Pass -Zpatchable-function-entry=M,M,.discard.patchable_function_entries to rustc when CFI and CALL_OPS are both enabled, so Rust functions get the same prefix NOPs as C functions. The section argument needs Rust 1.98 [1]. Probe for it, and let ARM64_CFI_PERMITS_CALL_OPS accept RUST=y when the probe passes.
[1] https://github.com/rust-lang/rust/pull/157445 Suggested-by: Ben Cressey <[email protected]> Reviewed-by: Ben Cressey <[email protected]> Reviewed-by: Florent Revest (Anthropic) <[email protected]> Assisted-by: LLM Signed-off-by: Jose Fernandez (Anthropic) <[email protected]> --- arch/arm64/Kconfig | 7 ++++++- arch/arm64/Makefile | 3 +++ rust/Makefile | 5 ++++- 3 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index afa566e0fa86c..cad2bdf3456ff 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -282,11 +282,16 @@ config CC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION # https://github.com/llvm/llvm-project/pull/131230 def_bool $(cc-option,-fpatchable-function-entry=1$(comma)1$(comma).discard.patchable_function_entries) +config RUSTC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION + # The section argument needs Rust 1.98.0 or later: + # https://github.com/rust-lang/rust/pull/157445 + def_bool $(rustc-option,-Zpatchable-function-entry=1$(comma)1$(comma).discard.patchable_function_entries) + config ARM64_CFI_PERMITS_CALL_OPS def_bool y depends on CFI depends on CC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION - depends on !RUST + depends on !RUST || RUSTC_HAS_PATCHABLE_FUNCTION_ENTRY_SECTION config ARM64_FUNCTION_PREFIX_NOPS int diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 653c1ed6ef38f..b23430e2b8567 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -152,6 +152,9 @@ ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS),y) -DCC_USING_PATCHABLE_FUNCTION_PREFIX=$(prefix_nops) KBUILD_CFLAGS += $(CFI_PREFIX_CFLAGS) export CFI_PREFIX_CFLAGS + # Rust functions are not patched by ftrace, but they are called indirectly + # from C and make indirect calls themselves, so they need the same prefix. + KBUILD_RUSTFLAGS += -Zpatchable-function-entry=$(prefix_nops),$(prefix_nops),.discard.patchable_function_entries endif else ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_ARGS),y) KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY diff --git a/rust/Makefile b/rust/Makefile index da1a7409d9845..0036cefbed76f 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -432,7 +432,10 @@ rusttest-macros: $(src)/macros/lib.rs \ +$(call if_changed,rustdoc_test) ifdef CONFIG_CC_IS_CLANG -bindgen_c_flags = $(c_flags) +# bindgen generates no code, and its libclang may predate the section +# argument of -fpatchable-function-entry that a kCFI kernel with CALL_OPS +# passes on arm64. +bindgen_c_flags = $(filter-out -fpatchable-function-entry=%,$(c_flags)) else # bindgen relies on libclang to parse C. Ideally, bindgen would support a GCC # plugin backend and/or the Clang driver would be perfectly compatible with GCC. -- 2.52.0
