2 files changed, 33 insertions, 0 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5a60f45cd9bb..532d4d52d1df 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -696,6 +696,27 @@ source "lib/Kconfig.kasan"
 
 endmenu # "Memory Debugging"
 
+config ARCH_HAS_KCOV
+	bool
+	help
+	  KCOV does not have any arch-specific code, but currently it is enabled
+	  only for x86_64. KCOV requires testing on other archs, and most likely
+	  disabling of instrumentation for some early boot code.
+
+config KCOV
+	bool "Code coverage for fuzzing"
+	depends on ARCH_HAS_KCOV
+	select DEBUG_FS
+	help
+	  KCOV exposes kernel code coverage information in a form suitable
+	  for coverage-guided fuzzing (randomized testing).
+
+	  If RANDOMIZE_BASE is enabled, PC values will not be stable across
+	  different machines and across reboots. If you need stable PC values,
+	  disable RANDOMIZE_BASE.
+
+	  For more details, see Documentation/kcov.txt.
+
 config DEBUG_SHIRQ
 	bool "Debug shared IRQ handlers"
 	depends on DEBUG_KERNEL
diff --git a/lib/Makefile b/lib/Makefile
index 4962d14c450f..a1de5b61ff40 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -7,6 +7,18 @@ ORIG_CFLAGS := $(KBUILD_CFLAGS)
 KBUILD_CFLAGS = $(subst $(CC_FLAGS_FTRACE),,$(ORIG_CFLAGS))
 endif
 
+# These files are disabled because they produce lots of non-interesting and/or
+# flaky coverage that is not a function of syscall inputs. For example,
+# rbtree can be global and individual rotations don't correlate with inputs.
+KCOV_INSTRUMENT_string.o := n
+KCOV_INSTRUMENT_rbtree.o := n
+KCOV_INSTRUMENT_list_debug.o := n
+KCOV_INSTRUMENT_debugobjects.o := n
+KCOV_INSTRUMENT_dynamic_debug.o := n
+# Kernel does not boot if we instrument this file as it uses custom calling
+# convention (see CONFIG_ARCH_HWEIGHT_CFLAGS).
+KCOV_INSTRUMENT_hweight.o := n
+
 lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 rbtree.o radix-tree.o dump_stack.o timerqueue.o\
 	 idr.o int_sqrt.o extable.o \