Kernel: New handle manager

This handle manager more closely mirrors the behaviour of the CTR-OS
one. In addition object ref-counts and support for DuplicateHandle have
been added.

Note that support for DuplicateHandle is still experimental, since parts
of the kernel still use Handles internally, which will likely cause
troubles if two different handles to the same object are used to e.g.
wait on a synchronization primitive.

13 files changed, 209 insertions, 168 deletions

diff --git a/src/core/hle/kernel/address_arbiter.cpp b/src/core/hle/kernel/address_arbiter.cpp
index acdbc92b..38705e3c 100644
--- a/src/core/hle/kernel/address_arbiter.cpp
+++ b/src/core/hle/kernel/address_arbiter.cpp
@@ -62,7 +62,8 @@ ResultCode ArbitrateAddress(Handle handle, ArbitrationType type, u32 address, s3
 /// Create an address arbiter
 AddressArbiter* CreateAddressArbiter(Handle& handle, const std::string& name) {
     AddressArbiter* address_arbiter = new AddressArbiter;
-    handle = Kernel::g_handle_table.Create(address_arbiter);
+    // TOOD(yuriks): Fix error reporting
+    handle = Kernel::g_handle_table.Create(address_arbiter).ValueOr(INVALID_HANDLE);
     address_arbiter->name = name;
     return address_arbiter;
 }
diff --git a/src/core/hle/kernel/event.cpp b/src/core/hle/kernel/event.cpp
index 6a0e294c..e43c3ee4 100644
--- a/src/core/hle/kernel/event.cpp
+++ b/src/core/hle/kernel/event.cpp
@@ -129,7 +129,8 @@ ResultCode ClearEvent(Handle handle) {
 Event* CreateEvent(Handle& handle, const ResetType reset_type, const std::string& name) {
     Event* evt = new Event;
 
-    handle = Kernel::g_handle_table.Create(evt);
+    // TOOD(yuriks): Fix error reporting
+    handle = Kernel::g_handle_table.Create(evt).ValueOr(INVALID_HANDLE);
 
     evt->locked = true;
     evt->permanent_locked = false;
diff --git a/src/core/hle/kernel/kernel.cpp b/src/core/hle/kernel/kernel.cpp
index e8bf83a4..e59ed1b5 100644
--- a/src/core/hle/kernel/kernel.cpp
+++ b/src/core/hle/kernel/kernel.cpp
@@ -17,73 +17,89 @@ HandleTable g_handle_table;
 u64 g_program_id = 0;
 
 HandleTable::HandleTable() {
-    next_id = INITIAL_NEXT_ID;
+    next_generation = 1;
+    Clear();
 }
 
-Handle HandleTable::Create(Object* obj, int range_bottom, int range_top) {
-    if (range_top > MAX_COUNT) {
-        range_top = MAX_COUNT;
-    }
-    if (next_id >= range_bottom && next_id < range_top) {
-        range_bottom = next_id++;
-    }
-    for (int i = range_bottom; i < range_top; i++) {
-        if (!occupied[i]) {
-            occupied[i] = true;
-            pool[i] = obj;
-            pool[i]->handle = i + HANDLE_OFFSET;
-            return i + HANDLE_OFFSET;
-        }
+ResultVal<Handle> HandleTable::Create(Object* obj) {
+    _dbg_assert_(Kernel, obj != nullptr);
+
+    u16 slot = next_free_slot;
+    if (slot >= generations.size()) {
+        LOG_ERROR(Kernel, "Unable to allocate Handle, too many slots in use.");
+        return ERR_OUT_OF_HANDLES;
     }
-    LOG_ERROR(Kernel, "Unable to allocate kernel object, too many objects slots in use.");
-    return 0;
-}
+    next_free_slot = generations[slot];
 
-bool HandleTable::IsValid(Handle handle) const {
-    int index = handle - HANDLE_OFFSET;
-    if (index < 0)
-        return false;
-    if (index >= MAX_COUNT)
-        return false;
+    u16 generation = next_generation++;
 
