netdev - Re: [PATCH 2/9] objtool: Fix ORC unwinding in non-JIT BPF generated code

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Message-ID: <20190614161101.vobuleyjap777ol5@treble>
Date:   Fri, 14 Jun 2019 11:11:01 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Song Liu <songliubraving@...com>,
        Kairui Song <kasong@...hat.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 2/9] objtool: Fix ORC unwinding in non-JIT BPF generated
 code

On Fri, Jun 14, 2019 at 08:13:49AM -0700, Alexei Starovoitov wrote:
> On Fri, Jun 14, 2019 at 1:11 AM Peter Zijlstra <peterz@...radead.org> wrote:
> >
> > On Fri, Jun 14, 2019 at 12:35:38AM -0700, Alexei Starovoitov wrote:
> > > On Fri, Jun 14, 2019 at 09:08:52AM +0200, Peter Zijlstra wrote:
> > > > On Thu, Jun 13, 2019 at 08:20:30PM -0500, Josh Poimboeuf wrote:
> > > > > On Thu, Jun 13, 2019 at 01:57:11PM -0700, Alexei Starovoitov wrote:
> > > >
> > > > > > and to patches 8 and 9.
> > > > >
> > > > > Well, it's your code, but ... can I ask why?  AT&T syntax is the
> > > > > standard for Linux, which is in fact the OS we are developing for.
> > > >
> > > > I agree, all assembly in Linux is AT&T, adding Intel notation only
> > > > serves to cause confusion.
> > >
> > > It's not assembly. It's C code that generates binary and here
> > > we're talking about comments.
> >
> > And comments are useless if they don't clarify. Intel syntax confuses.
> >
> > > I'm sure you're not proposing to do:
> > > /* mov src, dst */
> > > #define EMIT_mov(DST, SRC)                                                               \
> > > right?
> >
> > Which is why Josh reversed both of them. The current Intel order is just
> > terribly confusing. And I don't see any of the other JITs having
> > confusing comments like this.
> >
> > > bpf_jit_comp.c stays as-is. Enough of it.
> >
> > I think you're forgetting this is also arch/x86 code, and no, it needs
> > changes because its broken wrt unwinding.
> 
> See MAINTAINERS file.
> If you guys keep insisting on pointless churn like this
> we'll move arch/x86/net/ into net/ where it probably belongs.
> netdev has its own comment style too.
> And it is also probably confusing to some folks.

So if I understand correctly, you're proposing that we move x86-specific
code to net/arch/x86 so you don't have to make your code readable to
others and adhere to kernel style guidelines?

-- 
Josh