sandbox/win/src/crosscall_client.h - chromium/src - Git at Google

 // Copyright (c) 2012 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_CROSSCALL_CLIENT_H_
 #define SANDBOX_SRC_CROSSCALL_CLIENT_H_

 #include <stddef.h>
 #include <stdint.h>

 #include "base/compiler_specific.h"
 #include "sandbox/win/src/crosscall_params.h"
 #include "sandbox/win/src/sandbox.h"

 // This header defines the CrossCall(..) family of templated functions
 // Their purpose is to simulate the syntax of regular call but to generate
 // and IPC from the client-side.
 //
 // The basic pattern is to
 //   1) use template argument deduction to compute the size of each
 //      parameter and the appropriate copy method
 //   2) pack the parameters in the appropriate ActualCallParams< > object
 //   3) call the IPC interface IPCProvider::DoCall( )
 //
 // The general interface of CrossCall is:
 //  ResultCode CrossCall(IPCProvider& ipc_provider,
 //                       uint32_t tag,
 //                       const Par1& p1, const Par2& p2,...pn
 //                       CrossCallReturn* answer)
 //
 //  where:
 //    ipc_provider: is a specific implementation of the ipc transport see
 //                  sharedmem_ipc_server.h for an example.
 //    tag : is the unique id for this IPC call. Is used to route the call to
 //          the appropriate service.
 //    p1, p2,.. pn : The input parameters of the IPC. Use only simple types
 //                   and wide strings (can add support for others).
 //    answer : If the IPC was successful. The server-side answer is here. The
 //             interpretation of the answer is private to client and server.
 //
 // The return value is ALL_OK if the IPC was delivered to the server, other
 // return codes indicate that the IPC transport failed to deliver it.
 namespace sandbox {

 // this is the assumed channel size. This can be overridden in a given
 // IPC implementation.
 const uint32_t kIPCChannelSize = 1024;

 // The copy helper uses templates to deduce the appropriate copy function to
 // copy the input parameters in the buffer that is going to be send across the
 // IPC. These template facility can be made more sophisticated as need arises.

 // The default copy helper. It catches the general case where no other
 // specialized template matches better. We set the type to UINT32_TYPE, so this
 // only works with objects whose size is 32 bits.
 template <typename T>
 class CopyHelper {
  public:
   CopyHelper(const T& t) : t_(t) {}

   // Returns the pointer to the start of the input.
   const void* GetStart() const { return &t_; }

   // Update the stored value with the value in the buffer. This is not
   // supported for this type.
   bool Update(void* buffer) {
     // Not supported;
     return true;
   }

   // Returns the size of the input in bytes.
   uint32_t GetSize() const { return sizeof(T); }

   // Returns true if the current type is used as an In or InOut parameter.
   bool IsInOut() { return false; }

   // Returns this object's type.
   ArgType GetType() {
     static_assert(sizeof(T) == sizeof(uint32_t), "specialization needed");
     return UINT32_TYPE;
   }

  private:
   const T& t_;
 };

 // This copy helper template specialization if for the void pointer
 // case both 32 and 64 bit.
 template <>
 class CopyHelper<void*> {
  public:
   CopyHelper(void* t) : t_(t) {}

   // Returns the pointer to the start of the input.
   const void* GetStart() const { return &t_; }

   // Update the stored value with the value in the buffer. This is not
   // supported for this type.
   bool Update(void* buffer) {
     // Not supported;
     return true;
   }

   // Returns the size of the input in bytes.
   uint32_t GetSize() const { return sizeof(t_); }

   // Returns true if the current type is used as an In or InOut parameter.
   bool IsInOut() { return false; }

   // Returns this object's type.
   ArgType GetType() { return VOIDPTR_TYPE; }

  private:
   const void* t_;
 };

 // This copy helper template specialization catches the cases where the
 // parameter is a pointer to a string.
 template <>
 class CopyHelper<const wchar_t*> {
  public:
   CopyHelper(const wchar_t* t) : t_(t) {}

   // Returns the pointer to the start of the string.
   const void* GetStart() const { return t_; }

   // Update the stored value with the value in the buffer. This is not
   // supported for this type.
   bool Update(void* buffer) {
     // Not supported;
     return true;
   }

   // Returns the size of the string in bytes. We define a nullptr string to
   // be of zero length.
   uint32_t GetSize() const {
     __try {
       return (!t_) ? 0
                    : static_cast<uint32_t>(StringLength(t_) * sizeof(t_[0]));
     } __except (EXCEPTION_EXECUTE_HANDLER) {
       return UINT32_MAX;
     }
   }

