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authorMasahiro Yamada <yamada.masahiro@socionext.com>2018-05-28 12:22:04 +0300
committerMasahiro Yamada <yamada.masahiro@socionext.com>2018-06-11 03:14:08 +0300
commit5aadfdeb8de001ca04d500586e3b033404c28617 (patch)
treea430e73a414b972a4a4cb71ba98fad5af960254d /lib
parent6a61b70b43c9c4cbc7314bf6c8b5ba8b0d6e1e7b (diff)
downloadlinux-5aadfdeb8de001ca04d500586e3b033404c28617.tar.xz
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 <yamada.masahiro@socionext.com> Reviewed-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig.debug11
1 files changed, 7 insertions, 4 deletions
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