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Message-ID: <1502900796.1302.52.camel@gmail.com> Date: Wed, 16 Aug 2017 12:26:36 -0400 From: Daniel Micay <danielmicay@...il.com> To: Ingo Molnar <mingo@...nel.org>, Thomas Garnier <thgarnie@...gle.com> Cc: 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>, Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...hat.com>, Arnd Bergmann <arnd@...db.de>, Matthias Kaehlcke <mka@...omium.org>, Boris Ostrovsky <boris.ostrovsky@...cle.com>, Juergen Gross <jgross@...e.com>, Paolo Bonzini <pbonzini@...hat.com>, Radim Krčmář <rkrcmar@...hat.com>, Joerg Roedel <joro@...tes.org>, Tom Lendacky <thomas.lendacky@....com>, Andy Lutomirski <luto@...nel.org>, Borislav Petkov <bp@...e.de>, Brian Gerst <brgerst@...il.com>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, "Rafael J . Wysocki" <rjw@...ysocki.net>, Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>, Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>, Paul Gortmaker <paul.gortmaker@...driver.com>, Chris Metcalf <cmetcalf@...lanox.com>, Andrew Morton <akpm@...ux-foundation.org>, "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>, Nicolas Pitre <nicolas.pitre@...aro.org>, Christopher Li <sparse@...isli.org>, "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>, Lukas Wunner <lukas@...ner.de>, Mika Westerberg <mika.westerberg@...ux.intel.com>, Dou Liyang <douly.fnst@...fujitsu.com>, Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov <ast@...nel.org>, Masahiro Yamada <yamada.masahiro@...ionext.com>, Markus Trippelsdorf <markus@...ppelsdorf.de>, Steven Rostedt <rostedt@...dmis.org>, Kees Cook <keescook@...omium.org>, Rik van Riel <riel@...hat.com>, David Howells <dhowells@...hat.com>, Waiman Long <longman@...hat.com>, Kyle Huey <me@...ehuey.com>, Peter Foley <pefoley2@...oley.com>, Tim Chen <tim.c.chen@...ux.intel.com>, Catalin Marinas <catalin.marinas@....com>, Ard Biesheuvel <ard.biesheuvel@...aro.org>, Michal Hocko <mhocko@...e.com>, Matthew Wilcox <mawilcox@...rosoft.com>, "H . J . Lu" <hjl.tools@...il.com>, Paul Bolle <pebolle@...cali.nl>, Rob Landley <rob@...dley.net>, Baoquan He <bhe@...hat.com>, the arch/x86 maintainers <x86@...nel.org>, linux-crypto@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>, xen-devel@...ts.xenproject.org, kvm list <kvm@...r.kernel.org>, Linux PM list <linux-pm@...r.kernel.org>, linux-arch <linux-arch@...r.kernel.org>, linux-sparse@...r.kernel.org, Kernel Hardening <kernel-hardening@...ts.openwall.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Borislav Petkov <bp@...en8.de> Subject: Re: x86: PIE support and option to extend KASLR randomization > How are these assumptions hardcoded by GCC? Most of the instructions > should be > relocatable straight away, as most call/jump/branch instructions are > RIP-relative. > > I.e. is there no GCC code generation mode where code can be placed > anywhere in the > canonical address space, yet call and jump distance is within 31 bits > so that the > generated code is fast? That's what PIE is meant to do. However, not disabling support for lazy linking (-fno-plt) / symbol interposition (-Bsymbolic) is going to cause it to add needless overhead. arm64 is using -pie -shared -Bsymbolic in arch/arm64/Makefile for their CONFIG_RELOCATABLE option. See 08cc55b2afd97a654f71b3bebf8bb0ec89fdc498.
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