feat(bl2): add support to separate no-loadable sections

Add new options SEPARATE_BL2_NOLOAD_REGION to separate no-loadable
sections (.bss, stack, page tables) to a ram region specified
by BL2_NOLOAD_START and BL2_NOLOAD_LIMIT.

Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>
Change-Id: I844ee0fc405474af0aff978d292c826fbe0a82fd

Makefile

@@ -1021,6 +1021,7 @@ $(eval $(call assert_booleans,\
         RESET_TO_BL31 \
         SAVE_KEYS \
         SEPARATE_CODE_AND_RODATA \
+        SEPARATE_BL2_NOLOAD_REGION \
         SEPARATE_NOBITS_REGION \
         SPIN_ON_BL1_EXIT \
         SPM_MM \
@@ -1136,6 +1137,7 @@ $(eval $(call add_defines,\
         RAS_EXTENSION \
         RESET_TO_BL31 \
         SEPARATE_CODE_AND_RODATA \
+        SEPARATE_BL2_NOLOAD_REGION \
         SEPARATE_NOBITS_REGION \
         RECLAIM_INIT_CODE \
         SPD_${SPD} \

bl2/bl2_el3.ld.S

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017-2020, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2017-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -17,6 +17,11 @@ MEMORY {
     RAM (rwx): ORIGIN = BL2_RW_BASE, LENGTH = BL2_RW_LIMIT - BL2_RW_BASE
 #else
     RAM (rwx): ORIGIN = BL2_BASE, LENGTH = BL2_LIMIT - BL2_BASE
+#if SEPARATE_BL2_NOLOAD_REGION
+    RAM_NOLOAD (rw!a): ORIGIN = BL2_NOLOAD_START, LENGTH = BL2_NOLOAD_LIMIT - BL2_NOLOAD_START
+#else
+#define RAM_NOLOAD RAM
+#endif
 #endif
 }
 
@@ -106,9 +111,18 @@ SECTIONS
     __DATA_RAM_END__ = __DATA_END__;
 
     RELA_SECTION >RAM
-    STACK_SECTION >RAM
-    BSS_SECTION >RAM
-    XLAT_TABLE_SECTION >RAM
+#if SEPARATE_BL2_NOLOAD_REGION
+    SAVED_ADDR = .;
+    . = BL2_NOLOAD_START;
+    __BL2_NOLOAD_START__ = .;
+#endif
+    STACK_SECTION >RAM_NOLOAD
+    BSS_SECTION >RAM_NOLOAD
+    XLAT_TABLE_SECTION >RAM_NOLOAD
+#if SEPARATE_BL2_NOLOAD_REGION
+    __BL2_NOLOAD_END__ = .;
+    . = SAVED_ADDR;
+#endif
 
 #if USE_COHERENT_MEM
     /*

docs/getting_started/build-options.rst

@@ -647,6 +647,13 @@ Common build options
    ``BL31_NOBITS_LIMIT``. When the option is ``0`` (the default), NOBITS
    sections are placed in RAM immediately following the loaded firmware image.
 
+-  ``SEPARATE_BL2_NOLOAD_REGION``: Setting this option to ``1`` allows the
+   NOLOAD sections of BL2 (.bss, stacks, page tables) to be allocated in RAM
+   discontiguous from loaded firmware images. When set, the platform need to
+   provide definitions of ``BL2_NOLOAD_START`` and ``BL2_NOLOAD_LIMIT``. This
+   flag is disabled by default and NOLOAD sections are placed in RAM immediately
+   following the loaded firmware image.
+
 -  ``SMC_PCI_SUPPORT``: This option allows platforms to handle PCI configuration
    access requests via a standard SMCCC defined in `DEN0115`_. When combined with
    UEFI+ACPI this can provide a certain amount of OS forward compatibility
@@ -961,7 +968,7 @@ Firmware update options
 
 --------------
 
-*Copyright (c) 2019-2021, Arm Limited. All rights reserved.*
+*Copyright (c) 2019-2022, Arm Limited. All rights reserved.*
 
 .. _DEN0115: https://developer.arm.com/docs/den0115/latest
 .. _PSA FW update specification: https://developer.arm.com/documentation/den0118/a/

include/arch/aarch32/el3_common_macros.S

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -398,6 +398,12 @@
 		ldr	r1, =__RW_END__
 		sub	r1, r1, r0
 		bl	inv_dcache_range
+#if defined(IMAGE_BL2) && SEPARATE_BL2_NOLOAD_REGION
+		ldr	r0, =__BL2_NOLOAD_START__
+		ldr	r1, =__BL2_NOLOAD_END__
+		sub	r1, r1, r0
+		bl	inv_dcache_range
+#endif
 #endif
 
 		/*

include/arch/aarch64/el3_common_macros.S

@@ -469,6 +469,14 @@
 		sub	x1, x1, x0
 		bl	inv_dcache_range
 #endif
+#if defined(IMAGE_BL2) && SEPARATE_BL2_NOLOAD_REGION
+		adrp	x0, __BL2_NOLOAD_START__
+		add	x0, x0, :lo12:__BL2_NOLOAD_START__
+		adrp	x1, __BL2_NOLOAD_END__
+		add	x1, x1, :lo12:__BL2_NOLOAD_END__
+		sub	x1, x1, x0
+		bl	inv_dcache_range
+#endif
 #endif
 		adrp	x0, __BSS_START__
 		add	x0, x0, :lo12:__BSS_START__

make_helpers/defaults.mk

@@ -250,6 +250,10 @@ SEPARATE_CODE_AND_RODATA	:= 0
 # separate memory region, which may be discontiguous from the rest of BL31.
 SEPARATE_NOBITS_REGION		:= 0
 
+# Put BL2 NOLOAD sections (.bss, stacks, page tables) in a separate memory
+# region, platform Makefile is free to override this value.
+SEPARATE_BL2_NOLOAD_REGION	:= 0
+
 # If the BL31 image initialisation code is recalimed after use for the secondary
 # cores stack
 RECLAIM_INIT_CODE		:= 0