Dereferencing simple pointers

[daniel-kay3 at arcor dot de]

Hello Folks,
I am playing around with systemtap and am quite impressed. But there is one thing that confuses me. Is there any way that I can derefernce a single pointer from a function parameter inside a probe?

Example:

# Function from current Kernel (drivers/char/random.c:1049):
urandom_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
{
       return extract_entropy_user(&nonblocking_pool, buf, nbytes);
}

# My Probe Attempt without success:
probe kernel.function("urandom_read") {
        printf("%s\n", *($ppos));
}

I can't believe that this isn't possible...

Thanks in advance,
Daniel Kay