Messages in this thread | | | Date | Fri, 10 Feb 2023 14:43:56 -0800 | From | Kees Cook <> | Subject | Re: [PATCH v2] rust: allow to use INIT_STACK_ALL_ZERO |
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On February 10, 2023 1:51:41 PM PST, Andrea Righi <andrea.righi@canonical.com> wrote: >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 >going to be removed in the future (as the name of the option suggests), >likely with clang-17. > >So, make sure bindgen is using this extra option if the major version of >the libclang used by bindgen is < 17. > >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 >Signed-off-by: Andrea Righi <andrea.righi@canonical.com> >--- > >Changes in v2: > - check the version of libclang used by bindgen to determine if we need > to pass the additional clang option > > rust/Makefile | 13 +++++++++++++ > 1 file changed, 13 insertions(+) > >diff --git a/rust/Makefile b/rust/Makefile >index ff70c4c916f8..c77d7ce96a85 100644 >--- a/rust/Makefile >+++ b/rust/Makefile >@@ -269,6 +269,19 @@ BINDGEN_TARGET := $(BINDGEN_TARGET_$(SRCARCH)) > # some configurations, with new GCC versions, etc. > bindgen_extra_c_flags = -w --target=$(BINDGEN_TARGET) > >+# Auto variable zero-initialization requires an additional special option with >+# clang that is going to be removed sometimes in the future (likely in >+# clang-17), so make sure to pass this option only if clang supports it >+# (libclang major version < 17). >+# >+# https://github.com/llvm/llvm-project/issues/44842 >+ifdef CONFIG_INIT_STACK_ALL_ZERO >+libclang_maj_ver=$(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) \< 17), 1) >+bindgen_extra_c_flags += -enable-trivial-auto-var-init-zero-knowing-it-will-be-removed-from-clang >+endif >+endif
This logic already exists in the top-level Makefile. How does -ftrivial-auto-var-init=zero make it into bindgen_c_flags normally? (I.e. why does the legacy -enable... option not?)
>+ > bindgen_c_flags = $(filter-out $(bindgen_skip_c_flags), $(c_flags)) \ > $(bindgen_extra_c_flags) > endif
-- Kees Cook
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