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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 5AFF6C433E0 for ; Tue, 9 Jun 2020 00:38:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F990206C3 for ; Tue, 9 Jun 2020 00:38:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731520AbgFIAic (ORCPT ); Mon, 8 Jun 2020 20:38:32 -0400 Received: from mga12.intel.com ([192.55.52.136]:64028 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729217AbgFIAh6 (ORCPT ); Mon, 8 Jun 2020 20:37:58 -0400 IronPort-SDR: H1Hmc7MDwOZ2/hkuXqqvRN5Wmqh1tPw+Flcx/7GrdEUrXToCau0M1eWgGkx7VEyRZzal71oLfD xE4MtXMIUg6g== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Jun 2020 17:37:58 -0700 IronPort-SDR: p2oalkKzEMvdouJNti5J7BEPx5+c7jbkBE4nwQ9ipUiDR01a+CT8w1l0g7rz8F2ZaJhyJUfyMs 55AqaSuuyXzA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,489,1583222400"; d="scan'208";a="472894832" Received: from ranerica-svr.sc.intel.com ([172.25.110.23]) by fmsmga005.fm.intel.com with ESMTP; 08 Jun 2020 17:37:58 -0700 Date: Mon, 8 Jun 2020 17:38:12 -0700 From: Ricardo Neri To: Brendan Shanks Cc: linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, ebiederm@xmission.com, andi@notmuch.email, Babu.Moger@amd.com Subject: Re: [PATCH v3] x86/umip: Add emulation/spoofing for SLDT and STR instructions Message-ID: <20200609003812.GA26268@ranerica-svr.sc.intel.com> References: <20200608224424.7259-1-bshanks@codeweavers.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200608224424.7259-1-bshanks@codeweavers.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 08, 2020 at 03:44:24PM -0700, Brendan Shanks wrote: > Add emulation/spoofing of SLDT and STR for both 32- and 64-bit > processes. > > Wine users have found a small number of Windows apps using SLDT that > were crashing when run on UMIP-enabled systems. > > Reported-by: Andreas Rammhold > Originally-by: Ricardo Neri > Signed-off-by: Brendan Shanks > --- > > v3: Use (GDT_ENTRY_TSS * 8) for task register selector instead of > harcoding 0x40. > > arch/x86/kernel/umip.c | 32 +++++++++++++++++++++++--------- > 1 file changed, 23 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c > index 8d5cbe1bbb3b..166c579b0273 100644 > --- a/arch/x86/kernel/umip.c > +++ b/arch/x86/kernel/umip.c > @@ -244,16 +244,35 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst, > *data_size += UMIP_GDT_IDT_LIMIT_SIZE; > memcpy(data, &dummy_limit, UMIP_GDT_IDT_LIMIT_SIZE); > > - } else if (umip_inst == UMIP_INST_SMSW) { > - unsigned long dummy_value = CR0_STATE; > + } else if (umip_inst == UMIP_INST_SMSW || umip_inst == UMIP_INST_SLDT || > + umip_inst == UMIP_INST_STR) { > + unsigned long dummy_value; > + > + if (umip_inst == UMIP_INST_SMSW) > + dummy_value = CR0_STATE; > + else if (umip_inst == UMIP_INST_STR) > + dummy_value = GDT_ENTRY_TSS * 8; > + else if (umip_inst == UMIP_INST_SLDT) > + { This brace should go in the previous line. Also, if you use braces in the last part of the conditional you should probably use them in the previous ones. I guess in this case it woudln't improve readability. Instead, you can probably have a switch instead of the three ifs. That probably does improve readability and solves the dilemma of needing to put braces in all the one-line conditionals. BTW, you should also delete the comment at the top of the file saying that str and sldt will not be emulated: diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c index 166c579b0273..0984a55eb8c0 100644 --- a/arch/x86/kernel/umip.c +++ b/arch/x86/kernel/umip.c @@ -45,9 +45,6 @@ * value that, lies close to the top of the kernel memory. The limit for the GDT * and the IDT are set to zero. * - * Given that SLDT and STR are not commonly used in programs that run on WineHQ - * or DOSEMU2, they are not emulated. - * * The instruction smsw is emulated to return the value that the register CR0 * has at boot time as set in the head_32. * Thanks and BR, Ricardo