kernel/svc: Handle thread handles within GetProcessId

If a thread handle is passed to svcGetProcessId, the kernel attempts to
access the process ID via the thread's instance's owning process.

Technically, this function should also be handling the kernel debug
objects as well, however we currently don't handle those kernel objects
yet, so I've left a note via a comment about it to remind myself when
implementing it in the future.

src/core/hle/kernel/svc.cpp

@@ -364,20 +364,33 @@ static ResultCode GetThreadId(u64* thread_id, Handle thread_handle) {
     return RESULT_SUCCESS;
 }
 
-/// Get the ID of the specified process
-static ResultCode GetProcessId(u64* process_id, Handle process_handle) {
-    LOG_TRACE(Kernel_SVC, "called process=0x{:08X}", process_handle);
+/// Gets the ID of the specified process or a specified thread's owning process.
+static ResultCode GetProcessId(u64* process_id, Handle handle) {
+    LOG_DEBUG(Kernel_SVC, "called handle=0x{:08X}", handle);
 
     const auto& handle_table = Core::CurrentProcess()->GetHandleTable();
-    const SharedPtr<Process> process = handle_table.Get<Process>(process_handle);
-    if (!process) {
-        LOG_ERROR(Kernel_SVC, "Process handle does not exist, process_handle=0x{:08X}",
-                  process_handle);
-        return ERR_INVALID_HANDLE;
+    const SharedPtr<Process> process = handle_table.Get<Process>(handle);
+    if (process) {
+        *process_id = process->GetProcessID();
+        return RESULT_SUCCESS;
     }
 
-    *process_id = process->GetProcessID();
-    return RESULT_SUCCESS;
+    const SharedPtr<Thread> thread = handle_table.Get<Thread>(handle);
+    if (thread) {
+        const Process* const owner_process = thread->GetOwnerProcess();
+        if (!owner_process) {
+            LOG_ERROR(Kernel_SVC, "Non-existent owning process encountered.");
+            return ERR_INVALID_HANDLE;
+        }
+
+        *process_id = owner_process->GetProcessID();
+        return RESULT_SUCCESS;
+    }
+
+    // NOTE: This should also handle debug objects before returning.
+
+    LOG_ERROR(Kernel_SVC, "Handle does not exist, handle=0x{:08X}", handle);
+    return ERR_INVALID_HANDLE;
 }
 
 /// Default thread wakeup callback for WaitSynchronization