Linux: modpost does not build anything

Posted by waffleman on Stack Overflow See other posts from Stack Overflow or by waffleman
Published on 2011-01-17T16:10:54Z Indexed on 2011/01/17 16:53 UTC
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Filed under:

linux

|

gcc

|

kernel-module

I am having problems getting any kernel modules to build on my machine. Whenever I build a module, modpost always says there are zero modules:

MODPOST 0 modules

To troubleshoot the problem, I wrote a test module (hello.c):

#include <linux/module.h>       /* Needed by all modules */
#include <linux/kernel.h>       /* Needed for KERN_INFO */
#include <linux/init.h>         /* Needed for the macros */

static int __init hello_start(void)
{
printk(KERN_INFO "Loading hello module...\n");
printk(KERN_INFO "Hello world\n");
return 0;
}

static void __exit hello_end(void)
{
printk(KERN_INFO "Goodbye Mr.\n");
}

module_init(hello_start);
module_exit(hello_end);

Here is the Makefile for the module:

obj-m = hello.o
KVERSION = $(shell uname -r)
all:
        make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) modules
clean:
        make -C /lib/modules/$(KVERSION)/build M=$(shell pwd) clean

When I build it on my machine, I get the following output:

make -C /lib/modules/2.6.32-27-generic/build M=/home/waffleman/tmp/mod-test modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.32-27-generic'
  CC [M]  /home/waffleman/tmp/mod-test/hello.o
  Building modules, stage 2.
  MODPOST 0 modules
make[1]: Leaving directory `/usr/src/linux-headers-2.6.32-27-generic'

When I make the module on another machine, it is successful:

make -C /lib/modules/2.6.24-27-generic/build M=/home/somedude/tmp/mod-test modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.24-27-generic'
  CC [M]  /home/somedude/tmp/mod-test/hello.o
  Building modules, stage 2.
  MODPOST 1 modules
  CC      /home/somedude/tmp/mod-test/hello.mod.o
  LD [M]  /home/somedude/tmp/mod-test/hello.ko
make[1]: Leaving directory `/usr/src/linux-headers-2.6.24-27-generic'

I looked for any relevant documentation about modpost, but found little. Anyone know how modpost decides what to build? Is there an environment that I am possibly missing?

BTW here is what I am running:

uname -a
Linux waffleman-desktop 2.6.32-27-generic #49-Ubuntu SMP Wed Dec 1 23:52:12 UTC 2010 i686 GNU/Linux

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