Re: Signals/ Communication from kernel to user!

From: Der Herr Hofrat (der.herr_at_hofr.at)
Date: 02/28/05

  • Next message: Stelian Pop: "Re: [patch 3/2] drivers/char/vt.c: remove unnecessary code" 
    To: Ravindra Nadgauda <rnadgauda@velankani.com>
Date:	Mon, 28 Feb 2005 20:13:30 +0100 (CET)

    >
    >
    > Hello,
    > We wanted to establish a communication from kernel module (possibly a
    > driver) to a user level process.
    >
    > Wanted to know whether signals can be used for this purpose OR there any
    > other (better) methods of communication??
    >
    a bit brute force but you can simply run through the task list and kick
    the pid of your user-space app (example for 2.4 kernel):

    hofrat

    ---snip---
    /*
     * Copywrite 2002 Der Herr Hofrat
     * License GPL V2
     * Author der.herr@hofr.at
     */
    /*
     * run through the task list of linux search for the passed pid and send it
     * a SIGKILL . run as insmod pid=# to send process with pid # a kill signal
     */

    #include <bits/signum.h> /* signal number macros SIGHUP etc. */
    #include <linux/kernel.h> /* printk level */
    #include <linux/module.h> /* kernel version etc. */
    #include <linux/sched.h> /* task_struct */

    MODULE_LICENSE("GPL v2");
    MODULE_AUTHOR("Der Herr Hofrat");
    MODULE_DESCRIPTION("Signal to a user-space app from a kernel module");

    int pid=0;
    MODULE_PARM(pid,"i");

    int
    ksignal(int pid,int signum)
    {
            struct task_struct *p;

            /* run through the task list of linux until we find our pid */
            for_each_task(p){
                    if(p->pid == pid){
                            printk("sending signal %d for pid %d\n",signum,(int)p->pid);
                            /* don't have a sig_info struct to send along - pass 0 */
                            return send_sig(signum,p,0);
                    }
            }
            /* did not find the requested pid */
            return -1;
    }

    int
    init_module(void)
    {
            /* send pid a SIGKILL */
            ksignal(pid,SIGKILL);
            return 0;
    }

    void
    cleanup_module(void)
    {
            printk("out of here\n");
    }
    -
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  • Next message: Stelian Pop: "Re: [patch 3/2] drivers/char/vt.c: remove unnecessary code"

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