fixed and added a lot more stuff like timer and acpi and ahci stub code and a kernel loader as well as worked on pci enumeration

src/boot/boot2.asm

@@ -40,16 +40,58 @@ start:
    call printstr
 
    ; Load the kernel into memory
-   ; ...
+   %include "kernel_loader.asm"
 
-   ; Set up GDT, IDT, IVT
-   ; ...
+   ; Set up IVT (GTD and IDT not used in 16 bit real mode)
+   ; Define interrupt handlers (replace with your actual handler code)
+   div_by_zero_handler:
+	   cli
+	   hlt
+
+   timer_handler:
+	   ; Your timer interrupt handler code
+	   hlt
+	   ret
+
+   ; IVT entries (offset 0 for all handlers since segment 0)
+   times 0x100 dw 0x0000  ; Initialize unused entries
+   dw offset div_by_zero_handler  ; Interrupt 0 (Division by Zero)
+   times 0x7 dw 0x0000          ; Skip unused entries
+   dw offset timer_handler      ; Interrupt 0x8 (Timer)
 
    ; Switch to protected mode
-   ; ...
+   ; Enable Protected Mode
+   switch_to_protected_mode:
+     cli                   ; Disable interrupts
+     mov eax, cr0           ; Get current CR0 value
+     or eax, 0x01           ; Set PE bit (Protected Mode Enable)
+     mov cr0, eax           ; Write modified CR0 value back
 
    ; Set up stack and start executing kernel's code
-   ; ...
+   ; Define GDT structure (replace with your actual GDT definition)
+   gdt_start:             ; Beginning of GDT
+     times 5 dd 0          ; Null descriptor entries (optional)
+   gdt_code:             ; Code segment descriptor
+     dw 0xffff             ; Segment size (limit)
+     dw 0x0000             ; Segment base address (low)
+     db 0x0              ; Segment base address (high)
+     db 10011010b           ; Access rights (present, readable, conforming, executable)
+     db 11001111b           ; Access rights (long mode, 4-granularity, size)
+   gdt_end:               ; End of GDT
+   gdt_descriptor:
+     equ gdt_end - gdt_start ; Size of GDT
+     dw gdt_descriptor      ; Offset of GDT
+     dd gdt_start           ; Base address of GDT
+
+   ; Load the GDT
+   lgdt [gdt_descriptor]   ; Load GDT descriptor into GDTR
+
+   ; Set up Stack (replace with your actual stack segment and address)
+   mov ss, data_segment    ; Set stack segment selector
+   mov esp, 0x100000       ; Set stack pointer (top of stack)
+
+   ; Start Kernel Execution
+   jmp farptr kernel_entry  ; Jump to kernel entry point (replace with actual address)
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ; printstr routine, prints the string pointed by si using int 0x10 ;

src/boot/kernel_loader.asm

@@ -0,0 +1,28 @@
+; Define constants (adjust as needed)
+boot_drive equ 0x00   ; Drive to load kernel from (usually 0 for primary)
+kernel_sector equ 1   ; Sector containing the kernel (adjust for your kernel's location)
+kernel_segments equ 4  ; Number of sectors to load (adjust for your kernel size)
+kernel_load_address equ 0x1000 ; Memory address to load the kernel
+
+; ... (Function prototypes and int_13h implementation copied from previous response)
+; Function prototypes for readability
+; (These functions are not strictly necessary in NASM, but improve code organization)
+; Prototype for BIOS disk read interrupt (INT 13h)
+void int_13h(unsigned int ah, unsigned int al, unsigned int dx, unsigned int ch, unsigned int cl, unsigned int bx);
+
+; Function prototype for error handling or printing a message
+void error_handler(const char *message);
+; Main kernel loading code
+mov bx, kernel_load_address  ; Set load address
+
+; Loop to load kernel sectors
+mov cx, 0                     ; Initialize counter
+loop_load:
+    int_13h(0x02, kernel_segments, boot_drive * 256 + kernel_sector, ch, cl, bx)  ; Read sectors
+    add bx, 512 * kernel_segments  ; Update load address
+    inc cx                        ; Increment counter
+    cmp cx, kernel_segments        ; Check if all sectors loaded
+    jne loop_load                  ; Jump back if not finished
+
+; Success - kernel is now loaded into memory
+ret      ; Return to the main bootloader code

