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descriptor_tables.c
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#include "descriptor_tables.h"
#include "monitor.h"
#include "pic.h"
#include "system.h"
// Number of GDT entries
#define GDT_COUNT 5
// Number of IDT entries
#define IDT_COUNT 256
extern void gdt_flush(uint32_t);
extern void idt_flush(uint32_t);
static void gdt_set_gate(int32_t, uint32_t, uint32_t, uint8_t, uint8_t);
static void idt_set_gate(uint8_t, uint32_t, uint16_t, uint8_t);
static void pic_remap(void);
gdt_entry_t gdt_entries[GDT_COUNT];
gdt_ptr_t gdt_ptr;
idt_entry_t idt_entries[IDT_COUNT];
idt_ptr_t idt_ptr;
void gdt_init(void)
{
monitor_write("Initialising GDT... ");
gdt_ptr.limit = (sizeof(gdt_entry_t) * GDT_COUNT) - 1;
gdt_ptr.base = (uint32_t)&gdt_entries;
gdt_set_gate(0, 0, 0, 0, 0); // null segment
gdt_set_gate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF); // code segment
gdt_set_gate(2, 0, 0xFFFFFFFF, 0x92, 0xCF); // data segment
gdt_set_gate(3, 0, 0xFFFFFFFF, 0xFA, 0xCF); // user mode code segment
gdt_set_gate(4, 0, 0xFFFFFFFF, 0xF2, 0xCF); // user mode data segment
gdt_flush((uint32_t)&gdt_ptr);
monitor_color_set(MONCOLOR_GREEN, MONCOLOR_BLACK);
monitor_writeline("OK");
monitor_color_reset();
}
void idt_init(void)
{
monitor_write("Initialising IDT... ");
idt_ptr.limit = (sizeof(idt_entry_t) * IDT_COUNT) - 1;
idt_ptr.base = (uint32_t)&idt_entries;
memset((byte_t *)&idt_entries, 0, sizeof(idt_entry_t)*IDT_COUNT);
idt_set_gate( 0, (uint32_t)isr0 , 0x08, 0x8E);
idt_set_gate( 1, (uint32_t)isr1 , 0x08, 0x8E);
idt_set_gate( 2, (uint32_t)isr2 , 0x08, 0x8E);
idt_set_gate( 3, (uint32_t)isr3 , 0x08, 0x8E);
idt_set_gate( 4, (uint32_t)isr4 , 0x08, 0x8E);
idt_set_gate( 5, (uint32_t)isr5 , 0x08, 0x8E);
idt_set_gate( 6, (uint32_t)isr6 , 0x08, 0x8E);
idt_set_gate( 7, (uint32_t)isr7 , 0x08, 0x8E);
idt_set_gate( 8, (uint32_t)isr8 , 0x08, 0x8E);
idt_set_gate( 9, (uint32_t)isr9 , 0x08, 0x8E);
idt_set_gate(10, (uint32_t)isr10, 0x08, 0x8E);
idt_set_gate(11, (uint32_t)isr11, 0x08, 0x8E);
idt_set_gate(12, (uint32_t)isr12, 0x08, 0x8E);
idt_set_gate(13, (uint32_t)isr13, 0x08, 0x8E);
idt_set_gate(14, (uint32_t)isr14, 0x08, 0x8E);
idt_set_gate(15, (uint32_t)isr15, 0x08, 0x8E);
idt_set_gate(16, (uint32_t)isr16, 0x08, 0x8E);
idt_set_gate(17, (uint32_t)isr17, 0x08, 0x8E);
idt_set_gate(18, (uint32_t)isr18, 0x08, 0x8E);
idt_set_gate(19, (uint32_t)isr19, 0x08, 0x8E);
idt_set_gate(20, (uint32_t)isr20, 0x08, 0x8E);
idt_set_gate(21, (uint32_t)isr21, 0x08, 0x8E);
