Small problem, Can anybody help me?

Small problem, Can anybody help me?

[Srinivas G.]

Hi,

I have written a small hello.c program in the Linux Kernel version
2.4.18-3.

The code is as follows.
-----------------------


define MODULE
#include <linux/module.h>
#include <linux/init.h>

MODULE_LICENSE("GPL");

int Test_init(void)
{
	printk("<1> Hello World\n");
	return 0;
}

void Test_cleanup(void)
{
	printk("<1> Good bye\n");
}

module_init(Test_init);
module_exit(Test_cleanup);


I compiled it under same kernel version that is 2.4.18-3. It was showing
the following errors.

In file included from hello.c:2:
/usr/include/linux/module.h:60: parse error before `atomic_t'
/usr/include/linux/module.h:60: warning: no semicolon at end of struct
or union
/usr/include/linux/module.h:60: warning: no semicolon at end of struct
or union
/usr/include/linux/module.h:62: parse error before `}'
/usr/include/linux/module.h:62: warning: data definition has no type or
storage class
/usr/include/linux/module.h:91: parse error before `}'


The errors came due to a mistake in linux header file. Is it so...

Thanks in advance for any help you can come up with.

Regards,

Srinivas G

Re: Small problem, Can anybody help me?

[Erik Mouw]

On Thu, May 06, 2004 at 07:31:56PM +0530, Srinivas G. wrote:
> I have written a small hello.c program in the Linux Kernel version
> 2.4.18-3.

Ancient kernel with lots of known bugs and security issues. You'd
rather upgrade.

> The code is as follows.
> -----------------------
> 
> 
> define MODULE

The idea is to put that definition on the gcc command line.

> #include <linux/module.h>
> #include <linux/init.h>

You're missing #include <linux/kernel.h> 

> MODULE_LICENSE("GPL");
> 
> int Test_init(void)
> {
> 	printk("<1> Hello World\n");

Use KERN_ALERT instead of "<1>". We have #defines for a reason: if we
change the definition tomorrow, your source will still work. So use:

  printk(KERN_ALERT "Hello, world!\n");

> 	return 0;
> }
> 
> void Test_cleanup(void)
> {
> 	printk("<1> Good bye\n");
> }
> 
> module_init(Test_init);
> module_exit(Test_cleanup);
> 
> 
> I compiled it under same kernel version that is 2.4.18-3. It was showing
> the following errors.
> 
> In file included from hello.c:2:
> /usr/include/linux/module.h:60: parse error before `atomic_t'
  ^^^^^^^^^^^^
You're compiling against libc headers instead of kernel headers. See:

  http://www.kernelnewbies.org/faq/index.php3#headers

The way to compile a module on linux 2.4 is:

  gcc -O2 -Wall -I/path/to/kernel/include/directory -D__KERNEL__ -DMODULE -c hello.c


Erik

-- 
+-- Erik Mouw -- www.harddisk-recovery.com -- +31 70 370 12 90 --
| Lab address: Delftechpark 26, 2628 XH, Delft, The Netherlands

Re: Small problem, Can anybody help me?

[Dave Jones]

On Thu, May 06, 2004 at 07:31:56PM +0530, Srinivas G. wrote:

 > I compiled it under same kernel version that is 2.4.18-3. It was showing
 > the following errors.
 > 
 > In file included from hello.c:2:
 > /usr/include/linux/module.h:60: parse error before `atomic_t'
 > /usr/include/linux/module.h:60: warning: no semicolon at end of struct
 > or union
 > /usr/include/linux/module.h:60: warning: no semicolon at end of struct
 > or union
 > /usr/include/linux/module.h:62: parse error before `}'
 > /usr/include/linux/module.h:62: warning: data definition has no type or
 > storage class
 > /usr/include/linux/module.h:91: parse error before `}'

You're trying to include userspace headers into a kernel module.
This won't fly.

 > The errors came due to a mistake in linux header file. Is it so...
 > 
 > Thanks in advance for any help you can come up with.

Last week you claimed "Linux has broken spinlocks", this week "broken includes".
I suggest a trip to http://www.kernelnewbies.org/ may be in order
before you tackle anything more complicated than a helloworld module.

		Dave

Re: Small problem, Can anybody help me?

[Richard B. Johnson]

On Thu, 6 May 2004, Srinivas G. wrote:

>
> Hi,
>
> I have written a small hello.c program in the Linux Kernel version
> 2.4.18-3.
>
> The code is as follows.
> -----------------------
>
>
> define MODULE

#define __KERNEL__

#include <linux/kernel.h>

> #include <linux/module.h>
> #include <linux/init.h>
>


Cheers,
Dick Johnson
Penguin : Linux version 2.4.26 on an i686 machine (5557.45 BogoMips).
            Note 96.31% of all statistics are fiction.

Re: Small problem, Can anybody help me?

[David Woodhouse]

On Thu, 2004-05-06 at 16:28 +0200, Erik Mouw wrote:
> The way to compile a module on linux 2.4 is:
> 
>   gcc -O2 -Wall -I/path/to/kernel/include/directory -D__KERNEL__ -DMODULE -c hello.c

That doesn't always work. It gets the CFLAGS wrong. You should always
use
	make -C $KERNELDIR SUBDIRS=`pwd` modules


-- 
dwmw2