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Merge pull request #1466 from peterhuene/fix-unwind-emit

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Refactor unwind generation in Cranelift.
This commit is contained in:
Peter Huene
2020-04-16 13:34:23 -07:00
committed by GitHub
parent 99adc1d218 4d7a283b0c
commit 7d88384c0f
44 changed files with 2700 additions and 3161 deletions
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148
crates/jit/src/code_memory.rs
View File

@@ -1,37 +1,33 @@
//! Memory management for executable code.
use crate::function_table::FunctionTable;
use crate::unwind::UnwindRegistry;
use region;
use std::mem::ManuallyDrop;
use std::{cmp, mem};
use wasmtime_environ::{Compilation, CompiledFunction};
use wasmtime_environ::{
isa::{unwind::UnwindInfo, TargetIsa},
Compilation, CompiledFunction,
};
use wasmtime_runtime::{Mmap, VMFunctionBody};
struct CodeMemoryEntry {
mmap: ManuallyDrop<Mmap>,
table: ManuallyDrop<FunctionTable>,
registry: ManuallyDrop<UnwindRegistry>,
}
impl CodeMemoryEntry {
fn new() -> Self {
Self {
mmap: ManuallyDrop::new(Mmap::new()),
table: ManuallyDrop::new(FunctionTable::new()),
}
}
fn with_capacity(cap: usize) -> Result<Self, String> {
Ok(Self {
mmap: ManuallyDrop::new(Mmap::with_at_least(cap)?),
table: ManuallyDrop::new(FunctionTable::new()),
})
let mmap = ManuallyDrop::new(Mmap::with_at_least(cap)?);
let registry = ManuallyDrop::new(UnwindRegistry::new(mmap.as_ptr() as usize));
Ok(Self { mmap, registry })
}
}
impl Drop for CodeMemoryEntry {
fn drop(&mut self) {
unsafe {
// Table needs to be freed before mmap.
ManuallyDrop::drop(&mut self.table);
// The registry needs to be dropped before the mmap
ManuallyDrop::drop(&mut self.registry);
ManuallyDrop::drop(&mut self.mmap);
}
}
@@ -39,7 +35,7 @@ impl Drop for CodeMemoryEntry {
/// Memory manager for executable code.
pub struct CodeMemory {
current: CodeMemoryEntry,
current: Option<CodeMemoryEntry>,
entries: Vec<CodeMemoryEntry>,
position: usize,
published: usize,
@@ -54,7 +50,7 @@ impl CodeMemory {
/// Create a new `CodeMemory` instance.
pub fn new() -> Self {
Self {
current: CodeMemoryEntry::new(),
current: None,
entries: Vec::new(),
position: 0,
published: 0,
@@ -70,16 +66,14 @@ impl CodeMemory {
) -> Result<&mut [VMFunctionBody], String> {
let size = Self::function_allocation_size(func);
let (buf, table, start) = self.allocate(size)?;
let (buf, registry, start) = self.allocate(size)?;
let (_, _, _, vmfunc) = Self::copy_function(func, start as u32, buf, table);
let (_, _, vmfunc) = Self::copy_function(func, start as u32, buf, registry);
Ok(vmfunc)
}
/// Allocate a continuous memory block for a compilation.
///
/// Allocates memory for both the function bodies as well as function unwind data.
pub fn allocate_for_compilation(
&mut self,
compilation: &Compilation,
@@ -88,33 +82,35 @@ impl CodeMemory {
.into_iter()
.fold(0, |acc, func| acc + Self::function_allocation_size(func));
let (mut buf, mut table, start) = self.allocate(total_len)?;
let (mut buf, registry, start) = self.allocate(total_len)?;
let mut result = Vec::with_capacity(compilation.len());
let mut start = start as u32;
for func in compilation.into_iter() {
let (next_start, next_buf, next_table, vmfunc) =
Self::copy_function(func, start, buf, table);
let (next_start, next_buf, vmfunc) = Self::copy_function(func, start, buf, registry);
result.push(vmfunc);
start = next_start;
buf = next_buf;
table = next_table;
}
Ok(result.into_boxed_slice())
}
/// Make all allocated memory executable.
pub fn publish(&mut self) {
pub fn publish(&mut self, isa: &dyn TargetIsa) {
self.push_current(0)
.expect("failed to push current memory map");
for CodeMemoryEntry { mmap: m, table: t } in &mut self.entries[self.published..] {
for CodeMemoryEntry {
mmap: m,
registry: r,
} in &mut self.entries[self.published..]
{
// Remove write access to the pages due to the relocation fixups.
t.publish(m.as_ptr() as u64)
.expect("failed to publish function table");
r.publish(isa)
.expect("failed to publish function unwind registry");
if !m.is_empty() {
unsafe {
@@ -139,73 +135,79 @@ impl CodeMemory {
/// * The offset within the current mmap that the slice starts at
///
/// TODO: Add an alignment flag.
fn allocate(&mut self, size: usize) -> Result<(&mut [u8], &mut FunctionTable, usize), String> {
if self.current.mmap.len() - self.position < size {
fn allocate(&mut self, size: usize) -> Result<(&mut [u8], &mut UnwindRegistry, usize), String> {
assert!(size > 0);
if match &self.current {
Some(e) => e.mmap.len() - self.position < size,
None => true,
} {
self.push_current(cmp::max(0x10000, size))?;
}
let old_position = self.position;
self.position += size;
let e = self.current.as_mut().unwrap();
Ok((
&mut self.current.mmap.as_mut_slice()[old_position..self.position],
&mut self.current.table,
&mut e.mmap.as_mut_slice()[old_position..self.position],
&mut e.registry,
old_position,
))
}
/// Calculates the allocation size of the given compiled function.
fn function_allocation_size(func: &CompiledFunction) -> usize {
if func.unwind_info.is_empty() {
func.body.len()
} else {
// Account for necessary unwind information alignment padding (32-bit)
((func.body.len() + 3) & !3) + func.unwind_info.len()
match &func.unwind_info {
Some(UnwindInfo::WindowsX64(info)) => {
// Windows unwind information is required to be emitted into code memory
// This is because it must be a positive relative offset from the start of the memory
// Account for necessary unwind information alignment padding (32-bit alignment)
((func.body.len() + 3) & !3) + info.emit_size()
}
_ => func.body.len(),
}
}
/// Copies the data of the compiled function to the given buffer.
///
/// This will also add the function to the current function table.
/// This will also add the function to the current unwind registry.
fn copy_function<'a>(
func: &CompiledFunction,
func_start: u32,
buf: &'a mut [u8],
table: &'a mut FunctionTable,
) -> (
u32,
&'a mut [u8],
&'a mut FunctionTable,
&'a mut [VMFunctionBody],
) {
let func_end = func_start + (func.body.len() as u32);
registry: &mut UnwindRegistry,
) -> (u32, &'a mut [u8], &'a mut [VMFunctionBody]) {
let func_len = func.body.len();
let mut func_end = func_start + (func_len as u32);
let (body, remainder) = buf.split_at_mut(func.body.len());
let (body, mut remainder) = buf.split_at_mut(func_len);
body.copy_from_slice(&func.body);
let vmfunc = Self::view_as_mut_vmfunc_slice(body);
if func.unwind_info.is_empty() {
return (func_end, remainder, table, vmfunc);
if let Some(UnwindInfo::WindowsX64(info)) = &func.unwind_info {
// Windows unwind information is written following the function body
// Keep unwind information 32-bit aligned (round up to the nearest 4 byte boundary)
let unwind_start = (func_end + 3) & !3;
let unwind_size = info.emit_size();
let padding = (unwind_start - func_end) as usize;
let (slice, r) = remainder.split_at_mut(padding + unwind_size);
info.emit(&mut slice[padding..]);
func_end = unwind_start + (unwind_size as u32);
remainder = r;
}
// Keep unwind information 32-bit aligned (round up to the nearest 4 byte boundary)
let padding = ((func.body.len() + 3) & !3) - func.body.len();
let (unwind, remainder) = remainder.split_at_mut(padding + func.unwind_info.len());
let mut relocs = Vec::new();
func.unwind_info
.serialize(&mut unwind[padding..], &mut relocs);
if let Some(info) = &func.unwind_info {
registry
.register(func_start, func_len as u32, info)
.expect("failed to register unwind information");
}
let unwind_start = func_end + (padding as u32);
let unwind_end = unwind_start + (func.unwind_info.len() as u32);
relocs.iter_mut().for_each(move |r| {
r.offset += unwind_start;
r.addend += func_start;
});
table.add_function(func_start, func_end, unwind_start, &relocs);
(unwind_end, remainder, table, vmfunc)
(func_end, remainder, vmfunc)
}
/// Convert mut a slice from u8 to VMFunctionBody.
@@ -215,21 +217,19 @@ impl CodeMemory {
unsafe { &mut *body_ptr }
}
/// Pushes the current Mmap (and function table) and allocates a new Mmap of the given size.
/// Pushes the current entry and allocates a new one with the given size.
fn push_current(&mut self, new_size: usize) -> Result<(), String> {
let previous = mem::replace(
&mut self.current,
if new_size == 0 {
CodeMemoryEntry::new()
None
} else {
CodeMemoryEntry::with_capacity(cmp::max(0x10000, new_size))?
Some(CodeMemoryEntry::with_capacity(cmp::max(0x10000, new_size))?)
},
);
if !previous.mmap.is_empty() {
self.entries.push(previous);
} else {
assert_eq!(previous.table.len(), 0);
if let Some(e) = previous {
self.entries.push(e);
}
self.position = 0;

