From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/5946 Path: news.gmane.org!not-for-mail From: Rich Felker Newsgroups: gmane.linux.lib.musl.general Subject: Re: static build and dlopen Date: Wed, 27 Aug 2014 16:51:40 -0400 Message-ID: <20140827205139.GT12888@brightrain.aerifal.cx> References: <20140827164309.GO12888@brightrain.aerifal.cx> <53FE27E6.60902@skarnet.org> Reply-To: musl@lists.openwall.com NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1409172723 11284 80.91.229.3 (27 Aug 2014 20:52:03 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 27 Aug 2014 20:52:03 +0000 (UTC) To: musl@lists.openwall.com Original-X-From: musl-return-5953-gllmg-musl=m.gmane.org@lists.openwall.com Wed Aug 27 22:51:53 2014 Return-path: Envelope-to: gllmg-musl@plane.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by plane.gmane.org with smtp (Exim 4.69) (envelope-from ) id 1XMkC9-0007bU-1E for gllmg-musl@plane.gmane.org; Wed, 27 Aug 2014 22:51:53 +0200 Original-Received: (qmail 22039 invoked by uid 550); 27 Aug 2014 20:51:52 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Original-Received: (qmail 22025 invoked from network); 27 Aug 2014 20:51:51 -0000 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Original-Sender: Rich Felker Xref: news.gmane.org gmane.linux.lib.musl.general:5946 Archived-At: On Wed, Aug 27, 2014 at 10:19:18PM +0200, piranna@gmail.com wrote: > >> Yes, I though about this option before, has a dumb statically linked > >> executable to work as PID 1 that just only exec Node.js and wait until > >> it finishes, so I can use a standard dynamically linked one and do > >> whatever I want > > > > I don't understand why you can't do whatever you want anyway. > > You can run Node.js as PID 1 even if it is dynamically linked - you > > just need to have the libc (and ld-musl.so) in the filesystem. It > > will work. You can run anything as PID 1 provided all its dependencies > > are there at boot time. Traditional inits are usually dynamically > > linked - which I think is a very bad idea, but that's another subject. > > If Node.js is a special case that cannot be treated that way, then I'm > > interested in hearing why. > > I tried to do it that way, but didn't worked. Seems on Linux when you > are using a dynamically linked executable this is not run directly, > but instead it is exec internally /lib/ld-linux.so.2, that's a program > that load and link your executable and it's dynamic libraries and > later exec it, so it takes the PID 1 and when it finish and give > control to your dynamically linked executable (Node.js in this case), > then since PID 1 has exited, the kernel has a kernel panic. The same > happens if using /usr/bin/env as she-bang, since it will get the PID 1 > and fail. You can read all that I have learned about this topics on > https://github.com/NodeOS/NodeOS-Docker/pull/12. This analysis is incorrect. Dynamic-linked programs do not involve multiple processes where the dynamic linker runs in the parent process and exits once the child is loaded; this would break absolutely everything. Whether you took the approach I described (a wrapper program that exec's ld-musl with the right arguments) or just using the dynamic-linked program directly (if you can ensure that the dynamic linker is available at the right pathname, which I think you can), it will run as PID 1 and everything will work as expected. > By the way, based on this example > (http://www.cs.utah.edu/dept/old/texinfo/glibc-manual-0.02/library_23.html#SEC410) > I've done a dumb /init program that just exec the dynamically linked > Node.js with the real /init in Javascript and it worked. Ugly hack, > but at least it does its job :-) I think you could just directly use the dynamically linked Node.js here, without the wrapper; you haven't given any indication of why this would not work. Rich