From 3283a3b899f3d54c89a700249d177ede43fae2d5 Mon Sep 17 00:00:00 2001
From: Victor Chibotaru <tchibo@google.com>
Date: Fri, 17 Nov 2017 15:30:50 -0800
Subject: [PATCH] BACKPORT: Makefile: support flag
 -fsanitizer-coverage=trace-cmp

(Upstream commit d677a4d6019385488e794cc47bd3d6f9c2aab874.)

The flag enables Clang instrumentation of comparison operations
(currently not supported by GCC).  This instrumentation is needed by the
new KCOV device to collect comparison operands.

Link: http://lkml.kernel.org/r/20171011095459.70721-2-glider@google.com
Signed-off-by: Victor Chibotaru <tchibo@google.com>
Signed-off-by: Alexander Potapenko <glider@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Popov <alex.popov@linux.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: <syzkaller@googlegroups.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Change-Id: Id294d9cc7619fb351a8929d11d45e532f86d2c36
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Bug: 147413187
---
 Makefile              |  4 ++--
 lib/Kconfig.debug     | 10 ++++++++++
 scripts/Makefile.kcov |  7 +++++++
 3 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 scripts/Makefile.kcov

diff --git a/Makefile b/Makefile
index a4ec8f733611..e121b0021c92 100644
--- a/Makefile
+++ b/Makefile
@@ -650,8 +650,7 @@ KBUILD_AFLAGS	+= $(call cc-option,-fno-PIE)
 CFLAGS_GCOV	:= -fprofile-arcs -ftest-coverage \
 	$(call cc-option,-fno-tree-loop-im) \
 	$(call cc-disable-warning,maybe-uninitialized,)
-CFLAGS_KCOV	:= $(call cc-option,-fsanitize-coverage=trace-pc,)
-export CFLAGS_GCOV CFLAGS_KCOV
+export CFLAGS_GCOV
 
 # Make toolchain changes before including arch/$(SRCARCH)/Makefile to ensure
 # ar/cc/ld-* macros return correct values.
@@ -706,6 +705,7 @@ ifeq ($(shell $(CONFIG_SHELL) $(srctree)/scripts/gcc-goto.sh $(CC) $(KBUILD_CFLA
 	KBUILD_AFLAGS += -DCC_HAVE_ASM_GOTO
 endif
 
+include scripts/Makefile.kcov
 include scripts/Makefile.gcc-plugins
 
 ifdef CONFIG_READABLE_ASM
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 81a10bd78d8d..5bc743f4d402 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -756,6 +756,16 @@ config KCOV
 
 	  For more details, see Documentation/dev-tools/kcov.rst.
 
+config KCOV_ENABLE_COMPARISONS
+	bool "Enable comparison operands collection by KCOV"
+	depends on KCOV
+	default n
+	help
+	  KCOV also exposes operands of every comparison in the instrumented
+	  code along with operand sizes and PCs of the comparison instructions.
+	  These operands can be used by fuzzing engines to improve the quality
+	  of fuzzing coverage.
+
 config KCOV_INSTRUMENT_ALL
 	bool "Instrument all code by default"
 	depends on KCOV
diff --git a/scripts/Makefile.kcov b/scripts/Makefile.kcov
new file mode 100644
index 000000000000..5cc72037e423
--- /dev/null
+++ b/scripts/Makefile.kcov
@@ -0,0 +1,7 @@
+ifdef CONFIG_KCOV
+CFLAGS_KCOV	:= $(call cc-option,-fsanitize-coverage=trace-pc,)
+ifeq ($(CONFIG_KCOV_ENABLE_COMPARISONS),y)
+CFLAGS_KCOV += $(call cc-option,-fsanitize-coverage=trace-cmp,)
+endif
+
+endif