This patch helps developers to trap at almost any kernel code address,
specifying a handler routine to be invoked when the breakpoint is hit.  

Useful for analysing the Linux kernel by collecting debugging information
non-disruptively.  Employs single-stepping out-of-line to avoid probe
misses on SMP and may be especially useful in aiding debugging elusive
races and problems on live systems.  More elaborate dynamic tracing tools
such as DProbes can be built over the kprobes interface.


Helps developers to trap at almost any kernel code address, specifying a
handler routine to be invoked when the breakpoint is hit.  Useful for
analysing the Linux kernel by collecting debugging information
non-disruptively.  Employs single-stepping out-of-line to avoid probe
misses on SMP and may be especially useful in aiding debugging elusive
races and problems on live systems.  More elaborate dynamic tracing tools
such as DProbes can be built over the kprobes interface.

Sample usage:
	To place a probe on __blockdev_direct_IO:
	static int probe_handler(struct kprobe *p, struct pt_regs *)
	{
		... whatever ...
	}
	struct kprobe kp = {
		.addr = __blockdev_direct_IO,
		.pre_handler = probe_handler
	};
	register_kprobe(&kp);
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>