Embedded Recipes 2018 - swupdate: update your embedded device - Charles-Antoine Couret

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Swupdate: how to update
your embedded device?
Charles-Antoine Couret September 2018

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Summary
 Introduction
 Main update designs
 Swupdate presentation
 Implementation
 Conclusion
Embedded recipesEmbedded recipes
Swupdate: how to update your embedded devices?Swupdate: how to update your embedded devices?

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Introduction

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Introduction
Why update your embedded devices?
 Fix security issues or bugs
 Add new features
Some constraints to keep in mind
 Cost (bandwidth + development)
 Reliability
 Hardware capabilities (CPU power + memory + storage)
 Local or remote operation
 Security
 Downtime

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Main update designs

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Main update design: packages repository
 Similar to other distributions
Pros:
 Reduced bandwidth usage
 Low required storage
 Simple to deploy (especially with Yocto)
 Short downtime
Cons:
 No atomic operations (until OS-Tree)
 Complex / impossible roll back mechanism
 Unknown state of the device, several combinations of packages are
possible

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Main update design: recovery OS
 Recovery OS to download then install full update
Pros:
 Easy to update another image in case of invalid system
 Low storage (just kernel + initrd with some tools => extra ~10 MiB)
Cons:
 Recovery OS not updated
 Big bandwidth is required : complete firmware is downloaded
 Possible long downtime

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Main update design: dual copy
Pros:
 Everything is updatable (except the bootloader)
 Atomic operation
 Short downtime
Cons:
 Need more bandwidth + storage
 Could require a good process to validate new image

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Other considerations for all designs
Must have:
 Redundant bootloader environment
 Signed or encrypted updates
 Infinite loop proof based on watchdog or consecutive restarts
Not to do:
 Update bootloader (if you don’t have redundant bootloader)

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SWupdate

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Swupdate presentation: general
OpenSource software
Developped by Stefano Babic from DENX company
Repository: https://github.com/sbabic/swupdate
Features:
 Configuration at compile time
 Handle embedded storage: UBI, eMMC, SD, Raw NAND, NOR and SPI-
NOR
 Get updates from local / remote web server, hawkBit connector or local
file
 Support compression, encryption, signature checking, etc.
 Support redundant dual-copy and recovery OS designs
 U-boot integration
 Check software and hardware compatibility

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Swupdate presentation: other features
 Adding new hook or handler (in C or Lua), to update a specific FPGA for example
 Get progression of the process, to display on GUI
 Lua or shell scripting
 Has a rescue GUI in Lua: SWUpdateGUI
 Integration in Yocto and buildroot

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Swupdate presentation: other features
 Integrated web server:
mongoose

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Swupdate presentation: update image
 CPIO image with checksum
 Includes software description file like this:
software =
{
Version = "1.42";
Project_name = {
hardware-compatibility: [ "1" ];
stable = {
copy-1: {
images: (
{
name = "rootfs";
Version = "1.42";
filename = "cmc-imx6ul-image-cmc-imx6ul.ext4.gz";
device = "/dev/mmcblk1p1";
type = "raw";
compressed = true;
}
);

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Implementation

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Implementation: use case
IoT devices
 Based on iMX6UL processor from Variscite provider
 Yocto BSP
 Internal storage: eMMC 8GiB
 Firmware size: ~60 MiB
 Product lifetime: > 10 years
 No SD card or USB slots
 Internet connection from LAN or LTE
Use Cumulocity platform
 MQTT connection
 Firmware / config / software repositories
 Update size (GZ compression): ~19 MiB
 Update notification: 515,SerialNumber,https://aircloud.cumulocity.com/binaries/1568965

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Implementation: design
Update design: dual copy
 Enough storage and bandwidth
 Atomic
 No long downtime (less than 1 minute)
When notification received
 Send ack to Cumulocity after each step
 execlp("swupdate", "swupdate", "-e", "stable,copy-1", "-d", url, NULL);

Download to /tmp (avoid useless eMMC writes)

Check image validity (checksum, hardware, signature)

Install to standby partition

Change U-boot environment
 Reboot
 Validate software (around one hour) + change U-boot variable again

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stable = {
copy-1: {
images: (
{
name = "rootfs";
Version = "1.42";
type = "raw";
compressed = true;
}
);
uboot: (
{
name = "updated";
value = "1";
}
);
};
copy-2: {
images: (
{
name = "rootfs";
Version = "1.42";
type = "raw";
compressed = true;
}
);
uboot: (
{
name = "updated";
value = "1";
}
);
};

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Implementation
 U-boot change
$ fw_setenv updated 0
 Generate image
$ bitbake cmc-imx6ul-swu
or
$ echo -e "sw-descriptionnsw-description.signcmc-imx6ul-image-cmc-imx6ul.ext4.gz" | cpio -ov -H crc >
update.swu
 Yocto recipe (meta-swupdate layer)
SRC_URI = "file://sw-description
file://post_update.sh
"
inherit swupdate
COMPATIBLE = "var-som-mx6"
SWUPDATE_IMAGES = "cmc-imx6ul-image"
SWUPDATE_IMAGES_FSTYPES[cmc-imx6ul-image] = ".ext4.gz"
SWUPDATE_SIGNING = "RSA"
SWUPDATE_PRIVATE_KEY = "/path/to/private/key"

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Conclusion

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Conclusion
 Update your software while the product is alive
 Adapt the update design to your constraints
 Swupdate is a nice and flexible OpenSource project
 It is easy to integrate and develop this feature for your product (some days)

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Do you have questions?
www.mind.be
www.essensium.com
Essensium NV
Mind - Embedded Software Division
Gaston Geenslaan 9, B-3001 Leuven
Tel : +32 16-28 65 00
Fax : +32 16-28 65 01
email : info@essensium.com

Embedded Recipes 2018 - swupdate: update your embedded device - Charles-Antoine Couret

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Embedded Recipes 2018 - swupdate: update your embedded device - Charles-Antoine Couret