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Message-ID: <CAMuHMdW46hT9usJ-UxAnSKqzTdHfV+VKzU-L9O2NkSegTfbn9Q@mail.gmail.com>
Date: Sat, 23 Jan 2016 10:49:15 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Kees Cook <keescook@...omium.org>
Cc: Laura Abbott <laura@...bott.name>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, Ingo Molnar <mingo@...hat.com>,
Andy Lutomirski <luto@...capital.net>, "H. Peter Anvin" <hpa@...or.com>,
Michael Ellerman <mpe@...erman.id.au>, Mathias Krause <minipli@...glemail.com>,
Thomas Gleixner <tglx@...utronix.de>, "x86@...nel.org" <x86@...nel.org>, Arnd Bergmann <arnd@...db.de>,
PaX Team <pageexec@...email.hu>, Emese Revfy <re.emese@...il.com>,
LKML <linux-kernel@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH v4 0/8] introduce post-init read-only memory
Hi Kees,
On Fri, Jan 22, 2016 at 8:57 PM, Kees Cook <keescook@...omium.org> wrote:
> On Fri, Jan 22, 2016 at 11:16 AM, Laura Abbott <laura@...bott.name> wrote:
>> Kees had previously pushed a patch to do so but it exposed a couple of
>> underlying issues, mostly with low power paths
>> (c.f. http://article.gmane.org/gmane.linux.ports.arm.kernel/471199,
>> http://article.gmane.org/gmane.linux.kernel.mm/143489)
>> Those will need to be all fixed up before this could be made default.
I'm working on fixing that...
BTW, making the sections read-only is done quite late in the kernel startup
process, which means it doesn't trigger for the writes to the text segment in
secondary CPU bringup, but only for suspend/resume.
> Yeah, I've got a patch waiting to reorganize CONFIG_ARM_KERNMEM_PERMS
> to look more like arm64 (and x86) and get the feature correctly under
> CONFIG_DEBUG_RODATA. I made it default=y on v7+. rmk asked me to wait
> until -rc1 before resubmitting it.
>
> http://git.kernel.org/cgit/linux/kernel/git/kees/linux.git/commit/?h=kspp/arm-rodata&id=08bebfd2e7fb8a9f364ced74c356642d64e1f43e
One other concern is indeed memory usage ("ALIGN(1<<SECTION_SHIFT)"?).
Enabling CONFIG_ARM_KERNMEM_PERMS and CONFIG_DEBUG_RODATA in my test kernel
configs make the kernel too big to boot (overwritten DTB?) for 3 out of 4 arm
shmobile targets...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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