[PATCH -tip 01/10] ubsan, kcsan: don't combine sanitizer with kcov on clang

[Marco Elver]

From: Arnd Bergmann <arnd@xxxxxxxx>

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 the warning, check whether clang can handle this correctly
or disallow ubsan and kcsan when kcov is enabled.

Link: https://bugs.llvm.org/show_bug.cgi?id=45831
Link: https://lore.kernel.org/lkml/20200505142341.1096942-1-arnd@xxxxxxxx
Acked-by: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
---
This patch is already in -rcu tree, but since since the series is based
on -tip, to avoid conflict it is required for the subsequent patches.
---
 lib/Kconfig.kcsan | 11 +++++++++++
 lib/Kconfig.ubsan | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
index ea28245c6c1d..a7276035ca0d 100644
--- a/lib/Kconfig.kcsan
+++ b/lib/Kconfig.kcsan
@@ -3,9 +3,20 @@
 config HAVE_ARCH_KCSAN
 	bool
 
+config KCSAN_KCOV_BROKEN
+	def_bool KCOV && CC_HAS_SANCOV_TRACE_PC
+	depends on CC_IS_CLANG
+	depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=thread -fsanitize-coverage=trace-pc)
+	help
+	  Some versions of clang support either KCSAN and KCOV but not the
+	  combination of the two.
+	  See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
+	  in newer releases.
+
 menuconfig KCSAN
 	bool "KCSAN: dynamic data race detector"
 	depends on HAVE_ARCH_KCSAN && DEBUG_KERNEL && !KASAN
+	depends on !KCSAN_KCOV_BROKEN
 	select STACKTRACE
 	help
 	  The Kernel Concurrency Sanitizer (KCSAN) is a dynamic
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 48469c95d78e..3baea77bf37f 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -26,9 +26,20 @@ config UBSAN_TRAP
 	  the system. For some system builders this is an acceptable
 	  trade-off.
 
+config UBSAN_KCOV_BROKEN
+	def_bool KCOV && CC_HAS_SANCOV_TRACE_PC
+	depends on CC_IS_CLANG
+	depends on !$(cc-option,-Werror=unused-command-line-argument -fsanitize=bounds -fsanitize-coverage=trace-pc)
+	help
+	  Some versions of clang support either UBSAN or KCOV but not the
+	  combination of the two.
+	  See https://bugs.llvm.org/show_bug.cgi?id=45831 for the status
+	  in newer releases.
+
 config UBSAN_BOUNDS
 	bool "Perform array index bounds checking"
 	default UBSAN
+	depends on !UBSAN_KCOV_BROKEN
 	help
 	  This option enables detection of directly indexed out of bounds
 	  array accesses, where the array size is known at compile time.
-- 
2.26.2.761.g0e0b3e54be-goog