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 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0447DC433F5 for ; Sun, 6 Feb 2022 13:06:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 293556B0071; Sun, 6 Feb 2022 08:06:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 2407F6B0072; Sun, 6 Feb 2022 08:06:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 108D56B0073; Sun, 6 Feb 2022 08:06:58 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0119.hostedemail.com [216.40.44.119]) by kanga.kvack.org (Postfix) with ESMTP id 02A266B0071 for ; Sun, 6 Feb 2022 08:06:57 -0500 (EST) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 8BC0C8249980 for ; Sun, 6 Feb 2022 13:06:57 +0000 (UTC) X-FDA: 79112380074.18.D3E2DC4 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf12.hostedemail.com (Postfix) with ESMTP id 9F9FD40009 for ; Sun, 6 Feb 2022 13:06:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=O8zLbKs0X6TzxCrkjzqNkkHxAtjp2s1Oq6J6b6ynu0s=; b=WKUHYTCuz+4dtYW+6BDGdx6lbC 0OaQRA0ahdl6KWql9CtBckg55JkExEGI6yC3AH+pABNOGdgo2xCRAkXTUuw6D5KJOSqO3DYWCwul1 xyAotHf2CFbX/epQDuVxq/xDN/YIeGMNrXzAjlWDAZdeKM0nn7Pz5YVu28TI99yt4enCBvej6V4XV exkbj3EiBnKPAohE+dXpik1wBFbPp/PobtG8O3Hu45F6ZT6RMPeWL/3MrfgbWaSIk+usJ0OclAN2R zD4HC7KAj/Q7dlVumDLpRoVkqF81juNEszXWFeoryjlDzKBXTV7TgHWjiYpinUiaNfh4Cy9Gj4gD4 lkGuu/TA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nGhFH-00E7rV-11; Sun, 06 Feb 2022 13:06:24 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 245F8300470; Sun, 6 Feb 2022 14:06:19 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id D86F32CA50E07; Sun, 6 Feb 2022 14:06:19 +0100 (CET) Date: Sun, 6 Feb 2022 14:06:19 +0100 From: Peter Zijlstra To: "Edgecombe, Rick P" Cc: "bsingharora@gmail.com" , "hpa@zytor.com" , "Syromiatnikov, Eugene" , "rdunlap@infradead.org" , "keescook@chromium.org" , "dave.hansen@linux.intel.com" , "kirill.shutemov@linux.intel.com" , "Eranian, Stephane" , "linux-mm@kvack.org" , "fweimer@redhat.com" , "nadav.amit@gmail.com" , "jannh@google.com" , "linux-arch@vger.kernel.org" , "kcc@google.com" , "bp@alien8.de" , "oleg@redhat.com" , "hjl.tools@gmail.com" , "Yang, Weijiang" , "Lutomirski, Andy" , "pavel@ucw.cz" , "arnd@arndb.de" , "Moreira, Joao" , "tglx@linutronix.de" , "mike.kravetz@oracle.com" , "x86@kernel.org" , "linux-doc@vger.kernel.org" , "Dave.Martin@arm.com" , "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" Subject: Re: [PATCH 00/35] Shadow stacks for userspace Message-ID: References: <87fsozek0j.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 9F9FD40009 X-Rspam-User: nil Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=WKUHYTCu; dmarc=none; spf=none (imf12.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org X-Stat-Signature: 8zpfsoxz5fm4u7u6tbwf3h17ewfsnhsm X-Rspamd-Server: rspam08 X-HE-Tag: 1644152816-445664 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 Fri, Feb 04, 2022 at 01:08:25AM +0000, Edgecombe, Rick P wrote: > > So how is that going to work? altstack is not an esoteric corner > > case. > > My understanding is that the main usages for the signal stack were > handling stack overflows and corruption. Since the shadow stack only > contains return addresses rather than large stack allocations, and is > not generally writable or pivotable, I thought there was a good > possibility an alt shadow stack would not end up being especially > useful. Does it seem like reasonable guesswork? altstacks are also used in userspace threading implemenations.