && (infos.is_empty() || infos[0].code_offset > 0) {
pc_to_stack_map.push((range.start, None));
last_is_none_marker = true;
}
for info in infos {
assert!((info.code_offset as usize) < len);
pc_to_stack_map.push((
range.start + (info.code_offset as usize),
Some(Rc::new(info.stack_map.clone())),
));
last_is_none_marker = false;
}
}
if pc_to_stack_map.is_empty() {
// Nothing to register.
return;
}
let module_stack_maps = ModuleStackMaps {
range: min..max,
pc_to_stack_map,
};
let mut inner = self.inner.borrow_mut();
// Assert that this chunk of ranges doesn't collide with any other known
// chunks.
if let Some((_, prev)) = inner.ranges.range(max..).next() {
assert!(prev.range.start > max);
}
if let Some((prev_end, _)) = inner.ranges.range(..=min).next_back() {
assert!(*prev_end < min);
}
let old = inner.ranges.insert(max, module_stack_maps);
assert!(old.is_none());
}
/// Lookup the stack map for the given PC, if any.
pub fn lookup_stack_map(&self, pc: usize) -> Option<Rc<StackMap>> {
let inner = self.inner.borrow();
let stack_maps = inner.module_stack_maps(pc)?;
// Do a binary search to find the stack map for the given PC.
//
// Because GC safepoints are technically only associated with a single
// PC, we should ideally only care about `Ok(index)` values returned
// from the binary search. However, safepoints are inserted right before
// calls, and there are two things that can disturb the PC/offset
// associated with the safepoint versus the PC we actually use to query
// for the stack map:
//
// 1. The `backtrace` crate gives us the PC in a frame that will be
// *returned to*, and where execution will continue from, rather than
// the PC of the call we are currently at. So we would need to
// disassemble one instruction backwards to query the actual PC for
// the stack map.
//
// TODO: One thing we *could* do to make this a little less error
// prone, would be to assert/check that the nearest GC safepoint
// found is within `max_encoded_size(any kind of call instruction)`
// our queried PC for the target architecture.
//
// 2. Cranelift's stack maps only handle the stack, not
// registers. However, some references that are arguments to a call
// may need to be in registers. In these cases, what Cranelift will
// do is:
//
// a. spill all the live references,
// b. insert a GC safepoint for those references,
// c. reload the references into registers, and finally
// d. make the call.
//
// Step (c) adds drift between the GC safepoint and the location of
// the call, which is where we actually walk the stack frame and
// collect its live references.
//
// Luckily, the spill stack slots for the live references are still
// up to date, so we can still find all the on-stack roots.
// Furthermore, we do not have a moving GC, so we don't need to worry
// whether the following code will reuse the references in registers
// (which would not have been updated to point to the moved objects)
// or reload from the stack slots (which would have been updated to
// point to the moved objects).
let index = match stack_maps
.pc_to_stack_map
.binary_search_by_key(&pc, |(pc, _stack_map)| *pc)
{
// Exact hit.
Ok(i) => i,
// `Err(0)` means that the associated stack map would have been the
// first element in the array if this pc had an associated stack
// map, but this pc does not have an associated stack map. This can
// only happen inside a Wasm frame if there are no live refs at this
// pc.
Err(0) => return None,
Err(n) => n - 1,
};
let stack_map = stack_maps.pc_to_stack_map[index].1.as_ref()?.clone();
Some(stack_map)
} }
} }
impl StackMapRegistryInner { pub(crate) const EMPTY_STACK_MAP_LOOKUP: EmptyStackMapLookup = EmptyStackMapLookup;
fn module_stack_maps(&self, pc: usize) -> Option<&ModuleStackMaps> {
let (end, stack_maps) = self.ranges.range(pc..).next()?;
if pc < stack_maps.range.start || *end < pc {
None
} else {
Some(stack_maps)
}
}
}
#[derive(Debug, Default)] #[derive(Debug, Default)]
struct DebugOnly<T> { struct DebugOnly<T> {
@@ -965,7 +802,7 @@ impl<T> std::ops::DerefMut for DebugOnly<T> {
/// Additionally, you must have registered the stack maps for every Wasm module /// Additionally, you must have registered the stack maps for every Wasm module
/// that has frames on the stack with the given `stack_maps_registry`. /// that has frames on the stack with the given `stack_maps_registry`.
pub unsafe fn gc( pub unsafe fn gc(
stack_maps_registry: &StackMapRegistry, stack_map_lookup: &dyn StackMapLookup,
externref_activations_table: &VMExternRefActivationsTable, externref_activations_table: &VMExternRefActivationsTable,
) { ) {
// We borrow the precise stack roots `RefCell` for the whole duration of // We borrow the precise stack roots `RefCell` for the whole duration of
@@ -1003,7 +840,7 @@ pub unsafe fn gc(
if cfg!(debug_assertions) { if cfg!(debug_assertions) {
// Assert that there aren't any Wasm frames on the stack. // Assert that there aren't any Wasm frames on the stack.
backtrace::trace(|frame| { backtrace::trace(|frame| {
let stack_map = stack_maps_registry.lookup_stack_map(frame.ip() as usize); let stack_map = stack_map_lookup.lookup(frame.ip() as usize);
assert!(stack_map.is_none()); assert!(stack_map.is_none());
true true
}); });
@@ -1048,11 +885,11 @@ pub unsafe fn gc(
let pc = frame.ip() as usize; let pc = frame.ip() as usize;
let sp = frame.sp() as usize; let sp = frame.sp() as usize;
if let Some(stack_map) = stack_maps_registry.lookup_stack_map(pc) { if let Some(stack_map) = stack_map_lookup.lookup(pc) {
debug_assert!(sp != 0, "we should always get a valid SP for Wasm frames"); debug_assert!(sp != 0, "we should always get a valid SP for Wasm frames");
for i in 0..(stack_map.mapped_words() as usize) { for i in 0..((*stack_map).mapped_words() as usize) {
if stack_map.get_bit(i) { if (*stack_map).get_bit(i) {
// Stack maps have one bit per word in the frame, and the // Stack maps have one bit per word in the frame, and the
// zero^th bit is the *lowest* addressed word in the frame, // zero^th bit is the *lowest* addressed word in the frame,
// i.e. the closest to the SP. So to get the `i`^th word in // i.e. the closest to the SP. So to get the `i`^th word in

