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Date:      Sat, 2 Mar 1996 01:19:51 +1100
From:      Bruce Evans <bde@zeta.org.au>
To:        current@FreeBSD.org, jkh@time.cdrom.com
Subject:   Re: pstat: cannot read swaplist: kvm_read: Bad address
Message-ID:  <199603011419.BAA17909@godzilla.zeta.org.au>
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>I now get this for pstat all the time, and I've recompiled all the
>libs it depends on.

The problem seems to be that /dev/kmem isn't all readable.  Only the
resident parts of it are.  This is enforced by the following code
in the memory driver:

			/*
			 * Make sure that all of the pages are currently resident so
			 * that we don't create any zero-fill pages.
			 */
			addr = trunc_page(uio->uio_offset);
			eaddr = round_page(uio->uio_offset + c);
			for (; addr < eaddr; addr += PAGE_SIZE)
				if (pmap_extract(kernel_pmap, addr) == 0)
					return EFAULT;

The pages that I looked at could be read from kmem after I looked at
them using ddb.  The ones for the swap list seemed to be normal under
ddb.  Apparently looking at them right faults them in.

Bruce
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