// SPDX-FileCopyrightText: Copyright 2021 yuzu Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#pragma once

#include <array>
#include <atomic>
#include <condition_variable>
#include <mutex>
#include <span>
#include <string>
#include <utility>
#include <vector>

#include <boost/intrusive/list.hpp>

#include "common/common_types.h"
#include "common/intrusive_red_black_tree.h"
#include "common/spin_lock.h"
#include "core/arm/arm_interface.h"
#include "core/hle/kernel/k_affinity_mask.h"
#include "core/hle/kernel/k_light_lock.h"
#include "core/hle/kernel/k_spin_lock.h"
#include "core/hle/kernel/k_synchronization_object.h"
#include "core/hle/kernel/k_worker_task.h"
#include "core/hle/kernel/slab_helpers.h"
#include "core/hle/kernel/svc_common.h"
#include "core/hle/kernel/svc_types.h"
#include "core/hle/result.h"

namespace Common {
class Fiber;
}

namespace Core {
class ARM_Interface;
class System;
} // namespace Core

namespace Kernel {

class GlobalSchedulerContext;
class KernelCore;
class KProcess;
class KScheduler;
class KThreadQueue;

using KThreadFunction = VAddr;

enum class ThreadType : u32 {
    Main = 0,
    Kernel = 1,
    HighPriority = 2,
    User = 3,
    Dummy = 100, // Special thread type for emulation purposes only
};
DECLARE_ENUM_FLAG_OPERATORS(ThreadType);

enum class SuspendType : u32 {
    Process = 0,
    Thread = 1,
    Debug = 2,
    Backtrace = 3,
    Init = 4,

    Count,
};

enum class ThreadState : u16 {
    Initialized = 0,
    Waiting = 1,
    Runnable = 2,
    Terminated = 3,

    SuspendShift = 4,
    Mask = (1 << SuspendShift) - 1,

    ProcessSuspended = (1 << (0 + SuspendShift)),
    ThreadSuspended = (1 << (1 + SuspendShift)),
    DebugSuspended = (1 << (2 + SuspendShift)),
    BacktraceSuspended = (1 << (3 + SuspendShift)),
    InitSuspended = (1 << (4 + SuspendShift)),

    SuspendFlagMask = ((1 << 5) - 1) << SuspendShift,
};
DECLARE_ENUM_FLAG_OPERATORS(ThreadState);

enum class DpcFlag : u32 {
    Terminating = (1 << 0),
    Terminated = (1 << 1),
};

enum class ThreadWaitReasonForDebugging : u32 {
    None,            ///< Thread is not waiting
    Sleep,           ///< Thread is waiting due to a SleepThread SVC
    IPC,             ///< Thread is waiting for the reply from an IPC request
    Synchronization, ///< Thread is waiting due to a WaitSynchronization SVC
    ConditionVar,    ///< Thread is waiting due to a WaitProcessWideKey SVC
    Arbitration,     ///< Thread is waiting due to a SignalToAddress/WaitForAddress SVC
    Suspended,       ///< Thread is waiting due to process suspension
};

enum class StepState : u32 {
    NotStepping,   ///< Thread is not currently stepping
    StepPending,   ///< Thread will step when next scheduled
    StepPerformed, ///< Thread has stepped, waiting to be scheduled again
};

void SetCurrentThread(KernelCore& kernel, KThread* thread);
[[nodiscard]] KThread* GetCurrentThreadPointer(KernelCore& kernel);
[[nodiscard]] KThread& GetCurrentThread(KernelCore& kernel);
[[nodiscard]] s32 GetCurrentCoreId(KernelCore& kernel);

class KThread final : public KAutoObjectWithSlabHeapAndContainer<KThread, KWorkerTask>,
                      public boost::intrusive::list_base_hook<> {
    KERNEL_AUTOOBJECT_TRAITS(KThread, KSynchronizationObject);

private:
    friend class KScheduler;
    friend class KProcess;

public:
    static constexpr s32 DefaultThreadPriority = 44;
    static constexpr s32 IdleThreadPriority = Svc::LowestThreadPriority + 1;
    static constexpr s32 DummyThreadPriority = Svc::LowestThreadPriority + 2;

    explicit KThread(KernelCore& kernel_);
    ~KThread() override;

public:
    using ThreadContext32 = Core::ARM_Interface::ThreadContext32;
    using ThreadContext64 = Core::ARM_Interface::ThreadContext64;
    using WaiterList = boost::intrusive::list<KThread>;

    void SetName(std::string new_name) {
        name = std::move(new_name);
    }

    /**
     * Gets the thread's current priority
     * @return The current thread's priority
     */
    [[nodiscard]] s32 GetPriority() const {
        return priority;
    }

