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Merge pull request #15 from wasmerio/rust-goblin
Replace llvm objectfile reader with goblin.
This commit is contained in:
nlewycky
GitHub
@ -305,83 +305,99 @@ impl FuncTranslator {
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pos += file.write(&mem_buf_slice[pos..]).unwrap();
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}
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let object = memory_buffer.create_object_file().map_err(|()| {
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CompileError::Codegen("failed to create object file from llvm ir".to_string())
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})?;
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let mem_buf_slice = memory_buffer.as_slice();
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let object = goblin::Object::parse(&mem_buf_slice).unwrap();
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let elf = match object {
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goblin::Object::Elf(elf) => elf,
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_ => unimplemented!("native object file type not supported"),
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};
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let get_section_name = |section: &goblin::elf::section_header::SectionHeader| {
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if section.sh_name == goblin::elf::section_header::SHN_UNDEF as _ {
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return None;
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}
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let name = elf.strtab.get(section.sh_name);
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if name.is_none() {
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return None;
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}
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let name = name.unwrap();
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if name.is_err() {
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return None;
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}
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Some(name.unwrap())
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};
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let wasmer_function_idx = elf
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.section_headers
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.iter()
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.enumerate()
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.filter(|(_, section)| get_section_name(section) == Some("wasmer_function"))
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.map(|(idx, _)| idx)
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.take(1)
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.collect::<Vec<_>>();
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// TODO: handle errors here instead of asserting.
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assert!(wasmer_function_idx.len() == 1);
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let wasmer_function_idx = wasmer_function_idx[0];
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let bytes = elf.section_headers[wasmer_function_idx].file_range();
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let bytes = mem_buf_slice[bytes.start..bytes.end].to_vec();
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let mut bytes = vec![];
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let mut relocations = vec![];
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let mut local_relocations = vec![];
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let mut required_custom_sections = vec![];
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for section in object.get_sections() {
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match section.get_name().map(std::ffi::CStr::to_bytes) {
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Some(b"wasmer_function") => {
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bytes.extend(section.get_contents().to_vec());
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}
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Some(b".relawasmer_function") | Some(b".relwasmer_function") => {
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for rel in section.get_relocations() {
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let (i, cs) = rel.get_type();
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let kind = match (i, cs.to_bytes()) {
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(1, b"R_X86_64_64") => RelocationKind::Abs8,
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_ => unimplemented!("unknown relocation kind {:?}", rel.get_type()),
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};
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let mut reloc_target = None;
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let mut target = None;
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// TODO: fix inkwell API so we don't have a for loop
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// which always breaks after the first entry.
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for symbol in rel.get_symbols() {
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target = symbol
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.get_name()
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.map(|cs| String::from(cs.to_str().unwrap()));
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break;
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}
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// TODO: use a lookup table instead of a linear scan
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if let Some(ref target) = &target {
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if let Some((index, _)) =
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func_names.iter().find(|(_, name)| *name == target)
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{
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let local_index = wasm_module
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.local_func_index(index)
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.expect("Only local functions should be relocated");
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reloc_target = Some(RelocationTarget::LocalFunc(local_index));
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} else {
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if let Some(libcall) = libcalls.get(&target.to_string()) {
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reloc_target = Some(RelocationTarget::LibCall(*libcall));
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}
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}
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}
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if reloc_target.is_some() {
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let reloc_target = reloc_target.unwrap();
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let mut required_custom_sections = HashMap::new();
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relocations.push(Relocation {
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kind,
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reloc_target,
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offset: rel.get_offset() as u32,
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// TODO: it appears the LLVM C API has no way to
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// retrieve the addend.
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addend: 0,
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});
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} else {
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if let Some(ref target) = &target {
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let local_section_index = required_custom_sections.len() as u32;
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required_custom_sections.push(target.clone());
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local_relocations.push(LocalRelocation {
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kind,
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local_section_index,
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offset: rel.get_offset() as u32,
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// TODO: it appears the LLVM C API has no way to
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// retrieve the addend.
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addend: 0,
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});
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}
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}
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for (section_index, reloc_section) in &elf.shdr_relocs {
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let section_name = get_section_name(&elf.section_headers[*section_index]);
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if section_name != Some(".relawasmer_function")
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&& section_name != Some(".relwasmer_function")
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{
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continue;
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}
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for reloc in reloc_section.iter() {
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let kind = match reloc.r_type {
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// TODO: these constants are not per-arch, we'll need to
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// make the whole match per-arch.
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goblin::elf::reloc::R_X86_64_64 => RelocationKind::Abs8,
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_ => unimplemented!("unknown relocation {}", reloc.r_type),
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};
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let offset = reloc.r_offset as u32;
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let addend = reloc.r_addend.unwrap_or(0);
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let target = reloc.r_sym;
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// TODO: error handling
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let target = elf.syms.get(target).unwrap();
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if target.st_type() == goblin::elf::sym::STT_SECTION {
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let len = required_custom_sections.len();
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let entry = required_custom_sections.entry(target.st_shndx);
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let local_section_index = *entry.or_insert(len) as _;
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local_relocations.push(LocalRelocation {
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kind,
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local_section_index,
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offset,
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addend,
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});
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} else if target.st_type() == goblin::elf::sym::STT_NOTYPE
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&& target.st_shndx == goblin::elf::section_header::SHN_UNDEF as _
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{
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// Not defined in this .o file implies that it should
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// be a libcall.
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let name = target.st_name;
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let name = elf.strtab.get(name).unwrap().unwrap();
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if let Some(libcall) = libcalls.get(name) {
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relocations.push(Relocation {
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kind,
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reloc_target: RelocationTarget::LibCall(*libcall),
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offset,
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addend,
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});
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} else {
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unimplemented!("reference to unknown libcall {}", name);
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}
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} else {
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unimplemented!("unknown relocation {:?} with target {:?}", reloc, target);
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}
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_ => {}
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};
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}
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}
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// TODO: verify that we see all of them
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let mut custom_sections = vec![];
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custom_sections.resize(
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required_custom_sections.len(),
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@ -390,15 +406,10 @@ impl FuncTranslator {
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bytes: SectionBody::default(),
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},
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);
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for section in object.get_sections() {
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if let Some(name) = section.get_name().map(std::ffi::CStr::to_bytes) {
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if let Some(index) = required_custom_sections
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.iter()
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.position(|n| n.as_bytes() == name)
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{
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custom_sections[index].bytes.extend(section.get_contents());
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}
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}
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for (section_idx, local_section_idx) in required_custom_sections {
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let bytes = elf.section_headers[section_idx as usize].file_range();
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let bytes = &mem_buf_slice[bytes.start..bytes.end];
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custom_sections[local_section_idx].bytes.extend(bytes);
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}
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let address_map = FunctionAddressMap {
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