kernel/svc: Implement svcUnmapProcessCodeMemory

Essentially performs the inverse of svcMapProcessCodeMemory. This unmaps
the aliasing region first, then restores the general traits of the
aliased memory.

What this entails, is:

- Restoring Read/Write permissions to the VMA.
- Restoring its memory state to reflect it as a general heap memory region.
- Clearing the memory attributes on the region.

src/core/hle/kernel/svc.cpp

@@ -1257,6 +1257,74 @@ static ResultCode MapProcessCodeMemory(Core::System& system, Handle process_hand
     return vm_manager.MapCodeMemory(dst_address, src_address, size);
 }
 
+ResultCode UnmapProcessCodeMemory(Core::System& system, Handle process_handle, u64 dst_address,
+                                  u64 src_address, u64 size) {
+    LOG_DEBUG(Kernel_SVC,
+              "called. process_handle=0x{:08X}, dst_address=0x{:016X}, src_address=0x{:016X}, "
+              "size=0x{:016X}",
+              process_handle, dst_address, src_address, size);
+
+    if (!Common::Is4KBAligned(dst_address)) {
+        LOG_ERROR(Kernel_SVC, "dst_address is not page-aligned (dst_address=0x{:016X}).",
+                  dst_address);
+        return ERR_INVALID_ADDRESS;
+    }
+
+    if (!Common::Is4KBAligned(src_address)) {
+        LOG_ERROR(Kernel_SVC, "src_address is not page-aligned (src_address=0x{:016X}).",
+                  src_address);
+        return ERR_INVALID_ADDRESS;
+    }
+
+    if (size == 0 || Common::Is4KBAligned(size)) {
+        LOG_ERROR(Kernel_SVC, "Size is zero or not page-aligned (size=0x{:016X}).", size);
+        return ERR_INVALID_SIZE;
+    }
+
+    if (!IsValidAddressRange(dst_address, size)) {
+        LOG_ERROR(Kernel_SVC,
+                  "Destination address range overflows the address space (dst_address=0x{:016X}, "
+                  "size=0x{:016X}).",
+                  dst_address, size);
+        return ERR_INVALID_ADDRESS_STATE;
+    }
+
+    if (!IsValidAddressRange(src_address, size)) {
+        LOG_ERROR(Kernel_SVC,
+                  "Source address range overflows the address space (src_address=0x{:016X}, "
+                  "size=0x{:016X}).",
+                  src_address, size);
+        return ERR_INVALID_ADDRESS_STATE;
+    }
+
+    const auto& handle_table = system.Kernel().CurrentProcess()->GetHandleTable();
+    auto process = handle_table.Get<Process>(process_handle);
+    if (!process) {
+        LOG_ERROR(Kernel_SVC, "Invalid process handle specified (handle=0x{:08X}).",
+                  process_handle);
+        return ERR_INVALID_HANDLE;
+    }
+
+    auto& vm_manager = process->VMManager();
+    if (!vm_manager.IsWithinAddressSpace(src_address, size)) {
+        LOG_ERROR(Kernel_SVC,
+                  "Source address range is not within the address space (src_address=0x{:016X}, "
+                  "size=0x{:016X}).",
+                  src_address, size);
+        return ERR_INVALID_ADDRESS_STATE;
+    }
+
+    if (!vm_manager.IsWithinASLRRegion(dst_address, size)) {
+        LOG_ERROR(Kernel_SVC,
+                  "Destination address range is not within the ASLR region (dst_address=0x{:016X}, "
+                  "size=0x{:016X}).",
+                  dst_address, size);
+        return ERR_INVALID_MEMORY_RANGE;
+    }
+
+    return vm_manager.UnmapCodeMemory(dst_address, src_address, size);
+}
+
 /// Exits the current process
 static void ExitProcess(Core::System& system) {
     auto* current_process = system.Kernel().CurrentProcess();
@@ -2286,7 +2354,7 @@ static const FunctionDef SVC_Table[] = {
     {0x75, nullptr, "UnmapProcessMemory"},
     {0x76, SvcWrap<QueryProcessMemory>, "QueryProcessMemory"},
     {0x77, SvcWrap<MapProcessCodeMemory>, "MapProcessCodeMemory"},
-    {0x78, nullptr, "UnmapProcessCodeMemory"},
+    {0x78, SvcWrap<UnmapProcessCodeMemory>, "UnmapProcessCodeMemory"},
     {0x79, nullptr, "CreateProcess"},
     {0x7A, nullptr, "StartProcess"},
     {0x7B, nullptr, "TerminateProcess"},