Re: [PATCH v9 0/6] add support for relative references in special sections
From: Ingo Molnar
Date: Tue Jul 03 2018 - 04:39:04 EST
* Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> wrote:
> On 27 June 2018 at 17:15, Will Deacon <will.deacon@xxxxxxx> wrote:
> > Hi Ard,
> > On Tue, Jun 26, 2018 at 08:27:55PM +0200, Ard Biesheuvel wrote:
> >> 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)
> >> Patch #3 was sent out before as a single patch. This series supersedes
> >> the previous submission. This version makes relative ksymtab entries
> >> dependent on the new Kconfig symbol HAVE_ARCH_PREL32_RELOCATIONS rather
> >> than trying to infer from kbuild test robot replies for which architectures
> >> it should be blacklisted.
> >> Patch #1 introduces the new Kconfig symbol HAVE_ARCH_PREL32_RELOCATIONS,
> >> and sets it for the main architectures that are expected to benefit the
> >> most from this feature, i.e., 64-bit architectures or ones that use
> >> runtime relocations.
> >> Patch #2 add support for #define'ing __DISABLE_EXPORTS to get rid of
> >> ksymtab/kcrctab sections in decompressor and EFI stub objects when
> >> rebuilding existing C files to run in a different context.
> > I had a small question on patch 3, but it's really for my understanding.
> > So, for patches 1-3:
> > Reviewed-by: Will Deacon <will.deacon@xxxxxxx>
> Thanks all.
> Thomas, Ingo,
> Except for the below tweak against patch #3 for powerpc, which may
> apparently get confused by an input section called .discard without
> any suffixes, this series is good to go, but requires your ack to
> proceed, so I would like to ask you to share your comments and/or
> objections. Also, any suggestions or recommendations regarding the
> route these patches should take are highly appreciated.
Acked-by: Ingo Molnar <mingo@xxxxxxxxxx>
Regarding route - I suspect -mm would be good, or any other tree that does a lot
of cross-arch testing?