Kernel: Simplify Process factory functions

- Instead of taking the first new thread as an out-parameter, we now
  bundle the process and its first thread in a struct and use that
  as the return value.

- Make all Process factory functions return ErrorOr. Use this to convert
  some places to more TRY().

- Drop the "try_" prefix on Process factory functions.

1 files changed, 11 insertions, 6 deletions

diff --git a/Kernel/Process.h b/Kernel/Process.h
index e1b5220fcb..ccf5684169 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -185,15 +185,20 @@ public:
         Yes
     };
 
+    struct ProcessAndFirstThread {
+        NonnullRefPtr<Process> process;
+        NonnullLockRefPtr<Thread> first_thread;
+    };
+
     template<typename EntryFunction>
-    static RefPtr<Process> create_kernel_process(LockRefPtr<Thread>& first_thread, NonnullOwnPtr<KString> name, EntryFunction entry, u32 affinity = THREAD_AFFINITY_DEFAULT, RegisterProcess do_register = RegisterProcess::Yes)
+    static ErrorOr<ProcessAndFirstThread> create_kernel_process(NonnullOwnPtr<KString> name, EntryFunction entry, u32 affinity = THREAD_AFFINITY_DEFAULT, RegisterProcess do_register = RegisterProcess::Yes)
     {
         auto* entry_func = new EntryFunction(move(entry));
-        return create_kernel_process(first_thread, move(name), &Process::kernel_process_trampoline<EntryFunction>, entry_func, affinity, do_register);
+        return create_kernel_process(move(name), &Process::kernel_process_trampoline<EntryFunction>, entry_func, affinity, do_register);
     }
 
-    static RefPtr<Process> create_kernel_process(LockRefPtr<Thread>& first_thread, NonnullOwnPtr<KString> name, void (*entry)(void*), void* entry_data = nullptr, u32 affinity = THREAD_AFFINITY_DEFAULT, RegisterProcess do_register = RegisterProcess::Yes);
-    static ErrorOr<NonnullRefPtr<Process>> try_create_user_process(LockRefPtr<Thread>& first_thread, StringView path, UserID, GroupID, Vector<NonnullOwnPtr<KString>> arguments, Vector<NonnullOwnPtr<KString>> environment, TTY*);
+    static ErrorOr<ProcessAndFirstThread> create_kernel_process(NonnullOwnPtr<KString> name, void (*entry)(void*), void* entry_data = nullptr, u32 affinity = THREAD_AFFINITY_DEFAULT, RegisterProcess do_register = RegisterProcess::Yes);
+    static ErrorOr<ProcessAndFirstThread> create_user_process(StringView path, UserID, GroupID, Vector<NonnullOwnPtr<KString>> arguments, Vector<NonnullOwnPtr<KString>> environment, TTY*);
     static void register_new(Process&);
 
     ~Process();
@@ -594,8 +599,8 @@ private:
     bool remove_thread(Thread&);
 
     Process(NonnullOwnPtr<KString> name, NonnullRefPtr<Credentials>, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> current_directory, RefPtr<Custody> executable, TTY* tty, UnveilNode unveil_tree, UnveilNode exec_unveil_tree);
-    static ErrorOr<NonnullRefPtr<Process>> try_create(LockRefPtr<Thread>& first_thread, NonnullOwnPtr<KString> name, UserID, GroupID, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> current_directory = nullptr, RefPtr<Custody> executable = nullptr, TTY* = nullptr, Process* fork_parent = nullptr);
-    ErrorOr<void> attach_resources(NonnullOwnPtr<Memory::AddressSpace>&&, LockRefPtr<Thread>& first_thread, Process* fork_parent);
+    static ErrorOr<ProcessAndFirstThread> create(NonnullOwnPtr<KString> name, UserID, GroupID, ProcessID ppid, bool is_kernel_process, RefPtr<Custody> current_directory = nullptr, RefPtr<Custody> executable = nullptr, TTY* = nullptr, Process* fork_parent = nullptr);
+    ErrorOr<NonnullLockRefPtr<Thread>> attach_resources(NonnullOwnPtr<Memory::AddressSpace>&&, Process* fork_parent);
     static ProcessID allocate_pid();
 
     void kill_threads_except_self();