feat(rme): run BL2 in root world when FEAT_RME is enabled

This patch enables BL2 to run in root world (EL3) which is
needed as per the security model of RME-enabled systems.

Using the existing BL2_AT_EL3 TF-A build option is not convenient
because that option assumes TF-A BL1 doesn't exist, which is not
the case for RME-enabled systems. For the purposes of RME, we use
a normal BL1 image but we also want to run BL2 in EL3 as normally as
possible, therefore rather than use the special bl2_entrypoint
function in bl2_el3_entrypoint.S, we use a new bl2_entrypoint
function (in bl2_rme_entrypoint.S) which doesn't need reset or
mailbox initialization code seen in the el3_entrypoint_common macro.

The patch also cleans up bl2_el3_entrypoint.S, moving the
bl2_run_next_image function to its own file to avoid duplicating
code.

Signed-off-by: Zelalem Aweke <zelalem.aweke@arm.com>
Change-Id: I99821b4cd550cadcb701f4c0c4dc36da81c7ef55
diff --git a/bl2/bl2_main.c b/bl2/bl2_main.c
index d2de135..197c057 100644
--- a/bl2/bl2_main.c
+++ b/bl2/bl2_main.c
@@ -29,18 +29,18 @@
 #define NEXT_IMAGE	"BL32"
 #endif
 
-#if !BL2_AT_EL3
+#if BL2_AT_EL3
 /*******************************************************************************
- * Setup function for BL2.
+ * Setup function for BL2 when BL2_AT_EL3=1
  ******************************************************************************/
-void bl2_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
-	       u_register_t arg3)
+void bl2_el3_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
+		   u_register_t arg3)
 {
 	/* Perform early platform-specific setup */
-	bl2_early_platform_setup2(arg0, arg1, arg2, arg3);
+	bl2_el3_early_platform_setup(arg0, arg1, arg2, arg3);
 
 	/* Perform late platform-specific setup */
-	bl2_plat_arch_setup();
+	bl2_el3_plat_arch_setup();
 
 #if CTX_INCLUDE_PAUTH_REGS
 	/*
@@ -50,19 +50,18 @@
 	assert(is_armv8_3_pauth_present());
 #endif /* CTX_INCLUDE_PAUTH_REGS */
 }
-
-#else /* if BL2_AT_EL3 */
+#else /* BL2_AT_EL3 */
 /*******************************************************************************
- * Setup function for BL2 when BL2_AT_EL3=1.
+ * Setup function for BL2 when BL2_AT_EL3=0
  ******************************************************************************/
-void bl2_el3_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
-		   u_register_t arg3)
+void bl2_setup(u_register_t arg0, u_register_t arg1, u_register_t arg2,
+	       u_register_t arg3)
 {
 	/* Perform early platform-specific setup */
-	bl2_el3_early_platform_setup(arg0, arg1, arg2, arg3);
+	bl2_early_platform_setup2(arg0, arg1, arg2, arg3);
 
 	/* Perform late platform-specific setup */
-	bl2_el3_plat_arch_setup();
+	bl2_plat_arch_setup();
 
 #if CTX_INCLUDE_PAUTH_REGS
 	/*
@@ -115,7 +114,7 @@
 	measured_boot_finish();
 #endif /* MEASURED_BOOT */
 
-#if !BL2_AT_EL3
+#if !BL2_AT_EL3 && !ENABLE_RME
 #ifndef __aarch64__
 	/*
 	 * For AArch32 state BL1 and BL2 share the MMU setup.
@@ -140,7 +139,7 @@
 	 * be passed to next BL image as an argument.
 	 */
 	smc(BL1_SMC_RUN_IMAGE, (unsigned long)next_bl_ep_info, 0, 0, 0, 0, 0, 0);
-#else /* if BL2_AT_EL3 */
+#else /* if BL2_AT_EL3 || ENABLE_RME */
 	NOTICE("BL2: Booting " NEXT_IMAGE "\n");
 	print_entry_point_info(next_bl_ep_info);
 	console_flush();
@@ -153,5 +152,5 @@
 #endif /* ENABLE_PAUTH */
 
 	bl2_run_next_image(next_bl_ep_info);
-#endif /* BL2_AT_EL3 */
+#endif /* BL2_AT_EL3 && ENABLE_RME */
 }