From 5aadfdeb8de001ca04d500586e3b033404c28617 Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Mon, 28 May 2018 18:22:04 +0900 Subject: kcov: test compiler capability in Kconfig and correct dependency As Documentation/kbuild/kconfig-language.txt notes, 'select' should be be used with care - it forces a lower limit of another symbol, ignoring the dependency. Currently, KCOV can select GCC_PLUGINS even if arch does not select HAVE_GCC_PLUGINS. This could cause the unmet direct dependency. Now that Kconfig can test compiler capability, let's handle this in a more sophisticated way. There are two ways to enable KCOV; use the compiler that natively supports -fsanitize-coverage=trace-pc, or build the SANCOV plugin if the compiler has ability to build GCC plugins. Hence, the correct dependency for KCOV is: depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS You do not need to build the SANCOV plugin if the compiler already supports -fsanitize-coverage=trace-pc. Hence, the select should be: select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC With this, GCC_PLUGIN_SANCOV is selected only when necessary, so scripts/Makefile.gcc-plugins can be cleaner. I also cleaned up Kconfig and scripts/Makefile.kcov as well. Signed-off-by: Masahiro Yamada Reviewed-by: Kees Cook --- lib/Kconfig.debug | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'lib/Kconfig.debug') diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index eb885942eb0f..d543c65ce0eb 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -736,12 +736,15 @@ config ARCH_HAS_KCOV only for x86_64. KCOV requires testing on other archs, and most likely disabling of instrumentation for some early boot code. +config CC_HAS_SANCOV_TRACE_PC + def_bool $(cc-option,-fsanitize-coverage=trace-pc) + config KCOV bool "Code coverage for fuzzing" depends on ARCH_HAS_KCOV + depends on CC_HAS_SANCOV_TRACE_PC || GCC_PLUGINS select DEBUG_FS - select GCC_PLUGINS if !COMPILE_TEST - select GCC_PLUGIN_SANCOV if !COMPILE_TEST + select GCC_PLUGIN_SANCOV if !CC_HAS_SANCOV_TRACE_PC help KCOV exposes kernel code coverage information in a form suitable for coverage-guided fuzzing (randomized testing). @@ -755,7 +758,7 @@ config KCOV config KCOV_ENABLE_COMPARISONS bool "Enable comparison operands collection by KCOV" depends on KCOV - default n + depends on $(cc-option,-fsanitize-coverage=trace-cmp) help KCOV also exposes operands of every comparison in the instrumented code along with operand sizes and PCs of the comparison instructions. @@ -765,7 +768,7 @@ config KCOV_ENABLE_COMPARISONS config KCOV_INSTRUMENT_ALL bool "Instrument all code by default" depends on KCOV - default y if KCOV + default y 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 -- cgit v1.2.3