Kernel/IPC: Use Ports and Sessions as the fundamental building block of Inter Process Communication.

All handles obtained via srv::GetServiceHandle or svcConnectToPort are references to ClientSessions.
Service modules will wait on the counterpart of those ClientSessions (Called ServerSessions) using svcReplyAndReceive or svcWaitSynchronization[1|N], and will be awoken when a SyncRequest is performed.

HLE Interfaces are now ClientPorts which override the HandleSyncRequest virtual member function to perform command handling immediately.

src/core/hle/kernel/client_port.cpp

@@ -6,10 +6,17 @@
 #include "core/hle/kernel/client_port.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/server_port.h"
+#include "core/hle/kernel/server_session.h"
 
 namespace Kernel {
 
 ClientPort::ClientPort() {}
 ClientPort::~ClientPort() {}
 
+void ClientPort::AddWaitingSession(SharedPtr<ServerSession> server_session) {
+    server_port->pending_sessions.push_back(server_session);
+    // Wake the threads waiting on the ServerPort
+    server_port->WakeupAllWaitingThreads();
+}
+
 } // namespace

src/core/hle/kernel/client_port.h

@@ -11,16 +11,27 @@
 namespace Kernel {
 
 class ServerPort;
+class ServerSession;
 
 class ClientPort : public Object {
 public:
     friend class ServerPort;
-    std::string GetTypeName() const override {
-        return "ClientPort";
-    }
-    std::string GetName() const override {
-        return name;
-    }
+
+    /**
+     * Adds the specified server session to the queue of pending sessions of the associated ServerPort
+     * @param server_session Server session to add to the queue
+     */
+    virtual void AddWaitingSession(SharedPtr<ServerSession> server_session);
+
+    /**
+     * Handle a sync request from the emulated application.
+     * Only HLE services should override this function.
+     * @returns ResultCode from the operation.
+     */
+    virtual ResultCode HandleSyncRequest() { return RESULT_SUCCESS; }
+
+    std::string GetTypeName() const override { return "ClientPort"; }
+    std::string GetName() const override { return name; }
 
     static const HandleType HANDLE_TYPE = HandleType::ClientPort;
     HandleType GetHandleType() const override {

src/core/hle/kernel/client_session.cpp

@@ -0,0 +1,42 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include "common/assert.h"
+
+#include "core/hle/kernel/client_port.h"
+#include "core/hle/kernel/client_session.h"
+#include "core/hle/kernel/server_session.h"
+#include "core/hle/kernel/kernel.h"
+
+namespace Kernel {
+
+ClientSession::ClientSession() {}
+ClientSession::~ClientSession() {}
+
+ResultVal<SharedPtr<ClientSession>> ClientSession::Create(SharedPtr<ServerSession> server_session, SharedPtr<ClientPort> client_port, std::string name) {
+    SharedPtr<ClientSession> client_session(new ClientSession);
+
+    client_session->name = std::move(name);
+    client_session->server_session = server_session;
+    client_session->client_port = client_port;
+
+    return MakeResult<SharedPtr<ClientSession>>(std::move(client_session));
+}
+
+ResultCode ClientSession::HandleSyncRequest() {
+    // Signal the server session that new data is available
+    ResultCode result = server_session->HandleSyncRequest();
+
+    if (result.IsError())
+        return result;
+
+    // Tell the client port to handle the request in case it's an HLE service.
+    // The client port can be nullptr for port-less sessions (Like for example File and Directory sessions).
+    if (client_port != nullptr)
+        result = client_port->HandleSyncRequest();
+
+    return result;
+}
+
+} // namespace

