Kernel/aarch64: Implement Thread Local Storage

This commit adds Processor::set_thread_specific_data, and this function
is used to factor out architecture specific implementation of setting
the thread specific data. This function is implemented for
aarch64 and x86_64, and the callsites are changed to use this function
instead.

Kernel/Arch/aarch64/ASM_wrapper.h

@@ -37,6 +37,11 @@ inline void set_sp_el1(FlatPtr sp_el1)
     asm("msr sp_el1, %[value]" ::[value] "r"(sp_el1));
 }
 
+inline void set_tpidr_el0(FlatPtr tpidr_el0)
+{
+    asm("msr tpidr_el0, %[value]" ::[value] "r"(tpidr_el0));
+}
+
 inline void flush()
 {
     asm("dsb ish");

Kernel/Arch/aarch64/Processor.cpp

@@ -454,6 +454,8 @@ extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread)
 
     to_thread->set_cpu(Processor::current().id());
 
+    Processor::set_thread_specific_data(to_thread->thread_specific_data());
+
     auto in_critical = to_thread->saved_critical();
     VERIFY(in_critical > 0);
     Processor::restore_critical(in_critical);
@@ -466,4 +468,9 @@ StringView Processor::platform_string()
     return "aarch64"sv;
 }
 
+void Processor::set_thread_specific_data(VirtualAddress thread_specific_data)
+{
+    Aarch64::Asm::set_tpidr_el0(thread_specific_data.get());
+}
+
 }

Kernel/Arch/aarch64/Processor.h

@@ -279,6 +279,8 @@ public:
 
     static StringView platform_string();
 
+    static void set_thread_specific_data(VirtualAddress thread_specific_data);
+
 private:
     Processor(Processor const&) = delete;