66
crates/jit/src/compiler.rs
View File

@@ -14,9 +14,9 @@ use wasmtime_environ::entity::{EntityRef, PrimaryMap};
use wasmtime_environ::isa::{TargetFrontendConfig, TargetIsa};
use wasmtime_environ::wasm::{DefinedFuncIndex, DefinedMemoryIndex, MemoryIndex};
use wasmtime_environ::{
CacheConfig, CompileError, CompiledFunction, CompiledFunctionUnwindInfo, Compiler as _C,
ModuleAddressMap, ModuleMemoryOffset, ModuleTranslation, ModuleVmctxInfo, Relocation,
RelocationTarget, Relocations, Traps, Tunables, VMOffsets,
CacheConfig, CompileError, CompiledFunction, Compiler as _C, ModuleAddressMap,
ModuleMemoryOffset, ModuleTranslation, ModuleVmctxInfo, Relocation, RelocationTarget,
Relocations, Traps, Tunables, VMOffsets,
};
use wasmtime_runtime::{
InstantiationError, SignatureRegistry, VMFunctionBody, VMSharedSignatureIndex, VMTrampoline,
@@ -46,7 +46,6 @@ pub enum CompilationStrategy {
/// TODO: Consider using cranelift-module.
pub struct Compiler {
isa: Box<dyn TargetIsa>,
code_memory: CodeMemory,
signatures: SignatureRegistry,
strategy: CompilationStrategy,
@@ -102,34 +101,27 @@ impl Compiler {
translation: &ModuleTranslation,
debug_data: Option<DebugInfoData>,
) -> Result<Compilation, SetupError> {
let (
compilation,
relocations,
address_transform,
value_ranges,
stack_slots,
traps,
frame_layouts,
) = match self.strategy {
// For now, interpret `Auto` as `Cranelift` since that's the most stable
// implementation.
CompilationStrategy::Auto | CompilationStrategy::Cranelift => {
wasmtime_environ::cranelift::Cranelift::compile_module(
translation,
&*self.isa,
&self.cache_config,
)
let (compilation, relocations, address_transform, value_ranges, stack_slots, traps) =
match self.strategy {
// For now, interpret `Auto` as `Cranelift` since that's the most stable
// implementation.
CompilationStrategy::Auto | CompilationStrategy::Cranelift => {
wasmtime_environ::cranelift::Cranelift::compile_module(
translation,
&*self.isa,
&self.cache_config,
)
}
#[cfg(feature = "lightbeam")]
CompilationStrategy::Lightbeam => {
wasmtime_environ::lightbeam::Lightbeam::compile_module(
translation,
&*self.isa,
&self.cache_config,
)
}
}
#[cfg(feature = "lightbeam")]
CompilationStrategy::Lightbeam => {
wasmtime_environ::lightbeam::Lightbeam::compile_module(
translation,
&*self.isa,
&self.cache_config,
)
}
}
.map_err(SetupError::Compile)?;
.map_err(SetupError::Compile)?;
// Allocate all of the compiled functions into executable memory,
// copying over their contents.
@@ -202,8 +194,8 @@ impl Compiler {
&module_vmctx_info,
&address_transform,
&value_ranges,
&frame_layouts,
&funcs,
&compilation,
)
.map_err(SetupError::DebugInfo)?;
Some(bytes)
@@ -227,7 +219,7 @@ impl Compiler {
/// Make memory containing compiled code executable.
pub(crate) fn publish_compiled_code(&mut self) {
self.code_memory.publish();
self.code_memory.publish(self.isa.as_ref());
}
/// Shared signature registry.
@@ -264,7 +256,6 @@ pub fn make_trampoline(
let mut context = Context::new();
context.func = ir::Function::with_name_signature(ir::ExternalName::user(0, 0), wrapper_sig);
context.func.collect_frame_layout_info();
{
let mut builder = FunctionBuilder::new(&mut context.func, fn_builder_ctx);
@@ -343,7 +334,7 @@ pub fn make_trampoline(
)))
})?;
let unwind_info = CompiledFunctionUnwindInfo::new(isa, &context).map_err(|error| {
let unwind_info = context.create_unwind_info(isa).map_err(|error| {
SetupError::Compile(CompileError::Codegen(pretty_error(
&context.func,
Some(isa),
@@ -369,6 +360,10 @@ fn allocate_functions(
code_memory: &mut CodeMemory,
compilation: &wasmtime_environ::Compilation,
) -> Result<PrimaryMap<DefinedFuncIndex, *mut [VMFunctionBody]>, String> {
if compilation.is_empty() {
return Ok(PrimaryMap::new());
}
let fat_ptrs = code_memory.allocate_for_compilation(compilation)?;
// Second, create a PrimaryMap from result vector of pointers.
@@ -377,6 +372,7 @@ fn allocate_functions(
let fat_ptr: *mut [VMFunctionBody] = fat_ptrs[i];
result.push(fat_ptr);
}
Ok(result)
}

