doing some memory work and gdt and timer and vga

kernel/gdt.asm

@@ -0,0 +1,21 @@
+; gdt.asm
+; Assembler function to load the GDT and update segment registers
+
+global gdt_flush
+
+gdt_flush:
+    mov eax, [esp + 4]   ; Argument: pointer to GDT descriptor
+    lgdt [eax]           ; Load GDT
+
+    ; Reload segment registers
+    mov ax, 0x10         ; 0x10 = offset to kernel data segment (3rd entry)
+    mov ds, ax
+    mov es, ax
+    mov fs, ax
+    mov gs, ax
+    mov ss, ax
+
+    ; Jump to flush the instruction pipeline and load CS
+    jmp 0x08:.flush      ; 0x08 = offset to code segment (2nd entry)
+.flush:
+    ret

kernel/gdt.c

@@ -0,0 +1,48 @@
+#include "gdt.h"
+
+// Structure of a GDT entry (8 bytes)
+struct gdt_entry {
+    uint16_t limit_low;   // Limit bits 0–15
+    uint16_t base_low;    // Base bits 0–15
+    uint8_t  base_middle; // Base bits 16–23
+    uint8_t  access;      // Access flags
+    uint8_t  granularity; // Granularity + limit bits 16–19
+    uint8_t  base_high;   // Base bits 24–31
+} __attribute__((packed));
+
+// Structure of the GDT pointer
+struct gdt_ptr {
+    uint16_t limit;
+    uint32_t base;
+} __attribute__((packed));
+
+// Declare GDT with 3 entries
+static struct gdt_entry gdt[3];
+static struct gdt_ptr gp;
+
+// External ASM function to load GDT
+extern void gdt_flush(uint32_t);
+
+// Set an individual GDT entry
+static void gdt_set_gate(int num, uint32_t base, uint32_t limit, uint8_t access, uint8_t granularity) {
+    gdt[num].base_low    = (base & 0xFFFF);
+    gdt[num].base_middle = (base >> 16) & 0xFF;
+    gdt[num].base_high   = (base >> 24) & 0xFF;
+
+    gdt[num].limit_low   = (limit & 0xFFFF);
+    gdt[num].granularity = ((limit >> 16) & 0x0F) | (granularity & 0xF0);
+
+    gdt[num].access      = access;
+}
+
+// Initialize the GDT
+void gdt_init(void) {
+    gp.limit = (sizeof(struct gdt_entry) * 3) - 1;
+    gp.base  = (uint32_t)&gdt;
+
+    gdt_set_gate(0, 0, 0, 0, 0);                // Null segment
+    gdt_set_gate(1, 0, 0xFFFFFFFF, 0x9A, 0xCF); // Code segment
+    gdt_set_gate(2, 0, 0xFFFFFFFF, 0x92, 0xCF); // Data segment
+
+    gdt_flush((uint32_t)&gp);
+}

kernel/gdt.h

@@ -0,0 +1,8 @@
+#ifndef GDT_H
+#define GDT_H
+
+#include <stdint.h>
+
+void gdt_init(void);
+
+#endif

kernel/isr.c

@@ -1,11 +1,19 @@
 #include "terminal.h"
 #include "serial.h"
+#include "isr.h"
+
+static isr_callback_t interrupt_handlers[MAX_INTERRUPTS] = { 0 };
 
 void isr_handler(uint32_t int_num, uint32_t err_code) {
     terminal_write("Interrupt occurred: ");
-    // Add simple int-to-string printing here
+    // Here you can add a basic itoa to print int_num
     serial_write("INT triggered\n");
 
+    if (interrupt_handlers[int_num]) {
+        interrupt_handlers[int_num]();  // Call registered handler
+    } else {
+        terminal_write(" -> No handler registered\n");
+
         if (int_num == 0) {
             terminal_write(" -> Divide by zero error!\n");
         } else if (int_num == 13) {
@@ -18,4 +26,9 @@ void isr_handler(uint32_t int_num, uint32_t err_code) {
         while (1) {
             asm volatile ("hlt");
         }
+    }
+}
+
+void register_interrupt_handler(uint8_t n, isr_callback_t handler) {
+    interrupt_handlers[n] = handler;
 }

kernel/isr.h

@@ -0,0 +1,13 @@
+#ifndef ISR_H
+#define ISR_H
+
+#include <stdint.h>
+
+#define MAX_INTERRUPTS 256
+
+typedef void (*isr_callback_t)(void);
+
+void isr_handler(uint32_t int_num, uint32_t err_code);
+void register_interrupt_handler(uint8_t n, isr_callback_t handler);
+
+#endif

kernel/kmain.c

@@ -31,6 +31,17 @@ void kmain(void) {
     paging_init();
     serial_write("Paging initialized.\n");
 
