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Subject: Re: possible 4th option? [Re: kern/1102]
To: jdp@polstra.com (John Polstra)
Date: Tue, 23 Apr 96 9:23:07 MDT
From: Greg Lehey <lehey.pad@sni.de>
Cc: terry@lambert.org, mmead@Glock.COM, smpatel@freebsd.org,
        current@freebsd.org, ec0@s1.GANet.NET
In-Reply-To: <199604230135.SAA03252@austin.polstra.com>; from "John Polstra" at Apr 22, 96 6:35 pm
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>>>> The 2nd
>>>> option you mention is the one in which you would use currently unused
>>>> bytes in the ELF e_ident tag.
>
> They're not unused -- they're _reserved_.  If you stick anything other
> than 0 in them, you're technically no longer producing a valid ELF file.
> The analogous objection applies also to other ELF header fields such as
> e_type, e_machine, and e_flags.
>
> The ELF specification defines a mechanism for adding extra identifying
> information to an executable file: the PT_NOTE program header, and
> associated SHT_NOTE section.  That's how I think that different kinds
> of ELF executables should be recognized.  The good thing about NOTE
> sections is that each chunk of information contains, among other things,
> a "vendor tag" which is a string.  It's not that likely that Sun is
> going to collide with a vendor tag of, say, "FreeBSD, Inc." or "Free
> Software Foundation".

Sounds reasonable, even if it's a bit tedious.

> I'm going to try to add this kind of identification to our FreeBSD ELF
> executables, and fix the kernel to recognize them.  (Unfortunately, as
> usual, the binutils code maze is doing its best to make this difficult
> for me.)  I'd like to coordinate this with the Linux people, if they're
> interested.

Good idea.  While you're at it, why not give Sun and SCO a chance to
cooperate?

Greg