i386: create idt.c and isr.s

Create files that add IDT support for i386.

Signed-off-by: Danny Holman <dholman@gymli.xyz>

1 files changed, 50 insertions, 0 deletions

diff --git a/arch/i386/boot/idt.c b/arch/i386/boot/idt.c
new file mode 100644
index 0000000..752b679
--- /dev/null
+++ b/arch/i386/boot/idt.c
@@ -0,0 +1,50 @@
+#include <kernel/io.h>
+#include <stdint.h>
+
+struct idt_entry {
+        uint16_t        isr_low;
+        uint16_t        kernel_cs;
+        uint8_t         reserved;
+        uint8_t         attributes;
+        uint16_t        isr_high;
+} __attribute__((packed));
+
+struct idt_ptr {
+        uint16_t        limit;
+        uint32_t        base;
+} __attribute__((packed));
+
+__attribute__((aligned(0x10)))
+static struct idt_entry idt[256];
+static struct idt_ptr idtr;
+
+__attribute__((noreturn))
+void exception_handler(int in) {
+        kprintf("EXCEPTION %d CAUGHT\n", in);
+}
+
+extern void* isr_stub_table[];
+
+void idt_set_descriptor(uint8_t vector, void *isr, uint8_t flags) {
+        struct idt_entry *desc = &idt[vector];
+
+        desc->isr_low           = (uint32_t)isr & 0xFFFF;
+        desc->kernel_cs         = 0x08;
+        desc->attributes        = flags;
+        desc->isr_high          = (uint32_t)isr >> 16;
+        desc->reserved          = 0;
+}
+
+void idt_install(void) {
+        idtr.base = (uintptr_t)&idt[0];
+        idtr.limit = (uint16_t)sizeof(struct idt_entry) * 256 - 1;
+
+        for (uint8_t vector = 0; vector < 32; vector++) {
+                idt_set_descriptor(vector, isr_stub_table[vector], 0x8E);
+                isr_stub_table[vector] = 1;
+        }
+
+        __asm__ volatile("lidt %0" : : "memory"(idtr));
+        __asm__ volatile("sti");
+        kprintf("Interrupts on\n");
+}