src/drivers/bus/pci.c

@@ -20,28 +20,129 @@ void pci_init()
 	pci_write(PCI_COMMAND_PORT, 0x04);
 }
 
+// Read from a PCI device
+uint8_t pci_read_config(uint8_t bus, uint8_t device, uint8_t function, uint8_t offset)
+{
+	uint16_t port = PCI_BASE_ADDRESS | ((uint16_t)bus << 8) | ((uint16_t)device << 3) | ((uint16_t)function << 0x0B) | ((uint16_t)offset & 0xFC);
+	uint8_t value;
+
+	// Read from the specified port
+	__asm__ volatile("inb %1, %0" : "=a"(value) : "dN"(port));
+
+	return value;
+}
+// Function to write a value to a PCI configuration register
+void pci_write_config(uint8_t bus, uint8_t device, uint8_t function, uint8_t offset, uint8_t value)
+{
+	// ... (your existing implementation for setting up the port address)
+
+	// Write the specified value to the specified offset
+	__asm__ volatile("outb %0, %1" : : "a"(value), "dN"(port));
+}
+
+// Set the PCI Latency Timer for a device
+void pci_set_latency(uint8_t bus, uint8_t device, uint8_t function, uint8_t value)
+{
+	pci_write_config(bus, device, function, 0x0D, value);
+}
+
+uint16_t pci_read_config_word(uint8_t bus, uint8_t device, uint8_t function, uint8_t offset)
+{
+	uint16_t value = 0;
+	value |= pci_read_config(bus, device, function, offset);
+	value |= (uint16_t)pci_read_config(bus, device, function, offset + 1) << 8;
+	return value;
+}
+
+// Function to read a 32-bit value from PCI configuration space
+uint32_t pci_read_config_dword(uint8_t bus, uint8_t device, uint8_t function, uint8_t offset)
+{
+	uint32_t value = 0;
+	value |= pci_read_config(bus, device, function, offset);
+	value |= (uint32_t)pci_read_config(bus, device, function, offset + 1) << 8;
+	value |= (uint32_t)pci_read_config(bus, device, function, offset + 2) << 16;
+	value |= (uint32_t)pci_read_config(bus, device, function, offset + 3) << 24;
+	return value;
+}
+
+// Structure to hold information about a BAR
+typedef struct
+{
+	uint8_t type;  // Memory (0) or I/O (1)
+	uint32_t base; // Base address
+	uint32_t size; // Size of the region (in bytes)
+} bar_t;
+
+// Function to decode a BAR register
+bar_t pci_decode_bar(uint32_t bar_value)
+{
+	bar_t bar;
+	bar.type = (bar_value & 1) ? 1 : 0; // Check bit 0 for type
+
+	// Extract address and size information (logic might need adjustment)
+	bar.base = bar_value & ~((1 << 0) | (1 << 1)); // Mask out type and prefetchable bits
+
+	// Size calculation needs further processing based on Memory Space Enable bit (bit 3)
+	uint32_t size_bits = bar_value & ~(bar.base | (1 << 0) | (1 << 1) | (1 << 3));
+	if (size_bits == 0)
+	{ // Handle case where size is 0
+		bar.size = 0;
+	}
+	else
+	{
+		// Calculate size based on the number of leading 1s in size_bits
+		int num_leading_ones = 0;
+		while (size_bits && (size_bits & 0x80000000))
+		{
+			num_leading_ones++;
+			size_bits <<= 1;
+		}
+		bar.size = 1 << num_leading_ones;
+	}
+
+	return bar;
+}
 // Detect and configure PCI devices
 void pci_detect_devices()
 {
 	// Scan all PCI buses and devices
-    for (int bus = 0; bus < 256; bus++) {
-        for (int device = 0; device < 32; device++) {
-            for (int function = 0; function < 8; function++) {
+	for (int bus = 0; bus < 256; bus++)
+	{
+		for (int device = 0; device < 32; device++)
+		{
+			for (int function = 0; function < 8; function++)
+			{
 				uint16_t vendor_id = pci_read(bus, device, function, 0x00);
-                if (vendor_id != 0xFFFF) {
+				if (vendor_id != 0xFFFF)
+				{
 					uint16_t device_id = pci_read(bus, device, function, 0x02);
+
+					// Lookup vendor and device ID in a database (e.g., PCI.ids)
+					const char *device_name = lookup_device_name(vendor_id, device_id);
+
+					if (device_name != NULL)
+					{
+						// Device identified!
+						printk("Found PCI device: %s (vendor: %04x, device: %04x)\n",
+							   device_name, vendor_id, device_id);
+
+						// ... (Optional) Further configuration based on device type
+					}
+					else
+					{
+						// Device not found in database, handle unknown device
+						printk("Found unknown PCI device (vendor: %04x, device: %04x)\n",
+							   vendor_id, device_id);
+					}
+
+					// Continue reading other registers, handling BARs, etc.
 					uint8_t class_code = pci_read(bus, device, function, 0x0B);
 					uint8_t subclass_code = pci_read(bus, device, function, 0x0A);
 					uint8_t prog_if = pci_read(bus, device, function, 0x09);
 					uint8_t header_type = pci_read(bus, device, function, 0x0E);
 					uint8_t irq_line = pci_read(bus, device, function, 0x3C);
-                    uint32_t bar0 = pci_read(bus, device, function, 0x10);
-                    uint32_t bar1 = pci_read(bus, device, function, 0x14);
-                    uint32_t bar2 = pci_read(bus, device, function, 0x18);
-                    uint32_t bar3 = pci_read(bus, device, function, 0x1C);
-                    uint32_t bar4 = pci_read(bus, device, function, 0x20);
-                    uint32_t bar5 = pci_read(bus, device, function, 0x24);
-                    // Add any necessary device detection and configuration code here
+
+					// ... (rest of your code for handling BARs, etc.)
 				}
 			}
 		}