8
crates/runtime/src/instance.rs
View File

@@ -3,7 +3,7 @@
//! `InstanceHandle` is a reference-counting handle for an `Instance`. //! `InstanceHandle` is a reference-counting handle for an `Instance`.
use crate::export::Export; use crate::export::Export;
use crate::externref::{StackMapRegistry, VMExternRefActivationsTable}; use crate::externref::{StackMapLookup, VMExternRefActivationsTable};
use crate::memory::{Memory, RuntimeMemoryCreator}; use crate::memory::{Memory, RuntimeMemoryCreator};
use crate::table::{Table, TableElement}; use crate::table::{Table, TableElement};
use crate::traphandlers::Trap; use crate::traphandlers::Trap;
@@ -249,9 +249,9 @@ impl Instance {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_externref_activations_table()) } unsafe { self.vmctx_plus_offset(self.offsets.vmctx_externref_activations_table()) }
} }
/// Return a pointer to the `StackMapRegistry`. /// Return a pointer to the `StackMapLookup`.
pub fn stack_map_registry(&self) -> *mut *mut StackMapRegistry { pub fn stack_map_lookup(&self) -> *mut *const dyn StackMapLookup {
unsafe { self.vmctx_plus_offset(self.offsets.vmctx_stack_map_registry()) } unsafe { self.vmctx_plus_offset(self.offsets.vmctx_stack_map_lookup()) }
} }
/// Return a reference to the vmctx used by compiled wasm code. /// Return a reference to the vmctx used by compiled wasm code.

