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charset="utf-8" The KCFI sanitizer stores the CFI tag of a function just before its machine code. However, the patchable-function-entry flag can be used to introduce additional nop instructions before the machine code, taking up the space that normally holds the CFI tag. In this case, a backwards offset is applied to the CFI tag to move them out of the way of the nop instructions. To ensure that C and Rust agree on the offset used by CFI tags, pass the -Zpatchable-function-entry to rustc whenever it is passed to the C compiler. The required rustc version is bumped to 1.81.0 to ensure that the -Zpatchable-function-entry flag is available when CFI is used. Fixes: ca627e636551 ("rust: cfi: add support for CFI_CLANG with Rust") Signed-off-by: Alice Ryhl --- Note that this fix uses rustc-option which has a pending fix: https://lore.kernel.org/all/20241008-rustc-option-bootstrap-v2-1-e6e155b8f9f3@google.com/ --- arch/arm64/Makefile | 2 ++ arch/loongarch/Makefile | 1 + arch/riscv/Makefile | 2 ++ init/Kconfig | 2 +- 4 files changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index 9efd3f37c2fd..d7ec0bb09fc4 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -143,9 +143,11 @@ CHECKFLAGS += -D__aarch64__ ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_CALL_OPS),y) KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY CC_FLAGS_FTRACE := -fpatchable-function-entry=4,2 + KBUILD_RUSTFLAGS += $(call rustc-option,-Zpatchable-function-entry=4$(comma)2) else ifeq ($(CONFIG_DYNAMIC_FTRACE_WITH_ARGS),y) KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY CC_FLAGS_FTRACE := -fpatchable-function-entry=2 + KBUILD_RUSTFLAGS += $(call rustc-option,-Zpatchable-function-entry=2) endif ifeq ($(CONFIG_KASAN_SW_TAGS), y) diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile index ae3f80622f4c..f9cef31d1f0e 100644 --- a/arch/loongarch/Makefile +++ b/arch/loongarch/Makefile @@ -44,6 +44,7 @@ endif ifdef CONFIG_DYNAMIC_FTRACE KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY CC_FLAGS_FTRACE := -fpatchable-function-entry=2 +KBUILD_RUSTFLAGS += $(call rustc-option,-Zpatchable-function-entry=2) endif ifdef CONFIG_64BIT diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile index d469db9f46f4..65d4dcba309a 100644 --- a/arch/riscv/Makefile +++ b/arch/riscv/Makefile @@ -16,8 +16,10 @@ ifeq ($(CONFIG_DYNAMIC_FTRACE),y) KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY ifeq ($(CONFIG_RISCV_ISA_C),y) CC_FLAGS_FTRACE := -fpatchable-function-entry=4 + KBUILD_RUSTFLAGS += $(call rustc-option,-Zpatchable-function-entry=4) else CC_FLAGS_FTRACE := -fpatchable-function-entry=2 + KBUILD_RUSTFLAGS += $(call rustc-option,-Zpatchable-function-entry=2) endif endif diff --git a/init/Kconfig b/init/Kconfig index 530a382ee0fe..43434b681c3f 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1946,7 +1946,7 @@ config RUST depends on !GCC_PLUGIN_RANDSTRUCT depends on !RANDSTRUCT depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE - depends on !CFI_CLANG || RUSTC_VERSION >= 107900 && HAVE_CFI_ICALL_NORMALIZE_INTEGERS + depends on !CFI_CLANG || RUSTC_VERSION >= 108100 && HAVE_CFI_ICALL_NORMALIZE_INTEGERS select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG depends on !CALL_PADDING || RUSTC_VERSION >= 108100 depends on !KASAN_SW_TAGS --- base-commit: 4a335f920bc78e51b1d7d216d11f2ecbb6dd949f change-id: 20241008-cfi-patchable-all-ddd6275eaf4f Best regards, -- Alice Ryhl