kbuild: rust: add CONFIG_RUSTC_CLANG_LLVM_COMPATIBLE

This config detects if Rust and Clang have matching LLVM major version.
All IR or bitcode operations (e.g. LTO) rely on LLVM major version to be
matching, otherwise it may generate errors, or worse, miscompile
silently due to change of IR semantics.

It's usually suggested to use the exact same LLVM version, but this can
be difficult to guarantee. Rust's suggestion [1] is also major-version
only, so I think this check is sufficient for the kernel.

Link: https://doc.rust-lang.org/rustc/linker-plugin-lto.html [1]
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>
Tested-by: Andreas Hindborg <a.hindborg@kernel.org>
Link: https://patch.msgid.link/20260203-inline-helpers-v2-1-beb8547a03c9@google.com
[ Fixed typo. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Gary Guo 2026-02-03 11:34:08 +00:00 committed by Miguel Ojeda
parent 889c8c934d
commit e90f97ce20

View File

@ -82,6 +82,21 @@ config RUSTC_LLVM_VERSION
int
default $(rustc-llvm-version)
config RUSTC_LLVM_MAJOR_VERSION
int
default $(shell,expr $(rustc-llvm-version) / 10000)
config RUSTC_CLANG_LLVM_COMPATIBLE
bool
default y if CC_IS_CLANG && RUSTC_LLVM_MAJOR_VERSION = $(shell,expr $(cc-version) / 10000)
help
This indicates whether Rust and Clang use LLVM of the same major
version.
Operations involving handling LLVM IR or bitcode (e.g. cross-language
LTO) require the same LLVM major version to work properly. For best
compatibility it is recommended that the exact same LLVM is used.
config ARCH_HAS_CC_CAN_LINK
bool