+    terminal_write("Initializing memory allocator...\n");
+    kmalloc_init(0xC0100000);  // Virtual heap start address (must be mapped!)
+    serial_write("kmalloc initialized.\n");
+
+    void* ptr = kmalloc(128);  // Allocation test
+    serial_write("Allocated 128 bytes.\n");
+
+    terminal_write("Initializing timer...\n");
+    timer_init(100);  // 100 Hz (10 ms interval)
+    serial_write("Timer initialized.\n");
+
     terminal_write("Getting memory map...\n");
     memory_map_entry_t mmap[32];
     uint32_t mmap_size = get_memory_map(mmap, 32);

kernel/kmalloc.c

@@ -0,0 +1,38 @@
+#include "kmalloc.h"
+#include "terminal.h"  // Optional: for debug output
+
+static uint32_t current_heap = 0;
+
+// Initialize the allocator with a starting heap address
+void kmalloc_init(uint32_t heap_start) {
+    current_heap = heap_start;
+}
+
+// Simple bump allocator
+void* kmalloc(size_t size) {
+    if (current_heap == 0) {
+        terminal_write("kmalloc used before initialization!\n");
+        return 0;
+    }
+
+    void* addr = (void*)current_heap;
+    current_heap += size;
+    return addr;
+}
+
+// Allocate memory aligned to a power-of-two boundary (e.g., 0x1000)
+void* kmalloc_aligned(size_t size, uint32_t alignment) {
+    if (current_heap == 0) {
+        terminal_write("kmalloc_aligned used before initialization!\n");
+        return 0;
+    }
+
+    // Align the current_heap pointer
+    if ((current_heap & (alignment - 1)) != 0) {
+        current_heap = (current_heap + alignment) & ~(alignment - 1);
+    }
+
+    void* addr = (void*)current_heap;
+    current_heap += size;
+    return addr;
+}

kernel/kmalloc.h

@@ -0,0 +1,11 @@
+#ifndef KMALLOC_H
+#define KMALLOC_H
+
+#include <stdint.h>
+#include <stddef.h> // for size_t
+
+void kmalloc_init(uint32_t heap_start);
+void* kmalloc(size_t size);
+void* kmalloc_aligned(size_t size, uint32_t alignment);
+
+#endif

kernel/paging.c

@@ -2,20 +2,18 @@
 #include "io.h"
 
 page_directory_entry_t *page_directory = (page_directory_entry_t *)0x100000;
-page_table_entry_t *page_table = (page_table_entry_t *)0x101000; // Located right after the page directory
+page_table_entry_t *page_table = (page_table_entry_t *)0x101000;
+page_table_entry_t *heap_page_table = (page_table_entry_t *)0x102000; // Located right after the page directory
 
 // Helper function to set up the page directory entry
 void set_page_directory(page_directory_entry_t *dir) {
     for (int i = 0; i < PAGE_DIRECTORY_SIZE; i++) {
-        // Set up a page directory entry with identity mapping
-        dir[i].present = 9;
-        dir[i].rw = 0;           // Read/Write
-        dir[i].user = 0;         // Kernel mode
-        dir[i].write_through = 0;
-        dir[i].cache_disabled = 0;
-        dir[i].accessed = 0;
-        dir[0].frame = (uint32_t)page_table >> 12;
+        dir[i].present = 0;
     }
+    dir[0].present = 1;
+    dir[0].rw = 1;
+    dir[0].user = 0;
+    dir[0].frame = (uint32_t)page_table >> 12;
 }
 
 // Helper function to set up the page table entry
@@ -47,10 +45,26 @@ void enable_paging() {
 
