Linux 2.1 Virtual Memory problem

David Howells (
Tue, 20 Jan 1998 08:46:35 GMT

Well, not actually a bug, but can someone help me with a small problem... To
summarise, I need to be able to map physical address 0xFFFFD000 to virtual
memory from kernel space.

This is why:

* Part of my configuration manager accesses the Bios16 routines for PnP-BIOS
facilities, and one of those routines is for reading the ESCD area.

* This requires a segment selector setting up to enclose a particular area of
memory (specified by the BIOS), which I can do.

* The problem arises in my new BIOS/motherboard, in which the base address of
the NV memory is at physical address 0xFFFFD000, which is not mapped to any
virtual address as far as I can tell...

* I have no problems getting into the BIOS itself (which is at 0x000F0000),
and can call the routines and get back to the kernel with out a hitch.

Can someone suggest a way around this from within kernel space? It must be
possible from user space certainly, as my X server can mmap my graphics card
frame buffer.

Many thanks,
David Howells