linux-kernel - Re: [PATCH RFC 1/7] x86/head/64: Mark startup_gdt and startup_gdt_descr as _

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Message-ID: <20231110000352.zr6z6yofumdbk4wd@treble>
Date:   Thu, 9 Nov 2023 16:03:52 -0800
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     "H. Peter Anvin" <hpa@...or.com>,
        Kristen Carlson Accardi <kristen@...ux.intel.com>,
        Hou Wenlong <houwenlong.hwl@...group.com>,
        linux-kernel@...r.kernel.org,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE 32-BIT AND 64-BIT" <x86@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mike Rapoport <rppt@...nel.org>,
        Pasha Tatashin <pasha.tatashin@...een.com>
Subject: Re: [PATCH RFC 1/7] x86/head/64: Mark startup_gdt and
 startup_gdt_descr as __initdata

On Wed, Oct 18, 2023 at 01:45:40PM +0200, Ingo Molnar wrote:
> 
> * H. Peter Anvin <hpa@...or.com> wrote:
> 
> > If the goal is better KASLR, then what we really should spend time on was 
> > Kristen Accardi's fgKASLR patches, which not only exponentially(!) 
> > increases the randomization entrophy but also *actually* avoids the "one 
> > leak and it's over" problem.
> 
> Agreed. Going by this version of function-granularity KASLR from 3 years 
> ago:
> 
>   https://lwn.net/Articles/824307/
>   https://lwn.net/ml/linux-kernel/20200623172327.5701-1-kristen@linux.intel.com/
> 
> The fgKASLR feature looks entirely viable to me. Back then I presumed it 
> would get iterated beyond v3, and then it fell off my radar. :-/
> 
> If Kristen or someone else would like to dust this off & submit a fresh 
> version it would be much appreciated!

That actually got up to v10:

  https://lkml.kernel.org/lkml/20220209185752.1226407-1-alexandr.lobakin@intel.com

Anyway, I'm also very interested in this.  If nobody else is working on
it then I could give it a try.

BTW I've wondered if translation-unit granularity would be more
preferable than function granularity due to improved i-cache locality
and (possibly) easier livepatch compatibility.

-- 
Josh