kprobes: prevent probing of preempt_schedule()

Prohibit users from probing preempt_schedule().  One way of prohibiting the
user from probing functions is by marking such functions with __kprobes.  But
this method doesn't work for those functions, which are already marked to
different section like preempt_schedule() (belongs to __sched section).  So we
use blacklist approach to refuse user from probing these functions.

In blacklist approach we populate the blacklisted function's starting address
and its size in kprobe_blacklist structure.  Then we verify the user specified
address against start and end of the blacklisted function.  So any attempt to
register probe on blacklisted functions will be rejected.

[akpm@linux-foundation.org: build fix]
[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Srinivasa DS <srinivasa@in.ibm.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Jim Keniston <jkenisto@us.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>