linux-kernel - Re: Stackleak vs noinstr (Was: [GIT pull] objtool/core for v5.16-rc1)

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Date:   Wed, 3 Nov 2021 09:19:35 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexander Popov <alex.popov@...ux.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>
Subject: Re: Stackleak vs noinstr (Was: [GIT pull] objtool/core for v5.16-rc1)

On Wed, Nov 03, 2021 at 10:18:22AM +0300, Alexander Popov wrote:
> Yes, this is a correct approach.
> 
> But I'm not sure about removing NOKPROBE_SYMBOL and notrace for
> stackleak_erase. Does the code in noinstr.text disable all those?

Yes, noinstr implies all those and more. Both kprobe and tracing are a
form of instrumentation, and hence noinstr must disallow it.