ARM: kprobes: Reject 16-bit Thumb SETEND, CPS and BKPT instructions

These are very rare and/or problematic to emulate so we will take the
easy option and disallow probing them (as does the existing ARM
implementation).

Rejecting these instructions doesn't actually require any entries in the
decoding table as it is the default case for instructions which aren't
found.

Signed-off-by: Jon Medhurst <tixy@yxit.co.uk>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>

arch/arm/kernel/kprobes-thumb.c

@@ -373,6 +373,10 @@ static const union decode_item t16_table_1011[] = {
 	/* IT				1011 1111 xxxx xxxx */
 	DECODE_CUSTOM	(0xff00, 0xbf00, t16_decode_it),
 
+	/* SETEND			1011 0110 010x xxxx */
+	/* CPS				1011 0110 011x xxxx */
+	/* BKPT				1011 1110 xxxx xxxx */
+	/* And unallocated instructions...		    */
 	DECODE_END
 };