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

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Message-ID: <20230322183318.pqu2jjmi33j4an33@treble>
Date:   Wed, 22 Mar 2023 11:33:18 -0700
From:   Josh Poimboeuf <jpoimboe@...nel.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.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>,
        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 11:07:21AM -0700, Sami Tolvanen wrote:
> > +/*
> > + * 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
> 
> Couldn't we just use __ADDRESSABLE instead of adding a separate macro?
> The type of the variable shouldn't matter here, as long as we take the
> address of func.

Oh I did pretty much reimplement __ADDRESSABLE didn't I ;-)

-- 
Josh