2004-11-08 04:28:53

by Gene Heskett

[permalink] [raw]
Subject: makeing a loadable module

Greetings;

I found some code I can play with/hack/etc, in the form of a loadable
module and some testing driver programs, in 'dpci8255.tar.gz'.

Unforch its for a slightly different card than the one I have, and
once I've hacked the code to suit, I need to rebuild it.

So whats the gcc command line to make just a bare, loadable module for
say a 2.4.25 kernel? Obviously I'm missing something when it
complains and quits, claiming there is no 'main' defined, which I
don't think modules actually have one of those?

What I'm trying to do (hey, no big dummy jokes please :)

[root@coyote dist]# cc -o dpci8255.o dpci8255lib.c
/usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crt1.o(.text+0x18):
In function `_start':
: undefined reference to `main'
collect2: ld returned 1 exit status

The gcc manpage isn't that helpfull and I've now read thru it twice.

--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
99.28% setiathome rank, not too shabby for a WV hillbilly
Yahoo.com attorneys please note, additions to this message
by Gene Heskett are:
Copyright 2004 by Maurice Eugene Heskett, all rights reserved.


2004-11-08 06:11:50

by Eric Gaumer

[permalink] [raw]
Subject: Re: makeing a loadable module

On Sun, 2004-11-07 at 23:28 -0500, Gene Heskett wrote:
> Greetings;
>
> I found some code I can play with/hack/etc, in the form of a loadable
> module and some testing driver programs, in 'dpci8255.tar.gz'.
>
> Unforch its for a slightly different card than the one I have, and
> once I've hacked the code to suit, I need to rebuild it.
>
> So whats the gcc command line to make just a bare, loadable module for
> say a 2.4.25 kernel? Obviously I'm missing something when it
> complains and quits, claiming there is no 'main' defined, which I
> don't think modules actually have one of those?
>
> What I'm trying to do (hey, no big dummy jokes please :)
>
> [root@coyote dist]# cc -o dpci8255.o dpci8255lib.c
> /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crt1.o(.text+0x18):
> In function `_start':
> : undefined reference to `main'
> collect2: ld returned 1 exit status
>
> The gcc manpage isn't that helpfull and I've now read thru it twice.

This should work for a single source file

]$ gcc -O2 -D__KERNEL__ -DMODULE -DHAVE_CONFIG_H -I/usr/src/linux/include -c dcpi8255.c

If your using SMP then you'll need to define that as well.

--
Eric Gaumer <[email protected]>


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2004-11-08 22:36:46

by Sam Ravnborg

[permalink] [raw]
Subject: Re: makeing a loadable module

On Sun, Nov 07, 2004 at 11:28:48PM -0500, Gene Heskett wrote:
> Greetings;
>
> I found some code I can play with/hack/etc, in the form of a loadable
> module and some testing driver programs, in 'dpci8255.tar.gz'.
>
> Unforch its for a slightly different card than the one I have, and
> once I've hacked the code to suit, I need to rebuild it.
>
> So whats the gcc command line to make just a bare, loadable module for
> say a 2.4.25 kernel? Obviously I'm missing something when it
> complains and quits, claiming there is no 'main' defined, which I
> don't think modules actually have one of those?
>
> What I'm trying to do (hey, no big dummy jokes please :)
>
> [root@coyote dist]# cc -o dpci8255.o dpci8255lib.c
> /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/../../../crt1.o(.text+0x18):
> In function `_start':
> : undefined reference to `main'
> collect2: ld returned 1 exit status

Create a small Makefile:
echo obj-m := dpci8255.o > Makefile

And use:
make -C $PATH_TO_KERNEL_SRC SUBDIRS=$PWD modules

This will give you the correct gcc commandline - adopted to actual
configuration of the kernel.
Any other way to compile a module is br0ken.

For 2.6 the above syntax works as well, but simpler versions exists.

Sam