kernel: Add RSOD(red screen of death)

This is not useful since 99% of the time I will have access to the
serial output. But it does look cool.

9 files changed, 227 insertions, 4 deletions

diff --git a/kernel/Makefile b/kernel/Makefile
index e9ef843..55a1ae6 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -1,6 +1,6 @@
 CC="i686-sb-gcc"
 AS="i686-sb-as"
-OBJ = arch/i386/boot.o init/kernel.o cpu/gdt.o cpu/reload_gdt.o cpu/idt.o cpu/io.o libc/stdio/print.o drivers/keyboard.o log.o drivers/pit.o libc/string/memcpy.o libc/string/strlen.o libc/string/memcmp.o drivers/ata.o libc/string/memset.o cpu/syscall.o  read_eip.o libc/exit/assert.o process.o libc/string/strcpy.o arch/i386/mmu.o kmalloc.o fs/ext2.o fs/vfs.o fs/devfs.o cpu/spinlock.o random.o libc/string/strcmp.o crypto/ChaCha20/chacha20.o crypto/SHA1/sha1.o fs/tmpfs.o libc/string/isequal.o drivers/pst.o kubsan.o drivers/serial.o socket.o poll.o fs/fifo.o hashmap/hashmap.o fs/shm.o elf.o ksbrk.o sched/scheduler.o libc/string/copy.o drivers/mouse.o libc/string/strlcpy.o libc/string/strcat.o drivers/vbe.o drivers/pci.o drivers/rtl8139.o network/ethernet.o network/arp.o network/bytes.o network/ipv4.o network/udp.o math.o signal.o network/tcp.o drivers/ahci.o crypto/xoshiro256plusplus/xoshiro256plusplus.o arch/i386/interrupts.o cpu/isr.o lib/stack.o lib/buffered_write.o lib/list.o cpu/arch_inst.o cpu/int_syscall.o lib/ringbuffer.o lib/relist.o arch/i386/tsc.o arch/i386/asm_tsc.o drivers/cmos.o timer.o queue.o
+OBJ = arch/i386/boot.o init/kernel.o cpu/gdt.o cpu/reload_gdt.o cpu/idt.o cpu/io.o libc/stdio/print.o drivers/keyboard.o log.o drivers/pit.o libc/string/memcpy.o libc/string/strlen.o libc/string/memcmp.o drivers/ata.o libc/string/memset.o cpu/syscall.o  read_eip.o libc/exit/assert.o process.o libc/string/strcpy.o arch/i386/mmu.o kmalloc.o fs/ext2.o fs/vfs.o fs/devfs.o cpu/spinlock.o random.o libc/string/strcmp.o crypto/ChaCha20/chacha20.o crypto/SHA1/sha1.o fs/tmpfs.o libc/string/isequal.o drivers/pst.o kubsan.o drivers/serial.o socket.o poll.o fs/fifo.o hashmap/hashmap.o fs/shm.o elf.o ksbrk.o sched/scheduler.o libc/string/copy.o drivers/mouse.o libc/string/strlcpy.o libc/string/strcat.o drivers/vbe.o drivers/pci.o drivers/rtl8139.o network/ethernet.o network/arp.o network/bytes.o network/ipv4.o network/udp.o math.o signal.o network/tcp.o drivers/ahci.o crypto/xoshiro256plusplus/xoshiro256plusplus.o arch/i386/interrupts.o cpu/isr.o lib/stack.o lib/buffered_write.o lib/list.o cpu/arch_inst.o cpu/int_syscall.o lib/ringbuffer.o lib/relist.o arch/i386/tsc.o arch/i386/asm_tsc.o drivers/cmos.o timer.o queue.o drivers/virtio.o fonts.o
 CFLAGS = -std=c99 -O0 -fsanitize=vla-bound,shift-exponent,pointer-overflow,shift,signed-integer-overflow,bounds -ggdb -ffreestanding -Wall -Wextra -Wno-int-conversion -Wno-unused-parameter -Werror -mgeneral-regs-only -Wimplicit-fallthrough -I./libc/include/ -I. -Wno-pointer-sign -DKERNEL
 LDFLAGS=
 INCLUDE=-I./includes/ -I../include/ -I./libc/include/
diff --git a/kernel/cpu/idt.c b/kernel/cpu/idt.c
index a7a93f6..474727f 100644
--- a/kernel/cpu/idt.c
+++ b/kernel/cpu/idt.c
@@ -1,6 +1,7 @@
 #include <cpu/arch_inst.h>
 #include <cpu/idt.h>
 #include <interrupts.h>
+#include <log.h>
 #include <sched/scheduler.h>
 #include <stdio.h>
 
