1 files changed, 36 insertions, 0 deletions
diff --git a/arch/x86_64/src/context_switching/main.cpp b/arch/x86_64/src/context_switching/main.cpp
new file mode 100644
index 0000000..b682e79
--- /dev/null
+++ b/arch/x86_64/src/context_switching/main.cpp
@@ -0,0 +1,36 @@
+#include "arch/context_switching/main.hpp"
+
+#include "arch/boot/pointers.hpp"
+#include "arch/exception_handling/assert.hpp"
+#include "arch/kernel/cpu/if.hpp"
+#include "arch/kernel/cpu/jmp.hpp"
+#include "arch/kernel/cpu/tr.hpp"
+
+namespace teachos::arch::context_switching
+{
+  auto initialize_descriptor_tables() -> descriptor_tables
+  {
+    decltype(auto) global_descriptor_table = segment_descriptor_table::initialize_global_descriptor_table();
+
+    // TODO: Replace random construction with return value of initialization.
+    interrupt_descriptor_table::interrupt_descriptor_table idt{};
+    interrupt_descriptor_table::initialize_interrupt_descriptor_table();
+
+    kernel::cpu::jmp((uint64_t)&global_descriptor_table.at(1), boot::segment_register_reload_pointer);
+
+    // Load task state segment descriptor from the last element in the global descriptor table, done by calculating
+    // offset in bytes to the start of the segment descriptor (5 * 16) = 80
+    uint16_t const tss_selector =
+        (global_descriptor_table.size() - 1) * sizeof(segment_descriptor_table::segment_descriptor);
+    kernel::cpu::load_task_register(tss_selector);
+
+    auto const stored_task_register = kernel::cpu::store_task_register();
+    arch::exception_handling::assert(tss_selector == stored_task_register,
+                                     "[Global Descriptor Table] Loaded TR value is not the same as the stored value.");
+
+    kernel::cpu::set_interrupt_flag();
+
+    descriptor_tables tables = {global_descriptor_table, idt};
+    return tables;
+  }
+}  // namespace teachos::arch::context_switching