src/drivers/display/vga.c

@@ -7,30 +7,31 @@
 #include <unistd.h>
 
 uint8_t *map_memory(uint32_t base_address, uint32_t size);
-
-#define VGA_MEMORY_ADDRESS 0xA0000
-#define VGA_MEMORY_SIZE 0x60000
-#define VGA_MEMORY_BASE_ADDRESS 0xA0000
-
-#define COLOR_GREEN 0x00FF00
-
 uint8_t *vga_memory = (uint8_t *)VGA_MEMORY_ADDRESS;
 static uint16_t vga_width = VGA_WIDTH;
 static uint16_t vga_height = VGA_HEIGHT;
 static uint8_t vga_depth = VGA_DEPTH;
 uint8_t *framebuffer = (uint8_t *)vga_memory;
+uint8_t *map_memory(uint32_t base_address, uint32_t size);
+uint8_t read_vga_register(uint16_t register_address);
+int inb(uint16_t port);
+void outb(uint16_t port, uint8_t data);
+uint16_t width;
+uint32_t get_vga_memory_address();
 
 // Set a specific pixel color (assuming RGB format)
 int x = 10;
 int y = 20;
 int color = 0x00FF00; // Green
 
-framebuffer[y * width + x * 3] = (color & 0x00FF) >> 8; // Green value
-framebuffer[y * width + x * 3 + 1] = color & 0x00FF;	// Blue value
-framebuffer[y * width + x * 3 + 2] = color >> 8;		// Red value
+void some_function()
+{
+	// ... other code ...
+	uint8_t misc_output_value = read_vga_register(0x3C2); // Initialize here
+														  // ... use misc_output_value ...
+}
 
 uint8_t misc_output_value = read_vga_register(0x3C2);
-
 // Check bit 1 to determine text mode (0) or graphics mode (1)
 if (misc_output_value & 0x02)
 {
@@ -53,7 +54,7 @@ uint32_t get_vga_memory_address()
 void vga_init(void)
 {
 	// Initialize VGA driver here
-	vga_memory = (uint8_t *)map_memory(VGA_MEMORY_BASE_ADDRESS, VGA_MEMORY_SIZE);
+	vga_memory = (uint8_t *)map_memory(VGA_MEMORY_ADDRESS, VGA_MEMORY_SIZE);
 
 	if (vga_memory == NULL)
 	{
@@ -61,7 +62,7 @@ void vga_init(void)
 		fprintf(stderr, "Failed to map VGA Memory\n");
 	}
 
