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213516ef | 1 | # Copyright (C) 2015-2023 Free Software Foundation, Inc. |
d11916aa SS |
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 | import gdb | |
17 | from gdb.unwinder import Unwinder | |
18 | ||
d11916aa | 19 | |
bdc8cfc1 TT |
20 | # These are set to test whether invalid register names cause an error. |
21 | add_saved_register_error = False | |
22 | read_register_error = False | |
23 | ||
24 | ||
13123da8 | 25 | class FrameId(object): |
d11916aa SS |
26 | def __init__(self, sp, pc): |
27 | self._sp = sp | |
28 | self._pc = pc | |
29 | ||
30 | @property | |
31 | def sp(self): | |
32 | return self._sp | |
33 | ||
34 | @property | |
35 | def pc(self): | |
36 | return self._pc | |
37 | ||
13123da8 | 38 | |
d11916aa SS |
39 | class TestUnwinder(Unwinder): |
40 | AMD64_RBP = 6 | |
41 | AMD64_RSP = 7 | |
43d5901d | 42 | AMD64_RIP = None |
d11916aa SS |
43 | |
44 | def __init__(self): | |
45 | Unwinder.__init__(self, "test unwinder") | |
46 | self.char_ptr_t = gdb.lookup_type("unsigned char").pointer() | |
47 | self.char_ptr_ptr_t = self.char_ptr_t.pointer() | |
43d5901d AB |
48 | self._last_arch = None |
49 | ||
50 | # Update the register descriptor AMD64_RIP based on ARCH. | |
13123da8 SM |
51 | def _update_register_descriptors(self, arch): |
52 | if self._last_arch != arch: | |
53 | TestUnwinder.AMD64_RIP = arch.registers().find("rip") | |
43d5901d | 54 | self._last_arch = arch |
d11916aa SS |
55 | |
56 | def _read_word(self, address): | |
57 | return address.cast(self.char_ptr_ptr_t).dereference() | |
58 | ||
59 | def __call__(self, pending_frame): | |
60 | """Test unwinder written in Python. | |
61 | ||
62 | This unwinder can unwind the frames that have been deliberately | |
63 | corrupted in a specific way (functions in the accompanying | |
64 | py-unwind.c file do that.) | |
65 | This code is only on AMD64. | |
66 | On AMD64 $RBP points to the innermost frame (unless the code | |
67 | was compiled with -fomit-frame-pointer), which contains the | |
68 | address of the previous frame at offset 0. The functions | |
69 | deliberately corrupt their frames as follows: | |
70 | Before After | |
71 | Corruption: Corruption: | |
72 | +--------------+ +--------------+ | |
73 | RBP-8 | | | Previous RBP | | |
74 | +--------------+ +--------------+ | |
75 | RBP + Previous RBP | | RBP | | |
76 | +--------------+ +--------------+ | |
77 | RBP+8 | Return RIP | | Return RIP | | |
78 | +--------------+ +--------------+ | |
79 | Old SP | | | | | |
80 | ||
81 | This unwinder recognizes the corrupt frames by checking that | |
82 | *RBP == RBP, and restores previous RBP from the word above it. | |
83 | """ | |
87dbc774 AB |
84 | |
85 | # Check that we can access the architecture of the pending | |
86 | # frame, and that this is the same architecture as for the | |
87 | # currently selected inferior. | |
13123da8 SM |
88 | inf_arch = gdb.selected_inferior().architecture() |
89 | frame_arch = pending_frame.architecture() | |
90 | if inf_arch != frame_arch: | |
91 | raise gdb.GdbError("architecture mismatch") | |
87dbc774 | 92 | |
13123da8 | 93 | self._update_register_descriptors(frame_arch) |
43d5901d | 94 | |
d11916aa SS |
95 | try: |
96 | # NOTE: the registers in Unwinder API can be referenced | |
97 | # either by name or by number. The code below uses both | |
98 | # to achieve more coverage. | |
99 | bp = pending_frame.read_register("rbp").cast(self.char_ptr_t) | |
100 | if self._read_word(bp) != bp: | |
101 | return None | |
102 | # Found the frame that the test program has corrupted for us. | |
103 | # The correct BP for the outer frame has been saved one word | |
104 | # above, previous IP and SP are at the expected places. | |
105 | previous_bp = self._read_word(bp - 8) | |
106 | previous_ip = self._read_word(bp + 8) | |
107 | previous_sp = bp + 16 | |
108 | ||
bdc8cfc1 TT |
109 | try: |
110 | pending_frame.read_register("nosuchregister") | |
111 | except ValueError: | |
112 | global read_register_error | |
113 | read_register_error = True | |
114 | ||
d11916aa SS |
115 | frame_id = FrameId( |
116 | pending_frame.read_register(TestUnwinder.AMD64_RSP), | |
13123da8 SM |
117 | pending_frame.read_register(TestUnwinder.AMD64_RIP), |
118 | ) | |
d11916aa | 119 | unwind_info = pending_frame.create_unwind_info(frame_id) |
13123da8 | 120 | unwind_info.add_saved_register(TestUnwinder.AMD64_RBP, previous_bp) |
d11916aa SS |
121 | unwind_info.add_saved_register("rip", previous_ip) |
122 | unwind_info.add_saved_register("rsp", previous_sp) | |
bdc8cfc1 TT |
123 | try: |
124 | unwind_info.add_saved_register("nosuchregister", previous_sp) | |
125 | except ValueError: | |
126 | global add_saved_register_error | |
127 | add_saved_register_error = True | |
d11916aa SS |
128 | return unwind_info |
129 | except (gdb.error, RuntimeError): | |
130 | return None | |
131 | ||
13123da8 | 132 | |
d11916aa SS |
133 | gdb.unwinder.register_unwinder(None, TestUnwinder(), True) |
134 | print("Python script imported") |