Hi Alice, Just some minor comments on this: On Mon, Jul 29, 2024 at 02:22:50PM +0000, Alice Ryhl wrote: > 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. Since this patch doesn't touch riscv, I think you can just talk about arm64 in the commit message. > 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 "Currently" will probably age badly -- can you talk about a compiler version instead (e.g. "prior to version nnn, the compiler thinks..."). > 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 These unwind entries aren't mentioned at all in the commit message. Please can you explain what you're doing here? I guess it's something to do with the PAC patching? Maybe this hunk would be better as a separate patch? Will