-	framebuffer = vga_memory;
+	framebuffer = (uint8_t *)vga_memory;
 }
 
 // Replace with actual functions to read VGA registers based on your system
@@ -71,28 +72,33 @@ uint8_t read_vga_register(uint16_t register_address)
 	return value;
 }
 
-int inb(uint16_t port) {
-    // Implement port access logic (replace with system-specific function)
+int inb(uint16_t port)
+{
+	uint8_t value;
+	__asm volatile("inb %1, %0" : "=a"(value) : "d"(port));
+	return value;
 }
 
-void outb(uint16_t port, uint8_t data) {
-
+void outb(uint16_t port, uint8_t data)
+{
+	__asm volatile("outb %0, %1" : : "a"(data), "d"(port));
 }
 
 void vga_set_resolution(uint16_t width, uint16_t height, uint8_t depth)
 {
-	// Set VGA resolution here
-	// Example (replace with actual register values and writes based on your system):
 
 	// Sequencer unlock
 	outb(0x3C4, 0x01);
 	outb(0x3C5, 0x01);
 
 	// Set specific CRTC registers for desired resolution and refresh rate
-	// ... (write to specific VGA registers using outb)
+	outb(0x3D4, 0x01); // Horizontal total
+	outb(0x3D5, 0x5F); // ...
+	// ... (set other CRTC registers)
 
 	// Graphics controller registers for memory access
-	// ... (write to specific VGA registers using outb)
+	outb(0x3CE, 0x05); // Graphics mode
+	outb(0x3CF, 0x03);
 }
 
 void vga_draw_pixel(uint16_t x, uint16_t y, uint8_t color)
@@ -100,6 +106,9 @@ void vga_draw_pixel(uint16_t x, uint16_t y, uint8_t color)
 	// Draw a pixel on the screen at (x, y) with the given color
 	uint32_t offset = y * vga_width + x;
 	vga_memory[offset] = color;
+	framebuffer[y * width + x * 3] = (color & 0x00FF) >> 8; // Green value
+	framebuffer[y * width + x * 3 + 1] = color & 0x00FF;	// Blue value
+	framebuffer[y * width + x * 3 + 2] = color >> 8;		// Red value
 }
 
 void vga_clear_screen(uint8_t color)

src/drivers/display/vga.h

@@ -3,14 +3,22 @@
 
 #include <stdint.h>
 
-typedef struct {
+#define VGA_WIDTH 320			   // Replace with the desired width
+#define VGA_HEIGHT 200			   // Replace with the desired height
+#define VGA_DEPTH 8				   // Replace with the desired color depth (e.g., 8 for 256 colors)
+#define VGA_MEMORY_ADDRESS 0xA0000 // Move to header file
+#define VGA_MEMORY_SIZE 0x60000	   // Move to header file
+#define COLOR_GREEN 0x00FF00
+#define VGA_MAP_MEM_ERROR -1
+
+typedef struct
+{
 	uint16_t width;
 	uint16_t height;
 	uint8_t depth;
 	// Add other relevant settings like color palette, etc.
 } vga_display_settings_t;
 
-void vga_init();
 void vga_set_resolution(uint16_t width, uint16_t height, uint8_t depth);
 void vga_draw_pixel(uint16_t x, uint16_t y, uint8_t color);
 void vga_clear_screen(uint8_t color);

