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

[Michael Ellerman]

Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> 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@xxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>

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 <mpe@xxxxxxxxxxxxxx> (powerpc)

cheers