Path: utzoo!mnetor!uunet!husc6!necntc!necis!weinberg
From: weinberg@necis.UUCP (Glenn Weinberg)
Newsgroups: comp.emacs
Subject: Re: GNU under 5.3
Message-ID: <584@necis.UUCP>
Date: 6 Jan 88 23:23:52 GMT
References: <228@banyan.UUCP> <2381@ico.UUCP> <394@cosmo.UUCP>
Reply-To: weinberg@necis.UUCP (Glenn Weinberg)
Organization: NEC Information Systems, Acton, MA
Lines: 39
Keywords: NO_REMAP, alignment

In article <394@cosmo.UUCP> jum@cosmo.UUCP (Jens-Uwe Mager) writes:
>In article <2381@ico.UUCP> dougm@ico.UUCP (Doug McCallum) writes:
>>You have to define NO_REMAP.  5.3 is using regions aligned on 4Mb
>>boundaries.  If you try to remap, you will get the result you are
>>seeing.
>
>I encountered just the same problem on an sysV68 3.0 machine, I solved it
>by writing a linker control file to align to a 1Kbyte boundary only, and
>everything works fine. Is there any problems with this approach ?

There may or may not be, depending on how generous the loader (i.e.,
the code in the exec system call) is in your kernel.  Generally, these
alignment restrictions are there to make the kernel's page table allocation
mechanisms easier and/or to deal with hardware (MMU) protection alignment
restrictions.

If you use a non-standard alignment, the kernel has a few choices:

	1) It can blow you out of the water intentionally;

	2) if allowed by the hardware, it can support the non-standard
	   alignment less efficiently than the standard alignment, which
	   could affect system performance;

	3) if allowed by the hardware, it can support the non-standard
	   alignment with loss of protection, i.e., it can make (part or
	   all) of your text region writeable; or

	4) it can assume correct alignment and blow you, and possibly
	   everyone else on the system, out of the water accidentally.

Apparently, your system does either (2) or (3).

As long as you can get away with it, there's probably little or no harm
in what you're doing, but it's certainly not guaranteed to work on all
systems, or even on yours in the next release.
-- 
Glenn Weinberg (weinberg@necis.nec.com)
NEC Information Systems, 289 Great Road, Acton, MA 01720  (617) 263-3833