kbuild: rust: Define probing macros for rustc

Creates flag probe macro variants for `rustc`. These are helpful
because:

1. The kernel now supports a minimum `rustc` version rather than a
   single version.
2. `rustc` links against a range of LLVM revisions, occasionally even
   ones without an official release number. Since the availability of
   some Rust flags depends on which LLVM it has been linked against,
   probing is necessary.

Signed-off-by: Matthew Maurer <mmaurer@google.com>
Link: https://github.com/Rust-for-Linux/linux/pull/1087
Link: https://lore.kernel.org/r/20240820194910.187826-2-mmaurer@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 3500a3d62f0df29d1d3c59e002127b44bf21811d..785a491e599689b7f1f3c33d22c19d5ebc63ba53 100644 (file)
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -64,3 +64,11 @@ ld-version := $(shell,set -- $(ld-info) && echo $2)
 cc-option-bit = $(if-success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null,$(1))
 m32-flag := $(cc-option-bit,-m32)
 m64-flag := $(cc-option-bit,-m64)
+
+# $(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
+# CONFIG_RUST_IS_AVAILABLE is not set.
+# If you are testing for unstable features, consider testing RUSTC_VERSION
+# instead, as features may have different completeness while available.
+rustc-option = $(success,trap "rm -rf .tmp_$$" EXIT; mkdir .tmp_$$; $(RUSTC) $(1) --crate-type=rlib /dev/null --out-dir=.tmp_$$ -o .tmp_$$/tmp.rlib)

diff --git a/scripts/Makefile.compiler b/scripts/Makefile.compiler
index 92be0c9a13eeb51beca06abe15bfe22c6e72bfcb..057305eae85c6da49d1cf110a48bd49adee4d0fd 100644 (file)
--- a/scripts/Makefile.compiler
+++ b/scripts/Makefile.compiler
@@ -72,3 +72,18 @@ clang-min-version = $(call test-ge, $(CONFIG_CLANG_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))
+
+# __rustc-option
+# Usage: MY_RUSTFLAGS += $(call __rustc-option,$(RUSTC),$(MY_RUSTFLAGS),-Cinstrument-coverage,-Zinstrument-coverage)
+__rustc-option = $(call try-run,\
+       $(1) $(2) $(3) --crate-type=rlib /dev/null --out-dir=$$TMPOUT -o "$$TMP",$(3),$(4))
+
+# rustc-option
+# Usage: rustflags-y += $(call rustc-option,-Cinstrument-coverage,-Zinstrument-coverage)
+rustc-option = $(call __rustc-option, $(RUSTC),\
+       $(KBUILD_RUSTFLAGS),$(1),$(2))
+
+# rustc-option-yn
+# Usage: flag := $(call rustc-option-yn,-Cinstrument-coverage)
+rustc-option-yn = $(call try-run,\
+       $(RUSTC) $(KBUILD_RUSTFLAGS) $(1) --crate-type=rlib /dev/null --out-dir=$$TMPOUT -o "$$TMP",y,n)