[Milkymist-devel] Compiling uClinux/LM32 userspace apps

[Sébastien Bourdeauducq]

Hi Jon,

We are facing serious problems with compiling userspace applications for the 
Linux port to LM32/Milkymist. So far, we have been successful at porting and 
running the kernel, and we have userland working thanks to binaries we copied 
from the sample filesystem image available at
http://www.theobroma-systems.com/uclinux-lm32/

However, we cannot compile them ourselves. We tried:
- using GCC 4.4, uClibc from Theobroma and your patch: binary does not start, 
and Busybox prints its "applet not found" error message which seems to be a 
catch-all generic message for execution problems.
- using the binary lm32-linux toolchain available from the Theobroma website 
(http://www.theobroma-
systems.com/assets/downloads/mico32/lm32linux-20080206toolchains_linux.tar.gz): 
the kernel prints "Error: not enough relocations found" and the system crashes 
and reboots.
- from the GNU LD doc, it seemed that we needed to add the -i linker flag to 
add relocation info to the binary. We did that, and the system no longer 
crashed but printed "applet not found" instead.
- looking at the scripts available at http://www.theobroma-
systems.com/assets/downloads/mico32/lm32linux-20080206.tar.gz
it seemed we needed to pass -q as well to the linker. That did not help.
- we also tried passing -fPIC to the compiler, without change.

So, my questions are:
* How does the LM32 FDPIC works? There is no documentation at all, and uClibc 
and the kernel are full of dirty and sometimes contradictory "hacks" (as the 
code comments say...), making it very hard to understand. If we knew how it is 
supposed to work, we could debug the problem more efficiently than trying 
every combination of compiler/linker options we find lying around in 
Theobroma's scripts.
* Do you think the Theobroma binary toolchain could work, or is it broken 
beyond repair? In the former case, what are the options that we should pass to 
the linker and compiler so that the binaries can start?

Thank you,
Sébastien