Added NO_ARM_ASM option

arch.mk

@@ -205,7 +205,8 @@ ifeq ($(CORTEX_A5),1)
 else
   # All others use boot_arm.o
   OBJS+=src/boot_arm.o
-  CORTEXM_ARM_EXTRA_OBJS= \
+  ifneq ($(NO_ARM_ASM),1)
+    CORTEXM_ARM_EXTRA_OBJS= \
           ./lib/wolfssl/wolfcrypt/src/port/arm/armv8-sha256.o \
           ./lib/wolfssl/wolfcrypt/src/port/arm/armv8-sha512.o \
           ./lib/wolfssl/wolfcrypt/src/port/arm/armv8-32-sha256-asm.o \
@@ -216,12 +217,13 @@ else
           ./lib/wolfssl/wolfcrypt/src/port/arm/armv8-32-sha3-asm_c.o
 
 
-  CORTEXM_ARM_THUMB_EXTRA_OBJS= \
+    CORTEXM_ARM_THUMB_EXTRA_OBJS= \
           ./lib/wolfssl/wolfcrypt/src/port/arm/thumb2-sha256-asm.o \
           ./lib/wolfssl/wolfcrypt/src/port/arm/thumb2-sha256-asm_c.o
 
-  CORTEXM_ARM_EXTRA_CFLAGS+=-DWOLFSSL_ARMASM -DWOLFSSL_ARMASM_NO_HW_CRYPTO \
+    CORTEXM_ARM_EXTRA_CFLAGS+=-DWOLFSSL_ARMASM -DWOLFSSL_ARMASM_NO_HW_CRYPTO \
 							-DWOLFSSL_ARMASM_INLINE -DWOLFSSL_ARMASM_NO_NEON
+  endif
   ifeq ($(CORTEX_M33),1)
     CFLAGS+=-mcpu=cortex-m33 -DCORTEX_M33
     LDFLAGS+=-mcpu=cortex-m33

docs/compile.md

@@ -42,6 +42,18 @@ By default, wolfBoot is compiled for ARM Cortex-M3/4/7. To compile for Cortex-M0
 
 `CORTEX_M0=1`
 
+### Speed vs. size
+
+On a number of targets, algorithm may be optimized automatically to use assembly
+optimizations. To disable assembly optimizations, use `NO_ASM=1`. This option will
+produce smaller code, but will also impact on the boot time.
+
+ARM-specific ARM optimizations affecting hash and symmetric key ciphers can be
+disabled with the option `NO_ARM_ASM=1`. This is useful for example when you want
+to use SP math optimizations for key verification, but exclude SHA2/AES optimizations
+to save some space.
+
+
 ### Flash partitions
 
 The file [include/target.h](../include/target.h) is generated according to the configured flash geometry,

tools/config.mk

@@ -23,6 +23,7 @@ ifeq ($(ARCH),)
   CORTEX_M7?=0
   CORTEX_M3?=0
   NO_ASM?=0
+  NO_ARM_ASM?=0
   EXT_FLASH?=0
   SPI_FLASH?=0
   QSPI_FLASH?=0
@@ -104,5 +105,6 @@ CONFIG_VARS:= ARCH TARGET SIGN HASH MCUXSDK MCUXPRESSO MCUXPRESSO_CPU MCUXPRESSO
 	NXP_CUSTOM_DCD NXP_CUSTOM_DCD_OBJS \
 	FLASH_OTP_KEYSTORE \
 	KEYVAULT_OBJ_SIZE \
-	KEYVAULT_MAX_ITEMS
+	KEYVAULT_MAX_ITEMS \
+	NO_ARM_ASM
 

tools/test.mk

@@ -986,37 +986,37 @@ test-all: clean
 
 
 test-size-all:
-	make test-size SIGN=NONE LIMIT=4816
+	make test-size SIGN=NONE LIMIT=4816 NO_ARM_ASM=1
 	make keysclean
-	make test-size SIGN=ED25519 LIMIT=11396
+	make test-size SIGN=ED25519 LIMIT=11396 NO_ARM_ASM=1
 	make keysclean
-	make test-size SIGN=ECC256  LIMIT=17936
+	make test-size SIGN=ECC256  LIMIT=17936 NO_ARM_ASM=1
 	make clean
-	make test-size SIGN=ECC256 NO_ASM=1 LIMIT=13480
+	make test-size SIGN=ECC256 NO_ASM=1 LIMIT=13480 NO_ARM_ASM=1
 	make keysclean
-	make test-size SIGN=RSA2048 LIMIT=11212
+	make test-size SIGN=RSA2048 LIMIT=11212  NO_ARM_ASM=1
 	make clean
-	make test-size SIGN=RSA2048 NO_ASM=1 LIMIT=11788
+	make test-size SIGN=RSA2048 NO_ASM=1 LIMIT=11788 NO_ARM_ASM=1
 	make keysclean
-	make test-size SIGN=RSA4096 LIMIT=11500
+	make test-size SIGN=RSA4096 LIMIT=11500 NO_ARM_ASM=1
 	make clean
-	make test-size SIGN=RSA4096 NO_ASM=1 LIMIT=12076
+	make test-size SIGN=RSA4096 NO_ASM=1 LIMIT=12076 NO_ARM_ASM=1
 	make keysclean
-	make test-size SIGN=ECC384 LIMIT=17504
+	make test-size SIGN=ECC384 LIMIT=17504 NO_ARM_ASM=1
 	make clean
-	make test-size SIGN=ECC384 NO_ASM=1 LIMIT=14872
+	make test-size SIGN=ECC384 NO_ASM=1 LIMIT=14872 NO_ARM_ASM=1
 	make keysclean
-	make test-size SIGN=ED448 LIMIT=13408
+	make test-size SIGN=ED448 LIMIT=13408 NO_ARM_ASM=1
 	make keysclean
-	make test-size SIGN=RSA3072 LIMIT=11352
+	make test-size SIGN=RSA3072 LIMIT=11352 NO_ARM_ASM=1
 	make clean
-	make test-size SIGN=RSA3072 NO_ASM=1 LIMIT=11892
+	make test-size SIGN=RSA3072 NO_ASM=1 LIMIT=11892 NO_ARM_ASM=1
 	make keysclean
 	make test-size SIGN=LMS LMS_LEVELS=2 LMS_HEIGHT=5 LMS_WINTERNITZ=8 \
 		WOLFBOOT_SMALL_STACK=0 IMAGE_SIGNATURE_SIZE=2644 \
-		IMAGE_HEADER_SIZE?=5288 LIMIT=7504
+		IMAGE_HEADER_SIZE?=5288 LIMIT=7504 NO_ARM_ASM=1
 	make keysclean
 	make test-size SIGN=XMSS XMSS_PARAMS='XMSS-SHA2_10_256' \
 		IMAGE_SIGNATURE_SIZE=2500 IMAGE_HEADER_SIZE?=4096 \
-		LIMIT=8220
+		LIMIT=8220 NO_ARM_ASM=1
 	make keysclean