[uclibc-ng-devel] problem with stack protection, threads and static binaries

Daniel Fahlgren daniel at fahlgren.se
Wed Sep 16 08:41:15 CEST 2015

Hi Waldemar,

On Mon, 2015-09-14 at 06:52 +0200, Waldemar Brodkorb wrote:
> ...
> Does this happen only when uClibc itself is compiled with stack
> protection? Or just when the pthread app is statically linked and
> compiled with -fstack-protector?

This only happen when libpthread.a is compiled with stack protection and
the binary is statically linked. I have tried compiling the app both
with and without -fstack-protector-all but that doesn't change the
behavior. A libpthread.a not compiled with stack protection also does
not show this behavior.

> > With uClibc 0.9.33.x the same thing happens. With glibc the program
> > works.
> I can reproduce the bug. Moving __libc_setup_tls from NPTL init to
> __uClibc_main.c fixes it. Why do you think it is ugly to do this?

With my patch __libc_setup_tls() was called twice. I also haven't
thought it through if if is ok to simply move it from the pthread code
or if something else is depending on it being there.

> Does attached patch works for you? Just a cleaned up version of your
> fix. It doesn't produce any regressions running the testsuite.

Yes, that patch works just fine. I have tested it on my limited test
case as well as in the environment where I first encountered the bug.

Thanks and best regards,
Daniel Fahlgren

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