src/kernel/acpi.c

@@ -0,0 +1,33 @@
+#include "acpi.h"
+#include <stdint.h>
+#include <stdbool.h>
+
+// Function prototypes (implementations below)
+acpi_fadt_t *acpi_find_fadt();
+int acpi_validate_rsdt(acpi_fadt_t *fadt);
+
+// ... (Add other ACPI functions for table parsing, resource access, etc.)
+
+// Function to locate the FADT table
+acpi_fadt_t *acpi_find_fadt() {
+  // Read the RSDP (Root System Description Pointer) signature and checksum
+  // at the ACPI base address.
+  acpi_fadt_t *rsdp = (acpi_fadt_t *)ACPI_BASE;
+  if (rsdp->signature != *(uint32_t *)"RSDT" && rsdp->signature != *(uint32_t *)"XSDT") {
+    return NULL; // Not a valid ACPI signature
+  }
+  if (rsdp->checksum != 0) {
+    return NULL; // Invalid checksum
+  }
+
+  // Check ACPI revision and use appropriate table address (RSDT or XSDT)
+  return (acpi_fadt_t *)(rsdp->revision >= 2 ? rsdp->xsdt_addr : rsdp->rsdp_addr);
+}
+
+// Function to validate the RSDT (or XSDT) table
+int acpi_validate_rsdt(acpi_fadt_t *fadt) {
+  // Check table length and perform basic integrity checks
+  // ...
+
+  return 0; // Assuming success, replace with actual validation logic
+}

src/kernel/acpi.h

@@ -0,0 +1,25 @@
+#ifndef ACPI_H
+#define ACPI_H
+
+#include <stdint.h>
+
+// ACPI base address (replace with actual value)
+#define ACPI_BASE 0xE0000000
+
+// ACPI Fixed ACPI Description Table (FADT) structure
+typedef struct
+{
+	uint32_t signature;		 // Signature ("RSDT" or "XSDT")
+	uint32_t length;		 // Length of the table
+	uint8_t revision;		 // ACPI revision
+	uint8_t checksum;		 // Checksum (should be zero)
+	uint32_t oem_id[6];		 // OEM ID string
+	uint8_t oem_revision[8]; // OEM revision string
+	uint32_t rsdp_addr;		 // Physical address of RSDT (for ACPI 1.0)
+	uint32_t xsdt_addr;		 // Physical address of XSDT (for ACPI 2.0+)
+							 // ... other FADT fields (refer to ACPI specification)
+} __attribute__((packed)) acpi_fadt_t;
+
+// ... (Add other ACPI table structure definitions as needed)
+
+#endif /* ACPI_H */

src/kernel/ahci.c

@@ -0,0 +1,36 @@
+#include "ahci.h"
+#include <stdint.h>
+
+// Function prototypes (implementations below)
+uint32_t ahci_read_reg(uint32_t offset);
+void ahci_write_reg(uint32_t offset, uint32_t value);
+
+// Function to send an AHCI command
+int ahci_send_command(uint32_t cmd_slot, ahci_cmd_t *cmd);
+
+// ... (Add other AHCI functions for initialization, status checks, etc.)
+
+// Helper function to read a 32-bit register
+uint32_t ahci_read_reg(uint32_t offset)
+{
+	return *(volatile uint32_t *)(HBA_PORT_BASE + offset);
+}
+
+// Helper function to write a 32-bit register
+void ahci_write_reg(uint32_t offset, uint32_t value)
+{
+	*(volatile uint32_t *)(HBA_PORT_BASE + offset) = value;
+}
+
+// Function to send an AHCI command
+int ahci_send_command(uint32_t cmd_slot, ahci_cmd_t *cmd)
+{
+	// Implement logic to write the command list entry to appropriate registers
+	// ...
+
+	// Wait for command completion (check relevant AHCI registers)
+	// ...
+
+	// Return status based on completion and error checking
+	// ...
+}

