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

On Wed, Jun 03, 2026 at 07:43:29PM +0200, Yunseong Kim 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 <[email protected]>
> ---
>  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-$(CONFIG_KCOV_ENABLE_COMPARISONS)	+= -fsanitize-coverage=trace-cmp
>  
> +# KCOV dataflow: trace function args and return values
> +kcov-dataflow-flags-y := -fsanitize-coverage=dataflow-args,dataflow-ret -g
> +kcov-dataflow-flags-$(CONFIG_KCOV_DATAFLOW_NO_INLINE) += -fno-inline

https://clang.llvm.org/docs/ClangCommandLineReference.html

Has no mention of -fno-inline, furthermore, what are the exact
semantics? Does it inhibit __always_inline?