From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from phobos.denx.de (phobos.denx.de [85.214.62.61]) by sourceware.org (Postfix) with ESMTPS id D5AED3858C60 for ; Thu, 7 Oct 2021 10:00:45 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D5AED3858C60 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=denx.de Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=denx.de Received: from ktm (85-222-111-42.dynamic.chello.pl [85.222.111.42]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: lukma@denx.de) by phobos.denx.de (Postfix) with ESMTPSA id 512B7831A4; Thu, 7 Oct 2021 12:00:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=denx.de; s=phobos-20191101; t=1633600844; bh=oW5DUygpcRoYBc+N0O+M7d3Rh2w2UFAFzECB83r5LNU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=V9nsztlVpv/oCZ4coJVtag+BQETr87edUET9r7O+OU/kO7JUOBhWJf3nTvAem1/tW Oly2T+ZH4iBqNHGGMRi8p8C3XxKLcXtkZdcvsccW2C1tMqmGOi8SUXx9tXHEikUWIn IQcDJAMHyniXe1R1FkIKFimsAE2NW2kS19oHKP4JohJnIzGgq5q6aCoPhlQneP3oBH 8h22kuxbJMeWsV8CPXjCOmzu0TrCilOCxhgzt1r7ncMiW9fcAszU02DBzHSF/pu9b0 Cy9KGziTotbqDs9cYd1FNp21/hTqYmbK0+tumEX624eVacpFUc++3yWL1Yz3yp8ndt D+Fn+kjhZOAeg== Date: Thu, 7 Oct 2021 12:00:38 +0200 From: Lukasz Majewski To: Szabolcs Nagy Cc: Fangrui Song , Adhemerval Zanella , Florian Weimer , Joseph Myers , Andreas Schwab , libc-alpha Subject: Re: [PATCH] dl: Use "adr" assembler command to get proper load address Message-ID: <20211007120038.1445bbd3@ktm> In-Reply-To: <20211007111926.30db4c4f@ktm> References: <20210907131616.23472-1-lukma@denx.de> <20210907164906.yt6nonvfyhvbrx6p@google.com> <20210907193227.6047f9cc@ktm> <20210907174417.sctsswphsyae4mpc@google.com> <20211005094554.2f28d6bd@ktm> <20211006075721.qnv6qabroytcsido@google.com> <20211006110321.5f1a9610@ktm> <20211006134344.63395242@ktm> <20211006125517.GE2700@arm.com> <20211007111926.30db4c4f@ktm> Organization: denx.de X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; boundary="Sig_/zkM2rg./tumMt9rlFHF0Ob6"; protocol="application/pgp-signature" X-Virus-Scanned: clamav-milter 0.103.2 at phobos.denx.de X-Virus-Status: Clean X-Spam-Status: No, score=-2.9 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_BARRACUDACENTRAL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=no autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Oct 2021 10:00:48 -0000 --Sig_/zkM2rg./tumMt9rlFHF0Ob6 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Thu, 7 Oct 2021 11:19:26 +0200 Lukasz Majewski wrote: > Hi Szabolcs, >=20 > > The 10/06/2021 13:43, Lukasz Majewski wrote: =20 > > > Please find in-depth analyze about the issue: > > >=20 > > > It was tested with Beagle Bone Black (BBB) and QEMU (the same > > > binary rootfs images). > > > (If needed I will upload images and script to run QEMU to some > > > server for reproduction). > > > Branch: > > > https://github.com/lmajewski/y2038_glibc/commits/y2038_edge=20 > >=20 > > i think it is easier to look at if you upload the broken > > ld.so binary. or at least readelf -aW ld.so output. =20 >=20 > Please find working and broken ld-linux-armhf.so.3: > https://owncloud.denx.de/s/wtAfktG6pXLffSA >=20 > > =20 > > > On working setup to trigger the core dump: > > > /home/root/ld-linux-armhf.so.3 /sbin/init > > > gdb ./ld-linux-armhf.so.3 core > > >=20 > > > (and the /home/root/ld-linux-armhf.so.3 is the "broken" one). > > >=20 > > >=20 > > > Not working (patch [1] not applied): > > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > >=20 > > > All the code is located in _dl_start in elf/rtld.c and > > > elf/get-dynamic-info.h files: > > >=20 > > > (gdb) p/x $r5 > > > $46 =3D 0xb6fc8000 > > > r5 is set from the elf_machine_load_address() > > >=20 > > > Then we enter the elf_get_dynamic_info() > > >=20 > > > 0xb6fc95fc 99 ADJUST_DYN_INFO (DT_SYMTAB); > > > 