from dataclasses import dataclass from error import Traceback import x86 import elf.structs as elf # TODO: Add CLI options of symbol behavior def determine_symbol_binding(symbol_name: str): if symbol_name.startswith("."): # It's a section return elf.SymbolBinding.LOCAL elif symbol_name.startswith("_") and symbol_name != "_start": # Local use only return elf.SymbolBinding.GLOBAL # FIXME: Should be local, but that breaks the symbols by changing their order relative to reloc table else: return elf.SymbolBinding.GLOBAL def determine_symbol_type(symbol_name: str): if symbol_name.startswith("."): # It's a section return elf.SymbolType.SECTION else: return elf.SymbolType.NONE def make_symbol_table(defined_symbols: dict[str, int], undefined_symbols: list[str], symbol_name_table: bytes, section_index: int) -> elf.SymbolTable: entries: list[elf.Elf32SymbolTableEntry] = [] all_symbol_names: list[str] = [] for symbol_name in defined_symbols.keys(): if symbol_name not in all_symbol_names: entries.append(elf.Elf32SymbolTableEntry(symbol_name_table.index(symbol_name.encode("ascii")+b"\0"), defined_symbols[symbol_name], 0, determine_symbol_type(symbol_name), determine_symbol_binding(symbol_name), 0, section_index)) all_symbol_names.append(symbol_name) for symbol_name in undefined_symbols: if symbol_name not in all_symbol_names: entries.append(elf.Elf32SymbolTableEntry(symbol_name_table.index(symbol_name.encode("ascii")+b"\0"), 0, 0, elf.SymbolType.NONE, elf.SymbolBinding.GLOBAL, 0, 0)) all_symbol_names.append(symbol_name) # All of the local symbols must come first entries.sort(key=lambda s: s.binding==elf.SymbolBinding.LOCAL, reverse=True) entries = [elf.Elf32SymbolTableEntry(0, 0, 0, elf.SymbolType.NONE, elf.SymbolBinding.GLOBAL, 0, 0)] + entries return elf.SymbolTable(entries) def make_relocation_table(relocations: list[x86.Relocation], defined_symbol_names: list[str], symbol_table: elf.SymbolTable) -> elf.RelocationTable: entries: list[elf.RelocationTableEntryWithAddend] = [] for relocation in relocations: symbol_index = 0 for index, symbol_name in enumerate(defined_symbol_names, start=1): if symbol_name == relocation.symbol_name: symbol_index = index continue if relocation.is_relative: relocation_type = elf.X86RelocationType.PC_RELATIVE_32 explicit_addend = -4 else: relocation_type = elf.X86RelocationType.SIMPLE_32 explicit_addend = 0 entries.append(elf.RelocationTableEntryWithAddend(relocation.index, relocation_type, symbol_index, explicit_addend)) return elf.RelocationTable(entries) def make_simple_elf_header(elf_class: elf.ElfClass) -> elf.ElfHeader: return elf.ElfHeader( elf_identifier = elf.ELFIdentifier(elf_class, elf.Endianess.LSB, elf.OSABI.SYSTEM_V), file_type = elf.FileType.RELOCATABLE, target_isa = elf.TargetISA.X64 if elf_class == elf.ElfClass.BITS_64 else elf.TargetISA.X86, entry_point = 0, program_header_offset = 0, section_header_offset = elf.ELF64_HEADER_SIZE if elf_class == elf.ElfClass.BITS_64 else elf.ELF32_HEADER_SIZE, flags = 0, elf_header_size = elf.ELF64_HEADER_SIZE if elf_class == elf.ElfClass.BITS_64 else elf.ELF32_HEADER_SIZE, program_header_entry_size = 0, program_header_count = 0, section_header_entry_size = elf.ELF64_SECTION_HEADER_SIZE if elf_class == elf.ElfClass.BITS_64 else elf.ELF32_SECTION_HEADER_SIZE, section_header_count = 0, section_header_name_index = 0, ) def make_relocatable_elf(relocatable_code: x86.AssembledMachineCode, is_64_bit=False) -> elf.Elf32: file_offset = 0 elf_header = make_simple_elf_header(elf.ElfClass.BITS_64 if is_64_bit else elf.ElfClass.BITS_32) elf_header.section_header_offset = elf_header.elf_header_size elf_header.section_header_count = 6 file_offset += elf_header.elf_header_size null_section_header = elf.Elf32SectionHeader.null() section_names_section_header = elf.Elf32SectionHeader.blank_of_type(elf.Elf32SectionHeaderType.STRING_TABLE) symbol_table_names_section_header = elf.Elf32SectionHeader.blank_of_type(elf.Elf32SectionHeaderType.STRING_TABLE) symbol_table_section_header = elf.Elf32SectionHeader.blank_of_type(elf.Elf32SectionHeaderType.SYMBOL_TABLE) relocation_section_header = elf.Elf32SectionHeader.blank_of_type(elf.Elf32SectionHeaderType.RELOCATABLE) text_section_header = elf.Elf32SectionHeader.blank_of_type(elf.Elf32SectionHeaderType.PROGRAM_DATA) section_names = elf.make_null_terminated_string_table([elf.KnownSectionNames.NULL.value, elf.KnownSectionNames.SECTION_HEADER_STRING_TABLE.value, elf.KnownSectionNames.STRING_TABLE, elf.KnownSectionNames.SYMBOL_TABLE.value, elf.KnownSectionNames.RELOCATION_TEXT.value, elf.KnownSectionNames.TEXT.value]) section_names_section_header.name_index = section_names.index(elf.KnownSectionNames.SECTION_HEADER_STRING_TABLE.value.encode("ascii")) symbol_table_names_section_header.name_index = section_names.index(elf.KnownSectionNames.STRING_TABLE.value.encode("ascii")) symbol_table_section_header.name_index = section_names.index(elf.KnownSectionNames.SYMBOL_TABLE.value.encode("ascii")) relocation_section_header.name_index = section_names.index(elf.KnownSectionNames.RELOCATION_TEXT.value.encode("ascii")) text_section_header.name_index = section_names.index(elf.KnownSectionNames.TEXT.value.encode("ascii")) file_offset += elf_header.section_header_entry_size * 6 section_header_table = elf.Elf32SectionHeaderTable([ null_section_header, section_names_section_header, symbol_table_names_section_header, symbol_table_section_header, relocation_section_header, text_section_header ]) elf_header.section_header_name_index = section_header_table.entries.index(section_names_section_header) relocation_section_header.link_index = section_header_table.entries.index(symbol_table_section_header) relocation_section_header.info = section_header_table.entries.index(text_section_header) text_section_header.flags = elf.SHF_ALLOC | elf.SHF_EXECINSTR undefined_symbol_names = relocatable_code.get_undefined_label_names() all_symbol_names = list(relocatable_code.symbols.keys()) + undefined_symbol_names symbol_name_table_bytes = elf.make_null_terminated_string_table(all_symbol_names) symbol_table = make_symbol_table(relocatable_code.symbols, undefined_symbol_names, symbol_name_table_bytes, 5) symbol_table_section_header.info = symbol_table.get_symbol_index_of_first_nonlocal_symbol() symbol_table_section_header.link_index = section_header_table.entries.index(symbol_table_names_section_header) symbol_table_section_header.entry_size = elf.ELF64_SYMBOL_TABLE_ENTRY_SIZE if elf_header.elf_identifier.elf_class == elf.ElfClass.BITS_64 else elf.ELF32_SYMBOL_TABLE_ENTRY_SIZE relocation_section_header.entry_size = elf.ELF64_RELOCATION_TABLE_ENTRY_SIZE if elf_header.elf_identifier.elf_class == elf.ElfClass.BITS_64 else elf.ELF32_RELOCATION_TABLE_ENTRY_SIZE symbol_table_bytes = elf.symbol_table_to_bytes(symbol_table, elf_header.elf_identifier.elf_class) reloaction_table_bytes = elf.relocation_table_to_bytes(make_relocation_table(relocatable_code.relocations, all_symbol_names, symbol_table), elf_header.elf_identifier.elf_class) section_data = [b"", section_names, symbol_name_table_bytes, symbol_table_bytes, reloaction_table_bytes, relocatable_code.binary] sections: dict[int, bytes] = {} for section_index in range(1, len(section_header_table.entries)): section_header_table.entries[section_index].file_offset = file_offset section_header_table.entries[section_index].file_size = len(section_data[section_index]) sections.update({section_header_table.entries[section_index].file_offset: section_data[section_index]}) file_offset += len(section_data[section_index]) return elf.Elf32(elf_header, elf.Elf32ProgramHeaderTable([]), section_header_table, sections) def compile_to_relocatable_file(relocatable_code: x86.AssembledMachineCode) -> bytes: return bytes(make_relocatable_elf(relocatable_code))