kernel: implement light IPC

src/core/CMakeLists.txt

@@ -251,10 +251,16 @@ add_library(core STATIC
     hle/kernel/k_hardware_timer.h
     hle/kernel/k_interrupt_manager.cpp
     hle/kernel/k_interrupt_manager.h
+    hle/kernel/k_light_client_session.cpp
+    hle/kernel/k_light_client_session.h
     hle/kernel/k_light_condition_variable.cpp
     hle/kernel/k_light_condition_variable.h
     hle/kernel/k_light_lock.cpp
     hle/kernel/k_light_lock.h
+    hle/kernel/k_light_server_session.cpp
+    hle/kernel/k_light_server_session.h
+    hle/kernel/k_light_session.cpp
+    hle/kernel/k_light_session.h
     hle/kernel/k_memory_block.h
     hle/kernel/k_memory_block_manager.cpp
     hle/kernel/k_memory_block_manager.h

src/core/hle/kernel/k_client_port.cpp

@@ -3,6 +3,7 @@
 
 #include "common/scope_exit.h"
 #include "core/hle/kernel/k_client_port.h"
+#include "core/hle/kernel/k_light_session.h"
 #include "core/hle/kernel/k_port.h"
 #include "core/hle/kernel/k_scheduler.h"
 #include "core/hle/kernel/k_scoped_resource_reservation.h"
@@ -63,6 +64,7 @@ Result KClientPort::CreateSession(KClientSession** out) {
     R_UNLESS(session_reservation.Succeeded(), ResultLimitReached);
 
     // Allocate a session normally.
+    // TODO: Dynamic resource limits
     session = KSession::Create(m_kernel);
 
     // Check that we successfully created a session.
@@ -119,4 +121,71 @@ Result KClientPort::CreateSession(KClientSession** out) {
     R_SUCCEED();
 }
 
+Result KClientPort::CreateLightSession(KLightClientSession** out) {
+    // Declare the session we're going to allocate.
+    KLightSession* session{};
+
+    // Reserve a new session from the resource limit.
+    KScopedResourceReservation session_reservation(GetCurrentProcessPointer(m_kernel),
+                                                   Svc::LimitableResource::SessionCountMax);
+    R_UNLESS(session_reservation.Succeeded(), ResultLimitReached);
+
+    // Allocate a session normally.
+    // TODO: Dynamic resource limits
+    session = KLightSession::Create(m_kernel);
+
+    // Check that we successfully created a session.
+    R_UNLESS(session != nullptr, ResultOutOfResource);
+
+    // Update the session counts.
+    {
+        ON_RESULT_FAILURE {
+            session->Close();
+        };
+
+        // Atomically increment the number of sessions.
+        s32 new_sessions;
+        {
+            const auto max = m_max_sessions;
+            auto cur_sessions = m_num_sessions.load(std::memory_order_acquire);
+            do {
+                R_UNLESS(cur_sessions < max, ResultOutOfSessions);
+                new_sessions = cur_sessions + 1;
+            } while (!m_num_sessions.compare_exchange_weak(cur_sessions, new_sessions,
+                                                           std::memory_order_relaxed));
+        }
+
+        // Atomically update the peak session tracking.
+        {
+            auto peak = m_peak_sessions.load(std::memory_order_acquire);
+            do {
+                if (peak >= new_sessions) {
+                    break;
+                }
+            } while (!m_peak_sessions.compare_exchange_weak(peak, new_sessions,
+                                                            std::memory_order_relaxed));
+        }
+    }
+
+    // Initialize the session.
+    session->Initialize(this, m_parent->GetName());
+
+    // Commit the session reservation.
+    session_reservation.Commit();
+
+    // Register the session.
+    KLightSession::Register(m_kernel, session);
+    ON_RESULT_FAILURE {
+        session->GetClientSession().Close();
+        session->GetServerSession().Close();
+    };
+
+    // Enqueue the session with our parent.
+    R_TRY(m_parent->EnqueueSession(std::addressof(session->GetServerSession())));
+
+    // We succeeded, so set the output.
+    *out = std::addressof(session->GetClientSession());
+    R_SUCCEED();
+}
+
 } // namespace Kernel

src/core/hle/kernel/k_client_port.h

@@ -11,6 +11,7 @@
 
 namespace Kernel {
 
+class KLightClientSession;
 class KClientSession;
 class KernelCore;
 class KPort;
@@ -51,6 +52,7 @@ public:
     bool IsSignaled() const override;
 
