Re: [uml-devel] Re: uml-patch-2.6.0

[M A Young <m.a.young@durham.ac.uk>]

On Mon, 19 Jan 2004, Ingo Molnar wrote:

>
> * Ingo Molnar <mingo@elte.hu> wrote:
>
> > > 2.4 UMLs work fine with these libcs.  I had been assuming (without any
> > > evidence) that there was some other capability check (like uname), and
> > > libc gets horribly confused when it sees a 2.6 kernel that doesn't
> > > have the thread_info stuff.
> >
> > ok, i talked to Ulrich, and it turns out that ld.so in Fedora uses the
> > set_tid_address() syscall to find out whether the kernel has NPTL or
> > not [and thus whether to use the TLS glibc or the standard one]. [...]
>
> unfortunately, this is only the case if the kernel is below 2.5.69 and
> has 'nptl' in the uname. Otherwise ld.so assumes full NPTL support.
>
> so the only compatible solution seems to be to implement
> set/get_thread_area() within UML. Since UML itself is linked statically,
> which causes the non-TLS glibc to be linked, i think it should be safe
> to just shadow the TLS descriptors in the UML process and call
> set_thread_area() for every new thread that has TLS descriptors not
> equal to the previous thread's TLS descriptors.

I have found in tt mode with an FC1 image the system hangs after 3
syscalls (uname, brk, open), before any set/get_thread_area calls, so I
suspect there is another problem. The hang consists of repeated segfault
signals with fault address (beffe018) which returns -EFAULT. Is there any
setup for tls/nptl normally done by the kernel that might be missing in
UML, such as allocating some high up memory?

	Michael Young


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