rk/kmain.c

#include "ide.h"
#include <multiboot.h>
#include <acpi.h>
#include <vga.h>
#include <pci.h>
#include <printf.h>
#include <strcmp.h>
#include <gdt.h>
#include <idt.h>
#include <pic8259.h>
#include <ps2.h>

struct kernel_context {
    struct rsdp *rsdp;
    struct xsdp *xsdp;

    struct rsdt *rsdt;
};

struct kernel_context ctx = {0};

struct idt_entry g_idt[256] = {0};
struct idtr g_idtr = {0};

extern void exception_handler();
extern void ps2_isr();

#define MAGIC_BREAKPOINT __asm__ volatile("xchgw %bx, %bx");

void kmain(struct multiboot_info *info) {
    clear_screen();
    set_color(VGA_COLOR_CYAN);
// Check if the bootloader gave us the upper and lower memory
    if (!(info->flags & 0x1)) goto halt;

// Create and load an IDT
    for (int i = 0; i < 32; i++) {
        encode_idt_entry(g_idt, i, (uint32_t)&exception_handler, GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, 0x00), TRAP_GATE_32 | INT_RING0 | INT_PRESENT);
    }

    g_idtr.size = (sizeof(struct idt_entry) * 256) - 1;
    g_idtr.base = (uint32_t) &g_idt;

    asm volatile ("lidt %0" :: "m"(g_idtr));

    struct rsdp *found_rsdp = acpi_locate_rsdp();
    if (!found_rsdp) {
        set_color(VGA_COLOR_RED);
        printf("Failed to find RSDP signature\n");
        goto halt;
    }

    if (found_rsdp->Revision == ACPI_VER_1) {
        if (!acpi_validate_rsdp_checksum(found_rsdp)) {
            set_color(VGA_COLOR_RED);
            printf("RSDP has an invalid checksum\n");
            goto halt;
        }
        ctx.rsdp = found_rsdp;
        ctx.xsdp = 0;

        if (!acpi_validate_sdt_checksum((struct ACPISDTHeader *)found_rsdp->RsdtAddress)) {
            set_color(VGA_COLOR_RED);
            printf("RSDT has an invalid checksum\n");
            goto halt;
        }

        ctx.rsdt = (struct rsdt*)found_rsdp->RsdtAddress;

    } else if (found_rsdp->Revision == ACPI_VER_OTHER) {
        set_color(VGA_COLOR_RED);
        printf("ACPI versions higher than 1.0 are not yet supported because I'm lazy\n");
        goto halt;
    } else {
        set_color(VGA_COLOR_RED);
        printf("Invalid RSDP\n");
        goto halt;
    }

    printf("Using ACPI v1.0\n");

    struct fadt *fadt = acpi_locate_sdt(ctx.rsdt, "FACP");
    if (!fadt) {
        set_color(VGA_COLOR_RED);
        printf("Failed to find FADT\n");
        goto halt;
    }
    printf("Found FADT at 0x%x\n", fadt);
    if (fadt->Flags & 1)
        printf("Legacy devices are supported\n");
    else {
        /*
        set_color(VGA_COLOR_RED);
        printf("Legacy devices are not supported. I'm too lazy to support modern devices, bye bye.\n");
        goto halt;
        */
    }
    pic_remap(PIC_1_START, PIC_2_START);
// ACPI version 1.0 is so old that we assume that our PC supports the 8042 ps/2 controller 
    initialize_8042ps2();
    encode_idt_entry(g_idt, 0x21, (uint32_t)&ps2_isr, GDT_SEGMENT_SELECTOR(GDT_KERNEL_CODE, 0x00), INT_GATE_32 | INT_RING0 | INT_PRESENT);
    asm volatile ("sti" ::);

    struct mcfg *mcfg = acpi_locate_sdt(ctx.rsdt, "MCFG");
    if (!mcfg) {
        set_color(VGA_COLOR_RED);
        printf("Failed to find MCFG\n");
    } else {

        printf("Looks like you are using PCIe- Found MCFG at 0x%x\n", mcfg);

        struct pci_config_space *ide = pcie_find_device(mcfg, MASS_STORAGE_CONTROLLER, IDE_INTERFACE);
        if (ide) { 
            printf("IDE controller detected. Program Interface: %X\n", ide->program_interface);

            uint16_t ide_buf[256] = {0};
            ide_identify(ATA_PRIMARY, ATA_MASTER, ide_buf);
        }
    }

    set_color(VGA_COLOR_WHITE);
    printf("\nYou are now being dropped into a kernel shell\n$ ");
halt:
    for (;;) {}
}