linux-kernel - Re: [kernel-hardening] [PATCH v5 1/4] gcc-plugins: Add the initify gcc plugin

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Date:   Mon, 27 Mar 2017 09:14:36 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Andrew Donnellan <andrew.donnellan@....ibm.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Emese Revfy <re.emese@...il.com>,
        Arnd Bergmann <arnd@...db.de>,
        Josh Triplett <josh@...htriplett.org>,
        PaX Team <pageexec@...email.hu>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        minipli@...linux.so, Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        David Brown <david.brown@...aro.org>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jeff Layton <jlayton@...chiereds.net>,
        Sam Ravnborg <sam@...nborg.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>
Subject: Re: [kernel-hardening] [PATCH v5 1/4] gcc-plugins: Add the initify
 gcc plugin

On Mon, Mar 27, 2017 at 12:38 AM, Andrew Donnellan
<andrew.donnellan@....ibm.com> wrote:
> On 01/02/17 07:24, Kees Cook wrote:
>>
>> From: Emese Revfy <re.emese@...il.com>
>>
>> The kernel already has a mechanism to free up code and data memory that
>> is only used during kernel or module initialization.  This plugin will
>> teach the compiler to find more such code and data that can be freed
>> after initialization.
>
>
> Currently checking whether we can wire this up for powerpc without too many
> problems...

Cool, thanks. FWIW, note that this plugin is a bit back-burnered at
the moment. I've got this in my -next tree still, but it needs some
rather large changes to how it does its annotations before Linus will
accept it.

>> diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
>> index 34a74131a12c..b98b8fdb7aaf 100644
>> --- a/arch/x86/lib/Makefile
>> +++ b/arch/x86/lib/Makefile
>> @@ -29,6 +29,10 @@ lib-$(CONFIG_RANDOMIZE_BASE) += kaslr.o
>>  obj-y += msr.o msr-reg.o msr-reg-export.o hweight.o
>>
>>  ifeq ($(CONFIG_X86_32),y)
>> +        CFLAGS_strstr_32.o +=
>> $(INITIFY_DISABLE_VERIFIY_NOCAPTURE_FUNCTIONS)
>> +        CFLAGS_string_32.o +=
>> $(INITIFY_DISABLE_VERIFIY_NOCAPTURE_FUNCTIONS)
>> +        CFLAGS_memcpy_32.o +=
>> $(INITIFY_DISABLE_VERIFIY_NOCAPTURE_FUNCTIONS)
>
>
> s/VERIFIY/VERIFY/g here + Makefile.gcc-plugins?

Ah, thanks for catching that! I'll get that fixed.

-Kees

-- 
Kees Cook
Pixel Security