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Re: [Xen-devel] x86: PIE support and option to extend KASLR randomization
- To: Thomas Garnier <thgarnie@xxxxxxxxxx>
- From: Ingo Molnar <mingo@xxxxxxxxxx>
- Date: Fri, 11 Aug 2017 14:41:27 +0200
- Cc: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxx>, kvm@xxxxxxxxxxxxxxx, Radim Krčmář <rkrcmar@xxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Christopher Li <sparse@xxxxxxxxxxx>, Alexei Starovoitov <ast@xxxxxxxxxx>, David Howells <dhowells@xxxxxxxxxx>, Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>, Pavel Machek <pavel@xxxxxx>, "H . Peter Anvin" <hpa@xxxxxxxxx>, kernel-hardening@xxxxxxxxxxxxxxxxxx, Christoph Lameter <cl@xxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>, x86@xxxxxxxxxx, Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>, Daniel Borkmann <daniel@xxxxxxxxxxxxx>, Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>, Peter Foley <pefoley2@xxxxxxxxxxx>, Joerg Roedel <joro@xxxxxxxxxx>, "Rafael J . Wysocki" <rafael.j.wysocki@xxxxxxxxx>, Daniel Micay <danielmicay@xxxxxxxxx>, Baoquan He <bhe@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-sparse@xxxxxxxxxxxxxxx, Matthias Kaehlcke <mka@xxxxxxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, Waiman Long <longman@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxx>, Markus Trippelsdorf <markus@xxxxxxxxxxxxxxx>, Len Brown <len.brown@xxxxxxxxx>, Rik van Riel <riel@xxxxxxxxxx>, Chris Metcalf <cmetcalf@xxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, linux-pm@xxxxxxxxxxxxxxx, Brian Gerst <brgerst@xxxxxxxxx>, "H . J . Lu" <hjl.tools@xxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Josh Poimboeuf <jpoimboe@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Dou Liyang <douly.fnst@xxxxxxxxxxxxxx>, Paul Bolle <pebolle@xxxxxxxxxx>, "Paul E . McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>, Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>, "Rafael J . Wysocki" <rjw@xxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Kyle Huey <me@xxxxxxxxxxxx>, Lukas Wunner <lukas@xxxxxxxxx>, linux-crypto@xxxxxxxxxxxxxxx, Rob Landley <rob@xxxxxxxxxxx>, Tejun Heo <tj@xxxxxxxxxx>, Paolo Bonzini <pbonzini@xxxxxxxxxx>, Tom Lendacky <thomas.lendacky@xxxxxxx>, Tim Chen <tim.c.chen@xxxxxxxxxxxxxxx>, "David S . Miller" <davem@xxxxxxxxxxxxx>, "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
- Delivery-date: Fri, 11 Aug 2017 12:41:41 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
* Thomas Garnier <thgarnie@xxxxxxxxxx> wrote:
> Changes:
> - v2:
> - Add support for global stack cookie while compiler default to fs without
> mcmodel=kernel
> - Change patch 7 to correctly jump out of the identity mapping on kexec
> load
> preserve.
>
> These patches make the changes necessary to build the kernel as Position
> Independent Executable (PIE) on x86_64. A PIE kernel can be relocated below
> the top 2G of the virtual address space. It allows to optionally extend the
> KASLR randomization range from 1G to 3G.
So this:
61 files changed, 923 insertions(+), 299 deletions(-)
... is IMHO an _awful_ lot of churn and extra complexity in pretty fragile
pieces
of code, to gain what appears to be only ~1.5 more bits of randomization!
Do these changes get us closer to being able to build the kernel as truly
position
independent, i.e. to place it anywhere in the valid x86-64 address space? Or
any
other advantages?
Thanks,
Ingo
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