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Date: Tue, 1 Mar 2016 11:09:15 -0800
From: Kees Cook <keescook@...omium.org>
To: Emese Revfy <re.emese@...il.com>
Cc: linux-kbuild <linux-kbuild@...r.kernel.org>, PaX Team <pageexec@...email.hu>,
Brad Spengler <spender@...ecurity.net>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Michal Marek <mmarek@...e.com>,
Rasmus Villemoes <linux@...musvillemoes.dk>, Fengguang Wu <fengguang.wu@...el.com>
Subject: Re: [PATCH v4 0/3] Introduce GCC plugin infrastructure
On Tue, Mar 1, 2016 at 9:14 AM, Emese Revfy <re.emese@...il.com> wrote:
> This patch set introduce the GCC plugin infrastructure with examples for testing
> and documentation.
>
> GCC plugins are loadable modules that provide extra features to the compiler.
> They are useful for runtime instrumentation and static analysis.
>
> The infrastructure supports all gcc versions from 4.5 to 6.0, building
> out-of-tree modules and building in a separate directory. Cross-compilation
> is supported too but currently only the x86 architecture enables plugins.
>
> This infrastructure was ported from grsecurity/PaX. It is a CII project
> supported by the Linux Foundation.
>
> Emese Revfy (3):
> GCC plugin infrastructure
> Add Cyclomatic complexity plugin
> Documentations of the GCC plugin infrastructre
>
>
> Changes from v3:
> * Fix some indentation related warnings
> (Suggested by checkpatch.pl)
> * Add maintainer entries
> * Don't run gcc_plugin.sh when the GCC_PLUGINS option is disabled or unsupported
> (Reported-by: Fengguang Wu <fengguang.wu@...el.com>)
>
> I found a kbuild bug (or feature?) related to this patch. When a config option is disabled
> then the symbol gets undefined only when you run make clean.
> The easiest way to reproduce it is with e.g., CC_STACKPROTECTOR_STRONG:
Yeah, I fought this when adding _STRONG. It seems there are two
"phases" of Kbuild where it rebuilds the .config during phase 1 then
does the actual build in phase 2. I couldn't make the stack protector
detection kill the build because it would kill the config rewriter
too. So I had to leave it a warning and let the compiler die later
instead.
-Kees
>
> * patch in warning here:
>
> diff --git a/Makefile b/Makefile
> index a1a7708..9e6961f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -664,6 +664,7 @@ ifdef CONFIG_CC_STACKPROTECTOR_REGULAR
> else
> ifdef CONFIG_CC_STACKPROTECTOR_STRONG
> stackp-flag := -fstack-protector-strong
> + $(warning AAAAAAAA)
> ifeq ($(call cc-option, $(stackp-flag)),)
> $(warning Cannot use CONFIG_CC_STACKPROTECTOR_STRONG: \
> -fstack-protector-strong not supported by compiler)
>
> * enable CC_STACKPROTECTOR_STRONG in menuconfig
> * run make and it prints out the "AAAAAAAA"
> * enable CC_STACKPROTECTOR_NONE in menuconfig
> * run make and it prints out the "AAAAAAAA"
> * run make clean, run make again and it doesn't print out the "AAAAAAAA"
>
>
> Changes from v2:
> * Fixed incorrectly encoded characters
> * Generate the GIMPLE, IPA, SIMPLE_IPA and RTL pass structures
> (Suggested-by: Rasmus Villemoes <linux@...musvillemoes.dk>)
> * Write plugin related warning messages to stderr instead of stdout
> (Suggested-by: Kees Cook <keescook@...omium.org>)
> * Mention the installation of the gcc plugin headers (Documentation)
>
>
> Changes from v1:
> * Move the gcc-plugins make target into a separate Makefile because there may
> be a lot of plugins (Suggested-by: Rasmus Villemoes)
> * Simplify the dependencies of the plugin related config option
> (Suggested-by: Kees Cook <keescook@...omium.org>)
> * Removed the unnecessary example plugin
> ---
> Documentation/dontdiff | 1 +
> Documentation/gcc-plugins.txt | 82 ++++
> MAINTAINERS | 8 +
> Makefile | 41 +-
> arch/Kconfig | 24 +
> arch/x86/Kconfig | 1 +
> init/Makefile | 3 +
> scripts/Makefile.build | 2 +-
> scripts/Makefile.clean | 3 +-
> scripts/Makefile.gcc-plugins | 32 ++
> scripts/Makefile.host | 69 ++-
> scripts/gcc-plugin.sh | 51 ++
> scripts/link-vmlinux.sh | 2 +-
> scripts/package/builddeb | 1 +
> tools/gcc/Makefile | 19 +
> tools/gcc/cyc_complexity_plugin.c | 73 +++
> tools/gcc/gcc-common.h | 803 +++++++++++++++++++++++++++++++
> tools/gcc/gcc-generate-gimple-pass.h | 173 +++++++
> tools/gcc/gcc-generate-ipa-pass.h | 287 +++++++++++
> tools/gcc/gcc-generate-rtl-pass.h | 173 +++++++
> tools/gcc/gcc-generate-simple_ipa-pass.h | 173 +++++++
> 21 files changed, 2006 insertions(+), 15 deletions(-)
--
Kees Cook
Chrome OS & Brillo Security
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