/dev/mem and highmem

Nicolas George (nicolas.george@ens.fr)
Mon, 3 Mar 2003 17:00:50 +0100

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Is there any hope to have access to the highmem through /dev/mem, or a
similar device? Or did I miss an already existing method?


These days, bad RAM seems to become dramatically frequent. We have here
a PC with a few bad bits (switching to ECC is in project), but memtest86
did not find them. Recently, sshd started to segfault. Using cmp -lb
with an uncorrupted version we found the bad bit in the file, and then
looked for it in the phyical memory with `xxd /dev/mem | grep'. We found
it, disabled the area using mem=3D boot parameter.

Now this PC has a crontab that will write pseudo-random data in the
disabled area, and later read it back and compare it with the original
to find all bad bits.

Then I have another PC with bad RAM, I also discovered a file affected,
and tried the same method. Unfortunately the grep failed. The reason is
likely to be that the file was in highmem.

PS: please Cc me the answers.


Nicolas George

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