idt

makefile

@@ -1,7 +1,7 @@
 CC = x86_64-elf-gcc
 LD = x86_64-elf-ld
 
-CFLAGS = -m64 -ffreestanding -fno-builtin -Wall -Wextra -Wshadow -std=c23
+CFLAGS = -m64 -ffreestanding -fno-builtin -Wall -Wextra -Werror -Wshadow -std=c23
 LDFLAGS = 
 
 all: .build/nub-os.iso

src/boot.asm

@@ -31,6 +31,7 @@ section .text
 bits 32
 global _start
 _start:
+    cli
     mov esp, stack_top
 
     ; Check if CPU supports 64-bit mode

src/idt.asm

@@ -1,16 +1,21 @@
+extern interrput_handler
+
 %macro isr_err_stub 1
 isr_stub_%+%1:
-    call exception_handler
+    push %1
+    call interrput_handler
+    add rsp, 8
     iretq
 %endmacro
 
 %macro isr_no_err_stub 1
 isr_stub_%+%1:
-    call exception_handler
+    push %1
+    call interrput_handler
+    add rsp, 8
     iretq
 %endmacro
 
-extern exception_handler
 isr_no_err_stub 0
 isr_no_err_stub 1
 isr_no_err_stub 2
@@ -51,3 +56,11 @@ isr_stub_table:
     dq isr_stub_%+i
 %assign i i + 1 
 %endrep
+
+.text
+global idt_hang
+idt_hang:
+    cli
+.loop:
+    hlt
+    jmp .loop

src/idt.c

@@ -1,19 +1,19 @@
+#include "idt.h"
 #include "vga.h"
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 
-#define IDT_MAX_DESCRIPTORS 255
-
 typedef struct
 {
-    uint16_t isr_low;   // The lower 16 bits of the ISR's address
+    uint16_t address_low;
-    uint16_t kernel_cs; // The GDT segment selector that the CPU will load into CS before calling the ISR
+    uint16_t selector;
-    uint8_t ist;        // The IST in the TSS that the CPU will load into RSP; set to zero for now
+    uint8_t ist;
-    uint8_t attributes; // Type and attributes; see the IDT page
+    uint8_t flags;
-    uint16_t isr_mid;   // The higher 16 bits of the lower 32 bits of the ISR's address
+    uint16_t address_mid;
-    uint32_t isr_high;  // The higher 32 bits of the ISR's address
+    uint32_t address_high;
-    uint32_t reserved;  // Set to zero
+    uint32_t reserved;
-} __attribute__((packed)) idt_entry_t;
+} __attribute__((packed)) interrupt_descriptor;
 
 typedef struct
 {
@@ -21,45 +21,48 @@ typedef struct
     uint64_t base;
 } __attribute__((packed)) idtr_t;
 
-static idt_entry_t idt[256];
+static interrupt_descriptor idt[256];
 static idtr_t idtr;
-
-void exception_handler(void)
-{
-    vga_print_error("An unhandled exception occurred");
-    __asm__ volatile("cli; hlt");
-}
-
-void idt_set_descriptor(uint8_t vector, void* isr, uint8_t flags)
-{
-    idt_entry_t* descriptor = &idt[vector];
-
-    descriptor->isr_low = (uint64_t)isr & 0xFFFF;
-    descriptor->kernel_cs = 0x08;
-    descriptor->ist = 0;
-    descriptor->attributes = flags;
-    descriptor->isr_mid = ((uint64_t)isr >> 16) & 0xFFFF;
-    descriptor->isr_high = ((uint64_t)isr >> 32) & 0xFFFFFFFF;
-    descriptor->reserved = 0;
-}
-
-static bool vectors[IDT_MAX_DESCRIPTORS];
-
 extern void* isr_stub_table[];
+extern void idt_hang();
+
+void idt_set_descriptor(uint8_t vector, void* handler, uint8_t dpl)
+{
+    interrupt_descriptor* entry = &idt[vector];
+
+    entry->address_low = (uint64_t)handler & 0xFFFF;
+    entry->address_mid = ((uint64_t)handler >> 16) & 0xFFFF;
+    entry->address_high = (uint64_t)handler >> 32;
+    entry->selector = 0x08;
+    entry->flags = 0b1110 | ((dpl & 0b11) << 5) | (1 << 7);
+    entry->ist = 0;
+    entry->reserved = 0;
+}
 
