README.md

@@ -48,7 +48,7 @@ Once a task is completed, it should be checked off.
 - [x] Create a paging subsystem. It should allow drivers to allocate and deallocate pages at will.
 - [x] Create a memory allocator. This should provide the kernel with `malloc` and `free`. Internally, it should use the paging subsystem to ensure that the address it returns have actual RAM paged to them.
 - [x] Create an initial driver architecture, allowing different drivers included in the kernel to test whether they should load or not.
-- [ ] Create a VGA driver. On startup, some memory statistics should be displayed, as well as boot progress.
+- [x] Create a VGA driver. On startup, some memory statistics should be displayed, as well as boot progress.
 - [ ] Create subsystem for loading new processes in Ring 3.
 - [ ] Update the build script to generate a ramdisk containing any applications to run. This initial ramdisk is in CPIO format.
 - [ ] Write a VFS subsystem.

src/CMakeLists.txt

@@ -12,6 +12,7 @@ add_executable(kernel
     kmalloc.c
     string.c
     driver.c
+    vga.c
     interrupts.S
     kernel.c
 )

src/kernel.c

@@ -9,6 +9,7 @@
 #include "paging.h"
 #include "kmalloc.h"
 #include "driver.h"
+#include "vga.h"
 
 void offset_print(const char *str)
 {
@@ -71,6 +72,10 @@ void kernel_main(uint32_t magic, uint32_t addr) {
     init_drivers();
     offset_print("Drivers initialized\n");
 
+    /* Show memory statistics and boot progress on VGA */
+    vga_show_mem_stats();
+    vga_puts("Boot complete.\n\n");
+
     /* Test kmalloc/kfree */
     uint32_t *test_alloc = (uint32_t *)kmalloc(64);
     if (test_alloc) {

