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/bl1/aarch64/bl1_context_mgmt.c b/bl1/aarch64/bl1_context_mgmt.c
index 2a8d58e..b9a7e5b 100644
--- a/bl1/aarch64/bl1_context_mgmt.c
+++ b/bl1/aarch64/bl1_context_mgmt.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2021, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -16,6 +16,7 @@
 
 /* Following contains the cpu context pointers. */
 static void *bl1_cpu_context_ptr[2];
+entry_point_info_t *bl2_ep_info;
 
 
 void *cm_get_context(uint32_t security_state)
@@ -30,6 +31,40 @@
 	bl1_cpu_context_ptr[security_state] = context;
 }
 
+#if ENABLE_RME
+/*******************************************************************************
+ * This function prepares the entry point information to run BL2 in Root world,
+ * i.e. EL3, for the case when FEAT_RME is enabled.
+ ******************************************************************************/
+void bl1_prepare_next_image(unsigned int image_id)
+{
+	image_desc_t *bl2_desc;
+
+	assert(image_id == BL2_IMAGE_ID);
+
+	/* Get the image descriptor. */
+	bl2_desc = bl1_plat_get_image_desc(BL2_IMAGE_ID);
+	assert(bl2_desc != NULL);
+
+	/* Get the entry point info. */
+	bl2_ep_info = &bl2_desc->ep_info;
+
+	bl2_ep_info->spsr = (uint32_t)SPSR_64(MODE_EL3, MODE_SP_ELX,
+						DISABLE_ALL_EXCEPTIONS);
+
+	/*
+	 * Flush cache since bl2_ep_info is accessed after MMU is disabled
+	 * before jumping to BL2.
+	 */
+	flush_dcache_range((uintptr_t)bl2_ep_info, sizeof(entry_point_info_t));
+
+	/* Indicate that image is in execution state. */
+	bl2_desc->state = IMAGE_STATE_EXECUTED;
+
+	/* Print debug info and flush the console before running BL2. */
+	print_entry_point_info(bl2_ep_info);
+}
+#else
 /*******************************************************************************
  * This function prepares the context for Secure/Normal world images.
  * Normal world images are transitioned to EL2(if supported) else EL1.
@@ -93,3 +128,4 @@
 
 	print_entry_point_info(next_bl_ep);
 }
+#endif /* ENABLE_RME */
diff --git a/bl1/aarch64/bl1_entrypoint.S b/bl1/aarch64/bl1_entrypoint.S
index 00f2718..f61c060 100644
--- a/bl1/aarch64/bl1_entrypoint.S
+++ b/bl1/aarch64/bl1_entrypoint.S
@@ -1,13 +1,15 @@
 /*
- * Copyright (c) 2013-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2021, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
 #include <arch.h>
+#include <common/bl_common.h>
 #include <el3_common_macros.S>
 
 	.globl	bl1_entrypoint
+	.globl	bl1_run_bl2_in_root
 
 
 	/* -----------------------------------------------------
@@ -66,5 +68,41 @@
 	 * Do the transition to next boot image.
 	 * --------------------------------------------------
 	 */
+#if ENABLE_RME
+	b	bl1_run_bl2_in_root
+#else
 	b	el3_exit
+#endif
 endfunc bl1_entrypoint
+
+	/* -----------------------------------------------------
+	 * void bl1_run_bl2_in_root();
+	 * This function runs BL2 in root/EL3 when RME is enabled.
+	 * -----------------------------------------------------
+	 */
+
+func bl1_run_bl2_in_root
+	/* read bl2_ep_info */
+	adrp	x20, bl2_ep_info
+	add	x20, x20, :lo12:bl2_ep_info
+	ldr	x20, [x20]
+
+	/* ---------------------------------------------
+	 * MMU needs to be disabled because BL2 executes
+	 * in EL3. It will initialize the address space
+	 * according to its own requirements.
+	 * ---------------------------------------------
+	 */
+	bl	disable_mmu_icache_el3
+	tlbi	alle3
+
+	ldp	x0, x1, [x20, #ENTRY_POINT_INFO_PC_OFFSET]
+	msr	elr_el3, x0
+	msr	spsr_el3, x1
+
+	ldp	x6, x7, [x20, #(ENTRY_POINT_INFO_ARGS_OFFSET + 0x30)]
+	ldp	x4, x5, [x20, #(ENTRY_POINT_INFO_ARGS_OFFSET + 0x20)]
+	ldp	x2, x3, [x20, #(ENTRY_POINT_INFO_ARGS_OFFSET + 0x10)]
+	ldp	x0, x1, [x20, #(ENTRY_POINT_INFO_ARGS_OFFSET + 0x0)]
+	exception_return
+endfunc bl1_run_bl2_in_root
diff --git a/bl1/bl1_private.h b/bl1/bl1_private.h
index 2cfeeea..e119ba7 100644
--- a/bl1/bl1_private.h
+++ b/bl1/bl1_private.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2013-2021, Arm Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -11,6 +11,8 @@
 
 #include <common/bl_common.h>
 
+extern entry_point_info_t *bl2_ep_info;
+
 /******************************************
  * Function prototypes
  *****************************************/
@@ -18,6 +20,7 @@
 void bl1_arch_next_el_setup(void);
 
 void bl1_prepare_next_image(unsigned int image_id);
+void bl1_run_bl2_in_root(void);
 
 u_register_t bl1_fwu_smc_handler(unsigned int smc_fid,
 		u_register_t x1,