src/kernel/ahci.h

@@ -0,0 +1,28 @@
+#ifndef AHCI_H
+#define AHCI_H
+
+#include <stdint.h>
+
+// Base address of AHCI registers (replace with actual value)
+#define HBA_PORT_BASE 0x10000000
+
+// AHCI register offsets
+#define HBA_CAP 0x00	 // Host Capabilities
+#define HBA_PI 0x0C		 // Port Interrupt
+#define HBA_ISR 0x20	 // Interrupt Status
+#define HBA_IMR 0x30	 // Interrupt Mask
+#define HBA_CMD 0x34	 // Command List Head
+#define HBA_CMD_SLOT_0 0 // First command slot
+
+// AHCI command list structure
+typedef struct
+{
+	uint32_t cmd_sts;	  // FIS (Frame in flight)
+	uint32_t prdt_addr;	  // Physical address of PRDT (SATA FIS)
+	uint32_t prdt_length; // Length of PRDT in bytes
+	uint32_t reserved[4]; // Reserved (set to 0)
+} __attribute__((packed)) ahci_cmd_t;
+
+// ... (Add other AHCI register definitions and structures as needed)
+
+#endif /* AHCI_H */

src/kernel/arch/x86/idt.asm

@@ -1,7 +1,12 @@
-global LoadIDT
+global LoadIDT  ; Declare function as global
+
+_offset idt db 0
+
+section .text  ; Code section
+
+%include "idt.h"
 
-section .text
 LoadIDT:
-mov eax, [offset idt] ; Get the IDT address
-    LIDT [eax + 8*0x33]   ; Load only the timer interrupt entry (offset 8*0x33)
-    RET
+    mov eax, [esp + 4] ; Get IDT address (ensure offset idt is defined)
+    LIDT [eax]  ; Load timer interrupt entry (check for correct brackets)
+    RET                 ; Return from function

src/kernel/arch/x86/include/types.c

@@ -1,4 +1,5 @@
 #include "./types.h"
+#include <stdint.h>
 
 void gdt_set_entry(gdt_entry_t *entry, uint32_t base, uint32_t limit,
                    uint16_t flags)

src/kernel/arch/x86/isr/isr.asm

@@ -1,7 +1,13 @@
-section .text
-global isr_handler
-global _isr_stub
+%include "isr.h"
 
+section .data
+    ISR_HAS_ERROR_CODE equ 1
+    ISR_IS_HARDWARE_INTERRUPT equ 1
+
+section .text
+global isr_stub
+
+global _isr_stub
 _isr_stub:
     ; Save context
     PUSHAD ; Preserve all general-purpose registers
@@ -10,41 +16,36 @@ _isr_stub:
     CLI
 
     ; Align stack to 16-byte boundary for performance (if needed)
-    ; AND ESP, 0xFFFFFFF0
+    AND ESP, 0xFFFFFFF0
 
     ; Check if an error code is present (typically in EAX)
     ; This is just a placeholder, actual implementation depends on your IDT setup
     CMP BYTE [ISR_HAS_ERROR_CODE], 1
     JNE no_error_code
     PUSH DWORD [ESP + 32] ; Push error code
-    JMP done_pushing_error_code
+
 no_error_code:
-    PUSH DWORD 0 ; Push a dummy error code
-done_pushing_error_code:
-
-    ; Push interrupt number onto the stack
-    MOV EAX, [ESP + 36] ; Move interrupt number to EAX (accounting for the dummy/error code)
-    PUSH EAX ; Interrupt number
-
-    ; Call isr_handler
+	PUSH DWORD 0
+	MOV EAX, [ESP + 36]
+	PUSH EAX
+	; Call the C ISR handler
     CALL isr_handler
 
-    ; Send EOI to PIC only if it's a hardware interrupt
-    ; This is just a placeholder, actual implementation depends on your IDT setup
-    CMP BYTE [ISR_IS_HARDWARE_INTERRUPT], 1
+    MOV AL, BYTE [ISR_IS_HARDWARE_INTERRUPT]
+	CMP AL, 1
+
 	JNE skip_eoi
 	MOV AL, 0x20
 	OUT 0x20, AL
+
 skip_eoi:
 
+    POPAD
     ; Enable interrupts
     STI
 
     ; Clean up the stack
-    ADD ESP, 8 ; Remove error code and interrupt number
-
-    ; Restore context
-    POPAD ; Restore all general-purpose registers
+    ADD ESP, 16 ; Remove error code and interrupt number
 