@@ -50,6 +51,14 @@ __attribute__((no_caller_saved_registers)) void EOI(u8 irq) {
 }
 
 void general_protection_fault(reg_t *regs) {
+  int is_userspace = (regs->error_code & (1 << 2));
+  if (is_userspace) {
+    signal_process(current_task, SIGSEGV);
+    return;
+  }
+
+  log_enable_screen();
+
   klog(LOG_ERROR, "General Protetion Fault");
   kprintf(" Error Code: %x\n", regs->error_code);
   kprintf("Instruction Pointer: %x\n", regs->eip);
@@ -90,6 +99,8 @@ void page_fault(reg_t *regs) {
     return;
   }
 
+  log_enable_screen();
+
   klog(LOG_ERROR, "Page Fault");
   kprintf("CR2: %x\n", cr2);
   if (current_task) {
diff --git a/kernel/drivers/vbe.c b/kernel/drivers/vbe.c
index 05edfb8..9271867 100644
--- a/kernel/drivers/vbe.c
+++ b/kernel/drivers/vbe.c
@@ -1,5 +1,6 @@
 #include <assert.h>
 #include <drivers/vbe.h>
+#include <fonts.h>
 #include <fs/devfs.h>
 #include <fs/vfs.h>
 #include <mmu.h>
@@ -24,6 +25,43 @@ struct DISPLAY_INFO {
 
 struct DISPLAY_INFO vbe_info;
 
