1 /*
2 * Copyright (C) 2012 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 /*
18 * Contributed by: Intel Corporation
19 */
20
21 #include <gtest/gtest.h>
22 #include "BionicDeathTest.h"
23
24 #include <pthread.h>
25 #include <stdint.h>
26 #include <stdio.h>
27 #include <unistd.h>
28 #include <set>
29
30 extern "C" pid_t gettid();
31
32 // For x86, bionic and glibc have per-thread stack guard values (all identical).
33 #if defined(__i386__)
GetGuardFromTls()34 static uint32_t GetGuardFromTls() {
35 uint32_t guard;
36 asm ("mov %%gs:0x14, %0": "=d" (guard));
37 return guard;
38 }
39
40 struct stack_protector_checker {
41 std::set<pid_t> tids;
42 std::set<uint32_t> guards;
43
Checkstack_protector_checker44 void Check() {
45 pid_t tid = gettid();
46 uint32_t guard = GetGuardFromTls();
47
48 printf("[thread %d] %%gs:0x14 = 0x%08x\n", tid, guard);
49
50 // Duplicate tid. gettid(2) bug? Seeing this would be very upsetting.
51 ASSERT_TRUE(tids.find(tid) == tids.end());
52
53 // Uninitialized guard. Our bug. Note this is potentially flaky; we _could_ get
54 // four random zero bytes, but it should be vanishingly unlikely.
55 ASSERT_NE(guard, 0U);
56
57 tids.insert(tid);
58 guards.insert(guard);
59 }
60 };
61
ThreadGuardHelper(void * arg)62 static void* ThreadGuardHelper(void* arg) {
63 stack_protector_checker* checker = reinterpret_cast<stack_protector_checker*>(arg);
64 checker->Check();
65 return NULL;
66 }
67 #endif // __i386__
68
TEST(stack_protector,same_guard_per_thread)69 TEST(stack_protector, same_guard_per_thread) {
70 #if defined(__i386__)
71 stack_protector_checker checker;
72 size_t thread_count = 10;
73 for (size_t i = 0; i < thread_count; ++i) {
74 pthread_t t;
75 ASSERT_EQ(0, pthread_create(&t, NULL, ThreadGuardHelper, &checker));
76 void* result;
77 ASSERT_EQ(0, pthread_join(t, &result));
78 ASSERT_EQ(NULL, result);
79 }
80 ASSERT_EQ(thread_count, checker.tids.size());
81
82 // bionic and glibc use the same guard for every thread.
83 ASSERT_EQ(1U, checker.guards.size());
84 #else // __i386__
85 GTEST_LOG_(INFO) << "This test does nothing.\n";
86 #endif // __i386__
87 }
88
89 // For ARM and MIPS, glibc has a global stack check guard value.
90 #if defined(__BIONIC__) || defined(__arm__) || defined(__mips__)
91 #define TEST_STACK_CHK_GUARD
92
93 // Bionic has the global for x86 too, to support binaries that can run on
94 // Android releases that didn't implement the TLS guard value.
95 extern "C" uintptr_t __stack_chk_guard;
96
97 /*
98 * When this function returns, the stack canary will be inconsistent
99 * with the previous value, which will generate a call to __stack_chk_fail(),
100 * eventually resulting in a SIGABRT.
101 *
102 * This must be marked with "__attribute__ ((noinline))", to ensure the
103 * compiler generates the proper stack guards around this function.
104 */
105 static char* dummy_buf;
106
107 __attribute__ ((noinline))
do_modify_stack_chk_guard()108 static void do_modify_stack_chk_guard() {
109 char buf[128];
110 // Store local array's address to global variable to force compiler to generate stack guards.
111 dummy_buf = buf;
112 __stack_chk_guard = 0x12345678;
113 }
114
115 #endif
116
TEST(stack_protector,global_guard)117 TEST(stack_protector, global_guard) {
118 #if defined(TEST_STACK_CHK_GUARD)
119 ASSERT_NE(0, gettid());
120 ASSERT_NE(0U, __stack_chk_guard);
121 #else // TEST_STACK_CHK_GUARD
122 GTEST_LOG_(INFO) << "This test does nothing.\n";
123 #endif // TEST_STACK_CHK_GUARD
124 }
125
126 class stack_protector_DeathTest : public BionicDeathTest {};
127
TEST_F(stack_protector_DeathTest,modify_stack_protector)128 TEST_F(stack_protector_DeathTest, modify_stack_protector) {
129 #if defined(TEST_STACK_CHK_GUARD)
130 ASSERT_EXIT(do_modify_stack_chk_guard(), testing::KilledBySignal(SIGABRT), "");
131 #else // TEST_STACK_CHK_GUARD
132 GTEST_LOG_(INFO) << "This test does nothing.\n";
133 #endif // TEST_STACK_CHK_GUARD
134 }
135