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feat(compiler): Initial support for GOT-based relocations and compact_unwind tables for Mach-O

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(Work in progress) macOS uses a different scheme for exception handling
in Mach-O; in contrast with the "usual" .eh_frame mechanism, Mach-O has
a `compact_unwind` section in which EH-related metadata are embedded.
This commit begins the effort to support it in its entirety. On the path
to that end, it also adds GOT-based relocations, which are necessary for
Mach-O object files.
This commit is contained in:
Edoardo Marangoni
2025-01-15 12:14:06 +01:00
parent dc227424e1
commit 77e21dad8c
19 changed files with 1061 additions and 253 deletions
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136
lib/compiler-llvm/src/compiler.rs
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@ -9,6 +9,7 @@ use inkwell::targets::FileType;
use inkwell::DLLStorageClass;
use rayon::iter::ParallelBridge;
use rayon::prelude::{IntoParallelIterator, IntoParallelRefIterator, ParallelIterator};
use std::collections::HashSet;
use std::sync::Arc;
use wasmer_compiler::types::function::{Compilation, Dwarf};
use wasmer_compiler::types::module::CompileModuleInfo;
@ -23,6 +24,7 @@ use wasmer_compiler::{
};
use wasmer_types::entity::{EntityRef, PrimaryMap};
use wasmer_types::{CompileError, FunctionIndex, LocalFunctionIndex, SignatureIndex};
use wasmer_vm::libcalls::function_pointer;
//use std::sync::Mutex;
@ -90,6 +92,7 @@ impl LLVMCompiler {
function_body_inputs: &PrimaryMap<LocalFunctionIndex, FunctionBodyData<'_>>,
symbol_registry: &dyn SymbolRegistry,
wasmer_metadata: &[u8],
binary_format: target_lexicon::BinaryFormat,
) -> Result<Vec<u8>, CompileError> {
let target_machine = self.config().target_machine(target);
let ctx = Context::create();
@ -99,7 +102,7 @@ impl LLVMCompiler {
let merged_bitcode = function_body_inputs.into_iter().par_bridge().map_init(
|| {
let target_machine = self.config().target_machine(target);
FuncTranslator::new(target_machine)
FuncTranslator::new(target_machine, binary_format).unwrap()
},
|func_translator, (i, input)| {
let module = func_translator.translate_to_module(
@ -112,6 +115,7 @@ impl LLVMCompiler {
&compile_info.table_styles,
symbol_registry,
)?;
Ok(module.write_bitcode_to_memory().as_slice().to_vec())
},
);
@ -119,7 +123,7 @@ impl LLVMCompiler {
let trampolines_bitcode = compile_info.module.signatures.iter().par_bridge().map_init(
|| {
let target_machine = self.config().target_machine(target);
FuncTrampoline::new(target_machine)
FuncTrampoline::new(target_machine, binary_format).unwrap()
},
|func_trampoline, (i, sig)| {
let name = symbol_registry.symbol_to_name(Symbol::FunctionCallTrampoline(i));
@ -133,7 +137,7 @@ impl LLVMCompiler {
|| {
let target_machine = self.config().target_machine(target);
(
FuncTrampoline::new(target_machine),
FuncTrampoline::new(target_machine, binary_format).unwrap(),
&compile_info.module.signatures,
)
},
@ -196,6 +200,7 @@ impl LLVMCompiler {
callbacks.obj_memory_buffer(&CompiledKind::Module, &memory_buffer);
}
tracing::trace!("Finished compling the module!");
Ok(memory_buffer.as_slice().to_vec())
}
}
@ -228,6 +233,7 @@ impl Compiler for LLVMCompiler {
function_body_inputs,
symbol_registry,
wasmer_metadata,
self.config.target_binary_format(target),
))
}
@ -241,16 +247,25 @@ impl Compiler for LLVMCompiler {
function_body_inputs: PrimaryMap<LocalFunctionIndex, FunctionBodyData<'_>>,
) -> Result<Compilation, CompileError> {
//let data = Arc::new(Mutex::new(0));
let memory_styles = &compile_info.memory_styles;
let table_styles = &compile_info.table_styles;
let binary_format = self.config.target_binary_format(target);
let module = &compile_info.module;
// TODO: merge constants in sections.
let mut module_custom_sections = PrimaryMap::new();
let mut frame_section_bytes = vec![];
let mut frame_section_relocations = vec![];
let mut eh_frame_section_bytes = vec![];
let mut eh_frame_section_relocations = vec![];
let mut compact_unwind_section_bytes = vec![];
let mut compact_unwind_section_relocations = vec![];
let mut got_targets = HashSet::new();
let functions = function_body_inputs
.iter()
.collect::<Vec<(LocalFunctionIndex, &FunctionBodyData<'_>)>>()
@ -258,11 +273,12 @@ impl Compiler for LLVMCompiler {
.map_init(
|| {
let target_machine = self.config().target_machine(target);
FuncTranslator::new(target_machine)
FuncTranslator::new(target_machine, binary_format).unwrap()
},
|func_translator, (i, input)| {
// TODO: remove (to serialize)
//let _data = data.lock().unwrap();
func_translator.translate(
module,
module_translation,
@ -289,16 +305,49 @@ impl Compiler for LLVMCompiler {
)
}
}
compiled_function
.compiled_function
.relocations
.iter()
.filter(|v| v.kind.needs_got())
.for_each(|v| _ = got_targets.insert(v.reloc_target.clone()));
compiled_function
.custom_sections
.iter()
.map(|v| v.1.relocations.iter())
.flatten()
.filter(|v| v.kind.needs_got())
.for_each(|v| _ = got_targets.insert(v.reloc_target.clone()));
if compiled_function
.eh_frame_section_indices
.contains(&section_index)
{
let offset = frame_section_bytes.len() as u32;
let offset = eh_frame_section_bytes.len() as u32;
for reloc in &mut custom_section.relocations {
reloc.offset += offset;
}
frame_section_bytes.extend_from_slice(custom_section.bytes.as_slice());
frame_section_relocations.extend(custom_section.relocations);
eh_frame_section_bytes.extend_from_slice(custom_section.bytes.as_slice());
eh_frame_section_relocations.extend(custom_section.relocations);
// TODO: we do this to keep the count right, remove it.
