Kernel: Make sure we unmap the TLS region when a thread exits

Previously the TLS region would get leaked which was noticible
when creating/destroying a lot of threads and then inspecting
the region map.

Kernel/Thread.cpp

@@ -266,6 +266,12 @@ void Thread::exit(void* exit_value)
     set_should_die();
     u32 unlock_count;
     [[maybe_unused]] auto rc = unlock_process_if_locked(unlock_count);
+    if (m_thread_specific_range.has_value()) {
+        auto* region = process().space().find_region_from_range(m_thread_specific_range.value());
+        VERIFY(region);
+        if (!process().space().deallocate_region(*region))
+            dbgln("Failed to unmap TLS range, exiting thread anyway.");
+    }
     die_if_needed();
 }
 
@@ -1021,6 +1027,8 @@ KResult Thread::make_thread_specific_region(Badge<Process>)
     if (region_or_error.is_error())
         return region_or_error.error();
 
+    m_thread_specific_range = range.value();
+
     SmapDisabler disabler;
     auto* thread_specific_data = (ThreadSpecificData*)region_or_error.value()->vaddr().offset(align_up_to(process().m_master_tls_size, thread_specific_region_alignment())).as_ptr();
     auto* thread_local_storage = (u8*)((u8*)thread_specific_data) - align_up_to(process().m_master_tls_size, process().m_master_tls_alignment);

Kernel/Thread.h

@@ -29,6 +29,7 @@
 #include <Kernel/ThreadTracer.h>
 #include <Kernel/TimerQueue.h>
 #include <Kernel/UnixTypes.h>
+#include <Kernel/VM/Range.h>
 #include <LibC/fd_set.h>
 #include <LibC/signal_numbers.h>
 
@@ -1220,6 +1221,7 @@ private:
     u32 m_kernel_stack_top { 0 };
     OwnPtr<Region> m_kernel_stack_region;
     VirtualAddress m_thread_specific_data;
+    Optional<Range> m_thread_specific_range;
     Array<SignalActionData, NSIG> m_signal_action_data;
     Blocker* m_blocker { nullptr };