From: Matthew Maurer <mmaurer@xxxxxxxxxx> Make it possible to use the Control Flow Integrity (CFI) sanitizer when Rust is enabled. Enabling CFI with Rust requires that CFI is configured to normalize integer types so that all integer types of the same size and signedness are compatible under CFI. Rust and C use the same LLVM backend for code generation, so Rust KCFI is compatible with the KCFI used in the kernel for C. In the case of FineIBT, CFI also depends on -Zpatchable-function-entry for rewriting the function prolouge, so we set that flag for Rust as well. The flag for FineIBT requires rustc 1.80.0 or later, so include a Kconfig requirement for that. Enabling Rust will select CFI_ICALL_NORMALIZE_INTEGERS because the flag is required to use Rust with CFI. Using select rather than `depends on` avoids the case where Rust is not visible in menuconfig due to CFI_ICALL_NORMALIZE_INTEGERS not being enabled. One disadvantage of select is that RUST must `depends on` all of the things that CFI_ICALL_NORMALIZE_INTEGERS depends on to avoid invalid configurations. Alice has been using KCFI on her phone for several months, so it is reasonably well tested on arm64. Signed-off-by: Matthew Maurer <mmaurer@xxxxxxxxxx> Co-developed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> --- This is an alternate version that shows how to resolve the conflict with the "rust: fix export of bss symbols" patch [1]. As for the conflict with the KASAN patchset [2], it should be resolved by adding both strings to the supported-sanitizers list in sorted order. [1]: https://lore.kernel.org/r/20240815074519.2684107-2-nmi@xxxxxxxxxxxx [2]: https://lore.kernel.org/r/20240812232910.2026387-1-mmaurer@xxxxxxxxxx Makefile | 7 +++++++ arch/x86/Makefile | 4 ++++ init/Kconfig | 4 +++- rust/Makefile | 2 +- scripts/generate_rust_target.rs | 1 + 5 files changed, 16 insertions(+), 2 deletions(-) diff --git a/Makefile b/Makefile index 484c6900337e..2dc39a23005d 100644 --- a/Makefile +++ b/Makefile @@ -955,6 +955,13 @@ CC_FLAGS_CFI := -fsanitize=kcfi ifdef CONFIG_CFI_ICALL_NORMALIZE_INTEGERS CC_FLAGS_CFI += -fsanitize-cfi-icall-experimental-normalize-integers endif +ifdef CONFIG_RUST + # Always pass -Zsanitizer-cfi-normalize-integers as CONFIG_RUST selects + # CONFIG_CFI_ICALL_NORMALIZE_INTEGERS. + RUSTC_FLAGS_CFI := -Zsanitizer=kcfi -Zsanitizer-cfi-normalize-integers + KBUILD_RUSTFLAGS += $(RUSTC_FLAGS_CFI) + export RUSTC_FLAGS_CFI +endif KBUILD_CFLAGS += $(CC_FLAGS_CFI) export CC_FLAGS_CFI endif diff --git a/arch/x86/Makefile b/arch/x86/Makefile index 801fd85c3ef6..e9b2ee3c8a71 100644 --- a/arch/x86/Makefile +++ b/arch/x86/Makefile @@ -237,6 +237,10 @@ ifdef CONFIG_CALL_PADDING PADDING_CFLAGS := -fpatchable-function-entry=$(CONFIG_FUNCTION_PADDING_BYTES),$(CONFIG_FUNCTION_PADDING_BYTES) KBUILD_CFLAGS += $(PADDING_CFLAGS) export PADDING_CFLAGS + +PADDING_RUSTFLAGS := -Zpatchable-function-entry=$(CONFIG_FUNCTION_PADDING_BYTES),$(CONFIG_FUNCTION_PADDING_BYTES) +KBUILD_RUSTFLAGS += $(PADDING_RUSTFLAGS) +export PADDING_RUSTFLAGS endif KBUILD_LDFLAGS += -m elf_$(UTS_MACHINE) diff --git a/init/Kconfig b/init/Kconfig index b0238c4b6e79..306af56a22df 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1905,11 +1905,13 @@ config RUST bool "Rust support" depends on HAVE_RUST depends on RUST_IS_AVAILABLE - depends on !CFI_CLANG depends on !MODVERSIONS depends on !GCC_PLUGINS depends on !RANDSTRUCT depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE + depends on !CFI_CLANG || RUSTC_VERSION >= 107900 && $(cc-option,-fsanitize=kcfi -fsanitize-cfi-icall-experimental-normalize-integers) + select CFI_ICALL_NORMALIZE_INTEGERS if CFI_CLANG + depends on !FINEIBT || RUSTC_VERSION >= 108000 help Enables Rust support in the kernel. diff --git a/rust/Makefile b/rust/Makefile index 26b16c036fe3..53a17d22f5cd 100644 --- a/rust/Makefile +++ b/rust/Makefile @@ -305,7 +305,7 @@ $(obj)/bindings/bindings_helpers_generated.rs: $(src)/helpers.c FORCE quiet_cmd_exports = EXPORTS $@ cmd_exports = \ $(NM) -p --defined-only $< \ - | awk '/ (T|R|D|B) / {printf "EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3}' > $@ + | awk '$$2~/(T|R|D|B)/ && $$3!~/__cfi/ {printf "EXPORT_SYMBOL_RUST_GPL(%s);\n",$$3}' > $@ $(obj)/exports_core_generated.h: $(obj)/core.o FORCE $(call if_changed,exports) diff --git a/scripts/generate_rust_target.rs b/scripts/generate_rust_target.rs index c31657380bf9..9b184099278a 100644 --- a/scripts/generate_rust_target.rs +++ b/scripts/generate_rust_target.rs @@ -192,6 +192,7 @@ fn main() { } ts.push("features", features); ts.push("llvm-target", "x86_64-linux-gnu"); + ts.push("supported-sanitizers", ["kcfi"]); ts.push("target-pointer-width", "64"); } else if cfg.has("X86_32") { // This only works on UML, as i386 otherwise needs regparm support in rustc -- 2.46.0.184.g6999bdac58-goog