8
crates/runtime/src/instance/allocator.rs
View File

@@ -1,4 +1,4 @@
use crate::externref::{StackMapRegistry, VMExternRefActivationsTable}; use crate::externref::{StackMapLookup, VMExternRefActivationsTable, EMPTY_STACK_MAP_LOOKUP};
use crate::imports::Imports; use crate::imports::Imports;
use crate::instance::{Instance, InstanceHandle, RuntimeMemoryCreator}; use crate::instance::{Instance, InstanceHandle, RuntimeMemoryCreator};
use crate::memory::{DefaultMemoryCreator, Memory}; use crate::memory::{DefaultMemoryCreator, Memory};
@@ -57,8 +57,8 @@ pub struct InstanceAllocationRequest<'a> {
/// The pointer to the reference activations table to use for the instance. /// The pointer to the reference activations table to use for the instance.
pub externref_activations_table: *mut VMExternRefActivationsTable, pub externref_activations_table: *mut VMExternRefActivationsTable,
/// The pointer to the stack map registry to use for the instance. /// The pointer to the stack map lookup to use for the instance.
pub stack_map_registry: *mut StackMapRegistry, pub stack_map_lookup: Option<*const dyn StackMapLookup>,
} }
/// An link error while instantiating a module. /// An link error while instantiating a module.
@@ -447,7 +447,7 @@ unsafe fn initialize_vmcontext(instance: &Instance, req: InstanceAllocationReque
*instance.interrupts() = req.interrupts; *instance.interrupts() = req.interrupts;
*instance.externref_activations_table() = req.externref_activations_table; *instance.externref_activations_table() = req.externref_activations_table;
*instance.stack_map_registry() = req.stack_map_registry; *instance.stack_map_lookup() = req.stack_map_lookup.unwrap_or(&EMPTY_STACK_MAP_LOOKUP);
// Initialize shared signatures // Initialize shared signatures
let mut ptr = instance.signature_ids_ptr(); let mut ptr = instance.signature_ids_ptr();

4
crates/runtime/src/instance/allocator/pooling.rs
View File

@@ -1370,7 +1370,7 @@ mod test {
host_state: Box::new(()), host_state: Box::new(()),
interrupts: std::ptr::null(), interrupts: std::ptr::null(),
externref_activations_table: std::ptr::null_mut(), externref_activations_table: std::ptr::null_mut(),
stack_map_registry: std::ptr::null_mut(), stack_map_lookup: None,
}, },
) )
.expect("allocation should succeed"), .expect("allocation should succeed"),
@@ -1394,7 +1394,7 @@ mod test {
host_state: Box::new(()), host_state: Box::new(()),
interrupts: std::ptr::null(), interrupts: std::ptr::null(),
externref_activations_table: std::ptr::null_mut(), externref_activations_table: std::ptr::null_mut(),
stack_map_registry: std::ptr::null_mut(), stack_map_lookup: None,
}, },
) { ) {
Err(InstantiationError::Limit(3)) => {} Err(InstantiationError::Limit(3)) => {}

2
crates/runtime/src/instance/allocator/pooling/uffd.rs
View File

@@ -523,7 +523,7 @@ mod test {
host_state: Box::new(()), host_state: Box::new(()),
interrupts: ptr::null(), interrupts: ptr::null(),
externref_activations_table: ptr::null_mut(), externref_activations_table: ptr::null_mut(),
stack_map_registry: ptr::null_mut(), stack_map_lookup: None,
}, },
) )
.expect("instance should allocate"), .expect("instance should allocate"),

