Simple question about RTL

[xuelin.tian at qkmtech.com]

I follow the instructions which Pavel Pisa posted online. 
https://lists.rtems.org/pipermail/devel/2016-July/015683.html 
But, when I go to the "prelink generation" step, which is "arm-rtems4.11-gcc ${CFLAGS1} -Wl,--gc-sections init.o rootfs_tarfile.o -lm -o appdl.prelink", some error came up, 
#/.../ld: failed to merge target specific data of file init.o
#/.../ld: warning: cannot find entry symbol _start; defaulting to 0000000000008000
#collect2: error: ld returned 1 exit status

And he did not use rtems-ld to generate any file, so I got a little confused. Any idea?

Later, I also tried to use rtems-ld to link init.o and rootfs_tarfile.o, and it said:
#resolver:resolving: undefines, unresolved: 1
#resolver:resolve: |- rtems
#error: undefines: symbol not found: rtems
Here, I just want to know what '-b' the base kernel is, an object file (after compile before link), or an .exe (after statically link)? Thanks.




Best wishes,
Tim Tian
xuelin.tian at qkmtech.com
 
From: Chris Johns
Date: 2016-08-25 13:30
To: xuelin.tian at qkmtech.com; users at rtems.org
Subject: Re: Simple question about RTL
On 25/08/2016 1:02 PM, xuelin.tian at qkmtech.com wrote:
> Hi Chris,
> thanks for you reply. I'm trying to understand the concept here, and
> some points are still confusing me.
> In general, linking process should happen before applications taking
> control of CPU, which means the OS should handle the linking process.
 
The RTL provides a run-time link editor which allows you to load code 
with-in your running application. Libdl is the link editor. It is you or 
your code that tells it what to do.
 
> In
> RTEMS, the Init task should take care of this, am I right?
 
The Init task is your 'main' so this is your code. You are free to 
structure how you manage this just like any other part of your application.
 
> Now, for example, I have one base kernel and one tar file. My base
> kernel is running on my target (ZedBoard), and how can I load the tar
> file into memory using shell command via Jtag?
 
For an engineering development environment I would enable networking 
using libbsd and then NFS mount an exported disk from a host on the 
network. I would place the ELF object files where you can see them from 
the Zedboard and then use the RTL command to load the code.
 
Chris
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