Given an elf file, show a hex dump of each section along with the relationships between symbols and relocations annotated below each line

elfshow.py

import sys
from elftools.elf.elffile import ELFFile
from elftools.elf.sections import Section, SymbolTableSection, Symbol
from elftools.elf.relocation import RelocationSection, Relocation
from elftools.elf.constants import SH_FLAGS

class RelocSource:
    def __init__(self, target_section_number, symbol_section_number, r):
        self.target_section_number = target_section_number
        self.symbol_section_number = symbol_section_number
        self.r = r
        self.address = None
        self.name = None

class RelocTarget:
    def __init__(self, target_section_number, symbol_section_number, r):
        self.target_section_number = target_section_number
        self.symbol_section_number = symbol_section_number
        self.r = r
        self.address = None
        self.name = None

def annotate_elf(f):
    ef = ELFFile(f)

    symbols = {}

    def add_symbol(s):
        target_section_number = s.entry.st_shndx
        if type(target_section_number) == str:
            return

        target_section = ef.get_section(target_section_number)
        key = (target_section.name, s.entry.st_value)
        res = []
        if key in symbols:
            res = symbols[key]
        res.append(s)
        symbols[key] = res

    def add_reloc_source(r):
        target_section = ef.get_section(r.target_section_number)
        target_symbol_section = ef.get_section(r.symbol_section_number)
        target_symbol_number = r.r.entry['r_info'] >> 8
        target_symbol = target_symbol_section.get_symbol(target_symbol_number)

        if target_symbol.entry.st_shndx == 'SHN_UNDEF':
            return

        target_content_section = ef.get_section(target_symbol.entry.st_shndx)
        r.address = r.r.entry['r_offset']
        addend = r.r.entry['r_addend'] if 'r_addend' in r.r.entry else 0
        r.name = '%s+%x' % (target_symbol.name, addend)
        key = (target_section.name, r.address)
        res = []
        if key in symbols:
            res = symbols[key]
        res.append(r)
        symbols[key] = res

    def add_reloc_target(r):
        target_section = ef.get_section(r.target_section_number)
        target_symbol_section = ef.get_section(r.symbol_section_number)
        target_symbol_number = r.r.entry['r_info'] >> 8
        target_symbol = target_symbol_section.get_symbol(target_symbol_number)

        if target_symbol.entry.st_shndx == 'SHN_UNDEF':
            return

        target_content_section = ef.get_section(target_symbol.entry.st_shndx)
        addend = r.r.entry['r_addend'] if 'r_addend' in r.r.entry else 0
        r.address = target_symbol.entry.st_value + addend
        r.name = '%s+%x' % (target_symbol.name, addend)
        key = (target_content_section.name, r.address)
        res = []
        if key in symbols:
            res = symbols[key]
        res.append(r)
        symbols[key] = res

    for sect in ef.iter_sections():
        if isinstance(sect, SymbolTableSection):
            for s in sect.iter_symbols():
                add_symbol(s)
        elif isinstance(sect, RelocationSection):
            for r in sect.iter_relocations():
                target_section_number = sect.header['sh_info']
                symbol_section_number = sect.header['sh_link']
                add_reloc_source(RelocSource(target_section_number, symbol_section_number, r))
                add_reloc_target(RelocTarget(target_section_number, symbol_section_number, r))

    for sect in ef.iter_sections():
        if sect.header['sh_flags'] & SH_FLAGS.SHF_ALLOC or sect.header['sh_type'] == 'SHT_PROGBITS':
            d = sect.data()
            print(f'section {sect.name}')
            off = 0
            while off <= len(d):
                symbols_this_line = []
                sys.stdout.write('%08x:' % off)
                for i in range(16):
                    if off + i >= len(d):
                        break
                    key = (sect.name, off + i)
                    if key in symbols:
                        symbols_this_line += symbols[key]
                    sys.stdout.write(' %02x' % d[off + i])
                print('')
                if len(symbols_this_line):
                    for s in symbols_this_line:
                        if isinstance(s, Symbol):
                            if len(s.name):
                                print('%08x %s' % (s.entry.st_value, s.name))
                        elif isinstance(s, RelocSource):
                            print('%08x <-%02x %s' % (s.address, s.r['r_info'] & 0xff, s.name))
                        else:
                            print('%08x %02x-> %s' % (s.address, s.r['r_info'] & 0xff, s.name))

                off += 16

if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser()
    parser.add_argument('elffile')

    args = parser.parse_args()
    annotate_elf(open(args.elffile,'rb'))