Re: [PATCH 11/13] kbuild: rust: add `rustc-version` support

[Finn Behrens]

On 1 Jul 2024, at 20:36, Miguel Ojeda wrote:

> Now that we are starting to support several Rust versions, introduce
> `rustc-version` support, mimicking the C side:
>
>   - `scripts/rustc-version.sh`, that mimics the other version scripts
>      (with one more digit, e.g. Rust 1.79.0 is 107900).
>
>   - `rustc-{info,name,version}` Kbuild macros.
>
>   - `CONFIG_RUSTC_VERSION` Kconfig symbol that calls `rustc-version`.
>
>   - `rustc-min-version` Kbuild macro that uses `CONFIG_RUSTC_VERSION`.
>
> With these, we can easily support flags conditionally depending on
> `rustc`'s version -- a user comes in the next patch.
>
> Another user will be the `-Ctarget-feature=+reserve-x18`/`-Zfixed-x18`
> arm64 flags [1].
>
> Link: https://lore.kernel.org/rust-for-linux/20240305-shadow-call-stack-v2-1-c7b4a3f4d616@xxxxxxxxxx/ [1]
> Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>

Reviewed-by: Finn Behrens <me@xxxxxxxxxx>

> ---
>  init/Kconfig              |  6 +++++
>  scripts/Kconfig.include   |  6 +++++
>  scripts/Makefile.compiler |  4 +++
>  scripts/rustc-version.sh  | 52 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 68 insertions(+)
>  create mode 100755 scripts/rustc-version.sh
>
> diff --git a/init/Kconfig b/init/Kconfig
> index 94e20d3b99d4..7d344f248785 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1920,6 +1920,12 @@ config RUST
>
>  	  If unsure, say N.
>
> +config RUSTC_VERSION
> +	int
> +	depends on RUST
> +	default $(rustc-version)
> +	default 0
> +
>  config RUSTC_VERSION_TEXT
>  	string
>  	depends on RUST
> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> index 3ee8ecfb8c04..82ab889725db 100644
> --- a/scripts/Kconfig.include
> +++ b/scripts/Kconfig.include
> @@ -45,6 +45,12 @@ $(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this C compiler is not
>  cc-name := $(shell,set -- $(cc-info) && echo $1)
>  cc-version := $(shell,set -- $(cc-info) && echo $2)
>
> +# Get the Rust compiler name, version, and error out if it is not supported.
> +rustc-info := $(shell,$(srctree)/scripts/rustc-version.sh $(RUSTC))
> +$(error-if,$(success,test -z "$(rustc-info)"),Sorry$(comma) this Rust compiler is not supported.)
> +rustc-name := $(shell,set -- $(rustc-info) && echo $1)
> +rustc-version := $(shell,set -- $(rustc-info) && echo $2)
> +
>  # Get the assembler name, version, and error out if it is not supported.
>  as-info := $(shell,$(srctree)/scripts/as-version.sh $(CC) $(CLANG_FLAGS))
>  $(error-if,$(success,test -z "$(as-info)"),Sorry$(comma) this assembler is not supported.)
> diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
> index 92be0c9a13ee..17eaa085b59c 100644
> --- a/scripts/Makefile.compiler
> +++ b/scripts/Makefile.compiler
> @@ -69,6 +69,10 @@ gcc-min-version = $(call test-ge, $(CONFIG_GCC_VERSION), $1)
>  # Usage: cflags-$(call clang-min-version, 110000) += -foo
>  clang-min-version = $(call test-ge, $(CONFIG_CLANG_VERSION), $1)
>
> +# rustc-min-version
> +# Usage: rustflags-$(call rustc-min-version, 107900) += -foo
> +rustc-min-version = $(call test-ge, $(CONFIG_RUSTC_VERSION), $1)
> +
>  # ld-option
>  # Usage: KBUILD_LDFLAGS += $(call ld-option, -X, -Y)
>  ld-option = $(call try-run, $(LD) $(KBUILD_LDFLAGS) $(1) -v,$(1),$(2),$(3))
> diff --git a/scripts/rustc-version.sh b/scripts/rustc-version.sh
> new file mode 100755
> index 000000000000..4e658fd55ae6
> --- /dev/null
> +++ b/scripts/rustc-version.sh
> @@ -0,0 +1,52 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Print the Rust compiler name and its version in a 5 or 6-digit form.
> +# Also, perform the minimum version check.
> +
> +set -e
> +
> +# Convert the version string x.y.z to a canonical up-to-7-digits form.
> +#
> +# Note that this function uses one more digit (compared to other
> +# instances in other version scripts) to give a bit more space to
> +# `rustc` since it will reach 1.100.0 in late 2026.
> +get_canonical_version()
> +{
> +	IFS=.
> +	set -- $1
> +	echo $((100000 * $1 + 100 * $2 + $3))
> +}
> +
> +orig_args="$@"
> +
> +set -- $("$@" --version)
> +
> +name=$1
> +
> +min_tool_version=$(dirname $0)/min-tool-version.sh
> +
> +case "$name" in
> +rustc)
> +	version=$2
> +	min_version=$($min_tool_version rustc)
> +	;;
> +*)
> +	echo "$orig_args: unknown Rust compiler" >&2
> +	exit 1
> +	;;
> +esac
> +
> +rustcversion=$(get_canonical_version $version)
> +min_rustcversion=$(get_canonical_version $min_version)
> +
> +if [ "$rustcversion" -lt "$min_rustcversion" ]; then
> +	echo >&2 "***"
> +	echo >&2 "*** Rust compiler is too old."
> +	echo >&2 "***   Your $name version:    $version"
> +	echo >&2 "***   Minimum $name version: $min_version"
> +	echo >&2 "***"
> +	exit 1
> +fi
> +
> +echo $name $rustcversion
> -- 
> 2.45.2