     ; Return from interrupt
     IRETD

src/kernel/arch/x86/isr/isr.c

@@ -1,4 +1,5 @@
 #include "isr.h"
+#include <stdio.h>
 
 void isr_handler(struct isr_regs regs) {
     switch(regs.int_no) {

src/kernel/arch/x86/isr/isr.h

@@ -2,6 +2,7 @@
 #define ISR_H
 
 #include "../include/types.h"
+#include <stdio.h>
 
 enum ISR_Vector
 {
@@ -33,6 +34,7 @@ struct isr_regs
         esp_at_signal; // Pushed by the processor automatically
 };
 
+void isr_handler(struct isr_regs regs);
 // Structure for storing register values during an ISR
 struct idt_regs
 {

src/kernel/malloc/kmalloc.c

@@ -2,15 +2,72 @@
 
 static void *kernel_heap_start; // Start of the kernel heap
 static void *kernel_heap_end;	// End of the kernel heap
+static struct memory_block *free_blocks = NULL;
 
-void init_kernel_heap(void *start, void *end) {
-    kernel_heap_start = start;
-    kernel_heap_end = end;
-    // Initialize the kernel heap here
+struct memory_block
+{
+	size_t size;
+	struct memory_block *next;
+};
+
+void mark_as_used_kernel(void *ptr, size_t size)
+{
+	// Since we're using a linked list, there's no specific action needed
+	//  to mark the block itself as used (it's already removed from the list).
+	// However, you might want to perform additional bookkeeping for debugging
+	// or memory analysis purposes.
+
+	// Example: Update some metadata associated with the allocated block
+	// ((struct memory_block *)ptr)->used = true; // Assuming a 'used' flag
+
+	// This function can be potentially empty if you don't require specific
+	// actions for marking a block as used in the kernel.
 }
 
-void *kmalloc(size_t size) {
-    if (kernel_heap_start == NULL || kernel_heap_end == NULL) {
+void mark_as_free_kernel(void *ptr)
+{
+	// Cast the pointer to a memory_block structure
+	struct memory_block *block = (struct memory_block *)ptr;
+
+	// Add the block to the beginning of the free block list
+	block->next = free_blocks;
+	free_blocks = block;
+}
+
+void init_kernel_heap(void *start, void *end)
+{
+	kernel_heap_start = start;
+	kernel_heap_end = end;
+
+	free_blocks = (struct memory_block *)start;
+	free_blocks->size = (size_t)(end - start);
+	free_blocks->next = NULL;
+
+	// You'll need to replace this placeholder with logic to split the
+	// initial block into smaller ones based on your requirements.
+}
+
+void *find_free_kernel_block(size_t size)
+{
+	// First-fit algorithm (can be optimized with different strategies)
+	struct memory_block *current = free_blocks;
+	while (current != NULL)
+	{
+		if (current->size >= size)
+		{
+			// Found a suitable block
+			return current;
+		}
+		current = current->next;
+	}
+	// No suitable block found
+	return NULL;
+}
+
+void *kmalloc(size_t size)
+{
+	if (kernel_heap_start == NULL || kernel_heap_end == NULL)
+	{
 		// Kernel heap not initialized, cannot allocate
 		return NULL;
 	}
@@ -20,11 +77,17 @@ void *kmalloc(size_t size) {
 	size &= ~(sizeof(size_t) - 1);
 
 	// Search for a free block of sufficient size
-    // This is a placeholder for the actual algorithm
 	void *block = find_free_kernel_block(size);
-    if (block != NULL) {
+	if (block != NULL)
+	{
 		// Mark the block as used
 		mark_as_used_kernel(block, size);
+
+		// This is a placeholder for splitting the block if necessary
+		// You'll need to implement logic to potentially split the block
+		// into a used part of size 'size' and a remaining free block
+		// if the block size is significantly larger than 'size'.
+
 		return block;
 	}
 
@@ -32,8 +95,10 @@ void *kmalloc(size_t size) {
 	return NULL;
 }
 
-void kfree(void *ptr) {
-    if (ptr == NULL) {
+void kfree(void *ptr)
+{
+	if (ptr == NULL)
+	{
 		return;
 	}
 

src/kernel/malloc/kmalloc.h

@@ -1,9 +1,12 @@
-#ifndef KMALLOC_H
-#define KMALLOC_H
+#ifndef KMALLOC_H_  // Corrected guard macro
+#define KMALLOC_H_
 