8
crates/runtime/src/libcalls.rs
View File

@@ -449,8 +449,8 @@ pub unsafe extern "C" fn wasmtime_activations_table_insert_with_gc(
let externref = VMExternRef::clone_from_raw(externref); let externref = VMExternRef::clone_from_raw(externref);
let instance = (&mut *vmctx).instance(); let instance = (&mut *vmctx).instance();
let activations_table = &**instance.externref_activations_table(); let activations_table = &**instance.externref_activations_table();
let registry = &**instance.stack_map_registry(); let stack_map_lookup = &**instance.stack_map_lookup();
activations_table.insert_with_gc(externref, registry); activations_table.insert_with_gc(externref, stack_map_lookup);
} }
/// Perform a Wasm `global.get` for `externref` globals. /// Perform a Wasm `global.get` for `externref` globals.
@@ -466,8 +466,8 @@ pub unsafe extern "C" fn wasmtime_externref_global_get(
Some(externref) => { Some(externref) => {
let raw = externref.as_raw(); let raw = externref.as_raw();
let activations_table = &**instance.externref_activations_table(); let activations_table = &**instance.externref_activations_table();
let registry = &**instance.stack_map_registry(); let stack_map_lookup = &**instance.stack_map_lookup();
activations_table.insert_with_gc(externref, registry); activations_table.insert_with_gc(externref, stack_map_lookup);
raw raw
} }
} }

2
crates/wasmtime/src/func/typed.rs
View File

@@ -207,7 +207,7 @@ unsafe impl WasmTy for Option<ExternRef> {
unsafe { unsafe {
store store
.externref_activations_table() .externref_activations_table()
.insert_with_gc(x.inner, store.stack_map_registry()); .insert_with_gc(x.inner, &*store.stack_map_lookup());
} }
abi abi
} else { } else {

5
crates/wasmtime/src/instance.rs
View File

@@ -13,7 +13,7 @@ use wasmtime_environ::wasm::{
}; };
use wasmtime_environ::Initializer; use wasmtime_environ::Initializer;
use wasmtime_runtime::{ use wasmtime_runtime::{
Imports, InstanceAllocationRequest, InstantiationError, RuntimeInstance, StackMapRegistry, Imports, InstanceAllocationRequest, InstantiationError, RuntimeInstance, StackMapLookup,
VMContext, VMExternRefActivationsTable, VMFunctionBody, VMFunctionImport, VMGlobalImport, VMContext, VMExternRefActivationsTable, VMFunctionBody, VMFunctionImport, VMGlobalImport,
VMMemoryImport, VMTableImport, VMMemoryImport, VMTableImport,
}; };
@@ -525,8 +525,7 @@ impl<'a> Instantiator<'a> {
externref_activations_table: self.store.externref_activations_table() externref_activations_table: self.store.externref_activations_table()
as *const VMExternRefActivationsTable as *const VMExternRefActivationsTable
as *mut _, as *mut _,
stack_map_registry: self.store.stack_map_registry() as *const StackMapRegistry stack_map_lookup: Some(self.store.stack_map_lookup() as *const dyn StackMapLookup),
as *mut _,
})?; })?;
// After we've created the `InstanceHandle` we still need to run // After we've created the `InstanceHandle` we still need to run

