1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
# Copyright (C) 2015-2023 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# 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.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
import gdb
from gdb.unwinder import Unwinder
# These are set to test whether invalid register names cause an error.
add_saved_register_error = False
read_register_error = False
class FrameId(object):
def __init__(self, sp, pc):
self._sp = sp
self._pc = pc
@property
def sp(self):
return self._sp
@property
def pc(self):
return self._pc
class TestUnwinder(Unwinder):
AMD64_RBP = 6
AMD64_RSP = 7
AMD64_RIP = None
def __init__(self):
Unwinder.__init__(self, "test unwinder")
self.char_ptr_t = gdb.lookup_type("unsigned char").pointer()
self.char_ptr_ptr_t = self.char_ptr_t.pointer()
self._last_arch = None
# Update the register descriptor AMD64_RIP based on ARCH.
def _update_register_descriptors(self, arch):
if self._last_arch != arch:
TestUnwinder.AMD64_RIP = arch.registers().find("rip")
self._last_arch = arch
def _read_word(self, address):
return address.cast(self.char_ptr_ptr_t).dereference()
def __call__(self, pending_frame):
"""Test unwinder written in Python.
This unwinder can unwind the frames that have been deliberately
corrupted in a specific way (functions in the accompanying
py-unwind.c file do that.)
This code is only on AMD64.
On AMD64 $RBP points to the innermost frame (unless the code
was compiled with -fomit-frame-pointer), which contains the
address of the previous frame at offset 0. The functions
deliberately corrupt their frames as follows:
Before After
Corruption: Corruption:
+--------------+ +--------------+
RBP-8 | | | Previous RBP |
+--------------+ +--------------+
RBP + Previous RBP | | RBP |
+--------------+ +--------------+
RBP+8 | Return RIP | | Return RIP |
+--------------+ +--------------+
Old SP | | | |
This unwinder recognizes the corrupt frames by checking that
*RBP == RBP, and restores previous RBP from the word above it.
"""
# Check that we can access the architecture of the pending
# frame, and that this is the same architecture as for the
# currently selected inferior.
inf_arch = gdb.selected_inferior().architecture()
frame_arch = pending_frame.architecture()
if inf_arch != frame_arch:
raise gdb.GdbError("architecture mismatch")
self._update_register_descriptors(frame_arch)
try:
# NOTE: the registers in Unwinder API can be referenced
# either by name or by number. The code below uses both
# to achieve more coverage.
bp = pending_frame.read_register("rbp").cast(self.char_ptr_t)
if self._read_word(bp) != bp:
return None
# Found the frame that the test program has corrupted for us.
# The correct BP for the outer frame has been saved one word
# above, previous IP and SP are at the expected places.
previous_bp = self._read_word(bp - 8)
previous_ip = self._read_word(bp + 8)
previous_sp = bp + 16
try:
pending_frame.read_register("nosuchregister")
except ValueError:
global read_register_error
read_register_error = True
frame_id = FrameId(
pending_frame.read_register(TestUnwinder.AMD64_RSP),
pending_frame.read_register(TestUnwinder.AMD64_RIP),
)
unwind_info = pending_frame.create_unwind_info(frame_id)
unwind_info.add_saved_register(TestUnwinder.AMD64_RBP, previous_bp)
unwind_info.add_saved_register("rip", previous_ip)
unwind_info.add_saved_register("rsp", previous_sp)
try:
unwind_info.add_saved_register("nosuchregister", previous_sp)
except ValueError:
global add_saved_register_error
add_saved_register_error = True
return unwind_info
except (gdb.error, RuntimeError):
return None
gdb.unwinder.register_unwinder(None, TestUnwinder(), True)
print("Python script imported")
|
