SymbolLookup.py

'''
SymbolLookup.py
2020-04-19 Jim Fred

Perform symbol lookup using gdb.
Requires a path to gdb and a .elf file  and a list of variable names.
See  __main__ for example usage.
'''
from pygdbmi.gdbcontroller import GdbController # pip install pygdbmi
import re

'''
Class SymbolLookup has a constructor that takes all necessary paramters and creates a dictionary keyed by symbol name 
where values are the address and type.
'''
class SymbolLookup:

    '''
    Class used by SymbolLookup to store symbol addresses and type.
    '''
    class SymbolAddressType:
        def __init__(self, address, type):
            self.address = address
            self.type = type

        def __repr__(self):
            return '({0})0x{1:X}'.format(self.type, self.address)

    '''
    Constructor creates a dictionary.
    '''
    def __init__(self, gdb_exe, target_img, symbol_list):

        # Initial args for gdb.
        gdb_args = [
                    target_img, # target executable.
                    '-batch'    # Causes gdb to exit when done processing initial args.
                ]

        # Append more args to the list of args.
        # These args print the address of symbols.
        for sym in symbol_list:
            gdb_args.append('-ex=p(&{0})'.format(sym))

        # For more robust error checking, print "done" at the end, from gdb to the response list.
        gdb_args.append('--ex=p("done")')

        # Create a gdb object.
        gdbmi = GdbController(
            gdb_path=gdb_exe,
            gdb_args=gdb_args,
            verbose=False###True
        )

        # Lauch gdb and get the response(s).
        responses = gdbmi.get_gdb_response(timeout_sec=2)

        # validate the response based on the length and the last response being  '$3 = "done"' where 3 is the len() of responses.
        if (len(responses) != (len(symbol_list) + 1)  or responses[-1]['payload'] != '${0} = "done"'.format(len(responses))):
            raise Exception('Unexpected response from gdb.')

        del responses[-1] # delete the last element of the responses (containing "done").

        # Compose a dictionary of results, indexed by the symbol name.
        self.symbols = {}

        for eachResponse in responses:
            try:
                response_payload = eachResponse['payload']
                # for a string like '$1 = (float *) 0x20000a64 <HeaterControl::htrCurrentTotal_amps>', parse for 'float *' and  '0x20000a64'.
                reg_exp_match = re.search('\$(\d*?) = \((.*?)\) 0x([0-9A-Fa-f]*) ', response_payload)
                index = int(reg_exp_match.group(1)) - 1
                address = int(reg_exp_match.group(3), 16)
                type = reg_exp_match.group(2)
                ###print('{0}: {1:08X}, {2}'.format(index, address, type))
            except:
                print('Can\'t parse {0}'.format(response_payload))

            # Add this response to the dictionary.
            self.symbols[symbol_list[index]] = SymbolLookup.SymbolAddressType(address, type)

        # self.symbols should now be complete.
        return

'''
Test the usage of SymbolLookup.
'''
if __name__ == "__main__":

    symbol_lookup = SymbolLookup(
      gdb_exe = './resources/gdb.exe',
      target_img = './resources/HeaterControllerCondensationMitigation.out',
      symbol_list=[
          'HeaterControl::heaterDat[0].on',
          'HeaterControl::heaterDat[3].on',
          'main',
          'exit'
      ]
    )

    for symbol_name, symbol_info in symbol_lookup.symbols.items():
        print('{0} is ({1}) at 0x{2:X}'.format(symbol_name, symbol_info.type, symbol_info.address))

# eof.