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gdbmi.py 10.50 KiB
# Copyright (c) 2013-2017, The Linux Foundation. All rights reserved.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 and
# only version 2 as published by the Free Software Foundation.
#
# This program 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 General Public License for more details.
import sys
import re
import subprocess
import module_table
from print_out import print_out_str
GDB_SENTINEL = '(gdb) '
GDB_DATA_LINE = '~'
GDB_OOB_LINE = '^'
def gdb_hex_to_dec(val):
match = re.search('(0x[0-9a-fA-F]+)', val)
return int(match.group(1), 16)
class GdbSymbol(object):
def __init__(self, symbol, section, addr):
self.symbol = symbol
self.section = section
self.addr = addr
class GdbMIResult(object):
def __init__(self, lines, oob_lines):
self.lines = lines
self.oob_lines = oob_lines
class GdbMIException(Exception):
def __init__(self, *args):
self.value = '\n *** '.join([str(i) for i in args])
def __str__(self):
return self.value
class GdbMI(object):
"""Interface to the ``gdbmi`` subprocess. This should generally be
used as a context manager (using Python's ``with`` statement),
like so::
>>> with GdbMI(gdb_path, elf) as g:
print('GDB Version: ' + g.version())
"""
def __init__(self, gdb_path, elf, kaslr_offset=0):
self.gdb_path = gdb_path
self.elf = elf
self.kaslr_offset = kaslr_offset
self._cache = {}
self._gdbmi = None
self.mod_table = None
def open(self):
"""Open the connection to the ``gdbmi`` backend. Not needed if using
``gdbmi`` as a context manager (recommended).
"""
self._gdbmi = subprocess.Popen(
[self.gdb_path, '--interpreter=mi2', self.elf],
stdin=subprocess.PIPE,
stdout=subprocess.PIPE
)
self._flush_gdbmi()
def close(self):
"""Close the connection to the ``gdbmi`` backend. Not needed if using
``gdbmi`` as a context manager (recommended).
"""
self._gdbmi.communicate('quit')
def __enter__(self):
self.open()
return self
def __exit__(self, ex_type, ex_value, ex_traceback):
self.close()
def _flush_gdbmi(self):
while True:
line = self._gdbmi.stdout.readline().rstrip('\r\n')
if line == GDB_SENTINEL:
break
def setup_module_table(self, module_table):
self.mod_table = module_table
d = {"\\":"\\\\"}
for mod_tbl_ent in self.mod_table.module_table:
load_mod_sym_cmd = 'add-symbol-file %s 0x%x' % (mod_tbl_ent.get_sym_path(), mod_tbl_ent.module_offset)
gdb_cmd = ''.join(d.get(c, c) for c in load_mod_sym_cmd)
self._run(gdb_cmd)
def _run(self, cmd, skip_cache=False, save_in_cache=True):
"""Runs a gdb command and returns a GdbMIResult of the result. Results
are cached (unless skip_cache=True) for quick future lookups.
- cmd: Command to run (e.g. "show version")
- skip_cache: Don't use a previously cached result
- save_in_cache: Whether we should save this result in the cache
"""
if self._gdbmi is None:
raise Exception(
'BUG: GdbMI not initialized. ' +
'Please use GdbMI.open or a context manager.')
if not skip_cache:
if cmd in self._cache:
return GdbMIResult(self._cache[cmd], [])
self._gdbmi.stdin.write(cmd.rstrip('\n') + '\n')
self._gdbmi.stdin.flush()
output = []
oob_output = []
while True:
line = self._gdbmi.stdout.readline().rstrip('\r\n')
if line == GDB_SENTINEL:
break
if line.startswith(GDB_DATA_LINE):
# strip the leading "~"
line = line[1:]
# strip the leading and trailing "
line = line[1:-1]
# strip any trailing (possibly escaped) newlines
if line.endswith('\\n'):
line = line[:-2]
elif line.endswith('\n'):
line = line.rstrip('\n')
output.append(line)
if line.startswith(GDB_OOB_LINE):
oob_output.append(line[1:])
if save_in_cache:
self._cache[cmd] = output
return GdbMIResult(output, oob_output)
def _run_for_one(self, cmd):
result = self._run(cmd)
if len(result.lines) != 1:
raise GdbMIException(
cmd, '\n'.join(result.lines + result.oob_lines))
return result.lines[0]
def _run_for_first(self, cmd):
return self._run(cmd).lines[0]
def version(self):
"""Return GDB version"""
return self._run_for_first('show version')
def field_offset(self, the_type, field):
"""Returns the offset of a field in a struct or type.
