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From: scp@ibis.lanl.gov (Stephen Pope)
Newsgroups: comp.unix.wizards
Subject: Re: Indirect system call
Message-ID: <SCP.89Nov9100637@ibis.lanl.gov>
Date: 9 Nov 89 17:06:37 GMT
References: <28945@shemp.CS.UCLA.EDU>
Sender: news@lanl.gov
Organization: The Santa Fe Institute, NM
Lines: 16
In-reply-to: dieter@lynn.cs.ucla.edu's message of 8 Nov 89 21:06:03 GMT


In article <28945@shemp.CS.UCLA.EDU> dieter@lynn.cs.ucla.edu (Dieter Rothmeier) writes:

   While browsing through section 2 of the Unix manual,
   I came upon the concept of an indirect system call,
   as in syscall(2). Now that puzzled me. What might be
   the use for such a facility?

One thing they're good for is to "hide" specific system calls.
For example, one well known symbolic manipulation program
doesn't want you to use it freely, so it hides a call to
"hostid" inside an indirect system call, and compares the
result with that obtained via a normal hostid syscall.

stephen pope
scp@sfi.santafe.edu