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      1 /*
      2  * Copyright (C) 2014 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 ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
     18 #define ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
     19 
     20 #include <sys/mman.h>  // For the PROT_* and MAP_* constants.
     21 
     22 #include "base/bit_utils.h"
     23 #include "base/mutex.h"
     24 #include "gc/space/space.h"
     25 #include "globals.h"
     26 #include "mem_map.h"
     27 
     28 namespace art {
     29 namespace gc {
     30 namespace accounting {
     31 
     32 // Used to decide whether to take the read barrier fast/slow paths for
     33 // kUseTableLookupReadBarrier. If an entry is set, take the read
     34 // barrier slow path. There's an entry per region.
     35 class ReadBarrierTable {
     36  public:
     37   ReadBarrierTable() {
     38     size_t capacity = static_cast<size_t>(kHeapCapacity / kRegionSize);
     39     DCHECK_EQ(kHeapCapacity / kRegionSize,
     40               static_cast<uint64_t>(static_cast<size_t>(kHeapCapacity / kRegionSize)));
     41     std::string error_msg;
     42     MemMap* mem_map = MemMap::MapAnonymous("read barrier table", nullptr, capacity,
     43                                            PROT_READ | PROT_WRITE, false, false, &error_msg);
     44     CHECK(mem_map != nullptr && mem_map->Begin() != nullptr)
     45         << "couldn't allocate read barrier table: " << error_msg;
     46     mem_map_.reset(mem_map);
     47   }
     48   void ClearForSpace(space::ContinuousSpace* space) {
     49     uint8_t* entry_start = EntryFromAddr(space->Begin());
     50     uint8_t* entry_end = EntryFromAddr(space->Limit());
     51     memset(reinterpret_cast<void*>(entry_start), 0, entry_end - entry_start);
     52   }
     53   void Clear(uint8_t* start_addr, uint8_t* end_addr) {
     54     DCHECK(IsValidHeapAddr(start_addr)) << start_addr;
     55     DCHECK(IsValidHeapAddr(end_addr)) << end_addr;
     56     DCHECK_ALIGNED(start_addr, kRegionSize);
     57     DCHECK_ALIGNED(end_addr, kRegionSize);
     58     uint8_t* entry_start = EntryFromAddr(start_addr);
     59     uint8_t* entry_end = EntryFromAddr(end_addr);
     60     memset(reinterpret_cast<void*>(entry_start), 0, entry_end - entry_start);
     61   }
     62   bool IsSet(const void* heap_addr) const {
     63     DCHECK(IsValidHeapAddr(heap_addr)) << heap_addr;
     64     uint8_t entry_value = *EntryFromAddr(heap_addr);
     65     DCHECK(entry_value == 0 || entry_value == kSetEntryValue);
     66     return entry_value == kSetEntryValue;
     67   }
     68   void ClearAll() {
     69     mem_map_->MadviseDontNeedAndZero();
     70   }
     71   void SetAll() {
     72     memset(mem_map_->Begin(), kSetEntryValue, mem_map_->Size());
     73   }
     74   bool IsAllCleared() const {
     75     for (uint32_t* p = reinterpret_cast<uint32_t*>(mem_map_->Begin());
     76          p < reinterpret_cast<uint32_t*>(mem_map_->End()); ++p) {
     77       if (*p != 0) {
     78         return false;
     79       }
     80     }
     81     return true;
     82   }
     83 
     84   // This should match RegionSpace::kRegionSize. static_assert'ed in concurrent_copying.h.
     85   static constexpr size_t kRegionSize = 256 * KB;
     86 
     87  private:
     88   static constexpr uint64_t kHeapCapacity = 4ULL * GB;  // low 4gb.
     89   static constexpr uint8_t kSetEntryValue = 0x01;
     90 
     91   uint8_t* EntryFromAddr(const void* heap_addr) const {
     92     DCHECK(IsValidHeapAddr(heap_addr)) << heap_addr;
     93     uint8_t* entry_addr = mem_map_->Begin() + reinterpret_cast<uintptr_t>(heap_addr) / kRegionSize;
     94     DCHECK(IsValidEntry(entry_addr)) << "heap_addr: " << heap_addr
     95                                      << " entry_addr: " << reinterpret_cast<void*>(entry_addr);
     96     return entry_addr;
     97   }
     98 
     99   bool IsValidHeapAddr(const void* heap_addr) const {
    100 #ifdef __LP64__
    101     return reinterpret_cast<uint64_t>(heap_addr) < kHeapCapacity;
    102 #else
    103     UNUSED(heap_addr);
    104     return true;
    105 #endif
    106   }
    107 
    108   bool IsValidEntry(const uint8_t* entry_addr) const {
    109     uint8_t* begin = mem_map_->Begin();
    110     uint8_t* end = mem_map_->End();
    111     return entry_addr >= begin && entry_addr < end;
    112   }
    113 
    114   std::unique_ptr<MemMap> mem_map_;
    115 };
    116 
    117 }  // namespace accounting
    118 }  // namespace gc
    119 }  // namespace art
    120 
    121 #endif  // ART_RUNTIME_GC_ACCOUNTING_READ_BARRIER_TABLE_H_
    122