    /**
     * Sets the thread's current priority.
     * @param priority The new priority.
     */
    void SetPriority(s32 value) {
        priority = value;
    }

    /**
     * Gets the thread's nominal priority.
     * @return The current thread's nominal priority.
     */
    [[nodiscard]] s32 GetBasePriority() const {
        return base_priority;
    }

    /**
     * Gets the thread's thread ID
     * @return The thread's ID
     */
    [[nodiscard]] u64 GetThreadID() const {
        return thread_id;
    }

    void ContinueIfHasKernelWaiters() {
        if (GetNumKernelWaiters() > 0) {
            Continue();
        }
    }

    void SetBasePriority(s32 value);

    [[nodiscard]] Result Run();

    void Exit();

    [[nodiscard]] u32 GetSuspendFlags() const {
        return suspend_allowed_flags & suspend_request_flags;
    }

    [[nodiscard]] bool IsSuspended() const {
        return GetSuspendFlags() != 0;
    }

    [[nodiscard]] bool IsSuspendRequested(SuspendType type) const {
        return (suspend_request_flags &
                (1u << (static_cast<u32>(ThreadState::SuspendShift) + static_cast<u32>(type)))) !=
               0;
    }

    [[nodiscard]] bool IsSuspendRequested() const {
        return suspend_request_flags != 0;
    }

    void RequestSuspend(SuspendType type);

    void Resume(SuspendType type);

    void TrySuspend();

    void UpdateState();

    void Continue();

    void WaitUntilSuspended();

    constexpr void SetSyncedIndex(s32 index) {
        synced_index = index;
    }

    [[nodiscard]] constexpr s32 GetSyncedIndex() const {
        return synced_index;
    }

    constexpr void SetWaitResult(Result wait_res) {
        wait_result = wait_res;
    }

    [[nodiscard]] constexpr Result GetWaitResult() const {
        return wait_result;
    }

    /*
     * Returns the Thread Local Storage address of the current thread
     * @returns VAddr of the thread's TLS
     */
    [[nodiscard]] VAddr GetTLSAddress() const {
        return tls_address;
    }

    /*
     * Returns the value of the TPIDR_EL0 Read/Write system register for this thread.
     * @returns The value of the TPIDR_EL0 register.
     */
    [[nodiscard]] u64 GetTPIDR_EL0() const {
        return thread_context_64.tpidr;
    }

    /// Sets the value of the TPIDR_EL0 Read/Write system register for this thread.
    void SetTPIDR_EL0(u64 value) {
        thread_context_64.tpidr = value;
        thread_context_32.tpidr = static_cast<u32>(value);
    }

    [[nodiscard]] ThreadContext32& GetContext32() {
        return thread_context_32;
    }

    [[nodiscard]] const ThreadContext32& GetContext32() const {
        return thread_context_32;
    }

    [[nodiscard]] ThreadContext64& GetContext64() {
        return thread_context_64;
    }

    [[nodiscard]] const ThreadContext64& GetContext64() const {
        return thread_context_64;
    }

    [[nodiscard]] std::shared_ptr<Common::Fiber>& GetHostContext();

    [[nodiscard]] ThreadState GetState() const {
        return thread_state.load(std::memory_order_relaxed) & ThreadState::Mask;
    }

    [[nodiscard]] ThreadState GetRawState() const {
        return thread_state.load(std::memory_order_relaxed);
    }

    void SetState(ThreadState state);

    [[nodiscard]] StepState GetStepState() const {
        return step_state;
    }

    void SetStepState(StepState state) {
        step_state = state;
    }

    [[nodiscard]] s64 GetLastScheduledTick() const {
        return last_scheduled_tick;
    }

    void SetLastScheduledTick(s64 tick) {
        last_scheduled_tick = tick;
    }

    void AddCpuTime([[maybe_unused]] s32 core_id_, s64 amount) {
        cpu_time += amount;
        // TODO(bunnei): Debug kernels track per-core tick counts. Should we?
    }

