very basic vga, ata, serial drivers. start of fat and fs drivers

21 files changed, 633 insertions, 65 deletions

diff --git a/doc/internal/mem.txt b/doc/internal/mem.txt
index d3b7696..cc5d301 100644
--- a/doc/internal/mem.txt
+++ b/doc/internal/mem.txt
@@ -1,4 +1,8 @@
-0x0001.0000 - 0x0002.ffff: unused
+0x0001.0000 - 0x0002.5fff: unused
+0x0002.6000 - 0x0002.bfff: fat
+0x0002.c000 - 0x0002.ffff: file buffers
 0x0003.0000 - 0x0003.7fff: kernel
 0x0003.8000 - 0x0003.ffff: stack
-0x0004.0000 - 0x0007.ffff: unused
\ No newline at end of file
+0x0004.0000 - 0x0007.ffff: unused
+0x0008.0000 - 0x000d.9fff: ramd
+0x000d.a000 - 0xffff.ffff: unused
\ No newline at end of file
diff --git a/makefile b/makefile
index 0de951a..503fcca 100644
--- a/makefile
+++ b/makefile
@@ -1,20 +1,32 @@
-qemu: floppy
-	qemu-system-i386 out/floppy.img
-
-floppy: kernel boot
+disk: kernel boot
 	mkdir -p obj out
-	/sbin/mkfs.fat -C -R 17 -n "PORTLAND OS" obj/shadow.img 1440
+	/sbin/mkfs.fat -C -f 1 -F 12 -n "PORTLAND OS" -R 17 obj/shadow.img 8192
 	echo -n -e '\xeb\x3c' > obj/jmp.bin
 	dd if=obj/jmp.bin of=obj/shadow.img obs=2 conv=notrunc
 	dd if=out/boot.bin of=obj/shadow.img obs=1 seek=62 conv=notrunc
 	dd if=out/kernel.bin of=obj/shadow.img seek=1 conv=notrunc
-	mv obj/shadow.img out/floppy.img
+	mv obj/shadow.img out/disk.img
+
+vbox-image: disk
+	VBoxManage convertfromraw out/disk.img out/disk.vdi --uuid a61929ed-3bf2-45ff-b98a-44f87c616dba
+
+kdump: kernel
+	objdump -M intel -d obj/kernel.elf > out/kernel.dasm
 
+kgccargs = -m32 -ffreestanding -fno-asynchronous-unwind-tables
 kernel:
 	mkdir -p obj/kernel out
-	gcc -m32 -ffreestanding -c src/kernel/main.c -o obj/kernel/main.o
-	gcc -m32 -ffreestanding -c src/kernel/vga.c  -o obj/kernel/vga.o
-	ld -T src/kernel/link.ld obj/kernel/main.o obj/kernel/vga.o -o out/kernel.bin
+	gcc ${kgccargs} -c src/kernel/main.c   -o obj/kernel/main.o
+	gcc ${kgccargs} -c src/kernel/vga.c    -o obj/kernel/vga.o
+	gcc ${kgccargs} -c src/kernel/fat.c    -o obj/kernel/fat.o
+	gcc ${kgccargs} -c src/kernel/fs.c     -o obj/kernel/fs.o
+	gcc ${kgccargs} -c src/kernel/ata.c    -o obj/kernel/ata.o
+	gcc ${kgccargs} -c src/kernel/util.c   -o obj/kernel/utilc.o
+	gcc ${kgccargs} -c src/kernel/panic.c  -o obj/kernel/panic.o
+	gcc ${kgccargs} -c src/kernel/serial.c -o obj/kernel/serial.o
+	nasm -f elf32 src/kernel/util.asm -o obj/kernel/utila.o
+	ld -T src/kernel/link.ld obj/kernel/main.o obj/kernel/vga.o obj/kernel/fat.o obj/kernel/fs.o obj/kernel/ata.o obj/kernel/utilc.o obj/kernel/panic.o obj/kernel/utila.o obj/kernel/serial.o -o obj/kernel.elf
+	objcopy -O binary -j .entry -j .bin obj/kernel.elf out/kernel.bin
 
 boot:
 	mkdir -p out
diff --git a/src/boot.asm b/src/boot.asm
index fecf466..f8ff1c8 100644
--- a/src/boot.asm
+++ b/src/boot.asm
@@ -41,9 +41,14 @@ pmode:
   mov ds, ax
   mov ax, 0x18
   mov ss, ax
-  mov sp, 0x7ffc
+  mov esp, 0x00008000
+
+  xor ebp, ebp
+  call kernel_segment * 16
 
