Re: [PATCH] make uselib configurable (was Re: uselib() & 2.6.X?)

From: Andries Brouwer <aebr@win.tue.nl>
To: "Barry K. Nathan" <barryn@pobox.com>
Cc: Linus Torvalds <torvalds@osdl.org>,
	Marcelo Tosatti <marcelo.tosatti@cyclades.com>,
	Alan Cox <alan@lxorguk.ukuu.org.uk>,
	Lukasz Trabinski <lukasz@wsisiz.edu.pl>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] make uselib configurable (was Re: uselib()  & 2.6.X?)
Date: Wed, 12 Jan 2005 00:59:07 +0100	[thread overview]
Message-ID: <20050111235907.GG2760@pclin040.win.tue.nl> (raw)
In-Reply-To: <20050111225127.GD4378@ip68-4-98-123.oc.oc.cox.net>

On Tue, Jan 11, 2005 at 02:51:27PM -0800, Barry K. Nathan wrote:
> On Sat, Jan 08, 2005 at 10:46:19AM -0800, Linus Torvalds wrote:
> > Another issue is likely that we should make the whole "uselib()"
> > interfaces configurable. I don't think modern binaries use it (where
> > "modern" probably means "compiled within the last 8 years" ;).

libc 5.4.46 is from 1998-06-21 or so, glibc 2.0.5 from 1997-08-25 or so.

> +config SYS_USELIB
> +	bool "sys_uselib syscall support (needed for old binaries)"
> +	---help---
> +	  Many old binaries (e.g. dynamically linked a.out binaries, and
> +	  ELF binaries that are dynamically linked against libc5), require
> +	  the sys_uselib syscall. However, on the typical Linux system, this
> +	  code is just old cruft that no longer serves a purpose.
> +
> +	  If you are unsure, say "N" if you care more about security and
> +	  trimming bloat, or say "Y" if you care more about compatibility
> +	  with old software. (If you will answer "Y" or "M" to BINFMT_AOUT,
> +	  below, you probably should answer "Y" here.)

s/sys_uselib/uselib/
The system call is uselib().

Hmm - old cruft.. Why insult your users?
I do not have source for Maple. And my xmaple binary works just fine.
But it is a libc4 binary.

You mean "on the typical recently installed Linux system, with nothing
but the usual Linux utilities".

People always claim that Linux is good in preserving binary compatibility.
Don't know how true that was, but introducing such config options doesnt
help.

Let me also mutter about something else.
In principle configuration options are evil. Nobody wants fifty thousand
configuration options. But I see them multiply like ioctls.
There should be a significant gain in having a config option.

Maybe some argue that there is a gain in security here. Perhaps.
Or a gain in memory. It is negligible.
I see mostly a loss.

There are more ancient system calls, like old_stat and oldolduname.
Do we want separate options for each system call that is obsoleted?

Andries