[pok-devel] Start a guest binary in a partition

[Philipp Eppelt <philipp.eppelt@xxxxxxxxxxxxxxxxxxxxx>]

Hi,

I am a student at Dresden University of Technology, currently applying 
to Google Summer of Code for the RTEMS project.

The purpose of my project is to design and implement a 
paravirtualization layer in RTEMS to ease virtualization. As 
proof-of-concept I like to use POK as host system.

In last year's GSoC a student used POK to run RTEMS with the goal to get 
RTEMS ARINC 653 compliant.
He introduced new syscalls to POK and combined the RTEMS partly linked 
..ralf file with the POK binary. He used cat to pipe both binaries into 
the same file and used some 'magic' to fuse the two systems.
However, none of the usual tools (nm, readelf, objdump) read the 
resulting binary correctly, therefore I refrain from taking this way.
Additionally, I don't want to use direct syscalls from the guest, as the 
virtualization layer in RTEMS should be portable.


Now I am searching for a way to start the RTEMS guest binary.
My first idea was to build an application in POK containing all 'guest 
communication functions' (e.g. disable/enable interrupts, console 
access) and to pass the fully linked file as a library to RTEMS. Then 
the RTEMS build process would run without errors, as the missing 
function implementations are provided.
But I don't know, how I can call the RTEMS bsp_start() function for 
instance, as POK doesn't know about this at compile time.

The second idea was to build RTEMS first. This will fail due to 
undefined references cause by the 'communication functions'. The partly 
linked .ralf file could then be inserted while POK is linked, resolving 
the undefined references. This is pretty much the approach of last 
year's student. But that would intercept with the build process of POK 
and is therefore no satisfying approach. An custom linker script might 
resolve the issues with the tools, though.


So I am a little stuck here and seeking guidance.
Do you have another idea?
Is there some source code supporting foreign binaries to be executed in 
a partition?
Do you know of projects doing something similar?


Regards,
Philipp