mostly improvements to malloc

bootloader/linker.ld

@@ -14,4 +14,14 @@ SECTIONS {
         *(.bss*)
         *(COMMON)
     }
+
+    .stack (NOLOAD) : {
+        . = ALIGN(4);
+        . = . + 0x1000;
+    }
+
+    .heap (NOLOAD) : {
+        . = ALIGN(4);
+        . = . + 0x10000;
+    }
 }

kernel/cpu.c

@@ -2,6 +2,7 @@
 #include "serial.h"
 #include "terminal.h"
 #include "utils.h"
+#include "print.h"
 
 void cpuid(uint32_t function, uint32_t *eax, uint32_t *ebx, uint32_t *ecx, uint32_t *edx) {
     asm volatile (

kernel/fat12.c

@@ -1,5 +1,5 @@
-#include "fs.h"
+#include "fat12.h"
 
-void fs_init() {
+void fat12_init() {
     // Filesystem initialization code
 }

kernel/fat12.h

@@ -0,0 +1,47 @@
+#ifndef FAT12_H
+#define FAT12_H
+
+#include <stdint.h> /* Include standard integer types */
+#include <stdio.h>  /* Include standard I/O library */
+#include <stdlib.h> /* Include standard library */
+
+#define FAT12_SECTOR_SIZE 512 /* Sector size for FAT12 */
+#define FAT12_MAX_FILES 128 /* Maximum number of files in root directory */
+#define FAT12_ROOT_DIR_SECTORS 1 /* Number of sectors for root directory */
+
+typedef struct {
+    uint8_t jump[3]; /* Jump instruction for boot */
+    char oem[8]; /* OEM name */
+    uint16_t bytes_per_sector; /* Bytes per sector */
+    uint8_t sectors_per_cluster; /* Sectors per cluster */
+    uint16_t reserved_sectors; /* Reserved sectors count */
+    uint8_t num_fats; /* Number of FATs */
+    uint16_t max_root_dir_entries; /* Max entries in root directory */
+    uint16_t total_sectors; /* Total sectors */
+    uint8_t media_descriptor; /* Media descriptor */
+    uint16_t fat_size; /* Size of each FAT */
+    uint16_t sectors_per_track; /* Sectors per track */
+    uint16_t num_heads; /* Number of heads */
+    uint32_t hidden_sectors; /* Hidden sectors count */
+    uint32_t total_sectors_large; /* Total sectors for large disks */
+} __attribute__((packed)) FAT12_BootSector; /* Packed structure for boot sector */
+
+typedef struct {
+    char name[11]; /* File name (8.3 format) */
+    uint8_t attr; /* File attributes */
+    uint16_t reserved; /* Reserved */
+    uint16_t time; /* Time of last write */
+    uint16_t date; /* Date of last write */
+    uint16_t start_cluster; /* Starting cluster number */
+    uint32_t file_size; /* File size in bytes */
+} __attribute__((packed)) FAT12_DirEntry; /* Directory entry structure */
+
+void initialize_fat12(const char *disk_image); /* Function to initialize FAT12 */
+void read_fat12(const char *disk_image); /* Function to read FAT12 */
+void write_fat12(const char *disk_image); /* Function to write FAT12 */
+void list_files(const char *disk_image); /* Function to list files in root directory */
+void read_file(const char *disk_image, const char *filename); /* Function to read a file */
+void write_file(const char *disk_image, const char *filename, const uint8_t *data, size_t size); /* Function to write a file */
+
+#endif 
+/* FAT12_H */

kernel/fs.h

@@ -1,6 +0,0 @@
-#ifndef FS_H
-#define FS_H
-
-void fs_init();
-
-#endif // FS_H

kernel/kmalloc.c

@@ -1,6 +1,8 @@
 #include "kmalloc.h"
 #include "terminal.h"  // Optional: for debug output
 
+#define HEAP_END 0xC0100000
+
 static uint32_t current_heap = 0;
 
 // Initialize the allocator with a starting heap address
@@ -32,7 +34,18 @@ void* kmalloc_aligned(size_t size, uint32_t alignment) {
         current_heap = (current_heap + alignment) & ~(alignment - 1);
     }
 
+    if (current_heap + size > HEAP_END) {
+        terminal_write("kmalloc_aligned: Out of memory!\n");
+        return 0;
+    }
+
     void* addr = (void*)current_heap;
     current_heap += size;
     return addr;
 }
+
+void kfree(void* ptr) {
+    // In a bump allocator, we cannot free individual blocks.
+    // We can reset the allocator to the initial state.
+    current_heap = 0; // Reset the heap pointer
+}

kernel/malloc.c

@@ -55,7 +55,15 @@ void mark_as_free(void *ptr) {
         block->next = block->next->next;
     }
 
