amd64/127276: ldd invokes linux yes
kamikaze at bsdforen.de
Thu Sep 11 16:40:04 UTC 2008
The following reply was made to PR amd64/127276; it has been noted by GNATS.
From: Dominic Fandrey <kamikaze at bsdforen.de>
To: Rui Paulo <rpaulo at FreeBSD.org>
Cc: John Baldwin <jhb at freebsd.org>, freebsd-gnats-submit at freebsd.org,
freebsd-amd64 at freebsd.org
Subject: Re: amd64/127276: ldd invokes linux yes
Date: Thu, 11 Sep 2008 18:37:23 +0200
Rui Paulo wrote:
> On Thu, Sep 11, 2008 at 07:01:09AM +0200, Dominic Fandrey wrote:
>> I don't need it to work, I just need it not to invoke linux binaries. I'm
>> using ldd in a script and by ldd not returning 0 the script should know that
>> it hasn't encountered a valid binary. Instead ldd opens a linux binary like
>> yes and the script spills out ys (yes) or waits for input from stdin
>> (md5sum). I'm pretty certain ldd is in no way meant to invoke programs.
> I chatted briefly with John about this. The way our ldd works is by
> setting the environment variable TRACE_LOADED_OBJECTS and after some
> dlopen() magic it exec()'s the binary. FreeBSD rtld detects the environmental
> variable, prints the list of shared objects and quits.
> Linux rtld doesn't work this way, so FreeBSD ldd on a Linux binary will
> just run the Linux binary (Linux rtld will ignore the rest).
> Also, ldd wil return 1 on static binaries. Your best bet is to use
> file(1) to detect FreeBSD binaries. Something like `file $binary | grep
> FreeBSD-style` does the trick.
Ok, thanks. I have already created a workaround with readelf, but I'd still
consider this a bug in ldd. Shouldn't it check the elf brand if it only
works for a single one?
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