Add flags to support the shadow call stack sanitizer, both in the dynamic and non-dynamic modes. Right now, the compiler will emit the warning "unknown feature specified for `-Ctarget-feature`: `reserve-x18`". However, the compiler still passes it to the codegen backend, so the flag will work just fine. Once rustc starts recognizing the flag (or provides another way to enable the feature), it will stop emitting this warning. See [1] for the relevant issue. 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. However, I still think it is reasonable to add the flag now, as it will at least fail the build when using an invalid configuration, until the Rust compiler is fixed to list -Zsanitizer=shadow-call-stack as supported for the target. See [2] for the feature request to add this. I have tested this change with Rust Binder on an Android device using CONFIG_DYNAMIC_SCS. Without the -Ctarget-feature=+reserve-x18 flag, the phone crashes immediately on boot, and with the flag, the phone appears to work normally. This contains a TODO to add the -Zuse-sync-unwind=n flag. The flag defaults to n, so it isn't a problem today, but the flag is unstable, so the default could change in a future compiler release. Link: https://github.com/rust-lang/rust/issues/121970 [1] Link: https://github.com/rust-lang/rust/issues/121972 [2] Signed-off-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> --- This patch raises the question of whether we should change the Rust aarch64 support to use a custom target.json specification. If we do that, then we can fix both the warning for dynamic SCS and the build-failure for non-dynamic SCS without waiting for a new version of rustc with the mentioned issues fixed. --- Changes in v2: - Add -Cforce-unwind-tables flag. - Link to v1: https://lore.kernel.org/r/20240304-shadow-call-stack-v1-1-f055eaf40a2c@xxxxxxxxxx --- Makefile | 1 + arch/arm64/Makefile | 4 ++++ 2 files changed, 5 insertions(+) diff --git a/Makefile b/Makefile index 0e36eff14608..345066643a76 100644 --- a/Makefile +++ b/Makefile @@ -936,6 +936,7 @@ 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 a88cdf910687..9bd5522c18e9 100644 --- a/arch/arm64/Makefile +++ b/arch/arm64/Makefile @@ -48,9 +48,12 @@ 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 +# TODO: Pass -Zuse-sync-unwind=n once we upgrade to Rust 1.77.0 +KBUILD_RUSTFLAGS += -Cforce-unwind-tables=y endif ifeq ($(CONFIG_STACKPROTECTOR_PER_TASK),y) @@ -103,6 +106,7 @@ endif ifeq ($(CONFIG_SHADOW_CALL_STACK), y) KBUILD_CFLAGS += -ffixed-x18 +KBUILD_RUSTFLAGS += -Ctarget-feature=+reserve-x18 endif ifeq ($(CONFIG_CPU_BIG_ENDIAN), y) --- base-commit: 90d35da658da8cff0d4ecbb5113f5fac9d00eb72 change-id: 20240304-shadow-call-stack-9c197a4361d9 Best regards, -- Alice Ryhl <aliceryhl@xxxxxxxxxx>
