Question: kprobe fault handler

[Keshavamurthy, Anil S]

Hi,
	I am trying to support kprobe fault handler (on IA64 ) and
looking at the other architecture, I see they have added this call chain
notification in fault.c.

For example for i386 the code looks like

do_page_fault(....)
{

+		if (notify_die(DIE_PAGE_FAULT, "page_fault", regs,
error_code,
+					11, SIGSEGV) == NOTIFY_STOP)
+			return 0;

. . . . 
. . . 

}

Looking at this seems to be a bit heavyweight as we will be trying to
call this call chain notification for every page fault. I guess same
question was asked in the LKML mailing list. Do we know the overhead of
this?

Also, I would like to know how to test this feature where kprobe fault
handler 
will completely handle the page fault and return NOTIFY_STOP. Is there a
sample code for i386 that I can take a look at it?


Thanks,

-Anil Keshavamurthy
Sr. Software Engineer
Open Source Technology Center/SSG
Intel Corp.
(w) 503-712-4476