s390/kprobes: allow kprobes only on known instructions

Since we have an in-kernel disassembler we can make sure that
there won't be any kprobes set on random data.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/dis.h b/arch/s390/include/asm/dis.h
index 4d0dffc..04a83f5 100644
--- a/arch/s390/include/asm/dis.h
+++ b/arch/s390/include/asm/dis.h
@@ -42,5 +42,11 @@
 void show_code(struct pt_regs *regs);
 void print_fn_code(unsigned char *code, unsigned long len);
 int insn_to_mnemonic(unsigned char *instruction, char *buf, unsigned int len);
+struct s390_insn *find_insn(unsigned char *code);
+
+static inline int is_known_insn(unsigned char *code)
+{
+	return !!find_insn(code);
+}
 
 #endif /* __ASM_S390_DIS_H__ */