     Result CreateSession(KClientSession** out);
+    Result CreateLightSession(KLightClientSession** out);
 
 private:
     std::atomic<s32> m_num_sessions{};

src/core/hle/kernel/k_light_client_session.cpp

@@ -0,0 +1,31 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/hle/kernel/k_light_client_session.h"
+#include "core/hle/kernel/k_light_session.h"
+#include "core/hle/kernel/k_thread.h"
+
+namespace Kernel {
+
+KLightClientSession::KLightClientSession(KernelCore& kernel) : KAutoObject(kernel) {}
+
+KLightClientSession::~KLightClientSession() = default;
+
+void KLightClientSession::Destroy() {
+    m_parent->OnClientClosed();
+}
+
+void KLightClientSession::OnServerClosed() {}
+
+Result KLightClientSession::SendSyncRequest(u32* data) {
+    // Get the request thread.
+    KThread* cur_thread = GetCurrentThreadPointer(m_kernel);
+
+    // Set the light data.
+    cur_thread->SetLightSessionData(data);
+
+    // Send the request.
+    R_RETURN(m_parent->OnRequest(cur_thread));
+}
+
+} // namespace Kernel

src/core/hle/kernel/k_light_client_session.h

@@ -0,0 +1,39 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/hle/kernel/k_auto_object.h"
+#include "core/hle/result.h"
+
+namespace Kernel {
+
+class KLightSession;
+
+class KLightClientSession final : public KAutoObject {
+    KERNEL_AUTOOBJECT_TRAITS(KLightClientSession, KAutoObject);
+
+public:
+    explicit KLightClientSession(KernelCore& kernel);
+    ~KLightClientSession();
+
+    void Initialize(KLightSession* parent) {
+        // Set member variables.
+        m_parent = parent;
+    }
+
+    virtual void Destroy() override;
+
+    const KLightSession* GetParent() const {
+        return m_parent;
+    }
+
+    Result SendSyncRequest(u32* data);
+
+    void OnServerClosed();
+
+private:
+    KLightSession* m_parent;
+};
+
+} // namespace Kernel

