kern: implement SvcGetThreadContext3

libraries/libmesosphere/include/mesosphere/arch/arm64/kern_k_exception_context.hpp

@@ -22,7 +22,8 @@ namespace ams::kern::arch::arm64 {
         u64 x[(30 - 0) + 1];
         u64 sp;
         u64 pc;
-        u64 psr;
+        u32 psr;
+        u32 write;
         u64 tpidr;
         u64 reserved;
     };

libraries/libmesosphere/include/mesosphere/arch/arm64/kern_k_thread_context.hpp

@@ -74,7 +74,11 @@ namespace ams::kern::arch::arm64 {
 
             void CloneFpuStatus();
 
+            const u128 *GetFpuRegisters() const { return this->fpu_registers; }
+
             /* TODO: More methods (especially FPU management) */
     };
 
+    void GetUserContext(ams::svc::ThreadContext *out, const KThread *thread);
+
 }