Re: [PATCH 2/2] kbuild: rust: Enable KASAN support

[Andrey Konovalov]

On Fri, Jul 26, 2024 at 1:21 AM Matthew Maurer <mmaurer@xxxxxxxxxx> wrote:
>
> Rust supports KASAN via LLVM, but prior to this patch, the flags aren't
> set properly.
>
> Suggested-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
> Signed-off-by: Matthew Maurer <mmaurer@xxxxxxxxxx>

Hi Matthew,

>  CFLAGS_KASAN_MINIMAL := -fsanitize=kernel-address
> +RUSTFLAGS_KASAN_MINIMAL := -Zsanitizer=kernel-address -Zsanitizer-recover=kernel-address

If I recall correctly, the reason we need CFLAGS_KASAN_MINIMAL is
because older compilers don't support some of the additional options.
With Rust, this shouldn't be needed, as it requires a modern compiler
that does support all needed options. E.g., for CONFIG_KASAN_SW_TAGS,
we also don't have the MINIMAL thing for the same reason. (Possibly,
we also already don't need this for GENERIC KASAN, as the GCC version
requirement was raised a few times since KASAN was introduced.)

>         # Now add all the compiler specific options that are valid standalone
>         CFLAGS_KASAN := $(CFLAGS_KASAN_SHADOW) \
>          $(call cc-param,asan-globals=1) \
>          $(call cc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
>          $(call cc-param,asan-instrument-allocas=1)
> +       ifdef CONFIG_RUST
> +               RUSTFLAGS_KASAN := $(RUSTFLAGS_KASAN_SHADOW) \
> +                $(call rustc-param,asan-globals=1) \
> +                $(call rustc-param,asan-instrumentation-with-call-threshold=$(call_threshold)) \
> +                $(call rustc-param,asan-instrument-allocas=1)

I'm wondering if there's a way to avoid duplicating all options for
Rust. Perhaps, some kind of macro?

Thanks!