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Mon, 21 Nov 2022 07:40:32 +0000 (UTC) X-FDA: 80156651904.29.F5A8E42 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf23.hostedemail.com (Postfix) with ESMTP id C76AC140004 for ; Mon, 21 Nov 2022 07:40:31 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 66ACACE0451; Mon, 21 Nov 2022 07:40:28 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF4E3C433C1; Mon, 21 Nov 2022 07:40:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669016426; bh=ghyXIiLZQR1VJJWRY9yXFbB0NXqU+1Bza1GDza4IlCg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ON7jOHT51zmDztSDGialBKHHhuuS8etEB+bzLNnYkOPuzYN8CzSyJhiEze7ax2aBO ufY0+yMDRRomJ5SnzKhYhmsL6IFNJvTPXwuvGvC4nRehqiVkfBBVAZCHUpbyuGe7zw 8qyR42WL6O0WdCVMdC4iY4YR8BPp6OFE19ah0VVphN7mby7bqoomsRHFPmCmvPqu1I ZnoM9Oh03Xtb+zWDQzFh9M7r0kiExUA3Ljpm5yUnN42RVxbzJFiKEVzguQV+9ZzUqd kosXMOvDYZShEIMFzkfzNMn4c3HLbi7MzR91+xzo1GdrseepOOBii5ghopRFO9hEbc WaVzQsjgH6RiQ== Date: Mon, 21 Nov 2022 09:40:03 +0200 From: Mike Rapoport To: "Edgecombe, Rick P" Cc: "Schimpe, Christina" , "peterz@infradead.org" , "bsingharora@gmail.com" , "hpa@zytor.com" , "Syromiatnikov, Eugene" , "rdunlap@infradead.org" , "keescook@chromium.org" , "Yu, Yu-cheng" , "Eranian, Stephane" , "kirill.shutemov@linux.intel.com" , "dave.hansen@linux.intel.com" , "linux-mm@kvack.org" , "fweimer@redhat.com" , "nadav.amit@gmail.com" , "jannh@google.com" , "dethoma@microsoft.com" , "kcc@google.com" , "linux-arch@vger.kernel.org" , "bp@alien8.de" , "oleg@redhat.com" , "hjl.tools@gmail.com" , "Yang, Weijiang" , "Lutomirski, Andy" , "jamorris@linux.microsoft.com" , "arnd@arndb.de" , "tglx@linutronix.de" , "pavel@ucw.cz" , "mike.kravetz@oracle.com" , "x86@kernel.org" , "linux-doc@vger.kernel.org" , "john.allen@amd.com" , "mingo@redhat.com" , "Shankar, Ravi V" , "corbet@lwn.net" , "linux-kernel@vger.kernel.org" , "linux-api@vger.kernel.org" , "gorcunov@gmail.com" , "akpm@linux-foundation.org" Subject: Re: [PATCH v3 35/37] x86/cet: Add PTRACE interface for CET Message-ID: References: <20221104223604.29615-1-rick.p.edgecombe@intel.com> <20221104223604.29615-36-rick.p.edgecombe@intel.com> <223bf306716f5eb68e4f9fd660414c84cddd9886.camel@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ON7jOHT5; spf=pass (imf23.hostedemail.com: domain of rppt@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=none) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1669016432; a=rsa-sha256; cv=none; b=pl2/bJqBiKOURfaB1cqB1L18/tFv+NgFj8OiQF5kSEWim/N7CLwygICo2Uk986oxOMDHvc PzjYOXbiRr8bigckXw2Dxt20wm8XyZXaXNw6o/RwGiF2E12bFTVUfzhH+CTyaRo/to0y0p oWbSReGWeZx/x6yPtxnyBNpVnQi0FXs= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1669016432; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=O8xmrnqF5qIg2EjMtkhQkCrTH01JuJT42L0abMZ8L08=; b=ABsPXCB0pYHB2KWwOx5L5COCV16Dj512SG7ze8imTELyWlMINBk5mxpukrwIBV0NTg4S22 NKCfVcuWsENlpeqb915377jkhBmzgHCYwWRI+Eo3zwlJzgQtn4dmhRq91ujINF70Xmex+W fvLFNVWp8jO68Z6ofRacBOTx4Vc76Yk= X-Rspam-User: Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=ON7jOHT5; spf=pass (imf23.hostedemail.com: domain of rppt@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=rppt@kernel.org; dmarc=pass (policy=none) header.from=kernel.org X-Stat-Signature: hjzeui16m1rt8h7ansmpm3gf8am9xuf3 X-Rspamd-Queue-Id: C76AC140004 X-Rspamd-Server: rspam09 X-HE-Tag: 1669016431-336968 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Nov 17, 2022 at 07:57:59PM +0000, Edgecombe, Rick P wrote: > On Thu, 2022-11-17 at 12:25 +0000, Schimpe, Christina wrote: > > > Hmm, we definitely need to be able to set the SSP. Christina, does > > > GDB need > > > anything else? I thought maybe toggling SHSTK_EN? > > > > In addition to the SSP, we want to write the CET state. For instance > > for inferior calls, > > we want to reset the IBT bits. > > However, we won't write states that are disallowed by HW. > > Sorry, I should have given more background. Peter is saying we should > split the ptrace interface so that shadow stack and IBT are separate. > They would also no longer necessarily mirror the CET_U MSR format. > Instead the kernel would expose a kernel specific format that has the > needed bits of shadow stack support. And a separate one later for IBT. > > So the question is what does shadow stack need to support for ptrace > besides SSP? Is it only SSP? The other features are SHSTK_EN and > WRSS_EN. It might actually be nice to keep how these bits get flipped > more controlled (remove them from ptrace). It looks like CRIU didn't > need them. CRIU reads CET_U with ptrace(PTRACE_GETREGSET, NT_X86_CET). It's done before the injection of the parasite. The value of SHSTK_EN is used then to detect if shadow stack is enabled and to setup victim's shadow stack for sigreturn. -- Sincerely yours, Mike.