ARM64 kernel Image size limitations?

[Ard Biesheuvel]

On 28 August 2017 at 22:24, Florian Fainelli <f.fainelli at gmail.com> wrote:
> (fixed Will's address, apologies)
>
> On 08/28/2017 01:01 PM, Ard Biesheuvel wrote:
>> Hi,
>>
>> On 28 August 2017 at 20:55, Florian Fainelli <f.fainelli at gmail.com> wrote:
>>> Hi,
>>>
>>> I have been fighting with a reasonably large kernel Image: 46MB and
>>> found unable to boot it. This is on v4.13-rc6, but I could go back as
>>> far as v4.9~ish. It is so big, because it's got some debugging enabled,
>>> and the initramfs compression is disabled, but still that ought to be
>>> possible.
>>>
>>> After some experimentation I found that the breaking size is somewhere
>>> around 33MB total for arch/arm64/boot/Image and when that happens, I get
>>> the following backtrace which suggests that there is some memory
>>> corruption of some kind (or so it seems to me), other experiments
>>> indicated that the backtrace may point back to where the bootloader had
>>> set up its exception vector. I am fairly confident that the bootloader
>>> is not responsible for corrupting the Image that is loaded.
>>>
>>> Is there such a size limitation or am I possibly tripping over something
>>> else?
>>>
>>
>> What boot environment are you using? Is it possible the DTB is copied
>> on top of the kernel by the boot loader?
>
> Bootloader is BOLT (Broadcom's own implementation, has PSCI and is
> capable of doing FDT live patching), and yes the DTB is provided by the
> bootloader at an address higher than the kernel.
>
> Physical offset of the RAM on this platform is 0, so the load is going
> to be at PA 0x80000, 0x80000 + size (35MB) = 0x2280000, DTB is placed at
> 0x771f000 and is 0x90ef bytes.
>

Could you try to dump __log_buf from gdb?