    [[nodiscard]] s64 GetCpuTime() const {
        return cpu_time;
    }

    [[nodiscard]] s32 GetActiveCore() const {
        return core_id;
    }

    void SetActiveCore(s32 core) {
        core_id = core;
    }

    [[nodiscard]] s32 GetCurrentCore() const {
        return current_core_id;
    }

    void SetCurrentCore(s32 core) {
        current_core_id = core;
    }

    [[nodiscard]] KProcess* GetOwnerProcess() {
        return parent;
    }

    [[nodiscard]] const KProcess* GetOwnerProcess() const {
        return parent;
    }

    [[nodiscard]] bool IsUserThread() const {
        return parent != nullptr;
    }

    u16 GetUserDisableCount() const;
    void SetInterruptFlag();
    void ClearInterruptFlag();

    [[nodiscard]] KThread* GetLockOwner() const {
        return lock_owner;
    }

    void SetLockOwner(KThread* owner) {
        lock_owner = owner;
    }

    [[nodiscard]] const KAffinityMask& GetAffinityMask() const {
        return physical_affinity_mask;
    }

    [[nodiscard]] Result GetCoreMask(s32* out_ideal_core, u64* out_affinity_mask);

    [[nodiscard]] Result GetPhysicalCoreMask(s32* out_ideal_core, u64* out_affinity_mask);

    [[nodiscard]] Result SetCoreMask(s32 cpu_core_id, u64 v_affinity_mask);

    [[nodiscard]] Result SetActivity(Svc::ThreadActivity activity);

    [[nodiscard]] Result Sleep(s64 timeout);

    [[nodiscard]] s64 GetYieldScheduleCount() const {
        return schedule_count;
    }

    void SetYieldScheduleCount(s64 count) {
        schedule_count = count;
    }

    void WaitCancel();

    [[nodiscard]] bool IsWaitCancelled() const {
        return wait_cancelled;
    }

    void ClearWaitCancelled() {
        wait_cancelled = false;
    }

    [[nodiscard]] bool IsCancellable() const {
        return cancellable;
    }

    void SetCancellable() {
        cancellable = true;
    }

    void ClearCancellable() {
        cancellable = false;
    }

    [[nodiscard]] bool IsTerminationRequested() const {
        return termination_requested || GetRawState() == ThreadState::Terminated;
    }

    [[nodiscard]] u64 GetId() const override {
        return this->GetThreadID();
    }

    [[nodiscard]] bool IsInitialized() const override {
        return initialized;
    }

    [[nodiscard]] uintptr_t GetPostDestroyArgument() const override {
        return reinterpret_cast<uintptr_t>(parent) | (resource_limit_release_hint ? 1 : 0);
    }

    void Finalize() override;

    [[nodiscard]] bool IsSignaled() const override;

    void OnTimer();

    void DoWorkerTaskImpl();

    static void PostDestroy(uintptr_t arg);

    [[nodiscard]] static Result InitializeDummyThread(KThread* thread);

    [[nodiscard]] static Result InitializeIdleThread(Core::System& system, KThread* thread,
                                                     s32 virt_core);

    [[nodiscard]] static Result InitializeHighPriorityThread(Core::System& system, KThread* thread,
                                                             KThreadFunction func, uintptr_t arg,
                                                             s32 virt_core);

    [[nodiscard]] static Result InitializeUserThread(Core::System& system, KThread* thread,
                                                     KThreadFunction func, uintptr_t arg,
                                                     VAddr user_stack_top, s32 prio, s32 virt_core,
                                                     KProcess* owner);

public:
    struct StackParameters {
        u8 svc_permission[0x10];
        std::atomic<u8> dpc_flags;
        u8 current_svc_id;
        bool is_calling_svc;
        bool is_in_exception_handler;
        bool is_pinned;
        s32 disable_count;
        KThread* cur_thread;
    };

    [[nodiscard]] StackParameters& GetStackParameters() {
        return stack_parameters;
    }