224
crates/jit/src/function_table.rs
View File

@@ -1,224 +0,0 @@
//! Runtime function table.
//!
//! This module is primarily used to track JIT functions on Windows for stack walking and unwind.
type FunctionTableReloc = wasmtime_environ::CompiledFunctionUnwindInfoReloc;
/// Represents a runtime function table.
///
/// This is used to register JIT code with the operating system to enable stack walking and unwinding.
#[cfg(all(target_os = "windows", target_arch = "x86_64"))]
pub(crate) struct FunctionTable {
functions: Vec<winapi::um::winnt::RUNTIME_FUNCTION>,
published: bool,
}
#[cfg(all(target_os = "windows", target_arch = "x86_64"))]
impl FunctionTable {
/// Creates a new function table.
pub fn new() -> Self {
Self {
functions: Vec::new(),
published: false,
}
}
/// Returns the number of functions in the table, also referred to as its 'length'.
pub fn len(&self) -> usize {
self.functions.len()
}
/// Adds a function to the table based off of the start offset, end offset, and unwind offset.
///
/// The offsets are from the "module base", which is provided when the table is published.
pub fn add_function(
&mut self,
start: u32,
end: u32,
unwind: u32,
_relocs: &[FunctionTableReloc],
) {
assert_eq!(_relocs.len(), 0);
use winapi::um::winnt;
assert!(!self.published, "table has already been published");
let mut entry = winnt::RUNTIME_FUNCTION::default();
entry.BeginAddress = start;
entry.EndAddress = end;
unsafe {
*entry.u.UnwindInfoAddress_mut() = unwind;
}
self.functions.push(entry);
}
/// Publishes the function table using the given base address.
///
/// A published function table will automatically be deleted when it is dropped.
pub fn publish(&mut self, base_address: u64) -> Result<(), String> {
use winapi::um::winnt;
if self.published {
return Err("function table was already published".into());
}
self.published = true;
if self.functions.is_empty() {
return Ok(());
}
unsafe {
// Windows heap allocations are 32-bit aligned, but assert just in case
assert_eq!(
(self.functions.as_mut_ptr() as u64) % 4,
0,
"function table allocation was not aligned"
);
if winnt::RtlAddFunctionTable(
self.functions.as_mut_ptr(),
self.functions.len() as u32,
base_address,
) == 0
{
return Err("failed to add function table".into());
}
}
Ok(())
}
}
#[cfg(target_os = "windows")]
impl Drop for FunctionTable {
fn drop(&mut self) {
use winapi::um::winnt;
if self.published {
unsafe {
winnt::RtlDeleteFunctionTable(self.functions.as_mut_ptr());
}
}
}
}
/// Represents a runtime function table.
///
/// This is used to register JIT code with the operating system to enable stack walking and unwinding.
#[cfg(unix)]
pub(crate) struct FunctionTable {
functions: Vec<u32>,
relocs: Vec<FunctionTableReloc>,
published: Option<Vec<usize>>,
}
#[cfg(unix)]
impl FunctionTable {
/// Creates a new function table.
pub fn new() -> Self {
Self {
functions: Vec::new(),
relocs: Vec::new(),
published: None,
}
}
/// Returns the number of functions in the table, also referred to as its 'length'.
pub fn len(&self) -> usize {
self.functions.len()
}
/// Adds a function to the table based off of the start offset, end offset, and unwind offset.
///
/// The offsets are from the "module base", which is provided when the table is published.
pub fn add_function(
&mut self,
_start: u32,
_end: u32,
unwind: u32,
relocs: &[FunctionTableReloc],
) {
assert!(self.published.is_none(), "table has already been published");
self.functions.push(unwind);
self.relocs.extend_from_slice(relocs);
}
/// Publishes the function table using the given base address.
///
/// A published function table will automatically be deleted when it is dropped.
pub fn publish(&mut self, base_address: u64) -> Result<(), String> {
if self.published.is_some() {
return Err("function table was already published".into());
}
if self.functions.is_empty() {
assert_eq!(self.relocs.len(), 0);
self.published = Some(vec![]);
return Ok(());
}
extern "C" {
// libunwind import
fn __register_frame(fde: *const u8);
}
for reloc in self.relocs.iter() {
let addr = base_address + (reloc.offset as u64);
let target = base_address + (reloc.addend as u64);
unsafe {
std::ptr::write(addr as *mut u64, target);
}
}
let mut fdes = Vec::with_capacity(self.functions.len());
for unwind_offset in self.functions.iter() {
let addr = base_address + (*unwind_offset as u64);
let off = unsafe { std::ptr::read::<u32>(addr as *const u32) } as usize + 4;
let fde = (addr + off as u64) as usize;
unsafe {
__register_frame(fde as *const _);
}
fdes.push(fde);
}
self.published = Some(fdes);
Ok(())
}
}
#[cfg(unix)]
impl Drop for FunctionTable {
fn drop(&mut self) {
extern "C" {
// libunwind import
fn __deregister_frame(fde: *const u8);
}
if let Some(published) = &self.published {
unsafe {
// I'm not really sure why, but it appears to be way faster to
// unregister frames in reverse order rather than in-order. This
// way we're deregistering in LIFO order, and maybe there's some
// vec shifting or something like that in libgcc?
//
// Locally on Ubuntu 18.04 a wasm module with 40k empty
// functions takes 0.1s to compile and drop with reverse
// iteration. With forward iteration it takes 3s to compile and
// drop!
//
// Poking around libgcc sources seems to indicate that some sort
// of linked list is being traversed... We may need to figure
// out something else for backtraces in the future since this
// API may not be long-lived to keep calling.
for fde in published.iter().rev() {
__deregister_frame(*fde as *const _);
}
}
}
}
}

