@@ -3,7 +3,7 @@ Simple x86 operating system written in assembly and C.
 
 ## Software Requirements
 * GNU make
-* Cross-Compiler + binutils: gcc build for freestanding target i386-elf. If a prefix is needed, set the corresponding variable in the makefile.
+* GCC 7 (or higher) Cross Compiler + matching binutils, tailored for freestanding i686-elf-targets
 * Doxygen: If you want to build the documentation
 
 ## Make commands

@@ -0,0 +1,72 @@
+#include "os_interrupts.h"
+#include "os_text.h"
+
+#define HARDWARE_INTERRUPT (0b10001110)
+#define SYSCALL_INTERRUPT (0b11101110)
+
+#define array_sizeof(array) (sizeof(array)/sizeof(array[0]))
+
+#define MAKE_IDT_ENTRY(func, selector, type) { \
+        (uint16_t)(func), \
+        (uint16_t)(selector), \
+        0, \
+        (uint8_t)(type), \
+        (uint16_t)(0xC000) \
+    }
+    
+struct interrupt_frame {
+
+};
+
+__attribute__((interrupt)) void default_isr(struct interrupt_frame *frame) {
+    write("interrupt was issued\n");
+}
+
+__attribute__((interrupt)) void breakpoint_isr(struct interrupt_frame *frame) {
+    write("BREAKPOINT WAS HIT\n");
+    // dump registers to stdout
+}
+
+__attribute__((interrupt)) void double_fault_isr(struct interrupt_frame *frame) {
+    write("CRITICAL: DOUBLE FAULT\n");
+    while (1) {}
+}
+
+IDT_ENTRY IDT[31];
+
+void install_interrupt(int index, void* func, uint16_t selector, uint8_t type) {
+    IDT[index].offset_0 = (uint16_t)((uint32_t)func);
+    IDT[index].selector = selector;
+    IDT[index].__zero = 0;
+    IDT[index].type_attr = type;
+    IDT[index].offset_16 = (uint16_t)((uint32_t)(func) >> 16);
+    //if (index == 7) { while(1) {} }
+}
+
+struct {
+    uint16_t limit;
+    void* offset;
+}__attribute__((packed)) IDT_DESC = {
+    sizeof(IDT),
+    IDT
+};
+
+void init_interrupts(void) {
+    for (uint32_t i = 0; i < array_sizeof(IDT); i++) {
+        switch (i) {
+            case 0x03:
+            install_interrupt(i, breakpoint_isr, 0x08, HARDWARE_INTERRUPT);
+            case 0x08:
+            install_interrupt(i, double_fault_isr, 0x08, HARDWARE_INTERRUPT);
+            break;
+            default:
+            install_interrupt(i, default_isr, 0x08, HARDWARE_INTERRUPT);
+        }
+    }
+
+    __asm__ volatile (
+            "lidt (%0)\n"
+            "sti" : : 
+            "m" (IDT_DESC)
+        );
+}

@@ -1,4 +1,23 @@
 /*! \file
  * Sets up the interrupt descriptor table and provides functions to 
  * hook functions to interrupts.
- */+ */
+#ifndef OS_INTERRUPTS_H
+#define OS_INTERRUPTS_H
+
+ #include <stdint.h>
+
+/*!
+ * Represents a single entry of the IDT.
+ */
+typedef struct {
+    uint16_t offset_0;
+    uint16_t selector;
+    uint8_t __zero;
+    uint8_t type_attr;
+    uint16_t offset_16;
+}__attribute__((packed)) IDT_ENTRY;
+
+void init_interrupts(void);
+
+#endif

@@ -1,6 +1,9 @@
 #include "os_text.h"
+#include "os_interrupts.h"
 
 int main(void) {
+    init_interrupts();
+    
     const char* string[] = { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9" };
     clear();
     for (int i = 0; i < 50; i++) {

@@ -1,5 +1,5 @@
-OUTPUT_FORMAT(binary)
 OUTPUT_ARCH(i386)
+OUTPUT_FORMAT(elf32-i386)
 
 PAGE_SIZE = 1 << 12;
 
@@ -29,12 +29,18 @@
   KERNEL : AT(LOADADDR(SECOND_STAGE) + SIZEOF(SECOND_STAGE))
   {
     */kernel.o(.*)
+    */kernel.o(.bss)
   } >KERNEL
 
   APPLICATION : AT(LOADADDR(KERNEL) + SIZEOF(KERNEL))
   {
+    
+  } >APPLICATION
 
-  } >APPLICATION
+  .bss : AT(LOADADDR(APPLICATION) + SIZEOF(APPLICATION))
+  {
+
+  } >KERNEL
 }
 
 __SS_LMA = LOADADDR(SECOND_STAGE);

@@ -4,14 +4,14 @@ export CURRENT_DIR		= $(shell pwd)
 export INCLUDE_DIR		= $(CURRENT_DIR)/include
 export DEBUG_DIR		= $(CURRENT_DIR)/debug
 
-export GCC_PREFIX		= $(HOME)/opt/cross/i686-elf-/bin/i686-elf-
+export GCC_PREFIX		= $(HOME)/opt/cross/bin/i686-elf-
 
 ifdef DEBUG
 GLOBAL_BUILD		= $(CURRENT_DIR)/build/debug
-GCC_OPTIONS		= -D DEBUG -O0 -Wno-write-strings -Qn -Wall -Wextra -fno-exceptions -nostdlib -nostartfiles -ffreestanding
+GCC_OPTIONS		= -D DEBUG -g -O0 -Wno-write-strings -Qn -Wall -Wextra -fno-exceptions -nostdlib -nostartfiles -ffreestanding -mgeneral-regs-only
 else
 GLOBAL_BUILD		= $(CURRENT_DIR)/build/release
-GCC_OPTIONS		= -O1 -Wno-write-strings -Qn -Wall -Wextra -fno-exceptions -nostdlib -nostartfiles -ffreestanding
+GCC_OPTIONS		= -O1 -Wno-write-strings -Qn -Wall -Wextra -fno-exceptions -nostdlib -nostartfiles -ffreestanding -mgeneral-regs-only
 endif
 
 export GLOBAL_BUILD
@@ -26,8 +26,9 @@ > @mkdir $(GLOBAL_BUILD)/kernel 2> /dev/null; true
 > $(MAKE) LOCAL_BUILD=$(GLOBAL_BUILD)/boot -C boot build
 > $(MAKE) LOCAL_BUILD=$(GLOBAL_BUILD)/second_stage -C second_stage build
 > $(MAKE) LOCAL_BUILD=$(GLOBAL_BUILD)/kernel -C kernel build
-> $(GCC_PREFIX)ld $(wildcard $(GLOBAL_BUILD)/*.o) -T link.txt -Map=$(DEBUG_DIR)/mapfile.txt -o $(GLOBAL_BUILD)/base.img --oformat binary
-> @cp $(GLOBAL_BUILD)/base.img $(CURRENT_DIR)/build 2> /dev/null; true
+> $(GCC_PREFIX)ld $(wildcard $(GLOBAL_BUILD)/*.o) -T link.txt -Map=$(DEBUG_DIR)/mapfile.txt -o build/base.o
+> $(GCC_PREFIX)objcopy --only-keep-debug build/base.o $(DEBUG_DIR)/base.sym
+> $(GCC_PREFIX)objcopy -O binary build/base.o build/base.img
 
 .PHONY: clear
 clear: