From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BAFBC28CC7 for ; Mon, 3 Jun 2019 09:08:44 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 05B6527137 for ; Mon, 3 Jun 2019 09:08:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05B6527137 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:60018 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hXixP-0005fY-4T for qemu-devel@archiver.kernel.org; Mon, 03 Jun 2019 05:08:43 -0400 Received: from eggs.gnu.org ([209.51.188.92]:46640) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hXivW-0004FI-Rx for qemu-devel@nongnu.org; Mon, 03 Jun 2019 05:06:48 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hXivU-00024r-J7 for qemu-devel@nongnu.org; Mon, 03 Jun 2019 05:06:46 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55984) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hXivU-00022G-8p; Mon, 03 Jun 2019 05:06:44 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1C85BC05678B; Mon, 3 Jun 2019 09:06:43 +0000 (UTC) Received: from t460s.redhat.com (unknown [10.36.117.0]) by smtp.corp.redhat.com (Postfix) with ESMTP id C57D860C7F; Mon, 3 Jun 2019 09:06:40 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Date: Mon, 3 Jun 2019 11:06:14 +0200 Message-Id: <20190603090635.10631-2-david@redhat.com> In-Reply-To: <20190603090635.10631-1-david@redhat.com> References: <20190603090635.10631-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Mon, 03 Jun 2019 09:06:43 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH v2 01/22] s390x/tcg: Store only the necessary amount of doublewords for STFLE X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Stefan Liebler , Thomas Huth , Denys Vlasenko , David Hildenbrand , Andreas Krebbel , Cornelia Huck , Richard Henderson , Pino Toscano , Christian Borntraeger , qemu-s390x@nongnu.org, Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" The PoP (z14, 7-382) says: Doublewords to the right of the doubleword in which the highest-numbered facility bit is assigned for a model may or may not be stored. However, stack protection in certain binaries can't deal with that. "gzip" example code: f1b4: a7 08 00 03 lhi %r0,3 f1b8: b2 b0 f0 a0 stfle 160(%r15) f1bc: e3 20 f0 b2 00 90 llgc %r2,178(%r15) f1c2: c0 2b 00 00 00 01 nilf %r2,1 f1c8: b2 4f 00 10 ear %r1,%a0 f1cc: b9 14 00 22 lgfr %r2,%r2 f1d0: eb 11 00 20 00 0d sllg %r1,%r1,32 f1d6: b2 4f 00 11 ear %r1,%a1 f1da: d5 07 f0 b8 10 28 clc 184(8,%r15),40(%r1) f1e0: a7 74 00 06 jne f1ec f1e4: eb ef f1 30 00 04 lmg %r14,%r15,304(%r15) f1ea: 07 fe br %r14 f1ec: c0 e5 ff ff 9d 6e brasl %r14,2cc8 <__stack_chk_fail@p= lt> In QEMU, we currently have: max_bytes =3D 24 the code asks for (3 + 1) doublewords =3D=3D 32 bytes. If we write 32 bytes instead of only 24, and return "2 + 1" doublewords ("one less than the number of doulewords needed to contain all of the facility bits"), the example code detects a stack corruption. In my opinion, the code is wrong. However, it seems to work fine on real machines. So let's limit storing to the minimum of the requested and the maximum doublewords. Cc: Stefan Liebler Cc: Andreas Krebbel Reviewed-by: Richard Henderson Signed-off-by: David Hildenbrand --- target/s390x/misc_helper.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c index 34476134a4..10aa617cf9 100644 --- a/target/s390x/misc_helper.c +++ b/target/s390x/misc_helper.c @@ -678,7 +678,13 @@ uint32_t HELPER(stfle)(CPUS390XState *env, uint64_t = addr) =20 prepare_stfl(); max_bytes =3D ROUND_UP(used_stfl_bytes, 8); - for (i =3D 0; i < count_bytes; ++i) { + + /* + * The PoP says that doublewords beyond the highest-numbered facilit= y + * bit may or may not be stored. However, existing hardware appears= to + * not store the words, and existing software depend on that. + */ + for (i =3D 0; i < MIN(count_bytes, max_bytes); ++i) { cpu_stb_data_ra(env, addr + i, stfl_bytes[i], ra); } =20 --=20 2.21.0