[Xenomai] compiling kernel module with Xenomai support

[Xenomai] compiling kernel module with Xenomai support

[Tom Z]

Hi,

I am writing a kernel module that calls rt_task_add_hook() to add a hook 
when context switch occurs. I built a kernel module called 
*switch_hook.ko*, but when I /insmod switch_hook.ko/, it complains 
"*switch_hook: Unknown symbol rt_task_add_hook (err 0)*". I think I 
missed something during the build process (failed to include Xenomai 
source?) but I do not how to fix it. Below is my system settings, any 
help is greatly appreciated.
*Patched Linux kernel source* is at "/usr/src/linux-3.5.7"
*Xenomai source* is at "/usr/src/xenomai-2.6.2.1"
*Xenomai libraries and binaries* is at "/usr/xenomai"
*My kernel module source code* is at **"/home/tomz/switch_hook_mod/", 
and under this folder there are only two files: *Makefile* and 
*switch_hook.c*. Here is how I make this module, and Makefile and 
switch_hook.c's contents are attached as well:
/home/tomz/switch_hook_mod# *make EXTRA_CFLAGS="-I/usr/xenomai/include 
-D_GNU_SOURCE -D_REENTRANT -D__XENO" EXTRA_LDFLAGS="-lnative 
-L/usr/xenomai/lib -lxenomai -lpthread -lrt -lxenomai -lnative"*

*Makefile's content*
obj-m += switch_hook.o

all:
     make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
     make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

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

#include <native/task.h>
#include <native/timer.h>
#include  <rtdk.h>

void hook_func(void *cookie){
     printk(KERN_INFO "Context switch occured\n");
}

static int __init switch_hook_init(void)
{
     rt_print_auto_init(1);
     rt_printf("Add hook\n");
     rt_task_add_hook(T_HOOK_SWITCH, &hook_func);
     return 0;
}

static void __exit switch_hook_exit(void)
{
     printk(KERN_INFO "Goodbye\n");
}

module_init(switch_hook_init);
module_exit(switch_hook_exit);
//end of switch_hook.c

Re: [Xenomai] compiling kernel module with Xenomai support

[Paul]

On Thursday 14 March 2013, Tom Z wrote:
> Hi,
 ditto.
>
> I am writing a kernel module that calls rt_task_add_hook() to add a
> hook when context switch occurs. I built a kernel module called
> *switch_hook.ko*, but when I /insmod switch_hook.ko/, it complains
> "*switch_hook: Unknown symbol rt_task_add_hook (err 0)*". I think I

dmesg will probably show you have tainted your kernel by loading a 
non-GPL module.

> missed something during the build process (failed to include Xenomai
> source?) but I do not how to fix it. Below is my system settings, any
> help is greatly appreciated.
> *Patched Linux kernel source* is at "/usr/src/linux-3.5.7"
> *Xenomai source* is at "/usr/src/xenomai-2.6.2.1"
> *Xenomai libraries and binaries* is at "/usr/xenomai"
> *My kernel module source code* is at **"/home/tomz/switch_hook_mod/",
> and under this folder there are only two files: *Makefile* and
> *switch_hook.c*. Here is how I make this module, and Makefile and
> switch_hook.c's contents are attached as well:
> /home/tomz/switch_hook_mod# *make
> EXTRA_CFLAGS="-I/usr/xenomai/include -D_GNU_SOURCE -D_REENTRANT
> -D__XENO" EXTRA_LDFLAGS="-lnative -L/usr/xenomai/lib -lxenomai
> -lpthread -lrt -lxenomai -lnative"*

Ugly way of passing flags and prone to error.

>
> *Makefile's content*
> obj-m += switch_hook.o
# Use cflags instead of passing on the command line.
# Read Documentation/kbuild/makefiles.txt for other options.
cflags-y = $(shell xeno-config --skin native --cflags)
>
> all:
>      make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules
>
> clean:
>      make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean
>
> *switch_hook.c's content*
> #include <linux/module.h>    /* Needed by all modules */
> #include <linux/kernel.h>    /* Needed for KERN_INFO */
> #include <linux/init.h>        /* Needed for the macros */
>
> #include <native/task.h>
> #include <native/timer.h>
> #include  <rtdk.h>
>
> void hook_func(void *cookie){
>      printk(KERN_INFO "Context switch occured\n");
> }
>
> static int __init switch_hook_init(void)
> {
>      rt_print_auto_init(1);
>      rt_printf("Add hook\n");
>      rt_task_add_hook(T_HOOK_SWITCH, &hook_func);
>      return 0;
> }
>
> static void __exit switch_hook_exit(void)
> {
>      printk(KERN_INFO "Goodbye\n");
> }
>
> module_init(switch_hook_init);
> module_exit(switch_hook_exit);

MODULE_LICENSE("GPL"); /* See: linux/module.h for other valid options */
MODULE_AUTHOR("DRIVER_AUTHOR");	/* Who wrote this module? */
MODULE_DESCRIPTION("DRIVER_DESC");	/* What does this module do */

> //end of switch_hook.c
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