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From: Marco Elver <elver@google.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	Andrey Ryabinin <aryabinin@virtuozzo.com>,
	Kees Cook <keescook@chromium.org>,
	Andrey Konovalov <andreyknvl@google.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Stephen Rothwell <sfr@canb.auug.org.au>,
	Thomas Gleixner <tglx@linutronix.de>,
	kasan-dev <kasan-dev@googlegroups.com>,
	LKML <linux-kernel@vger.kernel.org>,
	clang-built-linux <clang-built-linux@googlegroups.com>
Subject: Re: [PATCH] ubsan, kcsan: don't combine sanitizer with kcov
Date: Tue, 5 May 2020 19:07:22 +0200	[thread overview]
Message-ID: <CANpmjNPCZ2r9V7t50_yy+F_-roBWJdiQWgmvvcqTFxzdzOwKhg@mail.gmail.com> (raw)
In-Reply-To: <CAK8P3a36w+QFqik_sHS3T5+_DZ7XP9Y5BYqT72pnjC67T9Sn3Q@mail.gmail.com>

On Tue, 5 May 2020 at 17:29, Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Tue, May 5, 2020 at 5:20 PM 'Marco Elver' via Clang Built Linux
> <clang-built-linux@googlegroups.com> wrote:
>
> > > --- a/lib/Kconfig.kcsan
> > > +++ b/lib/Kconfig.kcsan
> > > @@ -5,7 +5,7 @@ config HAVE_ARCH_KCSAN
> > >
> > >  menuconfig KCSAN
> > >         bool "KCSAN: dynamic data race detector"
> > > -       depends on HAVE_ARCH_KCSAN && DEBUG_KERNEL && !KASAN && !KCOV
> > > +       depends on HAVE_ARCH_KCSAN && DEBUG_KERNEL && !KASAN && !(KCOV
> > > && CC_IS_CLANG)
> >
> > I wonder if we can just add this:  depends on !(KCOV &&
> > !$(cc-option,-Werror -fsanitize=thread -fsanitize-coverage=trace-pc))
> >
> > Similarly for UBSAN.
> >
> > That way, once Clang supports this combination, we don't need another
> > patch to fix it.
>
> Good idea. It probably get a little more complicated because kcov uses
> different flags depending on other options:
>
> kcov-flags-$(CONFIG_CC_HAS_SANCOV_TRACE_PC)     += -fsanitize-coverage=trace-pc
> kcov-flags-$(CONFIG_KCOV_ENABLE_COMPARISONS)    += -fsanitize-coverage=trace-cmp
> kcov-flags-$(CONFIG_GCC_PLUGIN_SANCOV)          +=
> -fplugin=$(objtree)/scripts/gcc-plugins/sancov_plugin.so
>
> Do you have any preference on whether we should make KCSAN or KCOV
> conditional in this case? It may be easier to move the compiletime check
> into CONFIG_KCOV_ENABLE_COMPARISONS and
> CONFIG_CC_HAS_SANCOV_TRACE_PC.

Whichever is easier. I think if we have a config that tries to set
both, but then one gets silently disabled, it likely already breaks
the usecase. It'd be nice if there was a way to warn about only one
being selected so that a developer can then go back and choose the one
they're most interested in (or change compiler).

Thanks,
-- Marco

  reply	other threads:[~2020-05-05 17:07 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-05 14:23 [PATCH] ubsan, kcsan: don't combine sanitizer with kcov Arnd Bergmann
2020-05-05 14:36 ` Marco Elver
2020-05-05 14:50   ` Dmitry Vyukov
2020-05-05 14:59     ` Arnd Bergmann
2020-05-05 15:19       ` Marco Elver
2020-05-05 15:28         ` Arnd Bergmann
2020-05-05 17:07           ` Marco Elver [this message]
2020-05-07 16:25             ` [PATCH] [v2] ubsan, kcsan: don't combine sanitizer with kcov on clang Arnd Bergmann
2020-05-07 16:50               ` Marco Elver
2020-05-13 20:02               ` Paul E. McKenney
2020-05-22 16:08 ` [tip: locking/kcsan] ubsan, kcsan: Don't " tip-bot2 for Arnd Bergmann

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