because push eax will atomicly advance stack and copy register
ok not atimicly but interrupt wont happen inside instruction. cpu check its interrupt pins before executing instruction.


I can setup idt gate with ring3 selector.

question
there is a way to shift bits filling them with 1's:

0000 0011
0000 1111 ; shl 2
1111 1111 ; shl 6

1100 0000
1111 1100 ; shr 4

rcl, rcl + stc
only for one shift.





or for many shifts:

The closet in x86 with a single instruction is sar. Otherwise just do an or after the shift.

[edit]
Just to slightly improve on edfed's suggestion:

use shld:

.



NO. As long as no interrupts arrive and no exceptions occur, then you need no IDCT. If nevertheless: BOOM (TripleFault)

so why in that tutorial teaches to define one if there is no interupts or exceptions in PM? o.o

It would not be a very useful PM OS if you don't allow interrupts or exceptions. While an IDT is not required it is certainly desired.

Try this: "you are not required to put on clothes when you go to work"

With interrupts you can:
1) catch mouse and keyboard movement - very useful
2) catch time events - less useful, but you can update clock and measure time (of course there are other ways)
3) usually system functions are implemented through interrupting. For example int 64 (with eax=123), you can "call" system function number 123, which can be helpful to draw images or other stuff...

yep, IRQ (interupt request) is the link to the outside of the CPU.

without them, the computer is just a non interactive calculator.
with them, it becomes a video game, a web browser, a mp3 player, a porn watcher, a pic programmer, etc...

but if i cant use INTs in PM, how to catch mouse & keyboard in PM then? o.o

You can't, that is why it is wise to setup an IDT. Without a proper IDT then no interrupts allowed. With an IDT then interrupt away to your OS requirements.

hmm okay.

Just to clarify, you can't catch events, but you can poll for them without using interrupts. It is usually not as convenient to use polling. But one never knows your particular requirements may just be perfect for a polling non-interrupt OS.

to catch events form keyboard and mouse in PM, first switch in PM with interrupts disabled.
get a good video driver and lib to display infos, it will be usefull for debug later.

and then, reprogram pic to revector IRQ0 to 7 to a non reserved vector (INT 20h is the first allowed vector for user in PM), and relocate IRQ 8 to 15 to the next, then, INT 28h.
declare a vector for IRQ1 (INT21h) to the keyboard handler
declare a vector for IRQ12 (INT2Ch) to the mouse handler.

and then, it is ok, you can exploit any jkeyboard and mouse driver source code, by converting them to work in PM memory interface, basically, use32 and assume DS=linear0

If you look at http://board.flatassembler.net/topic.php?p=118339#118339 and open VESA64_15.11_resize.7z , browse to Stage2\PIC_PIT.inc , you can see that the code to do that is really simple. Sorry that I haven't had more time to comment the code, but you can always find support from this site: http://wiki.osdev.org/PIC

I will check.
But first lets go back a lil bit. I need ask why its faster to use a double buffer instead to access directly the video memory.

take as an example:
you put an image, then, over the image, you put a box, inside the box, you put a text and another image.

some pixels will be writen many times before to have their final values.

if you do the writes directlly in video memory (that is slow), you will loose a lot of time.
that's why it is better to first fill a buffer located in fast RAM, and transfert it in video memory ones it is done.
each pixels in video memory will be writen only one time.

Thank you, ed.