Date: Tue, 1 Dec 2015 08:24:03 +0100 From: Ingo Molnar <mingo@...nel.org> To: Russell King - ARM Linux <linux@....linux.org.uk> Cc: Kees Cook <keescook@...omium.org>, Heiko Carstens <heiko.carstens@...ibm.com>, Michael Ellerman <mpe@...erman.id.au>, "James E.J. Bottomley" <jejb@...isc-linux.org>, Catalin Marinas <catalin.marinas@....com>, LKML <linux-kernel@...r.kernel.org>, Andy Lutomirski <luto@...capital.net>, "H. Peter Anvin" <hpa@...or.com>, Mathias Krause <minipli@...glemail.com>, Ingo Molnar <mingo@...hat.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>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, linux-arch <linux-arch@...r.kernel.org> Subject: Re: [PATCH v2 1/4] init: create cmdline param to disable readonly * Russell King - ARM Linux <linux@....linux.org.uk> wrote: > On Mon, Nov 30, 2015 at 01:52:10PM -0800, Kees Cook wrote: > > On Wed, Nov 25, 2015 at 11:51 PM, Ingo Molnar <mingo@...nel.org> wrote: > > > * Kees Cook <keescook@...omium.org> wrote: > > >> +#ifdef CONFIG_DEBUG_RODATA > > > > > > Btw., could you please remove the Kconfig option altogether in an additional patch > > > and make read-only sections an always-on feature? It has been default-y for years > > > and all distros have it enabled. > > > > Yeah, this is something I've wanted to do for a while, but I would > > point out that only a few architectures have actually implemented it, > > and for arm and arm64 it was very recent: > > I don't think it can entirely be a kernel command line option. On ARM, > enabling DEBUG_RODATA has a substantial effect on the size of the kernel > image - we have to pad various sections to 1MB boundaries so we can > set the appropriate permissions. > > Forcing this layout on everyone won't work. Yeah, so I'd suggest to have it always-on on x86 (after adding the boot option), to simplify the x86 code and to make it more obvious that we rely on this. There's a moderate amount of #ifdeffery around this: triton:~/tip> git grep -w CONFIG_DEBUG_RODATA arch/x86/ | grep \# | wc -l 15 Thanks, Ingo
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