src/core/hle/kernel/k_light_server_session.cpp

@@ -0,0 +1,247 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/hle/kernel/k_light_server_session.h"
+#include "core/hle/kernel/k_light_session.h"
+#include "core/hle/kernel/k_thread.h"
+#include "core/hle/kernel/k_thread_queue.h"
+#include "core/hle/kernel/svc_results.h"
+
+namespace Kernel {
+
+namespace {
+
+constexpr u64 InvalidThreadId = std::numeric_limits<u64>::max();
+
+class ThreadQueueImplForKLightServerSessionRequest final : public KThreadQueue {
+private:
+    KThread::WaiterList* m_wait_list;
+
+public:
+    ThreadQueueImplForKLightServerSessionRequest(KernelCore& kernel, KThread::WaiterList* wl)
+        : KThreadQueue(kernel), m_wait_list(wl) {}
+
+    virtual void EndWait(KThread* waiting_thread, Result wait_result) override {
+        // Remove the thread from our wait list.
+        m_wait_list->erase(m_wait_list->iterator_to(*waiting_thread));
+
+        // Invoke the base end wait handler.
+        KThreadQueue::EndWait(waiting_thread, wait_result);
+    }
+
+    virtual void CancelWait(KThread* waiting_thread, Result wait_result,
+                            bool cancel_timer_task) override {
+        // Remove the thread from our wait list.
+        m_wait_list->erase(m_wait_list->iterator_to(*waiting_thread));
+
+        // Invoke the base cancel wait handler.
+        KThreadQueue::CancelWait(waiting_thread, wait_result, cancel_timer_task);
+    }
+};
+
+class ThreadQueueImplForKLightServerSessionReceive final : public KThreadQueue {
+private:
+    KThread** m_server_thread;
+
+public:
+    ThreadQueueImplForKLightServerSessionReceive(KernelCore& kernel, KThread** st)
+        : KThreadQueue(kernel), m_server_thread(st) {}
+
+    virtual void EndWait(KThread* waiting_thread, Result wait_result) override {
+        // Clear the server thread.
+        *m_server_thread = nullptr;
+
+        // Set the waiting thread as not cancelable.
+        waiting_thread->ClearCancellable();
+
+        // Invoke the base end wait handler.
+        KThreadQueue::EndWait(waiting_thread, wait_result);
+    }
+
+    virtual void CancelWait(KThread* waiting_thread, Result wait_result,
+                            bool cancel_timer_task) override {
+        // Clear the server thread.
+        *m_server_thread = nullptr;
+
+        // Set the waiting thread as not cancelable.
+        waiting_thread->ClearCancellable();
+
+        // Invoke the base cancel wait handler.
+        KThreadQueue::CancelWait(waiting_thread, wait_result, cancel_timer_task);
+    }
+};
+
+} // namespace
+
+KLightServerSession::KLightServerSession(KernelCore& kernel) : KAutoObject(kernel) {}
+KLightServerSession::~KLightServerSession() = default;
+
+void KLightServerSession::Destroy() {
+    this->CleanupRequests();
+
+    m_parent->OnServerClosed();
+}
+
+void KLightServerSession::OnClientClosed() {
+    this->CleanupRequests();
+}
+
+Result KLightServerSession::OnRequest(KThread* request_thread) {
+    ThreadQueueImplForKLightServerSessionRequest wait_queue(m_kernel,
+                                                            std::addressof(m_request_list));
+
+    // Send the request.
+    {
+        // Lock the scheduler.
+        KScopedSchedulerLock sl(m_kernel);
+
+        // Check that the server isn't closed.
+        R_UNLESS(!m_parent->IsServerClosed(), ResultSessionClosed);
+
+        // Check that the request thread isn't terminating.
+        R_UNLESS(!request_thread->IsTerminationRequested(), ResultTerminationRequested);
+
+        // Add the request thread to our list.
+        m_request_list.push_back(*request_thread);
+
+        // Begin waiting on the request.
+        request_thread->SetWaitReasonForDebugging(ThreadWaitReasonForDebugging::IPC);
+        request_thread->BeginWait(std::addressof(wait_queue));
+
+        // If we have a server thread, end its wait.
+        if (m_server_thread != nullptr) {
+            m_server_thread->EndWait(ResultSuccess);
+        }
+    }
+
+    // NOTE: Nintendo returns GetCurrentThread().GetWaitResult() here.
+    // This is technically incorrect, although it doesn't cause problems in practice
+    // because this is only ever called with request_thread = GetCurrentThreadPointer().
+    R_RETURN(request_thread->GetWaitResult());
+}
+
+Result KLightServerSession::ReplyAndReceive(u32* data) {
+    // Set the server context.
+    GetCurrentThread(m_kernel).SetLightSessionData(data);
+
+    // Reply, if we need to.
+    if (data[0] & KLightSession::ReplyFlag) {
+        KScopedSchedulerLock sl(m_kernel);
+
+        // Check that we're open.
+        R_UNLESS(!m_parent->IsClientClosed(), ResultSessionClosed);
+        R_UNLESS(!m_parent->IsServerClosed(), ResultSessionClosed);
+
+        // Check that we have a request to reply to.
+        R_UNLESS(m_current_request != nullptr, ResultInvalidState);
+
+        // Check that the server thread id is correct.
+        R_UNLESS(m_server_thread_id == GetCurrentThread(m_kernel).GetId(), ResultInvalidState);
+
+        // If we can reply, do so.
+        if (!m_current_request->IsTerminationRequested()) {
+            std::memcpy(m_current_request->GetLightSessionData(),
+                        GetCurrentThread(m_kernel).GetLightSessionData(), KLightSession::DataSize);
+            m_current_request->EndWait(ResultSuccess);
+        }
+
+        // Close our current request.
+        m_current_request->Close();
+
+        // Clear our current request.
+        m_current_request = nullptr;
+        m_server_thread_id = InvalidThreadId;
+    }
+
+    // Create the wait queue for our receive.
+    ThreadQueueImplForKLightServerSessionReceive wait_queue(m_kernel,
+                                                            std::addressof(m_server_thread));
+
+    // Receive.
+    while (true) {
+        // Try to receive a request.
+        {
+            KScopedSchedulerLock sl(m_kernel);
+
+            // Check that we aren't already receiving.
+            R_UNLESS(m_server_thread == nullptr, ResultInvalidState);
+            R_UNLESS(m_server_thread_id == InvalidThreadId, ResultInvalidState);
+
+            // Check that we're open.
+            R_UNLESS(!m_parent->IsClientClosed(), ResultSessionClosed);
+            R_UNLESS(!m_parent->IsServerClosed(), ResultSessionClosed);
+
+            // Check that we're not terminating.
+            R_UNLESS(!GetCurrentThread(m_kernel).IsTerminationRequested(),
+                     ResultTerminationRequested);
+
+            // If we have a request available, use it.
+            if (auto head = m_request_list.begin(); head != m_request_list.end()) {
+                // Set our current request.
+                m_current_request = std::addressof(*head);
+                m_current_request->Open();
+
+                // Set our server thread id.
+                m_server_thread_id = GetCurrentThread(m_kernel).GetId();
+
+                // Copy the client request data.
+                std::memcpy(GetCurrentThread(m_kernel).GetLightSessionData(),
+                            m_current_request->GetLightSessionData(), KLightSession::DataSize);
+
+                // We successfully received.
+                R_SUCCEED();
+            }
+
+            // We need to wait for a request to come in.
+
+            // Check if we were cancelled.
+            if (GetCurrentThread(m_kernel).IsWaitCancelled()) {
+                GetCurrentThread(m_kernel).ClearWaitCancelled();
+                R_THROW(ResultCancelled);
+            }
+
+            // Mark ourselves as cancellable.
+            GetCurrentThread(m_kernel).SetCancellable();
+
+            // Wait for a request to come in.
+            m_server_thread = GetCurrentThreadPointer(m_kernel);
+            GetCurrentThread(m_kernel).SetWaitReasonForDebugging(ThreadWaitReasonForDebugging::IPC);
+            GetCurrentThread(m_kernel).BeginWait(std::addressof(wait_queue));
+        }
+
+        // We waited to receive a request; if our wait failed, return the failing result.
+        R_TRY(GetCurrentThread(m_kernel).GetWaitResult());
+    }
+}
+
+void KLightServerSession::CleanupRequests() {
+    // Cleanup all pending requests.
+    {
+        KScopedSchedulerLock sl(m_kernel);
+
+        // Handle the current request.
+        if (m_current_request != nullptr) {
+            // Reply to the current request.
+            if (!m_current_request->IsTerminationRequested()) {
+                m_current_request->EndWait(ResultSessionClosed);
+            }
+
+            // Clear our current request.
+            m_current_request->Close();
+            m_current_request = nullptr;
+            m_server_thread_id = InvalidThreadId;
+        }
+
+        // Reply to all other requests.
+        for (auto& thread : m_request_list) {
+            thread.EndWait(ResultSessionClosed);
+        }
+
+        // Wait up our server thread, if we have one.
+        if (m_server_thread != nullptr) {
+            m_server_thread->EndWait(ResultSessionClosed);
+        }
+    }
+}
+
+} // namespace Kernel

