[nrf noup] zephyr: Header skip support for secondary MCUboot update

Commit adds NCS_KEEP_MCUBOOT_HEADER_IN_SECONDARY_MCUBOOT Kconfig,
default y, that controls whether MCUboot will keep MCUboot image
header while moving update to s0/s1 slot. This allows to reduce
siez of image in transfer, as smalles possible header can be used
without alignment to VTOR, and allows more space for s0/s1 binary
image.
The option is by default set to y, so users do not have to change
anything in existing configurations.
Note that setting this option to n will create MCUboot image that
can not be used to update secondary MCUboot instances built prior
to the option existence and these with the option set to y.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>

Author: de-nordic

boot/bootutil/src/swap_nsib.c

@@ -37,6 +37,9 @@ void nsib_swap_run(struct boot_loader_state *state, struct boot_status *bs)
     const struct flash_area *fap_pri;
     const struct flash_area *fap_sec;
     int rc;
+#ifndef CONFIG_NCS_KEEP_MCUBOOT_HEADER_IN_SECONDARY_MCUBOOT
+    const struct image_header *hdr = boot_img_hdr(state, BOOT_SLOT_SECONDARY);
+#endif
 
     BOOT_LOG_INF("Starting swap using nsib algorithm.");
 
@@ -53,7 +56,11 @@ void nsib_swap_run(struct boot_loader_state *state, struct boot_status *bs)
     rc = boot_erase_region(fap_pri, 0, fap_pri->fa_size, false);
     assert(rc == 0);
 
+#ifndef CONFIG_NCS_KEEP_MCUBOOT_HEADER_IN_SECONDARY_MCUBOOT
+    rc = boot_copy_region(state, fap_sec, fap_pri, hdr->ih_hdr_size, 0, hdr->ih_img_size);
+#else
     rc = boot_copy_region(state, fap_sec, fap_pri, 0, 0, fap_pri->fa_size);
+#endif
     assert(rc == 0);
 
     rc = swap_scramble_trailer_sectors(state, fap_sec);

boot/zephyr/Kconfig

@@ -1564,6 +1564,20 @@ config NCS_MCUBOOT_MANUFACTURING_APP_KEY_IDENTIFIER
 	help
 	  Manufacturing application key identifier.
 
+
+config NCS_KEEP_MCUBOOT_HEADER_IN_SECONDARY_MCUBOOT
+	bool "Keep MCUboot header in second stage MCUboot bootloader image" if !PARTITION_MANAGER_ENABLED
+	default y
+	depends on MCUBOOT_MCUBOOT_IMAGE_NUMBER != -1
+	help
+	  Default y to keep compatibility with PM built MCUboot images.
+	  When selected, the MCUboot header, attached to MCUboot image for DFU,
+	  will be also copied to s0/s1 slots with MCUboot, even though it is not used
+	  after secondary stage MCUboot updates itself by copying the
+	  update from update slot to target slot.
+	  When unselected the MCUboot header will be stripped, so the entire s0/s1
+	  slot can be used for executable binary part of MCUboot image.
+
 configdefault PSA_CRYPTO
 	  default y if SOC_NRF54H20 && BOOT_SIGNATURE_TYPE_ED25519