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

[Ahsan Hussain]

On 7/13/21 2:25 PM, Mark Rutland wrote:
> 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?
At 0xf0000000, towards the end of first DRAM bank which starts at 
0x40000000.
>> 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.

A minor correction is that when CONFIG_RANDOMIZE_BASE is _enabled_ the 
issue is gone. It is only observed when RANDOMIZE_BASE is _disabled_. 
Both booti and bootm calculate text_offset the same way based on arm64 
image header->image_size field, in booti_setup() routine from U-Boot 
arch/arm/lib/image.c.


Regards,
Ahsan