   // Returns true if the current type is used as an In or InOut parameter.
   bool IsInOut() { return false; }

   ArgType GetType() { return WCHAR_TYPE; }

  private:
   // We provide our not very optimized version of wcslen(), since we don't
   // want to risk having the linker use the version in the CRT since the CRT
   // might not be present when we do an early IPC call.
   static size_t CDECL StringLength(const wchar_t* wcs) {
     const wchar_t* eos = wcs;
     while (*eos++)
       ;
     return static_cast<size_t>(eos - wcs - 1);
   }

   const wchar_t* t_;
 };

 // Specialization for non-const strings. We just reuse the implementation of the
 // const string specialization.
 template <>
 class CopyHelper<wchar_t*> : public CopyHelper<const wchar_t*> {
  public:
   typedef CopyHelper<const wchar_t*> Base;
   CopyHelper(wchar_t* t) : Base(t) {}

   const void* GetStart() const { return Base::GetStart(); }

   bool Update(void* buffer) { return Base::Update(buffer); }

   uint32_t GetSize() const { return Base::GetSize(); }

   bool IsInOut() { return Base::IsInOut(); }

   ArgType GetType() { return Base::GetType(); }
 };

 // Specialization for wchar_t arrays strings. We just reuse the implementation
 // of the const string specialization.
 template <size_t n>
 class CopyHelper<const wchar_t[n]> : public CopyHelper<const wchar_t*> {
  public:
   typedef const wchar_t array[n];
   typedef CopyHelper<const wchar_t*> Base;
   CopyHelper(array t) : Base(t) {}

   const void* GetStart() const { return Base::GetStart(); }

   bool Update(void* buffer) { return Base::Update(buffer); }

   uint32_t GetSize() const { return Base::GetSize(); }

   bool IsInOut() { return Base::IsInOut(); }

   ArgType GetType() { return Base::GetType(); }
 };

 // Generic encapsulation class containing a pointer to a buffer and the
 // size of the buffer. It is used by the IPC to be able to pass in/out
 // parameters.
 class InOutCountedBuffer : public CountedBuffer {
  public:
   InOutCountedBuffer(void* buffer, uint32_t size)
       : CountedBuffer(buffer, size) {}
 };

 // This copy helper template specialization catches the cases where the
 // parameter is a an input/output buffer.
 template <>
 class CopyHelper<InOutCountedBuffer> {
  public:
   CopyHelper(const InOutCountedBuffer t) : t_(t) {}

   // Returns the pointer to the start of the string.
   const void* GetStart() const { return t_.Buffer(); }

   // Updates the buffer with the value from the new buffer in parameter.
   bool Update(void* buffer) {
     // We are touching user memory, this has to be done from inside a try
     // except.
     __try {
       memcpy(t_.Buffer(), buffer, t_.Size());
     } __except (EXCEPTION_EXECUTE_HANDLER) {
       return false;
     }
     return true;
   }

   // Returns the size of the string in bytes. We define a nullptr string to
   // be of zero length.
   uint32_t GetSize() const { return t_.Size(); }

   // Returns true if the current type is used as an In or InOut parameter.
   bool IsInOut() { return true; }

   ArgType GetType() { return INOUTPTR_TYPE; }

  private:
   const InOutCountedBuffer t_;
 };

 // The following two macros make it less error prone the generation
 // of CrossCall functions with ever more input parameters.

 #define XCALL_GEN_PARAMS_OBJ(num, params)                      \
   typedef ActualCallParams<num, kIPCChannelSize> ActualParams; \
   void* raw_mem = ipc_provider.GetBuffer();                    \
   if (!raw_mem)                                                \
     return SBOX_ERROR_NO_SPACE;                                \
   ActualParams* params = new (raw_mem) ActualParams(tag);

 #define XCALL_GEN_COPY_PARAM(num, params)                                  \
   static_assert(kMaxIpcParams >= num, "too many parameters");              \
   CopyHelper<Par##num> ch##num(p##num);                                    \
   if (!params->CopyParamIn(num - 1, ch##num.GetStart(), ch##num.GetSize(), \
                            ch##num.IsInOut(), ch##num.GetType()))          \
     return SBOX_ERROR_NO_SPACE;

