kernel.c

#include "kernel.h"
#include "gdt.h"
#include "vga.h"
#include "idt.h"
#include "pic.h"
#include "keyboard.h"
#include "memory.h"

/* ── Simple shell ────────────────────────────────────────────────────────────
   Supports: help, clear, mem, echo <text>, malloc <n>
───────────────────────────────────────────────────────────────────────────── */

static int kstrcmp(const char *a, const char *b) {
    while (*a && *a == *b) { a++; b++; }
    return *a - *b;
}

static int kstrncmp(const char *a, const char *b, size_t n) {
    while (n-- && *a && *a == *b) { a++; b++; }
    return n == (size_t)-1 ? 0 : *a - *b;
}

static size_t katoi(const char *s) {
    size_t n = 0;
    while (*s >= '0' && *s <= '9') n = n * 10 + (size_t)(*s++ - '0');
    return n;
}

#define CMD_BUF 128
static char cmd[CMD_BUF];
static int  cmd_len = 0;

static void shell_prompt(void) {
    vga_set_colour(VGA_LIGHT_GREEN, VGA_BLACK);
    vga_puts("\nkernel> ");
    vga_set_colour(VGA_WHITE, VGA_BLACK);
}

static void run_command(void) {
    if (cmd_len == 0) return;

    if (kstrcmp(cmd, "help") == 0) {
        vga_set_colour(VGA_YELLOW, VGA_BLACK);
        vga_puts("\nAvailable commands:\n");
        vga_set_colour(VGA_LIGHT_GREY, VGA_BLACK);
        vga_puts("  help          — show this message\n");
        vga_puts("  clear         — clear the screen\n");
        vga_puts("  mem           — show heap stats\n");
        vga_puts("  echo <text>   — print text\n");
        vga_puts("  malloc <n>    — allocate n bytes and show the address\n");

    } else if (kstrcmp(cmd, "clear") == 0) {
        vga_clear();

    } else if (kstrcmp(cmd, "mem") == 0) {
        vga_set_colour(VGA_CYAN, VGA_BLACK);
        vga_puts("\nMemory stats:\n");
        vga_set_colour(VGA_LIGHT_GREY, VGA_BLACK);
        memory_dump_stats();

    } else if (kstrncmp(cmd, "echo ", 5) == 0) {
        vga_putchar('\n');
        vga_puts(cmd + 5);

    } else if (kstrncmp(cmd, "malloc ", 7) == 0) {
        size_t n = katoi(cmd + 7);
        void *p  = kmalloc(n);
        if (p) {
            vga_printf("\nAllocated %u bytes at 0x%x", n, (uint32_t)p);
            kfree(p);
            vga_puts("  (freed)");
        }
    } else {
        vga_set_colour(VGA_LIGHT_RED, VGA_BLACK);
        vga_printf("\nUnknown command: '%s' (try 'help')", cmd);
        vga_set_colour(VGA_WHITE, VGA_BLACK);
    }
}

static void shell_loop(void) {
    shell_prompt();
    while (1) {
        char c = keyboard_getchar();
        if (c == '\n') {
            cmd[cmd_len] = '\0';
            run_command();
            cmd_len = 0;
            shell_prompt();
        } else if (c == '\b') {
            if (cmd_len > 0) {
                cmd_len--;
                vga_putchar('\b');
            }
        } else if (cmd_len < CMD_BUF - 1) {
            cmd[cmd_len++] = c;
            vga_putchar(c);
        }
    }
}

/* ── Entry point ─────────────────────────────────────────────────────────────
   Called from boot.asm after the stack is set up.
───────────────────────────────────────────────────────────────────────────── */
void kernel_main(void) {
    gdt_init();   /* MUST be first — installs our own GDT before any ISR fires */
    vga_init();

    /* Banner */
    vga_set_colour(VGA_YELLOW, VGA_BLACK);
    vga_puts("===========================================\n");
    vga_puts("          MyKernel v0.4 — x86 32-bit      \n");
    vga_puts("===========================================\n");

    vga_set_colour(VGA_CYAN, VGA_BLACK);
    vga_puts("[INIT] GDT...            ");
    vga_set_colour(VGA_LIGHT_GREEN, VGA_BLACK);
    vga_puts("OK\n");

    /* Subsystem initialisation */
    vga_set_colour(VGA_CYAN, VGA_BLACK);
    vga_puts("[INIT] Memory manager... ");
    memory_init();
    vga_set_colour(VGA_LIGHT_GREEN, VGA_BLACK);
    vga_puts("OK\n");

    vga_set_colour(VGA_CYAN, VGA_BLACK);
    vga_puts("[INIT] IDT & PIC...      ");
    pic_remap();
    idt_init();
    vga_set_colour(VGA_LIGHT_GREEN, VGA_BLACK);
    vga_puts("OK\n");

    vga_set_colour(VGA_CYAN, VGA_BLACK);
    vga_puts("[INIT] Keyboard driver.. ");
    keyboard_init();
    __asm__ volatile ("sti");      /* enable interrupts */
    vga_set_colour(VGA_LIGHT_GREEN, VGA_BLACK);
    vga_puts("OK\n");

    vga_set_colour(VGA_LIGHT_GREY, VGA_BLACK);
    vga_puts("\nType 'help' to see available commands.\n");

    shell_loop();   /* never returns */
}