[core] Unstub AliasRegionExtraSize (#260)

This implementation is basically usable for up to 8GB of DRAM which you can set in the emulator.
It should ensure that the alias or map region for the virtual address space is bigger when requested.
8GB DRAM is the size of Nintendos DRAM sticks in the developers kit.
Going above 8GB DRAM while emulating a game is not recommended.
That is why this implementation.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/260
Reviewed-by: Shinmegumi <shinmegumi@eden-emu.dev>
Co-authored-by: SDK-Chan <sdkchan@eden-emu.dev>
Co-committed-by: SDK-Chan <sdkchan@eden-emu.dev>

src/core/hle/kernel/k_page_table_base.h

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -715,6 +718,17 @@ public:
         return m_address_space_width;
     }
 
+    size_t CalculateAliasRegionExtraSize() const {
+        const size_t baseline = 64ull << 30;   // Mostly appropriate for DRAM values <= 8GB
+        const size_t region = GetAliasRegionSize();
+
+        if (region > baseline) {
+            return region - baseline;
+        }
+
+        return 0;
+    }
+
 public:
     // Linear mapped
     static u8* GetLinearMappedVirtualPointer(KernelCore& kernel, KPhysicalAddress addr) {

src/core/hle/kernel/k_process_page_table.h

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -410,6 +413,9 @@ public:
     size_t GetAliasRegionSize() const {
         return m_page_table.GetAliasRegionSize();
     }
+    size_t GetAliasRegionExtraSize() const {
+        return m_page_table.CalculateAliasRegionExtraSize();
+    }
     size_t GetStackRegionSize() const {
         return m_page_table.GetStackRegionSize();
     }

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

@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -37,8 +40,8 @@ Result GetInfo(Core::System& system, u64* result, InfoType info_id_type, Handle
     case InfoType::TotalNonSystemMemorySize:
     case InfoType::UsedNonSystemMemorySize:
     case InfoType::IsApplication:
-    case InfoType::FreeThreadCount:
-    case InfoType::AliasRegionExtraSize: {
+    case InfoType::FreeThreadCount:
+    case InfoType::AliasRegionExtraSize: {
         R_UNLESS(info_sub_id == 0, ResultInvalidEnumValue);
 
         const auto& handle_table = GetCurrentProcess(system.Kernel()).GetHandleTable();
@@ -61,7 +64,6 @@ Result GetInfo(Core::System& system, u64* result, InfoType info_id_type, Handle
         case InfoType::AliasRegionSize:
             *result = process->GetPageTable().GetAliasRegionSize();
             R_SUCCEED();
-
         case InfoType::HeapRegionAddress:
             *result = GetInteger(process->GetPageTable().GetHeapRegionStart());
             R_SUCCEED();
@@ -135,10 +137,17 @@ Result GetInfo(Core::System& system, u64* result, InfoType info_id_type, Handle
             }
             R_SUCCEED();
 
-        case InfoType::AliasRegionExtraSize:
-            // TODO (jarrodnorwell): do this when KIP's NPDM header is finished
-            R_SUCCEED();
-
+        case InfoType::AliasRegionExtraSize: {
+            if (info_sub_id != 0) {
+                return ResultInvalidCombination;
+            }
+
+            KProcess* current_process = GetCurrentProcessPointer(system.Kernel());
+            *result = current_process->GetPageTable().GetAliasRegionExtraSize();
+
+            R_SUCCEED();
+        }
+
         default:
             break;
         }