1# Copyright (C) 2016-2020 Free Software Foundation, Inc. 2 3# This program is free software; you can redistribute it and/or modify 4# it under the terms of the GNU General Public License as published by 5# the Free Software Foundation; either version 3 of the License, or 6# (at your option) any later version. 7# 8# This program is distributed in the hope that it will be useful, 9# but WITHOUT ANY WARRANTY; without even the implied warranty of 10# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 11# GNU General Public License for more details. 12# 13# You should have received a copy of the GNU General Public License 14# along with this program. If not, see <http://www.gnu.org/licenses/>. 15 16# This unwinder never does any unwinding. It'll (pretend to) "sniff" 17# the frame and ultimately return None, indicating that actual unwinding 18# should be performed by some other unwinder. 19# 20# But, prior to returning None, it will attempt to obtain the value 21# associated with a symbol via a call to gdb.parse_and_eval(). In 22# the course of doing this evaluation, GDB will potentially access 23# some frames, leading to the possibility of a recursive invocation of 24# this unwinder. If that should happen, code contained herein detects 25# that and prints a message which will cause some of the associated 26# tests to FAIL. 27 28import gdb 29from gdb.unwinder import Unwinder 30 31class TestUnwinder(Unwinder): 32 33 count = 0 34 35 @classmethod 36 def reset_count (cls): 37 cls.count = 0 38 39 @classmethod 40 def inc_count (cls): 41 cls.count += 1 42 43 test = 'check_undefined_symbol' 44 45 @classmethod 46 def set_test (cls, test) : 47 cls.test = test 48 49 def __init__(self): 50 Unwinder.__init__(self, "test unwinder") 51 self.recurse_level = 0 52 53 def __call__(self, pending_frame): 54 55 if self.recurse_level > 0: 56 gdb.write("TestUnwinder: Recursion detected - returning early.\n") 57 return None 58 59 self.recurse_level += 1 60 TestUnwinder.inc_count() 61 62 if TestUnwinder.test == 'check_user_reg_pc' : 63 64 pc = pending_frame.read_register('pc') 65 pc_as_int = int(pc.cast(gdb.lookup_type('int'))) 66 # gdb.write("In unwinder: pc=%x\n" % pc_as_int) 67 68 elif TestUnwinder.test == 'check_pae_pc' : 69 70 pc = gdb.parse_and_eval('$pc') 71 pc_as_int = int(pc.cast(gdb.lookup_type('int'))) 72 # gdb.write("In unwinder: pc=%x\n" % pc_as_int) 73 74 elif TestUnwinder.test == 'check_undefined_symbol' : 75 76 try: 77 val = gdb.parse_and_eval("undefined_symbol") 78 79 except Exception as arg: 80 pass 81 82 self.recurse_level -= 1 83 84 return None 85 86gdb.unwinder.register_unwinder(None, TestUnwinder(), True) 87gdb.write("Python script imported\n") 88