src/vga.c

@@ -0,0 +1,230 @@
+/**
+ * @file vga.c
+ * @brief VGA text-mode driver implementation.
+ *
+ * Drives the standard VGA text-mode framebuffer at 0xB8000. The buffer
+ * is an array of 80×25 16-bit values, where the low byte is the ASCII
+ * character and the high byte encodes foreground and background color.
+ *
+ * This driver registers itself via the REGISTER_DRIVER macro and is
+ * automatically discovered during boot.
+ */
+
+#include "vga.h"
+#include "driver.h"
+#include "port_io.h"
+#include "pmm.h"
+
+/** Base address of the VGA text-mode framebuffer. */
+#define VGA_BUFFER 0xB8000
+
+/** Pointer to the VGA framebuffer, treated as an array of uint16_t. */
+static uint16_t *vga_buffer = (uint16_t *)VGA_BUFFER;
+
+/** Current cursor row (0-based). */
+static uint8_t cursor_row = 0;
+
+/** Current cursor column (0-based). */
+static uint8_t cursor_col = 0;
+
+/** Current text attribute byte (foreground | background << 4). */
+static uint8_t text_attr = 0;
+
+/**
+ * Create a VGA entry (character + attribute) for the framebuffer.
+ *
+ * @param c    ASCII character.
+ * @param attr Color attribute byte.
+ * @return     16-bit VGA entry.
+ */
+static inline uint16_t vga_entry(char c, uint8_t attr) {
+    return (uint16_t)c | ((uint16_t)attr << 8);
+}
+
+/**
+ * Create a color attribute byte from foreground and background colors.
+ *
+ * @param fg Foreground color (0–15).
+ * @param bg Background color (0–15).
+ * @return   Attribute byte.
+ */
+static inline uint8_t vga_color(vga_color_t fg, vga_color_t bg) {
+    return (uint8_t)fg | ((uint8_t)bg << 4);
+}
+
+/**
+ * Update the hardware cursor position via VGA I/O ports.
+ */
+static void update_cursor(void) {
+    uint16_t pos = cursor_row * VGA_WIDTH + cursor_col;
+
+    outb(0x3D4, 0x0F);
+    outb(0x3D5, (uint8_t)(pos & 0xFF));
+    outb(0x3D4, 0x0E);
+    outb(0x3D5, (uint8_t)((pos >> 8) & 0xFF));
+}
+
+/**
+ * Scroll the screen up by one line.
+ *
+ * The top line is discarded, all other lines move up, and the bottom
+ * line is filled with spaces.
+ */
+static void scroll(void) {
+    /* Move all lines up by one */
+    for (int i = 0; i < (VGA_HEIGHT - 1) * VGA_WIDTH; i++) {
+        vga_buffer[i] = vga_buffer[i + VGA_WIDTH];
+    }
+
+    /* Clear the last line */
+    uint16_t blank = vga_entry(' ', text_attr);
+    for (int i = (VGA_HEIGHT - 1) * VGA_WIDTH; i < VGA_HEIGHT * VGA_WIDTH; i++) {
+        vga_buffer[i] = blank;
+    }
+
+    cursor_row = VGA_HEIGHT - 1;
+}
+
+void vga_clear(void) {
+    uint16_t blank = vga_entry(' ', text_attr);
+    for (int i = 0; i < VGA_WIDTH * VGA_HEIGHT; i++) {
+        vga_buffer[i] = blank;
+    }
+    cursor_row = 0;
+    cursor_col = 0;
+    update_cursor();
+}
+
+void vga_set_color(vga_color_t fg, vga_color_t bg) {
+    text_attr = vga_color(fg, bg);
+}
+
+void vga_putchar(char c) {
+    if (c == '\n') {
+        cursor_col = 0;
+        cursor_row++;
+    } else if (c == '\r') {
+        cursor_col = 0;
+    } else if (c == '\t') {
+        cursor_col = (cursor_col + 8) & ~7;
+        if (cursor_col >= VGA_WIDTH) {
+            cursor_col = 0;
+            cursor_row++;
+        }
+    } else if (c == '\b') {
+        if (cursor_col > 0) {
+            cursor_col--;
+            vga_buffer[cursor_row * VGA_WIDTH + cursor_col] = vga_entry(' ', text_attr);
+        }
+    } else {
+        vga_buffer[cursor_row * VGA_WIDTH + cursor_col] = vga_entry(c, text_attr);
+        cursor_col++;
+        if (cursor_col >= VGA_WIDTH) {
+            cursor_col = 0;
+            cursor_row++;
+        }
+    }
+
+    if (cursor_row >= VGA_HEIGHT) {
+        scroll();
+    }
+
+    update_cursor();
+}
+
+void vga_puts(const char *str) {
+    while (*str) {
+        vga_putchar(*str);
+        str++;
+    }
+}
+
+void vga_put_hex(uint32_t val) {
+    const char *hex = "0123456789ABCDEF";
+    vga_putchar('0');
+    vga_putchar('x');
+    for (int i = 28; i >= 0; i -= 4) {
+        vga_putchar(hex[(val >> i) & 0xF]);
+    }
+}
+
+void vga_put_dec(uint32_t val) {
+    if (val == 0) {
+        vga_putchar('0');
+        return;
+    }
+
+    char buf[12];
+    int pos = 0;
+    while (val > 0) {
+        buf[pos++] = '0' + (val % 10);
+        val /= 10;
+    }
+    /* Print in reverse */
+    while (pos > 0) {
+        vga_putchar(buf[--pos]);
+    }
+}
+
+void vga_show_mem_stats(void) {
+    uint32_t mem_kb = pmm_get_memory_size() + 1024; /* total including lower */
+
+    vga_set_color(VGA_LIGHT_CYAN, VGA_BLACK);
+    vga_puts("=== ClaudeOS Memory Statistics ===\n");
+
+    vga_set_color(VGA_WHITE, VGA_BLACK);
+    vga_puts("  Total RAM:    ");
+    vga_put_dec(mem_kb);
+    vga_puts(" KiB (");
+    vga_put_dec(mem_kb / 1024);
+    vga_puts(" MiB)\n");
+
+    vga_puts("  Kernel start: ");
+    extern uint32_t _kernel_start;
+    vga_put_hex((uint32_t)&_kernel_start);
+    vga_puts("\n");
+
+    vga_puts("  Kernel end:   ");
+    extern uint32_t _kernel_end;
+    vga_put_hex((uint32_t)&_kernel_end);
+    vga_puts("\n");
+
+    uint32_t kernel_size = (uint32_t)&_kernel_end - (uint32_t)&_kernel_start;
+    vga_puts("  Kernel size:  ");
+    vga_put_dec(kernel_size / 1024);
+    vga_puts(" KiB\n");
+
+    vga_set_color(VGA_LIGHT_CYAN, VGA_BLACK);
+    vga_puts("==================================\n");
+    vga_set_color(VGA_LIGHT_GREY, VGA_BLACK);
+}
+
+/* --- Driver registration --- */
+
+/**
+ * VGA probe: always succeeds since VGA text mode is always available
+ * on the target platform (i386).
+ */
+static driver_probe_result_t vga_probe(void) {
+    return DRIVER_PROBE_OK;
+}
+
+int vga_init(void) {
+    text_attr = vga_color(VGA_LIGHT_GREY, VGA_BLACK);
+    vga_clear();
+
+    vga_set_color(VGA_LIGHT_GREEN, VGA_BLACK);
+    vga_puts("ClaudeOS v0.1 booting...\n\n");
+    vga_set_color(VGA_LIGHT_GREY, VGA_BLACK);
+
+    return 0;
+}
+
+/** VGA driver descriptor. */
+static const driver_t vga_driver = {
+    .name  = "vga",
+    .probe = vga_probe,
+    .init  = vga_init,
+};
+
+REGISTER_DRIVER(vga_driver);

