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STM32MP157C-DK2 (non-secure?) boot

A quick grep through the latest and greatest release shows this:

$ grep -r STM32MP157C-DK2 . | grep machine
./meta-st/meta-st-stm32mp/conf/machine/stm32mp1-disco.conf:#@DESCRIPTION: [EXAMPLE] STM32MP157C-DK2 board ONLY with Trusted boot and SDcard support
./meta-st/meta-st-stm32mp/conf/machine/stm32mp1-disco.conf:M4_BOARDS = "STM32MP157C-DK2"
./meta-st/meta-st-stm32mp-addons/conf/machine/examples/stm32mp1-disco-mx.conf.sample:#@DESCRIPTION: [STM32CubeMX-EXAMPLE] STM32MP157C-DK2 board ONLY with Trusted boot and SDcard support
./meta-st/meta-st-stm32mp-addons/conf/machine/examples/stm32mp1-disco-mx.conf.sample:CUBEMX_PROJECT = "mx/STM32MP157C-DK2/my-demo/DeviceTree/my-demo"

So I am wondering if/how it's possible to have a kernel/device tree/rootfs which is not signed.

My ideal setup grabs (unsigned) kernel/device tree from tftp and passes to the kernel the kernel command line to boot over nfs (unsigned as well).

If this possible at all here with an unsigned kernel/device tree/rootfs?

If so, can you please elaborate a bit how?

My understanding is, that instead of U-Boot SPL TF-A is used, which loads a signed kernel and device tree (as a matter of fact there seem to be 3 device trees).

Now, I could imagine, that without burning the proper fuses, you could still load unsigned stuff (and the errors are ignored).

Thanks,

Robert

10 REPLIES 10

To answer my own question:

Yes of course you can use non-secure boot since the hardware allows this unless you disable it by hardware fuses.

This is how it can be done software-wise:

machine config:

https://gitlab.com/meta-layers/meta-u-boot-wic-bsp/-/blob/master/conf/machine/stm32mp157c-dk2.conf

wks file:

https://gitlab.com/meta-layers/meta-u-boot-wic-bsp/-/blob/master/wic/stm32mp157c-dk2-sd-card.wks.in

In addition, I use upstream u-boot, kernel, and poky here.