 #define XCALL_GEN_UPDATE_PARAM(num, params)            \
   if (!ch##num.Update(params->GetParamPtr(num - 1))) { \
     ipc_provider.FreeBuffer(raw_mem);                  \
     return SBOX_ERROR_BAD_PARAMS;                      \
   }

 #define XCALL_GEN_FREE_CHANNEL() ipc_provider.FreeBuffer(raw_mem);

 // CrossCall template with one input parameter
 template <typename IPCProvider, typename Par1>
 ResultCode CrossCall(IPCProvider& ipc_provider,
                      uint32_t tag,
                      const Par1& p1,
                      CrossCallReturn* answer) {
   XCALL_GEN_PARAMS_OBJ(1, call_params);
   XCALL_GEN_COPY_PARAM(1, call_params);

   ResultCode result = ipc_provider.DoCall(call_params, answer);

   if (SBOX_ERROR_CHANNEL_ERROR != result) {
     XCALL_GEN_UPDATE_PARAM(1, call_params);
     XCALL_GEN_FREE_CHANNEL();
   }

   return result;
 }

 // CrossCall template with two input parameters.
 template <typename IPCProvider, typename Par1, typename Par2>
 ResultCode CrossCall(IPCProvider& ipc_provider,
                      uint32_t tag,
                      const Par1& p1,
                      const Par2& p2,
                      CrossCallReturn* answer) {
   XCALL_GEN_PARAMS_OBJ(2, call_params);
   XCALL_GEN_COPY_PARAM(1, call_params);
   XCALL_GEN_COPY_PARAM(2, call_params);

   ResultCode result = ipc_provider.DoCall(call_params, answer);

   if (SBOX_ERROR_CHANNEL_ERROR != result) {
     XCALL_GEN_UPDATE_PARAM(1, call_params);
     XCALL_GEN_UPDATE_PARAM(2, call_params);
     XCALL_GEN_FREE_CHANNEL();
   }
   return result;
 }

 // CrossCall template with three input parameters.
 template <typename IPCProvider, typename Par1, typename Par2, typename Par3>
 ResultCode CrossCall(IPCProvider& ipc_provider,
                      uint32_t tag,
                      const Par1& p1,
                      const Par2& p2,
                      const Par3& p3,
                      CrossCallReturn* answer) {
   XCALL_GEN_PARAMS_OBJ(3, call_params);
   XCALL_GEN_COPY_PARAM(1, call_params);
   XCALL_GEN_COPY_PARAM(2, call_params);
   XCALL_GEN_COPY_PARAM(3, call_params);

   ResultCode result = ipc_provider.DoCall(call_params, answer);

   if (SBOX_ERROR_CHANNEL_ERROR != result) {
     XCALL_GEN_UPDATE_PARAM(1, call_params);
     XCALL_GEN_UPDATE_PARAM(2, call_params);
     XCALL_GEN_UPDATE_PARAM(3, call_params);
     XCALL_GEN_FREE_CHANNEL();
   }
   return result;
 }

 // CrossCall template with four input parameters.
 template <typename IPCProvider,
           typename Par1,
           typename Par2,
           typename Par3,
           typename Par4>
 ResultCode CrossCall(IPCProvider& ipc_provider,
                      uint32_t tag,
                      const Par1& p1,
                      const Par2& p2,
                      const Par3& p3,
                      const Par4& p4,
                      CrossCallReturn* answer) {
   XCALL_GEN_PARAMS_OBJ(4, call_params);
   XCALL_GEN_COPY_PARAM(1, call_params);
   XCALL_GEN_COPY_PARAM(2, call_params);
   XCALL_GEN_COPY_PARAM(3, call_params);
   XCALL_GEN_COPY_PARAM(4, call_params);

   ResultCode result = ipc_provider.DoCall(call_params, answer);

   if (SBOX_ERROR_CHANNEL_ERROR != result) {
     XCALL_GEN_UPDATE_PARAM(1, call_params);
     XCALL_GEN_UPDATE_PARAM(2, call_params);
     XCALL_GEN_UPDATE_PARAM(3, call_params);
     XCALL_GEN_UPDATE_PARAM(4, call_params);
     XCALL_GEN_FREE_CHANNEL();
   }
   return result;
 }

