boot: Simplify copy loop in boot_copy_region

Move checking of conditions, which remain the same for the whole
loop run, outside of the loop.

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

boot/bootutil/src/loader.c

@@ -1215,23 +1215,52 @@ boot_copy_region(struct boot_loader_state *state,
  int chunk_sz;
  int rc;
 #ifdef MCUBOOT_ENC_IMAGES
- uint32_t off;
+ uint32_t off = off_dst;
  uint32_t tlv_off;
  size_t blk_off;
  struct image_header *hdr;
  uint16_t idx;
  uint32_t blk_sz;
- uint8_t image_index;
+ uint8_t image_index = BOOT_CURR_IMG(state);
  bool encrypted_src;
  bool encrypted_dst;
- /* Assuming the secondary slot is source and needs decryption */
+ /* Assuming the secondary slot is source; note that 0 here not only
+ * means that primary slot is source, but also that there will be
+ * encryption happening, if it is 1 then there is decryption from
+ * secondary slot.
+ */
  int source_slot = 1;
+ /* In case of encryption enabled, we may have to do more work than
+ * just copy bytes */
+ bool only_copy = false;
+#else
+ (void)state;
 #endif
 
  TARGET_STATIC uint8_t buf[BUF_SZ] __attribute__((aligned(4)));
 
-#if !defined(MCUBOOT_ENC_IMAGES)
- (void)state;
+#ifdef MCUBOOT_ENC_IMAGES
+ encrypted_src = (flash_area_get_id(fap_src) != FLASH_AREA_IMAGE_PRIMARY(image_index));
+ encrypted_dst = (flash_area_get_id(fap_dst) != FLASH_AREA_IMAGE_PRIMARY(image_index));
+
+ if (encrypted_src != encrypted_dst) {
+ off = off_dst;
+
+ if (encrypted_dst) {
+ /* Need encryption, metadata from the primary slot */
+ hdr = boot_img_hdr(state, BOOT_PRIMARY_SLOT);
+ source_slot = 0;
+ } else {
+ /* Need decryption, metadata from the secondary slot */
+ hdr = boot_img_hdr(state, BOOT_SECONDARY_SLOT);
+ source_slot = 1;
+ }
+ } else {
+ /* In case when source and targe tis the same area, this means that we
+ * only have to copy bytes, no encryption or decryption.
+ */
+ only_copy = true;
+ }
 #endif
 
  bytes_copied = 0;
@@ -1248,57 +1277,41 @@ boot_copy_region(struct boot_loader_state *state,
  }
 
 #ifdef MCUBOOT_ENC_IMAGES
- image_index = BOOT_CURR_IMG(state);
- encrypted_src = (flash_area_get_id(fap_src) != FLASH_AREA_IMAGE_PRIMARY(image_index));
- encrypted_dst = (flash_area_get_id(fap_dst) != FLASH_AREA_IMAGE_PRIMARY(image_index));
-
- if (encrypted_src != encrypted_dst) {
- off = off_dst;
-
- if (encrypted_dst) {
- /* Need encryption, metadata from the primary slot */
- hdr = boot_img_hdr(state, BOOT_PRIMARY_SLOT);
- source_slot = 0;
+ /* If only copy, then does not matter if header indicates need for
+ * encryptio/decryptio, we just copy data. */
+ if (!only_copy && IS_ENCRYPTED(hdr)) {
+ uint32_t abs_off = off + bytes_copied;
+ if (abs_off < hdr->ih_hdr_size) {
+ /* do not decrypt header */
+ if (abs_off + chunk_sz > hdr->ih_hdr_size) {
+ /* The lower part of the chunk contains header data */
+ blk_off = 0;
+ blk_sz = chunk_sz - (hdr->ih_hdr_size - abs_off);
+ idx = hdr->ih_hdr_size - abs_off;
+ } else {
+ /* The chunk contains exclusively header data */
+ blk_sz = 0; /* nothing to decrypt */
+ }
  } else {
- /* Need decryption, metadata from the secondary slot */
- hdr = boot_img_hdr(state, BOOT_SECONDARY_SLOT);
- source_slot = 1;
+ idx = 0;
+ blk_sz = chunk_sz;
+ blk_off = (abs_off - hdr->ih_hdr_size) & 0xf;
  }
 
- if (IS_ENCRYPTED(hdr)) {
- uint32_t abs_off = off + bytes_copied;
- if (abs_off < hdr->ih_hdr_size) {
- /* do not decrypt header */
- if (abs_off + chunk_sz > hdr->ih_hdr_size) {
- /* The lower part of the chunk contains header data */
- blk_off = 0;
- blk_sz = chunk_sz - (hdr->ih_hdr_size - abs_off);
- idx = hdr->ih_hdr_size - abs_off;
+ if (blk_sz > 0)
+ {
+ tlv_off = BOOT_TLV_OFF(hdr);
+ if (abs_off + chunk_sz > tlv_off) {
+ /* do not decrypt TLVs */
+ if (abs_off >= tlv_off) {
+ blk_sz = 0;
  } else {
- /* The chunk contains exclusively header data */
- blk_sz = 0; /* nothing to decrypt */
- }
- } else {
- idx = 0;
- blk_sz = chunk_sz;
- blk_off = (abs_off - hdr->ih_hdr_size) & 0xf;
- }
-
- if (blk_sz > 0)
- {
- tlv_off = BOOT_TLV_OFF(hdr);
- if (abs_off + chunk_sz > tlv_off) {
- /* do not decrypt TLVs */
- if (abs_off >= tlv_off) {
- blk_sz = 0;
- } else {
- blk_sz = tlv_off - abs_off;
- }
+ blk_sz = tlv_off - abs_off;
  }
- boot_encrypt(BOOT_CURR_ENC(state), source_slot,
- (abs_off + idx) - hdr->ih_hdr_size, blk_sz,
- blk_off, &buf[idx]);
  }
+ boot_encrypt(BOOT_CURR_ENC(state), source_slot,
+ (abs_off + idx) - hdr->ih_hdr_size, blk_sz,
+ blk_off, &buf[idx]);
  }
  }
 #endif