1 /*
2 * Copyright (C) 2020 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17 #include <gtest/gtest.h>
18
19 #if defined(__BIONIC__)
20
21 #include <sys/mman.h>
22
23 #include "platform/bionic/android_unsafe_frame_pointer_chase.h"
24
25 // Prevent tail calls inside recurse.
nop(size_t val)26 __attribute__((weak, noinline)) size_t nop(size_t val) {
27 return val;
28 }
29
30 // Call android_unsafe_frame_pointer_chase inside count recurse stack frames.
recurse(int count,uintptr_t * buf,size_t num_entries)31 __attribute__((weak, noinline)) int recurse(int count, uintptr_t* buf, size_t num_entries) {
32 if (count != 0) return nop(recurse(count - 1, buf, num_entries));
33 return nop(android_unsafe_frame_pointer_chase(buf, num_entries));
34 }
35
36 static constexpr size_t kNumFrames = 32;
37
CheckFrames(uintptr_t * frames,size_t num_frames)38 static bool CheckFrames(uintptr_t* frames, size_t num_frames) {
39 // We expect one recurse frame calling android_unsafe_frame_pointer_chase, followed by kNumFrames identical
40 // recurse frames calling themselves, followed by at least one frame (the first caller of
41 // recurse).
42 if (num_frames < kNumFrames + 2) {
43 printf("num_frames (0x%zu) < kNumFrames + 2", num_frames);
44 return false;
45 }
46
47 if (frames[0] == frames[1]) {
48 printf("frames[0] == frames[1] (0x%zx)", frames[0]);
49 return false;
50 }
51
52 for (size_t i = 2; i <= kNumFrames; ++i) {
53 if (frames[i] != frames[1]) {
54 printf("frames[i] (0x%zx) != frames[1] (0x%zx)", frames[i], frames[1]);
55 return false;
56 }
57 }
58
59 if (frames[kNumFrames] == frames[kNumFrames + 1]) {
60 printf("frames[kNumFrames] == frames[kNumFrames + 1] (0x%zx)", frames[kNumFrames]);
61 return false;
62 }
63
64 return true;
65 }
66
TEST(android_unsafe_frame_pointer_chase,main_thread)67 TEST(android_unsafe_frame_pointer_chase, main_thread) {
68 size_t size = recurse(kNumFrames, 0, 0);
69
70 uintptr_t frames[kNumFrames + 2];
71 size_t size2 = recurse(kNumFrames, frames, kNumFrames + 2);
72 EXPECT_EQ(size2, size);
73
74 EXPECT_TRUE(CheckFrames(frames, size));
75 }
76
tester_func()77 static const char* tester_func() {
78 size_t size = recurse(kNumFrames, 0, 0);
79
80 uintptr_t frames[kNumFrames + 2];
81 size_t size2 = recurse(kNumFrames, frames, kNumFrames + 2);
82 if (size2 != size) {
83 return "size2 != size";
84 }
85
86 if (!CheckFrames(frames, size)) {
87 return "CheckFrames failed";
88 }
89 return nullptr;
90 }
91
BacktraceThread(void *)92 static void* BacktraceThread(void*) {
93 return (void*)tester_func();
94 }
95
TEST(android_unsafe_frame_pointer_chase,pthread)96 TEST(android_unsafe_frame_pointer_chase, pthread) {
97 pthread_t t;
98 ASSERT_EQ(0, pthread_create(&t, nullptr, BacktraceThread, nullptr));
99 void* retval;
100 ASSERT_EQ(0, pthread_join(t, &retval));
101 EXPECT_EQ(nullptr, reinterpret_cast<char*>(retval));
102 }
103
104 static bool g_handler_called;
105 static const char* g_handler_tester_result;
106
BacktraceHandler(int)107 static void BacktraceHandler(int) {
108 g_handler_called = true;
109 g_handler_tester_result = tester_func();
110 }
111
112 static constexpr size_t kStackSize = 16384;
113
SignalBacktraceThread(void * sp)114 static void* SignalBacktraceThread(void* sp) {
115 stack_t ss;
116 ss.ss_sp = sp;
117 ss.ss_flags = 0;
118 ss.ss_size = kStackSize;
119 sigaltstack(&ss, nullptr);
120
121 struct sigaction s = {};
122 s.sa_handler = BacktraceHandler;
123 s.sa_flags = SA_ONSTACK;
124 sigaction(SIGRTMIN, &s, nullptr);
125
126 raise(SIGRTMIN);
127 return nullptr;
128 }
129
TEST(android_unsafe_frame_pointer_chase,sigaltstack)130 TEST(android_unsafe_frame_pointer_chase, sigaltstack) {
131 // Create threads where the alternate stack appears both after and before the regular stack, and
132 // call android_unsafe_frame_pointer_chase from a signal handler. Without handling for the
133 // alternate signal stack, this would cause false negatives or potential false positives in the
134 // android_unsafe_frame_pointer_chase function.
135 void* stacks =
136 mmap(nullptr, kStackSize * 2, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0);
137
138 for (unsigned i = 0; i != 2; ++i) {
139 pthread_t t;
140 pthread_attr_t attr;
141 ASSERT_EQ(0, pthread_attr_init(&attr));
142 ASSERT_EQ(0, pthread_attr_setstack(&attr, reinterpret_cast<char*>(stacks) + kStackSize * i,
143 kStackSize));
144
145 ASSERT_EQ(0, pthread_create(&t, &attr, SignalBacktraceThread,
146 reinterpret_cast<char*>(stacks) + kStackSize * (1 - i)));
147 void* retval;
148 ASSERT_EQ(0, pthread_join(t, &retval));
149
150 EXPECT_TRUE(g_handler_called);
151 EXPECT_EQ(nullptr, g_handler_tester_result);
152 g_handler_called = false;
153 }
154
155 munmap(stacks, kStackSize * 2);
156 }
157
158 #endif // __BIONIC__
159