-  jmp kernel_segment * 16
+halt:
+  hlt
+  jmp halt
 
 gdt:
   dw .e - .t
diff --git a/src/kernel/ata.c b/src/kernel/ata.c
new file mode 100644
index 0000000..0e6cc4e
--- /dev/null
+++ b/src/kernel/ata.c
@@ -0,0 +1,113 @@
+#include <stdint.h>
+#include "panic.h"
+#include "util.h"
+#include "ata.h"
+
+enum {
+  AP_PRIMARY   = 0x01f0,
+  AP_SECONDARY = 0x0170,
+
+  AP_DATA  = 0x0,
+  AP_ERROR = 0x1,
+  AP_FEAT  = 0x1,
+  AP_COUNT = 0x2,
+  AP_SEC   = 0x3,
+  AP_CYL_L = 0x4,
+  AP_CYL_H = 0x5,
+  AP_HD_DR = 0x6,
+  AP_LBA0  = 0x3,
+  AP_LBA1  = 0x4,
+  AP_LBA2  = 0x5,
+  AP_L3_DR = 0x6,
+  AP_STAT  = 0x7,
+  AP_CMD   = 0x7,
+
+  APC_STAT = 0x0206,
+  APC_CTRL = 0x0206,
+  APC_ADDR = 0x0207
+};
+
+enum {
+  ADR_BASE  = 0xa0,
+  ADR_CASCD = 0x10,
+  ADR_LBA   = 0x40
+};
+
+enum {
+  AS_ERROR   = 0x01,
+  AS_INDEX   = 0x02,
+  AS_CORRECT = 0x04,
+  AS_DREADY  = 0x08,
+  AS_SERVICE = 0x10,
+  AS_FAULT   = 0x20,
+  AS_READY   = 0x40,
+  AS_BUSY    = 0x80
+};
+
+enum {
+  AC_READ  = 0x20,
+  AC_WRITE = 0x30,
+  AC_FLUSH = 0xe7
+};
+
+void ata_ldelay() {
+  uint16_t i = 65535;
+  while (i--)
+    ;
+}
+
+void ata_sdelay() {
+  uint8_t i = 255;
+  while (i--)
+    ;
+}
+
+void ata_dpoll() {
+  uint8_t s;
+  while ((s = inb(AP_PRIMARY | AP_STAT) & (AS_BUSY | AS_DREADY)) != AS_DREADY)
+    if (s & (AS_ERROR | AS_FAULT))
+      panic("ATA controller error or fault.");
+}
+
+uint8_t read_sectors(uint16_t start, uint8_t count, void *buffer) {
+  outb(AP_PRIMARY | AP_L3_DR, ADR_BASE | ADR_LBA);
+  outb(AP_PRIMARY | AP_LBA2, 0);
+  outb(AP_PRIMARY | AP_LBA1, start >> 8);
+  outb(AP_PRIMARY | AP_LBA0, start & 0xff);
+  outb(AP_PRIMARY | AP_COUNT, count);
+  outb(AP_PRIMARY | AP_CMD, AC_READ);
+  uint8_t i = count - 1;
+  uint16_t *ptr = buffer;
+  do {
+    ata_dpoll();
+    uint8_t j = 255;
+    do
+      *(ptr++) = inw(AP_PRIMARY | AP_DATA);
+    while (j--);
+    ata_ldelay();
+  } while (i--);
+  return count;//TODO: return early if necessary
+}
+
+uint8_t write_sectors(uint16_t start, uint8_t count, void *buffer) {
+  outb(AP_PRIMARY | AP_L3_DR, ADR_BASE | ADR_LBA);
+  outb(AP_PRIMARY | AP_LBA2, 0);
+  outb(AP_PRIMARY | AP_LBA1, start >> 8);
+  outb(AP_PRIMARY | AP_LBA0, start & 0xff);
+  outb(AP_PRIMARY | AP_COUNT, count);
+  outb(AP_PRIMARY | AP_CMD, AC_WRITE);
+  uint8_t i = 0;
+  uint16_t *ptr = buffer;
+  do {
+    ata_dpoll();
+    uint8_t j = 0;
+    do {
+      ata_sdelay();
+      outw(AP_PRIMARY | AP_DATA, *(ptr++));
+    }
+    while (++j);
+    ata_ldelay();
+  } while (++i != count);
+  outb(AP_PRIMARY | AP_CMD, AC_FLUSH);
+  return count;//TODO: return early if necessary
+}
\ No newline at end of file
diff --git a/src/kernel/ata.h b/src/kernel/ata.h
new file mode 100644
index 0000000..605f991
--- /dev/null
+++ b/src/kernel/ata.h
@@ -0,0 +1,6 @@
+#include <stdint.h>
+
+void init_ata();
+
+uint8_t read_sectors(uint16_t start, uint8_t count, void *buffer);
+uint8_t write_sectors(uint16_t start, uint8_t count, void *buffer);
\ No newline at end of file
diff --git a/src/kernel/fat.c b/src/kernel/fat.c
new file mode 100644
index 0000000..00fa61f
--- /dev/null
+++ b/src/kernel/fat.c
@@ -0,0 +1,21 @@
+#include "fat.h"
+#include "ata.h"
+#include "panic.h"
+
+void load_fat() {
+  read_sectors(FAT_INFO->reserved_sectors, FAT_INFO->sectors_per_fat, FAT);
+}
+
+uint16_t get_cluster(uint16_t n) {
+  uint32_t t = *(uint32_t *)(FAT + (n / 2) * 3);
+  return (n % 2 ? (t >> 12) : t) & 0xfff;
+}
+
+void set_cluster(uint16_t n, uint16_t v) {
+  uint32_t *t = (uint32_t *)(FAT + (n / 2) * 3);
+  *t = (*t & (n % 2 ? 0xff000fff : 0xfffff000)) | (n % 2 ? v << 12 : v);
+}
+
+uint16_t get_start_cluster(uint8_t *path) {
+  panic("Not implemented (get_start_cluster).");
+}
\ No newline at end of file
diff --git a/src/kernel/fat.h b/src/kernel/fat.h
index e7aa956..0fbf59f 100644
--- a/src/kernel/fat.h
+++ b/src/kernel/fat.h
@@ -4,12 +4,12 @@
 
