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Message-ID: <87ikuj30g8.fsf@linux.intel.com>
Date: Wed, 25 Sep 2024 14:09:11 -0700
From: Andi Kleen <ak@...ux.intel.com>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>,
x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, Andy Lutomirski
<luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Uros Bizjak
<ubizjak@...il.com>, Dennis Zhou <dennis@...nel.org>, Tejun Heo
<tj@...nel.org>, Christoph Lameter <cl@...ux.com>, Mathieu Desnoyers
<mathieu.desnoyers@...icios.com>, Paolo Bonzini <pbonzini@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>, Juergen Gross <jgross@...e.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>, Greg Kroah-Hartman
<gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>, Masahiro
Yamada <masahiroy@...nel.org>, Kees Cook <kees@...nel.org>, Nathan
Chancellor <nathan@...nel.org>, Keith Packard <keithp@...thp.com>,
Justin Stitt <justinstitt@...gle.com>, Josh Poimboeuf
<jpoimboe@...nel.org>, Arnaldo Carvalho de Melo <acme@...nel.org>,
Namhyung Kim <namhyung@...nel.org>
Subject: Re: [RFC PATCH 25/28] x86: Use PIE codegen for the core kernel
Ard Biesheuvel <ardb+git@...gle.com> writes:
> This substantially reduces the number of relocations that need to be
> processed when booting a relocatable KASLR kernel.
>
> Before (size in bytes of the reloc table):
>
> 797372 arch/x86/boot/compressed/vmlinux.relocs
>
> After:
>
> 400252 arch/x86/boot/compressed/vmlinux.relocs
I don't know why anybody would care about the size of the relocation table?
What matters is what it does to general performance.
Traditionally even on x86-64 PIC/E has a cost and the kernel model
was intended to avoid that.
>From my perspective this patch kit doesn't fix a real problem,
it's all risk of performance regression with no gain.
-Andi
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