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

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Message-ID: <20240928000444.grd3jxltzoiihsz3@treble>
Date: Fri, 27 Sep 2024 17:04:44 -0700
From: Josh Poimboeuf <jpoimboe@...nel.org>
To: Peter Zijlstra <peterz@...radead.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 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()?

-- 
Josh