Re: [RFC PATCH v2 2/6] kcov: add build system support for dataflow instrumentation

[Alexander Potapenko]

On Wed, Jun 3, 2026 at 7:43 PM Yunseong Kim <yunseong.kim@xxxxxxxx> wrote:
>
> Add CFLAGS_KCOV_DATAFLOW and RUSTFLAGS_KCOV_DATAFLOW exports to
> scripts/Makefile.kcov, containing:
>   -fsanitize-coverage=dataflow-args,dataflow-ret -g
>   (with optional -fno-inline via CONFIG_KCOV_DATAFLOW_NO_INLINE)
>
> scripts/Makefile.lib applies these flags when a module's Makefile sets:
>   KCOV_DATAFLOW_file.o := y   (per-file)
>   KCOV_DATAFLOW := y          (per-directory)
>
> Also supports CONFIG_KCOV_DATAFLOW_INSTRUMENT_ALL for global enablement.
> The flags are only applied to kernel objects (same guard as basic KCOV).
>
> Signed-off-by: Yunseong Kim <yunseong.kim@xxxxxxxx>
> ---
>  scripts/Makefile.kcov | 6 ++++++
>  scripts/Makefile.lib  | 7 +++++++
>  2 files changed, 13 insertions(+)
>
> diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov
> index 78305a84ba9d..101173fe194b 100644
> --- a/scripts/Makefile.kcov
> +++ b/scripts/Makefile.kcov
> @@ -2,10 +2,16 @@
>  kcov-flags-y                                   += -fsanitize-coverage=trace-pc
>  kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS)   += -fsanitize-coverage=trace-cmp
>
> +# KCOV dataflow: trace function args and return values
> +kcov-dataflow-flags-y := -fsanitize-coverage=dataflow-args,dataflow-ret -g

Instead of adding debug info here, consider adding a dependency on
CONFIG_DEBUG_INFO.


>  export CFLAGS_KCOV := $(kcov-flags-y)
> +export CFLAGS_KCOV_DATAFLOW := $(kcov-dataflow-flags-y)
> +export RUSTFLAGS_KCOV_DATAFLOW := -Cpasses=sancov-module -Cllvm-args=-sanitizer-coverage-level=3 -Cllvm-args=-sanitizer-coverage-dataflow-args -Cllvm-args=-sanitizer-coverage-dataflow-ret -Cdebuginfo=2

Ditto.