Fixing pointer values and adding basic idt value

2 files changed, 22 insertions, 3 deletions

diff --git a/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp b/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp
index 7346248..8bcce65 100644
--- a/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp
+++ b/arch/x86_64/src/context_switching/interrupt_descriptor_table/interrupt_descriptor_table.cpp
@@ -7,7 +7,22 @@ namespace teachos::arch::context_switching::interrupt_descriptor_table
 {
   namespace
   {
-    auto create_interrupt_descriptor_table() -> interrupt_descriptor_table { return interrupt_descriptor_table{}; }
+    auto create_interrupt_descriptor_table() -> interrupt_descriptor_table
+    {
+      // TODO: Fix offset and ist and selector index
+      uint64_t const offset = 0x0;
+      segment_selector const selector{0U, segment_selector::REQUEST_LEVEL_KERNEL};
+      ist_offset const ist{0U};
+      idt_flags const flags{idt_flags::DESCRIPTOR_LEVEL_KERNEL | idt_flags::INTERRUPT_GATE};
+      gate_descriptor const interrupt_gate{selector, ist, flags, offset};
+
+      segment_selector const selector{0U, segment_selector::REQUEST_LEVEL_KERNEL};
+      ist_offset const ist{0U};
+      idt_flags const flags{idt_flags::DESCRIPTOR_LEVEL_KERNEL | idt_flags::TRAP_GATE};
+      gate_descriptor const trap_gate{selector, ist, flags, offset};
+
+      return interrupt_descriptor_table{interrupt_gate, trap_gate};
+    }
   }  // namespace
 
   auto initialize_interrupt_descriptor_table() -> interrupt_descriptor_table &
@@ -15,7 +30,8 @@ namespace teachos::arch::context_switching::interrupt_descriptor_table
     // Interrupt Descriptor Table needs to be kept alive
     static auto idt = create_interrupt_descriptor_table();
 
-    interrupt_descriptor_table_pointer idt_pointer{static_cast<uint16_t>(idt.size() - 1), &idt};
+    interrupt_descriptor_table_pointer idt_pointer{static_cast<uint16_t>((idt.size() * sizeof(gate_descriptor)) - 1),
+                                                   &idt};
     kernel::cpu::load_interrupt_descriptor_table(idt_pointer);
 
     auto const stored_gdt_pointer = kernel::cpu::store_interrupt_descriptor_table();
diff --git a/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp b/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp
index 69cce19..e6a489c 100644
--- a/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp
+++ b/arch/x86_64/src/context_switching/segment_descriptor_table/global_descriptor_table.cpp
@@ -75,7 +75,10 @@ namespace teachos::arch::context_switching::segment_descriptor_table
     // Global Descriptor Table needs to be kept alive
     static auto gdt = create_global_descriptor_table();
 
-    global_descriptor_table_pointer gdt_pointer{static_cast<uint16_t>(gdt.size() - 1), &gdt};
+    // Calculate the size of the gdt in bytes - 1. This subtraction occurs because the maximum value of Size is 65535,
+    // while the GDT can be up to 65536 bytes in length (8192 entries). Further, no GDT can have a size of 0 bytes.
+    global_descriptor_table_pointer gdt_pointer{static_cast<uint16_t>((gdt.size() * sizeof(segment_descriptor)) - 1),
+                                                &gdt};
     kernel::cpu::load_global_descriptor_table(gdt_pointer);
 
     auto const stored_gdt_pointer = kernel::cpu::store_global_descriptor_table();