Hello, everyone!

I've got a question to ask about a framebuffer program I'm trying to put together for a low-level programming course at my university.

To the point. Target architecture is x86-64. I've managed to map the framebuffer device file /dev/fb0 to memory. However, when I try put a pixel on screen, the program segfaults. I haven't got even a vague idea what may be the cause.

I would be grateful for any hints. My situation is pretty hard, as I don't know anyone skilled in this field. The source is accessible here [1].

Regards,
Radosław Szymczyszyn

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[1]: http://ernie.icslab.agh.edu.pl/~lavrin/fb.asm

I think your problem is here: 'fb' is allocated as only one qword but you are writing to it with offsets in rbp.

Perhaps you can try something like this:

You're perfectly right. Thanks!