 // CrossCall template with five input parameters.
 template <typename IPCProvider,
           typename Par1,
           typename Par2,
           typename Par3,
           typename Par4,
           typename Par5>
 ResultCode CrossCall(IPCProvider& ipc_provider,
                      uint32_t tag,
                      const Par1& p1,
                      const Par2& p2,
                      const Par3& p3,
                      const Par4& p4,
                      const Par5& p5,
                      CrossCallReturn* answer) {
   XCALL_GEN_PARAMS_OBJ(5, call_params);
   XCALL_GEN_COPY_PARAM(1, call_params);
   XCALL_GEN_COPY_PARAM(2, call_params);
   XCALL_GEN_COPY_PARAM(3, call_params);
   XCALL_GEN_COPY_PARAM(4, call_params);
   XCALL_GEN_COPY_PARAM(5, call_params);

   ResultCode result = ipc_provider.DoCall(call_params, answer);

   if (SBOX_ERROR_CHANNEL_ERROR != result) {
     XCALL_GEN_UPDATE_PARAM(1, call_params);
     XCALL_GEN_UPDATE_PARAM(2, call_params);
     XCALL_GEN_UPDATE_PARAM(3, call_params);
     XCALL_GEN_UPDATE_PARAM(4, call_params);
     XCALL_GEN_UPDATE_PARAM(5, call_params);
     XCALL_GEN_FREE_CHANNEL();
   }
   return result;
 }

 // CrossCall template with six input parameters.
 template <typename IPCProvider,
           typename Par1,
           typename Par2,
           typename Par3,
           typename Par4,
           typename Par5,
           typename Par6>
 ResultCode CrossCall(IPCProvider& ipc_provider,
                      uint32_t tag,
                      const Par1& p1,
                      const Par2& p2,
                      const Par3& p3,
                      const Par4& p4,
                      const Par5& p5,
                      const Par6& p6,
                      CrossCallReturn* answer) {
   XCALL_GEN_PARAMS_OBJ(6, call_params);
   XCALL_GEN_COPY_PARAM(1, call_params);
   XCALL_GEN_COPY_PARAM(2, call_params);
   XCALL_GEN_COPY_PARAM(3, call_params);
   XCALL_GEN_COPY_PARAM(4, call_params);
   XCALL_GEN_COPY_PARAM(5, call_params);
   XCALL_GEN_COPY_PARAM(6, call_params);

   ResultCode result = ipc_provider.DoCall(call_params, answer);

   if (SBOX_ERROR_CHANNEL_ERROR != result) {
     XCALL_GEN_UPDATE_PARAM(1, call_params);
     XCALL_GEN_UPDATE_PARAM(2, call_params);
     XCALL_GEN_UPDATE_PARAM(3, call_params);
     XCALL_GEN_UPDATE_PARAM(4, call_params);
     XCALL_GEN_UPDATE_PARAM(5, call_params);
     XCALL_GEN_UPDATE_PARAM(6, call_params);
     XCALL_GEN_FREE_CHANNEL();
   }
   return result;
 }

 // CrossCall template with seven input parameters.
 template <typename IPCProvider,
           typename Par1,
           typename Par2,
           typename Par3,
           typename Par4,
           typename Par5,
           typename Par6,
           typename Par7>
 ResultCode CrossCall(IPCProvider& ipc_provider,
                      uint32_t tag,
                      const Par1& p1,
                      const Par2& p2,
                      const Par3& p3,
                      const Par4& p4,
                      const Par5& p5,
                      const Par6& p6,
                      const Par7& p7,
                      CrossCallReturn* answer) {
   XCALL_GEN_PARAMS_OBJ(7, call_params);
   XCALL_GEN_COPY_PARAM(1, call_params);
   XCALL_GEN_COPY_PARAM(2, call_params);
   XCALL_GEN_COPY_PARAM(3, call_params);
   XCALL_GEN_COPY_PARAM(4, call_params);
   XCALL_GEN_COPY_PARAM(5, call_params);
   XCALL_GEN_COPY_PARAM(6, call_params);
   XCALL_GEN_COPY_PARAM(7, call_params);

   ResultCode result = ipc_provider.DoCall(call_params, answer);

   if (SBOX_ERROR_CHANNEL_ERROR != result) {
     XCALL_GEN_UPDATE_PARAM(1, call_params);
     XCALL_GEN_UPDATE_PARAM(2, call_params);
     XCALL_GEN_UPDATE_PARAM(3, call_params);
     XCALL_GEN_UPDATE_PARAM(4, call_params);
     XCALL_GEN_UPDATE_PARAM(5, call_params);
     XCALL_GEN_UPDATE_PARAM(6, call_params);
     XCALL_GEN_UPDATE_PARAM(7, call_params);
     XCALL_GEN_FREE_CHANNEL();
   }
   return result;
 }
 }  // namespace sandbox