 #include <stddef.h> // For size_t
 
 void *kmalloc(size_t size);
 void kfree(void *ptr);
 
-#endif // KMALLOC_H
+void mark_as_used_kernel(void *ptr, size_t size);
+void mark_as_free_kernel(void *ptr);
+
+#endif /* KMALLOC_H_ */

src/kernel/malloc/malloc.c

@@ -10,6 +10,20 @@ void init_heap(void *start, void *end)
 	// Initialize the heap here
 }
 
+void *find_free_block(size_t size) {
+  // Implementation is similar to find_free_kernel_block
+  struct memory_block *current = free_blocks;
+  while (current != NULL) {
+    if (current->size >= size) {
+      return current;
+    }
+    current = current->next;
+  }
+
+  // No suitable block found
+  return NULL;
+}
+
 void *malloc(size_t size)
 {
 	if (heap_start == NULL || heap_end == NULL)

src/kernel/malloc/malloc.h

@@ -6,4 +6,6 @@
 void *malloc(size_t size);
 void free(void *ptr);
 
+void *find_free_block(size_t size);
+
 #endif // MALLOC_H

src/kernel/timer.c

@@ -1,3 +1,26 @@
-/*
-timer functions go here
-*/
+#include <stdint.h>
+#include "timer.h"
+
+// Function to send a byte to an I/O port
+void outb(uint16_t port, uint8_t data) {
+    __asm__ volatile ("outb %b, %w" : : "a" (data), "d" (port));
+}
+
+// Function to initialize the timer with a desired frequency
+void init_timer(uint32_t frequency) {
+  // Calculate the divisor based on the desired frequency
+  uint16_t divisor = 1193180 / frequency;
+
+  // Send the mode and divisor byte to the timer control port
+  outb(IOPORT_TIMER_CONTROL, TIMER_CTRL_SELECT_0 | TIMER_MODE_3 | TIMER_CTRL_BINARY);
+  outb(IOPORT_TIMER_0, (uint8_t) (divisor & 0xFF));
+  outb(IOPORT_TIMER_0, (uint8_t) ((divisor >> 8) & 0xFF));
+}
+
+// Function to wait for a specified number of microseconds
+void wait_us(uint32_t microseconds) {
+  uint32_t count = microseconds * 10; // Adjust for desired resolution (1 count = 100ns)
+  while (count--) {
+    // Implement a short delay loop here (e.g., empty loop or reading the PIT)
+  }
+}

src/kernel/timer.h

@@ -1,3 +1,37 @@
-/*
-timer functions go here
-*/
+Here's a breakdown of how to create timer.c and timer.h compatible with the 8253 for x86 32-bit protected mode on 386/486 processors:
+
+1. timer.h:
+
+This header file will contain function prototypes, constants, and any data structures you might need for interacting with the 8253 timer. Here's an example:
+C
+
+#ifndef TIMER_H
+#define TIMER_H
+
+#include <stdint.h>
+
+// I/O port addresses for the 8253
+#define IOPORT_TIMER_CONTROL 0x43
+#define IOPORT_TIMER_0 0x40
+
+// Timer modes (refer to 8253 documentation for details)
+#define TIMER_MODE_0 0x00
+#define TIMER_MODE_1 0x40
+#define TIMER_MODE_2 0x80
+#define TIMER_MODE_3 0xC0
+
+// Timer control bits (refer to 8253 documentation for details)
+#define TIMER_CTRL_SELECT_0 0x01
+#define TIMER_CTRL_SELECT_1 0x02
+#define TIMER_CTRL_SELECT_2 0x04
+#define TIMER_CTRL_MODE 0x30
+#define TIMER_CTRL_BINARY 0x00
+#define TIMER_CTRL_BCD 0x40
+#define TIMER_CTRL_ONE_SHOT 0x80
+#define TIMER_CTRL_CONTINOUS 0x00
+
+// Function prototypes
+void init_timer(uint32_t frequency);
+void wait_us(uint32_t microseconds);
+
+#endif /* TIMER_H */