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From:   Arnd Bergmann <arnd@arndb.de>
To:     Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Kees Cook <keescook@chromium.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Marco Elver <elver@google.com>
Cc:     Arnd Bergmann <arnd@arndb.de>, Dmitry Vyukov <dvyukov@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@googlegroups.com, linux-kernel@vger.kernel.org,
        clang-built-linux@googlegroups.com
Subject: [PATCH] ubsan, kcsan: don't combine sanitizer with kcov
Date:   Tue,  5 May 2020 16:23:24 +0200
Message-Id: <20200505142341.1096942-1-arnd@arndb.de>
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Sender: linux-kernel-owner@vger.kernel.org
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Clang does not allow -fsanitize-coverage=trace-{pc,cmp} together
with -fsanitize=bounds or with ubsan:

clang: error: argument unused during compilation: '-fsanitize-coverage=trace-pc' [-Werror,-Wunused-command-line-argument]
clang: error: argument unused during compilation: '-fsanitize-coverage=trace-cmp' [-Werror,-Wunused-command-line-argument]

To avoid that case, add a Kconfig dependency. The dependency could
go either way, disabling CONFIG_KCOV or CONFIG_UBSAN_BOUNDS when the
other is set. I picked the second option here as this seems to have
a smaller impact on the resulting kernel.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 lib/Kconfig.kcsan | 2 +-
 lib/Kconfig.ubsan | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index ea28245c6c1d..8f856c8828d5 100644
--- 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
+	depends on HAVE_ARCH_KCSAN && DEBUG_KERNEL && !KASAN && !KCOV
 	select STACKTRACE
 	help
 	  The Kernel Concurrency Sanitizer (KCSAN) is a dynamic
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 929211039bac..f98ef029553e 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -29,6 +29,7 @@ config UBSAN_TRAP
 config UBSAN_BOUNDS
 	bool "Perform array index bounds checking"
 	default UBSAN
+	depends on !(CC_IS_CLANG && KCOV)
 	help
 	  This option enables detection of directly indexed out of bounds
 	  array accesses, where the array size is known at compile time.
-- 
2.26.0