linux-kernel - Re: [PATCH v2 09/11] static_call: Make NULL static calls consistent

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Date:   Wed, 22 Mar 2023 11:35:29 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Jason Baron <jbaron@...mai.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Sami Tolvanen <samitolvanen@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Will McVicker <willmcvicker@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 09/11] static_call: Make NULL static calls consistent

On Wed, Mar 22, 2023 at 03:59:18PM +0100, Peter Zijlstra wrote:
> On Tue, Mar 21, 2023 at 09:00:15PM -0700, Josh Poimboeuf wrote:
> > +void __static_call_nop(void)
> > +{
> > +}
> > +EXPORT_SYMBOL_GPL(__static_call_nop);
> 
> Kees, is this a ROP target? The above is basically ENDBR;RET, push
> something on the stack, jump there and you're in business or so.

I could add __noendbr, except for the !HAVE_STATIC_CALL + !CFI_CLANG
case which actually needs to indirect call it.

-- 
Josh