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Message-ID: <c0bc2d98-d6eb-e3db-3799-2e28e9919f3d@zytor.com>
Date: Tue, 18 Jul 2017 18:35:05 -0700
From: "H. Peter Anvin" <hpa@...or.com>
To: Thomas Garnier <thgarnie@...gle.com>,
Herbert Xu <herbert@...dor.apana.org.au>,
"David S . Miller" <davem@...emloft.net>,
Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.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>, Andy Lutomirski <luto@...nel.org>,
Borislav Petkov <bp@...en8.de>,
"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
Brian Gerst <brgerst@...il.com>, Borislav Petkov <bp@...e.de>,
Christian Borntraeger <borntraeger@...ibm.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>,
Kees Cook <keescook@...omium.org>,
Paul Gortmaker <paul.gortmaker@...driver.com>,
Chris Metcalf <cmetcalf@...lanox.com>,
"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Christopher Li <sparse@...isli.org>,
Dou Liyang <douly.fnst@...fujitsu.com>,
Masahiro Yamada <yamada.masahiro@...ionext.com>,
Daniel Borkmann <daniel@...earbox.net>,
Markus Trippelsdorf <markus@...ppelsdorf.de>,
Peter Foley <pefoley2@...oley.com>,
Steven Rostedt <rostedt@...dmis.org>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Ard Biesheuvel <ard.biesheuvel@...aro.org>,
Catalin Marinas <catalin.marinas@....com>,
Matthew Wilcox <mawilcox@...rosoft.com>,
Michal Hocko <mhocko@...e.com>, Rob Landley <rob@...dley.net>,
Jiri Kosina <jkosina@...e.cz>, "H . J . Lu" <hjl.tools@...il.com>,
Paul Bolle <pebolle@...cali.nl>, Baoquan He <bhe@...hat.com>,
Daniel Micay <danielmicay@...il.com>
Cc: x86@...nel.org, linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
xen-devel@...ts.xenproject.org, kvm@...r.kernel.org,
linux-pm@...r.kernel.org, linux-arch@...r.kernel.org,
linux-sparse@...r.kernel.org, kernel-hardening@...ts.openwall.com
Subject: Re: [RFC 21/22] x86/module: Add support for mcmodel large and PLTs
On 07/18/17 15:33, Thomas Garnier wrote:
> With PIE support and KASLR extended range, the modules may be further
> away from the kernel than before breaking mcmodel=kernel expectations.
>
> Add an option to build modules with mcmodel=large. The modules generated
> code will make no assumptions on placement in memory.
>
> Despite this option, modules still expect kernel functions to be within
> 2G and generate relative calls. To solve this issue, the PLT arm64 code
> was adapted for x86_64. When a relative relocation go outside its range,
> a dynamic PLT entry is used to correctly jump to the destination.
Why large as opposed to medium or medium-PIC?
-hpa
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