musl - re-opening a shared object

Follow @Openwall on Twitter for new release announcements and other news

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20170704162100.0d0da430@vostro.util.wtbts.net>
Date: Tue, 4 Jul 2017 16:21:00 +0300
From: Timo Teras <timo.teras@....fi>
To: musl@...ts.openwall.com
Subject: re-opening a shared object

Hi,

I mentioned this issue earlier in the IRC, but wanted to write it as an
email so this does not get forgotten.

Basically the issue at hand is that at least Asterisk and Kamailio
(possibly others too) have a plugin system, where the plugin can
request whether it's symbols should be global or not. To implement this
the core code may dlopen the library, then dlclose, and finally dlopen
again with different flags. This does not work in musl since dlclose is
a stub, and dlopening again with different flags seems to not do
anything.

As example the sequence for kamailio is mostly:
 1. dlopen(file, RTLD_NOW)
 2. call library to figure out it wants RTLD_GLOBAL
 3. dlclose()
 4. dlopen(file, RTLD_NOW|RTLD_GLOBAL)

But I also think the Asterisk code is doing the opposite - defaulting
to RTLD_GLOBAL|RTLD_LAZY, and re-opening with RTLD_LOCAL|RTLD_NOW if
needed (which I think should be the other way around).

Anyway, would it be feasible to implement the above in musl? Perhaps,
by having dlopen() explicitly support promoting RTLD_LAZY to RTLD_NOW;
and RTLD_LOCAL to RTLD_GLOBAL? What would be the way to implement this?

Thanks
Timo

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.