idt.c

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/*
WKern - A Bare Metal OS / Kernel I am maKing (For Fun)
Copyright (C) 2025  Wdboyes13
 
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/
 
#include <global.h>
#include <idt/idtirq.h>
#include <io/kio.h>
#include <mem/kmem.h>
#include <types/nums.h>
#include <utils/util.h>

struct IdtEntry idt[IDT_ENTRIES];

struct IdtPtr idt_ptrn __attribute__((aligned(16)));

void IdtSetGate(u8 num, u32 base, u16 sel, u8 flags) {
    idt[num].base_lo = base & 0xFFFF;
    idt[num].sel = sel;
    idt[num].always0 = 0;
    idt[num].flags = flags;
    idt[num].base_hi = (base >> 16) & 0xFFFF;
}

extern void IdtLoad(void);

void debug_print_idt_entry(int i) {
    u32 base = (idt[i].base_hi << 16) | idt[i].base_lo;
    char buf[25];
    Kitoa(i, buf);
    Kprintf("IDT[%s] = %x\n", buf, base);
}

void AllIdt() {
 
    GdtInstall(); 
 
    Kprintf("Calling PIC Remap\n");
    _picr(); 
 
    MaskAllIrqs(); 
 
    UnmaskIrq(1); 
    UnmaskIrq(0); 
 
    Kprintf("Setting IDT to 0x00\n");
    Kmemset(&idt, 0,
            sizeof(struct IdtEntry) *
                IDT_ENTRIES); 
 
    Kprintf("Setting IDT Limit + Base\n");
    idt_ptrn.limit =
        (sizeof(struct IdtEntry) * IDT_ENTRIES) - 1; 
    idt_ptrn.base = (uptr)idt; 
 
    Kprintf("Setting up IDT gate 32 (IRQ0)\n");
    IdtSetGate(32, (uptr)Irq0Handler, KERNEL_CODE_SEGMENT,
               0x8E); 
    debug_print_idt_entry(32);
 
    Kprintf("Setting up IDT gate 33 (IRQ1)\n");
    IdtSetGate(33, (uptr)Irq1Handler, KERNEL_CODE_SEGMENT,
               0x8E); 
    debug_print_idt_entry(33);
 
    Kprintf("Disabling interrupts\n");
    __asm__ volatile("cli"); 
 
    struct {
        u16 limit;
        u32 base;
    } PKG gdtr;
 
    __asm__ volatile("sgdt %0" : "=m"(gdtr)); 
 
    Kprintf("GDT base = %x, limit = %x\n", gdtr.base, gdtr.limit);
    Kprintf("IDT base = %x, limit = %x\n", idt_ptrn.base, idt_ptrn.limit);
 
    Kprintf("Loading IDT\n");
    __asm__ volatile("lidt %[idt]" ::[idt] "m"(idt_ptrn)
                     : "memory"); 
 
    Kprintf("Enabling interrupts");
    __asm__ volatile("sti"); 
 
    PitInit(
        PIT_FREQ); 
}