Fix double swap on interrupted revert
This fixes #480.
When mcuboot rewrites image trailers during a swap, some information is
lost. If a reset occurs before the swap completes, mcuboot may not be
able to determine what which swap type to resume upon startup.
Specifically, if a "revert" swap gets interupted, mcuboot will perform
an extraneous swap on the subsequent boot. See
https://github.com/JuulLabs-OSS/mcuboot/issues/480 for details.
This commit adds an additional field to the image trailer: `swap-type`.
The new trailer structure is illustrated below:
```
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
~ Swap status (BOOT_MAX_IMG_SECTORS * min-write-size * 3) ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Encryption key 0 (16 octets) [*] ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Encryption key 1 (16 octets) [*] ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Swap size | 0xff padding (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Swap type | 0xff padding (7 octets) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Copy done | 0xff padding (7 octets) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Image OK | 0xff padding (7 octets) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ MAGIC (16 octets) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
```
The `swap-type` field contains one of the `BOOT_SWAP_TYPE_[...]` constants.
Every time a trailer is written, this field is written along with it.
When resuming an interrupted swap, mcuboot uses this field alone to
determine the type of swap being resumed. For new swap operations
(non-resume case), this field is not read at all; instead, mcuboot
consults the `boot_swap_tables` array to determine the swap operation to
perform (as it did prior to this commit).
Some additional changes were necessary to make all the simulated unit
tests pass:
* Before initiating a new swap operation, always write the image trailer
to the scratch area. This step allows mcuboot to persist the
`swap-type` field somewhere before erasing the trailer in the primary
slot. If a reset occurs immediately after the erase, mcuboot recovers
by using the trailer in the scratch area.
* Related to the above: if the scratch area is being used to hold status
bytes (because there are no spare sectors in the primary slot), erase
the scratch area immediately after the trailer gets written to the
primary slot. This eliminates ambiguity regarding the location of the
current trailer in case a reset occurs shortly afterwards.
Signed-off-by: Christopher Collins <ccollins@apache.org>
diff --git a/boot/bootutil/src/bootutil_priv.h b/boot/bootutil/src/bootutil_priv.h
index a5ca42f..d2871ee 100644
--- a/boot/bootutil/src/bootutil_priv.h
+++ b/boot/bootutil/src/bootutil_priv.h
@@ -61,6 +61,7 @@
uint32_t idx; /* Which area we're operating on */
uint8_t state; /* Which part of the swapping process are we at */
uint8_t use_scratch; /* Are status bytes ever written to scratch? */
+ uint8_t swap_type; /* The type of swap in effect */
uint32_t swap_size; /* Total size of swapped image */
#ifdef MCUBOOT_ENC_IMAGES
uint8_t enckey[2][BOOT_ENC_KEY_SIZE];
@@ -71,6 +72,7 @@
#define BOOT_MAGIC_BAD 2
#define BOOT_MAGIC_UNSET 3
#define BOOT_MAGIC_ANY 4 /* NOTE: control only, not dependent on sector */
+#define BOOT_MAGIC_NOTGOOD 5 /* NOTE: control only, not dependent on sector */
/*
* NOTE: leave BOOT_FLAG_SET equal to one, this is written to flash!
@@ -89,31 +91,42 @@
/**
* End-of-image slot structure.
*
- * 0 1 2 3
- * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
- * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- * ~ ~
- * ~ Swap status (variable, aligned) ~
- * ~ ~
- * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- * | Swap size |
- * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- * ~ padding with erased val (MAX ALIGN - 4) ~
- * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- * | Copy done | padding with erased val (MAX ALIGN - 1) ~
- * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- * | Image OK | padding with erased val (MAX ALIGN - 1) ~
- * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- * ~ MAGIC (16 octets) ~
- * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * 0 1 2 3
+ * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * ~ ~
+ * ~ Swap status (BOOT_MAX_IMG_SECTORS * min-write-size * 3) ~
+ * ~ ~
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Encryption key 0 (16 octets) [*] |
+ * | |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Encryption key 1 (16 octets) [*] |
+ * | |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Swap size (4 octets) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Swap type | 0xff padding (7 octets) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Copy done | 0xff padding (7 octets) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | Image OK | 0xff padding (7 octets) |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | MAGIC (16 octets) |
+ * | |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ *
+ * [*]: Only present if the encryption option is enabled
+ * (`MCUBOOT_ENC_IMAGES`).
*/
extern const uint32_t boot_img_magic[4];
struct boot_swap_state {
- uint8_t magic; /* One of the BOOT_MAGIC_[...] values. */
- uint8_t copy_done;
- uint8_t image_ok;
+ uint8_t magic; /* One of the BOOT_MAGIC_[...] values. */
+ uint8_t swap_type; /* One of the BOOT_SWAP_TYPE_[...] values. */
+ uint8_t copy_done; /* One of the BOOT_FLAG_[...] values. */
+ uint8_t image_ok; /* One of the BOOT_FLAG_[...] values. */
};
#define BOOT_MAX_IMG_SECTORS MCUBOOT_MAX_IMG_SECTORS
@@ -143,9 +156,6 @@
#define BOOT_STATUS_SOURCE_SCRATCH 1
#define BOOT_STATUS_SOURCE_PRIMARY_SLOT 2
-#define BOOT_FLAG_IMAGE_OK 0
-#define BOOT_FLAG_COPY_DONE 1
-
extern const uint32_t BOOT_MAGIC_SZ;
/**
@@ -180,9 +190,11 @@
int bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig,
size_t slen, uint8_t key_id);
+int boot_magic_compatible_check(uint8_t tbl_val, uint8_t val);
uint32_t boot_trailer_sz(uint8_t min_write_sz);
int boot_status_entries(const struct flash_area *fap);
uint32_t boot_status_off(const struct flash_area *fap);
+uint32_t boot_swap_type_off(const struct flash_area *fap);
int boot_read_swap_state(const struct flash_area *fap,
struct boot_swap_state *state);
int boot_read_swap_state_by_id(int flash_area_id,
@@ -192,6 +204,7 @@
int boot_schedule_test_swap(void);
int boot_write_copy_done(const struct flash_area *fap);
int boot_write_image_ok(const struct flash_area *fap);
+int boot_write_swap_type(const struct flash_area *fap, uint8_t swap_type);
int boot_write_swap_size(const struct flash_area *fap, uint32_t swap_size);
int boot_read_swap_size(uint32_t *swap_size);
#ifdef MCUBOOT_ENC_IMAGES