TSP: Fix GCC 11.0.0 compilation error.

This patch fixes the following compilation error
reported by aarch64-none-elf-gcc 11.0.0:

bl32/tsp/tsp_main.c: In function 'tsp_smc_handler':
bl32/tsp/tsp_main.c:393:9: error: 'tsp_get_magic'
 accessing 32 bytes in a region of size 16
 [-Werror=stringop-overflow=]
  393 |         tsp_get_magic(service_args);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
bl32/tsp/tsp_main.c:393:9: note: referencing argument 1
 of type 'uint64_t *' {aka 'long long unsigned int *'}
In file included from bl32/tsp/tsp_main.c:19:
bl32/tsp/tsp_private.h:64:6: note: in a call to function 'tsp_get_magic'
   64 | void tsp_get_magic(uint64_t args[4]);
      |      ^~~~~~~~~~~~~

by changing declaration of tsp_get_magic function from
void tsp_get_magic(uint64_t args[4]);
to
uint128_t tsp_get_magic(void);
which returns arguments directly in x0 and x1 registers.

In bl32\tsp\tsp_main.c the current tsp_smc_handler()
implementation calls tsp_get_magic(service_args);
, where service_args array is decl...

bl32/tsp/aarch64/tsp_request.S

 /*
- * Copyright (c) 2013-2014, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -9,28 +9,19 @@
 
 	.globl tsp_get_magic
 
-
 /*
  * This function raises an SMC to retrieve arguments from secure
  * monitor/dispatcher, saves the returned arguments the array received in x0,
  * and then returns to the caller
  */
 func tsp_get_magic
-	/* Save address to stack */
-	stp	x0, xzr, [sp, #-16]!
-
 	/* Load arguments */
 	ldr	w0, _tsp_fid_get_magic
 
 	/* Raise SMC */
 	smc	#0
 
-	/* Restore address from stack */
-	ldp	x4, xzr, [sp], #16
-
-	/* Store returned arguments to the array */
-	stp	x0, x1, [x4, #0]
-
+	/* Return arguments in x1:x0 */
 	ret
 endfunc tsp_get_magic
 

bl32/tsp/tsp_main.c

 /*
- * Copyright (c) 2013-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -363,8 +363,10 @@ tsp_args_t *tsp_smc_handler(uint64_t func,
 			       uint64_t arg6,
 			       uint64_t arg7)
 {
+	uint128_t service_args;
+	uint64_t service_arg0;
+	uint64_t service_arg1;
 	uint64_t results[2];
-	uint64_t service_args[2];
 	uint32_t linear_id = plat_my_core_pos();
 
 	/* Update this cpu's statistics */
@@ -387,10 +389,12 @@ tsp_args_t *tsp_smc_handler(uint64_t func,
 	results[1] = arg2;
 
 	/*
-	 * Request a service back from dispatcher/secure monitor. This call
-	 * return and thereafter resume execution
+	 * Request a service back from dispatcher/secure monitor.
+	 * This call returns and thereafter resumes execution.
 	 */
-	tsp_get_magic(service_args);
+	service_args = tsp_get_magic();
+	service_arg0 = (uint64_t)service_args;
+	service_arg1 = (uint64_t)(service_args >> 64U);
 
 #if CTX_INCLUDE_MTE_REGS
 	/*
@@ -403,20 +407,20 @@ tsp_args_t *tsp_smc_handler(uint64_t func,
 	/* Determine the function to perform based on the function ID */
 	switch (TSP_BARE_FID(func)) {
 	case TSP_ADD:
-		results[0] += service_args[0];
-		results[1] += service_args[1];
+		results[0] += service_arg0;
+		results[1] += service_arg1;
 		break;
 	case TSP_SUB:
-		results[0] -= service_args[0];
-		results[1] -= service_args[1];
+		results[0] -= service_arg0;
+		results[1] -= service_arg1;
 		break;
 	case TSP_MUL:
-		results[0] *= service_args[0];
-		results[1] *= service_args[1];
+		results[0] *= service_arg0;
+		results[1] *= service_arg1;
 		break;
 	case TSP_DIV:
-		results[0] /= service_args[0] ? service_args[0] : 1;
-		results[1] /= service_args[1] ? service_args[1] : 1;
+		results[0] /= service_arg0 ? service_arg0 : 1;
+		results[1] /= service_arg1 ? service_arg1 : 1;
 		break;
 	default:
 		break;

bl32/tsp/tsp_private.h

 /*
- * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -61,7 +61,7 @@ typedef struct tsp_args {
  */
 CASSERT(TSP_ARGS_SIZE == sizeof(tsp_args_t), assert_sp_args_size_mismatch);
 
-void tsp_get_magic(uint64_t args[4]);
+uint128_t tsp_get_magic(void);
 
 tsp_args_t *tsp_cpu_resume_main(uint64_t max_off_pwrlvl,
 				uint64_t arg1,