From 975a9ec96e282e437ccc1bdf1e660dcbf4542791 Mon Sep 17 00:00:00 2001
From: EmulatedSeasons <89668582+EmulatedSeasons@users.noreply.github.com>
Date: Fri, 10 May 2024 01:44:59 -0400
Subject: Added GDT and basic IDT as well as a bitmap drawing function

---
 kernel/arch/x86_64/gdt.cpp | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 kernel/arch/x86_64/gdt.cpp

(limited to 'kernel/arch/x86_64/gdt.cpp')

diff --git a/kernel/arch/x86_64/gdt.cpp b/kernel/arch/x86_64/gdt.cpp
new file mode 100644
index 0000000..19ec98e
--- /dev/null
+++ b/kernel/arch/x86_64/gdt.cpp
@@ -0,0 +1,34 @@
+#include <stdint.h>
+#include "gdt.h"
+
+void gdt_entry(SegDesc* seg, uint32_t base, uint32_t limit, uint8_t access, uint8_t flags) {
+    // setting each part of the base by masking the part being set and shifting it to the right position
+    seg->base_low = base & 0xFFFF; 
+    seg->base_mid = (base & 0xFF0000) >> 16;
+    seg->base_high = (base & 0xFF000000) >> 24;
+
+    seg->limit_low = limit & 0xFFFF;
+    seg->flag_limit_high = (limit & 0xF0000) >> 16;
+
+    // shifts flags to the right position and ors it with limit
+    seg->flag_limit_high |= (flags & 0xF) << 4;
+
+    seg->access = access;
+}
+
+void gdt_tss_entry(TssSegDesc* seg, uint64_t base, uint32_t limit, uint8_t access, uint8_t flags) {
+    // setting each part of the base by masking the part being set and shifting it to the right position
+    seg->base1 = base & 0xFFFF; 
+    seg->base2 = (base & 0xFF0000) >> 16;
+    seg->base3 = (base & 0xFF000000) >> 24;
+    seg->base4 = (base & 0xFFFFFFFF00000000) >> 32;
+
+    seg->limit_low = limit & 0xFFFF;
+    seg->flag_limit_high = (limit & 0xF0000) >> 16;
+
+    // shifts flags to the right position and ors it with limit
+    seg->flag_limit_high |= (flags & 0xF) << 4;
+
+    seg->access = access;
+    seg->reserved = 0;
+}
\ No newline at end of file
-- 
cgit v1.2.3-70-g09d2