Guru Meditation when accessing RAM (through mapping) @ 0xB8000

[Markus Duft]

Hi!

I'm writing a little hobby kernel (sources @ [1]), and now try to run it on virtualbox. it works fine on qemu, bochs and real hardware. The kernel is a x86_64 kernel. It runs perfectly on VirtualBox, with one little exception: if i try to do something on the screen, a guru meditation results (log attached).

The code causing the crash maps the VGA memory 0xB8000 to a virtual memory location (which succeeds), and then tries to write to the buffer (which crashes).

as i said, this works on qemu, bochs and real hardware, only vbox crashes. is this a limitation i should be aware of?

i'll attach:

• the log for the meditation.
• a cd image containing the kernel booted by grub2.

[1] ​https://github.com/mduft/tachyon3/blob/master/src/x86/cga.c

[Markus Duft]

Log of guru meditation