Date: Tue, 6 Aug 2019 17:50:34 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Borislav Petkov <bp@...en8.de> Cc: Thomas Garnier <thgarnie@...omium.org>, kernel-hardening@...ts.openwall.com, kristen@...ux.intel.com, keescook@...omium.org, Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, Andy Lutomirski <luto@...nel.org>, Juergen Gross <jgross@...e.com>, Thomas Hellstrom <thellstrom@...are.com>, "VMware, Inc." <pv-drivers@...are.com>, "Rafael J. Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>, Nadav Amit <namit@...are.com>, Jann Horn <jannh@...gle.com>, Feng Tang <feng.tang@...el.com>, Maran Wilson <maran.wilson@...cle.com>, Enrico Weigelt <info@...ux.net>, Allison Randal <allison@...utok.net>, Alexios Zavras <alexios.zavras@...el.com>, linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org, linux-pm@...r.kernel.org Subject: Re: [PATCH v9 00/11] x86: PIE support to extend KASLR randomization On Tue, Aug 06, 2019 at 05:43:47PM +0200, Borislav Petkov wrote: > On Tue, Jul 30, 2019 at 12:12:44PM -0700, Thomas Garnier wrote: > > These patches make some of the changes necessary to build the kernel as > > Position Independent Executable (PIE) on x86_64. Another patchset will > > add the PIE option and larger architecture changes. > > Yeah, about this: do we have a longer writeup about the actual benefits > of all this and why we should take this all? After all, after looking > at the first couple of asm patches, it is posing restrictions to how > we deal with virtual addresses in asm (only RIP-relative addressing in > 64-bit mode, MOVs with 64-bit immediates, etc, for example) and I'm > willing to bet money that some future unrelated change will break PIE > sooner or later. Possibly objtool can help here; it should be possible to teach it about these rules, and then it will yell when violated. That should avoid regressions.
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