From owner-freebsd-current@FreeBSD.ORG Tue Oct 11 19:37:16 2011 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 56180106564A; Tue, 11 Oct 2011 19:37:16 +0000 (UTC) (envelope-from lacombar@gmail.com) Received: from mail-wy0-f182.google.com (mail-wy0-f182.google.com [74.125.82.182]) by mx1.freebsd.org (Postfix) with ESMTP id 83EDE8FC19; Tue, 11 Oct 2011 19:37:15 +0000 (UTC) Received: by wyj26 with SMTP id 26so11620900wyj.13 for ; Tue, 11 Oct 2011 12:37:14 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; bh=y2MFWDonDiyBm3/ThYDhfwjNhwVH0kiCzs49RjFYd30=; b=TDn6ccTpO8XeHKY4HvM7R6mq4ocCnvbi/oUW1wn35uG+mN7+ld0WuGOiWlSo/Ic6Qp OunP2cv7BL2UNyRZvxiUpxTD0cOCH8j9OD4uA1JaEDr/9baZ7UlRamUemW+dewJxbNTj EztwLtxdMn2M7ew1fLW9AC3rlugbyhksSNHZE= MIME-Version: 1.0 Received: by 10.227.29.161 with SMTP id q33mr6372613wbc.49.1318361834530; Tue, 11 Oct 2011 12:37:14 -0700 (PDT) Received: by 10.180.103.33 with HTTP; Tue, 11 Oct 2011 12:37:14 -0700 (PDT) In-Reply-To: <4E949351.5040904@lerctr.org> References: <4E942FF1.9000805@FreeBSD.org> <4E948D59.5020006@lerctr.org> <4E949351.5040904@lerctr.org> Date: Tue, 11 Oct 2011 15:37:14 -0400 Message-ID: From: Arnaud Lacombe To: Larry Rosenman Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: =?ISO-8859-1?Q?Ren=E9_Ladan?= , freebsd-current@freebsd.org, Dimitry Andric Subject: Re: System headers with clang? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 11 Oct 2011 19:37:16 -0000 Hi, On Tue, Oct 11, 2011 at 3:04 PM, Larry Rosenman wrote: > On 10/11/2011 1:52 PM, Arnaud Lacombe wrote: >> >> Hi, >> >> On Tue, Oct 11, 2011 at 2:39 PM, Larry Rosenman =A0wrote= : >>> >>> On 10/11/2011 1:36 PM, Arnaud Lacombe wrote: >>>> >>>> Hi, >>>> >>>> On Tue, Oct 11, 2011 at 8:00 AM, Dimitry Andric >>>> =A0wrote: >>>>> >>>>> On 2011-10-09 19:32, Larry Rosenman wrote: >>>>>> >>>>>> I had gotten a PR about sysutils/lsof not compiling with clang. =A0I= had >>>>>> Vic Abell check it out, and the problem is NOT with lsof per se, but >>>>>> with the system headers. >>>>>> >>>>>> Is there a project afoot to update the system headers to make them >>>>>> clang >>>>>> compilable? >>>>> >>>>> The problem isn't that clang can't compile the system headers, but >>>>> normally these don't get included from userspace. =A0And they certain= ly >>>>> won't work as expected when you define _KERNEL in userspace, as the >>>>> lsof >>>>> port foolishly does. =A0It probably can't be avoided in such a tool, >>>>> though. >>>>> >>>> #ifdef _KERNEL/#endif protected part of system headers shall NEVER be >>>> accessed by userland. It is a fault to have them present in >>>> /usr/include. Linux got it right there, all those part are removed >>>> upon headers' installation. >>>> >>>> =A0- Arnaud >>> >>> Then lsof would NOT be compilable / usable at all, as it delves into >>> /dev/kmem to get information. >>> >> AFAIK, Linux is capable of supporting lsof in a backward compatible >> manner, without exposing its internal guts. >> >> FWIW, KVM is a bad kernel/userland interface, as it does not guarantee >> backward compatibility. >> >>> And it **NEEDS** to know what the structures are. >>> >> No, not kernel-only structure. Now, if these structure are not meant >> to be kernel only, move them out of _KERNEL area, but beware of >> backward compatibility issue in the future. > > Therein lies the rub. =A0In order to do it's job, it DOES need to grovel > around in kernel only structures. > > >> >>> That is unless someone(tm) writes the Kernel interfaces to get the info= . >>> >> Yes, this is the core of the problem and a classical chicken/eggs >> problem solves the very wrongest way. >> >> At some point, I thought to modify the build system to pass kernel's >> headers through unifdef(1), but I quickly forgot about that: >> >> % git grep 'define _KERNEL' * | grep -v '^sys' | wc -l >> =A0 =A0 =A0 27 >> >> =A0- Arnaud > > This is not going to fix things until/unless someone(tm) takes the bull b= y > the horns, and writes > a userland<->kernel interface to get ALL the data that lsof currently > gathers from groveling around > in /dev/kmem. > > I don't have the skills nor time to do that. > What are those interfaces exactly ? How is it done in Linux ? Thanks, - Arnaud