0xb6fc95f8 <_dl_start+308>: 04 30 92 15 ldrne r3, [r2, > > > #4] =3D> 0xb6fc95fc <_dl_start+312>: 05 30 83 10 addne r3, > > > r3, r5 0xb6fc9600 <_dl_start+316>: 04 30 82 15 strne r3, > > > [r2, #4] (gdb) p/x $r3 > > > $63 =3D 0x410003f4 > > > (gdb) p/x $r5 > > > $64 =3D 0xb6fc8000 =20 > >=20 > > it seems r5 is already wrong here, it's not the runtime > > address of 0. (looks more like the runtime address of > > 0x41000000) =20 >=20 > The r5 is set according to the change in patch which now I'm trying to > fix. >=20 > To be more specific - r5 is set according to code in patch SHA1: > bca0f5cbc9257c13322b99e55235c4f21ba0bd82 >=20 > >=20 > > likely something goes wrong with the computation of r5. =20 >=20 > Before the SHA1: bca0f5cbc9257c13322b99e55235c4f21ba0bd82 patch r5 was > computed with using 'adr' assembler instruction, not set from some > constant value. >=20 > asm ("adr %0, _dl_start" : "=3Dr" (pcrel_addr)); >=20 > And r5 value was 0x75fc8000 >=20 > > =20 > > > Links: > > > [1] - > > > https://github.com/lmajewski/y2038_glibc/commit/e67e0f589b88a44be8f8b= 9b770b08950dd7e5bd5 > > >=20 > > > readelf -e ld-linux-armhf.so.3=20 > > >=20 > > > [10] .plt PROGBITS 41000994 000994 000050 04 > > > AX 0 0 4 [11] .text PROGBITS 41000a00 > > > 000a00 01fed0 00 AX 0 0 64 [12] .rodata PROGBITS > > > 410208d0 0208d0 004b24 00 A 0 0 4 [13] .ARM.extab > > > PROGBITS 410253f4 0253f4 000018 00 A 0 0 4 [14] > > > .ARM.exidx ARM_EXIDX 4102540c 02540c 0000c8 00 AL 11 > > > 0 4 [15] .data.rel.ro PROGBITS 41036200 026200 > > > 000cf4 00 WA 0 0 8 [16] .dynamic DYNAMIC > > > 41036ef4 026ef4 0000c8 08 WA 5 0 4 [17] .got > > > PROGBITS 41036fbc 026fbc 000040 04 WA 0 0 4 =20 > >=20 > > why are all addresses >0x41000000 ? > > in a shared library i expect all those addresses > > to be close to 0. =20 >=20 > On this real HW system (the rootfs which is running) - libc.so.6 also > has address > 0x41000000 > libm.so.6 also has the value > 0x41200000 > (Entry point address: 0x412c9190) >=20 > The offset of > 0x41000000 looks a bit strange indeed, but it is still > less than the kernel space. Moreover, with position independent code > it shall not matter. >=20 > >=20 > > is this made by some modified binutils? =20 >=20 > I've double checked the ld-linux-armhf.so.3 and after build it has: > (Entry point address: 0xa00) which seems to be correct. >=20 > So it looks like during installation of the glibc (on the Yocto/OE > created rootfs) the elf header is modified and this 0x41000000 offset > is added. >=20 And indeed it is the case. Yocto/OE by default perform prelinking (use prelink program) to speedup start time of dynamic program. The prelink [1] itself assigns some virtual addresses to all required shared objects (in our case for /sbin/init), so no clashes are encountered. And using prelink is a _default_ behaviour in Yocto/OE poky distro. Links: [1] - https://linux.die.net/man/8/prelink >=20 > Best regards, >=20 > Lukasz Majewski >=20 > -- >=20 > DENX Software Engineering GmbH, Managing Director: Wolfgang Denk > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany > Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: > lukma@denx.de Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de --Sig_/zkM2rg./tumMt9rlFHF0Ob6 Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEgAyFJ+N6uu6+XupJAR8vZIA0zr0FAmFexUYACgkQAR8vZIA0 zr34kAf9GmYDvwBYV0DxbIfCWnoBm6RV6uoSCHssS4JKcTYD8sR08YS4REHvlo9h 6r4KvJSRKc0Co5kedzCYCdXIdsJpLKxzMnfeeYjiulzuP4dk3vNidqMETVm7eyKP HRn6wsn9KlJKvUfLroBR9HlhDEbPv04yWUN8J8hyV1acnwzXXGHN3hfjBtFJ/OHe jNOumq35nHLQWLx2h+bc28OFT4+8H7Mho6CVUTfYIRMmxXFdElKTOpsfW5Bt0U5F BJ8f54jFCZi7y0j2yDJdJ2CjN+boinoon0bYcS5BgOa+SFIM4tBDI6piKrJ2OUu6 V3pz2V3l2tphps5d9ePXrUFJthI+tw== =iq38 -----END PGP SIGNATURE----- --Sig_/zkM2rg./tumMt9rlFHF0Ob6--