1 /*
2 * Copyright (C) 2016 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29 #include "linker_gdb_support.h"
30
31 #include <pthread.h>
32
33 #include "private/ScopedPthreadMutexLocker.h"
34
35 // This function is an empty stub where GDB locates a breakpoint to get notified
36 // about linker activity.
37 extern "C"
38 void __attribute__((noinline)) __attribute__((visibility("default"))) rtld_db_dlactivity();
39
40 r_debug _r_debug =
41 {1, nullptr, reinterpret_cast<uintptr_t>(&rtld_db_dlactivity), r_debug::RT_CONSISTENT, 0};
42
43 static pthread_mutex_t g__r_debug_mutex = PTHREAD_MUTEX_INITIALIZER;
44 static link_map* r_debug_tail = nullptr;
45
insert_link_map_into_debug_map(link_map * map)46 void insert_link_map_into_debug_map(link_map* map) {
47 // Stick the new library at the end of the list.
48 // gdb tends to care more about libc than it does
49 // about leaf libraries, and ordering it this way
50 // reduces the back-and-forth over the wire.
51 if (r_debug_tail != nullptr) {
52 r_debug_tail->l_next = map;
53 map->l_prev = r_debug_tail;
54 map->l_next = nullptr;
55 } else {
56 _r_debug.r_map = map;
57 map->l_prev = nullptr;
58 map->l_next = nullptr;
59 }
60 r_debug_tail = map;
61 }
62
remove_link_map_from_debug_map(link_map * map)63 void remove_link_map_from_debug_map(link_map* map) {
64 if (r_debug_tail == map) {
65 r_debug_tail = map->l_prev;
66 }
67
68 if (map->l_prev) {
69 map->l_prev->l_next = map->l_next;
70 }
71 if (map->l_next) {
72 map->l_next->l_prev = map->l_prev;
73 }
74 }
75
notify_gdb_of_load(link_map * map)76 void notify_gdb_of_load(link_map* map) {
77 ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
78
79 _r_debug.r_state = r_debug::RT_ADD;
80 rtld_db_dlactivity();
81
82 insert_link_map_into_debug_map(map);
83
84 _r_debug.r_state = r_debug::RT_CONSISTENT;
85 rtld_db_dlactivity();
86 }
87
notify_gdb_of_unload(link_map * map)88 void notify_gdb_of_unload(link_map* map) {
89 ScopedPthreadMutexLocker locker(&g__r_debug_mutex);
90
91 _r_debug.r_state = r_debug::RT_DELETE;
92 rtld_db_dlactivity();
93
94 remove_link_map_from_debug_map(map);
95
96 _r_debug.r_state = r_debug::RT_CONSISTENT;
97 rtld_db_dlactivity();
98 }
99
notify_gdb_of_libraries()100 void notify_gdb_of_libraries() {
101 _r_debug.r_state = r_debug::RT_ADD;
102 rtld_db_dlactivity();
103 _r_debug.r_state = r_debug::RT_CONSISTENT;
104 rtld_db_dlactivity();
105 }
106
107