Path: utzoo!mnetor!uunet!husc6!rutgers!iuvax!bsu-cs!dhesi
From: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Newsgroups: comp.arch
Subject: Re: self-modifying code
Message-ID: <2169@bsu-cs.UUCP>
Date: 20 Feb 88 17:32:29 GMT
References: <486@taux01.UUCP> <666@cresswell.quintus.UUCP> <815@spar.SPAR.SLB.COM>
Reply-To: dhesi@bsu-cs.UUCP (Rahul Dhesi)
Organization: CS Dept, Ball St U, Muncie, Indiana
Lines: 16
Summary: solution

[re: how to overcome the code versus data distinction]

For those implementors who wish to allow data to be safely treated as
code, I suggest a system call that will accept a range of memory
addresses and a request to change it from code to data or from data to
code.  E.g.:

     #include <modech.h>
     if (modech(startadd, endadd, TO_CODE) == -1)
        error ("could not change data into code for execution");

This preserves the advantages if any of the code/data distinction
without being a pain to the implementor.  No doubt there would be some
alignment restrictions on the values of startadd and endadd.
-- 
Rahul Dhesi         UUCP:  <backbones>!{iuvax,pur-ee,uunet}!bsu-cs!dhesi