commit ad055d19e6401e60a0f290fccec97895c80fb5c0
author Fabio Utzig <utzig@apache.org> Mon Jun 29 20:19:26 2020 -0300
committer Fabio Utzig <utzig@utzig.org> Tue Jul 14 11:11:05 2020 -0300
tree 73b092fb323b68fbc3caa0eef8ff4c53af0e6544
parent a333a4576b553aae32ebb2a8f7eb99cadbf05e57

Allow larger primary slot in swap-move

When using swap in move mode, the current compatibility test only allows
for same size and layout between slots. This results in one sector that
can never be used in the secondary slot, which corresponds to the first
move up operation in the primary slot. This relaxes and checking a bit,
so both same size slots and a primary with one extra sector are valid.

Signed-off-by: Fabio Utzig <utzig@apache.org>

boot/bootutil/src/swap_move.c

diff --git a/boot/bootutil/src/swap_move.c b/boot/bootutil/src/swap_move.c
index b2a0cb7..90bf9d1 100644
--- a/boot/bootutil/src/swap_move.c
+++ b/boot/bootutil/src/swap_move.c
@@ -212,23 +212,36 @@
 int
 boot_slots_compatible(struct boot_loader_state *state)
 {
-    size_t num_sectors;
+    size_t num_sectors_pri;
+    size_t num_sectors_sec;
+    size_t sector_sz_pri = 0;
+    size_t sector_sz_sec = 0;
     size_t i;
 
-    num_sectors = boot_img_num_sectors(state, BOOT_PRIMARY_SLOT);
-    if (num_sectors != boot_img_num_sectors(state, BOOT_SECONDARY_SLOT)) {
-        BOOT_LOG_WRN("Cannot upgrade: slots don't have same amount of sectors");
+    num_sectors_pri = boot_img_num_sectors(state, BOOT_PRIMARY_SLOT);
+    num_sectors_sec = boot_img_num_sectors(state, BOOT_SECONDARY_SLOT);
+    if ((num_sectors_pri != num_sectors_sec) &&
+            (num_sectors_pri != (num_sectors_sec + 1))) {
+        BOOT_LOG_WRN("Cannot upgrade: not a compatible amount of sectors");
         return 0;
     }
 
-    if (num_sectors > BOOT_MAX_IMG_SECTORS) {
+    if (num_sectors_pri > BOOT_MAX_IMG_SECTORS) {
         BOOT_LOG_WRN("Cannot upgrade: more sectors than allowed");
         return 0;
     }
 
-    for (i = 0; i < num_sectors; i++) {
-        if (boot_img_sector_size(state, BOOT_PRIMARY_SLOT, i) !=
-                boot_img_sector_size(state, BOOT_SECONDARY_SLOT, i)) {
+    for (i = 0; i < num_sectors_sec; i++) {
+        sector_sz_pri = boot_img_sector_size(state, BOOT_PRIMARY_SLOT, i);
+        sector_sz_sec = boot_img_sector_size(state, BOOT_SECONDARY_SLOT, i);
+        if (sector_sz_pri != sector_sz_sec) {
+            BOOT_LOG_WRN("Cannot upgrade: not same sector layout");
+            return 0;
+        }
+    }
+
+    if (num_sectors_pri > num_sectors_sec) {
+        if (sector_sz_pri != boot_img_sector_size(state, BOOT_PRIMARY_SLOT, i)) {
             BOOT_LOG_WRN("Cannot upgrade: not same sector layout");
             return 0;
         }