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Old 11-06-2004, 08:42 PM   #1
mathman0
LQ Newbie
 
Registered: Oct 2004
Distribution: Fedor Core 2
Posts: 15

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compiling a module with gcc


writing a simple module trying to learn about writing device drivers...but i cant seem to get my code to compile properly
hello_module.c:
Code:
#include <linux/module.h>
                                                                             
#if defined(CONFIG_SMP)
#define __SMP__
#endif
                                                                             
#if defined(CONFIG_MODVERSIONS)
#define MODVERSIONS
#include <linux/modversions.h>
#endif
                                                                             
#include <linux/kernel.h>
                                                                             
int init_module(void)
{
        printk("<7>Hello kernel!\n");
        return 0;
}
                                                                             
void cleanup_module(void)
{
        printk("<7>Good-bye kernel!\n");
}
however when i try to compile and insert it i get this:
[root@localhost root]# gcc -D __KERNEL -D MODULE -O2 -W -Wall -c hello_module.c
hello_module.c: In function `init_module':
hello_module.c:16: warning: implicit declaration of function `printk'
[root@localhost root]# insmod hello_module.o
insmod: error inserting 'hello_module.o': -1 Invalid module format

if anyone could point me in the right direction it'd be greatly appreciated

23,1 All
 
Old 11-06-2004, 10:21 PM   #2
foo_bar_foo
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Registered: Jun 2004
Posts: 2,553

Rep: Reputation: 53
well for one thing fedora 2 kernel (modern) uses .ko modules
have no idea if they really differ from regular object files though ?????
first try -- just rename it.
 
Old 11-06-2004, 11:46 PM   #3
mathman0
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Registered: Oct 2004
Distribution: Fedor Core 2
Posts: 15

Original Poster
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well thanks for the info,renaming it however didn't work....but need to look into why they're doing this............heard alot of good things about FC2 but not that impressed
 
Old 11-06-2004, 11:48 PM   #4
mathman0
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Registered: Oct 2004
Distribution: Fedor Core 2
Posts: 15

Original Poster
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found a few errors in my command,am now using
[root@localhost root]# gcc -D__KERNEL__ -D__SMP__ -DMODULE -DMODVERSIONS -I/lib/modules/2.6.5-1.358/build/include -Wall -O2 -o hello_module.o -c hello_module.c
In file included from /lib/modules/2.6.5-1.358/build/include/asm/processor.h:18,
from /lib/modules/2.6.5-1.358/build/include/asm/thread_info.h:16,
from /lib/modules/2.6.5-1.358/build/include/linux/thread_info.h:21,
from /lib/modules/2.6.5-1.358/build/include/linux/spinlock.h:12,
from /lib/modules/2.6.5-1.358/build/include/linux/capability.h:45,
from /lib/modules/2.6.5-1.358/build/include/linux/sched.h:7, from /lib/modules/2.6.5-1.358/build/include/linux/module.h:10,
from hello_module.c:1:
/lib/modules/2.6.5-1.358/build/include/asm/system.h: In function `__set_64bit_var':
/lib/modules/2.6.5-1.358/build/include/asm/system.h:193: warning: dereferencing type-punned pointer will break strict-aliasing rules
/lib/modules/2.6.5-1.358/build/include/asm/system.h:193: warning: dereferencing type-punned pointer will break strict-aliasing rules

but still the same error from insmod
 
Old 11-07-2004, 02:19 PM   #5
foo_bar_foo
Senior Member
 
Registered: Jun 2004
Posts: 2,553

Rep: Reputation: 53
Quote:
Originally posted by mathman0
...but need to look into why they're doing this...........
new kernel is a good think you just have an old example trythis
Code:
    #include <linux/init.h>
    #include <linux/module.h>
    #include <linux/kernel.h>

    static int hello_init(void)
    {
        printk(KERN_ALERT "Hello, world\n");
        return 0;
    }

    static void hello_exit(void)
    {
        printk(KERN_ALERT "Goodbye, cruel world\n");
    }

    module_init(hello_init);
    module_exit(hello_exit);
Makefile
Code:
obj-m += hello.o
default:
make -C /lib/modules/$(shell uname -r)/build/ SUBDIRS=$(PWD) modules
put a TAB before make in the Makefile

sorry i cant try this to see if it works cause my kernel is very different (compiled with icc)
 
Old 11-07-2004, 04:13 PM   #6
mathman0
LQ Newbie
 
Registered: Oct 2004
Distribution: Fedor Core 2
Posts: 15

Original Poster
Rep: Reputation: 0
thank you,it now compiles and after inserting operated fine,now i can move on to read more about device drivers thank you
 
  


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