From owner-freebsd-hackers@FreeBSD.ORG Thu Nov 7 06:12:40 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 88C6CE4C; Thu, 7 Nov 2013 06:12:40 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id 0D03B2D65; Thu, 7 Nov 2013 06:12:39 +0000 (UTC) Received: from tom.home (kostik@localhost [127.0.0.1]) by kib.kiev.ua (8.14.7/8.14.7) with ESMTP id rA76CYbA067753; Thu, 7 Nov 2013 08:12:34 +0200 (EET) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.8.3 kib.kiev.ua rA76CYbA067753 Received: (from kostik@localhost) by tom.home (8.14.7/8.14.7/Submit) id rA76CYPs067752; Thu, 7 Nov 2013 08:12:34 +0200 (EET) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Thu, 7 Nov 2013 08:12:34 +0200 From: Konstantin Belousov To: Mark Johnston Subject: Re: dl_iterate_phdr() omits ld-elf.so Message-ID: <20131107061234.GO59496@kib.kiev.ua> References: <20131106052010.GB2826@raichu> <20131106171301.GG59496@kib.kiev.ua> <20131106231352.GB86666@charmander.sandvine.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="xQILpJsL5cebVBoz" Content-Disposition: inline In-Reply-To: <20131106231352.GB86666@charmander.sandvine.com> User-Agent: Mutt/1.5.22 (2013-10-16) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no version=3.3.2 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on tom.home Cc: freebsd-hackers@freebsd.org X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Nov 2013 06:12:40 -0000 --xQILpJsL5cebVBoz Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Nov 06, 2013 at 06:13:52PM -0500, Mark Johnston wrote: > On Wed, Nov 06, 2013 at 07:13:01PM +0200, Konstantin Belousov wrote: > > On Wed, Nov 06, 2013 at 12:20:10AM -0500, Mark Johnston wrote: > > > Hello, > > >=20 > > > While experimenting with dl_iterate_phdr(3), I noticed that it doesn't > > > include the runtime linker itself in the list of objects. This is > > > inconsistent with related interfaces such as /map in procfs, and > > > kinfo_getvmmap(3), so it seems incorrect to me that rtld is excluded > > > from the list of callback arguments. > > >=20 > > > Is there a reason for this behaviour? If not, does anyone have though= ts > > > on the diff below which fixes this? > > >=20 > > > Thanks, > > > -Mark > > >=20 > > > diff --git a/libexec/rtld-elf/rtld.c b/libexec/rtld-elf/rtld.c > > > index fa6dc2a..b55effa 100644 > > > --- a/libexec/rtld-elf/rtld.c > > > +++ b/libexec/rtld-elf/rtld.c > > > @@ -3269,6 +3269,11 @@ dl_iterate_phdr(__dl_iterate_hdr_callback call= back, void *param) > > > break; > > > =20 > > > } > > > + if (error =3D=3D 0) { > > > + rtld_fill_dl_phdr_info(&obj_rtld, &phdr_info); > > > + error =3D callback(&phdr_info, sizeof(phdr_info), param); > > > + } > > > + > > > lock_release(rtld_bind_lock, &bind_lockstate); > > > lock_release(rtld_phdr_lock, &phdr_lockstate); > >=20 > > I cannot make a case where this patch would be problematic, but rtld is > > very special object in the process address space indeed. The patch is > > needed exactly because rtld is not included into the list of the loaded > > objects, and more, symbol resolution from rtld is a special case. Doing > > dlopen() on rtld path would probably break things in funny way. > >=20 > > Still, I think the patch is worth committing, but be prepared to handle > > the broken cases, which could come out in quite indirect ways. > >=20 > > BTW, why do you need this ? >=20 > I was just trying to find a portable way to figure out the address at > which a given object was located, and noticed the omission because the > runtime linker is included in the list on Linux. It seemed like a bug to > me just based on what dl_iterate_phdr(3) is supposed to do: invoke a > callback for each loaded ELF object, which includes rtld even though > it's special. >=20 > So I don't really need this change. In this case, do you still think > it's worth committing? Or should I just leave it alone? It seems to make the function more logical. As I said, I think that the patch is worth committing. --xQILpJsL5cebVBoz Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (FreeBSD) iQIcBAEBAgAGBQJSey9RAAoJEJDCuSvBvK1BCZUQAKEdzw4UFVa/0oVbv977JK5U E4P295B3YvMEJuIEijWhrdPacrhzS0xGY+EvLZj5KME7wNduBV/dSFCxlFjtnMvm zubNW4YQQbW4+ZCDUEUKuIR9vcdvle8cVoo+RfoXGKPu4MtfZ5Fpj8cL1wmzu3cr B3cZy2XM0RI7GhJfxXgLvFDW71Qjuxw/AYrod9hbI0rHEsXGbhF5ROjcUMzIe4VF v4FJJdYd4mqxZ6lHCdHOrkhMwL59BXFl2ANXAZZNZGi8J2cB+ZktCI7g/8w4ooTo nI7DlSrLb36Lp5N5KJoKJwmHYUpDYBeFnB62yu2xbKX4Y4QbWRQKlbuQtSTn/4iw eTLUu4zr0bHcLihRGnGumKOY2vT/9alOmAHSJfI64Acmsli06rHOiRdMY/Jc8rr7 325Ifmeuu5IkWltKvYJ4vYBIBTkis8hT2lHif2IFcFxKk4KzvhVGLhT22A2qVrO8 aafxyuWZJxRMHlPYVfzSv8JDZvvCJqZW6HeOvjW1P5efyrlPCXmB/2FYoprJL5rT uqrQ/YycIKCVBjuatau37oo2uIVAVvvmPK+ZQHoR/smrGi1JxMr7ru5haAYWZL2N 9azmaKxE5KJQVA/X1w7IsWrqS+ll4lPZ53TCcRxAljupdQdb2ry/UQ7fvViuys9L DFHCY7PmtLAnZ95M+0dC =Uke4 -----END PGP SIGNATURE----- --xQILpJsL5cebVBoz--