82
crates/wasmtime/src/module/registry.rs
View File

@@ -43,6 +43,11 @@ impl ModuleRegistry {
self.module(pc)?.lookup_trap_info(pc) self.module(pc)?.lookup_trap_info(pc)
} }
/// Looks up a stack map from a program counter.
pub fn lookup_stack_map<'a>(&'a self, pc: usize) -> Option<&'a ir::StackMap> {
self.module(pc)?.lookup_stack_map(pc)
}
fn module(&self, pc: usize) -> Option<&RegisteredModule> { fn module(&self, pc: usize) -> Option<&RegisteredModule> {
let (end, info) = self.0.range(pc..).next()?; let (end, info) = self.0.range(pc..).next()?;
if pc < info.start || *end < pc { if pc < info.start || *end < pc {
@@ -53,13 +58,13 @@ impl ModuleRegistry {
} }
/// Registers a new module with the registry. /// Registers a new module with the registry.
pub fn register(&mut self, module: &Module) -> bool { pub fn register(&mut self, module: &Module) {
let compiled_module = module.compiled_module(); let compiled_module = module.compiled_module();
let (start, end) = compiled_module.code().range(); let (start, end) = compiled_module.code().range();
// Ignore modules with no code, finished functions, or if the module is already registered // Ignore modules with no code, finished functions, or if the module is already registered
if start == end || compiled_module.finished_functions().is_empty() { if start == end || compiled_module.finished_functions().is_empty() {
return false; return;
} }
// The module code range is exclusive for end, so make it inclusive as it // The module code range is exclusive for end, so make it inclusive as it
@@ -67,7 +72,7 @@ impl ModuleRegistry {
let end = end - 1; let end = end - 1;
if self.0.get(&end).is_some() { if self.0.get(&end).is_some() {
return false; return;
} }
// Assert that this module's code doesn't collide with any other registered modules // Assert that this module's code doesn't collide with any other registered modules
@@ -90,7 +95,6 @@ impl ModuleRegistry {
assert!(prev.is_none()); assert!(prev.is_none());
GLOBAL_MODULES.lock().unwrap().register(start, end, module); GLOBAL_MODULES.lock().unwrap().register(start, end, module);
true
} }
/// Looks up a trampoline from a shared signature index. /// Looks up a trampoline from a shared signature index.
@@ -135,7 +139,7 @@ impl RegisteredModule {
/// if no information can be found. /// if no information can be found.
pub fn lookup_frame_info(&self, pc: usize) -> Option<FrameInfo> { pub fn lookup_frame_info(&self, pc: usize) -> Option<FrameInfo> {
let (index, offset) = self.func(pc)?; let (index, offset) = self.func(pc)?;
let (addr_map, _) = self.module.func_info(index); let (addr_map, _, _) = self.module.func_info(index);
let pos = Self::instr_pos(offset, addr_map); let pos = Self::instr_pos(offset, addr_map);
// In debug mode for now assert that we found a mapping for `pc` within // In debug mode for now assert that we found a mapping for `pc` within
@@ -197,13 +201,77 @@ impl RegisteredModule {
/// Fetches trap information about a program counter in a backtrace. /// Fetches trap information about a program counter in a backtrace.
pub fn lookup_trap_info(&self, pc: usize) -> Option<&TrapInformation> { pub fn lookup_trap_info(&self, pc: usize) -> Option<&TrapInformation> {
let (index, offset) = self.func(pc)?; let (index, offset) = self.func(pc)?;
let (_, traps) = self.module.func_info(index); let (_, traps, _) = self.module.func_info(index);
let idx = traps let idx = traps