    [[nodiscard]] const StackParameters& GetStackParameters() const {
        return stack_parameters;
    }

    class QueueEntry {
    public:
        constexpr QueueEntry() = default;

        constexpr void Initialize() {
            prev = nullptr;
            next = nullptr;
        }

        constexpr KThread* GetPrev() const {
            return prev;
        }
        constexpr KThread* GetNext() const {
            return next;
        }
        constexpr void SetPrev(KThread* thread) {
            prev = thread;
        }
        constexpr void SetNext(KThread* thread) {
            next = thread;
        }

    private:
        KThread* prev{};
        KThread* next{};
    };

    [[nodiscard]] QueueEntry& GetPriorityQueueEntry(s32 core) {
        return per_core_priority_queue_entry[core];
    }

    [[nodiscard]] const QueueEntry& GetPriorityQueueEntry(s32 core) const {
        return per_core_priority_queue_entry[core];
    }

    [[nodiscard]] bool IsKernelThread() const {
        return GetActiveCore() == 3;
    }

    [[nodiscard]] bool IsDispatchTrackingDisabled() const {
        return is_single_core || IsKernelThread();
    }

    [[nodiscard]] s32 GetDisableDispatchCount() const {
        if (IsDispatchTrackingDisabled()) {
            // TODO(bunnei): Until kernel threads are emulated, we cannot enable/disable dispatch.
            return 1;
        }

        return this->GetStackParameters().disable_count;
    }

    void DisableDispatch() {
        if (IsDispatchTrackingDisabled()) {
            // TODO(bunnei): Until kernel threads are emulated, we cannot enable/disable dispatch.
            return;
        }

        ASSERT(GetCurrentThread(kernel).GetDisableDispatchCount() >= 0);
        this->GetStackParameters().disable_count++;
    }

    void EnableDispatch() {
        if (IsDispatchTrackingDisabled()) {
            // TODO(bunnei): Until kernel threads are emulated, we cannot enable/disable dispatch.
            return;
        }

        ASSERT(GetCurrentThread(kernel).GetDisableDispatchCount() > 0);
        this->GetStackParameters().disable_count--;
    }

    void Pin(s32 current_core);

    void Unpin();

    void SetInExceptionHandler() {
        this->GetStackParameters().is_in_exception_handler = true;
    }

    void ClearInExceptionHandler() {
        this->GetStackParameters().is_in_exception_handler = false;
    }

    [[nodiscard]] bool IsInExceptionHandler() const {
        return this->GetStackParameters().is_in_exception_handler;
    }

    void SetIsCallingSvc() {
        this->GetStackParameters().is_calling_svc = true;
    }

    void ClearIsCallingSvc() {
        this->GetStackParameters().is_calling_svc = false;
    }

    [[nodiscard]] bool IsCallingSvc() const {
        return this->GetStackParameters().is_calling_svc;
    }

    [[nodiscard]] u8 GetSvcId() const {
        return this->GetStackParameters().current_svc_id;
    }

    void RegisterDpc(DpcFlag flag) {
        this->GetStackParameters().dpc_flags |= static_cast<u8>(flag);
    }

    void ClearDpc(DpcFlag flag) {
        this->GetStackParameters().dpc_flags &= ~static_cast<u8>(flag);
    }

    [[nodiscard]] u8 GetDpc() const {
        return this->GetStackParameters().dpc_flags;
    }

    [[nodiscard]] bool HasDpc() const {
        return this->GetDpc() != 0;
    }

    void SetWaitReasonForDebugging(ThreadWaitReasonForDebugging reason) {
        wait_reason_for_debugging = reason;
    }

    [[nodiscard]] ThreadWaitReasonForDebugging GetWaitReasonForDebugging() const {
        return wait_reason_for_debugging;
    }

    [[nodiscard]] ThreadType GetThreadType() const {
        return thread_type;
    }

    [[nodiscard]] bool IsDummyThread() const {
        return GetThreadType() == ThreadType::Dummy;
    }

    void SetWaitObjectsForDebugging(const std::span<KSynchronizationObject*>& objects) {
        wait_objects_for_debugging.clear();
        wait_objects_for_debugging.reserve(objects.size());
        for (const auto& object : objects) {
            wait_objects_for_debugging.emplace_back(object);
        }
    }

    [[nodiscard]] const std::vector<KSynchronizationObject*>& GetWaitObjectsForDebugging() const {
        return wait_objects_for_debugging;
    }

    void SetMutexWaitAddressForDebugging(VAddr address) {
        mutex_wait_address_for_debugging = address;
    }

    [[nodiscard]] VAddr GetMutexWaitAddressForDebugging() const {
        return mutex_wait_address_for_debugging;
    }

    [[nodiscard]] s32 GetIdealCoreForDebugging() const {
        return virtual_ideal_core_id;
    }

    void AddWaiter(KThread* thread);

    void RemoveWaiter(KThread* thread);

    [[nodiscard]] Result GetThreadContext3(std::vector<u8>& out);

    [[nodiscard]] KThread* RemoveWaiterByKey(s32* out_num_waiters, VAddr key);

    [[nodiscard]] VAddr GetAddressKey() const {
        return address_key;
    }

    [[nodiscard]] u32 GetAddressKeyValue() const {
        return address_key_value;
    }

    void SetAddressKey(VAddr key) {
        address_key = key;
    }

    void SetAddressKey(VAddr key, u32 val) {
        address_key = key;
        address_key_value = val;
    }

    void ClearWaitQueue() {
        wait_queue = nullptr;
    }

    void BeginWait(KThreadQueue* queue);
    void NotifyAvailable(KSynchronizationObject* signaled_object, Result wait_result_);
    void EndWait(Result wait_result_);
    void CancelWait(Result wait_result_, bool cancel_timer_task);

    [[nodiscard]] bool HasWaiters() const {
        return !waiter_list.empty();
    }

    [[nodiscard]] s32 GetNumKernelWaiters() const {
        return num_kernel_waiters;
    }

    [[nodiscard]] u64 GetConditionVariableKey() const {
        return condvar_key;
    }

    [[nodiscard]] u64 GetAddressArbiterKey() const {
        return condvar_key;
    }

    // Dummy threads (used for HLE host threads) cannot wait based on the guest scheduler, and
    // therefore will not block on guest kernel synchronization primitives. These methods handle
    // blocking as needed.

    void IfDummyThreadTryWait();
    void IfDummyThreadEndWait();

    [[nodiscard]] uintptr_t GetArgument() const {
        return argument;
    }

    [[nodiscard]] VAddr GetUserStackTop() const {
        return stack_top;
    }

private:
    static constexpr size_t PriorityInheritanceCountMax = 10;
    union SyncObjectBuffer {
        std::array<KSynchronizationObject*, Svc::ArgumentHandleCountMax> sync_objects{};
        std::array<Handle,
                   Svc::ArgumentHandleCountMax*(sizeof(KSynchronizationObject*) / sizeof(Handle))>
            handles;
        constexpr SyncObjectBuffer() {}
    };
    static_assert(sizeof(SyncObjectBuffer::sync_objects) == sizeof(SyncObjectBuffer::handles));

    struct ConditionVariableComparator {
        struct RedBlackKeyType {
            u64 cv_key{};
            s32 priority{};

            [[nodiscard]] constexpr u64 GetConditionVariableKey() const {
                return cv_key;
            }

            [[nodiscard]] constexpr s32 GetPriority() const {
                return priority;
            }
        };

        template <typename T>
        requires(
            std::same_as<T, KThread> ||
            std::same_as<T, RedBlackKeyType>) static constexpr int Compare(const T& lhs,
                                                                           const KThread& rhs) {
            const u64 l_key = lhs.GetConditionVariableKey();
            const u64 r_key = rhs.GetConditionVariableKey();

            if (l_key < r_key) {
                // Sort first by key
                return -1;
            } else if (l_key == r_key && lhs.GetPriority() < rhs.GetPriority()) {
                // And then by priority.
                return -1;
            } else {
                return 1;
            }
        }
    };

    void AddWaiterImpl(KThread* thread);

    void RemoveWaiterImpl(KThread* thread);

    void StartTermination();

    void FinishTermination();

    [[nodiscard]] Result Initialize(KThreadFunction func, uintptr_t arg, VAddr user_stack_top,
                                    s32 prio, s32 virt_core, KProcess* owner, ThreadType type);

    [[nodiscard]] static Result InitializeThread(KThread* thread, KThreadFunction func,
                                                 uintptr_t arg, VAddr user_stack_top, s32 prio,
                                                 s32 core, KProcess* owner, ThreadType type,
                                                 std::function<void()>&& init_func);

    static void RestorePriority(KernelCore& kernel_ctx, KThread* thread);