 struct fat_info {
   uint8_t  oem[8];
-  uint16_t bytes_per_sector;
-  uint8_t  sectors_per_cluster;
+  uint16_t bytes_per_sector;//Assumed to be 512
+  uint8_t  sectors_per_cluster;//Assumed to be 1
   uint16_t reserved_sectors;
-  uint8_t  fats;
+  uint8_t  fats;//Assumed to be 1
   uint16_t root_entries;
-  uint16_t sectors;
+  uint16_t sectors;//Assumed not to be 0
   uint8_t  media_type;
   uint16_t sectors_per_fat;
   uint16_t sectors_per_track;
@@ -22,4 +22,11 @@ struct fat_info {
   uint32_t volume_id;
   uint8_t  label[11];
   uint8_t  fs_type[8];
-} __attribute__ ((packed));
\ No newline at end of file
+} __attribute__ ((packed));
+
+#define FAT ((void *)0x00026000)
+void load_fat();
+uint16_t get_cluster(uint16_t n);
+void set_cluster(uint16_t n, uint16_t v);
+
+uint16_t get_start_cluster(uint8_t *path);
\ No newline at end of file
diff --git a/src/kernel/fs.c b/src/kernel/fs.c
new file mode 100644
index 0000000..129e631
--- /dev/null
+++ b/src/kernel/fs.c
@@ -0,0 +1,82 @@
+#include <stdint.h>
+#include "fs.h"
+#include "ata.h"
+#include "fat.h"
+#include <stdbool.h>
+#include "panic.h"
+
+#define MAX_HANDLES 32
+#define FILE_BUFFER(h) ((void *)(0x0002be00 + (h << 9)))
+#define HANDLE(h) ((handles - 1)[h])
+#define HEAD(h) (FILE_BUFFER(h) + HANDLE(h).seek % 512)
+
+struct handle_info {
+  uint16_t start_cluster;
+  uint16_t seek;
+  uint16_t loaded_cluster;
+  bool dirty;
+};
+
+struct handle_info handles[MAX_HANDLES];
+
+void clear_fs_handles() {
+  struct handle_info *f = handles;
+  while (f < handles + MAX_HANDLES)
+    (f++)->start_cluster = 0;
+}
+
+fs_handle next_handle() {
+  fs_handle r = 0;
+  while (HANDLE(++r).start_cluster)
+    if (r == MAX_HANDLES)
+      return 0;
+  return r;
+}
+
+void write_buffer(fs_handle handle) {
+  HANDLE(handle).dirty = false;
+  panic("Not implemented (write_buffer).");
+}
+
+void read_buffer(fs_handle handle) {
+  if (HANDLE(handle).dirty)
+    write_buffer(handle);
+  HANDLE(handle).loaded_cluster = HANDLE(handle).seek >> 9;
+  panic("Not implemented (read_buffer).");
+}
+
+fs_handle fs_open(uint8_t *path) {
+  fs_handle next = next_handle();
+  if (!next)
+    return 0;
+  uint16_t s = get_start_cluster(path);
+  if (!s)
+    return 0;
+  HANDLE(next).start_cluster = s;
+  HANDLE(next).seek = 0;
+  HANDLE(next).dirty = false;
+  read_buffer(next);
+  return next;
+}
+
+int16_t fs_seek(fs_handle handle, int16_t by) {
+  uint16_t old = HANDLE(handle).seek;
+  uint16_t to = -by > old ? 0 : old + by;
+  HANDLE(handle).seek = to;
+  if ((to ^ old) & 0xfe00)
+    read_buffer(handle);
+}
+
+uint16_t fs_read(fs_handle handle, uint16_t max, void *buffer) {
+  panic("Not implemented (fs_read).");
+}
+
+uint16_t fs_write(fs_handle handle, uint16_t max, void *buffer) {
+  panic("Not implemented (fs_write).");
+}
+
+void fs_close(fs_handle handle) {
+  if (HANDLE(handle).dirty)
+    write_buffer(handle);
+  HANDLE(handle).start_cluster = 0;
+}
\ No newline at end of file
diff --git a/src/kernel/fs.h b/src/kernel/fs.h
new file mode 100644
index 0000000..821d810
--- /dev/null
+++ b/src/kernel/fs.h
@@ -0,0 +1,10 @@
+#include <stdint.h>
+
+void clear_fs_handles();
+
+typedef uint8_t fs_handle;
+fs_handle fs_open(uint8_t *path);
+int16_t fs_seek(fs_handle handle, int16_t by);
+uint16_t fs_read(fs_handle handle, uint16_t max, void *buffer);
+uint16_t fs_write(fs_handle handle, uint16_t max, void *buffer);
+void fs_close(fs_handle handle);
\ No newline at end of file
diff --git a/src/kernel/link.ld b/src/kernel/link.ld
index 1fcff40..1fc64fd 100644
--- a/src/kernel/link.ld
+++ b/src/kernel/link.ld
@@ -1,4 +1,4 @@
-OUTPUT_FORMAT(binary)
+OUTPUT_FORMAT(elf32-i386)
 OUTPUT_ARCH(i386)
 
