linux-hardening - Re: [RFC PATCH 00/21] KCFI support

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Message-ID: <YnA3Le2uJRaFF4TC@hirez.programming.kicks-ass.net>
Date:   Mon, 2 May 2022 21:55:25 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Sami Tolvanen <samitolvanen@...gle.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Mark Rutland <mark.rutland@....com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Joao Moreira <joao@...rdrivepizza.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        linux-hardening@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        llvm@...ts.linux.dev
Subject: Re: [RFC PATCH 00/21] KCFI support

On Mon, May 02, 2022 at 08:22:57AM -0700, Sami Tolvanen wrote:

> > Anyway, I think I hate that __builtin, I'd *much* rather see a variable
> > attribute or qualifier for this, such that one can mark a function
> > pointer as not doing CFI.
> >
> > I simply doesn't make sense to have a builtin that operates on an
> > expression. The whole thing is about indirect calls, IOW function
> > pointers.
> 
> I also thought an attribute would be more convenient, but the compiler
> folks prefer a built-in:
> 
> https://reviews.llvm.org/D122673

That seems to mostly worry about C++ things (overload sets, template
specialization, name mangling) we kernel folks don't seem to much care
about.

I'll stick with saying type system makes more sense to me though.