src/vga.h

@@ -0,0 +1,97 @@
+/**
+ * @file vga.h
+ * @brief VGA text-mode driver interface.
+ *
+ * Provides functions to write text to the VGA text-mode framebuffer
+ * (typically at 0xB8000). Supports an 80x25 character display with
+ * 16 foreground and 16 background colors.
+ */
+
+#ifndef VGA_H
+#define VGA_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+/** VGA color constants. */
+typedef enum {
+    VGA_BLACK         = 0,
+    VGA_BLUE          = 1,
+    VGA_GREEN         = 2,
+    VGA_CYAN          = 3,
+    VGA_RED           = 4,
+    VGA_MAGENTA       = 5,
+    VGA_BROWN         = 6,
+    VGA_LIGHT_GREY    = 7,
+    VGA_DARK_GREY     = 8,
+    VGA_LIGHT_BLUE    = 9,
+    VGA_LIGHT_GREEN   = 10,
+    VGA_LIGHT_CYAN    = 11,
+    VGA_LIGHT_RED     = 12,
+    VGA_LIGHT_MAGENTA = 13,
+    VGA_YELLOW        = 14,
+    VGA_WHITE         = 15,
+} vga_color_t;
+
+/** VGA screen dimensions. */
+#define VGA_WIDTH  80
+#define VGA_HEIGHT 25
+
+/**
+ * Initialize the VGA driver.
+ *
+ * Clears the screen and sets the default colors.
+ *
+ * @return 0 on success.
+ */
+int vga_init(void);
+
+/**
+ * Clear the VGA screen.
+ */
+void vga_clear(void);
+
+/**
+ * Set the foreground and background color for subsequent writes.
+ *
+ * @param fg Foreground color.
+ * @param bg Background color.
+ */
+void vga_set_color(vga_color_t fg, vga_color_t bg);
+
+/**
+ * Write a single character at the current cursor position.
+ *
+ * @param c Character to write.
+ */
+void vga_putchar(char c);
+
+/**
+ * Write a null-terminated string at the current cursor position.
+ *
+ * @param str String to write.
+ */
+void vga_puts(const char *str);
+
+/**
+ * Write a 32-bit value in hexadecimal to the VGA display.
+ *
+ * @param val Value to display.
+ */
+void vga_put_hex(uint32_t val);
+
+/**
+ * Write a 32-bit value in decimal to the VGA display.
+ *
+ * @param val Value to display.
+ */
+void vga_put_dec(uint32_t val);
+
+/**
+ * Display boot memory statistics on VGA.
+ *
+ * Shows detected memory, kernel size, and free pages.
+ */
+void vga_show_mem_stats(void);
+
+#endif /* VGA_H */