ARM: 9071/1: uprobes: Don't hook on thumb instructions

Since uprobes is not supported for thumb, check that the thumb bit is
not set when matching the uprobes instruction hooks.

The Arm UDF instructions used for uprobes triggering
(UPROBE_SWBP_ARM_INSN and UPROBE_SS_ARM_INSN) coincidentally share the
same encoding as a pair of unallocated 32-bit thumb instructions (not
UDF) when the condition code is 0b1111 (0xf). This in effect makes it
possible to trigger the uprobes functionality from thumb, and at that
using two unallocated instructions which are not permanently undefined.

Signed-off-by: Fredrik Strupe <fredrik@strupe.net>
Cc: stable@vger.kernel.org
Fixes: c7edc9e3

 ("ARM: add uprobes support")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>