src/core/hle/kernel/k_light_server_session.h

@@ -0,0 +1,49 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/hle/kernel/k_auto_object.h"
+#include "core/hle/kernel/k_thread.h"
+#include "core/hle/result.h"
+
+namespace Kernel {
+
+class KLightSession;
+
+class KLightServerSession final : public KAutoObject,
+                                  public Common::IntrusiveListBaseNode<KLightServerSession> {
+    KERNEL_AUTOOBJECT_TRAITS(KLightServerSession, KAutoObject);
+
+private:
+    KLightSession* m_parent{};
+    KThread::WaiterList m_request_list{};
+    KThread* m_current_request{};
+    u64 m_server_thread_id{std::numeric_limits<u64>::max()};
+    KThread* m_server_thread{};
+
+public:
+    explicit KLightServerSession(KernelCore& kernel);
+    ~KLightServerSession();
+
+    void Initialize(KLightSession* parent) {
+        // Set member variables. */
+        m_parent = parent;
+    }
+
+    virtual void Destroy() override;
+
+    constexpr const KLightSession* GetParent() const {
+        return m_parent;
+    }
+
+    Result OnRequest(KThread* request_thread);
+    Result ReplyAndReceive(u32* data);
+
+    void OnClientClosed();
+
+private:
+    void CleanupRequests();
+};
+
+} // namespace Kernel

src/core/hle/kernel/k_light_session.cpp

@@ -0,0 +1,81 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "core/hle/kernel/k_client_port.h"
+#include "core/hle/kernel/k_light_client_session.h"
+#include "core/hle/kernel/k_light_server_session.h"
+#include "core/hle/kernel/k_light_session.h"
+#include "core/hle/kernel/k_process.h"
+
+namespace Kernel {
+
+KLightSession::KLightSession(KernelCore& kernel)
+    : KAutoObjectWithSlabHeapAndContainer(kernel), m_server(kernel), m_client(kernel) {}
+KLightSession::~KLightSession() = default;
+
+void KLightSession::Initialize(KClientPort* client_port, uintptr_t name) {
+    // Increment reference count.
+    // Because reference count is one on creation, this will result
+    // in a reference count of two. Thus, when both server and client are closed
+    // this object will be destroyed.
+    this->Open();
+
+    // Create our sub sessions.
+    KAutoObject::Create(std::addressof(m_server));
+    KAutoObject::Create(std::addressof(m_client));
+
+    // Initialize our sub sessions.
+    m_server.Initialize(this);
+    m_client.Initialize(this);
+
+    // Set state and name.
+    m_state = State::Normal;
+    m_name = name;
+
+    // Set our owner process.
+    m_process = GetCurrentProcessPointer(m_kernel);
+    m_process->Open();
+
+    // Set our port.
+    m_port = client_port;
+    if (m_port != nullptr) {
+        m_port->Open();
+    }
+
+    // Mark initialized.
+    m_initialized = true;
+}
+
+void KLightSession::Finalize() {
+    if (m_port != nullptr) {
+        m_port->OnSessionFinalized();
+        m_port->Close();
+    }
+}
+
+void KLightSession::OnServerClosed() {
+    if (m_state == State::Normal) {
+        m_state = State::ServerClosed;
+        m_client.OnServerClosed();
+    }
+
+    this->Close();
+}
+
+void KLightSession::OnClientClosed() {
+    if (m_state == State::Normal) {
+        m_state = State::ClientClosed;
+        m_server.OnClientClosed();
+    }
+
+    this->Close();
+}
+
+void KLightSession::PostDestroy(uintptr_t arg) {
+    // Release the session count resource the owner process holds.
+    KProcess* owner = reinterpret_cast<KProcess*>(arg);
+    owner->ReleaseResource(Svc::LimitableResource::SessionCountMax, 1);
+    owner->Close();
+}
+
+} // namespace Kernel

