From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751208AbWFRSar (ORCPT ); Sun, 18 Jun 2006 14:30:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751212AbWFRSar (ORCPT ); Sun, 18 Jun 2006 14:30:47 -0400 Received: from hosting-agency.de ([194.145.226.10]:35514 "EHLO mailagency.de") by vger.kernel.org with ESMTP id S1751208AbWFRSaq (ORCPT ); Sun, 18 Jun 2006 14:30:46 -0400 From: Simon Raffeiner Reply-To: sturmflut@lieberbiber.de Organization: Lieberbiber, Inc. To: "Randy.Dunlap" , linux-kernel@vger.kernel.org Subject: Re: [patch 2/3] vdso: improve print_fatal_signals support by adding memory maps Date: Sun, 18 Jun 2006 20:29:21 +0200 User-Agent: KMail/1.9.3 References: <200606171614.58610.sturmflut@lieberbiber.de> <200606181525.42199.sturmflut@lieberbiber.de> <20060618104218.b07fb540.rdunlap@xenotime.net> In-Reply-To: <20060618104218.b07fb540.rdunlap@xenotime.net> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1370453.uo97zKSEhO"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Message-Id: <200606182029.30247.sturmflut@lieberbiber.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org --nextPart1370453.uo97zKSEhO Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Am Sonntag, 18. Juni 2006 19:42 schrieben Sie: > On Sun, 18 Jun 2006 15:25:35 +0200 Simon Raffeiner wrote: > > Am Sonntag, 18. Juni 2006 07:58 schrieben Sie: > > > On Sat, 17 Jun 2006 21:58:18 -0700 > > > > > > "Randy.Dunlap" wrote: > > > > On Sat, 17 Jun 2006 16:14:52 +0200 Simon Raffeiner wrote: > > > > > When compiling 2.6.17-rc6-mm2 (which contains this patch) my gcc > > > > > 4.0.3 (Ubuntu 4.0.3-1ubuntu5) complains about "int len;" being us= ed > > > > > uninitialized in print_vma(). AFAICS len is not initialized and > > > > > then passed to > > > > > pad_len_spaces(int len), which uses it for some calculations. > > > > > > > > > > I also noticed that similar code is used in fs/proc/task_mmu.c, > > > > > where show_map_internal() passes an uninitialised int len; to > > > > > pad_len_spaces(struct seq_file *m, int len). > > > > > > > > Ack both of those. And both of them pass &len as a parameter to > > > > printk/seq_printf where it looks as though they want just > > > > (after it has been initialized). > > > > > > printk("%n", &len) will initialise `len'. gcc is being wrong again. > > > > pad_len_spaces() is called in the following way: > > > > > > static int print_vma(struct vm_area_struct *vma) > > { > > int len; > > > > (...) > > > > pad_len_spaces(len); > > > > (...) > > > > > > and is defined as: > > > > > > static void pad_len_spaces(int len) > > { > > len =3D 25 + sizeof(void*) * 6 - len; > > > > if (len < 1) > > len =3D 1; > > > > printk("%*c", len, ' '); > > } > > > > > > len is passed to pad_len_spaces() without initialization and is used for > > calculations BEFORE printk() is called. > > Nope, len is used after printk(..., &len) is called. > But I don't see how printk() inits len... ? :( Magic? I finally got it: %n in the format string advises printk (have a look at=20 lib/vsprintf.c, where vsnprintf() does the real work) to store the number o= f=20 characters that have been written so far to a given memory location. So len= =20 is actually initialised. =2D-=20 OpenPGP/GnuPG Key: 0xB2204FA0 @ subkeys.pgp.net "There is no point in having Linux on the Desktop if it's at the cost of it= =20 being the same crap that Windows is." - Benjamin Herrenschmidt --nextPart1370453.uo97zKSEhO Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.2 (GNU/Linux) iD8DBQBElZuKd2q78rIgT6ARAnjcAJsHfxT3vcLN+sPqU8B3/dGfQX2OZACfWR2P o1OmK1zDhY+Q/9AD/juKcUA= =n+ab -----END PGP SIGNATURE----- --nextPart1370453.uo97zKSEhO--