 #endif  // SANDBOX_SRC_CROSSCALL_CLIENT_H__
	// Copyright (c) 2012 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_CROSSCALL_CLIENT_H_
	#define SANDBOX_SRC_CROSSCALL_CLIENT_H_

	#include <stddef.h>
	#include <stdint.h>

	#include "base/compiler_specific.h"
	#include "sandbox/win/src/crosscall_params.h"
	#include "sandbox/win/src/sandbox.h"

	// This header defines the CrossCall(..) family of templated functions
	// Their purpose is to simulate the syntax of regular call but to generate
	// and IPC from the client-side.
	//
	// The basic pattern is to
	// 1) use template argument deduction to compute the size of each
	// parameter and the appropriate copy method
	// 2) pack the parameters in the appropriate ActualCallParams< > object
	// 3) call the IPC interface IPCProvider::DoCall( )
	//
	// The general interface of CrossCall is:
	// ResultCode CrossCall(IPCProvider& ipc_provider,
	// uint32_t tag,
	// const Par1& p1, const Par2& p2,...pn
	// CrossCallReturn* answer)
	//
	// where:
	// ipc_provider: is a specific implementation of the ipc transport see
	// sharedmem_ipc_server.h for an example.
	// tag : is the unique id for this IPC call. Is used to route the call to
	// the appropriate service.
	// p1, p2,.. pn : The input parameters of the IPC. Use only simple types
	// and wide strings (can add support for others).
	// answer : If the IPC was successful. The server-side answer is here. The
	// interpretation of the answer is private to client and server.
	//
	// The return value is ALL_OK if the IPC was delivered to the server, other
	// return codes indicate that the IPC transport failed to deliver it.
	namespace sandbox {

	// this is the assumed channel size. This can be overridden in a given
	// IPC implementation.
	const uint32_t kIPCChannelSize = 1024;

	// The copy helper uses templates to deduce the appropriate copy function to
	// copy the input parameters in the buffer that is going to be send across the
	// IPC. These template facility can be made more sophisticated as need arises.

	// The default copy helper. It catches the general case where no other
	// specialized template matches better. We set the type to UINT32_TYPE, so this
	// only works with objects whose size is 32 bits.
	template <typename T>
	class CopyHelper {
	public:
	CopyHelper(const T& t) : t_(t) {}

	// Returns the pointer to the start of the input.
	const void* GetStart() const { return &t_; }

	// Update the stored value with the value in the buffer. This is not
	// supported for this type.
	bool Update(void* buffer) {
	// Not supported;
	return true;
	}

	// Returns the size of the input in bytes.
	uint32_t GetSize() const { return sizeof(T); }

	// Returns true if the current type is used as an In or InOut parameter.
	bool IsInOut() { return false; }

	// Returns this object's type.
	ArgType GetType() {
	static_assert(sizeof(T) == sizeof(uint32_t), "specialization needed");
	return UINT32_TYPE;
	}

	private:
	const T& t_;
	};

	// This copy helper template specialization if for the void pointer
	// case both 32 and 64 bit.
	template <>
	class CopyHelper<void*> {
	public:
	CopyHelper(void* t) : t_(t) {}

	// Returns the pointer to the start of the input.
	const void* GetStart() const { return &t_; }

	// Update the stored value with the value in the buffer. This is not
	// supported for this type.
	bool Update(void* buffer) {
	// Not supported;
	return true;
	}

	// Returns the size of the input in bytes.
	uint32_t GetSize() const { return sizeof(t_); }

	// Returns true if the current type is used as an In or InOut parameter.
	bool IsInOut() { return false; }

	// Returns this object's type.
	ArgType GetType() { return VOIDPTR_TYPE; }

	private:
	const void* t_;
	};

	// This copy helper template specialization catches the cases where the
	// parameter is a pointer to a string.
	template <>
	class CopyHelper<const wchar_t*> {
	public:
	CopyHelper(const wchar_t* t) : t_(t) {}

	// Returns the pointer to the start of the string.
	const void* GetStart() const { return t_; }

	// Update the stored value with the value in the buffer. This is not
	// supported for this type.
	bool Update(void* buffer) {
	// Not supported;
	return true;
	}

	// Returns the size of the string in bytes. We define a nullptr string to
	// be of zero length.
	uint32_t GetSize() const {
	__try {
	return (!t_) ? 0
	: static_cast<uint32_t>(StringLength(t_) * sizeof(t_[0]));
	} __except (EXCEPTION_EXECUTE_HANDLER) {
	return UINT32_MAX;
	}
	}

