small stub with fat info

makefile

@@ -1,3 +1,6 @@
+qemu: floppy
+	qemu-system-i386 out/floppy.img
+
 floppy: kernel boot
 	mkdir -p obj out
 	/sbin/mkfs.fat -C -R 17 -n "PORTLAND OS" obj/shadow.img 1440

src/boot.asm

@@ -12,6 +12,10 @@ kernel_segment equ 0x3000
   mov ss, ax
   mov sp, 0x7ffc
 
+  mov ah, 0x01
+  mov ch, 0x3f
+  int 0x10
+
   mov ax, kernel_segment
   mov es, ax
   mov ax, 0x0200 + kernel_sectors

src/kernel/fat.h

@@ -0,0 +1,25 @@
+#include <stdint.h>
+
+#define FAT_INFO ((struct fat_info *)0x7c03)
+
+struct fat_info {
+  uint8_t  oem[8];
+  uint16_t bytes_per_sector;
+  uint8_t  sectors_per_cluster;
+  uint16_t reserved_sectors;
+  uint8_t  fats;
+  uint16_t root_entries;
+  uint16_t sectors;
+  uint8_t  media_type;
+  uint16_t sectors_per_fat;
+  uint16_t sectors_per_track;
+  uint16_t heads;
+  uint32_t hidden_sectors;
+  uint32_t sectors_long;
+  uint8_t  drive_number;
+  uint8_t  reserved;
+  uint8_t  ext_boot_marker;
+  uint32_t volume_id;
+  uint8_t  label[11];
+  uint8_t  fs_type[8];
+} __attribute__ ((packed));

src/kernel/main.c

@@ -1,7 +1,14 @@
 #include <stdint.h>
 #include "vga.h"
+#include "fat.h"
 
 void main() {
+  vga_blank();
+  vga_printsz("In kernel-land\n\nDisk label: ");
+  vga_printsn(FAT_INFO->label, 11);
+  vga_printsz("\nDisk size:  ");
+  vga_printu32((FAT_INFO->sectors * FAT_INFO->bytes_per_sector) >> 10);
+  vga_printsz("k\n\nHalting...");
   while (1)
-    vga_printsz("Hello! ");
+    asm ("hlt");
 }

src/kernel/vga.c

@@ -1,14 +1,81 @@
 #include <stdint.h>
+#include <stdbool.h>
 
+#define VGA_COLUMNS 80
+#define VGA_LINES 25
 #define VGA_START (uint16_t *)0x000b8000
-#define VGA_END (VGA_START + 80 * 25)
+#define VGA_END (VGA_START + VGA_COLUMNS * VGA_LINES)
 uint16_t *cursor = VGA_START;
 uint16_t color = 0x1f00;
 
+void vga_scroll() {
+  cursor = VGA_START;
+}
+
+void vga_blank() {
+  uint32_t f = (color << 16) | color | 0x00200020;
+  uint32_t *p = (uint32_t *)VGA_START;
+  while (p < (uint32_t *)VGA_END)
+    *(p++) = f;
+  cursor = VGA_START;
+}
+
+void vga_printch(uint8_t ch) {
+  if (ch == '\n') {
+    if ((cursor = cursor - (cursor - VGA_START) % VGA_COLUMNS + VGA_COLUMNS) == VGA_END)
+      vga_scroll();
+    return;
+  }
+  *(cursor++) = color | ch;
+  if (cursor == VGA_END)
+    vga_scroll();
+}
+
 void vga_printsz(uint8_t *sz) {
-  while (*sz) {
+  while (*sz)
-    *(cursor++) = color | *(sz++);
+    vga_printch(*(sz++));
-    if (cursor == VGA_END)
+}
-      cursor = VGA_START;
+
+void vga_printsn(uint8_t *sn, uint8_t n) {
+  while (n--)
+    vga_printch(*(sn++));
+}
+
+void vga_printu32(uint32_t n) {
+  bool zero = false;
+  for (uint32_t m = 1000000000; m; m /= 10) {
+    uint8_t d = (n / m) % 10;
+    if (zero)
+      vga_printch(d + '0');
+    else if (d) {
+      zero = true;
+      vga_printch(d + '0');
+    }
+  }
+}
+
+void vga_printu16(uint16_t n) {
+  bool zero = false;
+  for (uint16_t m = 10000; m; m /= 10) {
+    uint8_t d = (n / m) % 10;
+    if (zero)
+      vga_printch(d + '0');
+    else if (d) {
+      zero = true;
+      vga_printch(d + '0');
+    }
+  }
+}
+
+void vga_printu8(uint8_t n) {
+  bool zero = false;
+  for (uint8_t m = 100; m; m /= 10) {
+    uint8_t d = (n / m) % 10;
+    if (zero)
+      vga_printch(d + '0');
+    else if (d) {
+      zero = true;
+      vga_printch(d + '0');
+    }
   }
 }

src/kernel/vga.h

@@ -1,3 +1,10 @@
 #include <stdint.h>
 
-void vga_printsz(uint8_t *sz);
+void vga_blank();
+void vga_scroll();
+void vga_printch(uint8_t ch);
+void vga_printsz(uint8_t *sz);
+void vga_printsn(uint8_t *sn, uint8_t n);
+void vga_printu32(uint32_t n);
+void vga_printu16(uint16_t n);
+void vga_printu8(uint8_t n);