2020-05-15 23:13:02 +01:00
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# Copyright (c) Facebook, Inc. and its affiliates.
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2021-04-03 09:10:35 +01:00
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# SPDX-License-Identifier: GPL-3.0-or-later
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2020-05-15 23:13:02 +01:00
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2019-05-10 07:53:16 +01:00
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import struct
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from typing import Optional, Sequence
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from tests.elf import ET, PT, SHT
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class ElfSection:
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def __init__(
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self,
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data: bytes,
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name: Optional[str] = None,
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sh_type: Optional[SHT] = None,
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p_type: Optional[PT] = None,
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vaddr: int = 0,
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paddr: int = 0,
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memsz: Optional[int] = None,
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p_align: int = 0,
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):
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self.data = data
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self.name = name
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self.sh_type = sh_type
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self.p_type = p_type
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self.vaddr = vaddr
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self.paddr = paddr
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self.memsz = memsz
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self.p_align = p_align
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assert (self.name is not None) or (self.p_type is not None)
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assert (self.name is None) == (self.sh_type is None)
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if self.p_type is None:
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assert self.memsz is None
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elif self.memsz is None:
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self.memsz = len(self.data)
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def create_elf_file(
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type: ET, sections: Sequence[ElfSection], little_endian: bool = True, bits: int = 64
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):
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endian = "<" if little_endian else ">"
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if bits == 64:
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ehdr_struct = struct.Struct(endian + "16BHHIQQQIHHHHHH")
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shdr_struct = struct.Struct(endian + "IIQQQQIIQQ")
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phdr_struct = struct.Struct(endian + "IIQQQQQQ")
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e_machine = 62 if little_endian else 43 # EM_X86_64 or EM_SPARCV9
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else:
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assert bits == 32
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ehdr_struct = struct.Struct(endian + "16BHHIIIIIHHHHHH")
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shdr_struct = struct.Struct(endian + "10I")
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phdr_struct = struct.Struct(endian + "8I")
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e_machine = 3 if little_endian else 8 # EM_386 or EM_MIPS
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2020-08-27 06:15:04 +01:00
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shstrtab = ElfSection(name=".shstrtab", sh_type=SHT.STRTAB, data=bytearray(1))
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2019-05-10 07:53:16 +01:00
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tmp = [shstrtab]
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tmp.extend(sections)
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sections = tmp
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shnum = 1 # One for the SHT_NULL section.
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phnum = 0
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for section in sections:
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if section.name is not None:
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shstrtab.data.extend(section.name.encode())
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shstrtab.data.append(0)
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shnum += 1
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if section.p_type is not None:
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phnum += 1
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shdr_offset = ehdr_struct.size
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phdr_offset = shdr_offset + shdr_struct.size * shnum
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headers_size = phdr_offset + phdr_struct.size * phnum
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buf = bytearray(headers_size)
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ehdr_struct.pack_into(
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buf,
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0,
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0x7F, # ELFMAG0
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ord("E"), # ELFMAG1
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ord("L"), # ELFMAG2
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ord("F"), # ELFMAG3
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2 if bits == 64 else 1, # EI_CLASS = ELFCLASS64 or ELFCLASS32
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1 if little_endian else 2, # EI_DATA = ELFDATA2LSB or ELFDATA2MSB
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1, # EI_VERSION = EV_CURRENT
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0, # EI_OSABI = ELFOSABI_NONE
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0, # EI_ABIVERSION
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0,
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0,
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0,
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0,
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0,
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0,
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0, # EI_PAD
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type, # e_type
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e_machine,
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1, # e_version = EV_CURRENT
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0, # e_entry
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2021-11-19 18:56:45 +00:00
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phdr_offset if phnum else 0, # e_phoff
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2019-05-10 07:53:16 +01:00
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shdr_offset, # e_shoff
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0, # e_flags
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ehdr_struct.size, # e_ehsize
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phdr_struct.size, # e_phentsize
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phnum, # e_phnum
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shdr_struct.size, # e_shentsize,
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shnum, # e_shnum,
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1, # e_shstrndx
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)
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shdr_offset += shdr_struct.size
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for section in sections:
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if section.p_align:
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padding = section.vaddr % section.p_align - len(buf) % section.p_align
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buf.extend(bytes(padding))
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if section.name is not None:
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shdr_struct.pack_into(
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buf,
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shdr_offset,
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shstrtab.data.index(section.name.encode()), # sh_name
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section.sh_type, # sh_type
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0, # sh_flags
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section.vaddr, # sh_addr
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len(buf), # sh_offset
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len(section.data), # sh_size
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0, # sh_link
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0, # sh_info
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1 if section.p_type is None else bits // 8, # sh_addralign
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0, # sh_entsize
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)
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shdr_offset += shdr_struct.size
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if section.p_type is not None:
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flags = 7 # PF_R | PF_W | PF_X
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if bits == 64:
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phdr_struct.pack_into(
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buf,
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phdr_offset,
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section.p_type, # p_type
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flags, # p_flags
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len(buf), # p_offset
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section.vaddr, # p_vaddr
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section.paddr, # p_paddr
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len(section.data), # p_filesz
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section.memsz, # p_memsz
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section.p_align, # p_align
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)
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else:
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phdr_struct.pack_into(
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buf,
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phdr_offset,
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section.p_type, # p_type
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len(buf), # p_offset
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section.vaddr, # p_vaddr
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section.paddr, # p_paddr
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len(section.data), # p_filesz
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section.memsz, # p_memsz
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flags, # p_flags
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section.p_align, # p_align
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)
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phdr_offset += phdr_struct.size
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buf.extend(section.data)
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return buf
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