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From: ignatz@aicchi.UUCP (Ihnat)
Newsgroups: net.unix-wizards
Subject: Re: Do you believe in MAGIC?
Message-ID: <491@aicchi.UUCP>
Date: Wed, 12-Jun-85 02:27:23 EDT
Article-I.D.: aicchi.491
Posted: Wed Jun 12 02:27:23 1985
Date-Received: Thu, 13-Jun-85 01:07:59 EDT
References: <821@unmvax.UUCP> <490@usl.UUCP> <82@decvax.UUCP> <106@aplvax.UUCP> <814@mako.UUCP>
Reply-To: ignatz@aicchi.UUCP (Ihnat)
Distribution: net
Organization: Analysts International Corp; Chicago Branch
Lines: 28

In <814@mako.UUCP>, Jan Steinman comments:


>	"...their code space is writable.  Two uses
>	are old binaries, and new programs that, for some reason, require
>	writes to code space. ...  "

Like programs to be run under interactive, intrusive debuggers.

>	The only way we know to have writable data below the code
>	space is to use OMAGIC format.  Note that I am not advocating
>	dynamic code modification; I simply need more control over
>	data - code layout than UNIX gives me.
>	
>	When facilities for explicit control of memory management are available,
>	OMAGIC can probably be put to bed, at least for new code.

I assume, from your comments, that you're on a BSD or BSD-derived site.  I
would like to point out that, although it's not yet widely documented,
the COFF (Common Object File Format) loader (admittedly only on System
V) has a fairly rich range of link editor directives, which give the programmer
good control over the final composition of the executable image and its
memory layout.
-- 
	Dave Ihnat
	Analysts International Corporation
	(312) 882-4673
	ihnp4!aicchi!ignatz