227 lines
6.9 KiB
Python
227 lines
6.9 KiB
Python
#!/usr/bin/python3
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# ELF editor for load align tests.
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# Copyright (C) 2022 Free Software Foundation, Inc.
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# Copyright The GNU Toolchain Authors.
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# This file is part of the GNU C Library.
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#
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# The GNU C Library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# The GNU C Library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with the GNU C Library; if not, see
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# <https://www.gnu.org/licenses/>.
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import argparse
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import os
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import sys
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import struct
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EI_NIDENT=16
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EI_MAG0=0
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ELFMAG0=b'\x7f'
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EI_MAG1=1
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ELFMAG1=b'E'
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EI_MAG2=2
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ELFMAG2=b'L'
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EI_MAG3=3
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ELFMAG3=b'F'
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EI_CLASS=4
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ELFCLASSNONE=b'0'
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ELFCLASS32=b'\x01'
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ELFCLASS64=b'\x02'
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EI_DATA=5
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ELFDATA2LSB=b'\x01'
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ELFDATA2MSB=b'\x02'
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ET_EXEC=2
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ET_DYN=3
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PT_LOAD=1
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PT_TLS=7
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def elf_types_fmts(e_ident):
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endian = '<' if e_ident[EI_DATA] == ELFDATA2LSB else '>'
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addr = 'I' if e_ident[EI_CLASS] == ELFCLASS32 else 'Q'
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off = 'I' if e_ident[EI_CLASS] == ELFCLASS32 else 'Q'
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return (endian, addr, off)
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class Elf_Ehdr:
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def __init__(self, e_ident):
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endian, addr, off = elf_types_fmts(e_ident)
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self.fmt = '{0}HHI{1}{2}{2}IHHHHHH'.format(endian, addr, off)
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self.len = struct.calcsize(self.fmt)
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def read(self, f):
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buf = f.read(self.len)
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if not buf:
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error('{}: header too small'.format(f.name))
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data = struct.unpack(self.fmt, buf)
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self.e_type = data[0]
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self.e_machine = data[1]
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self.e_version = data[2]
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self.e_entry = data[3]
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self.e_phoff = data[4]
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self.e_shoff = data[5]
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self.e_flags = data[6]
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self.e_ehsize = data[7]
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self.e_phentsize= data[8]
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self.e_phnum = data[9]
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self.e_shstrndx = data[10]
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class Elf_Phdr:
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def __init__(self, e_ident):
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endian, addr, off = elf_types_fmts(e_ident)
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self.ei_class = e_ident[EI_CLASS]
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if self.ei_class == ELFCLASS32:
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self.fmt = '{0}I{2}{1}{1}IIII'.format(endian, addr, off)
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else:
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self.fmt = '{0}II{2}{1}{1}QQQ'.format(endian, addr, off)
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self.len = struct.calcsize(self.fmt)
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def read(self, f):
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buf = f.read(self.len)
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if len(buf) < self.len:
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error('{}: program header too small'.format(f.name))
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data = struct.unpack(self.fmt, buf)
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if self.ei_class == ELFCLASS32:
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self.p_type = data[0]
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self.p_offset = data[1]
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self.p_vaddr = data[2]
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self.p_paddr = data[3]
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self.p_filesz = data[4]
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self.p_memsz = data[5]
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self.p_flags = data[6]
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self.p_align = data[7]
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else:
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self.p_type = data[0]
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self.p_flags = data[1]
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self.p_offset = data[2]
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self.p_vaddr = data[3]
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self.p_paddr = data[4]
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self.p_filesz = data[5]
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self.p_memsz = data[6]
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self.p_align = data[7]
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def write(self, f):
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if self.ei_class == ELFCLASS32:
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data = struct.pack(self.fmt,
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self.p_type,
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self.p_offset,
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self.p_vaddr,
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self.p_paddr,
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self.p_filesz,
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self.p_memsz,
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self.p_flags,
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self.p_align)
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else:
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data = struct.pack(self.fmt,
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self.p_type,
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self.p_flags,
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self.p_offset,
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self.p_vaddr,
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self.p_paddr,
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self.p_filesz,
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self.p_memsz,
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self.p_align)
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f.write(data)
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def error(msg):
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print(msg, file=sys.stderr)
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sys.exit(1)
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def elf_edit_align(phdr, align):
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if align == 'half':
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phdr.p_align = phdr.p_align >> 1
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else:
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phdr.p_align = int(align)
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def elf_edit_maximize_tls_size(phdr, elfclass):
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if elfclass == ELFCLASS32:
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# It is possible that the kernel can allocate half of the
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# address space, so use something larger.
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phdr.p_memsz = 0xfff00000
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else:
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phdr.p_memsz = 1 << 63
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def elf_edit(f, opts):
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ei_nident_fmt = 'c' * EI_NIDENT
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ei_nident_len = struct.calcsize(ei_nident_fmt)
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data = f.read(ei_nident_len)
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if len(data) < ei_nident_len:
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error('{}: e_nident too small'.format(f.name))
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e_ident = struct.unpack(ei_nident_fmt, data)
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if e_ident[EI_MAG0] != ELFMAG0 \
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or e_ident[EI_MAG1] != ELFMAG1 \
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or e_ident[EI_MAG2] != ELFMAG2 \
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or e_ident[EI_MAG3] != ELFMAG3:
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error('{}: bad ELF header'.format(f.name))
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if e_ident[EI_CLASS] != ELFCLASS32 \
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and e_ident[EI_CLASS] != ELFCLASS64:
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error('{}: unsupported ELF class: {}'.format(f.name, e_ident[EI_CLASS]))
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if e_ident[EI_DATA] != ELFDATA2LSB \
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and e_ident[EI_DATA] != ELFDATA2MSB: \
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error('{}: unsupported ELF data: {}'.format(f.name, e_ident[EI_DATA]))
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ehdr = Elf_Ehdr(e_ident)
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ehdr.read(f)
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if ehdr.e_type not in (ET_EXEC, ET_DYN):
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error('{}: not an executable or shared library'.format(f.name))
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phdr = Elf_Phdr(e_ident)
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maximize_tls_size_done = False
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for i in range(0, ehdr.e_phnum):
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f.seek(ehdr.e_phoff + i * phdr.len)
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phdr.read(f)
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if phdr.p_type == PT_LOAD and opts.align is not None:
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elf_edit_align(phdr, opts.align)
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f.seek(ehdr.e_phoff + i * phdr.len)
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phdr.write(f)
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break
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if phdr.p_type == PT_TLS and opts.maximize_tls_size:
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elf_edit_maximize_tls_size(phdr, e_ident[EI_CLASS])
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f.seek(ehdr.e_phoff + i * phdr.len)
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phdr.write(f)
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maximize_tls_size_done = True
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break
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if opts.maximize_tls_size and not maximize_tls_size_done:
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error('{}: TLS maximum size was not updated'.format(f.name))
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def get_parser():
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parser = argparse.ArgumentParser(description=__doc__)
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parser.add_argument('-a', dest='align',
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help='How to set the LOAD alignment')
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parser.add_argument('--maximize-tls-size', action='store_true',
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help='Set maximum PT_TLS size')
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parser.add_argument('output',
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help='ELF file to edit')
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return parser
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def main(argv):
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parser = get_parser()
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opts = parser.parse_args(argv)
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with open(opts.output, 'r+b') as fout:
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elf_edit(fout, opts)
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if __name__ == '__main__':
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main(sys.argv[1:])
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