Add swap using offset mode #2162

nordicjm · 2025-01-02T12:29:08Z

165KiB update using swap using move on nrf5340dk: 18 seconds
182KiB update using swap using offset on nrf5340dk: 13 seconds

Laczen · 2025-01-04T07:06:02Z

@nordicjm this is a very nice improvement. There are some minor documentation nits.

A further possible improvement could be to place the swap state (image trailer) in the update image slot (this will not be erased during the swap, and thus the image could go up to the slot size - trailer size).

nordicjm · 2025-01-06T12:29:41Z

@nordicjm this is a very nice improvement. There are some minor documentation nits.

A further possible improvement could be to place the swap state (image trailer) in the update image slot (this will not be erased during the swap, and thus the image could go up to the slot size - trailer size).

I left it in the first as with the "move" slot being moved to the second image, the overhead in both slots is now about equal (swap status in primary, move slot in secondary). However I'm not sure if this mode will actually be finished, the simulator is a giant fight and lots of edge cases need handling in application code to account for the secondary slot image being at either offset, and as of right now the simulator failures make no sense to me

Laczen · 2025-01-11T09:31:28Z

Some food for further thoughts: I have created a similar approach outside of mcuboot, by using a different terminology:
A "backup slot" is defined that starts one sector before the "update slot" and has the same size of the "update slot" and the "image slot", so the backup slot covers a part of the "update slot" (ends one sector sooner).

The image update moves one sector from image to backup followed by a move from update to image, when the update is finished the old image is in the backup slot and the new image is in the image slot. A restore is a move from the backup slot to the image slot.

The method also allows removing the "swap with scratch" as the "scratch" sector can be defined as the first sector of the backup image.

For devices that have plenty of flash the backup slot can also be defined separate from the update slot to enhance the life and keep flash wear equal for all slots (update erases all flash only once).

nordicjm · 2025-01-13T08:06:57Z

The method also allows removing the "swap with scratch" as the "scratch" sector can be defined as the first sector of the backup image.

The plan is that swap using scratch will be removed in the coming future, but as it stands right now this would not work, e.g. on an stm32 where the sector sizes are 32KiB, 32KiB, 64KiB, 128KiB, 128KiB - making it the first sector give a scratch size of 32KiB which means you can't complete a single swap. The idea is that MCUboot's "sector size" will not be the flash sector size in future, it will be able to be configured so in the case of the stm32 will be 128KiB, in the case of a device with internal and external flash whereby internal flash has 2KiB sectors and external flash has 8KiB sectors, both will be 8KiB - once this change is made it means that swap using scratch can be removed entirely because despite the device have different sector sizes, the move is done in multiples of the largest sector size. The added benefit of this is that the code is smaller and swap status area is smaller too

butok · 2025-01-14T07:29:17Z

Hi @nordicjm
SWAP_USING_OFFSET is better than SWAP_USING_MOVE.
Are there any cases where SWAP_USING_MOVE is preferable over OFFSET?

nordicjm · 2025-01-14T07:31:37Z

Hi @nordicjm SWAP_USING_OFFSET is better than SWAP_USING_MOVE. Are there any cases where SWAP_USING_MOVE is preferable over OFFSET?

When building for existing products where the bootloader is configured in swap using move mode, other than that swap using offset should become the new default

Refactors some functions so that the state variable is present in it Signed-off-by: Jamie McCrae <[email protected]>

Adds a new variation of the swap using move mode, named swap using offset, whereby instead of moving all the sectors in the primary image, the sectors in the secondary image are offset instead. This fastens image swapping time both for updates and reverts as each sector in both slots is erased only once, which also reduces flash wear, and uses less swap status bits to represent Signed-off-by: Jamie McCrae <[email protected]>

Adds support for using this mode to zephyr Signed-off-by: Jamie McCrae <[email protected]>

Adds support for getting the sector size of less sectors than are in an image, which mirrors support in zephyr and allows getting just the size of the first sector in an image Signed-off-by: Jamie McCrae <[email protected]>

Enables testing this new mode Signed-off-by: Jamie McCrae <[email protected]>

Fixes not using a pointer as a pointer Signed-off-by: Jamie McCrae <[email protected]>

Adds details on how this new mode works Signed-off-by: Jamie McCrae <[email protected]>

Adds a note about this new algorithm being added Signed-off-by: Jamie McCrae <[email protected]>

Fixes some comments which had typos or were not formatted correctly Signed-off-by: Jamie McCrae <[email protected]>

Adds support for serial recovery of images when MCUboot is set to swap using offset mode Signed-off-by: Jamie McCrae <[email protected]>

d3zd3z

Looks good. I think this will make a good default.

de-nordic · 2025-01-24T10:53:34Z

boot/boot_serial/include/boot_serial/boot_serial_encryption.h

+#ifdef MCUBOOT_SWAP_USING_OFFSET
+                              , uint32_t start_off
+#endif