-    // TODO: Implement coalescing with previous block
+    // Coalesce with previous block if it's free
+    struct memory_block *prev = free_blocks;
+    while (prev && prev->next != block) {
+        prev = prev->next;
+    }
+    if (prev && prev->is_free) {
+        prev->size += block->size + sizeof(struct memory_block);
+        prev->next = block->next;
+    }
 }
 
 void *malloc(size_t size)
@@ -94,4 +102,4 @@ void free(void *ptr)
 
     // Mark the block as free
     mark_as_free(block);
-}
+}

kernel/print.c

@@ -1,6 +1,84 @@
 #include <stdio.h>
+#include <stdarg.h>
+#include "print.h"
 
-void print_string(const char *str)
+void my_putchar(char ch) {
-{
+    // Write a single character to standard output
-    printf("%s", str);
+    // In a freestanding environment, you might need to implement this differently
+    // For now, we will use the standard putchar for demonstration
+    // Replace this with your own implementation if needed
+    putchar(ch);
+}
+
+void print_string(const char *str) {
+    // Simple implementation to print a string
+    while (*str) {
+        my_putchar(*str++);
+    }
+}
+
+void my_printf(const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+
+    while (*format) {
+        if (*format == '%') {
+            format++; // Move to the next character after '%'
+            switch (*format) {
+                case 's': { // String
+                    char *str = va_arg(args, char *);
+                    print_string(str);
+                    break;
+                }
+                case 'd': { // Integer
+                    int num = va_arg(args, int);
+                    char buffer[20]; // Buffer to hold the string representation
+                    snprintf(buffer, sizeof(buffer), "%d", num);
+                    print_string(buffer);
+                    break;
+                }
+                case 'c': { // Character
+                    char ch = (char)va_arg(args, int); // Promote char to int
+                    my_putchar(ch);
+                    break;
+                }
+                default:
+                    my_putchar('%'); // Print the '%' if no valid format specifier
+                    my_putchar(*format);
+                    break;
+            }
+        } else {
+            my_putchar(*format);
+        }
+        format++;
+    }
+
+    va_end(args);
+}
+
+
+void print_hex(unsigned int num) {
+    // Buffer to hold the hexadecimal representation
+    char buffer[9]; // 8 hex digits + null terminator
+    buffer[8] = '\0'; // Null-terminate the string
+
+    for (int i = 7; i >= 0; i--) {
+        int digit = num & 0xF; // Get the last 4 bits
+        buffer[i] = (digit < 10) ? (digit + '0') : (digit - 10 + 'A'); // Convert to hex character
+        num >>= 4; // Shift right by 4 bits
+    }
+
+    // Print the buffer, skipping leading zeros
+    int leading_zero = 1;
+    for (int i = 0; i < 8; i++) {
+        if (buffer[i] != '0') {
+            leading_zero = 0; // Found a non-zero digit
+        }
+        if (!leading_zero) {
+            my_putchar(buffer[i]);
+        }
+    }
+    if (leading_zero) {
+        my_putchar('0'); // If all were zeros, print a single '0'
+    }
 }

kernel/print.h

@@ -2,5 +2,8 @@
 #define PRINT_H
 
 void print_string(const char *str);
+void my_printf(const char *format, ...);
+void print_hex(unsigned int num);
+void my_putchar(char ch);
 
 #endif

kernel/shell.c

@@ -1,16 +1,18 @@
 #include "shell.h"
 #include "keyboard.h"
 #include "terminal.h"
+#include "print.h"
 #include <stdio.h>
 #include <string.h>
+#include "string_utils.h"
 
 void execute(char *input) {
-    if (strcmp(input, "help") == 0) {
+    if (my_strcmp(input, "help") == 0) {
-        printf("Available commands: help, clear, exit\n");
+        my_printf("Available commands: help, clear, exit\n");
-    } else if (strcmp(input, "clear") == 0) {
+    } else if (my_strcmp(input, "clear") == 0) {
         terminal_clear();
     } else {
-        printf("Unknown command: %s\n", input);
+        my_printf("Unknown command: %s\n", input);
     }
 }
 
@@ -22,7 +24,7 @@ void shell_loop()
 
     while (1)
     {
-        printf("> ");
+        my_printf("> ");
         index = 0;
 
         while (1)
@@ -32,7 +34,7 @@ void shell_loop()
             if (c == '\n' || c == '\r')  // Enter key
             {
                 input[index] = '\0';
-                printf("\n");
+                my_printf("\n");
                 break;
             }
             else if (c == '\b' || c == 127) // Backspace
@@ -40,7 +42,7 @@ void shell_loop()
                 if (index > 0)
                 {
                     index--;
-                    printf("\b \b"); // Erase last char on screen
+                    my_printf("\b \b"); // Erase last char on screen
                 }
             }
             else
@@ -52,7 +54,7 @@ void shell_loop()
             }
         }
 