.binary_search_by_key(&offset, |info| info.code_offset) .binary_search_by_key(&offset, |info| info.code_offset)
.ok()?; .ok()?;
Some(&traps[idx]) Some(&traps[idx])
} }
/// Looks up a stack map from a program counter
pub fn lookup_stack_map(&self, pc: usize) -> Option<&ir::StackMap> {
let (index, offset) = self.func(pc)?;
let (_, _, stack_maps) = self.module.func_info(index);
// Do a binary search to find the stack map for the given offset.
//
// Because GC safepoints are technically only associated with a single
// PC, we should ideally only care about `Ok(index)` values returned
// from the binary search. However, safepoints are inserted right before
// calls, and there are two things that can disturb the PC/offset
// associated with the safepoint versus the PC we actually use to query
// for the stack map:
//
// 1. The `backtrace` crate gives us the PC in a frame that will be
// *returned to*, and where execution will continue from, rather than
// the PC of the call we are currently at. So we would need to
// disassemble one instruction backwards to query the actual PC for
// the stack map.
//
// TODO: One thing we *could* do to make this a little less error
// prone, would be to assert/check that the nearest GC safepoint
// found is within `max_encoded_size(any kind of call instruction)`
// our queried PC for the target architecture.
//
// 2. Cranelift's stack maps only handle the stack, not
// registers. However, some references that are arguments to a call
// may need to be in registers. In these cases, what Cranelift will
// do is:
//
// a. spill all the live references,
// b. insert a GC safepoint for those references,
// c. reload the references into registers, and finally
// d. make the call.
//
// Step (c) adds drift between the GC safepoint and the location of
// the call, which is where we actually walk the stack frame and
// collect its live references.
//
// Luckily, the spill stack slots for the live references are still
// up to date, so we can still find all the on-stack roots.
// Furthermore, we do not have a moving GC, so we don't need to worry
// whether the following code will reuse the references in registers
// (which would not have been updated to point to the moved objects)
// or reload from the stack slots (which would have been updated to
// point to the moved objects).
let index = match stack_maps.binary_search_by_key(&offset, |i| i.code_offset) {
// Exact hit.
Ok(i) => i,
// `Err(0)` means that the associated stack map would have been the
// first element in the array if this pc had an associated stack
// map, but this pc does not have an associated stack map. This can
// only happen inside a Wasm frame if there are no live refs at this
// pc.
Err(0) => return None,
Err(i) => i - 1,
};
Some(&stack_maps[index].stack_map)
}
fn func(&self, pc: usize) -> Option<(DefinedFuncIndex, u32)> { fn func(&self, pc: usize) -> Option<(DefinedFuncIndex, u32)> {
let (index, start, _) = self.module.func_by_pc(pc)?; let (index, start, _) = self.module.func_by_pc(pc)?;
Some((index, (pc - start) as u32)) Some((index, (pc - start) as u32))
@@ -260,7 +328,7 @@ impl GlobalModuleRegistry {
match info.module.func(pc) { match info.module.func(pc) {
Some((index, offset)) => { Some((index, offset)) => {
let (addr_map, _) = info.module.module.func_info(index); let (addr_map, _, _) = info.module.module.func_info(index);
RegisteredModule::instr_pos(offset, addr_map).is_some() RegisteredModule::instr_pos(offset, addr_map).is_some()
} }
None => false, None => false,

