2 files changed, 191 insertions, 11 deletions

diff --git a/src/core/hle/kernel/k_slab_heap.h b/src/core/hle/kernel/k_slab_heap.h
index 81d472a3e..0ad74b0a0 100644
--- a/src/core/hle/kernel/k_slab_heap.h
+++ b/src/core/hle/kernel/k_slab_heap.h
@@ -4,34 +4,213 @@
 
 #pragma once
 
+#include <atomic>
+
+#include "common/assert.h"
+#include "common/common_types.h"
+
 namespace Kernel {
 
 class KernelCore;
 
-/// This is a placeholder class to manage slab heaps for kernel objects. For now, we just allocate
-/// these with new/delete, but this can be re-implemented later to allocate these in emulated
-/// memory.
+namespace impl {
+
+class KSlabHeapImpl final : NonCopyable {
+public:
+    struct Node {
+        Node* next{};
+    };
+
+    constexpr KSlabHeapImpl() = default;
+
+    void Initialize(std::size_t size) {
+        ASSERT(head == nullptr);
+        obj_size = size;
+    }
+
+    constexpr std::size_t GetObjectSize() const {
+        return obj_size;
+    }
+
+    Node* GetHead() const {
+        return head;
+    }
+
+    void* Allocate() {
+        Node* ret = head.load();
+
+        do {
+            if (ret == nullptr) {
+                break;
+            }
+        } while (!head.compare_exchange_weak(ret, ret->next));
+
+        return ret;
+    }
+
+    void Free(void* obj) {
+        Node* node = static_cast<Node*>(obj);
+
+        Node* cur_head = head.load();
+        do {
+            node->next = cur_head;
+        } while (!head.compare_exchange_weak(cur_head, node));
+    }
+
+private:
+    std::atomic<Node*> head{};
+    std::size_t obj_size{};
+};
+
+} // namespace impl
+
+class KSlabHeapBase : NonCopyable {
+public:
+    constexpr KSlabHeapBase() = default;
+
+    constexpr bool Contains(uintptr_t addr) const {
+        return start <= addr && addr < end;
+    }
+
+    constexpr std::size_t GetSlabHeapSize() const {
+        return (end - start) / GetObjectSize();
+    }
+
+    constexpr std::size_t GetObjectSize() const {
+        return impl.GetObjectSize();
+    }
+
+    constexpr uintptr_t GetSlabHeapAddress() const {
+        return start;
+    }
+
+    std::size_t GetObjectIndexImpl(const void* obj) const {
+        return (reinterpret_cast<uintptr_t>(obj) - start) / GetObjectSize();
+    }
+
+    std::size_t GetPeakIndex() const {
+        return GetObjectIndexImpl(reinterpret_cast<const void*>(peak));
+    }
+
+    void* AllocateImpl() {
+        return impl.Allocate();
+    }
+
+    void FreeImpl(void* obj) {
+        // Don't allow freeing an object that wasn't allocated from this heap
+        ASSERT(Contains(reinterpret_cast<uintptr_t>(obj)));
+
+        impl.Free(obj);
+    }
+
+    void InitializeImpl(std::size_t obj_size, void* memory, std::size_t memory_size) {
+        // Ensure we don't initialize a slab using null memory
+        ASSERT(memory != nullptr);
+
+        // Initialize the base allocator
+        impl.Initialize(obj_size);
+
+        // Set our tracking variables
+        const std::size_t num_obj = (memory_size / obj_size);
+        start = reinterpret_cast<uintptr_t>(memory);
+        end = start + num_obj * obj_size;
+        peak = start;
+
+        // Free the objects
+        u8* cur = reinterpret_cast<u8*>(end);
+
+        for (std::size_t i{}; i < num_obj; i++) {
+            cur -= obj_size;
+            impl.Free(cur);
+        }
+    }
+
+private:
+    using Impl = impl::KSlabHeapImpl;
+
+    Impl impl;
+    uintptr_t peak{};
+    uintptr_t start{};
+    uintptr_t end{};
+};
 
 template <typename T>
-class KSlabHeap final : NonCopyable {
+class KSlabHeap final : public KSlabHeapBase {
 public:
-    KSlabHeap() = default;
+    enum class AllocationType {
+        Host,
+        Guest,
+    };
 
-    void Initialize([[maybe_unused]] void* memory, [[maybe_unused]] std::size_t memory_size) {
-        // Placeholder that should initialize the backing slab heap implementation.
+    explicit constexpr KSlabHeap(AllocationType allocation_type_ = AllocationType::Host)
+        : KSlabHeapBase(), allocation_type{allocation_type_} {}
+
+    void Initialize(void* memory, std::size_t memory_size) {
+        if (allocation_type == AllocationType::Guest) {
+            InitializeImpl(sizeof(T), memory, memory_size);
+        }
     }
 
     T* Allocate() {
-        return new T();
+        switch (allocation_type) {
+        case AllocationType::Host:
+            // Fallback for cases where we do not yet support allocating guest memory from the slab
+            // heap, such as for kernel memory regions.
+            return new T;
+
+        case AllocationType::Guest:
+            T* obj = static_cast<T*>(AllocateImpl());
+            if (obj != nullptr) {
+                new (obj) T();
+            }
+            return obj;
+        }
+
+        UNREACHABLE_MSG("Invalid AllocationType {}", allocation_type);
+        return nullptr;
     }
 
     T* AllocateWithKernel(KernelCore& kernel) {
-        return new T(kernel);
+        switch (allocation_type) {
+        case AllocationType::Host:
+            // Fallback for cases where we do not yet support allocating guest memory from the slab
+            // heap, such as for kernel memory regions.
+            return new T(kernel);
+
+        case AllocationType::Guest:
+            T* obj = static_cast<T*>(AllocateImpl());
+            if (obj != nullptr) {
+                new (obj) T(kernel);
+            }
+            return obj;
+        }
+
+        UNREACHABLE_MSG("Invalid AllocationType {}", allocation_type);
+        return nullptr;
     }
 
     void Free(T* obj) {
-        delete obj;
+        switch (allocation_type) {
+        case AllocationType::Host:
+            // Fallback for cases where we do not yet support allocating guest memory from the slab
+            // heap, such as for kernel memory regions.
+            delete obj;
+            return;
+
+        case AllocationType::Guest:
+            FreeImpl(obj);
+            return;
+        }
+
+        UNREACHABLE_MSG("Invalid AllocationType {}", allocation_type);
     }
+
+    constexpr std::size_t GetObjectIndex(const T* obj) const {
+        return GetObjectIndexImpl(obj);
+    }
+
+private:
+    const AllocationType allocation_type;
 };
 
 } // namespace Kernel
diff --git a/src/core/hle/kernel/kernel.cpp b/src/core/hle/kernel/kernel.cpp
index 7ca2a2ef1..0ffb78d51 100644
--- a/src/core/hle/kernel/kernel.cpp
+++ b/src/core/hle/kernel/kernel.cpp
@@ -620,7 +620,8 @@ struct KernelCore::Impl {
 
     void InitializePageSlab() {
         // Allocate slab heaps
-        user_slab_heap_pages = std::make_unique<KSlabHeap<Page>>();
+        user_slab_heap_pages =
+            std::make_unique<KSlabHeap<Page>>(KSlabHeap<Page>::AllocationType::Guest);
 
         // TODO(ameerj): This should be derived, not hardcoded within the kernel
         constexpr u64 user_slab_heap_size{0x3de000};