-    return occupied[index];
+    // Overflow count so it fits in the 15 bits dedicated to the generation in the handle.
+    // CTR-OS doesn't use generation 0, so skip straight to 1.
+    if (next_generation >= (1 << 15)) next_generation = 1;
+
+    generations[slot] = generation;
+    intrusive_ptr_add_ref(obj);
+    objects[slot] = obj;
+
+    Handle handle = generation | (slot << 15);
+    obj->handle = handle;
+    return MakeResult<Handle>(handle);
 }
 
-void HandleTable::Clear() {
-    for (int i = 0; i < MAX_COUNT; i++) {
-        //brutally clear everything, no validation
-        if (occupied[i])
-            delete pool[i];
-        occupied[i] = false;
+ResultVal<Handle> HandleTable::Duplicate(Handle handle) {
+    Object* object = GetGeneric(handle);
+    if (object == nullptr) {
+        LOG_ERROR(Kernel, "Tried to duplicate invalid handle: %08X", handle);
+        return ERR_INVALID_HANDLE;
     }
-    pool.fill(nullptr);
-    next_id = INITIAL_NEXT_ID;
+    return Create(object);
 }
 
-Object* &HandleTable::operator [](Handle handle)
-{
-    _dbg_assert_msg_(Kernel, IsValid(handle), "GRABBING UNALLOCED KERNEL OBJ");
-    return pool[handle - HANDLE_OFFSET];
+ResultCode HandleTable::Close(Handle handle) {
+    if (!IsValid(handle))
+        return ERR_INVALID_HANDLE;
+
+    size_t slot = GetSlot(handle);
+    u16 generation = GetGeneration(handle);
+
+    intrusive_ptr_release(objects[slot]);
+    objects[slot] = nullptr;
+
+    generations[generation] = next_free_slot;
+    next_free_slot = slot;
+    return RESULT_SUCCESS;
 }
 
-void HandleTable::List() {
-    for (int i = 0; i < MAX_COUNT; i++) {
-        if (occupied[i]) {
-            if (pool[i]) {
-                LOG_DEBUG(Kernel, "KO %i: %s \"%s\"", i + HANDLE_OFFSET, pool[i]->GetTypeName().c_str(),
-                    pool[i]->GetName().c_str());
-            }
-        }
-    }
+bool HandleTable::IsValid(Handle handle) const {
+    size_t slot = GetSlot(handle);
+    u16 generation = GetGeneration(handle);
+
+    return slot < MAX_COUNT && objects[slot] != nullptr && generations[slot] == generation;
 }
 
-int HandleTable::GetCount() const {
-    return std::count(occupied.begin(), occupied.end(), true);
+Object* HandleTable::GetGeneric(Handle handle) const {
+    if (handle == CurrentThread) {
+        // TODO(yuriks) Directly return the pointer once this is possible.
+        handle = GetCurrentThreadHandle();
+    } else if (handle == CurrentProcess) {
+        LOG_ERROR(Kernel, "Current process (%08X) pseudo-handle not supported", CurrentProcess);
+        return nullptr;
+    }
+
+    if (!IsValid(handle)) {
+        return nullptr;
+    }
+    return objects[GetSlot(handle)];
 }
 
-Object* HandleTable::CreateByIDType(int type) {
-    LOG_ERROR(Kernel, "Unimplemented: %d.", type);
-    return nullptr;
+void HandleTable::Clear() {
+    for (size_t i = 0; i < MAX_COUNT; ++i) {
+        generations[i] = i + 1;
+        if (objects[i] != nullptr)
+            intrusive_ptr_release(objects[i]);
+        objects[i] = nullptr;
+    }
+    next_free_slot = 0;
 }
 
 /// Initialize the kernel
diff --git a/src/core/hle/kernel/kernel.h b/src/core/hle/kernel/kernel.h
index 27c406ad..7f86fd07 100644
--- a/src/core/hle/kernel/kernel.h
+++ b/src/core/hle/kernel/kernel.h
@@ -12,13 +12,17 @@
 typedef u32 Handle;
 typedef s32 Result;
 
