src/kernel/interrupts/idt.c


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#include <kernel/lib/lib.h>
#include <kernel/system.h>

struct idt_entry {
    uint16_t base_low;
    uint16_t sel; // Kernel segment
    uint8_t always0; // Always 0
    uint8_t flags;
    uint16_t base_high;
} __attribute__((packed));

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

// Initialize IDT with 256 entries
struct idt_entry idt[256];
struct idt_ptr idtp;

// Defined in idt.asm
extern void idt_load();

void idt_set_gate(unsigned char num, unsigned long base, unsigned short sel, unsigned char flags)
{
    // Specify the interrupt routine's base address
    idt[num].base_low = (uint16_t) (base & 0xFFFF);
    idt[num].base_high = (uint16_t) ((base >> 16) & 0xFFFF);

    // Set selector/segment of IDT entry
    idt[num].sel = sel;
    idt[num].always0 = 0;
    idt[num].flags = (uint8_t) (flags | 0x60);
}

// Install IDT
void idt_install()
{
    // Set IDT pointer and limit
    idtp.limit = (sizeof(struct idt_entry) * 256) - 1;
    idtp.base = &idt;

    // Clear IDT by setting memory cells to 0
    memset(&idt, 0, sizeof(struct idt_entry) * 256);

    idt_load();
    vga_log("Installed Interrupt Descriptor Table");
}