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      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 
     35   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 {
     44   bool operator()(const Range& a, const Range& b) const { return a.end <= b.begin; }
     45 };
     46 
     47 class HeapWalker {
     48  public:
     49   explicit HeapWalker(Allocator<HeapWalker> allocator)
     50       : allocator_(allocator),
     51         allocations_(allocator),
     52         allocation_bytes_(0),
     53         roots_(allocator),
     54         root_vals_(allocator),
     55         segv_handler_(allocator),
     56         walking_ptr_(0) {
     57     valid_allocations_range_.end = 0;
     58     valid_allocations_range_.begin = ~valid_allocations_range_.end;
     59 
     60     segv_handler_.install(
     61         SIGSEGV, [=](ScopedSignalHandler& handler, int signal, siginfo_t* siginfo, void* uctx) {
     62           this->HandleSegFault(handler, signal, siginfo, uctx);
     63         });
     64   }
     65 
     66   ~HeapWalker() {}
     67   bool Allocation(uintptr_t begin, uintptr_t end);
     68   void Root(uintptr_t begin, uintptr_t end);
     69   void Root(const allocator::vector<uintptr_t>& vals);
     70 
     71   bool DetectLeaks();
     72 
     73   bool Leaked(allocator::vector<Range>&, size_t limit, size_t* num_leaks, size_t* leak_bytes);
     74   size_t Allocations();
     75   size_t AllocationBytes();
     76 
     77   template <class F>
     78   void ForEachPtrInRange(const Range& range, F&& f);
     79 
     80   template <class F>
     81   void ForEachAllocation(F&& f);
     82 
     83   struct AllocationInfo {
     84     bool referenced_from_root;
     85   };
     86 
     87  private:
     88   void RecurseRoot(const Range& root);
     89   bool WordContainsAllocationPtr(uintptr_t ptr, Range* range, AllocationInfo** info);
     90   void HandleSegFault(ScopedSignalHandler&, int, siginfo_t*, void*);
     91 
     92   DISALLOW_COPY_AND_ASSIGN(HeapWalker);
     93   Allocator<HeapWalker> allocator_;
     94   using AllocationMap = allocator::map<Range, AllocationInfo, compare_range>;
     95   AllocationMap allocations_;
     96   size_t allocation_bytes_;
     97   Range valid_allocations_range_;
     98 
     99   allocator::vector<Range> roots_;
    100   allocator::vector<uintptr_t> root_vals_;
    101 
    102   ScopedSignalHandler segv_handler_;
    103   uintptr_t walking_ptr_;
    104 };
    105 
    106 template <class F>
    107 inline void HeapWalker::ForEachPtrInRange(const Range& range, F&& f) {
    108   uintptr_t begin = (range.begin + (sizeof(uintptr_t) - 1)) & ~(sizeof(uintptr_t) - 1);
    109   // TODO(ccross): we might need to consider a pointer to the end of a buffer
    110   // to be inside the buffer, which means the common case of a pointer to the
    111   // beginning of a buffer may keep two ranges live.
    112   for (uintptr_t i = begin; i < range.end; i += sizeof(uintptr_t)) {
    113     Range ref_range;
    114     AllocationInfo* ref_info;
    115     if (WordContainsAllocationPtr(i, &ref_range, &ref_info)) {
    116       f(ref_range, ref_info);
    117     }
    118   }
    119 }
    120 
    121 template <class F>
    122 inline void HeapWalker::ForEachAllocation(F&& f) {
    123   for (auto& it : allocations_) {
    124     const Range& range = it.first;
    125     HeapWalker::AllocationInfo& allocation = it.second;
    126     f(range, allocation);
    127   }
    128 }
    129 
    130 }  // namespace android
    131 
    132 #endif
    133