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 "fault_handler.h"
27 #include "globals.h"
28 #include "mem_map.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 /* error_msg */ &map_error_,
44 /* use_ashmem */ false)),
45 was_hit_(false) {
46 CHECK(target_map_ != nullptr) << "Unable to create segfault target address " << map_error_;
47 manager_->AddHandler(this, /*in_generated_code*/false);
48 }
49
~TestFaultHandler()50 virtual ~TestFaultHandler() {
51 manager_->RemoveHandler(this);
52 }
53
Action(int sig,siginfo_t * siginfo,void * context ATTRIBUTE_UNUSED)54 bool Action(int sig, siginfo_t* siginfo, void* context ATTRIBUTE_UNUSED) OVERRIDE {
55 CHECK_EQ(sig, SIGSEGV);
56 CHECK_EQ(reinterpret_cast<uint32_t*>(siginfo->si_addr),
57 GetTargetPointer()) << "Segfault on unexpected address!";
58 CHECK(!was_hit_) << "Recursive signal!";
59 was_hit_ = true;
60
61 LOG(INFO) << "SEGV Caught. mprotecting map.";
62 CHECK(target_map_->Protect(PROT_READ | PROT_WRITE)) << "Failed to mprotect R/W";
63 LOG(INFO) << "Setting value to be read.";
64 *GetTargetPointer() = kDataValue;
65 LOG(INFO) << "Changing prot to be read-only.";
66 CHECK(target_map_->Protect(PROT_READ)) << "Failed to mprotect R-only";
67 return true;
68 }
69
CauseSegfault()70 void CauseSegfault() {
71 CHECK_EQ(target_map_->GetProtect(), PROT_NONE);
72
73 // This will segfault. The handler should deal with it though and we will get a value out of it.
74 uint32_t data = *GetTargetPointer();
75
76 // Prevent re-ordering around the *GetTargetPointer by the compiler
77 std::atomic_signal_fence(std::memory_order_seq_cst);
78
79 CHECK(was_hit_);
80 CHECK_EQ(data, kDataValue) << "Unexpected read value from mmap";
81 CHECK_EQ(target_map_->GetProtect(), PROT_READ);
82 LOG(INFO) << "Success!";
83 }
84
85 private:
GetTargetPointer()86 uint32_t* GetTargetPointer() {
87 return reinterpret_cast<uint32_t*>(target_map_->Begin() + 8);
88 }
89
90 static constexpr uint32_t kDataValue = 0xDEADBEEF;
91
92 std::string map_error_;
93 std::unique_ptr<MemMap> target_map_;
94 bool was_hit_;
95 };
96
Java_Main_runFaultHandlerTest(JNIEnv *,jclass)97 extern "C" JNIEXPORT void JNICALL Java_Main_runFaultHandlerTest(JNIEnv*, jclass) {
98 std::unique_ptr<TestFaultHandler> handler(new TestFaultHandler(&fault_manager));
99 handler->CauseSegfault();
100 }
101
102 } // namespace art
103