 SECTIONS {
@@ -10,6 +10,8 @@ SECTIONS {
     *(.text)
     *(.rodata)
     *(.data)
+  }
+  /DISCARD/ : {
     *(.bss)
   }
 }
\ No newline at end of file
diff --git a/src/kernel/main.c b/src/kernel/main.c
index dbeb11b..877a276 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -1,14 +1,36 @@
 #include <stdint.h>
 #include "vga.h"
 #include "fat.h"
+#include "fs.h"
+#include "ata.h"
+#include "panic.h"
+#include "serial.h"
+#include "util.h"
+
+uint8_t nbuf[11];
 
 void main() {
   vga_blank();
-  vga_printsz("In kernel-land\n\nDisk label: ");
+  vga_printsz("Initializing drivers...");
+  sinit();
+  vga_printsz("\n  Serial ready.");
+  load_fat();
+  clear_fs_handles();
+  vga_printsz("\n  File system ready.\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...");
+  u32_dec(FAT_INFO->sectors >> 1, nbuf);
+  vga_printsz(nbuf);
+  vga_printsz("k\n\nFAT start:\n");
+  nbuf[3] = 0;
+  for (uint8_t r = 0; r < 192; r += 24) {
+    for (uint8_t c = 0; c < 24; ++c) {
+      u8_hex(*(uint8_t *)(FAT + r + c), nbuf);
+      nbuf[2] = ' ';
+      vga_printsz(nbuf);
+    }
+    vga_printch('\n');
+  }
   while (1)
     asm ("hlt");
 }
\ No newline at end of file
diff --git a/src/kernel/panic.c b/src/kernel/panic.c
new file mode 100644
index 0000000..49d4a27
--- /dev/null
+++ b/src/kernel/panic.c
@@ -0,0 +1,31 @@
+#include <stdint.h>
+#include "vga.h"
+#include "serial.h"
+#include "util.h"
+
+void halt() {
+  while (1)
+    asm volatile ("hlt");
+}
+
+void panic(uint8_t *message) {
+  uint32_t frame;
+  asm (
+    "movl %%ebp, %0"
+  : "=r" (frame));
+  vga_set_color(0x4f);
+  vga_blank();
+  vga_printsz("Kernel panic: ");
+  vga_printsz(message);
+  vga_printsz("\n\nStack trace:");
+  uint8_t stb[6];
+  while (1) {
+    uint32_t ip = *(uint32_t *)(0x38000 + frame + 4);
+    if (!ip)
+      halt();
+    vga_printsz("\n  0x");
+    u16_hex(ip - 0x30000 - 5, stb);//assumes would return to just after a call instruction
+    vga_printsz(stb);
+    frame = *(uint32_t *)(0x38000 + frame);
+  }
+}
\ No newline at end of file
diff --git a/src/kernel/panic.h b/src/kernel/panic.h
new file mode 100644
index 0000000..8972814
--- /dev/null
+++ b/src/kernel/panic.h
@@ -0,0 +1,4 @@
+#include <stdint.h>
+
+void panic(uint8_t *message) __attribute__ ((noreturn));
+void halt() __attribute__ ((noreturn));
\ No newline at end of file
diff --git a/src/kernel/serial.c b/src/kernel/serial.c
new file mode 100644
index 0000000..b88c7ec
--- /dev/null
+++ b/src/kernel/serial.c
@@ -0,0 +1,100 @@
+#include <stdint.h>
+#include <stdbool.h>
+#include "util.h"
+
+enum {
+  CP_DATA    = 0x0,
+  CP_INT     = 0x1,
+  CP_FIFO    = 0x2,
+  CP_LINE    = 0x3,
+  CP_MODEM   = 0x4,
+  CP_LINE_S  = 0x5,
