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From: gershon@ccicpg.UUCP ( Gershon Shamay)
Newsgroups: net.unix-wizards
Subject: Re: /etc/savecore fails with read i/o error
Message-ID: <133@ccicpg.UUCP>
Date: Wed, 15-Oct-86 01:19:45 EDT
Article-I.D.: ccicpg.133
Posted: Wed Oct 15 01:19:45 1986
Date-Received: Sat, 18-Oct-86 00:38:07 EDT
References: <4320@brl-smoke.ARPA>
Organization: CCI CPG, Irvine CA
Lines: 17

We had similar problems with savecore on a different machine. It turned out
to be the machine-dependency of 'savecore' itself. Somewhere in it there
was a simple-minded macro which tried to map Unix virtual addresses as
seen in memory (they begin with 0x80..... on a VAX 780/etc) to 
displacements in the swap file (where the core immage is kept).
Knowing that there should be a 1-1 mapping, the macro mapped
0x80000000 to 0, 0x80000400 to 400 and so on. It did so by just
dropping the MSB of the virtual address it needed. Now on our machine
that was wrong, the kernel starts at 0xC0000000, not 0x80000000 so the
macro was generating huge displacements in the core file, eventually
failing with a read I/O error (the disk driver refused to read there).
I don't know about kernel virtual addresses on your machine, but that's
a pointer - try to look for this macro in savecore.

	Gershon Shamay
	CCI
	Computer Products Group