57
crates/wasmtime/src/store.rs
View File

@@ -16,11 +16,11 @@ use std::rc::Rc;
use std::sync::Arc; use std::sync::Arc;
use std::task::{Context, Poll}; use std::task::{Context, Poll};
use wasmtime_environ::wasm::WasmFuncType; use wasmtime_environ::wasm::WasmFuncType;
use wasmtime_jit::{CompiledModule, ModuleCode}; use wasmtime_jit::ModuleCode;
use wasmtime_runtime::{ use wasmtime_runtime::{
InstanceAllocator, InstanceHandle, OnDemandInstanceAllocator, SignalHandler, StackMapRegistry, InstanceAllocator, InstanceHandle, OnDemandInstanceAllocator, SignalHandler, TrapInfo,
TrapInfo, VMContext, VMExternRef, VMExternRefActivationsTable, VMInterrupts, VMContext, VMExternRef, VMExternRefActivationsTable, VMInterrupts, VMSharedSignatureIndex,
VMSharedSignatureIndex, VMTrampoline, VMTrampoline,
}; };
/// Used to associate instances with the store. /// Used to associate instances with the store.
@@ -75,7 +75,6 @@ pub(crate) struct StoreInner {
instances: RefCell<Vec<StoreInstance>>, instances: RefCell<Vec<StoreInstance>>,
signal_handler: RefCell<Option<Box<SignalHandler<'static>>>>, signal_handler: RefCell<Option<Box<SignalHandler<'static>>>>,
externref_activations_table: VMExternRefActivationsTable, externref_activations_table: VMExternRefActivationsTable,
stack_map_registry: StackMapRegistry,
modules: RefCell<ModuleRegistry>, modules: RefCell<ModuleRegistry>,
trampolines: RefCell<TrampolineMap>, trampolines: RefCell<TrampolineMap>,
// Numbers of resources instantiated in this store. // Numbers of resources instantiated in this store.
@@ -139,7 +138,6 @@ impl Store {
instances: RefCell::new(Vec::new()), instances: RefCell::new(Vec::new()),
signal_handler: RefCell::new(None), signal_handler: RefCell::new(None),
externref_activations_table: VMExternRefActivationsTable::new(), externref_activations_table: VMExternRefActivationsTable::new(),
stack_map_registry: StackMapRegistry::default(),
modules: RefCell::new(ModuleRegistry::default()), modules: RefCell::new(ModuleRegistry::default()),
trampolines: RefCell::new(TrampolineMap::default()), trampolines: RefCell::new(TrampolineMap::default()),
instance_count: Default::default(), instance_count: Default::default(),
@@ -207,26 +205,7 @@ impl Store {
pub(crate) fn register_module(&self, module: &Module) { pub(crate) fn register_module(&self, module: &Module) {
// Register the module with the registry // Register the module with the registry
if !self.inner.modules.borrow_mut().register(module) { self.inner.modules.borrow_mut().register(module);
return;
}
// We need to know about all the stack maps of all instantiated modules
// so when performing a GC we know about all wasm frames that we find
// on the stack.
self.register_stack_maps(module.compiled_module());
}
fn register_stack_maps(&self, module: &CompiledModule) {
self.stack_map_registry()
.register_stack_maps(module.stack_maps().map(|(func, stack_maps)| unsafe {
let ptr = (*func).as_ptr();
let len = (*func).len();
let start = ptr as usize;
let end = ptr as usize + len;
let range = start..end;
(range, stack_maps)
}));
} }
// This is used to register a `Func` with the store // This is used to register a `Func` with the store
@@ -448,10 +427,6 @@ impl Store {
} }
#[inline] #[inline]
pub(crate) fn stack_map_registry(&self) -> &StackMapRegistry {
&self.inner.stack_map_registry
}
pub(crate) fn modules(&self) -> &RefCell<ModuleRegistry> { pub(crate) fn modules(&self) -> &RefCell<ModuleRegistry> {
&self.inner.modules &self.inner.modules
} }
@@ -471,20 +446,21 @@ impl Store {
/// ///
/// It is fine to call this several times: only the first call will have an effect. /// It is fine to call this several times: only the first call will have an effect.
pub unsafe fn notify_switched_thread(&self) { pub unsafe fn notify_switched_thread(&self) {
wasmtime_runtime::init_traps(frame_info::GlobalFrameInfo::is_wasm_pc) wasmtime_runtime::init_traps(crate::module::GlobalModuleRegistry::is_wasm_pc)
.expect("failed to initialize per-threads traps"); .expect("failed to initialize per-threads traps");
} }
#[inline]
pub(crate) fn stack_map_lookup(&self) -> *const dyn wasmtime_runtime::StackMapLookup {
self.inner.as_ref()
}
/// Perform garbage collection of `ExternRef`s. /// Perform garbage collection of `ExternRef`s.
pub fn gc(&self) { pub fn gc(&self) {
// For this crate's API, we ensure that `set_stack_canary` invariants // For this crate's API, we ensure that `set_stack_canary` invariants
// are upheld for all host-->Wasm calls, and we register every module // are upheld for all host-->Wasm calls.
// used with this store in `self.inner.stack_map_registry`.
unsafe { unsafe {
wasmtime_runtime::gc( wasmtime_runtime::gc(self.inner.as_ref(), &self.inner.externref_activations_table);
&self.inner.stack_map_registry,
&self.inner.externref_activations_table,
);
} }
} }
@@ -951,6 +927,13 @@ impl Drop for StoreInner {
} }
} }
impl wasmtime_runtime::StackMapLookup for StoreInner {
fn lookup(&self, pc: usize) -> Option<*const wasmtime_environ::ir::StackMap> {
// The address of the stack map is stable for the lifetime of the store
self.modules.borrow().lookup_stack_map(pc).map(|m| m as _)
}
}
/// A threadsafe handle used to interrupt instances executing within a /// A threadsafe handle used to interrupt instances executing within a
/// particular `Store`. /// particular `Store`.
/// ///

