[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] x86: PIE support and option to extend KASLR randomization
- To: "H. Peter Anvin" <hpa@xxxxxxxxx>
- From: Thomas Garnier <thgarnie@xxxxxxxxxx>
- Date: Fri, 22 Sep 2017 11:59:00 -0700
- Cc: Nicolas Pitre <nicolas.pitre@xxxxxxxxxx>, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxx>, kvm list <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>, Kernel Hardening <kernel-hardening@xxxxxxxxxxxxxxxxxx>, Christoph Lameter <cl@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Kees Cook <keescook@xxxxxxxxxxxx>, the arch/x86 maintainers <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 <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Sparse Mailing-list <linux-sparse@xxxxxxxxxxxxxxx>, Matthias Kaehlcke <mka@xxxxxxxxxxxx>, linux-arch <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 list <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>, LKML <linux-kernel@xxxxxxxxxxxxxxx>, Kyle Huey <me@xxxxxxxxxxxx>, Lukas Wunner <lukas@xxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Linux Crypto Mailing List <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, 22 Sep 2017 18:59:09 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Fri, Sep 22, 2017 at 11:38 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 09/22/17 09:32, Ingo Molnar wrote:
>>
>> BTW., I think things improved with ORC because with ORC we have RBP as an
>> extra
>> register and with PIE we lose RBX - so register pressure in code generation
>> is
>> lower.
>>
>
> We lose EBX on 32 bits, but we don't lose RBX on 64 bits - since x86-64
> has RIP-relative addressing there is no need for a dedicated PIC register.
>
> I'm somewhat confused how we can have as much as almost 1% overhead. I
> suspect that we end up making a GOT and maybe even a PLT for no good reason.
We have a GOT with very few entries, mainly linker script globals that
I think we can work to reduce or remove.
We have a PLT but it is empty. On latest iteration (not sent yet),
modules have PLT32 relocations but no PLT entry. I got rid of
mcmodel=large for modules and instead I move the beginning of the
module section just after the kernel so relative relocations work.
>
> -hpa
--
Thomas
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel
|
