On Tue, May 05, 2026 at 01:40:50PM +0200, Peter Zijlstra wrote:

On Tue, May 05, 2026 at 02:16:22PM +0530, Sathvika Vasireddy wrote:

quoted

This patch series implements build-time fixup of alternate feature
relative addresses for powerpc.

Previously, Nicholas Piggin proposed a build-time solution using a
custom PowerPC tool [1], which provided the foundation for this approach.
The current implementation leverages objtool's existing ELF parsing
infrastructure to do the same.

This patchset applies atop powerpc/merge branch.

[1] Original PowerPC tool approach:
    http://patchwork.ozlabs.org/project/linuxppc-dev/patch/20170521010130.13552-1-npiggin@gmail.com/

Testing:
Build and Boot tested on ppc64le, ppc64be, and ppc32be configs.

Sathvika Vasireddy (6):
  objtool/powerpc: Add build-time fixup of alternate feature branch
    targets
  objtool: Set ELF_F_LAYOUT flag to preserve vmlinux segment layout
  objtool: Fix "can't find starting instruction" warnings on vmlinux
  objtool/powerpc: Skip jump destination analysis and unnanotated
    intra-function call warnings for --ftr-fixup
  kbuild: Add objtool integration for PowerPC feature fixups
  powerpc: Enable build-time feature fixup processing by default

Ooh, so 2/3 are because you're not running objtool on vmlinux.o, but
you're running it later in the link stage?

AFAICT ELF_F_LAYOUT should not hurt the normal objtool run, but it
shouldn't be needed either, because we run much earlier, before sections
are placed.

And that also explains why you're the first to have trouble with 'can't
find starting instruction'. vmlinux.o will have unplaced sections that
are all relative 0.

Hmm... perhaps this ftr fixup should be its own command, like klp. Not
munged into check thing. Josh?

Hi Peter,

As the original author for the patch series will not be working on this
feature anymore, I'd like to take over and move this feature forward.

Your point about only using objtool at object stage, makes sense.
Would you prefer if I rework this as a saperate tool then?

Regards
~Shivang