src/core/hle/kernel/k_light_session.h

@@ -0,0 +1,86 @@
+// SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/hle/kernel/k_light_client_session.h"
+#include "core/hle/kernel/k_light_server_session.h"
+#include "core/hle/kernel/slab_helpers.h"
+#include "core/hle/result.h"
+
+namespace Kernel {
+
+class KClientPort;
+class KProcess;
+
+// TODO: SupportDynamicExpansion for SlabHeap
+class KLightSession final
+    : public KAutoObjectWithSlabHeapAndContainer<KLightSession, KAutoObjectWithList> {
+    KERNEL_AUTOOBJECT_TRAITS(KLightSession, KAutoObject);
+
+private:
+    enum class State : u8 {
+        Invalid = 0,
+        Normal = 1,
+        ClientClosed = 2,
+        ServerClosed = 3,
+    };
+
+public:
+    static constexpr size_t DataSize = sizeof(u32) * 7;
+    static constexpr u32 ReplyFlag = (1U << 31);
+
+private:
+    KLightServerSession m_server;
+    KLightClientSession m_client;
+    State m_state{State::Invalid};
+    KClientPort* m_port{};
+    uintptr_t m_name{};
+    KProcess* m_process{};
+    bool m_initialized{};
+
+public:
+    explicit KLightSession(KernelCore& kernel);
+    ~KLightSession();
+
+    void Initialize(KClientPort* client_port, uintptr_t name);
+    void Finalize() override;
+
+    bool IsInitialized() const override {
+        return m_initialized;
+    }
+    uintptr_t GetPostDestroyArgument() const override {
+        return reinterpret_cast<uintptr_t>(m_process);
+    }
+
+    static void PostDestroy(uintptr_t arg);
+
+    void OnServerClosed();
+    void OnClientClosed();
+
+    bool IsServerClosed() const {
+        return m_state != State::Normal;
+    }
+    bool IsClientClosed() const {
+        return m_state != State::Normal;
+    }
+
+    Result OnRequest(KThread* request_thread) {
+        R_RETURN(m_server.OnRequest(request_thread));
+    }
+
+    KLightClientSession& GetClientSession() {
+        return m_client;
+    }
+    KLightServerSession& GetServerSession() {
+        return m_server;
+    }
+    const KLightClientSession& GetClientSession() const {
+        return m_client;
+    }
+    const KLightServerSession& GetServerSession() const {
+        return m_server;
+    }
+};
+
+} // namespace Kernel

src/core/hle/kernel/k_port.cpp

@@ -58,4 +58,13 @@ Result KPort::EnqueueSession(KServerSession* session) {
     R_SUCCEED();
 }
 
+Result KPort::EnqueueSession(KLightServerSession* session) {
+    KScopedSchedulerLock sl{m_kernel};
+
+    R_UNLESS(m_state == State::Normal, ResultPortClosed);
+
+    m_server.EnqueueSession(session);
+    R_SUCCEED();
+}
+
 } // namespace Kernel

src/core/hle/kernel/k_port.h

@@ -13,6 +13,7 @@
 
 namespace Kernel {
 
+class KLightServerSession;
 class KServerSession;
 
 class KPort final : public KAutoObjectWithSlabHeapAndContainer<KPort, KAutoObjectWithList> {
@@ -38,6 +39,7 @@ public:
     bool IsServerClosed() const;
 
     Result EnqueueSession(KServerSession* session);
+    Result EnqueueSession(KLightServerSession* session);
 
     KClientPort& GetClientPort() {
         return m_client;

src/core/hle/kernel/k_server_port.cpp

@@ -27,12 +27,14 @@ bool KServerPort::IsLight() const {
 void KServerPort::CleanupSessions() {
     // Ensure our preconditions are met.
     if (this->IsLight()) {
-        UNIMPLEMENTED();
+        ASSERT(m_session_list.empty());
+    } else {
+        ASSERT(m_light_session_list.empty());
     }
 
