Blink by orbitaldecay [web]
Blink 1.0
orbitaldecay@gmail.com
-~= What is Blink? =~-----------------------------------------------------------
Blink is a 32bit protected mode OS kernel for x86 PCs in 256 bytes! Blink
is multiboot compatible, so it can be booted by any multiboot compliant boot
loader (GRUB is all I've tested it with). Userland code is provided to the
kernel to execute by means of multiboot modules.
When Blink is loaded, it specifies the VESA mode it would like to use to the
multiboot boot loader. Thus, once userland code starts, a linear frame buffer is
already available for drawing. This makes Blink particularly well suited for
writing size code.
-~= How to run Blink =~---------------------------------------------------------
To run Blink, you'll need GRUB2 installed. It won't work with GRUB legacy
because GRUB legacy doesn't support the VESA graphics features of the multiboot
specification (AFAIK). At the GRUB2 boot menu, press C to bring up a command
line. Then type
> legacy_kernel /path/to/blink.bin /path/to/blink.bin
> module /path/to/intro.bin
> boot
where '/path/to' represents a fully qualified path name. After typing 'boot'
and pressing enter, Blink will boot and execute the userland code contained in
intro.bin.
-~= Writing Userland code for Blink =~------------------------------------------
Blink sets up a very minimal userland environment. There is no way to
control where GRUB loads multiboot modules, so all userland code must be
position independent. Blink does, however, place the address of the begining
of the module in ESI and the address of the linear frame buffer in EDI before
jumping to the userland module. Blink does not set up a stack for the userland
code, so if you need one you'll have to set it up yourself. Blink reserves
memory from 0x00100200 to 0x00200000 for use by userland code. Various constants
are stored in settings.def which should aid development. For example, if you
wanted to set up a stack and install an ISR to run every time the timer is
triggered (IRQ0), you could do it like this:
%include 'settings.def'
bits 32
user.start:
; At this point ESI contains a pointer to USER.start (which could be loaded
; anywhere) and EDI contains a pointer to our linear frame buffer (LFB)
; Initialize segment registers and setup stack
mov esp, USER_STACK ; USER_STACK is defined in settings.def
; Save pointer to LFB
mov [USER_DATA], edi ; USER_DATA is defined in settings.def
; Install ISR 0x20 to draw when the timer goes off (IRQ0)
mov eax, IDT_ADDR + 0x20 * 8 ; IDT_ADDR is defined in settings.def
add esi, (user.isr20h - user.start)
mov word [eax], si
shr esi, 16
mov word [eax + 6], si
user.spin:
jmp user.spin
; ISR for 20h
user.isr20h:
pushad
; Clear master PIC
mov al, 0x20
out 0x20, al
; Fill the screen
mov eax, USER_DATA
mov ebx, [eax] ; Load LFB address
mov edx, [eax + 4] ; Load frame counter
xor ecx, ecx ; Clear the pixel counter
user.isr20h_fillscreen:
mov byte [ebx + ecx * 4], dl
inc ecx
cmp ecx, VID_WIDTH * VID_HEIGHT ; Video resolution from settings.def
jnz user.isr20h_fillscreen
; Increment frame counter
inc dword [eax + 4]
; Goodbye
popad
iretd
user.end:
-~= Thanks =~-------------------------------------------------------------------
... to the OS dev community and all the 1337 h4xx0rz out there who keep the
scene alive. E-mail me with questions or comments. Peace.
orbitaldecay 2014
[ back to the prod ]