linux-kernel - Re: [PATCH v2 08/11] arm64/static_call: Fix static call CFI violations

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Message-ID: <20230322182617.eyfphw4o2tm5yqi2@treble>
Date:   Wed, 22 Mar 2023 11:26:17 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Mark Rutland <mark.rutland@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, 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 08/11] arm64/static_call: Fix static call CFI
 violations

On Wed, Mar 22, 2023 at 03:19:33PM +0100, Peter Zijlstra wrote:
> On Wed, Mar 22, 2023 at 12:22:07PM +0000, Mark Rutland wrote:
> > On Tue, Mar 21, 2023 at 09:00:14PM -0700, Josh Poimboeuf wrote:
> 
> > > +++ b/arch/arm64/include/asm/static_call.h
> > > @@ -0,0 +1,29 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 */
> > > +#ifndef _ASM_ARM64_STATIC_CALL_H
> > > +#define _ASM_ARM64_STATIC_CALL_H
> > > +
> > > +/*
> > > + * Make a dummy reference to a function pointer in C to force the compiler to
> > > + * emit a __kcfi_typeid_ symbol for asm to use.
> > > + */
> > > +#define GEN_CFI_SYM(func)						\
> > > +	static typeof(func) __used __section(".discard.cfi") *__UNIQUE_ID(cfi) = func
> > > +
> > > +
> > > +/* Generate a CFI-compliant static call NOP function */
> > > +#define __ARCH_DEFINE_STATIC_CALL_CFI(name, insns)			\
> > > +	asm(".align 4						\n"	\
> 
> Should this ^ be:
> 
> 	__ALIGN_STR "\n" \

Ah right, you did mention that before.  Will do.

-- 
Josh