feat(imx): add helper to take params from BL2

So far the i.MX BL31 doesn't take any parameters. This means the BL32
image base address and whether or not a BL32 image is used at all has to
be hardcoded in BL31.

This adds a helper function that allows to take params from BL2 safely.
On i.MX BL2 is usually U-Boot SPL which passes random values in arg0,
so make sure arg0 is within the internal SRAM range before accessing it
as a pointer. Also make sure arg0 is sufficiently aligned and the header
type and version is correct.

Change-Id: Idab8013a1d6dabf50a83c75f3e6f831de4a537e9
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

plat/imx/common/imx_common.c

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2024, Pengutronix, Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include <errno.h>
+#include <stdint.h>
+
+#include <common/bl_common.h>
+#include <common/desc_image_load.h>
+
+#include <plat_common.h>
+
+/*
+ * This function checks if @arg0 can safely be accessed as a pointer
+ * and if it does, it fills in @bl32_info and @bl33_info with data
+ * found in @arg0.
+ *
+ * Returns 0 when @arg0 can be used as entry point info and a negative
+ * error code otherwise.
+ */
+int imx_bl31_params_parse(uintptr_t arg0, uintptr_t ocram_base,
+			  uintptr_t ocram_size,
+			  entry_point_info_t *bl32_info,
+			  entry_point_info_t *bl33_info)
+{
+	bl_params_t *v2 = (void *)(uintptr_t)arg0;
+
+	if (arg0 & 0x3) {
+		return -EINVAL;
+	}
+
+	if (arg0 < ocram_base || arg0 >= ocram_base + ocram_size) {
+		return -EINVAL;
+	}
+
+	if (v2->h.version != PARAM_VERSION_2) {
+		return -EINVAL;
+	}
+
+	if (v2->h.type != PARAM_BL_PARAMS) {
+		return -EINVAL;
+	}
+
+	bl31_params_parse_helper(arg0, bl32_info, bl33_info);
+
+	return 0;
+}

plat/imx/common/include/plat_common.h

@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2024, Pengutronix, Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#ifndef PLAT_COMMON_H
+#define PLAT_COMMON_H
+
+#include <stdint.h>
+#include <common/bl_common.h>
+
+int imx_bl31_params_parse(uintptr_t arg0, uintptr_t ocram_base,
+			  uintptr_t ocram_size,
+			  entry_point_info_t *bl32_info,
+			  entry_point_info_t *bl33_info);
+
+#endif /* PLAT_COMMON_H */

plat/imx/imx8m/imx8mm/platform.mk

@@ -46,6 +46,7 @@ BL31_SOURCES		+=	plat/imx/common/imx8_helpers.S			\
 				plat/imx/common/imx8_topology.c			\
 				plat/imx/common/imx_sip_handler.c		\
 				plat/imx/common/imx_sip_svc.c			\
+				plat/imx/common/imx_common.c			\
 				plat/imx/common/imx_uart_console.S		\
 				lib/cpus/aarch64/cortex_a53.S			\
 				drivers/arm/tzc/tzc380.c			\

plat/imx/imx8m/imx8mn/platform.mk

@@ -41,6 +41,7 @@ BL31_SOURCES		+=	plat/imx/common/imx8_helpers.S			\
 				plat/imx/common/imx8_topology.c			\
 				plat/imx/common/imx_sip_handler.c		\
 				plat/imx/common/imx_sip_svc.c			\
+				plat/imx/common/imx_common.c			\
 				plat/imx/common/imx_uart_console.S		\
 				lib/cpus/aarch64/cortex_a53.S			\
 				drivers/arm/tzc/tzc380.c			\

plat/imx/imx8m/imx8mp/platform.mk

@@ -42,6 +42,7 @@ BL31_SOURCES		+=	plat/imx/common/imx8_helpers.S			\
 				plat/imx/common/imx8_topology.c			\
 				plat/imx/common/imx_sip_handler.c		\
 				plat/imx/common/imx_sip_svc.c			\
+				plat/imx/common/imx_common.c			\
 				plat/imx/common/imx_uart_console.S		\
 				lib/cpus/aarch64/cortex_a53.S			\
 				drivers/arm/tzc/tzc380.c			\

plat/imx/imx93/platform.mk

@@ -22,6 +22,7 @@ IMX_GIC_SOURCES		:=	${GICV3_SOURCES}			\
 BL31_SOURCES		+=	plat/common/aarch64/crash_console_helpers.S   \
 				plat/imx/imx93/aarch64/plat_helpers.S		\
 				plat/imx/imx93/plat_topology.c			\
+				plat/imx/common/imx_common.c			\
 				plat/imx/common/lpuart_console.S		\
 				plat/imx/imx93/trdc.c			\
 				plat/imx/imx93/pwr_ctrl.c			\