Syncboot/kernel/idt.c

#include <kernel/utils.h>
#include <kernel/descriptor_tables.h>

struct idt_entry {
	unsigned short base_low;
	unsigned short selector;
	unsigned char always0;
	unsigned char flags;
	unsigned short base_high;
} __attribute__((packed));

struct idt_ptr {
	unsigned short limit;
	unsigned int base;
} __attribute__((packed));

struct idt_entry idt[256]; // Interrupt table of 256 entries
struct idt_ptr idtp; // Pointer to idt table

extern void idt_load();

void idt_set_gate(unsigned char num, unsigned long base, unsigned short sel, unsigned char flags) {
	idt[num].base_low = base & 0xFFFF;
	idt[num].base_high = (base >> 16) & 0xFFFF;
	
	idt[num].selector = sel;
	idt[num].always0 = 0;
	
	// Must be uncommented when we get to usermode - it sets the permission
	// level to 3
	idt[num].flags = flags; // | 0x60;
}

void idt_install() {
	idtp.limit = (sizeof (struct idt_entry) * 256) - 1;
	idtp.base = (uint16_t) &idt;
	
	memset(&idt, 0, sizeof(struct idt_entry) * 256);
	
	idt_set_gate(0, (unsigned)isr0, 0x08, 0x8E);
    idt_set_gate(1, (unsigned)isr1, 0x08, 0x8E);
    idt_set_gate(2, (unsigned)isr2, 0x08, 0x8E);
    idt_set_gate(3, (unsigned)isr3, 0x08, 0x8E);
    idt_set_gate(4, (unsigned)isr4, 0x08, 0x8E);
    idt_set_gate(5, (unsigned)isr5, 0x08, 0x8E);
    idt_set_gate(6, (unsigned)isr6, 0x08, 0x8E);
    idt_set_gate(7, (unsigned)isr7, 0x08, 0x8E);

    idt_set_gate(8, (unsigned)isr8, 0x08, 0x8E);
    idt_set_gate(9, (unsigned)isr9, 0x08, 0x8E);
    idt_set_gate(10, (unsigned)isr10, 0x08, 0x8E);
    idt_set_gate(11, (unsigned)isr11, 0x08, 0x8E);
    idt_set_gate(12, (unsigned)isr12, 0x08, 0x8E);
    idt_set_gate(13, (unsigned)isr13, 0x08, 0x8E);
    idt_set_gate(14, (unsigned)isr14, 0x08, 0x8E);
    idt_set_gate(15, (unsigned)isr15, 0x08, 0x8E);

    idt_set_gate(16, (unsigned)isr16, 0x08, 0x8E);
    idt_set_gate(17, (unsigned)isr17, 0x08, 0x8E);
    idt_set_gate(18, (unsigned)isr18, 0x08, 0x8E);
    idt_set_gate(19, (unsigned)isr19, 0x08, 0x8E);
    idt_set_gate(20, (unsigned)isr20, 0x08, 0x8E);
    idt_set_gate(21, (unsigned)isr21, 0x08, 0x8E);
    idt_set_gate(22, (unsigned)isr22, 0x08, 0x8E);
    idt_set_gate(23, (unsigned)isr23, 0x08, 0x8E);

    idt_set_gate(24, (unsigned)isr24, 0x08, 0x8E);
    idt_set_gate(25, (unsigned)isr25, 0x08, 0x8E);
    idt_set_gate(26, (unsigned)isr26, 0x08, 0x8E);
    idt_set_gate(27, (unsigned)isr27, 0x08, 0x8E);
    idt_set_gate(28, (unsigned)isr28, 0x08, 0x8E);
    idt_set_gate(29, (unsigned)isr29, 0x08, 0x8E);
    idt_set_gate(30, (unsigned)isr30, 0x08, 0x8E);
    idt_set_gate(31, (unsigned)isr31, 0x08, 0x8E);
	
	idt_load();
	irq_install();
	
}

void irq_install_handler(int irq, void (*handler)(registers_t* r)) {
	irq_routines[irq] = handler;
}

void irq_uninstall_handler(int irq) {
	irq_routines[irq] = 0;
}

void irq_remap() {
	outb(0x20, 0x11);
	outb(0xA0, 0x11);
	outb(0x21, 0x20);
	outb(0xA1, 0x28);
	outb(0x21, 0x04);
	outb(0xA1, 0x02);
	outb(0x21, 0x01);
	outb(0xA1, 0x01);
	outb(0x21, 0x0);
	outb(0xA1, 0x0);
}

void irq_install() {
	irq_remap();
	idt_set_gate(32, (unsigned)irq0, 0x08, 0x8E);
	idt_set_gate(33, (unsigned)irq1, 0x08, 0x8E);
	idt_set_gate(34, (unsigned)irq2, 0x08, 0x8E);
	idt_set_gate(35, (unsigned)irq3, 0x08, 0x8E);
	idt_set_gate(36, (unsigned)irq4, 0x08, 0x8E);
	idt_set_gate(37, (unsigned)irq5, 0x08, 0x8E);
	idt_set_gate(38, (unsigned)irq6, 0x08, 0x8E);
	idt_set_gate(39, (unsigned)irq7, 0x08, 0x8E);
	idt_set_gate(40, (unsigned)irq8, 0x08, 0x8E);
	idt_set_gate(41, (unsigned)irq9, 0x08, 0x8E);
	idt_set_gate(42, (unsigned)irq10, 0x08, 0x8E);
	idt_set_gate(43, (unsigned)irq11, 0x08, 0x8E);
	idt_set_gate(44, (unsigned)irq12, 0x08, 0x8E);
	idt_set_gate(45, (unsigned)irq13, 0x08, 0x8E);
	idt_set_gate(46, (unsigned)irq14, 0x08, 0x8E);
	idt_set_gate(47, (unsigned)irq15, 0x08, 0x8E);
}

void fault_handler(registers_t *r) {
	if(r->int_no < 32) {
		serial_print(exception_messages[r->int_no], strlen(exception_messages[r->int_no]));
		serial_print(" Exception. Halting.\r\n");
		for(;;);
	}
}

void irq_handler(registers_t *r) {
	void (*handler)(registers_t* r);
	
	serial_print(0x3F8, "[INFO] Received IRQ: " + r->int_no);
	handler = irq_routines[r->int_no - 32];
	if(handler) 
		handler(r);
	
	if(r->int_no > 39)
		outb(0xA0, 0x20);
	
	outb(0x20, 0x20);
}