On Mon, 8 Feb 2016 21:28:13 +0100
Michal Marek [off-list ref] wrote:

Dne 7.2.2016 v 22:28 Emese Revfy napsal(a):

quoted

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 but
currently only the x86 architecture enables plugins.

The directory of the gcc plugins is tools/gcc. 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
tools/gcc/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 changelog is missing an explanation as to why this needs to be part
of the kernel build system. To me it looks like building the kernel with
a modified build system and non-default compiler flags, which can be
achieved by doing make CC=my-gcc-wrapper or somesuch. But I'd love to be
corrected.

These compiler options compile the gcc plugins not the kernel. The new gcc option
used for building the kernel is the -fplugin option.

-- 
Emese