+const Handle INVALID_HANDLE = 0;
+
 namespace Kernel {
 
-// From kernel.h. Declarations duplicated here to avoid a circular header dependency.
-class Thread;
-Thread* GetCurrentThread();
+// TODO: Verify code
+const ResultCode ERR_OUT_OF_HANDLES(ErrorDescription::OutOfMemory, ErrorModule::Kernel,
+        ErrorSummary::OutOfResource, ErrorLevel::Temporary);
+// TOOD: Verify code
+const ResultCode ERR_INVALID_HANDLE = InvalidHandle(ErrorModule::Kernel);
 
-enum KernelHandle {
+enum KernelHandle : Handle {
     CurrentThread   = 0xFFFF8000,
     CurrentProcess  = 0xFFFF8001,
 };
@@ -61,103 +65,127 @@ public:
         LOG_ERROR(Kernel, "(UNIMPLEMENTED)");
         return UnimplementedFunction(ErrorModule::Kernel);
     }
-};
 
-class HandleTable : NonCopyable {
-public:
-    HandleTable();
-    ~HandleTable() {}
+private:
+    friend void intrusive_ptr_add_ref(Object*);
+    friend void intrusive_ptr_release(Object*);
 
-    // Allocates a handle within the range and inserts the object into the map.
-    Handle Create(Object* obj, int range_bottom=INITIAL_NEXT_ID, int range_top=0x7FFFFFFF);
+    unsigned int ref_count = 0;
+};
 
-    static Object* CreateByIDType(int type);
+// Special functions that will later be used by boost::instrusive_ptr to do automatic ref-counting
+inline void intrusive_ptr_add_ref(Object* object) {
+    ++object->ref_count;
+}
 
-    template <class T>
-    void Destroy(Handle handle) {
-        if (Get<T>(handle)) {
-            occupied[handle - HANDLE_OFFSET] = false;
-            delete pool[handle - HANDLE_OFFSET];
-        }
+inline void intrusive_ptr_release(Object* object) {
+    if (--object->ref_count == 0) {
+        delete object;
     }
+}
 
-    bool IsValid(Handle handle) const;
+/**
+ * This class allows the creation of Handles, which are references to objects that can be tested
+ * for validity and looked up. Here they are used to pass references to kernel objects to/from the
+ * emulated process. it has been designed so that it follows the same handle format and has
+ * approximately the same restrictions as the handle manager in the CTR-OS.
+ *
+ * Handles contain two sub-fields: a slot index (bits 31:15) and a generation value (bits 14:0).
+ * The slot index is used to index into the arrays in this class to access the data corresponding
+ * to the Handle.
+ *
+ * To prevent accidental use of a freed Handle whose slot has already been reused, a global counter
+ * is kept and incremented every time a Handle is created. This is the Handle's "generation". The
+ * value of the counter is stored into the Handle as well as in the handle table (in the
+ * "generations" array). When looking up a handle, the Handle's generation must match with the
+ * value stored on the class, otherwise the Handle is considered invalid.
+ *
+ * To find free slots when allocating a Handle without needing to scan the entire object array, the
+ * generations field of unallocated slots is re-purposed as a linked list of indices to free slots.
+ * When a Handle is created, an index is popped off the list and used for the new Handle. When it
+ * is destroyed, it is again pushed onto the list to be re-used by the next allocation. It is
+ * likely that this allocation strategy differs from the one used in CTR-OS, but this hasn't been
+ * verified and isn't likely to cause any problems.
+ */
+class HandleTable final : NonCopyable {
+public:
+    HandleTable();
 
-    template <class T>
-    T* Get(Handle handle) {
-        if (handle == CurrentThread) {
-            return reinterpret_cast<T*>(GetCurrentThread());
-        }
+    /**
+     * Allocates a handle for the given object.
+     * @return The created Handle or one of the following errors:
+     *           - `ERR_OUT_OF_HANDLES`: the maximum number of handles has been exceeded.
+     */
+    ResultVal<Handle> Create(Object* obj);
 
