Date: Thu, 16 Aug 2018 07:49:04 -0700 From: Mark Millard <marklmi@yahoo.com> To: Warner Losh <imp@bsdimp.com> Cc: Ed Maste <emaste@freebsd.org>, "freebsd-toolchain@FreeBSD.org" <freebsd-toolchain@freebsd.org>, Dimitry Andric <dim@freebsd.org> Subject: Re: Broken arm support in clang now? Message-ID: <FE00838E-6EC8-4923-A068-0C9566A22F97@yahoo.com> In-Reply-To: <CANCZdfpFr3vZYt9SS46wtutEdXR7e3QqS2WiFA2usrkrqAY%2B3w@mail.gmail.com> References: <CANCZdfpmDN-nAkViuEx-tKpPhOdRYX=xNu6s8E2o6F4xC2WPnA@mail.gmail.com> <1880880F-9D9D-47E0-A7A4-5369A3770F89@FreeBSD.org> <CANCZdfpF9ND_k2xvZrsDebsZ07p2RU0Lebp5GDtmxnjdXc=N-A@mail.gmail.com> <A5B46840-B508-4F40-9EFD-50D0439EBAC7@FreeBSD.org> <8B467E75-A6D3-41A5-8EA1-4DDFE0E14CC5@nexustechnology.com> <CANCZdfq4NmT6_W9MwSMC8r4fQfxW8fWyh1pOX5snnVLNEvew9A@mail.gmail.com> <230C1E7D-04DB-4E45-8A40-F6B2F5E557E9@yahoo.com> <CAPyFy2DW86vT2bJBpoznCkB6U8HTYFyYH29Sb=-aCBPd65a=Qg@mail.gmail.com> <86844298-1268-4F5E-A6CD-64CADC022FB9@yahoo.com> <CANCZdfpFr3vZYt9SS46wtutEdXR7e3QqS2WiFA2usrkrqAY%2B3w@mail.gmail.com>
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> On 2018-Aug-16, at 7:16 AM, Warner Losh <imp at bsdimp.com> wrote:
>=20
> On Thu, Aug 16, 2018 at 8:14 AM, Mark Millard <marklmiat yahoo.com> =
wrote:
>> On 2018-Aug-16, at 6:38 AM, Ed Maste <emaste at freebsd.org> wrote:
>>=20
>> > On 11 August 2018 at 20:45, Mark Millard via freebsd-toolchain
>> > <freebsd-toolchain at freebsd.org> wrote:
>> >>=20
>> >> Is the link command itself available? (The =
.../sys/*/kernel.full.meta
>> >> likely has it if it is still around.)
>> >=20
>> > I tried a tinderbox build right now and saw the lld warnings from
>> > linking zfs.ko. It appears to be fallout from the change to build
>> > clang and lld only once for tinderbox, because we're invoking ld =
from
>> > the ${HOST_TARGET} path:
>> >=20
>> > =
/scratch/tmp/emaste/obj/scratch/tmp/emaste/freebsd/freebsd11-amd64/tmp/usr=
/bin/ld
>> > -m armelf_fbsd -Bshareable -znotext -d -warn-common --build-id=3Dsha1=
>> > -o zfs.ko.full zfs.kld
>> > =
/scratch/tmp/emaste/obj/scratch/tmp/emaste/freebsd/freebsd11-amd64/tmp/usr=
/bin/ld:
>> > warning: lld uses extended branch encoding, no object with
>> > architecture supporting feature detected.
>> > =
/scratch/tmp/emaste/obj/scratch/tmp/emaste/freebsd/freebsd11-amd64/tmp/usr=
/bin/ld:
>> > warning: lld may use movt/movw, no object with architecture =
supporting
>> > feature detected.
>>=20
>> So ld.lld is not a valid cross linker for some arm variants? A
>> architecture specific bootstrap one is needed?
>>=20
>> Is this because armelf_fbsd is not specific enough to
>> identify the accurate target emulation? Is it because
>> the .o's are not sufficient for that identification?
>>=20
>> Note: I got the questions from reading the output in:
>>=20
>> # ld.lld=20
>> ld.lld: error: no input files
>> ld.lld: error: target emulation unknown: -m or at least one .o file =
required
>>=20
>> So it appears that -m and/or .o's are used to identify targets.
>> I'm not clear on the criteria when both are present.
>>=20
>> (ld.lld does not take -target as an argument.)
>>=20
> lld uses instructions and features introduced in armv7 unconditionally =
to do its linking. The bug appears to be that clang invokes it =
unconditionally in some cases.
Ahh. Okay. 32-bit non-armv7+ cannot be fully llvm based.
Intersting.
But I took Ed M.'s text to be based on the .meta file where
he listed:
=
/scratch/tmp/emaste/obj/scratch/tmp/emaste/freebsd/freebsd11-amd64/tmp/usr=
/bin/ld -m armelf_fbsd -Bshareable -znotext -d -warn-common =
--build-id=3Dsha1 -o zfs.ko.full zfs.kld
The implication would be that ld was then directly
invoked instead of via cc (clang).
Looking at a armv7 build I happen to have around:
# more =
/usr/obj/cortexA53_clang/arm64.aarch64/usr/src/arm64.aarch64/sys/GENERIC-N=
ODBG/modules/usr/src/sys/modules/zfs/zfs.ko.full.meta
# Meta data file =
/usr/obj/cortexA53_clang/arm64.aarch64/usr/src/arm64.aarch64/sys/GENERIC-N=
ODBG/modules/usr/src/sys/modules/zfs/zfs.ko.full.meta
CMD ld -m aarch64elf -Bshareable -znotext -d -warn-common =
--build-id=3Dsha1 -o zfs.ko.full zfs.kld
CWD =
/usr/obj/cortexA53_clang/arm64.aarch64/usr/src/arm64.aarch64/sys/GENERIC-N=
ODBG/modules/usr/src/sys/modules/zfs
TARGET zfs.ko.full
-- command output --
It looks like ld was directly invoked instead of being
done via a cc command for my amd64 -> armv7 cross build
example.
=3D=3D=3D
Mark Millard
marklmi at yahoo.com
( dsl-only.net went
away in early 2018-Mar)
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