2
crates/jit/src/lib.rs
View File

@@ -23,11 +23,11 @@
mod code_memory;
mod compiler;
mod function_table;
mod imports;
mod instantiate;
mod link;
mod resolver;
mod unwind;
pub mod native;
pub mod trampoline;

11
crates/jit/src/unwind.rs Normal file
View File

@@ -0,0 +1,11 @@
cfg_if::cfg_if! {
if #[cfg(all(windows, target_arch = "x86_64"))] {
mod winx64;
pub use self::winx64::*;
} else if #[cfg(unix)] {
mod systemv;
pub use self::systemv::*;
} else {
compile_error!("unsupported target platform for unwind");
}
}

150
crates/jit/src/unwind/systemv.rs Normal file
View File

@@ -0,0 +1,150 @@
//! Module for System V ABI unwind registry.
use anyhow::{bail, Result};
use cranelift_codegen::isa::{unwind::UnwindInfo, TargetIsa};
use gimli::{
write::{Address, EhFrame, EndianVec, FrameTable, Writer},
RunTimeEndian,
};
/// Represents a registry of function unwind information for System V ABI.
pub struct UnwindRegistry {
base_address: usize,
functions: Vec<gimli::write::FrameDescriptionEntry>,
frame_table: Vec<u8>,
registrations: Vec<usize>,
published: bool,
}
extern "C" {
// libunwind import
fn __register_frame(fde: *const u8);
fn __deregister_frame(fde: *const u8);
}
impl UnwindRegistry {
/// Creates a new unwind registry with the given base address.
pub fn new(base_address: usize) -> Self {
Self {
base_address,
functions: Vec::new(),
frame_table: Vec::new(),
registrations: Vec::new(),
published: false,
}
}
/// Registers a function given the start offset, length, and unwind information.
pub fn register(&mut self, func_start: u32, _func_len: u32, info: &UnwindInfo) -> Result<()> {
if self.published {
bail!("unwind registry has already been published");
}
match info {
UnwindInfo::SystemV(info) => {
self.functions.push(info.to_fde(Address::Constant(
self.base_address as u64 + func_start as u64,
)));
}
_ => bail!("unsupported unwind information"),
}
Ok(())
}
/// Publishes all registered functions.
pub fn publish(&mut self, isa: &dyn TargetIsa) -> Result<()> {
if self.published {
bail!("unwind registry has already been published");
}
if self.functions.is_empty() {
self.published = true;
return Ok(());
}
self.set_frame_table(isa)?;
unsafe {
self.register_frames();
}
self.published = true;
Ok(())
}
fn set_frame_table(&mut self, isa: &dyn TargetIsa) -> Result<()> {
let mut table = FrameTable::default();
let cie_id = table.add_cie(match isa.create_systemv_cie() {
Some(cie) => cie,
None => bail!("ISA does not support System V unwind information"),
});
let functions = std::mem::replace(&mut self.functions, Vec::new());
for func in functions {
table.add_fde(cie_id, func);
}
let mut eh_frame = EhFrame(EndianVec::new(RunTimeEndian::default()));
table.write_eh_frame(&mut eh_frame).unwrap();
// GCC expects a terminating "empty" length, so write a 0 length at the end of the table.
eh_frame.0.write_u32(0).unwrap();
self.frame_table = eh_frame.0.into_vec();
Ok(())
}
unsafe fn register_frames(&mut self) {
cfg_if::cfg_if! {
if #[cfg(target_os = "macos")] {
// On macOS, `__register_frame` takes a pointer to a single FDE
let start = self.frame_table.as_ptr();
let end = start.add(self.frame_table.len());
let mut current = start;
// Walk all of the entries in the frame table and register them
while current < end {
let len = std::ptr::read::<u32>(current as *const u32) as usize;
// Skip over the CIE
if current != start {
__register_frame(current);
self.registrations.push(current as usize);
}
// Move to the next table entry (+4 because the length itself is not inclusive)
current = current.add(len + 4);
}
} else {
// On other platforms, `__register_frame` will walk the FDEs until an entry of length 0
let ptr = self.frame_table.as_ptr();
__register_frame(ptr);
self.registrations.push(ptr as usize);
}
}
}
}
impl Drop for UnwindRegistry {
fn drop(&mut self) {
if self.published {
unsafe {
// libgcc stores the frame entries as a linked list in decreasing sort order
// based on the PC value of the registered entry.
//
// As we store the registrations in increasing order, it would be O(N^2) to
// deregister in that order.
//
// To ensure that we just pop off the first element in the list upon every
// deregistration, walk our list of registrations backwards.
for fde in self.registrations.iter().rev() {
__deregister_frame(*fde as *const _);
}
}
}
}
}

