makeing a loadable module

makeing a loadable module

[Gene Heskett]

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."
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by Gene Heskett are:
Copyright 2004 by Maurice Eugene Heskett, all rights reserved.

Re: makeing a loadable module

[Eric Gaumer]

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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 <gaumerel@ecs.fullerton.edu>

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Re: makeing a loadable module

[Sam Ravnborg]

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