+#define place_pixel_pos(_p, _pos)                                              \
+  { *(u32 *)((u32 *)framebuffer + _pos) = _p; }
+
+static int get_bitmap_value(const unsigned char bitmap[], int i) {
+  int array_index = i / 8;
+  int byte_index = i % 8;
+  int rc = (bitmap[array_index] >> byte_index) & 0x1;
+  return rc;
+}
+
+void vbe_drawfont(u32 px, u32 py, const u8 c) {
+  u32 x, y;
+  x = px;
+  y = py;
+  if (px + 8 > framebuffer_width) {
+    return;
+  }
+  if (py + 8 > framebuffer_height) {
+    return;
+  }
+  const unsigned char *bitmap = font8x8_basic[c];
+  for (int i = 0; i < 8 * 8; i++) {
+    u32 pos = x + y * framebuffer_width;
+    if (get_bitmap_value(bitmap, i)) {
+      place_pixel_pos(0xFFFFFF, pos);
+    }
+    x++;
+    if (x >= 8 + px) {
+      y++;
+      x = px;
+    }
+    if (y > py + 8) {
+      break;
+    }
+  }
+}
+
 int display_driver_init(multiboot_info_t *mbi) {
   assert(CHECK_FLAG(mbi->flags, 12));
   framebuffer_width = mbi->framebuffer_width;
diff --git a/kernel/drivers/vbe.h b/kernel/drivers/vbe.h
index 369f384..c0f6c42 100644
--- a/kernel/drivers/vbe.h
+++ b/kernel/drivers/vbe.h
@@ -1,6 +1,8 @@
 #ifndef VBE_H
 #define VBE_H
 #include <multiboot.h>
+
+void vbe_drawfont(u32 px, u32 py, const u8 c);
 int display_driver_init(multiboot_info_t *mb);
 void display_driver_cross(multiboot_info_t *mbi);
 void add_vbe_device(void);
diff --git a/kernel/fonts.c b/kernel/fonts.c
new file mode 100644
index 0000000..7b89fd7
--- /dev/null
+++ b/kernel/fonts.c
@@ -0,0 +1,132 @@
+#include <fonts.h>
+
+const unsigned char font8x8_basic[128][8] = {
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0000 (nul)
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0001
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0002
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0003
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0004
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0005
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0006
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0007
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0008
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0009
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000A
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000B
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000C
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000D
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000E
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+000F
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0010
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0011
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0012
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0013
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0014
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0015
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0016
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0017
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0018
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0019
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001A
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001B
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001C
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001D
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001E
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+001F
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0020 (space)
+    {0x18, 0x3C, 0x3C, 0x18, 0x18, 0x00, 0x18, 0x00}, // U+0021 (!)