     // Cleanup the session list.
     while (true) {
-        // Get the last session in the list
+        // Get the last session in the list.
         KServerSession* session = nullptr;
         {
             KScopedSchedulerLock sl{m_kernel};
@@ -49,6 +51,26 @@ void KServerPort::CleanupSessions() {
             break;
         }
     }
+
+    // Cleanup the light session list.
+    while (true) {
+        // Get the last session in the list.
+        KLightServerSession* session = nullptr;
+        {
+            KScopedSchedulerLock sl{m_kernel};
+            if (!m_light_session_list.empty()) {
+                session = std::addressof(m_light_session_list.front());
+                m_light_session_list.pop_front();
+            }
+        }
+
+        // Close the session.
+        if (session != nullptr) {
+            session->Close();
+        } else {
+            break;
+        }
+    }
 }
 
 void KServerPort::Destroy() {
@@ -64,8 +86,7 @@ void KServerPort::Destroy() {
 
 bool KServerPort::IsSignaled() const {
     if (this->IsLight()) {
-        UNIMPLEMENTED();
+        return !m_light_session_list.empty();
-        return false;
     } else {
         return !m_session_list.empty();
     }
@@ -83,6 +104,18 @@ void KServerPort::EnqueueSession(KServerSession* session) {
     }
 }
 
+void KServerPort::EnqueueSession(KLightServerSession* session) {
+    ASSERT(this->IsLight());
+
+    KScopedSchedulerLock sl{m_kernel};
+
+    // Add the session to our queue.
+    m_light_session_list.push_back(*session);
+    if (m_light_session_list.size() == 1) {
+        this->NotifyAvailable();
+    }
+}
+
 KServerSession* KServerPort::AcceptSession() {
     ASSERT(!this->IsLight());
 
@@ -98,4 +131,19 @@ KServerSession* KServerPort::AcceptSession() {
     return session;
 }
 
+KLightServerSession* KServerPort::AcceptLightSession() {
+    ASSERT(this->IsLight());
+
+    KScopedSchedulerLock sl{m_kernel};
+
+    // Return the first session in the list.
+    if (m_light_session_list.empty()) {
+        return nullptr;
+    }
+
+    KLightServerSession* session = std::addressof(m_light_session_list.front());
+    m_light_session_list.pop_front();
+    return session;
+}
+
 } // namespace Kernel

src/core/hle/kernel/k_server_port.h

@@ -9,6 +9,7 @@
 
 #include "common/intrusive_list.h"
 
+#include "core/hle/kernel/k_light_server_session.h"
 #include "core/hle/kernel/k_server_session.h"
 #include "core/hle/kernel/k_synchronization_object.h"
 
@@ -28,8 +29,10 @@ public:
     void Initialize(KPort* parent);
 
     void EnqueueSession(KServerSession* session);
+    void EnqueueSession(KLightServerSession* session);
 
     KServerSession* AcceptSession();
+    KLightServerSession* AcceptLightSession();
 
     const KPort* GetParent() const {
         return m_parent;
@@ -43,10 +46,12 @@ public:
 
 private:
     using SessionList = Common::IntrusiveListBaseTraits<KServerSession>::ListType;
+    using LightSessionList = Common::IntrusiveListBaseTraits<KLightServerSession>::ListType;
 
     void CleanupSessions();
 
     SessionList m_session_list{};
+    LightSessionList m_light_session_list{};
     KPort* m_parent{};
 };
 

src/core/hle/kernel/k_thread.h

@@ -385,6 +385,13 @@ public:
         m_cancellable = false;
     }
 
+    u32* GetLightSessionData() const {
+        return m_light_ipc_data;
+    }
+    void SetLightSessionData(u32* data) {
+        m_light_ipc_data = data;
+    }
+
     bool IsTerminationRequested() const {
         return m_termination_requested || GetRawState() == ThreadState::Terminated;
     }

