U-Boot: Arm64: bootm gets stuck if RANDOMIZE_BASE is disabled

[Mark Rutland]

On Tue, Jul 13, 2021 at 02:15:08PM +0500, Ahsan Hussain wrote:
> Hello,
> 
> I'm dumbfounded by a seemingly unrelated early kernel hang/failing to boot
> when CONFIG_RANDOMIZE_BASE=n is set in kernel and we use FIT uImage. I've
> verified this behavior on a couple of i.MX8 SoCs (i.MX8M plus and i.MX8QXP)
> and the results remain consistent.
> 
> I'm able to boot kernel when I use booti command. However when I use bootm
> to boot a U-Boot fitImage (with kernel and fdt load addresses/entrypoint in
> .its file same as I used for booti command; also tried disabling relocation
> for fdt by setting fdt_high=~0UL), the boot gets stuck at "Starting kernel
> ...". On disabling RANDOMIZE_BASE kconfig in Linux the same fitImage is able
> to boot.

Can you say which address you're trying to load the kernel to?

> I've tried enabling earlycon and U-Boot debug messages in common/bootm.c and
> arch/arm/lib/bootm.c but found no helpful difference in both boot flows.
> Please let me know if I'm missing something obvious or where do I start
> looking to debug this issue.

IIUC, the booti command respects the text_offset from the kernel header,
whereas bootm will not. If you have a hard-coded offset, it's possible
you're violating the offset the kernel expects, and where the kernel is
not relocatable, if can't fix itself up.

I suspect you have a hard-coded offset of 0x80000, whereas recent
kernels have a text offset of 0x00000. Your bootloader *should* read
this dynamially rather than hard-coding it.

For details, see:

https://www.kernel.org/doc/html/v5.4/arm64/booting.html#call-the-kernel-image

Thanks,
Mark.