6
crates/wasmtime/src/trampoline.rs
View File

@@ -19,8 +19,8 @@ use std::sync::Arc;
use wasmtime_environ::{entity::PrimaryMap, wasm, Module}; use wasmtime_environ::{entity::PrimaryMap, wasm, Module};
use wasmtime_runtime::{ use wasmtime_runtime::{
Imports, InstanceAllocationRequest, InstanceAllocator, InstanceHandle, Imports, InstanceAllocationRequest, InstanceAllocator, InstanceHandle,
OnDemandInstanceAllocator, StackMapRegistry, VMExternRefActivationsTable, VMFunctionBody, OnDemandInstanceAllocator, VMExternRefActivationsTable, VMFunctionBody, VMFunctionImport,
VMFunctionImport, VMSharedSignatureIndex, VMSharedSignatureIndex,
}; };
/// A wrapper around `wasmtime_runtime::InstanceHandle` which pairs it with the /// A wrapper around `wasmtime_runtime::InstanceHandle` which pairs it with the
@@ -77,7 +77,7 @@ fn create_handle(
externref_activations_table: store.externref_activations_table() externref_activations_table: store.externref_activations_table()
as *const VMExternRefActivationsTable as *const VMExternRefActivationsTable
as *mut _, as *mut _,
stack_map_registry: store.stack_map_registry() as *const StackMapRegistry as *mut _, stack_map_lookup: Some(store.stack_map_lookup()),
}, },
)?; )?;

4
crates/wasmtime/src/trampoline/create_handle.rs
View File

@@ -9,7 +9,7 @@ use wasmtime_environ::entity::PrimaryMap;
use wasmtime_environ::wasm::DefinedFuncIndex; use wasmtime_environ::wasm::DefinedFuncIndex;
use wasmtime_environ::Module; use wasmtime_environ::Module;
use wasmtime_runtime::{ use wasmtime_runtime::{
Imports, InstanceAllocationRequest, InstanceAllocator, StackMapRegistry, Imports, InstanceAllocationRequest, InstanceAllocator, StackMapLookup,
VMExternRefActivationsTable, VMFunctionBody, VMFunctionImport, VMSharedSignatureIndex, VMExternRefActivationsTable, VMFunctionBody, VMFunctionImport, VMSharedSignatureIndex,
}; };
@@ -43,7 +43,7 @@ pub(crate) fn create_handle(
externref_activations_table: store.externref_activations_table() externref_activations_table: store.externref_activations_table()
as *const VMExternRefActivationsTable as *const VMExternRefActivationsTable
as *mut _, as *mut _,
stack_map_registry: store.stack_map_registry() as *const StackMapRegistry as *mut _, stack_map_lookup: &store,
})?; })?;
Ok(store.add_instance(handle, true)) Ok(store.add_instance(handle, true))

4
crates/wasmtime/src/trampoline/func.rs
View File

@@ -283,7 +283,7 @@ pub fn create_function(
host_state: Box::new(trampoline_state), host_state: Box::new(trampoline_state),
interrupts: std::ptr::null(), interrupts: std::ptr::null(),
externref_activations_table: std::ptr::null_mut(), externref_activations_table: std::ptr::null_mut(),
stack_map_registry: std::ptr::null_mut(), stack_map_lookup: None,
})?, })?,
trampoline, trampoline,
)) ))
@@ -315,7 +315,7 @@ pub unsafe fn create_raw_function(
host_state, host_state,
interrupts: std::ptr::null(), interrupts: std::ptr::null(),
externref_activations_table: std::ptr::null_mut(), externref_activations_table: std::ptr::null_mut(),
stack_map_registry: std::ptr::null_mut(), stack_map_lookup: None,
})?, })?,
) )
} }

2
crates/wasmtime/src/values.rs
View File

@@ -98,7 +98,7 @@ impl Val {
let externref_ptr = x.inner.as_raw(); let externref_ptr = x.inner.as_raw();
store store
.externref_activations_table() .externref_activations_table()
.insert_with_gc(x.inner, store.stack_map_registry()); .insert_with_gc(x.inner, &*store.stack_map_lookup());
ptr::write(p as *mut *mut u8, externref_ptr) ptr::write(p as *mut *mut u8, externref_ptr)
} }
Val::FuncRef(f) => ptr::write( Val::FuncRef(f) => ptr::write(