+  CP_MODEM_S = 0x6,
+
+  CP_DIVLOW  = 0x0,
+  CP_DIVHIGH = 0x1,
+
+  CP_1 = 0x03f8,
+  CP_2 = 0x02f8,
+  CP_3 = 0x03e8,
+  CP_4 = 0x02e8
+};
+
+enum {
+  CL_BAUD  = 0x80,
+
+  CL_PODD  = 0x08,
+  CL_PEVEN = 0x0c,
+  CL_PON   = 0x18,
+  CL_POFF  = 0x1c,
+
+  CL_LSTOP = 0x4,
+
+  CL_5BIT  = 0x0,
+  CL_6BIT  = 0x1,
+  CL_7BIT  = 0x2,
+  CL_8BIT  = 0x3
+};
+
+enum {
+  CLS_B_ERR = 0x80,
+  CLS_IDLE  = 0x40,
+  CLS_WRITE = 0x20,
+  CLS_BREAK = 0x10,
+  CLS_FRAME = 0x08,
+  CLS_PAR   = 0x04,
+  CLS_OVER  = 0x02,
+  CLS_READ  = 0x01
+};
+
+bool error;
+#define SERIAL_SPIN_LIMIT 65535
+
+bool serr() {
+  return error;
+}
+
+void sinit() {
+  error = false;
+  outb(CP_1 | CP_INT, 0);
+  outb(CP_1 | CP_LINE, CL_BAUD);
+  outb(CP_1 | CP_DIVLOW, 0x03);//38400
+  outb(CP_1 | CP_DIVHIGH, 0x00);//baud
+  outb(CP_1 | CP_LINE, CL_8BIT);
+  outb(CP_1 | CP_FIFO, 0xc7);//?
+}
+
+void sout(uint8_t b) {
+  if (error)
+    return;
+  uint16_t s = SERIAL_SPIN_LIMIT;
+  while (!(inb(CP_1 | CP_LINE_S) & CLS_WRITE))
+    if (!--s) {
+      error = true;
+      return;
+    }
+  outb(CP_1 | CP_DATA, b);
+}
+
+void soutsz(uint8_t *s) {
+  while (*s)
+    sout(*(s++));
+}
+
+void soutsn(uint8_t *s, uint8_t n) {
+  while (n--)
+    sout(*(s++));
+}
+
+uint8_t sin() {
+  if (error)
+    return 0;
+  while (!(inb(CP_1 | CP_LINE_S) & CLS_READ))
+    ;//spin
+  return inb(CP_1 | CP_DATA);
+}
+
+void sinsn(uint8_t *s, uint8_t n) {
+  while (n--)
+    *(s++) = sin();
+}
\ No newline at end of file
diff --git a/src/kernel/serial.h b/src/kernel/serial.h
new file mode 100644
index 0000000..f0465d0
--- /dev/null
+++ b/src/kernel/serial.h
@@ -0,0 +1,10 @@
+#include <stdint.h>
+#include <stdbool.h>
+
+bool serr();
+void sinit();
+void sout(uint8_t b);
+void soutsz(uint8_t *s);
+void soutsn(uint8_t *s, uint8_t n);
+uint8_t sin();
+void sinsn(uint8_t *s, uint8_t n);
\ No newline at end of file
diff --git a/src/kernel/util.asm b/src/kernel/util.asm
new file mode 100644
index 0000000..acac17f
--- /dev/null
+++ b/src/kernel/util.asm
@@ -0,0 +1,37 @@
+bits 32
+
+global outb
+global inb
+global outw
+global inw
+
+section .text
+outb:
+  ;word [esp + 4] = port
+  ;byte [esp + 8] = value
+  mov dx, word [esp + 4]
+  mov al, byte [esp + 8]
+  out dx, al
+  ret
+
+inb:
+  ;word [esp + 4] = port
+  ;al out = value
+  mov dx, word [esp + 4]
+  in al, dx
+  ret
+
+outw:
+  ;word [esp + 4] = port
+  ;word [esp + 8] = value
+  mov dx, word [esp + 4]
+  mov ax, word [esp + 8]
+  out dx, ax
+  ret
+
+inw:
+  ;word [esp + 4] = port
+  ;ax out = value
+  mov dx, word [esp + 4]
+  in ax, dx
+  ret
\ No newline at end of file
diff --git a/src/kernel/util.c b/src/kernel/util.c
new file mode 100644
index 0000000..df6e7d8