-        if (handle < HANDLE_OFFSET || handle >= HANDLE_OFFSET + MAX_COUNT || !occupied[handle - HANDLE_OFFSET]) {
-            if (handle != 0) {
-                LOG_ERROR(Kernel, "Bad object handle %08x", handle);
-            }
-            return nullptr;
-        } else {
-            Object* t = pool[handle - HANDLE_OFFSET];
-            if (t->GetHandleType() != T::HANDLE_TYPE) {
-                LOG_ERROR(Kernel, "Wrong object type for %08x", handle);
-                return nullptr;
-            }
-            return static_cast<T*>(t);
-        }
-    }
+    /**
+     * Returns a new handle that points to the same object as the passed in handle.
+     * @return The duplicated Handle or one of the following errors:
+     *           - `ERR_INVALID_HANDLE`: an invalid handle was passed in.
+     *           - Any errors returned by `Create()`.
+     */
+    ResultVal<Handle> Duplicate(Handle handle);
 
-    // ONLY use this when you know the handle is valid.
-    template <class T>
-    T *GetFast(Handle handle) {
-        if (handle == CurrentThread) {
-            return reinterpret_cast<T*>(GetCurrentThread());
-        }
+    /**
+     * Closes a handle, removing it from the table and decreasing the object's ref-count.
+     * @return `RESULT_SUCCESS` or one of the following errors:
+     *           - `ERR_INVALID_HANDLE`: an invalid handle was passed in.
+     */
+    ResultCode Close(Handle handle);
 
-        const Handle realHandle = handle - HANDLE_OFFSET;
-        _dbg_assert_(Kernel, realHandle >= 0 && realHandle < MAX_COUNT && occupied[realHandle]);
-        return static_cast<T*>(pool[realHandle]);
-    }
+    /// Checks if a handle is valid and points to an existing object.
+    bool IsValid(Handle handle) const;
 
-    template <class T, typename ArgT>
-    void Iterate(bool func(T*, ArgT), ArgT arg) {
-        int type = T::GetStaticIDType();
-        for (int i = 0; i < MAX_COUNT; i++)
-        {
-            if (!occupied[i])
-                continue;
-            T* t = static_cast<T*>(pool[i]);
-            if (t->GetIDType() == type) {
-                if (!func(t, arg))
-                    break;
-            }
-        }
-    }
+    /**
+     * Looks up a handle.
+     * @returns Pointer to the looked-up object, or `nullptr` if the handle is not valid.
+     */
+    Object* GetGeneric(Handle handle) const;
 
-    bool GetIDType(Handle handle, HandleType* type) const {
-        if ((handle < HANDLE_OFFSET) || (handle >= HANDLE_OFFSET + MAX_COUNT) ||
-                !occupied[handle - HANDLE_OFFSET]) {
-            LOG_ERROR(Kernel, "Bad object handle %08X", handle);
-            return false;
+    /**
+     * Looks up a handle while verifying its type.
+     * @returns Pointer to the looked-up object, or `nullptr` if the handle is not valid or its
+     *          type differs from the handle type `T::HANDLE_TYPE`.
+     */
+    template <class T>
+    T* Get(Handle handle) const {
+        Object* object = GetGeneric(handle);
+        if (object != nullptr && object->GetHandleType() == T::HANDLE_TYPE) {
+            return static_cast<T*>(object);
         }
-        Object* t = pool[handle - HANDLE_OFFSET];
-        *type = t->GetHandleType();
-        return true;
+        return nullptr;
     }
 
-    Object* &operator [](Handle handle);
-    void List();
+    /// Closes all handles held in this table.
     void Clear();
-    int GetCount() const;
 
 private:
+    /**
+     * This is the maximum limit of handles allowed per process in CTR-OS. It can be further
+     * reduced by ExHeader values, but this is not emulated here.
+     */
+    static const size_t MAX_COUNT = 4096;
+
+    static size_t GetSlot(Handle handle)    { return handle >> 15; }
+    static u16 GetGeneration(Handle handle) { return handle & 0x7FFF; }
+
+    /// Stores the Object referenced by the handle or null if the slot is empty.
+    std::array<Object*, MAX_COUNT> objects;
 