+    {0x36, 0x36, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0022 (")
+    {0x36, 0x36, 0x7F, 0x36, 0x7F, 0x36, 0x36, 0x00}, // U+0023 (#)
+    {0x0C, 0x3E, 0x03, 0x1E, 0x30, 0x1F, 0x0C, 0x00}, // U+0024 ($)
+    {0x00, 0x63, 0x33, 0x18, 0x0C, 0x66, 0x63, 0x00}, // U+0025 (%)
+    {0x1C, 0x36, 0x1C, 0x6E, 0x3B, 0x33, 0x6E, 0x00}, // U+0026 (&)
+    {0x06, 0x06, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0027 (')
+    {0x18, 0x0C, 0x06, 0x06, 0x06, 0x0C, 0x18, 0x00}, // U+0028 (()
+    {0x06, 0x0C, 0x18, 0x18, 0x18, 0x0C, 0x06, 0x00}, // U+0029 ())
+    {0x00, 0x66, 0x3C, 0xFF, 0x3C, 0x66, 0x00, 0x00}, // U+002A (*)
+    {0x00, 0x0C, 0x0C, 0x3F, 0x0C, 0x0C, 0x00, 0x00}, // U+002B (+)
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x0C, 0x0C, 0x06}, // U+002C (,)
+    {0x00, 0x00, 0x00, 0x3F, 0x00, 0x00, 0x00, 0x00}, // U+002D (-)
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x0C, 0x0C, 0x00}, // U+002E (.)
+    {0x60, 0x30, 0x18, 0x0C, 0x06, 0x03, 0x01, 0x00}, // U+002F (/)
+    {0x3E, 0x63, 0x73, 0x7B, 0x6F, 0x67, 0x3E, 0x00}, // U+0030 (0)
+    {0x0C, 0x0E, 0x0C, 0x0C, 0x0C, 0x0C, 0x3F, 0x00}, // U+0031 (1)
+    {0x1E, 0x33, 0x30, 0x1C, 0x06, 0x33, 0x3F, 0x00}, // U+0032 (2)
+    {0x1E, 0x33, 0x30, 0x1C, 0x30, 0x33, 0x1E, 0x00}, // U+0033 (3)
+    {0x38, 0x3C, 0x36, 0x33, 0x7F, 0x30, 0x78, 0x00}, // U+0034 (4)
+    {0x3F, 0x03, 0x1F, 0x30, 0x30, 0x33, 0x1E, 0x00}, // U+0035 (5)
+    {0x1C, 0x06, 0x03, 0x1F, 0x33, 0x33, 0x1E, 0x00}, // U+0036 (6)
+    {0x3F, 0x33, 0x30, 0x18, 0x0C, 0x0C, 0x0C, 0x00}, // U+0037 (7)
+    {0x1E, 0x33, 0x33, 0x1E, 0x33, 0x33, 0x1E, 0x00}, // U+0038 (8)
+    {0x1E, 0x33, 0x33, 0x3E, 0x30, 0x18, 0x0E, 0x00}, // U+0039 (9)
+    {0x00, 0x0C, 0x0C, 0x00, 0x00, 0x0C, 0x0C, 0x00}, // U+003A (:)
+    {0x00, 0x0C, 0x0C, 0x00, 0x00, 0x0C, 0x0C, 0x06}, // U+003B (;)
+    {0x18, 0x0C, 0x06, 0x03, 0x06, 0x0C, 0x18, 0x00}, // U+003C (<)
+    {0x00, 0x00, 0x3F, 0x00, 0x00, 0x3F, 0x00, 0x00}, // U+003D (=)
+    {0x06, 0x0C, 0x18, 0x30, 0x18, 0x0C, 0x06, 0x00}, // U+003E (>)
+    {0x1E, 0x33, 0x30, 0x18, 0x0C, 0x00, 0x0C, 0x00}, // U+003F (?)
+    {0x3E, 0x63, 0x7B, 0x7B, 0x7B, 0x03, 0x1E, 0x00}, // U+0040 (@)
+    {0x0C, 0x1E, 0x33, 0x33, 0x3F, 0x33, 0x33, 0x00}, // U+0041 (A)
+    {0x3F, 0x66, 0x66, 0x3E, 0x66, 0x66, 0x3F, 0x00}, // U+0042 (B)
+    {0x3C, 0x66, 0x03, 0x03, 0x03, 0x66, 0x3C, 0x00}, // U+0043 (C)
+    {0x1F, 0x36, 0x66, 0x66, 0x66, 0x36, 0x1F, 0x00}, // U+0044 (D)
+    {0x7F, 0x46, 0x16, 0x1E, 0x16, 0x46, 0x7F, 0x00}, // U+0045 (E)
+    {0x7F, 0x46, 0x16, 0x1E, 0x16, 0x06, 0x0F, 0x00}, // U+0046 (F)
+    {0x3C, 0x66, 0x03, 0x03, 0x73, 0x66, 0x7C, 0x00}, // U+0047 (G)
+    {0x33, 0x33, 0x33, 0x3F, 0x33, 0x33, 0x33, 0x00}, // U+0048 (H)
+    {0x1E, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+0049 (I)
+    {0x78, 0x30, 0x30, 0x30, 0x33, 0x33, 0x1E, 0x00}, // U+004A (J)
+    {0x67, 0x66, 0x36, 0x1E, 0x36, 0x66, 0x67, 0x00}, // U+004B (K)
+    {0x0F, 0x06, 0x06, 0x06, 0x46, 0x66, 0x7F, 0x00}, // U+004C (L)
+    {0x63, 0x77, 0x7F, 0x7F, 0x6B, 0x63, 0x63, 0x00}, // U+004D (M)
+    {0x63, 0x67, 0x6F, 0x7B, 0x73, 0x63, 0x63, 0x00}, // U+004E (N)
+    {0x1C, 0x36, 0x63, 0x63, 0x63, 0x36, 0x1C, 0x00}, // U+004F (O)
+    {0x3F, 0x66, 0x66, 0x3E, 0x06, 0x06, 0x0F, 0x00}, // U+0050 (P)
+    {0x1E, 0x33, 0x33, 0x33, 0x3B, 0x1E, 0x38, 0x00}, // U+0051 (Q)
+    {0x3F, 0x66, 0x66, 0x3E, 0x36, 0x66, 0x67, 0x00}, // U+0052 (R)
+    {0x1E, 0x33, 0x07, 0x0E, 0x38, 0x33, 0x1E, 0x00}, // U+0053 (S)
