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#!/usr/bin/env python3
#
# Fixes garbage data between sections and optionally rodata section flags
#
import argparse
from libelf import *
def fix_section_flags(elf):
for section in elf.sections:
# Unset Alloc flag in .rodata section
if section.name == ".rodata":
section.sh_flags &= ~SHF_ALLOC
def fix_garbage(elf, original):
# Begin with the original data, and paste header and section data over it
result = original
if len(original) < len(elf.data):
result.extend([0]*(len(elf.data) - len(original)))
else:
result = result[:len(elf.data)]
# NOTE: This only supports the elf header, program headers, section headers and section data at this time
# emplace elf header
hdr = elf.elf_header.to_bin()
result[0:len(hdr)] = hdr
# emplace program headers
for i,proghdr in enumerate(elf.progheaders):
offset = elf.elf_header.e_phoff + i * elf.elf_header.e_phentsize
result[offset:offset+elf.elf_header.e_phentsize] = proghdr.to_bin()
# emplace section headers and section data
for i,section in enumerate(elf.sections):
offset = elf.elf_header.e_shoff + i * elf.elf_header.e_shentsize
section_header, section_data = section.to_bin()
result[offset:offset+elf.elf_header.e_shentsize] = section_header
if section_data is not None:
result[section.sh_offset:section.sh_offset+section.sh_size] = section_data
return result
def main():
parser = argparse.ArgumentParser(description="Disassemble relocatable ELF object.")
parser.add_argument("compiled", help="path to the compiled ELF file")
parser.add_argument("original", help="path to the original ELF file")
parser.add_argument("--fix-section-flags", help="", action="store_true")
args = parser.parse_args()
elf = None
with open(args.compiled, "rb") as elf_file:
elf = ElfFile(bytearray(elf_file.read()))
original = None
with open(args.original, "rb") as original_file:
original = bytearray(original_file.read())
if args.fix_section_flags:
fix_section_flags(elf)
result_data = fix_garbage(elf, original)
with open(args.compiled, "wb") as elf_file:
elf_file.write(result_data)
if __name__ == '__main__':
main()
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