 void idt_init(void)
 {
     idtr.base = (uintptr_t)&idt[0];
-    idtr.limit = (uint16_t)sizeof(idt_entry_t) * IDT_MAX_DESCRIPTORS - 1;
+    idtr.limit = (uint16_t)sizeof(interrupt_descriptor) * 256 - 1;
 
     for (uint8_t vector = 0; vector < 32; vector++)
     {
-        idt_set_descriptor(vector, isr_stub_table[vector], 0x8E);
+        idt_set_descriptor(vector, isr_stub_table[vector], 0);
-        vectors[vector] = true;
     }
 
     __asm__ volatile("lidt %0" : : "m"(idtr));
     __asm__ volatile("sti");
-
+}
-    vga_print_success("IDT intialzied");
+
+typedef struct
+{
+    uint64_t vector_number;
+    uint64_t error_code;
+} cpu_status_t;
+
+void interrput_handler(uint64_t vector_number)
+{
+    vga_print("An exception occurred: ");
+    vga_print_uint(vector_number);
+    vga_print("\n");
+    idt_hang();
 }

src/idt.h

@@ -1,5 +1,6 @@
+#pragma once
+
 #include <stdint.h>
 
 void idt_init(void);
-void exception_handler(void);
 void idt_set_descriptor(uint8_t vector, void* isr, uint8_t flags);

src/kernel.c

@@ -6,8 +6,7 @@ void kernel_main(void)
     vga_clear();
 
     idt_init();
+    vga_print_success("IDT intialzied\n");
 
     vga_print("Welcome to nub OS\n");
-
-    int x = 1 / 0;
 }

src/vga.c

@@ -116,7 +116,6 @@ void vga_print_success(const char* message)
     vga_print_colored("success", VGA_GREEN);
     vga_print(" ] ");
     vga_print(message);
-    vga_print("\n");
 }
 
 void vga_print_error(const char* message)
@@ -125,5 +124,64 @@ void vga_print_error(const char* message)
     vga_print_colored("error", VGA_RED);
     vga_print(" ] ");
     vga_print(message);
-    vga_print("\n");
+}
+
+static void reverse(char* str, int length)
+{
+    int start = 0;
+    int end = length - 1;
+    while (start < end)
+    {
+        char temp = str[start];
+        str[start] = str[end];
+        str[end] = temp;
+        start++;
+        end--;
+    }
+}
+
+static int uitoa(unsigned int value, char* buffer)
+{
+    int i = 0;
+    if (value == 0)
+    {
+        buffer[i++] = '0';
+        buffer[i] = '\0';
+        return i;
+    }
+
+    while (value > 0)
+    {
+        buffer[i++] = (value % 10) + '0';
+        value /= 10;
+    }
+
+    buffer[i] = '\0';
+    reverse(buffer, i);
+    return i;
+}
+
+void vga_print_uint(unsigned int value)
+{
+    char buffer[11];
+    uitoa(value, buffer);
+    vga_print(buffer);
+}
+
+void vga_print_int(int value)
+{
+    char buffer[12];
+
+    if (value < 0)
+    {
+        vga_print("-");
+        unsigned int abs_val = (unsigned int)(-value);
+        uitoa(abs_val, buffer);
+    }
+    else
+    {
+        uitoa((unsigned int)value, buffer);
+    }
+
+    vga_print(buffer);
 }

src/vga.h

@@ -26,9 +26,13 @@ void vga_set_cursor_position(uint8_t row, uint8_t col);
 
 void vga_print_colored(const char* string, vga_color_t color);
 void vga_print(const char* string);
+
 void vga_print_success(const char* message);
 void vga_print_error(const char* message);
 
+void vga_print_uint(unsigned int value);
+void vga_print_int(int value);
+
 static inline vga_color_t vga_color(vga_color_t fg_color, vga_color_t bg_color)
 {
     return fg_color | bg_color << 4;