-    enum {
-        MAX_COUNT       = 0x1000,
-        HANDLE_OFFSET   = 0x100,
-        INITIAL_NEXT_ID = 0x10,
-    };
+    /**
+     * The value of `next_generation` when the handle was created, used to check for validity. For
+     * empty slots, contains the index of the next free slot in the list.
+     */
+    std::array<u16, MAX_COUNT> generations;
+
+    /**
+     * Global counter of the number of created handles. Stored in `generations` when a handle is
+     * created, and wraps around to 1 when it hits 0x8000.
+     */
+    u16 next_generation;
 
-    std::array<Object*, MAX_COUNT> pool;
-    std::array<bool, MAX_COUNT> occupied;
-    int next_id;
+    /// Head of the free slots linked list.
+    u16 next_free_slot;
 };
 
 extern HandleTable g_handle_table;
diff --git a/src/core/hle/kernel/mutex.cpp b/src/core/hle/kernel/mutex.cpp
index 08462376..558068c7 100644
--- a/src/core/hle/kernel/mutex.cpp
+++ b/src/core/hle/kernel/mutex.cpp
@@ -87,7 +87,7 @@ void ReleaseThreadMutexes(Handle thread) {
     
     // Release every mutex that the thread holds, and resume execution on the waiting threads
     for (MutexMap::iterator iter = locked.first; iter != locked.second; ++iter) {
-        Mutex* mutex = g_handle_table.GetFast<Mutex>(iter->second);
+        Mutex* mutex = g_handle_table.Get<Mutex>(iter->second);
         ResumeWaitingThread(mutex);
     }
 
@@ -136,7 +136,8 @@ ResultCode ReleaseMutex(Handle handle) {
  */
 Mutex* CreateMutex(Handle& handle, bool initial_locked, const std::string& name) {
     Mutex* mutex = new Mutex;
-    handle = Kernel::g_handle_table.Create(mutex);
+    // TODO(yuriks): Fix error reporting
+    handle = Kernel::g_handle_table.Create(mutex).ValueOr(INVALID_HANDLE);
 
     mutex->locked = mutex->initial_locked = initial_locked;
     mutex->name = name;
diff --git a/src/core/hle/kernel/semaphore.cpp b/src/core/hle/kernel/semaphore.cpp
index 1dee15f1..6bc8066a 100644
--- a/src/core/hle/kernel/semaphore.cpp
+++ b/src/core/hle/kernel/semaphore.cpp
@@ -57,7 +57,8 @@ ResultCode CreateSemaphore(Handle* handle, s32 initial_count,
                           ErrorSummary::WrongArgument, ErrorLevel::Permanent);
 
     Semaphore* semaphore = new Semaphore;
-    *handle = g_handle_table.Create(semaphore);
+    // TOOD(yuriks): Fix error reporting
+    *handle = g_handle_table.Create(semaphore).ValueOr(INVALID_HANDLE);
 
     // When the semaphore is created, some slots are reserved for other threads,
     // and the rest is reserved for the caller thread
diff --git a/src/core/hle/kernel/shared_memory.cpp b/src/core/hle/kernel/shared_memory.cpp
index bd9d947a..cea1f6fa 100644
--- a/src/core/hle/kernel/shared_memory.cpp
+++ b/src/core/hle/kernel/shared_memory.cpp
@@ -32,7 +32,8 @@ public:
  */
 SharedMemory* CreateSharedMemory(Handle& handle, const std::string& name) {
     SharedMemory* shared_memory = new SharedMemory;
-    handle = Kernel::g_handle_table.Create(shared_memory);
+    // TOOD(yuriks): Fix error reporting
+    handle = Kernel::g_handle_table.Create(shared_memory).ValueOr(INVALID_HANDLE);
     shared_memory->name = name;
     return shared_memory;
 }
diff --git a/src/core/hle/kernel/thread.cpp b/src/core/hle/kernel/thread.cpp
index 2739bdd5..872df2d1 100644
--- a/src/core/hle/kernel/thread.cpp
+++ b/src/core/hle/kernel/thread.cpp
@@ -341,7 +341,8 @@ Thread* CreateThread(Handle& handle, const char* name, u32 entry_point, s32 prio
 
