Dear all,
Some of you may have played with the Xvesa server (which is different
from the VESA driver of the XFree86 server).
The Xvesa server currently runs the BIOS in VM86 mode with the
following memory map (all addresses hex):
00000 - 003FF: mapped shared from /dev/mem;
01000 - 01FFF: mapped private from /dev/zero;
A0000 - FFFFF: mapped shared from /dev/mem.
Roberto DiCosmo and myself have spent some time trying to debug the
BIOS of a laptop that would break Xvesa with a SIGSEGV in VM86 mode.
It turned out that, for some reason, this laptop's BIOS tries to do a
memory scan when switching modes; thus, it crashes as soon as it
encounters the first hole in the memory map. Using a hole-less memory
map fixes the problem.
I am therefore planning to change Xvesa to have a memory map with no
holes, and would be grateful for any advice. It is rather clear to me
that I should map 01000 through 9FFFF private from /dev/zero. On the
other hand, it is not clear to me whether 00400 through 00FFF should
be mapped private or shared, and where from.
Of course, I would be curious to learn why this machine insists on
doing a memory scan upon int 10h; conspiracy theories welcome.
Thanks for your help,
Juliusz
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