linux-kernel - Re: [RFC PATCH 1/9] kernel: add support for patchable function pointers

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Message-ID: <20181005135728.GR19272@hirez.programming.kicks-ass.net>
Date:   Fri, 5 Oct 2018 15:57:28 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     linux-kernel@...r.kernel.org,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Samuel Neves <sneves@....uc.pt>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Richard Weinberger <richard@....at>,
        linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [RFC PATCH 1/9] kernel: add support for patchable function
 pointers

On Fri, Oct 05, 2018 at 10:13:25AM +0200, Ard Biesheuvel wrote:
> Add a function pointer abstraction that can be implemented by the arch
> in a manner that avoids the downsides of function pointers, i.e., the
> fact that they are typically located in a writable data section, and
> their vulnerability to Spectre like defects.
> 
> The FFP (or fast function pointer) is callable as a function, since
> the generic incarnation is simply that. However, due to the fact that
> C does not distinguish between functions and function pointers at the
> call site, the architecture can instead emit it as a patchable sequence
> of instructions consisting of ordinary branches.

This is basically a static_key, except for indirection function calls?
So why not call the thing static_func or static_call or something like
that?