src/core/hle/kernel/kernel.cpp

@@ -1340,6 +1340,7 @@ struct KernelCore::SlabHeapContainer {
     KSlabHeap<KProcess> process;
     KSlabHeap<KResourceLimit> resource_limit;
     KSlabHeap<KSession> session;
+    KSlabHeap<KLightSession> light_session;
     KSlabHeap<KSharedMemory> shared_memory;
     KSlabHeap<KSharedMemoryInfo> shared_memory_info;
     KSlabHeap<KThread> thread;
@@ -1370,6 +1371,8 @@ KSlabHeap<T>& KernelCore::SlabHeap() {
         return slab_heap_container->resource_limit;
     } else if constexpr (std::is_same_v<T, KSession>) {
         return slab_heap_container->session;
+    } else if constexpr (std::is_same_v<T, KLightSession>) {
+        return slab_heap_container->light_session;
     } else if constexpr (std::is_same_v<T, KSharedMemory>) {
         return slab_heap_container->shared_memory;
     } else if constexpr (std::is_same_v<T, KSharedMemoryInfo>) {
@@ -1407,6 +1410,7 @@ template KSlabHeap<KPort>& KernelCore::SlabHeap();
 template KSlabHeap<KProcess>& KernelCore::SlabHeap();
 template KSlabHeap<KResourceLimit>& KernelCore::SlabHeap();
 template KSlabHeap<KSession>& KernelCore::SlabHeap();
+template KSlabHeap<KLightSession>& KernelCore::SlabHeap();
 template KSlabHeap<KSharedMemory>& KernelCore::SlabHeap();
 template KSlabHeap<KSharedMemoryInfo>& KernelCore::SlabHeap();
 template KSlabHeap<KThread>& KernelCore::SlabHeap();

src/core/hle/kernel/svc/svc_light_ipc.cpp

@@ -1,21 +1,40 @@
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
-#include "core/arm/arm_interface.h"
 #include "core/core.h"
+#include "core/hle/kernel/k_light_client_session.h"
+#include "core/hle/kernel/k_light_server_session.h"
+#include "core/hle/kernel/k_process.h"
+#include "core/hle/kernel/k_thread.h"
 #include "core/hle/kernel/svc.h"
 #include "core/hle/kernel/svc_results.h"
 
 namespace Kernel::Svc {
 
 Result SendSyncRequestLight(Core::System& system, Handle session_handle, u32* args) {
-    UNIMPLEMENTED();
+    // Get the light client session from its handle.
-    R_THROW(ResultNotImplemented);
+    KScopedAutoObject session = GetCurrentProcess(system.Kernel())
+                                    .GetHandleTable()
+                                    .GetObject<KLightClientSession>(session_handle);
+    R_UNLESS(session.IsNotNull(), ResultInvalidHandle);
+
+    // Send the request.
+    R_TRY(session->SendSyncRequest(args));
+
+    R_SUCCEED();
 }
 
 Result ReplyAndReceiveLight(Core::System& system, Handle session_handle, u32* args) {
-    UNIMPLEMENTED();
+    // Get the light server session from its handle.
-    R_THROW(ResultNotImplemented);
+    KScopedAutoObject session = GetCurrentProcess(system.Kernel())
+                                    .GetHandleTable()
+                                    .GetObject<KLightServerSession>(session_handle);
+    R_UNLESS(session.IsNotNull(), ResultInvalidHandle);
+
+    // Handle the request.
+    R_TRY(session->ReplyAndReceive(args));
+
+    R_SUCCEED();
 }
 
 Result SendSyncRequestLight64(Core::System& system, Handle session_handle, u32* args) {

src/core/hle/kernel/svc/svc_port.cpp

@@ -5,6 +5,7 @@
 #include "core/core.h"
 #include "core/hle/kernel/k_client_port.h"
 #include "core/hle/kernel/k_client_session.h"
+#include "core/hle/kernel/k_light_client_session.h"
 #include "core/hle/kernel/k_object_name.h"
 #include "core/hle/kernel/k_port.h"
 #include "core/hle/kernel/k_process.h"
@@ -51,13 +52,73 @@ Result ConnectToNamedPort(Core::System& system, Handle* out, u64 user_name) {
 
 Result CreatePort(Core::System& system, Handle* out_server, Handle* out_client,
                   int32_t max_sessions, bool is_light, uint64_t name) {
-    UNIMPLEMENTED();
+    auto& kernel = system.Kernel();
-    R_THROW(ResultNotImplemented);
+
+    // Ensure max sessions is valid.
+    R_UNLESS(max_sessions > 0, ResultOutOfRange);
+
+    // Get the current handle table.
+    auto& handle_table = GetCurrentProcess(kernel).GetHandleTable();
+
+    // Create a new port.
+    KPort* port = KPort::Create(kernel);
+    R_UNLESS(port != nullptr, ResultOutOfResource);
+
+    // Initialize the port.
+    port->Initialize(max_sessions, is_light, name);
+
+    // Ensure that we clean up the port (and its only references are handle table) on function end.
+    SCOPE_EXIT({
+        port->GetServerPort().Close();
+        port->GetClientPort().Close();
+    });
+
+    // Register the port.
+    KPort::Register(kernel, port);
+
+    // Add the client to the handle table.
+    R_TRY(handle_table.Add(out_client, std::addressof(port->GetClientPort())));
+
+    // Ensure that we maintain a clean handle state on exit.
+    ON_RESULT_FAILURE {
+        handle_table.Remove(*out_client);
+    };
+
+    // Add the server to the handle table.
+    R_RETURN(handle_table.Add(out_server, std::addressof(port->GetServerPort())));
 }
 