idt_set_gate(22, (uint32_t)isr22, 0x08, 0x8E);
idt_set_gate(23, (uint32_t)isr23, 0x08, 0x8E);
idt_set_gate(24, (uint32_t)isr24, 0x08, 0x8E);
idt_set_gate(25, (uint32_t)isr25, 0x08, 0x8E);
idt_set_gate(26, (uint32_t)isr26, 0x08, 0x8E);
idt_set_gate(27, (uint32_t)isr27, 0x08, 0x8E);
idt_set_gate(28, (uint32_t)isr28, 0x08, 0x8E);
idt_set_gate(29, (uint32_t)isr29, 0x08, 0x8E);
idt_set_gate(30, (uint32_t)isr30, 0x08, 0x8E);
idt_set_gate(31, (uint32_t)isr31, 0x08, 0x8E);
pic_remap();
idt_set_gate(32, (uint32_t)irq0 , 0x08, 0x8E);
idt_set_gate(33, (uint32_t)irq1 , 0x08, 0x8E);
idt_set_gate(34, (uint32_t)irq2 , 0x08, 0x8E);
idt_set_gate(35, (uint32_t)irq3 , 0x08, 0x8E);
idt_set_gate(36, (uint32_t)irq4 , 0x08, 0x8E);
idt_set_gate(37, (uint32_t)irq5 , 0x08, 0x8E);
idt_set_gate(38, (uint32_t)irq6 , 0x08, 0x8E);
idt_set_gate(39, (uint32_t)irq7 , 0x08, 0x8E);
idt_set_gate(40, (uint32_t)irq8 , 0x08, 0x8E);
idt_set_gate(41, (uint32_t)irq9 , 0x08, 0x8E);
idt_set_gate(42, (uint32_t)irq10, 0x08, 0x8E);
idt_set_gate(43, (uint32_t)irq11, 0x08, 0x8E);
idt_set_gate(44, (uint32_t)irq12, 0x08, 0x8E);
idt_set_gate(45, (uint32_t)irq13, 0x08, 0x8E);
idt_set_gate(46, (uint32_t)irq14, 0x08, 0x8E);
idt_set_gate(47, (uint32_t)irq15, 0x08, 0x8E);
idt_flush((uint32_t)&idt_ptr);
monitor_color_set(MONCOLOR_GREEN, MONCOLOR_BLACK);
monitor_writeline("OK");
monitor_color_reset();
}
static void gdt_set_gate(int32_t number, uint32_t base, uint32_t limit, uint8_t access, uint8_t granularity)
{
gdt_entries[number].base_low = (base & 0xFFFF);
gdt_entries[number].base_middle = (base >> 16) & 0xFF;
gdt_entries[number].base_high = (base >> 24) & 0xFF;
gdt_entries[number].limit_low = (limit & 0xFFFF);
gdt_entries[number].granularity = (limit >> 16) & 0x0F;
gdt_entries[number].granularity |= granularity & 0xF0;
gdt_entries[number].access = access;
}
static void idt_set_gate(uint8_t number, uint32_t base, uint16_t selector, uint8_t flags)
{
idt_entries[number].base_low = base & 0xFFFF;
idt_entries[number].base_high = (base >> 16) & 0xFFFF;
idt_entries[number].selector = selector;
idt_entries[number].zero = 0;
// TODO: set interrupt gate to ring 3
idt_entries[number].flags = flags /* | 0x60 */;
}
static void pic_remap(void)
{
// Restart both PICs
outb(PIC1_CMD, 0x11);
outb(PIC2_CMD, 0x11);
// Start PIC1 at 32
outb(PIC1_DATA, 0x20);
// Start PIC2 at 40
outb(PIC2_DATA, 0x28);
// Set up cascading
outb(PIC1_DATA, 0x04);
outb(PIC2_DATA, 0x02);
// Finish
outb(PIC1_DATA, 0x01);
outb(PIC2_DATA, 0x01);
outb(PIC1_DATA, 0x0);
outb(PIC2_DATA, 0x0);
}