Date: Fri, 6 Oct 2006 12:50:20 GMT From: Daniel Eischen <deischen@freebsd.org> To: freebsd-threads@FreeBSD.org Subject: Re: threads/103975: Implicit loading/unloading of libpthread.so may crash user processes Message-ID: <200610061250.k96CoK2R002708@freefall.freebsd.org>
next in thread | raw e-mail | index | archive | help
The following reply was made to PR threads/103975; it has been noted by GNATS.
From: Daniel Eischen <deischen@freebsd.org>
To: Takahiro Kurosawa <takahiro.kurosawa@gmail.com>
Cc: Alexander Kabaev <kabaev@gmail.com>, John Baldwin <john@baldwin.cx>,
freebsd-gnats-submit@freebsd.org, freebsd-threads@freebsd.org
Subject: Re: threads/103975: Implicit loading/unloading of libpthread.so may
crash user processes
Date: Fri, 6 Oct 2006 08:42:19 -0400 (EDT)
On Fri, 6 Oct 2006, Takahiro Kurosawa wrote:
> Alexander Kabaev <kabaev@gmail.com> wrote:
>> On Thu, 5 Oct 2006 09:06:20 -0400
>> John Baldwin <john@baldwin.cx> wrote:
>>
>> > > To fix the problem, a function that has __attribute__((destructor))
>> > > in libpthread should probably be implemented in order to recover
>> > > the initial state before unloading.
>> >
>> > I'm not sure you can recover the state actually, hence why I think
>> > maybe we should make it so that libpthread doesn't unload once it has
>> > been loaded.
>
> I understand that it's way easier to prohibit unloading of libpthread
> than to change the code safely unloadable.
> Thanks for your explanation, John!
>
>> Linux does not allow pthread library to be unloaded presumably because
>> of reasons like this. From readelf -a /compat/linux/lib/libpthread.so.0:
>>
>> 0x6ffffffb (FLAGS_1) Flags: NODELETE INITFIRST
>>
>> Infortunately, rtld does not implement NODELETE and INITFIRST. Both are
>> addressed in my patch that I am yet to commit.
>
> I'm looking forward to the commit of your patch into the CVS repository :-)
> Maybe the following line should be added to src/lib/libpthread/Makefile
> when rtld supports the NODELETE flag? :
> LDFLAGS+=-Wl,-znodelete
If that's the knob, then I'd agree. You also want to make
the same change to libthr.
--
Dan
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200610061250.k96CoK2R002708>