Link a simple program and load into RTEMS with dlopen

Boldizsar.Palotas at esa.int Boldizsar.Palotas at esa.int
Tue Sep 18 06:59:14 UTC 2018


Hi,

Thank you for the help, it did work. I've reduced it to only needing `-c` 
(compile, but do not link) as the extra option.

Thanks again,
Boldizsár Palotás



From:   Chris Johns <chrisj at rtems.org>
To:     Boldizsar.Palotas at esa.int, users at rtems.org
Date:   2018.09.18 08:18
Subject:        Re: Link a simple program and load into RTEMS with dlopen



On 18/09/2018 01:29, Boldizsar.Palotas at esa.int wrote:
> Hi,

Hi, and welcome.

> I'm using RTEMS 4.11 and the builtin POSIX API functions to dynamically 
load a
> program image into memory. The program image is loaded in RTEMS using 
the
> following code:
> void* handle = dlopen(prog_name, RTLD_NOW | RTLD_GLOBAL);
> if (!handle)
>    printf("dlopen: %s\n", dlerror());

This looks fine.

> I'm using the GCC built by RTEMS Source Builder to compile the object 
located at
> prog_namein the in-memory filesystem.

Great.

> What command line should I use to properly compile a single C file to be 
loaded
> this way?

You need to use the same command line used to compile any source to an 
object
file. The dynamic loader in RTEMS supports a relocatable ELF file the 
compiler
creates with out the need for special options.

> For reference, I've tried the following command line options, but got an 
error:
> $ /opt/rtems-4.11/bin/sparc-rtems4.11-gcc test.c -c -o test.elf -shared 
-fPIC

Do not use the `-shared` option, also the `-fPIC` option is not needed for 
RTEMS
loadable code.

The RTEMS loader is not like the Linux or FreeBSD libdl loaders. The RTEMS
loader will perform a standard link-edit process to locate the code in 
your
address space.

> $ # Run in emulator, result:
> $ # dlopen: global symbol not found: _GLOBAL_OFFSET_TABLE_

This will be related to either the -shared or -fPIC options.

> I have also tried some other combinations and also using the rtems-ld 
program.

The rtems-ld command is used to managing more complex sets of object 
files. You
can load the ELF files directly.

> Any ideas?

I hope this helps.

Chris



This message is intended only for the recipient(s) named above. It may contain proprietary information and/or
protected content. Any unauthorised disclosure, use, retention or dissemination is prohibited. If you have received
this e-mail in error, please notify the sender immediately. ESA applies appropriate organisational measures to protect
personal data, in case of data privacy queries, please contact the ESA Data Protection Officer (dpo at esa.int).

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rtems.org/pipermail/users/attachments/20180918/b15fa801/attachment-0002.html>


More information about the users mailing list