linux-kernel - Re: [PATCH 07/14] x86/ibt: Clean up is

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240928130835.GA19439@noisy.programming.kicks-ass.net>
Date: Sat, 28 Sep 2024 15:08:35 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, alyssa.milburn@...el.com,
	scott.d.constable@...el.com, joao@...rdrivepizza.com,
	andrew.cooper3@...rix.com, jose.marchesi@...cle.com,
	hjl.tools@...il.com, ndesaulniers@...gle.com,
	samitolvanen@...gle.com, nathan@...nel.org, ojeda@...nel.org,
	kees@...nel.org, alexei.starovoitov@...il.com,
	Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH 07/14] x86/ibt: Clean up is_endbr()

On Fri, Sep 27, 2024 at 05:04:44PM -0700, Josh Poimboeuf wrote:
> On Fri, Sep 27, 2024 at 09:49:03PM +0200, Peter Zijlstra wrote:
> > Pretty much every caller of is_endbr() actually wants to test something at an
> > address and ends up doing get_kernel_nofault(). Fold the lot into a more
> > convenient helper.
> > 
> > Note: this effectively reverts commit a8497506cd2c ("bpf: Avoid
> > get_kernel_nofault() to fetch kprobe entry IP") which was entirely the
> > wrong way to go about doing things. The right solution is to optimize
> > get_kernel_nofault() itself, it really doesn't need STAC/CLAC nor the
> > speculation barrier. Using __get_user is a historical hack, not a
> > requirement.
> 
> But these patches don't actually optimize get_kernel_nofault()?

No, I figured there was enough there already. Also, given the state I
was in, I'd probably get it wrong.

I have it on a todo list somewhere though. It shouldn't be too hard.