For the future: We should just rewrite the code to take this param anyway and ignore it when not used.

de-nordic · 2025-01-24T10:54:09Z

boot/boot_serial/src/boot_serial_encryption.c

+#ifdef MCUBOOT_SWAP_USING_OFFSET
+                              , uint32_t start_off
+#endif


de-nordic · 2025-01-24T10:54:47Z

boot/bootutil/include/bootutil/enc_key.h

+#if defined(MCUBOOT_SWAP_USING_OFFSET) && defined(MCUBOOT_SERIAL_RECOVERY)
+                  , uint32_t start_off
+#endif


de-nordic · 2025-01-24T14:10:03Z

boot/bootutil/src/swap_offset.c

+            off = boot_img_sector_size(state, BOOT_SECONDARY_SLOT, 0);
+        }
+
+        rc = flash_area_read(fap, off, out_hdr, sizeof *out_hdr);


I think that convention in MCUboot is to use () after sizeof.

nvlsianpu

New swap alg. is introduced as it should be - new swap code is placed in dedicate source, changes are made in logical chunks and legible.
This implements what I had in my minds a few years ago.

nvlsianpu · 2025-01-24T15:39:00Z

docs/design.md

+a smaller swap status area size.
+
+When using this algorithm the maximum image size available for the application
+will be the smallest of the following:


just: will be:?

nvlsianpu · 2025-01-24T15:47:36Z

docs/release-notes.d/swap-using-offset.md

+  up by having the update image written in the second sector in
+  the update slot, which offers a faster update process and
+  requires a smaller swap status area
+- Made swap using offset the default algorithm for Zephyr builds


This is set as default if preferred... as it was with the move alg before

nordicjm requested a review from de-nordic January 2, 2025 12:29

nordicjm force-pushed the swaplesserase branch 5 times, most recently from 1f86386 to 484d0f5 Compare January 3, 2025 12:53

nordicjm force-pushed the swaplesserase branch from 484d0f5 to b6b32c5 Compare January 6, 2025 11:13

nordicjm force-pushed the swaplesserase branch 5 times, most recently from f61a84d to 546b5b5 Compare January 10, 2025 13:38

nordicjm force-pushed the swaplesserase branch from 546b5b5 to 678cb93 Compare January 13, 2025 08:01

nordicjm marked this pull request as ready for review January 13, 2025 08:11

nordicjm requested review from davidvincze and d3zd3z as code owners January 13, 2025 08:11

nordicjm force-pushed the swaplesserase branch 3 times, most recently from 769bca3 to 9e28dea Compare January 13, 2025 10:18

zephyrbot mentioned this pull request Jan 13, 2025

mcuboot: Add support for swap using offset algorithm zephyrproject-rtos/zephyr#83893

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nordicjm force-pushed the swaplesserase branch 2 times, most recently from d12d10d to 8cf39b8 Compare January 15, 2025 08:16

boot: bootutil: Refactor some functions to have state

86bd792

Refactors some functions so that the state variable is present in it Signed-off-by: Jamie McCrae <[email protected]>

nordicjm force-pushed the swaplesserase branch from 8cf39b8 to 9fa2367 Compare January 15, 2025 10:25

nordicjm added 9 commits January 15, 2025 12:22

zephyr: Add support for swap using offset mode

089ae2d

Adds support for using this mode to zephyr Signed-off-by: Jamie McCrae <[email protected]>

sim: Add swap using offset to tests

6b6a527

Enables testing this new mode Signed-off-by: Jamie McCrae <[email protected]>

sim: Fix wrong usage of pointer

2305757

Fixes not using a pointer as a pointer Signed-off-by: Jamie McCrae <[email protected]>

docs: design: Add information on swap using offset mode

8d26acf

Adds details on how this new mode works Signed-off-by: Jamie McCrae <[email protected]>

docs: release-notes: Add note on new swap using offset mode

14c9b8c

Adds a note about this new algorithm being added Signed-off-by: Jamie McCrae <[email protected]>

boot: bootutil: loader: Fix some comments

62b6b08

Fixes some comments which had typos or were not formatted correctly Signed-off-by: Jamie McCrae <[email protected]>

boot: boot_serial: Add support for swap using offset mode

e09365f

Adds support for serial recovery of images when MCUboot is set to swap using offset mode Signed-off-by: Jamie McCrae <[email protected]>

nordicjm force-pushed the swaplesserase branch from 9fa2367 to e09365f Compare January 15, 2025 13:33

d3zd3z approved these changes Jan 23, 2025

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de-nordic requested a review from nvlsianpu January 24, 2025 14:16

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Add swap using offset mode #2162

Add swap using offset mode #2162

nordicjm commented Jan 2, 2025 •

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Add swap using offset mode #2162

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Add swap using offset mode #2162

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