Kernel: Generate coredump backtraces from "threads for coredump" list

This broke with the change that gave each process a list of its own
threads. Since threads are removed slightly earlier from that list
during process teardown, we're not able to use it for generating
coredump backtraces. Fortunately we have the "threads for coredump"
list for just this purpose. :^)

Kernel/CoreDump.cpp

@@ -240,7 +240,7 @@ ByteBuffer CoreDump::create_notes_threads_data() const
 {
     ByteBuffer threads_data;
 
-    m_process->for_each_thread([&](Thread& thread) {
+    for (auto& thread : m_process->threads_for_coredump({})) {
         ByteBuffer entry_buff;
 
         ELF::Core::ThreadInfo info {};
@@ -251,9 +251,7 @@ ByteBuffer CoreDump::create_notes_threads_data() const
         entry_buff.append((void*)&info, sizeof(info));
 
         threads_data += entry_buff;
-
-        return IterationDecision::Continue;
-    });
+    }
     return threads_data;
 }
 

Kernel/Process.cpp

@@ -677,7 +677,7 @@ void Process::die()
     m_tty = nullptr;
 
     for_each_thread([&](auto& thread) {
-        m_threads_for_coredump.append(&thread);
+        m_threads_for_coredump.append(thread);
         return IterationDecision::Continue;
     });
 

Kernel/Process.h

@@ -206,6 +206,9 @@ public:
     template<typename Callback>
     IterationDecision for_each_thread(Callback) const;
 
+    template<typename Callback>
+    IterationDecision for_each_thread_in_coredump(Callback) const;
+
     void die();
     void finalize();
 
@@ -500,6 +503,8 @@ public:
     HashMap<String, String>& coredump_metadata() { return m_coredump_metadata; }
     const HashMap<String, String>& coredump_metadata() const { return m_coredump_metadata; }
 
+    const NonnullRefPtrVector<Thread>& threads_for_coredump(Badge<CoreDump>) const { return m_threads_for_coredump; }
+
     PerformanceEventBuffer* perf_events() { return m_perf_event_buffer; }
 
 private:
@@ -662,7 +667,7 @@ private:
 
     HashMap<String, String> m_coredump_metadata;
 
-    Vector<RefPtr<Thread>> m_threads_for_coredump;
+    NonnullRefPtrVector<Thread> m_threads_for_coredump;
 };
 
 extern InlineLinkedList<Process>* g_processes;

Kernel/Thread.h

@@ -785,6 +785,7 @@ public:
     u32 stack_ptr() const { return m_tss.esp; }
 
     RegisterState& get_register_dump_from_stack();
+    const RegisterState& get_register_dump_from_stack() const { return const_cast<Thread*>(this)->get_register_dump_from_stack(); }
 
     TSS32& tss() { return m_tss; }
     const TSS32& tss() const { return m_tss; }