--- /dev/null
+++ b/src/kernel/util.c
@@ -0,0 +1,100 @@
+#include <stdint.h>
+#include "panic.h"
+#include <stdbool.h>
+
+void memcpy(void *from, void *to, uint32_t n) {
+  panic("Not implemented (memcpy).");
+}
+
+void u32_dec(uint32_t n, uint8_t *b) {
+  if (!n) {
+    *(uint16_t *)b = '0';
+    return;
+  }
+  bool zero = false;
+  for (uint32_t m = 1000000000; m; m /= 10) {
+    uint8_t d = (n / m) % 10;
+    if (zero)
+      *(b++) = d + '0';
+    else if (d) {
+      zero = true;
+      *(b++) = d + '0';
+    }
+  }
+  *b = 0;
+}
+
+void u16_dec(uint16_t n, uint8_t *b) {
+  if (!n) {
+    *(uint16_t *)b = '0';
+    return;
+  }
+  bool zero = false;
+  for (uint32_t m = 10000; m; m /= 10) {
+    uint8_t d = (n / m) % 10;
+    if (zero)
+      *(b++) = d + '0';
+    else if (d) {
+      zero = true;
+      *(b++) = d + '0';
+    }
+  }
+  *b = 0;
+}
+
+void u8_dec(uint8_t n, uint8_t *b) {
+  if (!n) {
+    *(uint16_t *)b = '0';
+    return;
+  }
+  bool zero = false;
+  for (uint32_t m = 100; m; m /= 10) {
+    uint8_t d = (n / m) % 10;
+    if (zero)
+      *(b++) = d + '0';
+    else if (d) {
+      zero = true;
+      *(b++) = d + '0';
+    }
+  }
+  *b = 0;
+}
+
+void u32_hex(uint32_t n, uint8_t *b) {
+  uint8_t m = 28;
+  while (1) {
+    uint8_t d = (n >> m) & 0xf;
+    *(b++) = d >= 10 ? 'a' + d - 10 : '0' + d;
+    if (!m) {
+      *b = 0;
+      return;
+    }
+    m -= 4;
+  }
+}
+
+void u16_hex(uint16_t n, uint8_t *b) {
+  uint8_t m = 12;
+  while (1) {
+    uint8_t d = (n >> m) & 0xf;
+    *(b++) = d >= 10 ? 'a' + d - 10 : '0' + d;
+    if (!m) {
+      *b = 0;
+      return;
+    }
+    m -= 4;
+  }
+}
+
+void u8_hex(uint8_t n, uint8_t *b) {
+  uint8_t m = 4;
+  while (1) {
+    uint8_t d = (n >> m) & 0xf;
+    *(b++) = d >= 10 ? 'a' + d - 10 : '0' + d;
+    if (!m) {
+      *b = 0;
+      return;
+    }
+    m -= 4;
+  }
+}
\ No newline at end of file
diff --git a/src/kernel/util.h b/src/kernel/util.h
new file mode 100644
index 0000000..08b3e4a
--- /dev/null
+++ b/src/kernel/util.h
@@ -0,0 +1,13 @@
+#include <stdint.h>
+
+void memcpy(void *from, void *to, uint32_t n);
+void outb(uint16_t port, uint8_t value);
+uint8_t inb(uint16_t port);
+void outw(uint16_t port, uint16_t value);
+uint16_t inw(uint16_t port);
+void u32_dec(uint32_t n, uint8_t *b);
+void u16_dec(uint16_t n, uint8_t *b);
+void u8_dec(uint8_t n, uint8_t *b);
+void u32_hex(uint32_t n, uint8_t *b);
+void u16_hex(uint16_t n, uint8_t *b);
+void u8_hex(uint8_t n, uint8_t *b);
\ No newline at end of file
diff --git a/src/kernel/vga.c b/src/kernel/vga.c
index 8e438a8..c387b22 100644
--- a/src/kernel/vga.c
+++ b/src/kernel/vga.c
@@ -1,6 +1,12 @@
 #include <stdint.h>
 #include <stdbool.h>
 
