Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 14 Oct 2021 12:06:54 -0700
From:   Josh Poimboeuf <jpoimboe@redhat.com>
To:     Steven Rostedt <rostedt@goodmis.org>
Cc:     Kees Cook <keescook@chromium.org>, Borislav Petkov <bp@alien8.de>,
        Sami Tolvanen <samitolvanen@google.com>, x86@kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org,
        llvm@lists.linux.dev
Subject: Re: [PATCH v5 09/15] x86: Use an opaque type for functions not
 callable from C
Message-ID: <20211014190654.gn2jd43vw35gzdvs@treble>
References: <20211013181658.1020262-1-samitolvanen@google.com>
 <20211013181658.1020262-10-samitolvanen@google.com>
 <YWgSwmzPFrRbMC1P@zn.tnic>
 <202110140904.41B5183E@keescook>
 <YWhpbu/Y6V2p/zlY@zn.tnic>
 <202110141141.870A67E@keescook>
 <20211014145211.573579e6@gandalf.local.home>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20211014145211.573579e6@gandalf.local.home>
Precedence: bulk

On Thu, Oct 14, 2021 at 02:52:11PM -0400, Steven Rostedt wrote:
> On Thu, 14 Oct 2021 11:47:01 -0700
> Kees Cook <keescook@chromium.org> wrote:
> 
> > On Thu, Oct 14, 2021 at 07:31:26PM +0200, Borislav Petkov wrote:
> > > On Thu, Oct 14, 2021 at 09:07:57AM -0700, Kees Cook wrote:
> > > Looking at the changelog, DECLARE_ASM_FUNC_SYMBOL, makes a lot more
> > > sense to me even if it doesn't specify the aspect that it is not called
> > > by C but who cares - it is generic enough.  
> > 
> > Around we go. :) Josh[1] and Steven[2] explicitly disagreed with
> > that name, leading to the current name[3]. Do you want it to be
> > DECLARE_ASM_FUNC_SYMBOL() over those objections?
> 
> Just note, that I was fine with the original name, but was against the
> version Josh suggested ;-)

Naming is important, especially for something as confusing as this.  We
need to be able to read it in a few months and have some idea of what's
going on.

"DECLARE_ASM_FUNC_SYMBOL" is nonsensical.  As a reader of the code I
wonder why are some asm functions using it and not others?  And how do I
know if I need it for my new function?

"extern const u8 int3_magic[]" is even worse.  Why are some asm
functions randomly declared as arrays, and others not?  Where can I go
to find out more without digging through the commit log?

-- 
Josh