mojo/system/handle_table.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "mojo/system/handle_table.h"
   6
   7 #include "base/logging.h"
   8 #include "base/macros.h"
   9 #include "mojo/system/constants.h"
  10 #include "mojo/system/dispatcher.h"
  11
  12 namespace mojo {
  13 namespace system {
  14
  15 HandleTable::Entry::Entry() : busy(false) {
  16 }
  17
  18 HandleTable::Entry::Entry(const scoped_refptr<Dispatcher>& dispatcher)
  19     : dispatcher(dispatcher), busy(false) {
  20 }
  21
  22 HandleTable::Entry::~Entry() {
  23   DCHECK(!busy);
  24 }
  25
  26 HandleTable::HandleTable() : next_handle_(MOJO_HANDLE_INVALID + 1) {
  27 }
  28
  29 HandleTable::~HandleTable() {
  30   // This should usually not be reached (the only instance should be owned by
  31   // the singleton |Core|, which lives forever), except in tests.
  32 }
  33
  34 Dispatcher* HandleTable::GetDispatcher(MojoHandle handle) {
  35   DCHECK_NE(handle, MOJO_HANDLE_INVALID);
  36
  37   HandleToEntryMap::iterator it = handle_to_entry_map_.find(handle);
  38   if (it == handle_to_entry_map_.end())
  39     return NULL;
  40   return it->second.dispatcher.get();
  41 }
  42
  43 MojoResult HandleTable::GetAndRemoveDispatcher(
  44     MojoHandle handle,
  45     scoped_refptr<Dispatcher>* dispatcher) {
  46   DCHECK_NE(handle, MOJO_HANDLE_INVALID);
  47   DCHECK(dispatcher);
  48
  49   HandleToEntryMap::iterator it = handle_to_entry_map_.find(handle);
  50   if (it == handle_to_entry_map_.end())
  51     return MOJO_RESULT_INVALID_ARGUMENT;
  52   if (it->second.busy)
  53     return MOJO_RESULT_BUSY;
  54   *dispatcher = it->second.dispatcher;
  55   handle_to_entry_map_.erase(it);
  56
  57   return MOJO_RESULT_OK;
  58 }
  59
  60 MojoHandle HandleTable::AddDispatcher(
  61     const scoped_refptr<Dispatcher>& dispatcher) {
  62   if (handle_to_entry_map_.size() >= kMaxHandleTableSize)
  63     return MOJO_HANDLE_INVALID;
  64   return AddDispatcherNoSizeCheck(dispatcher);
  65 }
  66
  67 std::pair<MojoHandle, MojoHandle> HandleTable::AddDispatcherPair(
  68     const scoped_refptr<Dispatcher>& dispatcher0,
  69     const scoped_refptr<Dispatcher>& dispatcher1) {
  70   if (handle_to_entry_map_.size() + 1 >= kMaxHandleTableSize)
  71     return std::make_pair(MOJO_HANDLE_INVALID, MOJO_HANDLE_INVALID);
  72   return std::make_pair(AddDispatcherNoSizeCheck(dispatcher0),
  73                         AddDispatcherNoSizeCheck(dispatcher1));
  74 }
  75
  76 bool HandleTable::AddDispatcherVector(const DispatcherVector& dispatchers,
  77                                       MojoHandle* handles) {
  78   DCHECK_LE(dispatchers.size(), kMaxMessageNumHandles);
  79   DCHECK(handles);
  80   // TODO(vtl): |std::numeric_limits<size_t>::max()| isn't a compile-time
  81   // expression in C++03.
  82   COMPILE_ASSERT(
  83       static_cast<uint64_t>(kMaxHandleTableSize) + kMaxMessageNumHandles <
  84           (sizeof(size_t) == 8 ? kuint64max
  85                                : static_cast<uint64_t>(kuint32max)),
  86       addition_may_overflow);
  87
  88   if (handle_to_entry_map_.size() + dispatchers.size() > kMaxHandleTableSize)
  89     return false;
  90
  91   for (size_t i = 0; i < dispatchers.size(); i++) {
  92     if (dispatchers[i].get()) {
  93       handles[i] = AddDispatcherNoSizeCheck(dispatchers[i]);
  94     } else {
  95       LOG(WARNING) << "Invalid dispatcher at index " << i;
  96       handles[i] = MOJO_HANDLE_INVALID;
  97     }
  98   }
  99   return true;
 100 }
 101
 102 MojoResult HandleTable::MarkBusyAndStartTransport(
 103     MojoHandle disallowed_handle,
 104     const MojoHandle* handles,
 105     uint32_t num_handles,
 106     std::vector<DispatcherTransport>* transports) {
 107   DCHECK_NE(disallowed_handle, MOJO_HANDLE_INVALID);
 108   DCHECK(handles);
 109   DCHECK_LE(num_handles, kMaxMessageNumHandles);
 110   DCHECK(transports);
 111   DCHECK_EQ(transports->size(), num_handles);
 112
 113   std::vector<Entry*> entries(num_handles);
 114
 115   // First verify all the handles and get their dispatchers.
