[ECOS] Objloader question

["Retallack, Mark \(Siemens\)" <mark dot retallack at siemens dot com>]

Sorry if this is a repeat mail, problems with the mail server.

Hello, I have just been looking at the new objloader (a very useful and
cool package), and I have run into a problem. 

I have written a very simple test app to see how it works, all the app
does is export the open_library and a myapp function. When the myapp
function is loaded and called, it should just call the diag_printf
function. However the diag_printf function is stored in flash  (starts
at 0x40000000) and the myapp function is stored in ram (starts at
0x00000000). 

In the myapp.o file, the diag_printf function is defined as a
R_PPC_REL24  relocatable entry, I am running a PowerPC system which
means that it is not possible to perform a branch over the 16MB
boundary. To get this to work I need a method of making the R_PPC_REL24
perform a jump instead. 

I have looked into the following options:

Option 1: Use gcc with the -mlongcall option. 

I have looked at the gcc manual and I believe this should work, however
my version of gcc (3.2.1) does not support the -mlongcall option and I
would prefer not to have to use a different gcc toolchain.

Option 2: Add a branch island 

This would be a ram located "trampoline" than would perform a jump to
the diag_printf in flash when is is called from the myapp function. This
looks like the best long term solution, but I still need to come up with
a way of doing it.


Does anyone have any other ideas? I did think that the MMU could be used
somehow?

Thanks in advance. 


Mark Retallack
Embedded Software Engineer
Siemens Traffic Controls 
Sopers Lane, Poole, Dorset. BH17 7ER. UK.
Tel: 01202 782189
Fax: 01202 782545
www.siemenstraffic.com

Committed to quality traffic solutions and service excellence


Todays Quote:

I can't decide which WRONG TURN to make first!!  


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