[PATCH 1/2] kbuild: rust: add `CONFIG_RUSTC_LLVM_VERSION`

Alice Ryhl
2024-10-10T09:38:38Z

From: Gary Guo <gary@garyguo.net>

Each version of Rust supports a range of LLVM versions. There are cases where
we want to gate a config on the LLVM version instead of the Rust version.
Normalized cfi integer tags are one example [1].

For consistency with cc-version and ld-version, the new version number is added
to the existing rustc-version script, rather than being added to a new script.

The invocation of rustc-version is being moved from init/Kconfig to
scripts/Kconfig.include to avoid invoking rustc-version.sh twice and for
consistency with cc-version.

Link: https://lore.kernel.org/all/20240925-cfi-norm-kasan-fix-v1-1-0328985cdf33@google.com/ [1]
Signed-off-by: Gary Guo <gary@garyguo.net>
---
init/Kconfig | 6 +++++-
scripts/Kconfig.include | 4 ++++
scripts/rustc-version.sh | 31 +++++++++++++++++++++++++------
3 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 530a382ee0fe..98cf859d58c2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -62,7 +62,7 @@ config LLD_VERSION

config RUSTC_VERSION
int
- default $(shell,$(srctree)/scripts/rustc-version.sh $(RUSTC))
+ default $(rustc-version)
help
It does not depend on `RUST` since that one may need to use the version
in a `depends on`.
@@ -78,6 +78,10 @@ config RUST_IS_AVAILABLE
In particular, the Makefile target 'rustavailable' is useful to check
why the Rust toolchain is not being detected.

+config RUSTC_LLVM_VERSION
+ int
+ default $(rustc-llvm-version)
+
config CC_CAN_LINK
bool
default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(USERCFLAGS) $(USERLDFLAGS) $(m64-flag)) if 64BIT
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 785a491e5996..788097a55731 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -65,6 +65,10 @@ cc-option-bit = $(if-success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null,$
m32-flag := $(cc-option-bit,-m32)
m64-flag := $(cc-option-bit,-m64)

+rustc-info := $(shell,$(srctree)/scripts/rustc-version.sh $(RUSTC))
+rustc-version := $(shell,set -- $(rustc-info) && echo $1)
+rustc-llvm-version := $(shell,set -- $(rustc-info) && echo $2)
+
# $(rustc-option,<flag>)
# Return y if the Rust compiler supports <flag>, n otherwise
# Calls to this should be guarded so that they are not evaluated if
diff --git a/scripts/rustc-version.sh b/scripts/rustc-version.sh
index 4e22593e2eab..24e19ed8f234 100755
--- a/scripts/rustc-version.sh
+++ b/scripts/rustc-version.sh
@@ -3,14 +3,23 @@
#
# Usage: $ ./rustc-version.sh rustc
#
-# Print the Rust compiler version in a 6 or 7-digit form.
+# Print the Rust compiler version and the LLVM version it uses in a 6 or
+# 7-digit form.
+
+# Convert the version string x.y.z to a canonical up-to-6-digits form.
+get_llvm_canonical_version()
+{
+ IFS=.
+ set -- $1
+ echo $((10000 * $1 + 100 * $2 + $3))
+}

# 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
+# Note that this function uses one more digit (compared to other instances in
+# other version scripts and the instance above) to give a bit more space to
# `rustc` since it will reach 1.100.0 in late 2026.
-get_canonical_version()
+get_rustc_canonical_version()
{
IFS=.
set -- $1
@@ -19,8 +28,18 @@ get_canonical_version()

if output=$("$@" --version 2>/dev/null); then
set -- $output
- get_canonical_version $2
+ rustc_version=$(get_rustc_canonical_version $2)
else
- echo 0
+ echo 0 0
exit 1
fi
+
+if output=$("$@" --version --verbose 2>/dev/null | grep LLVM); then
+ set -- $output
+ rustc_llvm_version=$(get_llvm_canonical_version $3)
+else
+ echo 0 0
+ exit 1
+fi
+
+echo $rustc_version $rustc_llvm_version

--
2.47.0.rc0.187.ge670bccf7e-goog