 116   uint32_t i;
 117   MojoResult error_result = MOJO_RESULT_INTERNAL;
 118   for (i = 0; i < num_handles; i++) {
 119     // Sending your own handle is not allowed (and, for consistency, returns
 120     // "busy").
 121     if (handles[i] == disallowed_handle) {
 122       error_result = MOJO_RESULT_BUSY;
 123       break;
 124     }
 125
 126     HandleToEntryMap::iterator it = handle_to_entry_map_.find(handles[i]);
 127     if (it == handle_to_entry_map_.end()) {
 128       error_result = MOJO_RESULT_INVALID_ARGUMENT;
 129       break;
 130     }
 131
 132     entries[i] = &it->second;
 133     if (entries[i]->busy) {
 134       error_result = MOJO_RESULT_BUSY;
 135       break;
 136     }
 137     // Note: By marking the handle as busy here, we're also preventing the
 138     // same handle from being sent multiple times in the same message.
 139     entries[i]->busy = true;
 140
 141     // Try to start the transport.
 142     DispatcherTransport transport =
 143         Dispatcher::HandleTableAccess::TryStartTransport(
 144             entries[i]->dispatcher.get());
 145     if (!transport.is_valid()) {
 146       // Only log for Debug builds, since this is not a problem with the system
 147       // code, but with user code.
 148       DLOG(WARNING) << "Likely race condition in user code detected: attempt "
 149                        "to transfer handle " << handles[i]
 150                     << " while it is in use on a different thread";
 151
 152       // Unset the busy flag (since it won't be unset below).
 153       entries[i]->busy = false;
 154       error_result = MOJO_RESULT_BUSY;
 155       break;
 156     }
 157
 158     // Check if the dispatcher is busy (e.g., in a two-phase read/write).
 159     // (Note that this must be done after the dispatcher's lock is acquired.)
 160     if (transport.IsBusy()) {
 161       // Unset the busy flag and end the transport (since it won't be done
 162       // below).
 163       entries[i]->busy = false;
 164       transport.End();
 165       error_result = MOJO_RESULT_BUSY;
 166       break;
 167     }
 168
 169     // Hang on to the transport (which we'll need to end the transport).
 170     (*transports)[i] = transport;
 171   }
 172   if (i < num_handles) {
 173     DCHECK_NE(error_result, MOJO_RESULT_INTERNAL);
 174
 175     // Unset the busy flags and release the locks.
 176     for (uint32_t j = 0; j < i; j++) {
 177       DCHECK(entries[j]->busy);
 178       entries[j]->busy = false;
 179       (*transports)[j].End();
 180     }
 181     return error_result;
 182   }
 183
 184   return MOJO_RESULT_OK;
 185 }
 186
 187 MojoHandle HandleTable::AddDispatcherNoSizeCheck(
 188     const scoped_refptr<Dispatcher>& dispatcher) {
 189   DCHECK(dispatcher.get());
 190   DCHECK_LT(handle_to_entry_map_.size(), kMaxHandleTableSize);
 191   DCHECK_NE(next_handle_, MOJO_HANDLE_INVALID);
 192
 193   // TODO(vtl): Maybe we want to do something different/smarter. (Or maybe try
 194   // assigning randomly?)
 195   while (handle_to_entry_map_.find(next_handle_) !=
 196          handle_to_entry_map_.end()) {
 197     next_handle_++;
 198     if (next_handle_ == MOJO_HANDLE_INVALID)
 199       next_handle_++;
 200   }
 201
 202   MojoHandle new_handle = next_handle_;
 203   handle_to_entry_map_[new_handle] = Entry(dispatcher);
 204
 205   next_handle_++;
 206   if (next_handle_ == MOJO_HANDLE_INVALID)
 207     next_handle_++;
 208
 209   return new_handle;
 210 }
 211
 212 void HandleTable::RemoveBusyHandles(const MojoHandle* handles,
 213                                     uint32_t num_handles) {
 214   DCHECK(handles);
 215   DCHECK_LE(num_handles, kMaxMessageNumHandles);
 216
 217   for (uint32_t i = 0; i < num_handles; i++) {
 218     HandleToEntryMap::iterator it = handle_to_entry_map_.find(handles[i]);
 219     DCHECK(it != handle_to_entry_map_.end());
 220     DCHECK(it->second.busy);
 221     it->second.busy = false;  // For the sake of a |DCHECK()|.
 222     handle_to_entry_map_.erase(it);
 223   }
 224 }
 225
 226 void HandleTable::RestoreBusyHandles(const MojoHandle* handles,
 227                                      uint32_t num_handles) {
 228   DCHECK(handles);
 229   DCHECK_LE(num_handles, kMaxMessageNumHandles);
 230
 231   for (uint32_t i = 0; i < num_handles; i++) {
 232     HandleToEntryMap::iterator it = handle_to_entry_map_.find(handles[i]);
 233     DCHECK(it != handle_to_entry_map_.end());
 234     DCHECK(it->second.busy);
 235     it->second.busy = false;
 236   }
 237 }
 238
 239 }  // namespace system
 240 }  // namespace mojo