ARM64 kernel Image size limitations?

[Florian Fainelli]

(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.


-- 
Florian