	// Returns true if the current type is used as an In or InOut parameter.
	bool IsInOut() { return false; }

	ArgType GetType() { return WCHAR_TYPE; }

	private:
	// We provide our not very optimized version of wcslen(), since we don't
	// want to risk having the linker use the version in the CRT since the CRT
	// might not be present when we do an early IPC call.
	static size_t CDECL StringLength(const wchar_t* wcs) {
	const wchar_t* eos = wcs;
	while (*eos++)
	;
	return static_cast<size_t>(eos - wcs - 1);
	}

	const wchar_t* t_;
	};

	// Specialization for non-const strings. We just reuse the implementation of the
	// const string specialization.
	template <>
	class CopyHelper<wchar_t> : public CopyHelper<const wchar_t> {
	public:
	typedef CopyHelper<const wchar_t*> Base;
	CopyHelper(wchar_t* t) : Base(t) {}

	const void* GetStart() const { return Base::GetStart(); }

	bool Update(void* buffer) { return Base::Update(buffer); }

	uint32_t GetSize() const { return Base::GetSize(); }

	bool IsInOut() { return Base::IsInOut(); }

	ArgType GetType() { return Base::GetType(); }
	};

	// Specialization for wchar_t arrays strings. We just reuse the implementation
	// of the const string specialization.
	template <size_t n>
	class CopyHelper<const wchar_t[n]> : public CopyHelper<const wchar_t*> {
	public:
	typedef const wchar_t array[n];
	typedef CopyHelper<const wchar_t*> Base;
	CopyHelper(array t) : Base(t) {}

	const void* GetStart() const { return Base::GetStart(); }

	bool Update(void* buffer) { return Base::Update(buffer); }

	uint32_t GetSize() const { return Base::GetSize(); }

	bool IsInOut() { return Base::IsInOut(); }

	ArgType GetType() { return Base::GetType(); }
	};

	// Generic encapsulation class containing a pointer to a buffer and the
	// size of the buffer. It is used by the IPC to be able to pass in/out
	// parameters.
	class InOutCountedBuffer : public CountedBuffer {
	public:
	InOutCountedBuffer(void* buffer, uint32_t size)
	: CountedBuffer(buffer, size) {}
	};

	// This copy helper template specialization catches the cases where the
	// parameter is a an input/output buffer.
	template <>
	class CopyHelper<InOutCountedBuffer> {
	public:
	CopyHelper(const InOutCountedBuffer t) : t_(t) {}

	// Returns the pointer to the start of the string.
	const void* GetStart() const { return t_.Buffer(); }

	// Updates the buffer with the value from the new buffer in parameter.
	bool Update(void* buffer) {
	// We are touching user memory, this has to be done from inside a try
	// except.
	__try {
	memcpy(t_.Buffer(), buffer, t_.Size());
	} __except (EXCEPTION_EXECUTE_HANDLER) {
	return false;
	}
	return true;
	}

	// Returns the size of the string in bytes. We define a nullptr string to
	// be of zero length.
	uint32_t GetSize() const { return t_.Size(); }

	// Returns true if the current type is used as an In or InOut parameter.
	bool IsInOut() { return true; }

	ArgType GetType() { return INOUTPTR_TYPE; }

	private:
	const InOutCountedBuffer t_;
	};

	// The following two macros make it less error prone the generation
	// of CrossCall functions with ever more input parameters.

	#define XCALL_GEN_PARAMS_OBJ(num, params) \
	typedef ActualCallParams<num, kIPCChannelSize> ActualParams; \
	void* raw_mem = ipc_provider.GetBuffer(); \
	if (!raw_mem) \
	return SBOX_ERROR_NO_SPACE; \
	ActualParams* params = new (raw_mem) ActualParams(tag);

	#define XCALL_GEN_COPY_PARAM(num, params) \
	static_assert(kMaxIpcParams >= num, "too many parameters"); \
	CopyHelper<Par##num> ch##num(p##num); \
	if (!params->CopyParamIn(num - 1, ch##num.GetStart(), ch##num.GetSize(), \
	ch##num.IsInOut(), ch##num.GetType())) \
	return SBOX_ERROR_NO_SPACE;

	#define XCALL_GEN_UPDATE_PARAM(num, params) \
	if (!ch##num.Update(params->GetParamPtr(num - 1))) { \
	ipc_provider.FreeBuffer(raw_mem); \
	return SBOX_ERROR_BAD_PARAMS; \
	}

