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618f726f | 1 | # Copyright (C) 2015-2016 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 | ||
19 | class FrameId(object): | |
20 | ||
21 | def __init__(self, sp, pc): | |
22 | self._sp = sp | |
23 | self._pc = pc | |
24 | ||
25 | @property | |
26 | def sp(self): | |
27 | return self._sp | |
28 | ||
29 | @property | |
30 | def pc(self): | |
31 | return self._pc | |
32 | ||
33 | ||
34 | class TestUnwinder(Unwinder): | |
35 | AMD64_RBP = 6 | |
36 | AMD64_RSP = 7 | |
37 | AMD64_RIP = 16 | |
38 | ||
39 | def __init__(self): | |
40 | Unwinder.__init__(self, "test unwinder") | |
41 | self.char_ptr_t = gdb.lookup_type("unsigned char").pointer() | |
42 | self.char_ptr_ptr_t = self.char_ptr_t.pointer() | |
43 | ||
44 | def _read_word(self, address): | |
45 | return address.cast(self.char_ptr_ptr_t).dereference() | |
46 | ||
47 | def __call__(self, pending_frame): | |
48 | """Test unwinder written in Python. | |
49 | ||
50 | This unwinder can unwind the frames that have been deliberately | |
51 | corrupted in a specific way (functions in the accompanying | |
52 | py-unwind.c file do that.) | |
53 | This code is only on AMD64. | |
54 | On AMD64 $RBP points to the innermost frame (unless the code | |
55 | was compiled with -fomit-frame-pointer), which contains the | |
56 | address of the previous frame at offset 0. The functions | |
57 | deliberately corrupt their frames as follows: | |
58 | Before After | |
59 | Corruption: Corruption: | |
60 | +--------------+ +--------------+ | |
61 | RBP-8 | | | Previous RBP | | |
62 | +--------------+ +--------------+ | |
63 | RBP + Previous RBP | | RBP | | |
64 | +--------------+ +--------------+ | |
65 | RBP+8 | Return RIP | | Return RIP | | |
66 | +--------------+ +--------------+ | |
67 | Old SP | | | | | |
68 | ||
69 | This unwinder recognizes the corrupt frames by checking that | |
70 | *RBP == RBP, and restores previous RBP from the word above it. | |
71 | """ | |
72 | try: | |
73 | # NOTE: the registers in Unwinder API can be referenced | |
74 | # either by name or by number. The code below uses both | |
75 | # to achieve more coverage. | |
76 | bp = pending_frame.read_register("rbp").cast(self.char_ptr_t) | |
77 | if self._read_word(bp) != bp: | |
78 | return None | |
79 | # Found the frame that the test program has corrupted for us. | |
80 | # The correct BP for the outer frame has been saved one word | |
81 | # above, previous IP and SP are at the expected places. | |
82 | previous_bp = self._read_word(bp - 8) | |
83 | previous_ip = self._read_word(bp + 8) | |
84 | previous_sp = bp + 16 | |
85 | ||
86 | frame_id = FrameId( | |
87 | pending_frame.read_register(TestUnwinder.AMD64_RSP), | |
88 | pending_frame.read_register(TestUnwinder.AMD64_RIP)) | |
89 | unwind_info = pending_frame.create_unwind_info(frame_id) | |
90 | unwind_info.add_saved_register(TestUnwinder.AMD64_RBP, | |
91 | previous_bp) | |
92 | unwind_info.add_saved_register("rip", previous_ip) | |
93 | unwind_info.add_saved_register("rsp", previous_sp) | |
94 | return unwind_info | |
95 | except (gdb.error, RuntimeError): | |
96 | return None | |
97 | ||
98 | gdb.unwinder.register_unwinder(None, TestUnwinder(), True) | |
99 | print("Python script imported") |