Re: [PATCH v3 3/3] integer-wrap: Force full rebuild when .scl file changes

Justin Stitt
2025-05-05T18:17:12Z

On Sat, May 3, 2025 at 11:46 AM Kees Cook <kees@kernel.org> wrote:
>
> Since the integer wrapping sanitizer's behavior depends on its associated
> .scl file, we must force a full rebuild if the file changes. If not,
> instrumentation may differ between targets based on when they were built.
>
> Generate a new header file, integer-wrap.h, any time the Clang .scl
> file changes. Include the header file in compiler-version.h when its
> associated feature name, INTEGER_WRAP, is defined. This will be picked
> up by fixdep and force rebuilds where needed.
>
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> Cc: Masahiro Yamada <masahiroy@kernel.org>
> Cc: Justin Stitt <justinstitt@google.com>
> Cc: Nathan Chancellor <nathan@kernel.org>
> Cc: Nicolas Schier <nicolas.schier@linux.dev>
> Cc: Marco Elver <elver@google.com>
> Cc: Andrey Konovalov <andreyknvl@gmail.com>
> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
> Cc: <linux-kbuild@vger.kernel.org>
> Cc: <kasan-dev@googlegroups.com>
> Cc: <linux-hardening@vger.kernel.org>
> ---
> include/linux/compiler-version.h | 3 +++
> scripts/Makefile.ubsan | 1 +
> scripts/basic/Makefile | 5 +++++
> 3 files changed, 9 insertions(+)
>
> diff --git a/include/linux/compiler-version.h b/include/linux/compiler-version.h
> index 69b29b400ce2..187e749f9e79 100644
> --- a/include/linux/compiler-version.h
> +++ b/include/linux/compiler-version.h
> @@ -19,3 +19,6 @@
> #ifdef RANDSTRUCT
> #include <generated/randstruct_hash.h>
> #endif
> +#ifdef INTEGER_WRAP
> +#include <generated/integer-wrap.h>
> +#endif
> diff --git a/scripts/Makefile.ubsan b/scripts/Makefile.ubsan
> index 9e35198edbf0..653f7117819c 100644
> --- a/scripts/Makefile.ubsan
> +++ b/scripts/Makefile.ubsan
> @@ -15,6 +15,7 @@ ubsan-cflags-$(CONFIG_UBSAN_TRAP) += $(call cc-option,-fsanitize-trap=undefined
> export CFLAGS_UBSAN := $(ubsan-cflags-y)
>
> ubsan-integer-wrap-cflags-$(CONFIG_UBSAN_INTEGER_WRAP) += \
> + -DINTEGER_WRAP \
> -fsanitize-undefined-ignore-overflow-pattern=all \
> -fsanitize=signed-integer-overflow \
> -fsanitize=unsigned-integer-overflow \
> diff --git a/scripts/basic/Makefile b/scripts/basic/Makefile
> index dd289a6725ac..fb8e2c38fbc7 100644
> --- a/scripts/basic/Makefile
> +++ b/scripts/basic/Makefile
> @@ -14,3 +14,8 @@ cmd_create_randstruct_seed = \
> $(obj)/randstruct.seed: $(gen-randstruct-seed) FORCE
> $(call if_changed,create_randstruct_seed)
> always-$(CONFIG_RANDSTRUCT) += randstruct.seed
> +
> +# integer-wrap: if the .scl file changes, we need to do a full rebuild.
> +$(obj)/../../include/generated/integer-wrap.h: $(srctree)/scripts/integer-wrap-ignore.scl FORCE
> + $(call if_changed,touch)
> +always-$(CONFIG_UBSAN_INTEGER_WRAP) += ../../include/generated/integer-wrap.h

I'm not sure how this fake header stuff works to ensure builds deps
are tracked properly but we do need scl files to be considered as part
of complete builds, so:

Acked-by: Justin Stitt <justinstitt@google.com>

> --
> 2.34.1
>