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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Sun, 19 Jun 2022 18:19:51 +0900
Message-ID: <CAK7LNATLXO44AKiJJ=XJDpESPpGyE_4YJqAiav926H2veWiWBw@mail.gmail.com>
Subject: Re: [PATCH] scripts/Makefile.clang: set --target for host based on
 make -v
To:     Nick Desaulniers <ndesaulniers@google.com>
Cc:     Nathan Chancellor <nathan@kernel.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Tom Rix <trix@redhat.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <llvm@lists.linux.dev>
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On Sat, Jun 18, 2022 at 8:26 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Fri, Jun 17, 2022 at 4:21 PM Nathan Chancellor <nathan@kernel.org> wrote:
> >
> > On Fri, Jun 17, 2022 at 01:39:48PM -0700, Nick Desaulniers wrote:
> > > We're working on providing statically linked images of clang to host on
> > > kernel.org. We're building them in Alpine Linux based Docker containers,
> > > which are MUSL based systems.
> > >
> > > In order to keep bootstrapping simpler, I'd like for them to have an
> > > implicit default --target of x86_64-alpine-linux-musl (set via LLVM's
> > > cmake variable LLVM_DEFAULT_TARGET_TRIPLE).
> > >
> > > Similarly, if one were to use a different build of clang meant for a
> > > glibc or bionic based system on a MUSL based host, we'd prefer to use
> > > the correct MUSL based triple for target hosts.
> > >
> > > Borrowed from the Zen of Python: Explicit is better than implicit. Let's
> > > be explicit about the target triple for HOSTCC when building with
> > > HOSTCC=clang or LLVM=1.


If people try to use the clang packaged by you,
I think the same thing will occur on any project.

I do not understand why you are trying to patch the kernel build?


If this is a problem, it is specific to your clang package,
not to the linux kernel.

You need to find a solution in your package.


> > >
> > > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> >
> > I have tested this with a few different distributions on both aarch64
> > and x86_64:
> >
> > Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> > Tested-by: Nathan Chancellor <nathan@kernel.org>
> >
> > One small comment below.
> >
> > > ---
> > >  Makefile               |  3 +--
> > >  scripts/Makefile.clang | 10 ++++++++++
> > >  2 files changed, 11 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/Makefile b/Makefile
> > > index 1a6678d817bd..87712d9b043c 100644
> > > --- a/Makefile
> > > +++ b/Makefile
> > > @@ -600,10 +600,9 @@ endif
> > >  # CC_VERSION_TEXT is referenced from Kconfig (so it needs export),
> > >  # and from include/config/auto.conf.cmd to detect the compiler upgrade.
> > >  CC_VERSION_TEXT = $(subst $(pound),,$(shell LC_ALL=C $(CC) --version 2>/dev/null | head -n 1))
> > > +HOSTCC_VERSION_TEXT = $(subst $(pound),,$(shell LC_ALL=C $(HOSTCC) --version 2>/dev/null | head -n 1))
> > >
> > > -ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
> > >  include $(srctree)/scripts/Makefile.clang
> > > -endif
> > >
> > >  # Include this also for config targets because some architectures need
> > >  # cc-cross-prefix to determine CROSS_COMPILE.
> > > diff --git a/scripts/Makefile.clang b/scripts/Makefile.clang
> > > index 87285b76adb2..a4505cd62d7b 100644
> > > --- a/scripts/Makefile.clang
> > > +++ b/scripts/Makefile.clang
> > > @@ -1,3 +1,4 @@
> > > +ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
> > >  # Individual arch/{arch}/Makefiles should use -EL/-EB to set intended
> > >  # endianness and -m32/-m64 to set word size based on Kconfigs instead of
> > >  # relying on the target triple.
> > > @@ -39,3 +40,12 @@ CLANG_FLAGS        += -Werror=ignored-optimization-argument
> > >  KBUILD_CFLAGS        += $(CLANG_FLAGS)
> > >  KBUILD_AFLAGS        += $(CLANG_FLAGS)
> > >  export CLANG_FLAGS
> > > +endif
> > > +
> > > +# If HOSTCC is clang, set the host target triple explicitly; do not rely on
> > > +# implicit defaults.
> > > +ifneq ($(findstring clang,$(HOSTCC_VERSION_TEXT)),)
> > > +HOST_TRIPLE          := --target=$(shell make --version | head -n2 | tail -n1 | cut -d ' ' -f 3)
> >
> > Should we use $(MAKE) instead of make here? I guess the only case where
>
> oh! yeah, good call. I think so.  Will wait until next Tuesday
> (Juneteenth holiday in the US on Monday) to send a v2. Thanks for
> taking a look!
>
> > it would matter is if someone was calling make via an explicit path and
> > did not have it available in their PATH so maybe it is not worth
> > worrying about.
> >
> > > +KBUILD_HOSTCFLAGS    += $(HOST_TRIPLE)
> > > +KBUILD_HOSTLDFLAGS   += $(HOST_TRIPLE)
> > > +endif
> > >
> > > base-commit: 79fe0f863f920c5fcf9dea61676742f813f0b7a6
> > > --
> > > 2.36.1.476.g0c4daa206d-goog
> > >
> > >
>
>
>
> --
> Thanks,
> ~Nick Desaulniers


--
Best Regards
Masahiro Yamada