[PATCH 1/5] arm64: PIE: Skip fixups if distance is zero

[André Przywara]

On 24/09/2020 21:22, Stephen Warren wrote:

Hi Stephen,

> On 9/24/20 8:45 AM, André Przywara wrote:
>> On 24/09/2020 01:17, Andre Przywara wrote:
>>> When the actual offset between link and runtime address is zero, there
>>> is no need for patching up U-Boot early when running with
>>> CONFIG_POSITION_INDEPENDENT.
>>
>> That turns out to be not fully true.
>> Some toolchains (all Linaro cross compilers?) don't handle this well,
>> they keep the original locations in the binary uninitialised, and rely
>> on the reldyn fixup table to patch in the actual values.
>> Other compilers (GCC 9.2 vanilla, Ubuntu GCC 7.5.0, Arm website 9.2)
>> fill in the addresses both into the binary and the fixup, so this patch
>> works.
>>
>> It seems to be fixed by enabling CONFIG_STATIC_RELA?
>> I see it's disabled for CONFIG_POSITION_INDEPENDENT, what was the reason
>> behind that?
> 
> I can't remember for sure. I tried re-enabling STATIC_RELA at both the
> upstream commit where POSITION_INDEPENDENT was first implemented and at
> top-of-tree, and ran test/py on Tegra, and it works fine. Perhaps I just
> figured there was no need to perform the static relocations since the
> code would always do it? I figure it's safe to re-enable it, i.e.
> decouple the two config options completely.

Many thanks for the reply and the test!
And yeah, I was hoping that it was just for "because we don't need to".

I will send a patch to always use STATIC_RELA for arm64. As Ard pointed
out, it should actually not be needed anymore (for newer binutils), but
the Linaro toolchains miss this change, and quite some people use them.

Cheers,
Andre