1 /*
2 * Copyright (C) 2016 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 #ifndef LIBMEMUNREACHABLE_HEAP_WALKER_H_
18 #define LIBMEMUNREACHABLE_HEAP_WALKER_H_
19
20 #include <signal.h>
21
22 #include "android-base/macros.h"
23
24 #include "Allocator.h"
25 #include "ScopedSignalHandler.h"
26 #include "Tarjan.h"
27
28 namespace android {
29
30 // A range [begin, end)
31 struct Range {
32 uintptr_t begin;
33 uintptr_t end;
34
sizeRange35 size_t size() const { return end - begin; };
36 bool operator==(const Range& other) const {
37 return this->begin == other.begin && this->end == other.end;
38 }
39 bool operator!=(const Range& other) const { return !(*this == other); }
40 };
41
42 // Comparator for Ranges that returns equivalence for overlapping ranges
43 struct compare_range {
operatorcompare_range44 bool operator()(const Range& a, const Range& b) const { return a.end <= b.begin; }
45 };
46
47 class HeapWalker {
48 public:
HeapWalker(Allocator<HeapWalker> allocator)49 explicit HeapWalker(Allocator<HeapWalker> allocator)
50 : allocator_(allocator),
51 allocations_(allocator),
52 allocation_bytes_(0),
53 roots_(allocator),
54 root_vals_(allocator),
55 sigsegv_handler_(allocator),
56 sigbus_handler_(allocator),
57 walking_ptr_(0),
58 walking_range_{0, 0},
59 segv_logged_(false),
60 segv_page_count_(0) {
61 valid_allocations_range_.end = 0;
62 valid_allocations_range_.begin = ~valid_allocations_range_.end;
63 valid_mappings_range_.end = 0;
64 valid_mappings_range_.begin = ~valid_allocations_range_.end;
65
66 sigsegv_handler_.install(
67 SIGSEGV, [=](ScopedSignalHandler& handler, int signal, siginfo_t* siginfo, void* uctx) {
68 this->HandleSegFault(handler, signal, siginfo, uctx);
69 });
70 sigbus_handler_.install(
71 SIGBUS, [=](ScopedSignalHandler& handler, int signal, siginfo_t* siginfo, void* uctx) {
72 this->HandleSegFault(handler, signal, siginfo, uctx);
73 });
74 }
75
~HeapWalker()76 ~HeapWalker() {}
77 bool Allocation(uintptr_t begin, uintptr_t end);
78 void Mapping(uintptr_t begin, uintptr_t end);
79 void Root(uintptr_t begin, uintptr_t end);
80 void Root(const allocator::vector<uintptr_t>& vals);
81
82 bool DetectLeaks();
83
84 bool Leaked(allocator::vector<Range>&, size_t limit, size_t* num_leaks, size_t* leak_bytes);
85 size_t Allocations();
86 size_t AllocationBytes();
87
88 template <class F>
89 void ForEachPtrInRange(const Range& range, F&& f);
90
91 template <class F>
92 void ForEachAllocation(F&& f);
93
94 struct AllocationInfo {
95 bool referenced_from_root;
96 };
97
98 private:
99 void RecurseRoot(const Range& root);
100 bool WordContainsAllocationPtr(uintptr_t ptr, Range* range, AllocationInfo** info);
101 void HandleSegFault(ScopedSignalHandler&, int, siginfo_t*, void*);
102
103 DISALLOW_COPY_AND_ASSIGN(HeapWalker);
104 Allocator<HeapWalker> allocator_;
105 using AllocationMap = allocator::map<Range, AllocationInfo, compare_range>;
106 AllocationMap allocations_;
107 size_t allocation_bytes_;
108 Range valid_allocations_range_;
109 Range valid_mappings_range_;
110
111 allocator::vector<Range> roots_;
112 allocator::vector<uintptr_t> root_vals_;
113
114 ScopedSignalHandler sigsegv_handler_;
115 ScopedSignalHandler sigbus_handler_;
116 volatile uintptr_t walking_ptr_;
117 Range walking_range_;
118 bool segv_logged_;
119 size_t segv_page_count_;
120 };
121
122 template <class F>
ForEachPtrInRange(const Range & range,F && f)123 inline void HeapWalker::ForEachPtrInRange(const Range& range, F&& f) {
124 uintptr_t begin = (range.begin + (sizeof(uintptr_t) - 1)) & ~(sizeof(uintptr_t) - 1);
125 // TODO(ccross): we might need to consider a pointer to the end of a buffer
126 // to be inside the buffer, which means the common case of a pointer to the
127 // beginning of a buffer may keep two ranges live.
128 for (uintptr_t i = begin; i < range.end; i += sizeof(uintptr_t)) {
129 Range ref_range;
130 AllocationInfo* ref_info;
131 if (WordContainsAllocationPtr(i, &ref_range, &ref_info)) {
132 f(ref_range, ref_info);
133 }
134 }
135 }
136
137 template <class F>
ForEachAllocation(F && f)138 inline void HeapWalker::ForEachAllocation(F&& f) {
139 for (auto& it : allocations_) {
140 const Range& range = it.first;
141 HeapWalker::AllocationInfo& allocation = it.second;
142 f(range, allocation);
143 }
144 }
145
146 } // namespace android
147
148 #endif
149