1    :  // Copyright 2013 Google Inc. All Rights Reserved.
   2    :  //
   3    :  // Licensed under the Apache License, Version 2.0 (the "License");
   4    :  // you may not use this file except in compliance with the License.
   5    :  // You may obtain a copy of the License at
   6    :  //
   7    :  //     http://www.apache.org/licenses/LICENSE-2.0
   8    :  //
   9    :  // Unless required by applicable law or agreed to in writing, software
  10    :  // distributed under the License is distributed on an "AS IS" BASIS,
  11    :  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12    :  // See the License for the specific language governing permissions and
  13    :  // limitations under the License.
  14    :  
  15    :  #include "syzygy/agent/profiler/symbol_map.h"
  16    :  
  17    :  namespace agent {
  18    :  namespace profiler {
  19    :  
  20    :  base::subtle::Atomic32 SymbolMap::Symbol::next_symbol_id_ = 0;
  21    :  
  22  E :  SymbolMap::SymbolMap() {
  23  E :  }
  24    :  
  25  E :  SymbolMap::~SymbolMap() {
  26  E :  }
  27    :  
  28    :  void SymbolMap::AddSymbol(const void* start_addr,
  29    :                            size_t length,
  30  E :                            const base::StringPiece& name) {
  31  E :    base::AutoLock hold(lock_);
  32    :  
  33  E :    scoped_refptr<Symbol> symbol = new Symbol(name, start_addr);
  34    :    // TODO(siggi): Perhaps this should be an error?
  35  E :    if (!symbol)
  36  i :      return;
  37    :  
  38  E :    Range range(reinterpret_cast<const uint8*>(start_addr), length);
  39  E :    RetireRangeUnlocked(range);
  40    :  
  41    :    bool inserted = addr_space_.Insert(
  42  E :        Range(reinterpret_cast<const uint8*>(start_addr), length), symbol);
  43  E :    DCHECK(inserted);
  44  E :  }
  45    :  
  46  E :  void SymbolMap::MoveSymbol(const void* old_addr, const void* new_addr) {
  47  E :    base::AutoLock hold(lock_);
  48    :  
  49    :    SymbolAddressSpace::RangeMapIter found =
  50    :        addr_space_.FindFirstIntersection(
  51  E :            Range(reinterpret_cast<const uint8*>(old_addr), 1));
  52    :  
  53    :    // If we don't have a record of the original symbol, then we can't move it.
  54    :    // This may occur if a symbol provider starts pushing events only after its
  55    :    // address space has been stocked.
  56  E :    if (found == addr_space_.end() || found->first.start() != old_addr)
  57  i :      return;
  58    :  
  59  E :    scoped_refptr<Symbol> symbol = found->second;
  60    :  
  61    :    // Note the fact that it's been moved.
  62  E :    symbol->Move(new_addr);
  63    :  
  64  E :    size_t length = found->first.size();
  65  E :    addr_space_.Remove(found);
  66    :  
  67    :    RetireRangeUnlocked(
  68  E :        Range(reinterpret_cast<const uint8*>(new_addr), length));
  69    :  
  70    :    bool inserted = addr_space_.Insert(
  71  E :        Range(reinterpret_cast<const uint8*>(new_addr), length), symbol);
  72  E :    DCHECK(inserted);
  73  E :  }
  74    :  
  75  E :  scoped_refptr<SymbolMap::Symbol> SymbolMap::FindSymbol(const void* addr) {
  76  E :    base::AutoLock hold(lock_);
  77    :  
  78    :    SymbolAddressSpace::RangeMapIter found =
  79    :        addr_space_.FindFirstIntersection(
  80  E :            Range(reinterpret_cast<const uint8*>(addr), 1));
  81    :  
  82  E :    if (found == addr_space_.end())
  83  E :      return NULL;
  84    :  
  85  E :    return found->second;
  86  E :  }
  87    :  
  88  E :  void SymbolMap::RetireRangeUnlocked(const Range& range) {
  89  E :    lock_.AssertAcquired();
  90    :  
  91    :    SymbolAddressSpace::RangeMapIterPair found =
  92  E :        addr_space_.FindIntersecting(range);
  93  E :    SymbolAddressSpace::iterator it = found.first;
  94  E :    for (; it != found.second; ++it)
  95  E :      found.first->second->Invalidate();
  96    :  
  97  E :    addr_space_.Remove(found);
  98  E :  }
  99    :  
 100    :  SymbolMap::Symbol::Symbol(const base::StringPiece& name, const void* address)
 101    :      : name_(name.begin(), name.end()),
 102    :        move_count_(0),
 103    :        id_(0),
 104  E :        address_(address) {
 105  E :  }
 106    :  
 107  E :  bool SymbolMap::Symbol::EnsureHasId() {
 108  E :    DCHECK(!invalid());
 109  E :    if (base::subtle::Acquire_Load(&id_) != 0)
 110  E :      return false;
 111    :  
 112    :    // Allocate a new symbol ID. Note that we may be racing against other
 113    :    // threads to assign this ID to the symbol, hence the compare-and-swap
 114    :    // below. In the case of a race, this ID may not get allocated to any
 115    :    // symbol.
 116  E :    base::subtle::Atomic32 next_id = 0;
 117    :    do {
 118  E :      next_id = base::subtle::NoBarrier_AtomicIncrement(&next_symbol_id_, 1);
 119  E :    } while (next_id == 0);
 120    :  
 121  E :    return base::subtle::NoBarrier_CompareAndSwap(&id_, 0, next_id) == 0;
 122  E :  }
 123    :  
 124  E :  void SymbolMap::Symbol::Invalidate() {
 125  E :    DCHECK(!invalid());
 126  E :    Move(NULL);
 127  E :  }
 128    :  
 129  E :  void SymbolMap::Symbol::Move(const void* new_address) {
 130  E :    DCHECK(!invalid());
 131    :    // TODO(siggi): The intent here is to make sure other cores see the new
 132    :    //     value without delay. The barrier may not be what's needed to do that?
 133  E :    address_ = new_address;
 134  E :    base::subtle::Barrier_AtomicIncrement(&move_count_, 1);
 135  E :  }
 136    :  
 137    :  }  // namespace profiler
 138    :  }  // namespace agent