src/core/hle/kernel/client_session.h

@@ -0,0 +1,50 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <string>
+
+#include "common/common_types.h"
+
+#include "core/hle/kernel/kernel.h"
+
+namespace Kernel {
+
+class ClientPort;
+class ServerSession;
+
+class ClientSession final : public Object {
+public:
+    /**
+     * Creates a client session.
+     * @param server_session The server session associated with this client session
+     * @param client_port The client port which this session is connected to
+     * @param name Optional name of client session
+     * @return The created client session
+     */
+    static ResultVal<SharedPtr<ClientSession>> Create(SharedPtr<ServerSession> server_session, SharedPtr<ClientPort> client_port, std::string name = "Unknown");
+
+    std::string GetTypeName() const override { return "ClientSession"; }
+    std::string GetName() const override { return name; }
+
+    static const HandleType HANDLE_TYPE = HandleType::ClientSession;
+    HandleType GetHandleType() const override { return HANDLE_TYPE; }
+
+    /**
+     * Handle a SyncRequest from the emulated application.
+     * @return ResultCode of the operation.
+     */
+    ResultCode HandleSyncRequest();
+
+    std::string name;                           ///< Name of client port (optional)
+    SharedPtr<ServerSession> server_session;    ///< The server session associated with this client session.
+    SharedPtr<ClientPort> client_port;          ///< The client port which this session is connected to.
+
+private:
+    ClientSession();
+    ~ClientSession() override;
+};
+
+} // namespace

src/core/hle/kernel/kernel.h

@@ -31,22 +31,24 @@ enum KernelHandle : Handle {
 };
 
 enum class HandleType : u32 {
-    Unknown = 0,
+    Unknown         = 0,
 
-    Session = 2,
-    Event = 3,
-    Mutex = 4,
-    SharedMemory = 5,
-    Redirection = 6,
-    Thread = 7,
-    Process = 8,
-    AddressArbiter = 9,
-    Semaphore = 10,
-    Timer = 11,
-    ResourceLimit = 12,
-    CodeSet = 13,
-    ClientPort = 14,
-    ServerPort = 15,
+
+    Event           = 3,
+    Mutex           = 4,
+    SharedMemory    = 5,
+    Redirection     = 6,
+    Thread          = 7,
+    Process         = 8,
+    AddressArbiter  = 9,
+    Semaphore       = 10,
+    Timer           = 11,
+    ResourceLimit   = 12,
+    CodeSet         = 13,
+    ClientPort      = 14,
+    ServerPort      = 15,
+    ClientSession   = 16,
+    ServerSession   = 17,
 };
 
 enum {
@@ -82,7 +84,7 @@ public:
      */
     bool IsWaitable() const {
         switch (GetHandleType()) {
-        case HandleType::Session:
+        case HandleType::ServerSession:
         case HandleType::ServerPort:
         case HandleType::Event:
         case HandleType::Mutex:

src/core/hle/kernel/server_session.cpp

@@ -0,0 +1,58 @@
+// Copyright 2016 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <tuple>
+
+#include "core/hle/kernel/client_port.h"
+#include "core/hle/kernel/client_session.h"
+#include "core/hle/kernel/server_session.h"
+#include "core/hle/kernel/thread.h"
+
+namespace Kernel {
+
+ServerSession::ServerSession() {}
+ServerSession::~ServerSession() {}
+
+ResultVal<SharedPtr<ServerSession>> ServerSession::Create(std::string name) {
+    SharedPtr<ServerSession> server_session(new ServerSession);
+
+    server_session->name = std::move(name);
+    server_session->signaled = false;
+
+    return MakeResult<SharedPtr<ServerSession>>(std::move(server_session));
+}
+
+bool ServerSession::ShouldWait() {
+    return !signaled;
+}
+
+void ServerSession::Acquire() {
+    ASSERT_MSG(!ShouldWait(), "object unavailable!");
+    signaled = false;
+}
+
+ResultCode ServerSession::HandleSyncRequest() {
+    // The ServerSession received a sync request, this means that there's new data available
+    // from one of its ClientSessions, so wake up any threads that may be waiting on a svcReplyAndReceive or similar.
+    signaled = true;
+    WakeupAllWaitingThreads();
+    return RESULT_SUCCESS;
+}
+
+SharedPtr<ClientSession> ServerSession::CreateClientSession() {
+    // In Citra, some types of ServerSessions (File and Directory sessions) are not created as a pair of Server-Client sessions,
+    // but are instead created as a single ServerSession, which then hands over a ClientSession on demand (When opening the File or Directory).
+    // The real kernel (Or more specifically, the real FS service) does create the pair of Sessions at the same time (via svcCreateSession), and simply
+    // stores the ClientSession until it is needed.
+    return ClientSession::Create(SharedPtr<ServerSession>(this), nullptr, name + "Client").MoveFrom();
+}
+
+std::tuple<SharedPtr<ServerSession>, SharedPtr<ClientSession>> ServerSession::CreateSessionPair(SharedPtr<ClientPort> client_port, std::string name) {
+    auto server_session = ServerSession::Create(name + "Server").MoveFrom();
+    auto client_session = ClientSession::Create(server_session, client_port, name + "Client").MoveFrom();
+
+    return std::make_tuple(server_session, client_session);
+}
+
+}

src/core/hle/kernel/server_session.h

@@ -162,57 +162,64 @@ inline u32* GetCommandBuffer(const int offset = 0) {
                                     offset);
 }
 