module_custom_sections.push(CustomSection {
protection: CustomSectionProtection::Read,
bytes: SectionBody::new_with_vec(vec![]),
relocations: vec![],
});
} else if compiled_function
.compact_unwind_section_indices
.contains(&section_index)
{
let offset = compact_unwind_section_bytes.len() as u32;
for reloc in &mut custom_section.relocations {
reloc.offset += offset;
}
compact_unwind_section_bytes
.extend_from_slice(custom_section.bytes.as_slice());
compact_unwind_section_relocations.extend(custom_section.relocations);
// TODO: we do this to keep the count right, remove it.
module_custom_sections.push(CustomSection {
protection: CustomSectionProtection::Read,
@ -320,23 +369,41 @@ impl Compiler for LLVMCompiler {
})
.collect::<PrimaryMap<LocalFunctionIndex, _>>();
let dwarf = if !frame_section_bytes.is_empty() {
let dwarf = Some(Dwarf::new(SectionIndex::from_u32(
module_custom_sections.len() as u32,
)));
let debug = if !eh_frame_section_bytes.is_empty() {
let debug = Dwarf::new(SectionIndex::from_u32(module_custom_sections.len() as u32));
// Do not terminate dwarf info with a zero-length CIE.
// Because more info will be added later
// in lib/object/src/module.rs emit_compilation
module_custom_sections.push(CustomSection {
protection: CustomSectionProtection::Read,
bytes: SectionBody::new_with_vec(frame_section_bytes),
relocations: frame_section_relocations,
bytes: SectionBody::new_with_vec(eh_frame_section_bytes),
relocations: eh_frame_section_relocations,
});
dwarf
Some(debug)
} else {
None
};
//println!("compact_unwind_bytes: {compact_unwind_section_bytes:?}");
let debug = if !compact_unwind_section_bytes.is_empty() {
let section_idx = SectionIndex::from_u32(module_custom_sections.len() as u32);
module_custom_sections.push(CustomSection {
protection: CustomSectionProtection::Read,
bytes: SectionBody::new_with_vec(compact_unwind_section_bytes),
relocations: compact_unwind_section_relocations,
});
if let Some(mut dbg) = debug {
dbg.compact_unwind = Some(section_idx);
Some(dbg)
} else {
Some(Dwarf::new_cu(section_idx))
}
} else {
debug
};
let function_call_trampolines = module
.signatures
.values()
@ -345,7 +412,7 @@ impl Compiler for LLVMCompiler {
.map_init(
|| {
let target_machine = self.config().target_machine(target);
FuncTrampoline::new(target_machine)
FuncTrampoline::new(target_machine, binary_format).unwrap()
},
|func_trampoline, sig| func_trampoline.trampoline(sig, self.config(), ""),
)
@ -360,7 +427,7 @@ impl Compiler for LLVMCompiler {
.map_init(
|| {
let target_machine = self.config().target_machine(target);
FuncTrampoline::new(target_machine)
FuncTrampoline::new(target_machine, binary_format).unwrap()
},
|func_trampoline, func_type| {
func_trampoline.dynamic_trampoline(func_type, self.config(), "")
@ -370,12 +437,43 @@ impl Compiler for LLVMCompiler {
.into_iter()
.collect::<PrimaryMap<_, _>>();
let got = if !got_targets.is_empty() {
let mut got_data = vec![];
let mut map = std::collections::HashMap::new();
for (i, reloc) in got_targets.into_iter().enumerate() {
match reloc {
RelocationTarget::LibCall(c) => got_data.push(function_pointer(c)),
RelocationTarget::LocalFunc(_) => todo!(),
RelocationTarget::CustomSection(_) => todo!(),
}
map.insert(reloc, i);
}
let got_data: Vec<u8> = got_data
.into_iter()
.map(|v| v.to_ne_bytes())
.flatten()
.collect();
let index = SectionIndex::from_u32(module_custom_sections.len() as u32);
module_custom_sections.push(CustomSection {
protection: CustomSectionProtection::Read,
bytes: SectionBody::new_with_vec(got_data),
relocations: vec![],
});
Some(wasmer_compiler::types::function::GOT { index, map })
} else {
None
};
tracing::trace!("Finished compling the module!");
Ok(Compilation {
functions,
custom_sections: module_custom_sections,
function_call_trampolines,
dynamic_function_trampolines,
debug: dwarf,
debug,
got,
})
}
}