-Result ConnectToPort(Core::System& system, Handle* out_handle, Handle port) {
+Result ConnectToPort(Core::System& system, Handle* out, Handle port) {
-    UNIMPLEMENTED();
+    // Get the current handle table.
-    R_THROW(ResultNotImplemented);
+    auto& handle_table = GetCurrentProcess(system.Kernel()).GetHandleTable();
+
+    // Get the client port.
+    KScopedAutoObject client_port = handle_table.GetObject<KClientPort>(port);
+    R_UNLESS(client_port.IsNotNull(), ResultInvalidHandle);
+
+    // Reserve a handle for the port.
+    // NOTE: Nintendo really does write directly to the output handle here.
+    R_TRY(handle_table.Reserve(out));
+    ON_RESULT_FAILURE {
+        handle_table.Unreserve(*out);
+    };
+
+    // Create the session.
+    KAutoObject* session;
+    if (client_port->IsLight()) {
+        R_TRY(client_port->CreateLightSession(
+            reinterpret_cast<KLightClientSession**>(std::addressof(session))));
+    } else {
+        R_TRY(client_port->CreateSession(
+            reinterpret_cast<KClientSession**>(std::addressof(session))));
+    }
+
+    // Register the session.
+    handle_table.Register(*out, session);
+    session->Close();
+
+    // We succeeded.
+    R_SUCCEED();
 }
 
 Result ManageNamedPort(Core::System& system, Handle* out_server_handle, uint64_t user_name,

src/core/hle/kernel/svc/svc_session.cpp

@@ -3,8 +3,10 @@
 
 #include "common/scope_exit.h"
 #include "core/core.h"
+#include "core/hle/kernel/k_light_session.h"
 #include "core/hle/kernel/k_process.h"
 #include "core/hle/kernel/k_scoped_resource_reservation.h"
+#include "core/hle/kernel/k_server_port.h"
 #include "core/hle/kernel/k_session.h"
 #include "core/hle/kernel/svc.h"
 
@@ -20,7 +22,7 @@ Result CreateSession(Core::System& system, Handle* out_server, Handle* out_clien
     T* session;
 
     // Reserve a new session from the process resource limit.
-    // FIXME: LimitableResource_SessionCountMax
+    // TODO: Dynamic resource limits
     KScopedResourceReservation session_reservation(std::addressof(process),
                                                    LimitableResource::SessionCountMax);
     if (session_reservation.Succeeded()) {
@@ -92,16 +94,42 @@ Result CreateSession(Core::System& system, Handle* out_server, Handle* out_clien
 Result CreateSession(Core::System& system, Handle* out_server, Handle* out_client, bool is_light,
                      u64 name) {
     if (is_light) {
-        // return CreateSession<KLightSession>(system, out_server, out_client, name);
+        R_RETURN(CreateSession<KLightSession>(system, out_server, out_client, name));
-        R_THROW(ResultNotImplemented);
     } else {
         R_RETURN(CreateSession<KSession>(system, out_server, out_client, name));
     }
 }
 
-Result AcceptSession(Core::System& system, Handle* out_handle, Handle port_handle) {
+Result AcceptSession(Core::System& system, Handle* out, Handle port_handle) {
-    UNIMPLEMENTED();
+    // Get the current handle table.
-    R_THROW(ResultNotImplemented);
+    auto& handle_table = GetCurrentProcess(system.Kernel()).GetHandleTable();
+
+    // Get the server port.
+    KScopedAutoObject port = handle_table.GetObject<KServerPort>(port_handle);
+    R_UNLESS(port.IsNotNull(), ResultInvalidHandle);
+
+    // Reserve an entry for the new session.
+    R_TRY(handle_table.Reserve(out));
+    ON_RESULT_FAILURE {
+        handle_table.Unreserve(*out);
+    };
+
+    // Accept the session.
+    KAutoObject* session;
+    if (port->IsLight()) {
+        session = port->AcceptLightSession();
+    } else {
+        session = port->AcceptSession();
+    }
+
+    // Ensure we accepted successfully.
+    R_UNLESS(session != nullptr, ResultNotFound);
+
+    // Register the session.
+    handle_table.Register(*out, session);
+    session->Close();
+
+    R_SUCCEED();
 }
 
 Result CreateSession64(Core::System& system, Handle* out_server_session_handle,