+#define VGA_COM_MIRROR
+
+#ifdef VGA_COM_MIRROR
+#include "serial.h"
+#endif
+
 #define VGA_COLUMNS 80
 #define VGA_LINES 25
 #define VGA_START (uint16_t *)0x000b8000
@@ -8,11 +14,18 @@
 uint16_t *cursor = VGA_START;
 uint16_t color = 0x1f00;
 
+void vga_set_color(uint8_t new_color) {
+  color = new_color << 8;
+}
+
 void vga_scroll() {
   cursor = VGA_START;
 }
 
 void vga_blank() {
+#ifdef VGA_COM_MIRROR
+  soutsz("\r\n\r\n<CLEAR>\r\n\r\n");
+#endif
   uint32_t f = (color << 16) | color | 0x00200020;
   uint32_t *p = (uint32_t *)VGA_START;
   while (p < (uint32_t *)VGA_END)
@@ -22,10 +35,16 @@ void vga_blank() {
 
 void vga_printch(uint8_t ch) {
   if (ch == '\n') {
+#ifdef VGA_COM_MIRROR
+    soutsz("\r\n");
+#endif
     if ((cursor = cursor - (cursor - VGA_START) % VGA_COLUMNS + VGA_COLUMNS) == VGA_END)
       vga_scroll();
     return;
   }
+#ifdef VGA_COM_MIRROR
+  sout(ch);
+#endif
   *(cursor++) = color | ch;
   if (cursor == VGA_END)
     vga_scroll();
@@ -39,43 +58,4 @@ void vga_printsz(uint8_t *sz) {
 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');
-    }
-  }
 }
\ No newline at end of file
diff --git a/src/kernel/vga.h b/src/kernel/vga.h
index 95c6335..1e041df 100644
--- a/src/kernel/vga.h
+++ b/src/kernel/vga.h
@@ -1,10 +1,8 @@
 #include <stdint.h>
 
+void vga_set_color(uint8_t color);
 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);
\ No newline at end of file
+void vga_printsn(uint8_t *sn, uint8_t n);
\ No newline at end of file
diff --git a/src/kernel/vga.inc b/src/kernel/vga.inc
new file mode 100644
index 0000000..c7244e1
--- /dev/null
+++ b/src/kernel/vga.inc
@@ -0,0 +1,11 @@
+extern vga_set_color
+extern vga_blank
+extern vga_scroll
+extern vga_printch
+extern vga_printsz
+extern vga_printsn
+extern vga_printu32
+extern vga_printu16
+extern vga_printu8
+extern vga_printu32h
+extern vga_printu8h
\ No newline at end of file