- What I did
Add support of secure warm-boot to SONiC.
Basically, warm-boot is supporting to load a new kernel without doing full/cold boot.
That is by loading a new kernel and exec with kexec Linux command. As a result of that, even when the Secure Boot feature is enabled, still a user or a malicious user can load an unsigned kernel, so to avoid that we added the support of the secure warm boot.
More Description about this feature can be found in the Secure Boot HLD: sonic-net/SONiC#1028

- How I did it
In general, Linux support it, so I enabled this support by doing the follow steps:

I added some special flags in Linux Kernel when user build the sonic-buildimage with secure boot feature enabled.
I added a flag "-s" to the kexec command
Note: more details in the HLD above.

- How to verify it
* Good flow:
manually just install with sonic-installed a new secure image (a SONiC image that was build with Secure Boot flag enabled)
after the secure image is installed, do:
warm-reboot
Check now that the new kernel is really loaded and switched.
* Bad flow:
Do the same steps 1-2 as a good flow but with an insecure image (SONiC image that was built without setting Secure Boot enabled)
After the insecure image is installed, and triggered warm-boot you should get an error that the new unsigned kernel from the unsecured image was not loaded.
Automation test - TBD

…ic-net#2715)

What I did
Warm-reboot fails on kvm due to non-zero exit upon command
bootctl status 2>/dev/null | grep -c "Secure Boot: enabled"

How I did it
Added || true to return 0 when previous command fails.
Added CHECK_SECURE_UPGRADE_ENABLED to check output of previous command
Added debug logs

How to verify it
Run warm-reboot on kvm and physical device when increased verbosity. Expects debug log to indicate secure/non secure boot. Successful warm reboot