Re: [kernel-hardening] [PATCH v8 2/4] GCC plugin infrastructure

On 13/05/16 09:57, Emese Revfy wrote:

This patch allows to build the whole kernel with GCC plugins. It was ported from
grsecurity/PaX. The infrastructure supports building out-of-tree modules and
building in a separate directory. Cross-compilation is supported too.
Currently the x86, arm, arm64 and uml architectures enable plugins.

The directory of the gcc plugins is scripts/gcc-plugins. You can use a file or a directory
there. The plugins compile with these options:
  * -fno-rtti: gcc is compiled with this option so the plugins must use it too
  * -fno-exceptions: this is inherited from gcc too
  * -fasynchronous-unwind-tables: this is inherited from gcc too
  * -ggdb: it is useful for debugging a plugin (better backtrace on internal
     errors)
  * -Wno-narrowing: to suppress warnings from gcc headers (ipa-utils.h)
  * -Wno-unused-variable: to suppress warnings from gcc headers (gcc_version
     variable, plugin-version.h)

The infrastructure introduces a new Makefile target called gcc-plugins. It
supports all gcc versions from 4.5 to 6.0. The scripts/gcc-plugin.sh script
chooses the proper host compiler (gcc-4.7 can be built by either gcc or g++).
This script also checks the availability of the included headers in
scripts/gcc-plugins/gcc-common.h.

The gcc-common.h header contains frequently included headers for GCC plugins
and it has a compatibility layer for the supported gcc versions.

The gcc-generate-*-pass.h headers automatically generate the registration
structures for GIMPLE, SIMPLE_IPA, IPA and RTL passes.

Note that 'make clean' keeps the *.so files (only the distclean or mrproper
targets clean all) because they are needed for out-of-tree modules.

The arm and arm64 architectures were tested by David Brown [off-list ref].

Signed-off-by: Emese Revfy <redacted>

I've done some basic sanity testing on powerpc with the cyclomatic 
complexity plugin (with LE native + cross-compilers) and it seems to 
work with the patch below.

Signed-off-by: Andrew Donnellan <redacted>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index a18a0dc..0cfed5b 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -97,6 +97,7 @@ config PPC
         select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL
         select HAVE_FUNCTION_TRACER
         select HAVE_FUNCTION_GRAPH_TRACER
+       select HAVE_GCC_PLUGINS
         select SYSCTL_EXCEPTION_TRACE
         select ARCH_WANT_OPTIONAL_GPIOLIB
         select VIRT_TO_BUS if !PPC64

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan@au1.ibm.com  IBM Australia Limited