     Thread* thread = new Thread;
 
-    handle = Kernel::g_handle_table.Create(thread);
+    // TOOD(yuriks): Fix error reporting
+    handle = Kernel::g_handle_table.Create(thread).ValueOr(INVALID_HANDLE);
 
     thread_queue.push_back(handle);
     thread_ready_queue.prepare(priority);
diff --git a/src/core/hle/kernel/thread.h b/src/core/hle/kernel/thread.h
index 9396b6b2..0e1397cd 100644
--- a/src/core/hle/kernel/thread.h
+++ b/src/core/hle/kernel/thread.h
@@ -77,9 +77,6 @@ Handle ArbitrateHighestPriorityThread(u32 arbiter, u32 address);
 /// Arbitrate all threads currently waiting...
 void ArbitrateAllThreads(u32 arbiter, u32 address);
 
-/// Gets the current thread
-Thread* GetCurrentThread();
-
 /// Gets the current thread handle
 Handle GetCurrentThreadHandle();
 
diff --git a/src/core/hle/service/fs/archive.cpp b/src/core/hle/service/fs/archive.cpp
index 5746b58e..487bf3aa 100644
--- a/src/core/hle/service/fs/archive.cpp
+++ b/src/core/hle/service/fs/archive.cpp
@@ -133,7 +133,7 @@ public:
         case FileCommand::Close:
         {
             LOG_TRACE(Service_FS, "Close %s %s", GetTypeName().c_str(), GetName().c_str());
-            Kernel::g_handle_table.Destroy<File>(GetHandle());
+            backend->Close();
             break;
         }
 
@@ -189,7 +189,7 @@ public:
         case DirectoryCommand::Close:
         {
             LOG_TRACE(Service_FS, "Close %s %s", GetTypeName().c_str(), GetName().c_str());
-            Kernel::g_handle_table.Destroy<Directory>(GetHandle());
+            backend->Close();
             break;
         }
 
@@ -283,7 +283,8 @@ ResultVal<Handle> OpenFileFromArchive(ArchiveHandle archive_handle, const FileSy
     }
 
     auto file = Common::make_unique<File>(std::move(backend), path);
-    Handle handle = Kernel::g_handle_table.Create(file.release());
+    // TOOD(yuriks): Fix error reporting
+    Handle handle = Kernel::g_handle_table.Create(file.release()).ValueOr(INVALID_HANDLE);
     return MakeResult<Handle>(handle);
 }
 
@@ -388,7 +389,8 @@ ResultVal<Handle> OpenDirectoryFromArchive(ArchiveHandle archive_handle, const F
     }
 
     auto directory = Common::make_unique<Directory>(std::move(backend), path);
-    Handle handle = Kernel::g_handle_table.Create(directory.release());
+    // TOOD(yuriks): Fix error reporting
+    Handle handle = Kernel::g_handle_table.Create(directory.release()).ValueOr(INVALID_HANDLE);
     return MakeResult<Handle>(handle);
 }
 
diff --git a/src/core/hle/service/service.cpp b/src/core/hle/service/service.cpp
index e9a7973b..0f3cc2aa 100644
--- a/src/core/hle/service/service.cpp
+++ b/src/core/hle/service/service.cpp
@@ -56,7 +56,8 @@ Manager::~Manager() {
 
 /// Add a service to the manager (does not create it though)
 void Manager::AddService(Interface* service) {
-    m_port_map[service->GetPortName()] = Kernel::g_handle_table.Create(service);
+    // TOOD(yuriks): Fix error reporting
+    m_port_map[service->GetPortName()] = Kernel::g_handle_table.Create(service).ValueOr(INVALID_HANDLE);
     m_services.push_back(service);
 }
 
diff --git a/src/core/hle/service/service.h b/src/core/hle/service/service.h
index 9d5828fd..28b4ccd1 100644
--- a/src/core/hle/service/service.h
+++ b/src/core/hle/service/service.h
@@ -54,7 +54,8 @@ public:
 