 // Initialize paging: set up the page directory and enable paging
 void paging_init() {
-    // Set up the page directory and page tables
+    // Set up identity-mapped page directory + table
     set_page_directory(page_directory);
     set_page_table(page_table);
 
-    // Enable paging
+    // === Set up heap mapping at 0xC0100000 ===
+    for (int i = 0; i < PAGE_TABLE_SIZE; i++) {
+        heap_page_table[i].present = 1;
+        heap_page_table[i].rw = 1;
+        heap_page_table[i].user = 0;
+        heap_page_table[i].write_through = 0;
+        heap_page_table[i].cache_disabled = 0;
+        heap_page_table[i].accessed = 0;
+        heap_page_table[i].frame = (256 + i); // Start physical heap at 1MB (256*4KB = 1MB)
+    }
+
+    // Index 772 = 0xC0100000 / 4MB
+    page_directory[772].present = 1;
+    page_directory[772].rw = 1;
+    page_directory[772].user = 0;
+    page_directory[772].frame = (uint32_t)heap_page_table >> 12;
+
     enable_paging();
 }

kernel/paging.h

@@ -6,6 +6,7 @@
 #define PAGE_SIZE 4096                // Page size in bytes
 #define PAGE_DIRECTORY_SIZE 1024      // 1024 entries in page directory
 #define PAGE_TABLE_SIZE 1024          // 1024 entries in a page table
+#define KERNEL_HEAP_START 0xC0100000
 
 // Page Directory and Page Table structure
 typedef struct {

kernel/timer.c

@@ -0,0 +1,28 @@
+#include "timer.h"
+#include "io.h"
+#include "isr.h"
+#include "terminal.h"
+
+static uint32_t tick = 0;
+
+void timer_callback(void) {
+    tick++;
+    // Optional: Print every 100 ticks
+    // if (tick % 100 == 0) {
+    //     terminal_write("Tick\n");
+    // }
+}
+
+void timer_init(uint32_t frequency) {
+    register_interrupt_handler(32, timer_callback); // IRQ0 = Interrupt 32
+
+    uint32_t divisor = 1193180 / frequency;
+
+    outb(0x43, 0x36);             // Command byte
+    outb(0x40, divisor & 0xFF);   // Low byte
+    outb(0x40, (divisor >> 8));   // High byte
+}
+
+uint32_t timer_get_ticks(void) {
+    return tick;
+}

kernel/timer.h

@@ -0,0 +1,9 @@
+#ifndef TIMER_H
+#define TIMER_H
+
+#include <stdint.h>
+
+void timer_init(uint32_t frequency);
+uint32_t timer_get_ticks(void);
+
+#endif

kernel/vga.c

@@ -0,0 +1,9 @@
+#include "vga.h"
+
+uint8_t vga_entry_color(vga_color fg, vga_color bg) {
+    return fg | bg << 4;
+}
+
+uint16_t vga_entry(unsigned char uc, uint8_t color) {
+    return (uint16_t)uc | (uint16_t)color << 8;
+}

kernel/vga.h

@@ -0,0 +1,28 @@
+#ifndef VGA_H
+#define VGA_H
+
+#include <stdint.h>
+
+typedef enum {
+    VGA_COLOR_BLACK = 0,
+    VGA_COLOR_BLUE = 1,
+    VGA_COLOR_GREEN = 2,
+    VGA_COLOR_CYAN = 3,
+    VGA_COLOR_RED = 4,
+    VGA_COLOR_MAGENTA = 5,
+    VGA_COLOR_BROWN = 6,
+    VGA_COLOR_LIGHT_GREY = 7,
+    VGA_COLOR_DARK_GREY = 8,
+    VGA_COLOR_LIGHT_BLUE = 9,
+    VGA_COLOR_LIGHT_GREEN = 10,
+    VGA_COLOR_LIGHT_CYAN = 11,
+    VGA_COLOR_LIGHT_RED = 12,
+    VGA_COLOR_LIGHT_MAGENTA = 13,
+    VGA_COLOR_LIGHT_BROWN = 14,
+    VGA_COLOR_WHITE = 15,
+} vga_color;
+
+uint8_t vga_entry_color(vga_color fg, vga_color bg);
+uint16_t vga_entry(unsigned char uc, uint8_t color);
+
+#endif