	#define XCALL_GEN_FREE_CHANNEL() ipc_provider.FreeBuffer(raw_mem);

	// CrossCall template with one input parameter
	template <typename IPCProvider, typename Par1>
	ResultCode CrossCall(IPCProvider& ipc_provider,
	uint32_t tag,
	const Par1& p1,
	CrossCallReturn* answer) {
	XCALL_GEN_PARAMS_OBJ(1, call_params);
	XCALL_GEN_COPY_PARAM(1, call_params);

	ResultCode result = ipc_provider.DoCall(call_params, answer);

	if (SBOX_ERROR_CHANNEL_ERROR != result) {
	XCALL_GEN_UPDATE_PARAM(1, call_params);
	XCALL_GEN_FREE_CHANNEL();
	}

	return result;
	}

	// CrossCall template with two input parameters.
	template <typename IPCProvider, typename Par1, typename Par2>
	ResultCode CrossCall(IPCProvider& ipc_provider,
	uint32_t tag,
	const Par1& p1,
	const Par2& p2,
	CrossCallReturn* answer) {
	XCALL_GEN_PARAMS_OBJ(2, call_params);
	XCALL_GEN_COPY_PARAM(1, call_params);
	XCALL_GEN_COPY_PARAM(2, call_params);

	ResultCode result = ipc_provider.DoCall(call_params, answer);

	if (SBOX_ERROR_CHANNEL_ERROR != result) {
	XCALL_GEN_UPDATE_PARAM(1, call_params);
	XCALL_GEN_UPDATE_PARAM(2, call_params);
	XCALL_GEN_FREE_CHANNEL();
	}
	return result;
	}

	// CrossCall template with three input parameters.
	template <typename IPCProvider, typename Par1, typename Par2, typename Par3>
	ResultCode CrossCall(IPCProvider& ipc_provider,
	uint32_t tag,
	const Par1& p1,
	const Par2& p2,
	const Par3& p3,
	CrossCallReturn* answer) {
	XCALL_GEN_PARAMS_OBJ(3, call_params);
	XCALL_GEN_COPY_PARAM(1, call_params);
	XCALL_GEN_COPY_PARAM(2, call_params);
	XCALL_GEN_COPY_PARAM(3, call_params);

	ResultCode result = ipc_provider.DoCall(call_params, answer);

	if (SBOX_ERROR_CHANNEL_ERROR != result) {
	XCALL_GEN_UPDATE_PARAM(1, call_params);
	XCALL_GEN_UPDATE_PARAM(2, call_params);
	XCALL_GEN_UPDATE_PARAM(3, call_params);
	XCALL_GEN_FREE_CHANNEL();
	}
	return result;
	}

	// CrossCall template with four input parameters.
	template <typename IPCProvider,
	typename Par1,
	typename Par2,
	typename Par3,
	typename Par4>
	ResultCode CrossCall(IPCProvider& ipc_provider,
	uint32_t tag,
	const Par1& p1,
	const Par2& p2,
	const Par3& p3,
	const Par4& p4,
	CrossCallReturn* answer) {
	XCALL_GEN_PARAMS_OBJ(4, call_params);
	XCALL_GEN_COPY_PARAM(1, call_params);
	XCALL_GEN_COPY_PARAM(2, call_params);
	XCALL_GEN_COPY_PARAM(3, call_params);
	XCALL_GEN_COPY_PARAM(4, call_params);

	ResultCode result = ipc_provider.DoCall(call_params, answer);

	if (SBOX_ERROR_CHANNEL_ERROR != result) {
	XCALL_GEN_UPDATE_PARAM(1, call_params);
	XCALL_GEN_UPDATE_PARAM(2, call_params);
	XCALL_GEN_UPDATE_PARAM(3, call_params);
	XCALL_GEN_UPDATE_PARAM(4, call_params);
	XCALL_GEN_FREE_CHANNEL();
	}
	return result;
	}

	// CrossCall template with five input parameters.
	template <typename IPCProvider,
	typename Par1,
	typename Par2,
	typename Par3,
	typename Par4,
	typename Par5>
	ResultCode CrossCall(IPCProvider& ipc_provider,
	uint32_t tag,
	const Par1& p1,
	const Par2& p2,
	const Par3& p3,
	const Par4& p4,
	const Par5& p5,
	CrossCallReturn* answer) {
	XCALL_GEN_PARAMS_OBJ(5, call_params);
	XCALL_GEN_COPY_PARAM(1, call_params);
	XCALL_GEN_COPY_PARAM(2, call_params);
	XCALL_GEN_COPY_PARAM(3, call_params);
	XCALL_GEN_COPY_PARAM(4, call_params);
	XCALL_GEN_COPY_PARAM(5, call_params);

