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Diffstat (limited to 'scripts/tst-elf-edit.py')
| -rw-r--r-- | scripts/tst-elf-edit.py | 206 |
1 files changed, 206 insertions, 0 deletions
diff --git a/scripts/tst-elf-edit.py b/scripts/tst-elf-edit.py new file mode 100644 index 0000000000..a514179bbf --- /dev/null +++ b/scripts/tst-elf-edit.py @@ -0,0 +1,206 @@ +#!/usr/bin/python3 +# ELF editor for load align tests. +# Copyright (C) 2022 Free Software Foundation, Inc. +# Copyright The GNU Toolchain Authors. +# This file is part of the GNU C Library. +# +# The GNU C Library is free software; you can redistribute it and/or +# modify it under the terms of the GNU Lesser General Public +# License as published by the Free Software Foundation; either +# version 2.1 of the License, or (at your option) any later version. +# +# The GNU C Library is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +# Lesser General Public License for more details. +# +# You should have received a copy of the GNU Lesser General Public +# License along with the GNU C Library; if not, see +# <https://www.gnu.org/licenses/>. + +import argparse +import os +import sys +import struct + +EI_NIDENT=16 + +EI_MAG0=0 +ELFMAG0=b'\x7f' +EI_MAG1=1 +ELFMAG1=b'E' +EI_MAG2=2 +ELFMAG2=b'L' +EI_MAG3=3 +ELFMAG3=b'F' + +EI_CLASS=4 +ELFCLASSNONE=b'0' +ELFCLASS32=b'\x01' +ELFCLASS64=b'\x02' + +EI_DATA=5 +ELFDATA2LSB=b'\x01' +ELFDATA2MSB=b'\x02' + +ET_DYN=3 + +PT_LOAD=1 + +def elf_types_fmts(e_ident): + endian = '<' if e_ident[EI_DATA] == ELFDATA2LSB else '>' + addr = 'I' if e_ident[EI_CLASS] == ELFCLASS32 else 'Q' + off = 'I' if e_ident[EI_CLASS] == ELFCLASS32 else 'Q' + return (endian, addr, off) + +class Elf_Ehdr: + def __init__(self, e_ident): + endian, addr, off = elf_types_fmts(e_ident) + self.fmt = '{0}HHI{1}{2}{2}IHHHHHH'.format(endian, addr, off) + self.len = struct.calcsize(self.fmt) + + def read(self, f): + buf = f.read(self.len) + if not buf: + error('{}: header too small'.format(f.name)) + data = struct.unpack(self.fmt, buf) + self.e_type = data[0] + self.e_machine = data[1] + self.e_version = data[2] + self.e_entry = data[3] + self.e_phoff = data[4] + self.e_shoff = data[5] + self.e_flags = data[6] + self.e_ehsize = data[7] + self.e_phentsize= data[8] + self.e_phnum = data[9] + self.e_shstrndx = data[10] + + +class Elf_Phdr: + def __init__(self, e_ident): + endian, addr, off = elf_types_fmts(e_ident) + self.ei_class = e_ident[EI_CLASS] + if self.ei_class == ELFCLASS32: + self.fmt = '{0}I{2}{1}{1}IIII'.format(endian, addr, off) + else: + self.fmt = '{0}II{2}{1}{1}QQQ'.format(endian, addr, off) + self.len = struct.calcsize(self.fmt) + + def read(self, f): + buf = f.read(self.len) + if len(buf) < self.len: + error('{}: program header too small'.format(f.name)) + data = struct.unpack(self.fmt, buf) + if self.ei_class == ELFCLASS32: + self.p_type = data[0] + self.p_offset = data[1] + self.p_vaddr = data[2] + self.p_paddr = data[3] + self.p_filesz = data[4] + self.p_memsz = data[5] + self.p_flags = data[6] + self.p_align = data[7] + else: + self.p_type = data[0] + self.p_flags = data[1] + self.p_offset = data[2] + self.p_vaddr = data[3] + self.p_paddr = data[4] + self.p_filesz = data[5] + self.p_memsz = data[6] + self.p_align = data[7] + + def write(self, f): + if self.ei_class == ELFCLASS32: + data = struct.pack(self.fmt, + self.p_type, + self.p_offset, + self.p_vaddr, + self.p_paddr, + self.p_filesz, + self.p_memsz, + self.p_flags, + self.p_align) + else: + data = struct.pack(self.fmt, + self.p_type, + self.p_flags, + self.p_offset, + self.p_vaddr, + self.p_paddr, + self.p_filesz, + self.p_memsz, + self.p_align) + f.write(data) + + +def error(msg): + print(msg, file=sys.stderr) + sys.exit(1) + + +def elf_edit_align(phdr, align): + if align == 'half': + phdr.p_align = phdr.p_align >> 1 + else: + phdr.p_align = int(align) + + +def elf_edit(f, align): + ei_nident_fmt = 'c' * EI_NIDENT + ei_nident_len = struct.calcsize(ei_nident_fmt) + + data = f.read(ei_nident_len) + if len(data) < ei_nident_len: + error('{}: e_nident too small'.format(f.name)) + e_ident = struct.unpack(ei_nident_fmt, data) + + if e_ident[EI_MAG0] != ELFMAG0 \ + or e_ident[EI_MAG1] != ELFMAG1 \ + or e_ident[EI_MAG2] != ELFMAG2 \ + or e_ident[EI_MAG3] != ELFMAG3: + error('{}: bad ELF header'.format(f.name)) + + if e_ident[EI_CLASS] != ELFCLASS32 \ + and e_ident[EI_CLASS] != ELFCLASS64: + error('{}: unsupported ELF class: {}'.format(f.name, e_ident[EI_CLASS])) + + if e_ident[EI_DATA] != ELFDATA2LSB \ + and e_ident[EI_DATA] != ELFDATA2MSB: \ + error('{}: unsupported ELF data: {}'.format(f.name, e_ident[EI_DATA])) + + ehdr = Elf_Ehdr(e_ident) + ehdr.read(f) + if ehdr.e_type != ET_DYN: + error('{}: not a shared library'.format(f.name)) + + phdr = Elf_Phdr(e_ident) + for i in range(0, ehdr.e_phnum): + f.seek(ehdr.e_phoff + i * phdr.len) + phdr.read(f) + if phdr.p_type == PT_LOAD: + elf_edit_align(phdr, align) + f.seek(ehdr.e_phoff + i * phdr.len) + phdr.write(f) + break + + +def get_parser(): + parser = argparse.ArgumentParser(description=__doc__) + parser.add_argument('-a', dest='align', required=True, + help='How to set the LOAD alignment') + parser.add_argument('output', + help='ELF file to edit') + return parser + + +def main(argv): + parser = get_parser() + opts = parser.parse_args(argv) + with open(opts.output, 'r+b') as fout: + elf_edit(fout, opts.align) + + +if __name__ == '__main__': + main(sys.argv[1:]) |