1 /*
2 * Copyright (C) 2018 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 #include <atomic>
19 #include <memory>
20
21 #include <jni.h>
22 #include <signal.h>
23 #include <stdint.h>
24 #include <sys/mman.h>
25
26 #include "base/globals.h"
27 #include "base/mem_map.h"
28 #include "fault_handler.h"
29
30 namespace art {
31
32 class TestFaultHandler final : public FaultHandler {
33 public:
TestFaultHandler(FaultManager * manager)34 explicit TestFaultHandler(FaultManager* manager)
35 : FaultHandler(manager),
36 map_error_(),
37 target_map_(MemMap::MapAnonymous("test-305-mmap",
38 /* addr */ nullptr,
39 /* byte_count */ kPageSize,
40 /* prot */ PROT_NONE,
41 /* low_4gb */ false,
42 /* reuse */ false,
43 /* reservation */ nullptr,
44 /* error_msg */ &map_error_,
45 /* use_ashmem */ false)),
46 was_hit_(false) {
47 CHECK(target_map_.IsValid()) << "Unable to create segfault target address " << map_error_;
48 manager_->AddHandler(this, /*in_generated_code*/false);
49 }
50
~TestFaultHandler()51 virtual ~TestFaultHandler() {
52 manager_->RemoveHandler(this);
53 }
54
Action(int sig,siginfo_t * siginfo,void * context ATTRIBUTE_UNUSED)55 bool Action(int sig, siginfo_t* siginfo, void* context ATTRIBUTE_UNUSED) override {
56 CHECK_EQ(sig, SIGSEGV);
57 CHECK_EQ(reinterpret_cast<uint32_t*>(siginfo->si_addr),
58 GetTargetPointer()) << "Segfault on unexpected address!";
59 CHECK(!was_hit_) << "Recursive signal!";
60 was_hit_ = true;
61
62 LOG(INFO) << "SEGV Caught. mprotecting map.";
63 CHECK(target_map_.Protect(PROT_READ | PROT_WRITE)) << "Failed to mprotect R/W";
64 LOG(INFO) << "Setting value to be read.";
65 *GetTargetPointer() = kDataValue;
66 LOG(INFO) << "Changing prot to be read-only.";
67 CHECK(target_map_.Protect(PROT_READ)) << "Failed to mprotect R-only";
68 return true;
69 }
70
CauseSegfault()71 void CauseSegfault() {
72 CHECK_EQ(target_map_.GetProtect(), PROT_NONE);
73
74 // This will segfault. The handler should deal with it though and we will get a value out of it.
75 uint32_t data = *GetTargetPointer();
76
77 // Prevent re-ordering around the *GetTargetPointer by the compiler
78 std::atomic_signal_fence(std::memory_order_seq_cst);
79
80 CHECK(was_hit_);
81 CHECK_EQ(data, kDataValue) << "Unexpected read value from mmap";
82 CHECK_EQ(target_map_.GetProtect(), PROT_READ);
83 LOG(INFO) << "Success!";
84 }
85
86 private:
GetTargetPointer()87 uint32_t* GetTargetPointer() {
88 return reinterpret_cast<uint32_t*>(target_map_.Begin() + 8);
89 }
90
91 static constexpr uint32_t kDataValue = 0xDEADBEEF;
92
93 std::string map_error_;
94 MemMap target_map_;
95 bool was_hit_;
96 };
97
Java_Main_runFaultHandlerTest(JNIEnv *,jclass)98 extern "C" JNIEXPORT void JNICALL Java_Main_runFaultHandlerTest(JNIEnv*, jclass) {
99 std::unique_ptr<TestFaultHandler> handler(new TestFaultHandler(&fault_manager));
100 handler->CauseSegfault();
101 }
102
103 } // namespace art
104