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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "mojo/system/handle_table.h"
#include "base/logging.h"
#include "base/macros.h"
#include "mojo/system/constants.h"
#include "mojo/system/dispatcher.h"
namespace mojo {
namespace system {
HandleTable::Entry::Entry() : busy(false) {
}
HandleTable::Entry::Entry(const scoped_refptr<Dispatcher>& dispatcher)
: dispatcher(dispatcher), busy(false) {
}
HandleTable::Entry::~Entry() {
DCHECK(!busy);
}
HandleTable::HandleTable() : next_handle_(MOJO_HANDLE_INVALID + 1) {
}
HandleTable::~HandleTable() {
// This should usually not be reached (the only instance should be owned by
// the singleton |Core|, which lives forever), except in tests.
}
Dispatcher* HandleTable::GetDispatcher(MojoHandle handle) {
DCHECK_NE(handle, MOJO_HANDLE_INVALID);
HandleToEntryMap::iterator it = handle_to_entry_map_.find(handle);
if (it == handle_to_entry_map_.end())
return NULL;
return it->second.dispatcher.get();
}
MojoResult HandleTable::GetAndRemoveDispatcher(
MojoHandle handle,
scoped_refptr<Dispatcher>* dispatcher) {
DCHECK_NE(handle, MOJO_HANDLE_INVALID);
DCHECK(dispatcher);
HandleToEntryMap::iterator it = handle_to_entry_map_.find(handle);
if (it == handle_to_entry_map_.end())
return MOJO_RESULT_INVALID_ARGUMENT;
if (it->second.busy)
return MOJO_RESULT_BUSY;
*dispatcher = it->second.dispatcher;
handle_to_entry_map_.erase(it);
return MOJO_RESULT_OK;
}
MojoHandle HandleTable::AddDispatcher(
const scoped_refptr<Dispatcher>& dispatcher) {
if (handle_to_entry_map_.size() >= kMaxHandleTableSize)
return MOJO_HANDLE_INVALID;
return AddDispatcherNoSizeCheck(dispatcher);
}
std::pair<MojoHandle, MojoHandle> HandleTable::AddDispatcherPair(
const scoped_refptr<Dispatcher>& dispatcher0,
const scoped_refptr<Dispatcher>& dispatcher1) {
if (handle_to_entry_map_.size() + 1 >= kMaxHandleTableSize)
return std::make_pair(MOJO_HANDLE_INVALID, MOJO_HANDLE_INVALID);
return std::make_pair(AddDispatcherNoSizeCheck(dispatcher0),
AddDispatcherNoSizeCheck(dispatcher1));
}
bool HandleTable::AddDispatcherVector(const DispatcherVector& dispatchers,
MojoHandle* handles) {
DCHECK_LE(dispatchers.size(), kMaxMessageNumHandles);
DCHECK(handles);
// TODO(vtl): |std::numeric_limits<size_t>::max()| isn't a compile-time
// expression in C++03.
COMPILE_ASSERT(
static_cast<uint64_t>(kMaxHandleTableSize) + kMaxMessageNumHandles <
(sizeof(size_t) == 8 ? kuint64max
: static_cast<uint64_t>(kuint32max)),
addition_may_overflow);
if (handle_to_entry_map_.size() + dispatchers.size() > kMaxHandleTableSize)
return false;
for (size_t i = 0; i < dispatchers.size(); i++) {
if (dispatchers[i].get()) {
handles[i] = AddDispatcherNoSizeCheck(dispatchers[i]);
} else {
LOG(WARNING) << "Invalid dispatcher at index " << i;
handles[i] = MOJO_HANDLE_INVALID;
}
}
return true;
}
MojoResult HandleTable::MarkBusyAndStartTransport(
MojoHandle disallowed_handle,
const MojoHandle* handles,
uint32_t num_handles,
std::vector<DispatcherTransport>* transports) {
DCHECK_NE(disallowed_handle, MOJO_HANDLE_INVALID);
DCHECK(handles);
DCHECK_LE(num_handles, kMaxMessageNumHandles);
DCHECK(transports);
DCHECK_EQ(transports->size(), num_handles);
std::vector<Entry*> entries(num_handles);
// First verify all the handles and get their dispatchers.
