Can't build kernel anymore: amd64 kernel requires linker ifunc support

[Rodney W. Grimes]

> On 16 May 2018 at 09:35, Rodney W. Grimes
> <freebsd-rwg at pdx.rh.cn85.dnsmgr.net> wrote:
> >>
> >> LD=ld.lld make
> >>
> >> is the magic here. The kernel needs a new linker to properly link in the
> >> ifunc, and that's not our ancient ld. lld does it, as does the latter-day
> >> binutils.
> >
> > Since this now seems to be a mandatory thing to get a kernel built
> > can it please be set in the Makefile that is needing it?
> 
> It's already handled by the Makefile that needs it when using the
> normal build process - i.e., "make buildworld buildkernel" (or
> toolchain or kernel-toolchain followed by buildkernel).
> 
> The failure arises when building a kernel the "old" way, using config
> and then and make in the kernel directory. This inherently uses the
> host's linker (/usr/bin/ld), which is too old to link the kernel. We
> can't just add LD=ld.lld to the kernel's Makefile(s), because it would
> break external toolchain and other cases where users use a specific
> linker. I hope to introduce a KERNEL_LD Make variable that controls
> the linker used for the kernel link, but it's more involved than a one
> or two line change for the same reason that we can't just set
> LD=ld.lld.
> 
> ld.lld will start being installed as /usr/bin/ld once these two issues
> are resolved:
...

In the meantime what about reverting the ifunc usage until this
can be done?

> 
> pr227968 [exp-run] Update lang/ghc to 8.4.2, devel/stack to 1.7.1, and
> all the */hs-* ports
> pr214864 [exp-run] test build with lld as /usr/bin/ld
> 
> The exp-run for the first is complete and I believe we are now just
> waiting on the change to be committed. As soon as that happens I will
> ask for another exp-run for the second PR, and will commit the change
> to install lld by default as soon as it completes (assuming
> successfully).
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-- 
Rod Grimes                                                 rgrimes at freebsd.org