software interrupt

include/mem.h

@@ -2,5 +2,6 @@
 #define KARLOS_MEM_H
 
 void init_gdt();
+void init_idt();
 
 #endif

src/kernel.c

@@ -95,10 +95,13 @@ void _start()
 
     // memory stuff
     init_gdt();
+    init_idt();
 
-    println("Test after init_gdt");
+    println("Test after init");
 
-    check_initrd();
+    __asm__("int $0x80" :: );
+
+    // check_initrd();
 
     // hang for now
     panic("end of kernel");

src/x86_64/mem.c

@@ -1,4 +1,5 @@
 #include <stdint.h>
+#include "output.h" // remove later, this is only for interrupt handler
 
 uint64_t gdt[3];
 
@@ -49,3 +50,57 @@ void init_gdt() {
 	__asm__ ("mov %0, %%ds" :: "r"(DATA_SEGMENT << 3));
 	// TODO set code segment -> iret?
 }
+
+__attribute__ ((packed))
+struct int_desc_entry {
+    uint16_t offset1;
+    uint16_t selector;
+    uint8_t ist;
+    uint8_t attr;
+    uint16_t offset2;
+    uint32_t offset3;
+    uint32_t pad;
+};
+
+#define PRIV_KERNEL 0
+#define PRIV_USER 3
+
+void write_segment_selector(uint16_t *ss, uint16_t index) {
+    *ss = (uint16_t)PRIV_KERNEL
+        | 0 // use GDT
+        | (index << 3)
+    ;
+}
+
+#define GATE_TYPE_INTERRUPT 0xe
+
+void write_int_desc_entry(struct int_desc_entry *e, uint64_t offset) {
+    e->offset1 = (uint16_t) (offset & 0xffff);
+    write_segment_selector(&e->selector, CODE_SEGMENT);
+    e->ist = 0;
+    e->attr = (uint8_t)GATE_TYPE_INTERRUPT
+            | (uint8_t)(PRIV_KERNEL << 5)
+            | (uint8_t)(1 << 7) // present
+    ;
+    e->offset2 = (uint16_t) ((offset >> 16) & 0xffff);
+    e->offset3 = (uint32_t) ((offset >> 32) & 0xffffffff);
+    e->pad = 0;
+}
+
+void basic_interrupt_handler(void) {
+    panic("Hello Interrupt!\n");
+}
+
+#define NUM_INTERRUPTS 256
+struct int_desc_entry idt[NUM_INTERRUPTS];
+
+void init_idt() {
+    write_int_desc_entry(&idt[0x80], (uint64_t)(intptr_t)basic_interrupt_handler);
+
+    uint8_t idtr[10];
+
+    *(uint16_t*)idtr = sizeof(idt) - 1;
+    *(uint64_t**)(idtr + 2) = (uint64_t*)idt;
+
+    __asm__ ("lidt (%0)" :: "r"(idtr));
+}