From nobody Mon Feb 9 09:34:28 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) client-ip=192.237.175.120; envelope-from=xen-devel-bounces@lists.xenproject.org; helo=lists.xenproject.org; Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=fail(p=none dis=none) header.from=citrix.com ARC-Seal: i=1; a=rsa-sha256; t=1590607188; cv=none; d=zohomail.com; s=zohoarc; b=Ozg9wdKgEydIXJo/3laaAJPfxFY3GfyuXMwGLLh6aAXIAoXzybyFW1DJzdLLzLNjpDP/Hq+UBRQ1A7Uh0ZvIR2GETpR6GBqhJn7C7lberjFE7HmrVlHqqtkc23UDDb+6lMlMe66IfrsjQlEpP6IfSiYpEBFZ0lYpftYeWeEmuus= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1590607188; h=Content-Type:Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=T/43hH0vDU3tZXHq/Ub/txHYfKhHD/STKXiu10HJcJU=; b=BtlYtOCUZ1GPXGmoCLfNYTerexfcBtPGlYrWILa6/X1JNoj2J5yGSSrsaHFsPx4HbdEm1NGkajC90tc5JWFfewWeHucsM/gCfGOnky2W0zSauNEr5s04JcYgwShIluDuRYbrAV5cJwUNTSOqXtsv68AI9QbHnqos2GuFhTtyLSM= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=pass (zohomail.com: domain of lists.xenproject.org designates 192.237.175.120 as permitted sender) smtp.mailfrom=xen-devel-bounces@lists.xenproject.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) by mx.zohomail.com with SMTPS id 1590607188925950.3224487904511; Wed, 27 May 2020 12:19:48 -0700 (PDT) Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1je1aH-00042G-DG; Wed, 27 May 2020 19:19:25 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1je1aF-00041n-QK for xen-devel@lists.xenproject.org; Wed, 27 May 2020 19:19:23 +0000 Received: from esa5.hc3370-68.iphmx.com (unknown [216.71.155.168]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id f33f80e4-a04e-11ea-81bc-bc764e2007e4; Wed, 27 May 2020 19:19:13 +0000 (UTC) X-Inumbo-ID: f33f80e4-a04e-11ea-81bc-bc764e2007e4 Authentication-Results: esa5.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: Tq6+s3Zh7QaRK595E15ZFckIpIk5gndEZuDz8ttfd0qmFsoM1hkOEjbDpJmnafihXdS2HWfRcK QVkAVn3Rogew9UeKYWAH/IlD37FBiRZJR2anYYwrexQOk8+W6IdikgmgQ91IBXK3pEfLaP1DAM N6gd/Mt3pHXf98aiI/OYkIiMcPVmOwN4qrs210s1yoSsDlLfidrAwIRjL7qHSPnlzZBL0xbvuQ 67mO7Yp3pPLaQirrO8TluPLa7vsdyPssxO/H6VF+3sCQfFEywaUHox0NAOzp6g/8KgpVgvw+RP Q7A= X-SBRS: 2.7 X-MesageID: 18850558 X-Ironport-Server: esa5.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.73,442,1583211600"; d="scan'208";a="18850558" From: Andrew Cooper To: Xen-devel Subject: [PATCH v2 07/14] x86/cpu: Adjust enable_nmis() to be shadow stack compatible Date: Wed, 27 May 2020 20:18:40 +0100 Message-ID: <20200527191847.17207-8-andrew.cooper3@citrix.com> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20200527191847.17207-1-andrew.cooper3@citrix.com> References: <20200527191847.17207-1-andrew.cooper3@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Andrew Cooper , Wei Liu , Jan Beulich , =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" When executing an IRET-to-self, the shadow stack must agree with the regular stack. We can't manipulate SSP directly, so have to fake a shadow IRET fra= me by executing 3 CALLs, then editing the result to look correct. This is not a fastpath, is called on the BSP long before CET can be set up, and may be called on the crash path after CET is disabled. Use the fact th= at INCSSP is allocated from the hint nop space to construct a test for CET bei= ng active which is safe on all processors. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich --- CC: Jan Beulich CC: Wei Liu CC: Roger Pau Monn=C3=A9 --- xen/include/asm-x86/processor.h | 43 +++++++++++++++++++++++++++++++------= ---- 1 file changed, 33 insertions(+), 10 deletions(-) diff --git a/xen/include/asm-x86/processor.h b/xen/include/asm-x86/processo= r.h index 859bd9e2ec..badd7e60e5 100644 --- a/xen/include/asm-x86/processor.h +++ b/xen/include/asm-x86/processor.h @@ -545,17 +545,40 @@ static inline void enable_nmis(void) { unsigned long tmp; =20 - asm volatile ( "mov %%rsp, %[tmp] \n\t" - "push %[ss] \n\t" - "push %[tmp] \n\t" - "pushf \n\t" - "push %[cs] \n\t" - "lea 1f(%%rip), %[tmp] \n\t" - "push %[tmp] \n\t" - "iretq; 1: \n\t" - : [tmp] "=3D&r" (tmp) + asm volatile ( "mov %%rsp, %[rsp] \n\t" + "lea .Ldone(%%rip), %[rip] \n\t" +#ifdef CONFIG_XEN_SHSTK + /* Check for CET-SS being active. */ + "mov $1, %k[ssp] \n\t" + "rdsspq %[ssp] \n\t" + "cmp $1, %k[ssp] \n\t" + "je .Lshstk_done \n\t" + + /* Push 3 words on the shadow stack */ + ".rept 3 \n\t" + "call 1f; nop; 1: \n\t" + ".endr \n\t" + + /* Fixup to be an IRET shadow stack frame */ + "wrssq %q[cs], -1*8(%[ssp]) \n\t" + "wrssq %[rip], -2*8(%[ssp]) \n\t" + "wrssq %[ssp], -3*8(%[ssp]) \n\t" + + ".Lshstk_done:" +#endif + /* Write an IRET regular frame */ + "push %[ss] \n\t" + "push %[rsp] \n\t" + "pushf \n\t" + "push %q[cs] \n\t" + "push %[rip] \n\t" + "iretq \n\t" + ".Ldone: \n\t" + : [rip] "=3D&r" (tmp), + [rsp] "=3D&r" (tmp), + [ssp] "=3D&r" (tmp) : [ss] "i" (__HYPERVISOR_DS), - [cs] "i" (__HYPERVISOR_CS) ); + [cs] "r" (__HYPERVISOR_CS) ); } =20 void sysenter_entry(void); --=20 2.11.0