[PATCH] android_ab: fix slot selection

[Colin Pinnell McAllister]

The boot selection rules state that a slot is bootable if it is not
corrupted and either has tries remaining or has already booted
successfully. However, slots that have tries_remaining == 0 and
successful_boot == 1 will be disregarded when picking the slot to
attempt.

Update the selection logic so slots marked successful remain eligible
even when their tries counter is zero. Also include the successful_boot
state in the unbootable-slot debug output.

Signed-off-by: Colin Pinnell McAllister <colin.mcallister at garmin.com>
---

An alternative would be to keep the existing behavior and update the
comment in boot/android_ab.c:276 to remove the successful_boot
condition. I do prefer updating the logic to match the documented rules.
Currently, the userspace AB code will need to increment the tries
counter for a slot that has booted successfully but has no tries left.

 boot/android_ab.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/boot/android_ab.c b/boot/android_ab.c
index 13e82dbcb7f..93e74f81d4b 100644
--- a/boot/android_ab.c
+++ b/boot/android_ab.c
@@ -289,11 +289,14 @@ int ab_select_slot(struct blk_desc *dev_desc, struct disk_partition *part_info,
        slot = -1;
        for (i = 0; i < abc->nb_slot; ++i) {
                if (abc->slot_info[i].verity_corrupted ||
-                   !abc->slot_info[i].tries_remaining) {
+                   (!abc->slot_info[i].tries_remaining &&
+                        !abc->slot_info[i].successful_boot)) {
                        log_debug("ANDROID: unbootable slot %d tries: %d, ",
                                  i, abc->slot_info[i].tries_remaining);
-                       log_debug("corrupt: %d\n",
+                       log_debug("corrupt: %d, ",
                                  abc->slot_info[i].verity_corrupted);
+                       log_debug("successful: %d\n",
+                                 abc->slot_info[i].successful_boot);
                        continue;
                }
                log_debug("ANDROID: bootable slot %d pri: %d, tries: %d, ",
--
2.53.0


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