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Diffstat (limited to 'security/sandbox/chromium/sandbox/win/src/sharedmem_ipc_client.h')
| -rw-r--r-- | security/sandbox/chromium/sandbox/win/src/sharedmem_ipc_client.h | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/security/sandbox/chromium/sandbox/win/src/sharedmem_ipc_client.h b/security/sandbox/chromium/sandbox/win/src/sharedmem_ipc_client.h new file mode 100644 index 0000000000..73f739dece --- /dev/null +++ b/security/sandbox/chromium/sandbox/win/src/sharedmem_ipc_client.h @@ -0,0 +1,140 @@ +// Copyright (c) 2006-2008 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. + +#ifndef SANDBOX_SRC_SHAREDMEM_IPC_CLIENT_H__ +#define SANDBOX_SRC_SHAREDMEM_IPC_CLIENT_H__ + +#include <stddef.h> +#include <stdint.h> + +#include "sandbox/win/src/crosscall_params.h" +#include "sandbox/win/src/ipc_tags.h" +#include "sandbox/win/src/sandbox.h" + +// IPC transport implementation that uses shared memory. +// This is the client side +// +// The shared memory is divided on blocks called channels, and potentially +// it can perform as many concurrent IPC calls as channels. The IPC over +// each channel is strictly synchronous for the client. +// +// Each channel as a channel control section associated with. Each control +// section has two kernel events (known as ping and pong) and a integer +// variable that maintains a state +// +// this is the state diagram of a channel: +// +// locked in service +// kFreeChannel---------->BusyChannel-------------->kAckChannel +// ^ | +// |_________________________________________________| +// answer ready +// +// The protocol is as follows: +// 1) client finds a free channel: state = kFreeChannel +// 2) does an atomic compare-and-swap, now state = BusyChannel +// 3) client writes the data into the channel buffer +// 4) client signals the ping event and waits (blocks) on the pong event +// 5) eventually the server signals the pong event +// 6) the client awakes and reads the answer from the same channel +// 7) the client updates its InOut parameters with the new data from the +// shared memory section. +// 8) the client atomically sets the state = kFreeChannel +// +// In the shared memory the layout is as follows: +// +// [ channel count ] +// [ channel control 0] +// [ channel control 1] +// [ channel control N] +// [ channel buffer 0 ] 1024 bytes +// [ channel buffer 1 ] 1024 bytes +// [ channel buffer N ] 1024 bytes +// +// By default each channel buffer is 1024 bytes +namespace sandbox { + +// the possible channel states as described above +enum ChannelState { + // channel is free + kFreeChannel = 1, + // IPC in progress client side + kBusyChannel, + // IPC in progress server side + kAckChannel, + // not used right now + kReadyChannel, + // IPC abandoned by client side + kAbandonedChannel +}; + +// The next two constants control the time outs for the IPC. +const DWORD kIPCWaitTimeOut1 = 1000; // Milliseconds. +const DWORD kIPCWaitTimeOut2 = 50; // Milliseconds. + +// the channel control structure +struct ChannelControl { + // points to be beginning of the channel buffer, where data goes + size_t channel_base; + // maintains the state from the ChannelState enumeration + volatile LONG state; + // the ping event is signaled by the client when the IPC data is ready on + // the buffer + HANDLE ping_event; + // the client waits on the pong event for the IPC answer back + HANDLE pong_event; + // the IPC unique identifier + IpcTag ipc_tag; +}; + +struct IPCControl { + // total number of channels available, some might be busy at a given time + size_t channels_count; + // handle to a shared mutex to detect when the server is dead + HANDLE server_alive; + // array of channel control structures + ChannelControl channels[1]; +}; + +// the actual shared memory IPC implementation class. This object is designed +// to be lightweight so it can be constructed on-site (at the calling place) +// wherever an IPC call is needed. +class SharedMemIPCClient { + public: + // Creates the IPC client. + // as parameter it takes the base address of the shared memory + explicit SharedMemIPCClient(void* shared_mem); + + // locks a free channel and returns the channel buffer memory base. This call + // blocks until there is a free channel + void* GetBuffer(); + + // releases the lock on the channel, for other to use. call this if you have + // called GetBuffer and you want to abort but have not called yet DoCall() + void FreeBuffer(void* buffer); + + // Performs the actual IPC call. + // params: The blob of packed input parameters. + // answer: upon IPC completion, it contains the server answer to the IPC. + // If the return value is not SBOX_ERROR_CHANNEL_ERROR, the caller has to free + // the channel. + // returns ALL_OK if the IPC mechanism successfully delivered. You still need + // to check on the answer structure to see the actual IPC result. + ResultCode DoCall(CrossCallParams* params, CrossCallReturn* answer); + + private: + // Returns the index of the first free channel. It sets 'severe_failure' + // to true if there is an unrecoverable error that does not allow to + // find a channel. + size_t LockFreeChannel(bool* severe_failure); + // Return the channel index given the address of the buffer. + size_t ChannelIndexFromBuffer(const void* buffer); + IPCControl* control_; + // point to the first channel base + char* first_base_; +}; + +} // namespace sandbox + +#endif // SANDBOX_SRC_SHAREDMEM_IPC_CLIENT_H__ |