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78 lines
4.8 KiB
78 lines
4.8 KiB
import struct, ctypes, ctypes.util
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from dataclasses import dataclass
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from tinygrad.helpers import getbits, i2u, unwrap
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from tinygrad.runtime.autogen import 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 link_sym(sym:str, libs:list[str]) -> int:
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for lib in libs:
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try: return unwrap(ctypes.cast(getattr(ctypes.CDLL(ctypes.util.find_library(lib)), sym), ctypes.c_void_p).value)
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except (OSError, AttributeError): pass
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raise RuntimeError(f'Attempting to relocate against an undefined symbol {sym}')
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def elf_loader(blob:bytes, force_section_align:int=1, link_libs:list[str]|None=None) -> 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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if trgt_sh_name == ".eh_frame": continue
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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, link_sym(_strtab(sh_strtab, sym.st_name), link_libs or []) if sym.st_shndx == 0 else
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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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def jit_loader(obj: bytes, base:int=0, link_libs:list[str]|None=None) -> bytes:
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image_, _, relocs = elf_loader(obj, link_libs=link_libs)
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image = bytearray(image_)
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def relocate(instr: int, base: int, ploc: int, tgt: int, r_type: int):
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match r_type:
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# https://refspecs.linuxfoundation.org/elf/x86_64-abi-0.95.pdf
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case libc.R_X86_64_PC32: return i2u(32, tgt-ploc)
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case libc.R_X86_64_PLT32: return i2u(32, tgt-ploc-base)
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# https://github.com/ARM-software/abi-aa/blob/main/aaelf64/aaelf64.rst for definitions of relocations
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# https://www.scs.stanford.edu/~zyedidia/arm64/index.html for instruction encodings
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case libc.R_AARCH64_ADR_PREL_PG_HI21:
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rel_pg = (tgt & ~0xFFF) - (ploc & ~0xFFF)
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return instr | (getbits(rel_pg, 12, 13) << 29) | (getbits(rel_pg, 14, 32) << 5)
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case libc.R_AARCH64_ADD_ABS_LO12_NC: return instr | (getbits(tgt, 0, 11) << 10)
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case libc.R_AARCH64_LDST16_ABS_LO12_NC: return instr | (getbits(tgt, 1, 11) << 10)
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case libc.R_AARCH64_LDST32_ABS_LO12_NC: return instr | (getbits(tgt, 2, 11) << 10)
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case libc.R_AARCH64_LDST64_ABS_LO12_NC: return instr | (getbits(tgt, 3, 11) << 10)
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case libc.R_AARCH64_LDST128_ABS_LO12_NC: return instr | (getbits(tgt, 4, 11) << 10)
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case libc.R_AARCH64_CALL26:
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if -(2**25) <= tgt-ploc-base and tgt-ploc-base <= (2**25 - 1) * 4: return instr | getbits(tgt-ploc-base, 2, 27)
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nonlocal image
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# create trampoline: LDR x17, 8 BR x17
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image += struct.pack("<IIQ", 0x58000051, 0xD61F0220, tgt)
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return instr | getbits(len(image)-ploc-16, 2, 27)
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raise NotImplementedError(f"Encountered unknown relocation type {r_type}")
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# This is needed because we have an object file, not a .so that has all internal references (like loads of constants from .rodata) resolved.
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for ploc,tgt,r_type,r_addend in relocs:
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image[ploc:ploc+4] = struct.pack("<I", relocate(struct.unpack("<I", image[ploc:ploc+4])[0], base, ploc, tgt+r_addend, r_type))
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return bytes(image)
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