Re: [PATCH] arm64: vdso32: Fix '--prefix=' value for newer versions of clang

From: Sedat Dilek <sedat.dilek@gmail.com>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
	stable@vger.kernel.org,
	Masahiro Yamada <yamada.masahiro@socionext.com>
Subject: Re: [PATCH] arm64: vdso32: Fix '--prefix=' value for newer versions of clang
Date: Thu, 23 Jul 2020 06:55:25 +0200	[thread overview]
Message-ID: <CA+icZUUOjYoCoEYyRzBdMoh_Fh4DszWoNhpmapqgYOAt8wHO-g@mail.gmail.com> (raw)
In-Reply-To: <20200723045145.GA448242@ubuntu-n2-xlarge-x86>

On Thu, Jul 23, 2020 at 6:51 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Thu, Jul 23, 2020 at 06:45:07AM +0200, Sedat Dilek wrote:
> > On Thu, Jul 23, 2020 at 6:15 AM Nathan Chancellor
> > <natechancellor@gmail.com> wrote:
> > >
> > > Newer versions of clang only look for $(COMPAT_GCC_TOOLCHAIN_DIR)as [1],
> > > rather than $(COMPAT_GCC_TOOLCHAIN_DIR)$(CROSS_COMPILE_COMPAT)as,
> > > resulting in the following build error:
> > >
> > > $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- \
> > > CROSS_COMPILE_COMPAT=arm-linux-gnueabi- LLVM=1 O=out/aarch64 distclean \
> > > defconfig arch/arm64/kernel/vdso32/
> > > ...
> > > /home/nathan/cbl/toolchains/llvm-binutils/bin/as: unrecognized option '-EL'
> > > clang-12: error: assembler command failed with exit code 1 (use -v to see invocation)
> > > make[3]: *** [arch/arm64/kernel/vdso32/Makefile:181: arch/arm64/kernel/vdso32/note.o] Error 1
> > > ...
> > >
> > > Adding the value of CROSS_COMPILE_COMPAT (adding notdir to account for a
> > > full path for CROSS_COMPILE_COMPAT) fixes this issue, which matches the
> > > solution done for the main Makefile [2].
> > >
> >
> > [ CC Masahiro ]
> >
> > Masahiro added a slightly adapted version of [2] in <kbuild.git#fixes>.
> > Shall this go through kbuild subsystem or folded into [1]?
> >
> > - Sedat -
> >
> > [1] https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=fixes&id=ca9b31f6bb9c6aa9b4e5f0792f39a97bbffb8c51
>
> Sorry, should have cc'd Masahiro, slipped my mind.
>
> Note, I kept this separate as the patches have to go back different
> distances; only 5.7 has working clang support for vdso32, see
> commit a5d442f50a41 ("arm64: vdso32: Enable Clang Compilation") in
> Linus' tree, which appeared in 5.7-rc1 so this only needs to go into
> linux-5.7.y. The main patch needs to back all the way to 4.4 so we would
> need to drop this hunk when backporting, which would be annoying, as the
> main patch backports cleanly to 4.9.
>

Clarify your patch by adding...?

Cc: stable@vger.kernel.org # 5.7

> It could be routed via the kbuild tree but the arm64 maintainers are
> pretty good at getting these fixes into the hands of Linus so I see no
> reason to go around them.
>

As you and arm64 maintainers prefer.

- Sedat -

> Cheers,
> Nathan
>
> > > [1]: https://github.com/llvm/llvm-project/commit/3452a0d8c17f7166f479706b293caf6ac76ffd90
> > > [2]: https://lore.kernel.org/lkml/20200721173125.1273884-1-maskray@google.com/
> > >
> > > Cc: stable@vger.kernel.org
> > > Link: https://github.com/ClangBuiltLinux/linux/issues/1099
> > > Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> > > ---
> > >  arch/arm64/kernel/vdso32/Makefile | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/arch/arm64/kernel/vdso32/Makefile b/arch/arm64/kernel/vdso32/Makefile
> > > index d88148bef6b0..5139a5f19256 100644
> > > --- a/arch/arm64/kernel/vdso32/Makefile
> > > +++ b/arch/arm64/kernel/vdso32/Makefile
> > > @@ -14,7 +14,7 @@ COMPAT_GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE_COMPAT)elfedit))
> > >  COMPAT_GCC_TOOLCHAIN := $(realpath $(COMPAT_GCC_TOOLCHAIN_DIR)/..)
> > >
> > >  CC_COMPAT_CLANG_FLAGS := --target=$(notdir $(CROSS_COMPILE_COMPAT:%-=%))
> > > -CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)
> > > +CC_COMPAT_CLANG_FLAGS += --prefix=$(COMPAT_GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE_COMPAT))
> > >  CC_COMPAT_CLANG_FLAGS += -no-integrated-as -Qunused-arguments
> > >  ifneq ($(COMPAT_GCC_TOOLCHAIN),)
> > >  CC_COMPAT_CLANG_FLAGS += --gcc-toolchain=$(COMPAT_GCC_TOOLCHAIN)
> > >
> > > base-commit: d15be546031cf65a0fc34879beca02fd90fe7ac7
> > > --
> > > 2.28.0.rc1
> > >
> > > --
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