From: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Subject: kcov: allow more fine-grained coverage instrumentation
For more targeted fuzzing, it's better to disable kernel-wide
instrumentation and instead enable it on a per-subsystem basis. This
follows the pattern of UBSAN and allows you to compile in the kcov driver
without instrumenting the whole kernel.
To instrument a part of the kernel, you can use either
# for a single file in the current directory
KCOV_INSTRUMENT_filename.o := y
or
# for all the files in the current directory (excluding subdirectories)
KCOV_INSTRUMENT := y
or
# (same as above)
ccflags-y += $(CFLAGS_KCOV)
or
# for all the files in the current directory (including subdirectories)
subdir-ccflags-y += $(CFLAGS_KCOV)
Link: http://lkml.kernel.org/r/1464008380-11405-1-git-send-email-vegard.nossum@xxxxxxxxxx
Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Quentin Casasnovas <quentin.casasnovas@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
lib/Kconfig.debug | 11 +++++++++++
scripts/Makefile.lib | 2 +-
2 files changed, 12 insertions(+), 1 deletion(-)
diff -puN lib/Kconfig.debug~kcov-allow-more-fine-grained-coverage-instrumentation lib/Kconfig.debug
--- a/lib/Kconfig.debug~kcov-allow-more-fine-grained-coverage-instrumentation
+++ a/lib/Kconfig.debug
@@ -719,6 +719,17 @@ config KCOV
For more details, see Documentation/kcov.txt.
+config KCOV_INSTRUMENT_ALL
+ bool "Instrument all code by default"
+ depends on KCOV
+ default y if KCOV
+ help
+ If you are doing generic system call fuzzing (like e.g. syzkaller),
+ then you will want to instrument the whole kernel and you should
+ say y here. If you are doing more targeted fuzzing (like e.g.
+ filesystem fuzzing with AFL) then you will want to enable coverage
+ for more specific subsets of files, and should say n here.
+
config DEBUG_SHIRQ
bool "Debug shared IRQ handlers"
depends on DEBUG_KERNEL
diff -puN scripts/Makefile.lib~kcov-allow-more-fine-grained-coverage-instrumentation scripts/Makefile.lib
--- a/scripts/Makefile.lib~kcov-allow-more-fine-grained-coverage-instrumentation
+++ a/scripts/Makefile.lib
@@ -138,7 +138,7 @@ endif
ifeq ($(CONFIG_KCOV),y)
_c_flags += $(if $(patsubst n%,, \
- $(KCOV_INSTRUMENT_$(basetarget).o)$(KCOV_INSTRUMENT)y), \
+ $(KCOV_INSTRUMENT_$(basetarget).o)$(KCOV_INSTRUMENT)$(CONFIG_KCOV_INSTRUMENT_ALL)), \
$(CFLAGS_KCOV))
endif
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