	ResultCode result = ipc_provider.DoCall(call_params, answer);

	if (SBOX_ERROR_CHANNEL_ERROR != result) {
	XCALL_GEN_UPDATE_PARAM(1, call_params);
	XCALL_GEN_UPDATE_PARAM(2, call_params);
	XCALL_GEN_UPDATE_PARAM(3, call_params);
	XCALL_GEN_UPDATE_PARAM(4, call_params);
	XCALL_GEN_UPDATE_PARAM(5, call_params);
	XCALL_GEN_FREE_CHANNEL();
	}
	return result;
	}

	// CrossCall template with six input parameters.
	template <typename IPCProvider,
	typename Par1,
	typename Par2,
	typename Par3,
	typename Par4,
	typename Par5,
	typename Par6>
	ResultCode CrossCall(IPCProvider& ipc_provider,
	uint32_t tag,
	const Par1& p1,
	const Par2& p2,
	const Par3& p3,
	const Par4& p4,
	const Par5& p5,
	const Par6& p6,
	CrossCallReturn* answer) {
	XCALL_GEN_PARAMS_OBJ(6, call_params);
	XCALL_GEN_COPY_PARAM(1, call_params);
	XCALL_GEN_COPY_PARAM(2, call_params);
	XCALL_GEN_COPY_PARAM(3, call_params);
	XCALL_GEN_COPY_PARAM(4, call_params);
	XCALL_GEN_COPY_PARAM(5, call_params);
	XCALL_GEN_COPY_PARAM(6, call_params);

	ResultCode result = ipc_provider.DoCall(call_params, answer);

	if (SBOX_ERROR_CHANNEL_ERROR != result) {
	XCALL_GEN_UPDATE_PARAM(1, call_params);
	XCALL_GEN_UPDATE_PARAM(2, call_params);
	XCALL_GEN_UPDATE_PARAM(3, call_params);
	XCALL_GEN_UPDATE_PARAM(4, call_params);
	XCALL_GEN_UPDATE_PARAM(5, call_params);
	XCALL_GEN_UPDATE_PARAM(6, call_params);
	XCALL_GEN_FREE_CHANNEL();
	}
	return result;
	}

	// CrossCall template with seven input parameters.
	template <typename IPCProvider,
	typename Par1,
	typename Par2,
	typename Par3,
	typename Par4,
	typename Par5,
	typename Par6,
	typename Par7>
	ResultCode CrossCall(IPCProvider& ipc_provider,
	uint32_t tag,
	const Par1& p1,
	const Par2& p2,
	const Par3& p3,
	const Par4& p4,
	const Par5& p5,
	const Par6& p6,
	const Par7& p7,
	CrossCallReturn* answer) {
	XCALL_GEN_PARAMS_OBJ(7, call_params);
	XCALL_GEN_COPY_PARAM(1, call_params);
	XCALL_GEN_COPY_PARAM(2, call_params);
	XCALL_GEN_COPY_PARAM(3, call_params);
	XCALL_GEN_COPY_PARAM(4, call_params);
	XCALL_GEN_COPY_PARAM(5, call_params);
	XCALL_GEN_COPY_PARAM(6, call_params);
	XCALL_GEN_COPY_PARAM(7, call_params);

	ResultCode result = ipc_provider.DoCall(call_params, answer);

	if (SBOX_ERROR_CHANNEL_ERROR != result) {
	XCALL_GEN_UPDATE_PARAM(1, call_params);
	XCALL_GEN_UPDATE_PARAM(2, call_params);
	XCALL_GEN_UPDATE_PARAM(3, call_params);
	XCALL_GEN_UPDATE_PARAM(4, call_params);
	XCALL_GEN_UPDATE_PARAM(5, call_params);
	XCALL_GEN_UPDATE_PARAM(6, call_params);
	XCALL_GEN_UPDATE_PARAM(7, call_params);
	XCALL_GEN_FREE_CHANNEL();
	}
	return result;
	}
	} // namespace sandbox

	#endif // SANDBOX_SRC_CROSSCALL_CLIENT_H__