-        if (strcmp(input, "exit") == 0)
+        if (my_strcmp(input, "exit") == 0)
             break;
 
         execute(input);

kernel/string_utils.c

@@ -0,0 +1,80 @@
+#include "string_utils.h"
+#include <stddef.h>
+#include <stdarg.h>
+
+size_t my_strlen(const char *str) {
+    const char *s = str;
+    while (*s) s++;
+    return s - str;
+}
+
+// Forward declaration of my_itoa
+static size_t my_itoa(int value, char *str, size_t size);
+
+int my_vsnprintf(char *str, size_t size, const char *format, ...) {
+    va_list args;
+    va_start(args, format);
+    size_t written = 0; // Change to size_t
+
+    for (const char *p = format; *p != '\0' && written < size - 1; p++) {
+        if (*p == '%') {
+            p++;
+            if (*p == 's') {
+                const char *s = va_arg(args, const char *);
+                while (*s && written < size - 1) {
+                    str[written++] = *s++;
+                }
+            } else if (*p == 'd') {
+                // Handle integer formatting
+                written += my_itoa(va_arg(args, int), str + written, size - written);
+            } else {
+                // Handle other formats as needed
+                str[written++] = *p; // Just copy the character
+            }
+        } else {
+            str[written++] = *p;
+        }
+    }
+    str[written] = '\0'; // Null-terminate the string
+    va_end(args);
+    return written;
+}
+
+static size_t my_itoa(int value, char *str, size_t size) {
+    size_t written = 0; // Change to size_t
+    if (value < 0) {
+        if (written < size - 1) {
+            str[written++] = '-';
+        }
+        value = -value;
+    }
+    // Convert integer to string
+    int temp = value;
+    int digits = 0;
+    do {
+        digits++;
+        temp /= 10;
+    } while (temp);
+    
+    if (written + digits >= size) {
+        digits = size - written - 1; // Prevent overflow
+    }
+    
+    str += written + digits; // Move pointer to the end
+    *str-- = '\0'; // Null-terminate the string
+
+    do {
+        *str-- = (value % 10) + '0';
+        value /= 10;
+    } while (value && str >= str - digits);
+    
+    return written + digits; // Return total written characters
+}
+
+int my_strcmp(const char *str1, const char *str2) {
+    while (*str1 && (*str1 == *str2)) {
+        str1++;
+        str2++;
+    }
+    return *(unsigned char *)str1 - *(unsigned char *)str2;
+}

kernel/string_utils.h

@@ -0,0 +1,11 @@
+#ifndef STRING_UTILS_H
+#define STRING_UTILS_H
+
+#include <stddef.h>
+#include <stdarg.h> // Include for va_list and related macros
+
+size_t my_strlen(const char *str); // Renamed to avoid conflict
+int my_vsnprintf(char *str, size_t size, const char *format, ...); // Renamed to avoid conflict
+int my_strcmp(const char *str1, const char *str2);
+
+#endif // STRING_UTILS_H

kernel/syscalls.c

@@ -21,8 +21,7 @@ void syscall_handler(int code, va_list args) {
     }
 }
 
-void syscall(int code, ...)
+void syscall(int code, ...) {
-{
     va_list args;
     va_start(args, code);
     syscall_handler(code, args);

kernel/syscalls.h

@@ -1,6 +1,7 @@
 #ifndef SYSCALLS_H
 #define SYSCALLS_H
 
+#include <stdarg.h>
 // Syscall numbers
 typedef enum {
     SYSCALL_INIT = 0,
@@ -9,8 +10,7 @@ typedef enum {
 } syscall_code_t;
 
 // Syscall dispatcher
-void syscall_handler();
+void syscall_handler(int code, va_list args);
-
 // Syscall interface
 void syscall(int code, ...);
 

kernel/vga.c

@@ -1,9 +1,9 @@
 #include "vga.h"
 #include <stddef.h>
 #include <stdbool.h>
-#include <stdio.h>   // Include for vsnprintf
+#include <string.h>
-#include <string.h>  // Include for strlen
+#include <stdarg.h>
-#include <stdarg.h>  // Include for va_list, va_start, etc.
+#include "string_utils.h"
 
 void outb(uint16_t port, uint8_t value) {
     __asm__ volatile("outb %0, %1" : : "a"(value), "Nd"(port));
@@ -130,11 +130,11 @@ void vga_printf(const char* format, ...) {
     char buffer[256];  // Buffer to store the formatted string
     va_list args;
     va_start(args, format);
-    vsnprintf(buffer, sizeof(buffer), format, args);
+    my_vsnprintf(buffer, sizeof(buffer), format, args); // Use my_vsnprintf instead of vsnprintf
     va_end(args);
     
     // Now you can use the buffer with vga_write_string
-    vga_write_string(buffer, strlen(buffer));
+    vga_write_string(buffer, my_strlen(buffer)); // Use my_strlen instead of strlen
 }
 
 void vga_init(void) {