To use the shadow call stack sanitizer, you must pass special flags: * On arm64, you must pass -ffixed-x18 to your compiler. * On riscv, you must pass --no-relax-gp to your linker. These requirements also apply to Rust code. When using Rust on arm64, you must pass the -Zfixed-x18 flag to rustc, which has the same effect as the -ffixed-x18 flag does for C code. The -Zfixed-x18 flag requires rustc version 1.80.0 or greater. There is no need to pass any flags to rustc on riscv as only the linker requires additional flags on this platform. On older versions of Rust, it is still possible to use shadow call stack by passing -Ctarget-feature=+reserve-x18 instead of -Zfixed-x18. However, this flag emits a warning during the build, so this patch does not add support for using it. Currently, the compiler thinks that the aarch64-unknown-none target doesn't support -Zsanitizer=shadow-call-stack, so the build will fail if you enable shadow call stack in non-dynamic mode. See [1] for the relevant feature request. To avoid this compilation failure, Kconfig is set up to reject such configurations. The `depends on` clause is placed on `config RUST` to avoid a situation where enabling Rust silently turns off the sanitizer. Instead, turning on the sanitizer results in Rust being disabled. We generally do not want changes to CONFIG_RUST to result in any mitigations being changed or turned off. Link: https://github.com/rust-lang/rust/issues/121972 [1] Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> --- Makefile | 1 + arch/arm64/Makefile | 3 +++ init/Kconfig | 2 +- 3 files changed, 5 insertions(+), 1 deletion(-) diff --git a/Makefile b/Makefile index 2b5f9f098b6f..66daca7a9b57 100644 --- a/Makefile +++ b/Makefile @@ -928,6 +928,7 @@ ifdef CONFIG_SHADOW_CALL_STACK ifndef CONFIG_DYNAMIC_SCS CC_FLAGS_SCS := -fsanitize=shadow-call-stack KBUILD_CFLAGS += $(CC_FLAGS_SCS) +KBUILD_RUSTFLAGS += -Zsanitizer=shadow-call-stack endif export CC_FLAGS_SCS endif diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile index f6bc3da1ef11..b058c4803efb 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -57,9 +57,11 @@ KBUILD_AFLAGS += $(call cc-option,-mabi=lp64) ifneq ($(CONFIG_UNWIND_TABLES),y) KBUILD_CFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables KBUILD_AFLAGS += -fno-asynchronous-unwind-tables -fno-unwind-tables +KBUILD_RUSTFLAGS += -Cforce-unwind-tables=n else KBUILD_CFLAGS += -fasynchronous-unwind-tables KBUILD_AFLAGS += -fasynchronous-unwind-tables +KBUILD_RUSTFLAGS += -Cforce-unwind-tables=y -Zuse-sync-unwind=n endif ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) @@ -114,6 +116,7 @@ endif ifeq ($(CONFIG_SHADOW_CALL_STACK), y) KBUILD_CFLAGS += -ffixed-x18 +KBUILD_RUSTFLAGS += -Zfixed-x18 endif ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) diff --git a/init/Kconfig b/init/Kconfig index 914edf51b068..103957466cee 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1909,7 +1909,7 @@ config RUST depends on !MODVERSIONS depends on !GCC_PLUGINS depends on !RANDSTRUCT - depends on !SHADOW_CALL_STACK + depends on !SHADOW_CALL_STACK || RUSTC_VERSION >= 108000 && UNWIND_PATCH_PAC_INTO_SCS depends on !DEBUG_INFO_BTF || PAHOLE_HAS_LANG_EXCLUDE help Enables Rust support in the kernel. -- 2.46.0.rc1.232.g9752f9e123-goog
