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, URIBL_BLOCKED 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 1E190C28CC5 for ; Wed, 5 Jun 2019 20:39:22 +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 EB7E72067C for ; Wed, 5 Jun 2019 20:39:21 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB7E72067C 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]:49528 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hYcgr-0006nW-3u for qemu-devel@archiver.kernel.org; Wed, 05 Jun 2019 16:39:21 -0400 Received: from eggs.gnu.org ([209.51.188.92]:40964) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hYccG-0002mn-Eh for qemu-devel@nongnu.org; Wed, 05 Jun 2019 16:34:37 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hYccD-0006Hc-OV for qemu-devel@nongnu.org; Wed, 05 Jun 2019 16:34:35 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42042) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hYccB-00068m-Al; Wed, 05 Jun 2019 16:34:32 -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 DD1723082131; Wed, 5 Jun 2019 20:34:27 +0000 (UTC) Received: from t460s.redhat.com (ovpn-116-124.ams2.redhat.com [10.36.116.124]) by smtp.corp.redhat.com (Postfix) with ESMTP id 121C9619A9; Wed, 5 Jun 2019 20:34:25 +0000 (UTC) From: David Hildenbrand To: qemu-devel@nongnu.org Date: Wed, 5 Jun 2019 22:33:39 +0200 Message-Id: <20190605203403.29461-10-david@redhat.com> In-Reply-To: <20190605203403.29461-1-david@redhat.com> References: <20190605203403.29461-1-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 [10.5.110.42]); Wed, 05 Jun 2019 20:34:27 +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] [PULL SUBSYSTEM s390x 09/33] 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 , David Hildenbrand , Andreas Krebbel , Cornelia Huck , Richard Henderson , 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