Initial download from archive

http://web.archive.org/web/20210423124630/https://github.com/jdah/tetris-os/blob/master/README.md

src/idt.c

@@ -0,0 +1,39 @@
+#include "idt.h"
+
+struct IDTEntry {
+    u16 offset_low;
+    u16 selector;
+    u8 __ignored;
+    u8 type;
+    u16 offset_high;
+} PACKED;
+
+struct IDTPointer {
+    u16 limit;
+    uintptr_t base;
+} PACKED;
+
+static struct {
+    struct IDTEntry entries[256];
+    struct IDTPointer pointer;
+} idt;
+
+// in start.S
+extern void idt_load();
+
+void idt_set(u8 index, void (*base)(struct Registers*), u16 selector, u8 flags) {
+    idt.entries[index] = (struct IDTEntry) {
+        .offset_low = ((uintptr_t) base) & 0xFFFF,
+        .offset_high = (((uintptr_t) base) >> 16) & 0xFFFF,
+        .selector = selector,
+        .type = flags | 0x60,
+        .__ignored = 0
+    };
+}
+
+void idt_init() {
+    idt.pointer.limit = sizeof(idt.entries) - 1;
+    idt.pointer.base = (uintptr_t) &idt.entries[0];
+    memset(&idt.entries[0], 0, sizeof(idt.entries));
+    idt_load((uintptr_t) &idt.pointer);
+}