ARM64 kernel Image size limitations?

[Florian Fainelli]

On 08/29/2017 09:51 AM, Florian Fainelli wrote:
> On 08/29/2017 01:15 AM, Ard Biesheuvel wrote:
>> 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?
> 
> Silly me, this is a bootloader limitation, unlike what I thought the
> load address is not at PA 0, it is at PA 0x06FFC000 and there is only
> ~34MB worth of space available, mayhem ensues.

Most definitively -ENOCOFFEE it is loaded at PA 0x80000 as I expect it
to, I will try to get you a log after drinking some coffee ;)
-- 
Florian