+    {0x3F, 0x2D, 0x0C, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+0054 (T)
+    {0x33, 0x33, 0x33, 0x33, 0x33, 0x33, 0x3F, 0x00}, // U+0055 (U)
+    {0x33, 0x33, 0x33, 0x33, 0x33, 0x1E, 0x0C, 0x00}, // U+0056 (V)
+    {0x63, 0x63, 0x63, 0x6B, 0x7F, 0x77, 0x63, 0x00}, // U+0057 (W)
+    {0x63, 0x63, 0x36, 0x1C, 0x1C, 0x36, 0x63, 0x00}, // U+0058 (X)
+    {0x33, 0x33, 0x33, 0x1E, 0x0C, 0x0C, 0x1E, 0x00}, // U+0059 (Y)
+    {0x7F, 0x63, 0x31, 0x18, 0x4C, 0x66, 0x7F, 0x00}, // U+005A (Z)
+    {0x1E, 0x06, 0x06, 0x06, 0x06, 0x06, 0x1E, 0x00}, // U+005B ([)
+    {0x03, 0x06, 0x0C, 0x18, 0x30, 0x60, 0x40, 0x00}, // U+005C (\)
+    {0x1E, 0x18, 0x18, 0x18, 0x18, 0x18, 0x1E, 0x00}, // U+005D (])
+    {0x08, 0x1C, 0x36, 0x63, 0x00, 0x00, 0x00, 0x00}, // U+005E (^)
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF}, // U+005F (_)
+    {0x0C, 0x0C, 0x18, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+0060 (`)
+    {0x00, 0x00, 0x1E, 0x30, 0x3E, 0x33, 0x6E, 0x00}, // U+0061 (a)
+    {0x07, 0x06, 0x06, 0x3E, 0x66, 0x66, 0x3B, 0x00}, // U+0062 (b)
+    {0x00, 0x00, 0x1E, 0x33, 0x03, 0x33, 0x1E, 0x00}, // U+0063 (c)
+    {0x38, 0x30, 0x30, 0x3e, 0x33, 0x33, 0x6E, 0x00}, // U+0064 (d)
+    {0x00, 0x00, 0x1E, 0x33, 0x3f, 0x03, 0x1E, 0x00}, // U+0065 (e)
+    {0x1C, 0x36, 0x06, 0x0f, 0x06, 0x06, 0x0F, 0x00}, // U+0066 (f)
+    {0x00, 0x00, 0x6E, 0x33, 0x33, 0x3E, 0x30, 0x1F}, // U+0067 (g)
+    {0x07, 0x06, 0x36, 0x6E, 0x66, 0x66, 0x67, 0x00}, // U+0068 (h)
+    {0x0C, 0x00, 0x0E, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+0069 (i)
+    {0x30, 0x00, 0x30, 0x30, 0x30, 0x33, 0x33, 0x1E}, // U+006A (j)
+    {0x07, 0x06, 0x66, 0x36, 0x1E, 0x36, 0x67, 0x00}, // U+006B (k)
+    {0x0E, 0x0C, 0x0C, 0x0C, 0x0C, 0x0C, 0x1E, 0x00}, // U+006C (l)
+    {0x00, 0x00, 0x33, 0x7F, 0x7F, 0x6B, 0x63, 0x00}, // U+006D (m)
+    {0x00, 0x00, 0x1F, 0x33, 0x33, 0x33, 0x33, 0x00}, // U+006E (n)
+    {0x00, 0x00, 0x1E, 0x33, 0x33, 0x33, 0x1E, 0x00}, // U+006F (o)
+    {0x00, 0x00, 0x3B, 0x66, 0x66, 0x3E, 0x06, 0x0F}, // U+0070 (p)
+    {0x00, 0x00, 0x6E, 0x33, 0x33, 0x3E, 0x30, 0x78}, // U+0071 (q)
+    {0x00, 0x00, 0x3B, 0x6E, 0x66, 0x06, 0x0F, 0x00}, // U+0072 (r)
+    {0x00, 0x00, 0x3E, 0x03, 0x1E, 0x30, 0x1F, 0x00}, // U+0073 (s)
+    {0x08, 0x0C, 0x3E, 0x0C, 0x0C, 0x2C, 0x18, 0x00}, // U+0074 (t)
+    {0x00, 0x00, 0x33, 0x33, 0x33, 0x33, 0x6E, 0x00}, // U+0075 (u)
+    {0x00, 0x00, 0x33, 0x33, 0x33, 0x1E, 0x0C, 0x00}, // U+0076 (v)
+    {0x00, 0x00, 0x63, 0x6B, 0x7F, 0x7F, 0x36, 0x00}, // U+0077 (w)
+    {0x00, 0x00, 0x63, 0x36, 0x1C, 0x36, 0x63, 0x00}, // U+0078 (x)
+    {0x00, 0x00, 0x33, 0x33, 0x33, 0x3E, 0x30, 0x1F}, // U+0079 (y)
+    {0x00, 0x00, 0x3F, 0x19, 0x0C, 0x26, 0x3F, 0x00}, // U+007A (z)
+    {0x38, 0x0C, 0x0C, 0x07, 0x0C, 0x0C, 0x38, 0x00}, // U+007B ({)
+    {0x18, 0x18, 0x18, 0x00, 0x18, 0x18, 0x18, 0x00}, // U+007C (|)
+    {0x07, 0x0C, 0x0C, 0x38, 0x0C, 0x0C, 0x07, 0x00}, // U+007D (})
+    {0x6E, 0x3B, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}, // U+007E (~)
+    {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}  // U+007F
+};
diff --git a/kernel/fonts.h b/kernel/fonts.h
new file mode 100644
index 0000000..b7a615e
--- /dev/null
+++ b/kernel/fonts.h
@@ -0,0 +1 @@
+extern const unsigned char font8x8_basic[128][8];
diff --git a/kernel/libc/stdio/print.c b/kernel/libc/stdio/print.c
index eedf026..3df6b5f 100644
--- a/kernel/libc/stdio/print.c
+++ b/kernel/libc/stdio/print.c
@@ -1,17 +1,17 @@
 #include <assert.h>
-#include <drivers/serial.h>
+#include <log.h>
 #include <stdio.h>
 #include <string.h>
 
