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SubjectRe: [PATCH 2/2] kbuild: Disable CONFIG_LD_ORPHAN_WARN for ld.lld 10.0.1
On Fri, Nov 13, 2020 at 11:56 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> ld.lld 10.0.1 spews a bunch of various warnings about .rela sections,
> along with a few others. Newer versions of ld.lld do not have these
> warnings. As a result, do not add '--orphan-handling=warn' to
> LDFLAGS_vmlinux if ld.lld's version is not new enough.
>
> Reported-by: Arvind Sankar <nivedita@alum.mit.edu>
> Reported-by: kernelci.org bot <bot@kernelci.org>
> Reported-by: Mark Brown <broonie@kernel.org>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1187
> Link: https://github.com/ClangBuiltLinux/linux/issues/1193
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
> MAINTAINERS | 1 +
> init/Kconfig | 6 +++++-
> scripts/lld-version.sh | 20 ++++++++++++++++++++
> 3 files changed, 26 insertions(+), 1 deletion(-)
> create mode 100755 scripts/lld-version.sh
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3da6d8c154e4..4b83d3591ec7 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -4284,6 +4284,7 @@ B: https://github.com/ClangBuiltLinux/linux/issues
> C: irc://chat.freenode.net/clangbuiltlinux
> F: Documentation/kbuild/llvm.rst
> F: scripts/clang-tools/
> +F: scripts/lld-version.sh
> K: \b(?i:clang|llvm)\b
>
> CLEANCACHE API
> diff --git a/init/Kconfig b/init/Kconfig
> index a270716562de..40c9ca60ac1d 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -47,6 +47,10 @@ config CLANG_VERSION
> int
> default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
>
> +config LLD_VERSION
> + int
> + default $(shell,$(srctree)/scripts/lld-version.sh $(LD))
> +
> config CC_CAN_LINK
> bool
> default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag)) if 64BIT
> @@ -1349,7 +1353,7 @@ config LD_DEAD_CODE_DATA_ELIMINATION
> own risk.
>
> config LD_ORPHAN_WARN
> - def_bool ARCH_WANT_LD_ORPHAN_WARN && $(ld-option,--orphan-handling=warn)
> + def_bool ARCH_WANT_LD_ORPHAN_WARN && $(ld-option,--orphan-handling=warn) && (!LD_IS_LLD || LLD_VERSION >= 110000)
>
> config SYSCTL
> bool
> diff --git a/scripts/lld-version.sh b/scripts/lld-version.sh
> new file mode 100755
> index 000000000000..cc779f412e39
> --- /dev/null
> +++ b/scripts/lld-version.sh
> @@ -0,0 +1,20 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# ld.lld-version ld.lld-command

^ it looks like this format was copied from scripts/gcc-version, but
it's kind of curious/cryptic to me for a comment about usage. Is it
necessary? A comment in the form:

# Usage: ./scripts/lld-version.sh ld.lld

Would be clearer to me.

> +#
> +# Print the linker version of `ld.lld-command' in a 5 or 6-digit form
> +# such as `100001' for ld.lld 10.0.1 etc.
> +
> +linker="$*"
> +
> +if ! ( $linker --version | grep -q LLD ); then
> + echo 0
> + exit 1
> +fi
> +
> +VERSION=$($linker --version | cut -d ' ' -f 2)

This is going to invoke the linker potentially twice if it's LLD.
Would it be nicer to capture the output of `$linker --version`, check
which linker it is, then slice that up via `cut` to get the version?

This version is fine to me, but if you're going to send a v2, that
might be a nice slight cleanup. Otherwise,

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>

(Please drop those tags if you modify this for v2 and I'll rereview/retest).

> +MAJOR=$(echo $VERSION | cut -d . -f 1)
> +MINOR=$(echo $VERSION | cut -d . -f 2)
> +PATCHLEVEL=$(echo $VERSION | cut -d . -f 3)
> +printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL
> --
> 2.29.2
>


--
Thanks,
~Nick Desaulniers

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