i.MX ProcessorsのトピックRe: imx8mm not starting kernel when enabling verified boot

imx8mm not starting kernel when enabling verified boot

LarsIndresaeter — Mon, 23 Nov 2020 15:53:43 GMT

Hi,

I am trying to get verified boot to work on a custom board based on the i.MX 8M Mini EVK.

I have modified the code in the branch branch

imx_v2020.04_5.4.47_2.2.0

from the repo

https://source.codeaurora.org/external/imx/uboot-imx

to match my board and I am able to boot Linux.

Then I follow the receipe in

doc/uImage.FIT/signature.txt

and add a public key to my dts file and the following to my defconfig

CONFIG_FIT_SIGNATURE=y
CONFIG_SPL_RSA=y

What I observe is that the signature is successfully verified but the Kernel is not started.

The last print out from u-boot is:

==========================================================

## Loading fdt from FIT Image at 40480000 ...
Using 'conf-1' configuration
Verifying Hash Integrity ... OK
Trying 'fdt-0' fdt subimage
Description: Flattened Device Tree blob
Type: Flat Device Tree
Compression: uncompressed
Data Start: 0x413b3b6c
Data Size: 37477 Bytes = 36.6 KiB
Architecture: AArch64
Hash algo: sha1
Hash value: d17e6dae443d3b59eb5ae62e41ad65c2cd54e75b
Sign algo: sha1,rsa2048:dev
Sign value: 4d28bdd3ce1df8e9d93e37b1f9ec6f60e89d1e278f94ca72958b1d7f35ab5abb9586900cf7a9e31440765af3339434713514116c1435
Verifying Hash Integrity ... sha1,rsa2048:dev+ sha1+ OK
Booting using the fdt blob at 0x413b3b6c
Loading Kernel Image
Using Device Tree in place at 00000000413b3b6c, end 00000000413bfdd0

Starting kernel ...

unable to select a mode
device_remove: Device 'mmc@30b60000.blk' failed to remove, but children are gone

==========================================================

The signature check was successful and u-boot should now boot the same Linux kernel that we know to work.

The last thing u-boot is doing is to call armv8_switch_to_el2() in the file arch/arm/lib/bootm.c.

Note that the mmc error message is also present when I am able to boot Linux without verified boot.

Is there anyone out there that recognize this behavior and can provide me with some clues? Perhaps some missing configs?

Lars

Re: imx8mm not starting kernel when enabling verified boot

Zhiming_Liu — Thu, 26 Nov 2020 02:38:20 GMT

You can refer ro this filehttps://www.nxp.com/docs/en/application-note/AN4581.pdf and other community about HABV4.

Best Regards

Zhiming

Re: imx8mm not starting kernel when enabling verified boot

LarsIndresaeter — Thu, 26 Nov 2020 14:41:27 GMT

Thank you for your response.

What I am attempting to do is to extend the root of trust from u-boot using verified boot. U-boot will eventually be signed by HABv4.

The kernel and ramdisk is signed using a separate process and the public key from this process is embedded in u-boot.bin.

I have tried this with the branch imx_v2018.03_4.14.98_2.1.0 (and corresponding versions for the kernel and atf). With this version I can get HABv4 to work and I can get verified boot to work but not both at the same time.

Since it is a good idea to use a more recent version of u-boot I decided to use u-boot branch imx_v2020.04_5.4.47_2.2.0 but now I am not able to get verified boot to work.

All this makes me wonder if HABv4 and verified boot works together and if it is tested by NXP.