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rust: allow to use INIT_STACK_ALL_ZERO

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With CONFIG_INIT_STACK_ALL_ZERO enabled, bindgen passes
-ftrivial-auto-var-init=zero to clang, that triggers the following
error:

 error: '-ftrivial-auto-var-init=zero' hasn't been enabled; enable it at your own peril for benchmarking purpose only with '-enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang'

However, this additional option that is currently required by clang is
deprecated since clang-16 and going to be removed in the future,
likely with clang-18.

So, make sure bindgen is using this extra option if the major version of
the libclang used by bindgen is < 16.

In this way we can enable CONFIG_INIT_STACK_ALL_ZERO with CONFIG_RUST
without triggering any build error.

Link: https://github.com/llvm/llvm-project/issues/44842
Link: https://github.com/llvm/llvm-project/blob/llvmorg-16.0.0-rc2/clang/docs/ReleaseNotes.rst#deprecated-compiler-flags
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
[Changed to < 16, added link and reworded]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Andrea Righi 2023-02-10 22:51:41 +01:00 committed by Miguel Ojeda
parent ccc4505454
commit d966c3cab9
1 changed files with 14 additions and 0 deletions
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14
rust/Makefile
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@ -262,6 +262,20 @@ BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH))
# some configurations, with new GCC versions, etc.
bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET)
# Auto variable zero-initialization requires an additional special option with
# clang that is going to be removed sometime in the future (likely in
# clang-18), so make sure to pass this option only if clang supports it
# (libclang major version < 16).
#
# https://github.com/llvm/llvm-project/issues/44842
# https://github.com/llvm/llvm-project/blob/llvmorg-16.0.0-rc2/clang/docs/ReleaseNotes.rst#deprecated-compiler-flags
ifdef CONFIG_INIT_STACK_ALL_ZERO
libclang_maj_ver=$(shell $(BINDGEN) $(srctree)/scripts/rust_is_available_bindgen_libclang.h 2>&1 | sed -ne 's/.*clang version \([0-9]*\).*/\1/p')
ifeq ($(shell expr $(libclang_maj_ver) \< 16), 1)
bindgen_extra_c_flags += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang
endif
endif
bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \
$(bindgen_extra_c_flags)
endif