uint32_t i;
MojoResult error_result = MOJO_RESULT_INTERNAL;
for (i = 0; i < num_handles; i++) {
// Sending your own handle is not allowed (and, for consistency, returns
// "busy").
if (handles[i] == disallowed_handle) {
error_result = MOJO_RESULT_BUSY;
break;
}
HandleToEntryMap::iterator it = handle_to_entry_map_.find(handles[i]);
if (it == handle_to_entry_map_.end()) {
error_result = MOJO_RESULT_INVALID_ARGUMENT;
break;
}
entries[i] = &it->second;
if (entries[i]->busy) {
error_result = MOJO_RESULT_BUSY;
break;
}
// Note: By marking the handle as busy here, we're also preventing the
// same handle from being sent multiple times in the same message.
entries[i]->busy = true;
// Try to start the transport.
DispatcherTransport transport =
Dispatcher::HandleTableAccess::TryStartTransport(
entries[i]->dispatcher.get());
if (!transport.is_valid()) {
// Only log for Debug builds, since this is not a problem with the system
// code, but with user code.
DLOG(WARNING) << "Likely race condition in user code detected: attempt "
"to transfer handle " << handles[i]
<< " while it is in use on a different thread";
// Unset the busy flag (since it won't be unset below).
entries[i]->busy = false;
error_result = MOJO_RESULT_BUSY;
break;
}
// Check if the dispatcher is busy (e.g., in a two-phase read/write).
// (Note that this must be done after the dispatcher's lock is acquired.)
if (transport.IsBusy()) {
// Unset the busy flag and end the transport (since it won't be done
// below).
entries[i]->busy = false;
transport.End();
error_result = MOJO_RESULT_BUSY;
break;
}
// Hang on to the transport (which we'll need to end the transport).
(*transports)[i] = transport;
}
if (i < num_handles) {
DCHECK_NE(error_result, MOJO_RESULT_INTERNAL);
// Unset the busy flags and release the locks.
for (uint32_t j = 0; j < i; j++) {
DCHECK(entries[j]->busy);
entries[j]->busy = false;
(*transports)[j].End();
}
return error_result;
}
return MOJO_RESULT_OK;
}
MojoHandle HandleTable::AddDispatcherNoSizeCheck(
const scoped_refptr<Dispatcher>& dispatcher) {
DCHECK(dispatcher.get());
DCHECK_LT(handle_to_entry_map_.size(), kMaxHandleTableSize);
DCHECK_NE(next_handle_, MOJO_HANDLE_INVALID);
// TODO(vtl): Maybe we want to do something different/smarter. (Or maybe try
// assigning randomly?)
while (handle_to_entry_map_.find(next_handle_) !=
handle_to_entry_map_.end()) {
next_handle_++;
if (next_handle_ == MOJO_HANDLE_INVALID)
next_handle_++;
}
MojoHandle new_handle = next_handle_;
handle_to_entry_map_[new_handle] = Entry(dispatcher);
next_handle_++;
if (next_handle_ == MOJO_HANDLE_INVALID)
next_handle_++;
return new_handle;
}
void HandleTable::RemoveBusyHandles(const MojoHandle* handles,
uint32_t num_handles) {
DCHECK(handles);
DCHECK_LE(num_handles, kMaxMessageNumHandles);
for (uint32_t i = 0; i < num_handles; i++) {
HandleToEntryMap::iterator it = handle_to_entry_map_.find(handles[i]);
DCHECK(it != handle_to_entry_map_.end());
DCHECK(it->second.busy);
it->second.busy = false; // For the sake of a |DCHECK()|.
handle_to_entry_map_.erase(it);
}
}
void HandleTable::RestoreBusyHandles(const MojoHandle* handles,
uint32_t num_handles) {
DCHECK(handles);
DCHECK_LE(num_handles, kMaxMessageNumHandles);
for (uint32_t i = 0; i < num_handles; i++) {
HandleToEntryMap::iterator it = handle_to_entry_map_.find(handles[i]);
DCHECK(it != handle_to_entry_map_.end());
DCHECK(it->second.busy);
it->second.busy = false;
}
}
} // namespace system
} // namespace mojo
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