[POWERPC] Transparently handle <.symbol> lookup for kprobes

When data symbols are not present in kernel image, user needs to add
dot(".") before function name explicitly, that he wants to probe in kprobe
module on ppc64.

for ex:-
When data symbols are missing on ppc64,
====================
[root@llm27lp1 ~]# cat /proc/kallsyms | grep do_fork
c00000000006283c T .do_fork
==============================
User needs add "." to "do_fork"

kp.symbol_name = ".do_fork";
============================

This makes kprobe modules unportable.  This fixes the problem.
Signed-off-by: Srinivasa Ds <srinivasa@in.ibm.com>
Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

include/asm-powerpc/kprobes.h

@@ -64,6 +64,12 @@ typedef unsigned int kprobe_opcode_t;
 				addr = *(kprobe_opcode_t **)addr;	\
 		} else if (name[0] != '.')				\
 			addr = *(kprobe_opcode_t **)addr;		\
+	} else {							\
+		char dot_name[KSYM_NAME_LEN+1];				\
+		dot_name[0] = '.';					\
+		dot_name[1] = '\0';					\
+		strncat(dot_name, name, KSYM_NAME_LEN);			\
+		addr = (kprobe_opcode_t *)kallsyms_lookup_name(dot_name); \
 	}								\
 }