From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from desiato.infradead.org (desiato.infradead.org [90.155.92.199])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A8EF3204
	for <llvm@lists.linux.dev>; Mon,  2 May 2022 19:55:48 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed;
	d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version:
	References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:
	Content-Transfer-Encoding:Content-ID:Content-Description;
	bh=mYYa7YhSPmVPESGC3WBfSUVLu7/5dL6ovKiS3tnTNxc=; b=X7JjkI1eS+hZwlLL/I9p7ec0h2
	UeIxqvrdiJt3meq6ElbsNEDYIxW+qZz/j2FrSu6coXltcfr4QtTMMPFDzslv9IR5A31jl1ddBKnH9
	c2qsGdbgoQzF9iywxqp5QHtMYcYLEB3+RVk8mUsIOTnJ93L7VRDhLz56q/kJE1S8EfyygaZ+EPJH4
	+lUKye+VxqZ8KUh1eKBescSHXrCybAweDQoUoV1TG8LbXYRpZEdQGzvMqMTJ67eTO75Z/LyqmGrAJ
	WIdEZp2LKR7NJxMrEW0UmH4MNpVWroXNW+J0b79QIxFrPP2W8RHSAR29nZiASkc9sS+Ga1qVVPW+d
	6RQX6kKQ==;
Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net)
	by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux))
	id 1nlc8m-00AZWD-7z; Mon, 02 May 2022 19:55:28 +0000
Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225])
	(using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)
	 key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256)
	(Client did not present a certificate)
	by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 772E030017D;
	Mon,  2 May 2022 21:55:25 +0200 (CEST)
Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000)
	id 5223120288CEB; Mon,  2 May 2022 21:55:25 +0200 (CEST)
Date: Mon, 2 May 2022 21:55:25 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Sami Tolvanen <samitolvanen@google.com>
Cc: Kees Cook <keescook@chromium.org>, Mark Rutland <mark.rutland@arm.com>,
	Josh Poimboeuf <jpoimboe@redhat.com>, Will Deacon <will@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Joao Moreira <joao@overdrivepizza.com>,
	Sedat Dilek <sedat.dilek@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
	linux-hardening@vger.kernel.org,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	llvm@lists.linux.dev
Subject: Re: [RFC PATCH 00/21] KCFI support
Message-ID: <YnA3Le2uJRaFF4TC@hirez.programming.kicks-ass.net>
References: <20220429203644.2868448-1-samitolvanen@google.com>
 <202204291545.47C6A97EA2@keescook>
 <Ymz7DWkRJy3PMaHm@hirez.programming.kicks-ass.net>
 <CABCJKuckt75qA1op-LpkJnQsJC36m9fstbY3uD=7pET2VyyZSg@mail.gmail.com>
Precedence: bulk
X-Mailing-List: llvm@lists.linux.dev
List-Id: <llvm.lists.linux.dev>
List-Subscribe: <mailto:llvm+subscribe@lists.linux.dev>
List-Unsubscribe: <mailto:llvm+unsubscribe@lists.linux.dev>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <CABCJKuckt75qA1op-LpkJnQsJC36m9fstbY3uD=7pET2VyyZSg@mail.gmail.com>

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.