kcov: test compiler capability in Kconfig and correct dependency
authorMasahiro Yamada <yamada.masahiro@socionext.com>
Mon, 28 May 2018 09:22:04 +0000 (18:22 +0900)
committerMasahiro Yamada <yamada.masahiro@socionext.com>
Mon, 11 Jun 2018 00:14:08 +0000 (09:14 +0900)
commit5aadfdeb8de001ca04d500586e3b033404c28617
treea430e73a414b972a4a4cb71ba98fad5af960254d
parent6a61b70b43c9c4cbc7314bf6c8b5ba8b0d6e1e7b
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>
Makefile
lib/Kconfig.debug
scripts/Makefile.gcc-plugins
scripts/Makefile.kcov
scripts/gcc-plugins/Makefile