     /// Allocates a new handle for the service
     Handle CreateHandle(Kernel::Object *obj) {
-        Handle handle = Kernel::g_handle_table.Create(obj);
+        // TODO(yuriks): Fix error reporting
+        Handle handle = Kernel::g_handle_table.Create(obj).ValueOr(INVALID_HANDLE);
         m_handles.push_back(handle);
         return handle;
     }
@@ -62,7 +63,7 @@ public:
     /// Frees a handle from the service
     template <class T>
     void DeleteHandle(const Handle handle) {
-        Kernel::g_handle_table.Destroy<T>(handle);
+        Kernel::g_handle_table.Close(handle);
         m_handles.erase(std::remove(m_handles.begin(), m_handles.end(), handle), m_handles.end());
     }
 
diff --git a/src/core/hle/svc.cpp b/src/core/hle/svc.cpp
index a48ac09a..25944fc6 100644
--- a/src/core/hle/svc.cpp
+++ b/src/core/hle/svc.cpp
@@ -119,11 +119,9 @@ static Result WaitSynchronization1(Handle handle, s64 nano_seconds) {
     // TODO(bunnei): Do something with nano_seconds, currently ignoring this
     bool wait_infinite = (nano_seconds == -1); // Used to wait until a thread has terminated
 
-    if (!Kernel::g_handle_table.IsValid(handle)) {
+    Kernel::Object* object = Kernel::g_handle_table.GetGeneric(handle);
+    if (object == nullptr)
         return InvalidHandle(ErrorModule::Kernel).raw;
-    }
-    Kernel::Object* object = Kernel::g_handle_table.GetFast<Kernel::Object>(handle);
-    _dbg_assert_(Kernel, object != nullptr);
 
     LOG_TRACE(Kernel_SVC, "called handle=0x%08X(%s:%s), nanoseconds=%lld", handle, object->GetTypeName().c_str(),
             object->GetName().c_str(), nano_seconds);
@@ -150,10 +148,9 @@ static Result WaitSynchronizationN(s32* out, Handle* handles, s32 handle_count,
 
     // Iterate through each handle, synchronize kernel object
     for (s32 i = 0; i < handle_count; i++) {
-        if (!Kernel::g_handle_table.IsValid(handles[i])) {
+        Kernel::Object* object = Kernel::g_handle_table.GetGeneric(handles[i]);
+        if (object == nullptr)
             return InvalidHandle(ErrorModule::Kernel).raw;
-        }
-        Kernel::Object* object = Kernel::g_handle_table.GetFast<Kernel::Object>(handles[i]);
 
         LOG_TRACE(Kernel_SVC, "\thandle[%d] = 0x%08X(%s:%s)", i, handles[i], object->GetTypeName().c_str(),
             object->GetName().c_str());
@@ -321,19 +318,12 @@ static Result CreateEvent(Handle* evt, u32 reset_type) {
 
 /// Duplicates a kernel handle
 static Result DuplicateHandle(Handle* out, Handle handle) {
-    LOG_WARNING(Kernel_SVC, "(STUBBED) called handle=0x%08X", handle);
-
-    // Translate kernel handles -> real handles
-    if (handle == Kernel::CurrentThread) {
-        handle = Kernel::GetCurrentThreadHandle();
+    ResultVal<Handle> out_h = Kernel::g_handle_table.Duplicate(handle);
+    if (out_h.Succeeded()) {
+        *out = *out_h;
+        LOG_TRACE(Kernel_SVC, "duplicated 0x%08X to 0x%08X", handle, *out);
     }
-    _assert_msg_(KERNEL, (handle != Kernel::CurrentProcess),
-        "(UNIMPLEMENTED) process handle duplication!");
-
-    // TODO(bunnei): FixMe - This is a hack to return the handle that we were asked to duplicate.
-    *out = handle;
-
-    return 0;
+    return out_h.Code().raw;
 }
 
 /// Signals an event