[PATCH 2/2] ARM: axxia: remove TEXT_OFFSET override hack

[Alexander Sverdlin]

Hi Ard!

On 12/01/2021 15:05, Ard Biesheuvel wrote:
>>>>> --- a/arch/arm/Makefile
>>>>> +++ b/arch/arm/Makefile
>>>>> @@ -151,7 +151,6 @@ textofs-$(CONFIG_ARCH_IPQ40XX) := 0x00208000
>>>>>  textofs-$(CONFIG_ARCH_MSM8X60) := 0x00208000
>>>>>  textofs-$(CONFIG_ARCH_MSM8960) := 0x00208000
>>>>>  textofs-$(CONFIG_ARCH_MESON) := 0x00208000
>>>>> -textofs-$(CONFIG_ARCH_AXXIA) := 0x00308000
>>>>>
>>>>>  # Machine directory name.  This list is sorted alphanumerically
>>>>>  # by CONFIG_* macro name.
>>>> What should the users of uncompressed kernel do with their legacy bootloaders?
>>>> I've tested you patch and AXXIA bootloader is not able to deal with 0x8000 default
>>>> load address...
>>>>
>>> I am not sure I understand why this makes a difference. Does the AXXIA
>>> bootloader take the load address from the uncompressed image somehow?
>>>
>>> I would assume that the bootloader knows about the memory reservation
>>> at the base of DRAM, and places the kernel image outside of it. That
>>> kernel image can now run at any offset of the start of DRAM modulo 2
>>> MB.
>>>
>>> Maybe the issue is that the old offset is 3 MiB?
>>
>> Some more info from the AXXIA U-Boot, include/configs/axxia.arm.h:
>>
>> #define CONFIG_UBOOT_REGION_SIZE        0x400000
>> #define CONFIG_FEMAC_DMA_SIZE           0x40000
>> #define CONFIG_FEMAC_DMA_START          (CONFIG_UBOOT_REGION_SIZE - CONFIG_FEMAC_DMA_SIZE)
>>
>> From what I see in same file the layout seems to be:
>> Start: 0
>> CodeEnd: 0x200000
>> StackTop: 0x260000
>> HeapTop: 0x3C0000
>> FEMAC_Top: 0x400000
>>
>> So the previous 0x308000 worked overwriting U-Boot heap, but
>> going down to 0x8000 actually overwrites U-Boot code and everything explodes...
>>
> 
> It is rather disappointing that the axxia bootloader is so braindead
> that it will overwrite itself if vmlinux is not built with a huge hole
> at the beginning.
> 
> I guess that rules out any cleanup we might attempt to do here.

I can try passing TEXT_OFFSET to the make, but is this official interface
to the Linux Makefile which will be persistent?

-- 
Best regards,
Alexander Sverdlin.