91
crates/jit/src/unwind/winx64.rs Normal file
View File

@@ -0,0 +1,91 @@
//! Module for Windows x64 ABI unwind registry.
use anyhow::{bail, Result};
use cranelift_codegen::isa::{unwind::UnwindInfo, TargetIsa};
use winapi::um::winnt;
/// Represents a registry of function unwind information for Windows x64 ABI.
pub struct UnwindRegistry {
base_address: usize,
functions: Vec<winnt::RUNTIME_FUNCTION>,
published: bool,
}
impl UnwindRegistry {
/// Creates a new unwind registry with the given base address.
pub fn new(base_address: usize) -> Self {
Self {
base_address,
functions: Vec::new(),
published: false,
}
}
/// Registers a function given the start offset, length, and unwind information.
pub fn register(&mut self, func_start: u32, func_len: u32, info: &UnwindInfo) -> Result<()> {
if self.published {
bail!("unwind registry has already been published");
}
match info {
UnwindInfo::WindowsX64(_) => {
let mut entry = winnt::RUNTIME_FUNCTION::default();
entry.BeginAddress = func_start;
entry.EndAddress = func_start + func_len;
// The unwind information should be immediately following the function
// with padding for 4 byte alignment
unsafe {
*entry.u.UnwindInfoAddress_mut() = (entry.EndAddress + 3) & !3;
}
self.functions.push(entry);
Ok(())
}
_ => bail!("unsupported unwind information"),
}
}
/// Publishes all registered functions.
pub fn publish(&mut self, _isa: &dyn TargetIsa) -> Result<()> {
if self.published {
bail!("unwind registry has already been published");
}
self.published = true;
if !self.functions.is_empty() {
// Windows heap allocations are 32-bit aligned, but assert just in case
assert_eq!(
(self.functions.as_mut_ptr() as u64) % 4,
0,
"function table allocation was not aligned"
);
unsafe {
if winnt::RtlAddFunctionTable(
self.functions.as_mut_ptr(),
self.functions.len() as u32,
self.base_address as u64,
) == 0
{
bail!("failed to register function table");
}
}
}
Ok(())
}
}
impl Drop for UnwindRegistry {
fn drop(&mut self) {
if self.published {
unsafe {
winnt::RtlDeleteFunctionTable(self.functions.as_mut_ptr());
}
}
}
}