feat(drtm): introduce drtm dynamic launch function

This function is placeholder for checking all the necessary conditions
before doing drtm dynamic launch.
In this patch following conditions are checked (based on Table 31 of
DRTM spec beta0), rest of the conditions will be added in later
patches.
 - Only boot PE is online
 - Caller execution state is AArch64
 - Caller exception level is NS-EL2 or NS-EL1

Signed-off-by: Manish Pandey <manish.pandey2@arm.com>
Change-Id: I622b946bc191bb39f828831336ceafbc10834c19

services/std_svc/drtm/drtm_main.c

@@ -19,6 +19,7 @@
 #include <common/runtime_svc.h>
 #include <drivers/auth/crypto_mod.h>
 #include "drtm_main.h"
+#include <lib/psci/psci_lib.h>
 #include <lib/xlat_tables/xlat_tables_v2.h>
 #include <plat/common/platform.h>
 #include <services/drtm_svc.h>
@@ -149,6 +150,72 @@ static inline uint64_t drtm_features_tcb_hashes(void *ctx)
 		 plat_drtm_features.tcb_hash_features);
 }
 
+static enum drtm_retc drtm_dl_check_caller_el(void *ctx)
+{
+	uint64_t spsr_el3 = read_ctx_reg(get_el3state_ctx(ctx), CTX_SPSR_EL3);
+	uint64_t dl_caller_el;
+	uint64_t dl_caller_aarch;
+
+	dl_caller_el = spsr_el3 >> MODE_EL_SHIFT & MODE_EL_MASK;
+	dl_caller_aarch = spsr_el3 >> MODE_RW_SHIFT & MODE_RW_MASK;
+
+	/* Caller's security state is checked from drtm_smc_handle function */
+
+	/* Caller can be NS-EL2/EL1 */
+	if (dl_caller_el == MODE_EL3) {
+		ERROR("DRTM: invalid launch from EL3\n");
+		return DENIED;
+	}
+
+	if (dl_caller_aarch != MODE_RW_64) {
+		ERROR("DRTM: invalid launch from non-AArch64 execution state\n");
+		return DENIED;
+	}
+
+	return SUCCESS;
+}
+
+static enum drtm_retc drtm_dl_check_cores(void)
+{
+	bool running_on_single_core;
+	uint64_t this_pe_aff_value = read_mpidr_el1() & MPIDR_AFFINITY_MASK;
+
+	if (this_pe_aff_value != plat_drtm_features.boot_pe_id) {
+		ERROR("DRTM: invalid launch on a non-boot PE\n");
+		return DENIED;
+	}
+
+	running_on_single_core = psci_is_last_on_cpu_safe();
+	if (!running_on_single_core) {
+		ERROR("DRTM: invalid launch due to non-boot PE not being turned off\n");
+		return DENIED;
+	}
+
+	return SUCCESS;
+}
+
+static uint64_t drtm_dynamic_launch(uint64_t x1, void *handle)
+{
+	enum drtm_retc ret = SUCCESS;
+
+	/* Ensure that only boot PE is powered on */
+	ret = drtm_dl_check_cores();
+	if (ret != SUCCESS) {
+		SMC_RET1(handle, ret);
+	}
+
+	/*
+	 * Ensure that execution state is AArch64 and the caller
+	 * is highest non-secure exception level
+	 */
+	ret = drtm_dl_check_caller_el(handle);
+	if (ret != SUCCESS) {
+		SMC_RET1(handle, ret);
+	}
+
+	SMC_RET1(handle, ret);
+}
+
 uint64_t drtm_smc_handler(uint32_t smc_fid,
 			  uint64_t x1,
 			  uint64_t x2,
@@ -268,7 +335,7 @@ uint64_t drtm_smc_handler(uint32_t smc_fid,
 
 	case ARM_DRTM_SVC_DYNAMIC_LAUNCH:
 		INFO("DRTM service handler: dynamic launch\n");
-		SMC_RET1(handle, SMC_OK);
+		return drtm_dynamic_launch(x1, handle);
 		break;	/* not reached */
 
 	case ARM_DRTM_SVC_CLOSE_LOCALITY: