TSP: Enable pointer authentication support

The size increase after enabling options related to ARMv8.3-PAuth is:

+----------------------------+-------+-------+-------+--------+
|                            |  text |  bss  |  data | rodata |
+----------------------------+-------+-------+-------+--------+
| CTX_INCLUDE_PAUTH_REGS = 1 |   +40 |   +0  |   +0  |   +0   |
|                            |  0.4% |       |       |        |
+----------------------------+-------+-------+-------+--------+
| ENABLE_PAUTH = 1           |  +352 |    +0 |  +16  |   +0   |
|                            |  3.1% |       | 15.8% |        |
+----------------------------+-------+-------+-------+--------+

Results calculated with the following build configuration:

    make PLAT=fvp SPD=tspd DEBUG=1 \
    SDEI_SUPPORT=1                 \
    EL3_EXCEPTION_HANDLING=1       \
    TSP_NS_INTR_ASYNC_PREEMPT=1    \
    CTX_INCLUDE_PAUTH_REGS=1       \
    ENABLE_PAUTH=1

Change-Id: I6cc1fe0b2345c547dcef66f98758c4eb55fe5ee4
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
diff --git a/bl32/tsp/tsp.mk b/bl32/tsp/tsp.mk
index 4ea3dfb..b1fe7ff 100644
--- a/bl32/tsp/tsp.mk
+++ b/bl32/tsp/tsp.mk
@@ -1,5 +1,5 @@
 #
-# Copyright (c) 2013-2016, ARM Limited and Contributors. All rights reserved.
+# Copyright (c) 2013-2019, ARM Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -17,6 +17,11 @@
 
 BL32_LINKERFILE		:=	bl32/tsp/tsp.ld.S
 
+# This flag determines whether pointer authentication is used in the TSP or not
+ifeq ($(ENABLE_PAUTH),1)
+BL32_CFLAGS		+=	-msign-return-address=non-leaf
+endif
+
 # This flag determines if the TSPD initializes BL32 in tspd_init() (synchronous
 # method) or configures BL31 to pass control to BL32 instead of BL33
 # (asynchronous method).