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37 lines
2.3 KiB
37 lines
2.3 KiB
1 month ago
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from dataclasses import dataclass
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import tinygrad.runtime.autogen.libc as libc
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@dataclass(frozen=True)
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class ElfSection: name:str; header:libc.Elf64_Shdr; content:bytes # noqa: E702
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def elf_loader(blob:bytes, force_section_align:int=1) -> tuple[memoryview, list[ElfSection], list[tuple]]:
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def _strtab(blob: bytes, idx: int) -> str: return blob[idx:blob.find(b'\x00', idx)].decode('utf-8')
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header = libc.Elf64_Ehdr.from_buffer_copy(blob)
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section_headers = (libc.Elf64_Shdr * header.e_shnum).from_buffer_copy(blob[header.e_shoff:])
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sh_strtab = blob[(shstrst:=section_headers[header.e_shstrndx].sh_offset):shstrst+section_headers[header.e_shstrndx].sh_size]
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sections = [ElfSection(_strtab(sh_strtab, sh.sh_name), sh, blob[sh.sh_offset:sh.sh_offset+sh.sh_size]) for sh in section_headers]
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def _to_carray(sh, ctype): return (ctype * (sh.header.sh_size // sh.header.sh_entsize)).from_buffer_copy(sh.content)
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rel = [(sh, sh.name[4:], _to_carray(sh, libc.Elf64_Rel)) for sh in sections if sh.header.sh_type == libc.SHT_REL]
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rela = [(sh, sh.name[5:], _to_carray(sh, libc.Elf64_Rela)) for sh in sections if sh.header.sh_type == libc.SHT_RELA]
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symtab = [_to_carray(sh, libc.Elf64_Sym) for sh in sections if sh.header.sh_type == libc.SHT_SYMTAB][0]
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progbits = [sh for sh in sections if sh.header.sh_type == libc.SHT_PROGBITS]
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# Prealloc image for all fixed addresses.
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image = bytearray(max([sh.header.sh_addr + sh.header.sh_size for sh in progbits if sh.header.sh_addr != 0] + [0]))
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for sh in progbits:
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if sh.header.sh_addr != 0: image[sh.header.sh_addr:sh.header.sh_addr+sh.header.sh_size] = sh.content
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else:
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image += b'\0' * (((align:=max(sh.header.sh_addralign, force_section_align)) - len(image) % align) % align) + sh.content
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sh.header.sh_addr = len(image) - len(sh.content)
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# Relocations
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relocs = []
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for sh, trgt_sh_name, c_rels in rel + rela:
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target_image_off = next(tsh for tsh in sections if tsh.name == trgt_sh_name).header.sh_addr
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rels = [(r.r_offset, symtab[libc.ELF64_R_SYM(r.r_info)], libc.ELF64_R_TYPE(r.r_info), getattr(r, "r_addend", 0)) for r in c_rels]
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relocs += [(target_image_off + roff, sections[sym.st_shndx].header.sh_addr + sym.st_value, rtype, raddend) for roff, sym, rtype, raddend in rels]
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return memoryview(image), sections, relocs
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