+class ClientSession;
+class ClientPort;
+
 /**
- * Kernel object representing the client endpoint of an IPC session. Sessions are the basic CTR-OS
+ * Kernel object representing the server endpoint of an IPC session. Sessions are the basic CTR-OS
  * primitive for communication between different processes, and are used to implement service calls
  * to the various system services.
  *
  * To make a service call, the client must write the command header and parameters to the buffer
  * located at offset 0x80 of the TLS (Thread-Local Storage) area, then execute a SendSyncRequest
- * SVC call with its Session handle. The kernel will read the command header, using it to marshall
+ * SVC call with its ClientSession handle. The kernel will read the command header, using it to marshall
  * the parameters to the process at the server endpoint of the session. After the server replies to
  * the request, the response is marshalled back to the caller's TLS buffer and control is
  * transferred back to it.
- *
- * In Citra, only the client endpoint is currently implemented and only HLE calls, where the IPC
- * request is answered by C++ code in the emulator, are supported. When SendSyncRequest is called
- * with the session handle, this class's SyncRequest method is called, which should read the TLS
- * buffer and emulate the call accordingly. Since the code can directly read the emulated memory,
- * no parameter marshalling is done.
- *
- * In the long term, this should be turned into the full-fledged IPC mechanism implemented by
- * CTR-OS so that IPC calls can be optionally handled by the real implementations of processes, as
- * opposed to HLE simulations.
  */
-class Session : public WaitObject {
+class ServerSession : public WaitObject {
 public:
-    Session();
-    ~Session() override;
-
-    std::string GetTypeName() const override {
-        return "Session";
-    }
-
-    static const HandleType HANDLE_TYPE = HandleType::Session;
-    HandleType GetHandleType() const override {
-        return HANDLE_TYPE;
-    }
+    ServerSession();
+    ~ServerSession() override;
 
     /**
-     * Handles a synchronous call to this session using HLE emulation. Emulated <-> emulated calls
-     * aren't supported yet.
+     * Creates a server session.
+     * @param name Optional name of the server session
+     * @return The created server session
      */
-    virtual ResultVal<bool> SyncRequest() = 0;
+    static ResultVal<SharedPtr<ServerSession>> Create(std::string name = "Unknown");
 
-    // TODO(bunnei): These functions exist to satisfy a hardware test with a Session object
-    // passed into WaitSynchronization. Figure out the meaning of them.
+    std::string GetTypeName() const override { return "ServerSession"; }
 
-    bool ShouldWait() override {
-        return true;
-    }
+    static const HandleType HANDLE_TYPE = HandleType::ServerSession;
+    HandleType GetHandleType() const override { return HANDLE_TYPE; }
 
-    void Acquire() override {
-        ASSERT_MSG(!ShouldWait(), "object unavailable!");
-    }
+    /**
+     * Creates a pair of ServerSession and an associated ClientSession.
+     * @param client_port ClientPort to which the sessions are connected
+     * @param name Optional name of the ports
+     * @return The created session tuple
+     */
+    static std::tuple<SharedPtr<ServerSession>, SharedPtr<ClientSession>> CreateSessionPair(SharedPtr<ClientPort> client_port, std::string name = "Unknown");
+
+    /**
+     * Creates a portless ClientSession and associates it with this ServerSession.
+     * @returns ClientSession The newly created ClientSession.
+     */
+    SharedPtr<ClientSession> CreateClientSession();
+
+    /**
+     * Handle a sync request from the emulated application.
+     * Only HLE services should override this function.
+     * @returns ResultCode from the operation.
+     */
+    virtual ResultCode HandleSyncRequest();
+
+    bool ShouldWait() override;
+
+    void Acquire() override;
+
+    std::string name; ///< The name of this session (optional)
+    bool signaled;    ///< Whether there's new data available to this ServerSession
 };
 }