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

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.

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