Re: git: 349cc55c9796 - main - Merge llvm-project main llvmorg-14-init-10186-gff7f2cfa959b

On Tue, May 17, 2022 at 10:56:14AM -0700, John Baldwin wrote:
> On 5/16/22 8:09 PM, Charlie Li wrote:
> > Brooks Davis wrote:
> > > On Mon, May 16, 2022 at 10:47:49AM -0400, Charlie Li wrote:
> > > > Dimitry Andric wrote:
> > > > > This was also reported by another user, and it turned out they were
> > > > > using WITHOUT_CROSS_COMPILER= in src.conf. If you also have that, try
> > > > > removing it and rebuilding.
> > > > > 
> > > > Yeah I eventually figured that part out. Worked around (first attempt)
> > > > by building with devel/llvm14 CROSS_TOOLCHAIN, but resulted in certain
> > > > kernel modules (zfs and a few more) with malformed relocations.
> > > > Subsequent rebuild with the new world's toolchain corrected that.
> > > 
> > > Does that mean we're missing patches in the port?  Hopefully anything
> > > this critical can be merged into LLVM 14.0.3.
> > > 
> > Probably:
> > 
> > May 15 22:34:08 current-builder kernel: ---<<BOOT>>---
> > May 15 22:34:08 current-builder kernel: Copyright (c) 1992-2022 The
> > FreeBSD Project.
> > May 15 22:34:08 current-builder kernel: Copyright (c) 1979, 1980, 1983,
> > 1986, 1988, 1989, 1991, 1992, 1993, 1994
> > May 15 22:34:08 current-builder kernel:         The Regents of the
> > University of California. All rights reserved.
> > May 15 22:34:08 current-builder kernel: FreeBSD is a registered
> > trademark of The FreeBSD Foundation.
> > May 15 22:34:08 current-builder kernel: FreeBSD 14.0-CURRENT #121
> > main-n255657-48a1a6be196: Sun May 15 21:59:12 EDT 2022
> > May 15 22:34:08 current-builder kernel:
> > root@current-builder:/usr/obj/usr/src/amd64.amd64/sys/GENERIC-NODEBUG amd64
> > May 15 22:34:08 current-builder kernel: clang version 14.0.2
> > [...]
> > May 15 22:34:08 current-builder kernel: kldload: unexpected relocation
> > type 42, symbol index 8321
> 
> These are all type 42:
> 
> #define	R_X86_64_REX_GOTPCRELX	42
> 
> It's not a LLVM bug so much as it is probably missing support in the kernel and/or
> loader for this type of relocation.  kldxref might also need updating.
> 
> I suspect due to a mismatch of old lld with new clang or some such that the old
> lld failed to resolve these relocations to some other type or something weird like
> that?

I do think this is a toolchain bug, or at least new and undesired behavior.

For practical purposes, R_X86_64_GOTPCRELX and R_X86_64_REX_GOTPCRELX are
same as R_X86_64_GOTPCREL64, I believe, but we do not expect GOT relocations
in the .o object modules on amd64.