build: add CFG_DYN_SHM_CAP config variable

This variable can disable reported capability
OPTEE_SMC_SEC_CAP_DYNAMIC_SHM.

But dynamic SHM remains fully operational, though. This can be used
for testing and debugging to emulate system, where dynamic SHM is not
supported.

Signed-off-by: Volodymyr Babchuk <vlad.babchuk@gmail.com>
Acked-by: Jerome Forissier <jerome.forissier@linaro.org>

core/arch/arm/tee/entry_fast.c

@@ -106,9 +106,11 @@ static void tee_entry_exchange_capabilities(struct thread_smc_args *args)
 	args->a0 = OPTEE_SMC_RETURN_OK;
 	args->a1 = OPTEE_SMC_SEC_CAP_HAVE_RESERVED_SHM;
 
+#if defined(CFG_DYN_SHM_CAP)
 	dyn_shm_en = core_mmu_nsec_ddr_is_defined();
 	if (dyn_shm_en)
 		args->a1 |= OPTEE_SMC_SEC_CAP_DYNAMIC_SHM;
+#endif
 
 	IMSG("Dynamic shared memory is %sabled", dyn_shm_en ? "en" : "dis");
 }

mk/config.mk

@@ -263,3 +263,10 @@ CFG_SECURE_DATA_PATH ?= n
 # so its value represents log2(cores/cluster).
 # Default is 2**(2) = 4 cores per cluster.
 CFG_CORE_CLUSTER_SHIFT ?= 2
+
+# Do not report to NW that dynamic shared memory (shared memory outside
+# predefined region) is enabled.
+# Note that you can disable this feature for debug purposes. OP-TEE will not
+# report to Normal World that it support dynamic SHM. But, nevertheles it
+# will accept dynamic SHM buffers.
+CFG_DYN_SHM_CAP ?= y