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Date:   Wed, 23 Jun 2021 21:06:41 -0700
From:   Nathan Chancellor <nathan@kernel.org>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Christoph Hellwig <hch@lst.de>, Brian Cain <bcain@codeaurora.org>,
        Sid Manning <sidneym@codeaurora.org>,
        linux-hexagon@vger.kernel.org, linux-kernel@vger.kernel.org,
        Nick Desaulniers <ndesaulniers@google.com>,
        clang-built-linux@googlegroups.com
Subject: Re: how can we test the hexagon port in mainline
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On Wed, Jun 23, 2021 at 05:35:38PM +0200, Arnd Bergmann wrote:
> On Wed, Jun 23, 2021 at 5:17 PM Christoph Hellwig <hch@lst.de> wrote:
> >
> > It seem like it still isn't complete enought for a kernel build, though:
> >
> > $ export CROSS_COMPILE=/opt/clang+llvm-12.0.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin/hexagon-unknown-linux-musl-
> > $ make ARCH=hexagon LLVM=1 oldconfig
> > ...
> > scripts/Kconfig.include:40: linker 'ld.lld' not found
> 
> I tried this using the prebuilt binaries from apt.llvm.org:
> 
> $ make ARCH=hexagon LLVM=1 O=obj-hexagon CROSS_COMPILE=hexagon-linux-
> LLVM_IAS=1 CC=llvm-12 defconfig modules vmlinux
> <stdin>:1515:2: warning: syscall clone3 not implemented [-W#warnings]
> #warning syscall clone3 not implemented
>  ^
> 1 warning generated.
> 
> Doing the same thing with allmodconfig results in an internal error
> with clang-12
> while compiling kernel/locking/lockdep.c. Same thing with clang-13.
> After turning
> off lock debugging, it seems fine.

I've reported this upstream with you on CC:

https://bugs.llvm.org/show_bug.cgi?id=50838

Christoph, that toolchain should work (I had to install libtinfo5 and
libc++1-7 on Debian Buster):

$ export PATH=$HOME/tmp/clang+llvm-12.0.0-cross-hexagon-unknown-linux-musl/x86_64-linux-gnu/bin:$PATH

$ make -skj"$(nproc)" ARCH=hexagon CROSS_COMPILE=hexagon-unknown-linux-musl LLVM=1 LLVM_IAS=1 defconfig all

CROSS_COMPILE is really only used to set the '--target=' flag when
LLVM=1 LLVM_IAS=1 are used, it can even be just 'hexagon-linux'.

As Arnd points out, https://apt.llvm.org is also an option, that is what
we use in our continuous integration:

https://github.com/ClangBuiltLinux/continuous-integration2

Cheers,
Nathan