firmware/saleae-logic16/parseelf.py

   1 #!/usr/bin/python3
   2 ##
   3 ## This file is part of the sigrok-util project.
   4 ##
   5 ## Copyright (C) 2013 Marcus Comstedt <marcus@mc.pp.se>
   6 ##
   7 ## This program is free software; you can redistribute it and/or modify
   8 ## it under the terms of the GNU General Public License as published by
   9 ## the Free Software Foundation; either version 3 of the License, or
  10 ## (at your option) any later version.
  11 ##
  12 ## This program is distributed in the hope that it will be useful,
  13 ## but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 ## GNU General Public License for more details.
  16 ##
  17 ## You should have received a copy of the GNU General Public License
  18 ## along with this program; if not, see <http://www.gnu.org/licenses/>.
  19 ##
  20
  21 import struct
  22
  23 class elf:
  24
  25     def read_struct(this, struct_fmt, struct_fields):
  26         fmt = this.elf_endianprefix+str.translate(struct_fmt, this.elf_format);
  27         fields = struct.unpack(fmt, this.file.read(struct.calcsize(fmt)))
  28         return dict(zip(struct_fields, fields))
  29
  30     def read_ehdr(this):
  31         return this.read_struct('16sHHWNNNWHHHHHH',
  32                                 ('e_ident', 'e_type', 'e_machine', 'e_version',
  33                                  'e_entry', 'e_phoff', 'e_shoff', 'e_flags',
  34                                  'e_ehsize', 'e_phentsize', 'e_phnum',
  35                                  'e_shentsize', 'e_shnum', 'e_shstrndx'))
  36
  37     def read_shdr(this):
  38         return this.read_struct('WWNNNNWWNN',
  39                                 ('sh_name', 'sh_type', 'sh_flags', 'sh_addr',
  40                                  'sh_offset', 'sh_size', 'sh_link', 'sh_info',
  41                                  'sh_addralign', 'sh_entsize'))
  42
  43     def read_section(this, shdr):
  44         this.file.seek(shdr['sh_offset'])
  45         return this.file.read(shdr['sh_size'])
  46
  47     def get_name(this, name, strtab=None):
  48         strtab = strtab or this.strtab
  49         nul = strtab.find(b'\0', name)
  50         if nul < 0:
  51             return bytes.decode(strtab[name:])
  52         else:
  53             return bytes.decode(strtab[name:nul])
  54
  55     def find_section(this, name):
  56         for section in this.shdrs:
  57             if this.get_name(section['sh_name']) == name:
  58                 return section
  59         raise KeyError(name)
  60
  61     def parse_symbol(this):
  62         if this.elf_wordsize == 64:
  63             return this.read_struct('WBBHNX',
  64                                     ('st_name', 'st_info', 'st_other',
  65                                      'st_shndx', 'st_value', 'st_size'))
  66         else:
  67             return this.read_struct('WNWBBH',
  68                                     ('st_name', 'st_value', 'st_size',
  69                                      'st_info', 'st_other', 'st_shndx'))
  70
  71     def parse_rela(this):
  72         return this.read_struct('NNn', ('r_offset', 'r_info', 'r_addend'))
  73
  74     def parse_rel(this):
  75         return this.read_struct('NN', ('r_offset', 'r_info'))
  76
  77     def fixup_reloc(this, reloc):
  78         if not 'r_addend' in reloc:
  79             reloc['r_addend'] = 0
  80         if this.elf_wordsize == 64:
  81             reloc['r_sym'] = reloc['r_info'] >> 32
  82             reloc['r_type'] = reloc['r_info'] & 0xffffffff
  83         else:
  84             reloc['r_sym'] = reloc['r_info'] >> 8
  85             reloc['r_type'] = reloc['r_info'] & 0xff
  86         return reloc
  87
  88     def parse_symbols(this, symsecname, strsecname):
  89         try:
  90             symsechdr = this.find_section(symsecname)
  91             strsechdr = this.find_section(strsecname)
  92         except KeyError:
  93             return {}
  94         strsec = this.read_section(strsechdr)
  95         this.file.seek(symsechdr['sh_offset'])
  96         syms = [dict(this.parse_symbol(),number=i) for i in
  97                 range(0, symsechdr['sh_size'] // symsechdr['sh_entsize'])]
  98         return {this.get_name(sym['st_name'], strsec): sym for sym in syms}
  99
 100     def parse_relocs(this, section):
 101         this.file.seek(section['sh_offset'])
 102         if section['sh_type'] == 4:
 103             relocs = [this.fixup_reloc(this.parse_rela()) for i in
 104                       range(0, section['sh_size'] // section['sh_entsize'])]
 105         else:
 106             relocs = [this.fixup_reloc(this.parse_rel()) for i in
 107                       range(0, section['sh_size'] // section['sh_entsize'])]
 108         return relocs
 109
 110     def address_to_offset(this, addr):
 111         for section in this.shdrs:
 112             if (section['sh_addr'] <= addr and
 113                 section['sh_addr']+section['sh_size'] > addr):
 114                 return section['sh_offset']+(addr-section['sh_addr'])
 115         raise IndexError('address out of range')
 116
 117     def load_symbol(this, sym):
 118         this.file.seek(this.address_to_offset(sym['st_value']))
 119         return this.file.read(sym['st_size'])
 120
 121     def __init__(this, filename):
 122         this.file = open(filename, 'rb')
 123         magic = this.file.read(16)
 124
 125         if magic[:4] != b'\x7fELF':
 126             raise Exception("ELF signature not found")
 127
 128         if magic[4] == 1:
 129             this.elf_wordsize = 32
 130             nativeint = 'Ii'
 131         elif magic[4] == 2:
 132             this.elf_wordsize = 64
 133             nativeint = 'Qq'
 134         else:
 135             raise Exception("Invalid ELF file class")
 136
 137         if magic[5] == 1:
 138             this.elf_endianprefix = '<'
 139         elif magic[5] == 2:
 140             this.elf_endianprefix = '>'
 141         else:
 142             raise Exception("Invalid ELF data encoding")
 143
 144         this.elf_format = str.maketrans('HWwXxNn', 'HIiQq'+nativeint)
 145
 146         this.file.seek(0)
 147         this.ehdr = this.read_ehdr()
 148         this.file.seek(this.ehdr['e_shoff'])
 149         this.shdrs = [this.read_shdr() for i in range(this.ehdr['e_shnum'])]
 150
 151         this.strtab = this.read_section(this.shdrs[this.ehdr['e_shstrndx']])
 152
 153         this.symtab = this.parse_symbols('.symtab', '.strtab')
 154         this.dynsym = this.parse_symbols('.dynsym', '.dynstr')
 155
 156         this.relocs = {}
 157         for section in this.shdrs:
 158             if section['sh_type'] == 4 or section['sh_type'] == 9:
 159                 rels = {}
 160                 symsec = this.shdrs[section['sh_link']]
 161                 if this.get_name(symsec['sh_name']) == '.symtab':
 162                     rels['symbols'] = this.symtab
 163                 elif this.get_name(symsec['sh_name']) == '.dynsym':
 164                     rels['symbols'] = this.dynsym
 165                 rels['relocs'] = this.parse_relocs(section)
 166                 this.relocs[this.get_name(section['sh_name'])] = rels
 167
 168     def __del__(this):
 169         try:
 170             this.file.close()
 171         except AttributeError:
 172             pass