# Re: \[PATCH v9 0/6\] add support for relative references in special sections

- From: Michael Ellerman \<mpe@ellerman.id.au\>
- Date: 2018-06-27 05:34:01 
- List: linuxppc-dev
- Page: https://ratatoskr.run/linuxppc-dev/2018/06/5318024
- Thread: https://ratatoskr.run/linux-arm-kernel/2018/06/5317749/t.md

```text
Ard Biesheuvel [ref] writes:
> This adds support for emitting special sections such as initcall arrays,
> PCI fixups and tracepoints as relative references rather than absolute
> references. This reduces the size by 50% on 64-bit architectures, but
> more importantly, it removes the need for carrying relocation metadata
> for these sections in relocatable kernels (e.g., for KASLR) that needs
> to be fixed up at boot time. On arm64, this reduces the vmlinux footprint
> of such a reference by 8x (8 byte absolute reference + 24 byte RELA entry
> vs 4 byte relative reference)
...
>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Kees Cook <redacted>
> Cc: Will Deacon <redacted>
> Cc: Michael Ellerman <mpe@ellerman.id.au>

This seems to be working on powerpc.

It boots on a couple of machines with no obvious badness.

And there's some size reduction with a random config I had lying around:

  Total: Before=14820494, After=14673313, chg -0.99%


It can get some more testing once it's in linux-next as far as I'm
concerned.

  Acked-by: Michael Ellerman [ref] (powerpc)

cheers
```