rust/src/backend.rs
2020-01-10 13:30:21 +01:00

135 lines
4.5 KiB
Rust

use std::collections::HashMap;
use std::convert::TryFrom;
use rustc::session::Session;
use cranelift_module::{FuncId, Module};
use object::{SectionKind, SymbolFlags, RelocationKind, RelocationEncoding};
use object::write::*;
use cranelift_object::*;
use gimli::SectionId;
use crate::debuginfo::{DebugReloc, DebugRelocName};
pub trait WriteMetadata {
fn add_rustc_section(&mut self, symbol_name: String, data: Vec<u8>, is_like_osx: bool);
}
impl WriteMetadata for object::write::Object {
fn add_rustc_section(&mut self, symbol_name: String, data: Vec<u8>, _is_like_osx: bool) {
let segment = self.segment_name(object::write::StandardSegment::Data).to_vec();
let section_id = self.add_section(segment, b".rustc".to_vec(), object::SectionKind::Data);
let offset = self.append_section_data(section_id, &data, 1);
// For MachO and probably PE this is necessary to prevent the linker from throwing away the
// .rustc section. For ELF this isn't necessary, but it also doesn't harm.
self.add_symbol(object::write::Symbol {
name: symbol_name.into_bytes(),
value: offset,
size: data.len() as u64,
kind: object::SymbolKind::Data,
scope: object::SymbolScope::Dynamic,
weak: false,
section: SymbolSection::Section(section_id),
flags: SymbolFlags::None,
});
}
}
pub trait WriteDebugInfo {
type SectionId;
fn add_debug_section(&mut self, name: SectionId, data: Vec<u8>) -> Self::SectionId;
fn add_debug_reloc(
&mut self,
section_map: &HashMap<SectionId, Self::SectionId>,
symbol_map: &indexmap::IndexMap<FuncId, String>,
from: &Self::SectionId,
reloc: &DebugReloc,
);
}
impl WriteDebugInfo for ObjectProduct {
type SectionId = (object::write::SectionId, object::write::SymbolId);
fn add_debug_section(
&mut self,
id: SectionId,
data: Vec<u8>,
) -> (object::write::SectionId, object::write::SymbolId) {
let name = if self.object.format() == target_lexicon::BinaryFormat::Macho {
id.name().replace('.', "__") // machO expects __debug_info instead of .debug_info
} else {
id.name().to_string()
}.into_bytes();
let segment = self.object.segment_name(StandardSegment::Debug).to_vec();
let section_id = self.object.add_section(segment, name, SectionKind::Debug);
self.object.section_mut(section_id).set_data(data, 1);
let symbol_id = self.object.section_symbol(section_id);
(section_id, symbol_id)
}
fn add_debug_reloc(
&mut self,
section_map: &HashMap<SectionId, Self::SectionId>,
symbol_map: &indexmap::IndexMap<FuncId, String>,
from: &Self::SectionId,
reloc: &DebugReloc,
) {
let (symbol, symbol_offset) = match reloc.name {
DebugRelocName::Section(id) => {
(section_map.get(&id).unwrap().1, 0)
}
DebugRelocName::Symbol(id) => {
let symbol_id = self.function_symbol(*symbol_map.get_index(id).unwrap().0);
self.object.symbol_section_and_offset(symbol_id).expect("Debug reloc for undef sym???")
}
};
self.object.add_relocation(from.0, Relocation {
offset: u64::from(reloc.offset),
symbol,
kind: RelocationKind::Absolute,
encoding: RelocationEncoding::Generic,
size: reloc.size * 8,
addend: i64::try_from(symbol_offset).unwrap() + reloc.addend,
}).unwrap();
}
}
pub trait Emit {
fn emit(self) -> Vec<u8>;
}
impl Emit for ObjectProduct {
fn emit(self) -> Vec<u8> {
self.object.write().unwrap()
}
}
pub fn with_object(sess: &Session, name: &str, f: impl FnOnce(&mut Object)) -> Vec<u8> {
let triple = crate::build_isa(sess, true).triple().clone();
let mut metadata_object =
object::write::Object::new(triple.binary_format, triple.architecture);
metadata_object.add_file_symbol(name.as_bytes().to_vec());
f(&mut metadata_object);
metadata_object.write().unwrap()
}
pub type Backend = impl cranelift_module::Backend<Product: Emit + WriteDebugInfo>;
pub fn make_module(sess: &Session, name: String) -> Module<Backend> {
let module: Module<ObjectBackend> = Module::new(
ObjectBuilder::new(
crate::build_isa(sess, true),
name + ".o",
ObjectTrapCollection::Disabled,
cranelift_module::default_libcall_names(),
)
.unwrap(),
);
module
}