RAS: Introduce handler for EL3 EAs

External Aborts while executing in EL3 is fatal in nature. This patch
allows for the platform to define a handler for External Aborts received
while executing in EL3. A default implementation is added which falls
back to platform unhandled exception.

Change-Id: I466f2c8113a33870f2c7d2d8f2bf20437d9fd354
Signed-off-by: Jeenu Viswambharan <jeenu.viswambharan@arm.com>

bl31/aarch64/runtime_exceptions.S

@@ -213,7 +213,7 @@ end_vector_entry fiq_sp_el0
 
 
 vector_entry serror_sp_el0
-	b	report_unhandled_exception
+	no_ret	plat_handle_el3_ea
 end_vector_entry serror_sp_el0
 
 	/* ---------------------------------------------------------------------
@@ -239,7 +239,7 @@ vector_entry fiq_sp_elx
 end_vector_entry fiq_sp_elx
 
 vector_entry serror_sp_elx
-	b	report_unhandled_exception
+	no_ret	plat_handle_el3_ea
 end_vector_entry serror_sp_elx
 
 	/* ---------------------------------------------------------------------

plat/common/aarch64/platform_helpers.S

@@ -22,6 +22,7 @@
 
 	.weak	plat_handle_uncontainable_ea
 	.weak	plat_handle_double_fault
+	.weak	plat_handle_el3_ea
 
 #if !ENABLE_PLAT_COMPAT
 	.globl	platform_get_core_pos
@@ -212,3 +213,11 @@ endfunc plat_handle_uncontainable_ea
 func plat_handle_double_fault
 	b	report_unhandled_exception
 endfunc plat_handle_double_fault
+
+	/* -----------------------------------------------------
+	 * Platform handler for EL3 External Abort.
+	 * -----------------------------------------------------
+	 */
+func plat_handle_el3_ea
+	b	report_unhandled_exception
+endfunc plat_handle_el3_ea