While Neal Walfield [interview] finished the initial memory management framework for the L4/Hurd port [story], Marcus Brinkmann was busy porting essential parts of glibc, namely getting the process startup code working and thus actual programs to run. This rather small step is at the end of a giant leap towards the first bootstrapping phase and opens the way for future development.

His latest patches and the add-on to glibc (which are maintained in the hurd-l4 CVS repository for the time being) enable Thread Local Storage (TLS) and Thread Specific Data (TSD) (which are prerequisites for glibc's Native POSIX Threading Library (NPTL) [story]) and also make glibc's startup and initialization code run all the way until invoking main().

This makes it possible to link a program statically against glibc and have it run in place of the bootstrap filesystem server. To this end, Marcus was able to port banner(6) to Hurd/L4, which thus has the honour of being the first user application running on the L4 port.

Concerning the future, Marcus says: "I think that this basically concludes the first step of the initial bootstrap phase. [...] we can now easily explore and develop the system in any way we want. The dinner is prepared."

From: Marcus Brinkmann
Subject: TLS/TSD support and startup/initialization working
Date: Thu, 27 Jan 2005 17:54:11 +0100


Hi,

with the changes of today, the glibc patch set in CVS supports startup
and initialization up to the invocation of the main() function - this
means important things like malloc() work.

Of course, there is a lot of cheating going on, and the implementation
is full of gaps and stubs.  But this step forward means that we can do
easy testing by just writing a program and linking it to glibc, and
run it as the "bootstrap filesystem" server.

TLS/TSD seems to work without any problems - important things like the
default locale are set up correctly, and thus strerror() works.
__thread variables are supported, glibc uses them itself.

There were a couple of fixes and extensions needed in wortel and the
startup code, but it wasn't so much.  My understanding of the glibc
code has reached an all-time high (not that this required much ;)

If you want to reproduce all this, you need to configure, make and
install the software as usual.  It is important that your compiler can
find the installed header files afterwards!  Only then you can
reconfigure your source with "--enable-libc" and try to build the C
library according to the README.

Static linking against this new libc should be possible after (manual)
installation, I guess, but I always use a very hackisch and long gcc
command line to cheat myself into a binary that I can then use as
"filesystem server" (the last one in the list) in the GRUB
configuration.  See the README for details.

I think that this basically concludes the first step of the initial
bootstrap phase.  By being able to link a program against glibc, and
by booting all the way up to that programs main() function, we can now
easily explore and develop the system in any way we want.

The dinner is prepared! :)

Thanks,
Marcus

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