 #define TAB_SIZE 8
 
 inline void putc(const char c) {
-  write_serial(c);
+  log_char(c);
 }
 
 void put_string(const char *s, int l) {
   for (; l > 0; l--, s++) {
-    write_serial(*s);
+    log_char(*s);
   }
 }
 
diff --git a/kernel/log.c b/kernel/log.c
index 47f6d6f..11ac783 100644
--- a/kernel/log.c
+++ b/kernel/log.c
@@ -1,13 +1,50 @@
 #include "log.h"
 #include <cpu/arch_inst.h>
+#include <drivers/serial.h>
+#include <drivers/vbe.h>
+#include <fonts.h>
 #include <sched/scheduler.h>
 #include <stdarg.h>
 
+int log_to_screen = 0;
+
+extern u8 *framebuffer;
+extern u32 framebuffer_width;
+extern u32 framebuffer_height;
+
+void log_enable_screen(void) {
+  log_to_screen = 1;
+  u32 *p = (u32 *)framebuffer;
+  for (u32 i = 0; i < framebuffer_width * framebuffer_height; i++, p++) {
+    *p = 0xFF0000;
+  }
+}
+
 struct stackframe {
   struct stackframe *ebp;
   u32 eip;
 };
 
+u32 x = 0;
+u32 y = 0;
+
+void log_char(const char c) {
+  write_serial(c);
+  if (log_to_screen) {
+    if ('\n' == c) {
+      x = 0;
+      y += 8;
+      return;
+    }
+    if (x > 1000) {
+      y += 8;
+      x = 0;
+    }
+    vbe_drawfont(x, y, c);
+    x += 8;
+  }
+}
+
 void dump_backtrace(u32 max_frames) {
   struct stackframe *stk = (void *)get_current_sbp();
   kprintf("Stack trace:\n");
diff --git a/kernel/log.h b/kernel/log.h
index fb1ce34..3955acf 100644
--- a/kernel/log.h
+++ b/kernel/log.h
@@ -6,5 +6,7 @@
 #define LOG_ERROR 1
 #define LOG_SUCCESS 0
 
+void log_char(const char c);
 void klog(int code, char *fmt, ...);
 void dump_backtrace(u32 max_frames);
+void log_enable_screen(void);