Example:
>>> gdbmi.field_offset("struct ion_buffer", "heap")
20
``the_type``
struct or type (note that if it's a struct you should
include the word ``"struct"`` (e.g.: ``"struct
ion_buffer"``))
``field``
the field whose offset we want to return
"""
cmd = 'print /x (int)&(({0} *)0)->{1}'.format(the_type, field)
result = self._run_for_one(cmd)
return gdb_hex_to_dec(result)
def container_of(self, ptr, the_type, member):
"""Like ``container_of`` from the kernel."""
return ptr - self.field_offset(the_type, member)
def sibling_field_addr(self, ptr, parent_type, member, sibling):
"""Returns the address of a sibling field within the parent
structure.
Example:
Given a dump containing an instance of the following struct::
struct pizza {
int price;
int qty;
};
If you have a pointer to qty, you can get a pointer to price with:
>>> addr = sibling_field_addr(qty, 'struct pizza', 'qty', 'price')
>>> price = dump.read_int(addr)
>>> price
10
"""
return self.container_of(ptr, parent_type, member) + \
self.field_offset(parent_type, sibling)
def sizeof(self, the_type):
"""Returns the size of the type specified by ``the_type``."""
result = self._run_for_one('print /x sizeof({0})'.format(the_type))
return gdb_hex_to_dec(result)
def address_of(self, symbol):
"""Returns the address of the specified symbol.
>>> hex(dump.address_of('linux_banner'))
'0xc0b0006a'
"""
result = self._run_for_one('print /x &{0}'.format(symbol))
return int(result.split(' ')[-1], 16) + self.kaslr_offset
def get_symbol_info(self, address):
"""Returns a GdbSymbol representing the nearest symbol found at
``address``."""
result = self._run_for_one('info symbol ' + hex(address))
parts = result.split(' ')
if len(parts) < 2:
raise GdbMIException('Output looks bogus...', result)
symbol = parts[0]
section = parts[-1]
return GdbSymbol(symbol, section, address)
def symbol_at(self, address):
"""Get the symbol at the given address (using ``get_symbol_info``)"""
return self.get_symbol_info(address).symbol
def get_enum_lookup_table(self, enum, upperbound):
"""Return a table translating enum values to human readable
strings.
>>> dump.gdbmi.get_enum_lookup_table('ion_heap_type', 10)
['ION_HEAP_TYPE_SYSTEM',
'ION_HEAP_TYPE_SYSTEM_CONTIG',
'ION_HEAP_TYPE_CARVEOUT',
'ION_HEAP_TYPE_CHUNK',
'ION_HEAP_TYPE_CUSTOM',
'ION_NUM_HEAPS',
'6',
'7',
'8',
'9']
"""
table = []
for i in range(0, upperbound):
result = self._run_for_first(
'print ((enum {0}){1})'.format(enum, i))
parts = result.split(' ')
if len(parts) < 3:
raise GdbMIException(
"can't parse enum {0} {1}\n".format(enum, i), result)
table.append(parts[2].rstrip())
return table
def get_func_info(self, address):
"""Returns the function info at a particular address, specifically
line and file.
>>> dump.gdbmi.get_func_info(dump.gdbmi.address_of('panic'))
'Line 78 of \\"kernel/kernel/panic.c\\"'
"""
result = self._run_for_one('info line *0x{0:x}'.format(address))
m = re.search(r'(Line \d+ of \\?\".*\\?\")', result)
if m is not None:
return m.group(0)
else:
return '(unknown info for address 0x{0:x})'.format(address)
def get_value_of(self, symbol):
"""Returns the value of a symbol (in decimal)"""
result = self._run_for_one('print /d {0}'.format(symbol))
return int(result.split(' ')[-1], 10)
def get_value_of_string(self, symbol):
"""Returns the value of a symbol (as a string)"""
cmd = 'print /s {0}'.format(symbol)
result = self._run(cmd)
if len(result.lines) == 0:
raise GdbMIException(
cmd, '\n'.join(result.lines + result.oob_lines))
match = re.search(r'^[$]\d+ = \\"(.*)(\\\\n\\")', result.lines[0])
if match:
return match.group(1)
else:
match = re.search(r'^[$]\d+ = 0x[0-9a-fA-F]+ .* \\"(.*)(\\\\n\\")', result.lines[0])
if match:
return match.group(1)
return None
if __name__ == '__main__':
if len(sys.argv) != 3:
print('Usage: gdbmi.py gdb_path elf')
sys.exit(1)
gdb_path, elf = sys.argv[1:]
with GdbMI(gdb_path, elf) as g:
print('GDB Version: ' + g.version())
print('ion_buffer.heap offset: ' + str(g.field_offset('struct ion_buffer', 'heap')))
print('atomic_t.counter offset: ' + str(g.field_offset('atomic_t', 'counter')))
print('sizeof(struct ion_buffer): ' + str(g.sizeof('struct ion_buffer')))
addr = g.address_of('kernel_config_data')
print('address of kernel_config_data: ' + hex(addr))
symbol = g.get_symbol_info(addr)
print('symbol at ' + hex(addr) + ' : ' + symbol.symbol + \
' which is in section ' + symbol.section)