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Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.99.2 #2 (Red Hat Linux)) id 1wV3hZ-0000000E5QO-0fPF; Thu, 04 Jun 2026 08:45:21 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 49529301218; Thu, 04 Jun 2026 10:45:19 +0200 (CEST) Date: Thu, 4 Jun 2026 10:45:19 +0200 From: Peter Zijlstra To: Yunseong Kim Cc: Ingo Molnar , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Dmitry Vyukov , Andrey Konovalov , Andrew Morton , Nathan Chancellor , Nick Desaulniers , Bill Wendling , Justin Stitt , Nicolas Schier , Miguel Ojeda , Boqun Feng , Gary Guo , =?iso-8859-1?Q?Bj=F6rn?= Roy Baron , Benno Lossin , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Jonathan Corbet , Shuah Khan , linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, llvm@lists.linux.dev, linux-kbuild@vger.kernel.org, rust-for-linux@vger.kernel.org, workflows@vger.kernel.org, linux-doc@vger.kernel.org, Yunseong Kim Subject: Re: [RFC PATCH v2 2/6] kcov: add build system support for dataflow instrumentation Message-ID: <20260604084519.GA3126523@noisy.programming.kicks-ass.net> References: <20260603-kcov-dataflow-next-20260603-v2-0-fee0939de2c4@est.tech> <20260603-kcov-dataflow-next-20260603-v2-2-fee0939de2c4@est.tech> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260603-kcov-dataflow-next-20260603-v2-2-fee0939de2c4@est.tech> 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 > --- > 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?