On Mon, Jan 14, 2002 at 01:29:21PM -0500, Israel Fdez wrote:
> I'm developing a file auditor kernel module. The auditing tasks are performed
> by a userland daemond, and the sys_open and sys_exec system calls are
> intercepted by the kernel module. I was using IPC V messages to communicate
> both hte LKm anda the daemon, but I realize that they are not designed to run
> within the kernel space. Now I'm tring with a /proc file, but, this is my
> question:
You actually want a real device driver, /proc wasn't designed to be
abused like that.
> Whow can I make my daemond to wait a "signal" or something else from the
> kernel module. This "signal" should contain the file path to be audited.
Use a semaphore (or some other kind of locking mechanism).
struct semaphore sem;
/* device "read" function */
static ssize_t read_func(struct file *filp, char *buf, size_t count,
loff_t *f_pos)
{
if(down_interruptible(&sem))
return -ERESTARTSYS;
/* copy data to userland */
return number of bytes written to userland;
}
/* other part of the driver that wants to wakeup userland (interrupt
/* handler, for example) */
up(&sem);
/* initialisation at module load*/
sema_init(&sem, 1);
Userland daemon reads the device, but blocks on the semaphore. Userland
gets woken up either when it receives a signal (hence the
down_interruptible()), or when the semaphore gets signaled with up()
(probably when data comes available). Again, see "linux device drivers,
2nd edition".
Erik
--
J.A.K. (Erik) Mouw, Information and Communication Theory Group, Faculty
of Information Technology and Systems, Delft University of Technology,
PO BOX 5031, 2600 GA Delft, The Netherlands Phone: +31-15-2783635
Fax: +31-15-2781843 Email: J.A.K.Mouw@its.tudelft.nl
WWW: http://www-ict.its.tudelft.nl/~erik/
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