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Subjectmmap from 0xFFFF0000 -> 0xFFFFFFFF does not work, why?!
Hi all,

1st Question :

i'm working at a bios flash utility for some pc manufacture and have trouble
in using the mmap function :(

I need access to the address space starting at 0xFFFE0000 to 0xFFFFFFFF where the flash chip copy its contents. I use the /dev/mem device driver to access the memory environment throw the mmap function but it does not work. So i decrease the size from 0x20000 to 0x20000 - getpagesize() and what happens, yes mmap exit without any error.

Why can i not mmap from 0xFFFE0000 with the size of 0x20000 bytes ?!
More background information. I have to program the vendor specific PCI devices
before i get the access to the flash contents. This PCI device handels the
write/read operations to that flash chip and the region where its contents
will be mirrored. I can NOT change the region where it will be :(

2nd Question :

Perhapps it will be a stuppid question but how can i access the mapped memory ?!
Can i use simple cpu memory access or is it required to use the read/write
function with the previous get file handle by open("/dev/mem", ..) ?!

3rd Question :

The access to the flash chip is VERY time critical. I need a function that
allows me to protect the current task from others. While accessing the flash memory mapped before, NO other task should/must get processor time. Which technique solve this problem ?!

4th Question :

Because the pentium processors have caches it is required to disable them
before access the flash memory (you know, time critical access). So i include
some assembler code that use the %cr0 pentium processor register but i get
segfaults while executing this source line :( How can i disable the cpu cache
withou using the assembler code within the user application ?! Of course, only
root can do that.

I hope this questions fits in the mailling list because it is the last chanse
for me, no one else could help me...

I realy HOPE get hopeful answers, thx.

Raphal Bossek <>
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