    // For core KThread implementation
    ThreadContext32 thread_context_32{};
    ThreadContext64 thread_context_64{};
    Common::IntrusiveRedBlackTreeNode condvar_arbiter_tree_node{};
    s32 priority{};
    using ConditionVariableThreadTreeTraits =
        Common::IntrusiveRedBlackTreeMemberTraitsDeferredAssert<
            &KThread::condvar_arbiter_tree_node>;
    using ConditionVariableThreadTree =
        ConditionVariableThreadTreeTraits::TreeType<ConditionVariableComparator>;
    ConditionVariableThreadTree* condvar_tree{};
    u64 condvar_key{};
    u64 virtual_affinity_mask{};
    KAffinityMask physical_affinity_mask{};
    u64 thread_id{};
    std::atomic<s64> cpu_time{};
    VAddr address_key{};
    KProcess* parent{};
    VAddr kernel_stack_top{};
    u32* light_ipc_data{};
    VAddr tls_address{};
    KLightLock activity_pause_lock;
    s64 schedule_count{};
    s64 last_scheduled_tick{};
    std::array<QueueEntry, Core::Hardware::NUM_CPU_CORES> per_core_priority_queue_entry{};
    KThreadQueue* wait_queue{};
    WaiterList waiter_list{};
    WaiterList pinned_waiter_list{};
    KThread* lock_owner{};
    u32 address_key_value{};
    u32 suspend_request_flags{};
    u32 suspend_allowed_flags{};
    s32 synced_index{};
    Result wait_result{ResultSuccess};
    s32 base_priority{};
    s32 physical_ideal_core_id{};
    s32 virtual_ideal_core_id{};
    s32 num_kernel_waiters{};
    s32 current_core_id{};
    s32 core_id{};
    KAffinityMask original_physical_affinity_mask{};
    s32 original_physical_ideal_core_id{};
    s32 num_core_migration_disables{};
    std::atomic<ThreadState> thread_state{};
    std::atomic<bool> termination_requested{};
    bool wait_cancelled{};
    bool cancellable{};
    bool signaled{};
    bool initialized{};
    bool debug_attached{};
    s8 priority_inheritance_count{};
    bool resource_limit_release_hint{};
    StackParameters stack_parameters{};
    Common::SpinLock context_guard{};

    // For emulation
    std::shared_ptr<Common::Fiber> host_context{};
    bool is_single_core{};
    ThreadType thread_type{};
    StepState step_state{};
    std::mutex dummy_wait_lock;
    std::condition_variable dummy_wait_cv;

    // For debugging
    std::vector<KSynchronizationObject*> wait_objects_for_debugging;
    VAddr mutex_wait_address_for_debugging{};
    ThreadWaitReasonForDebugging wait_reason_for_debugging{};
    uintptr_t argument;
    VAddr stack_top;

public:
    using ConditionVariableThreadTreeType = ConditionVariableThreadTree;

    void SetConditionVariable(ConditionVariableThreadTree* tree, VAddr address, u64 cv_key,
                              u32 value) {
        condvar_tree = tree;
        condvar_key = cv_key;
        address_key = address;
        address_key_value = value;
    }

    void ClearConditionVariable() {
        condvar_tree = nullptr;
    }

    [[nodiscard]] bool IsWaitingForConditionVariable() const {
        return condvar_tree != nullptr;
    }

    void SetAddressArbiter(ConditionVariableThreadTree* tree, u64 address) {
        condvar_tree = tree;
        condvar_key = address;
    }

    void ClearAddressArbiter() {
        condvar_tree = nullptr;
    }

    [[nodiscard]] bool IsWaitingForAddressArbiter() const {
        return condvar_tree != nullptr;
    }

    [[nodiscard]] ConditionVariableThreadTree* GetConditionVariableTree() const {
        return condvar_tree;
    }
};

class KScopedDisableDispatch {
public:
    [[nodiscard]] explicit KScopedDisableDispatch(KernelCore& kernel_) : kernel{kernel_} {
        // If we are shutting down the kernel, none of this is relevant anymore.
        if (kernel.IsShuttingDown()) {
            return;
        }
        GetCurrentThread(kernel).DisableDispatch();
    }

    ~KScopedDisableDispatch();

private:
    KernelCore& kernel;
};

} // namespace Kernel
