From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AH8x227VvdKiw58h52rq09C402EZbsute3cQgLNKl99WtEloECdfqyCizEnkLH6zrJacnqTccm9D ARC-Seal: i=1; a=rsa-sha256; t=1517166055; cv=none; d=google.com; s=arc-20160816; b=i+/CReqmzLadikx7RcRd6PqtrDStzBJIAisrA0MkURKvmEmfxco9uKn2lipu4c3k/W aMqXhr9luQj3KcOoBLXRkWkDAxAKrUKcChto2Rr9ZFEHWiSVEGtKyaa+24k30f9cWdnZ 7vAgIypTBtfGDnIdwVnMrYbhKgHQ5Ldzlo3OWL3yHvjjbxXTppRrgOEpSJ+zEdaUeZBV Dmt1Q+ER4dEsuTTjcQeplPP7JyAVwfPFkit+ueRUzLmeq+kgL1upJ9IZyqqzmZHjJW3F Xwnld38+ttEx6GLVxqg4c9q103jsfjynDpKEEXhCdpGMsHqhgjpWNIFVf5e1Q/BI+S4b e16A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=subject:user-agent:in-reply-to:content-disposition:mime-version :references:message-id:cc:to:from:date:sender:dkim-signature :delivered-to:list-id:list-subscribe:list-unsubscribe:list-help :list-post:precedence:mailing-list:arc-authentication-results; bh=x26evswGNCIkmcwFQa81dF08a8o2kWcrKmnI2sHYSg4=; b=zMRj56xRzAB6aI5zifCFJ995q4mPHmropakQzgVa9Ih/EecpJkyzyPVHqAUmLt5KbO E2wZ7PYiEOB/48bKzFEEA97RJyookGxV/Nh2/Vsvl+YzTr0E/c6759GPay/3bMqWJX0D EBF4/uRG+5CemCrVMxvB+gXqK0+2FBhx8M2qThwNqTBYS6wGnd1QvNTgujI5VC9ATE6K 9+u4MQOqxhGm138LJYh0LvbvF0ztqpMLr0RyfsnqME6nE/m6Hs4wgSc7WUeIofwNmRVn KR89a1n9sRR+obM0wEj/SW16udz/hwARBkYVcipLTsb3Wyyt2M2C05V6NubYjnyY4j7f Qxbw== ARC-Authentication-Results: i=1; mx.google.com; dkim=fail header.i=@gmail.com header.s=20161025 header.b=nF7vpRaB; spf=pass (google.com: domain of kernel-hardening-return-11493-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-11493-gregkh=linuxfoundation.org@lists.openwall.com Authentication-Results: mx.google.com; dkim=fail header.i=@gmail.com header.s=20161025 header.b=nF7vpRaB; spf=pass (google.com: domain of kernel-hardening-return-11493-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-11493-gregkh=linuxfoundation.org@lists.openwall.com Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: Sender: Ingo Molnar Date: Sun, 28 Jan 2018 20:00:35 +0100 From: Ingo Molnar To: Andy Lutomirski Cc: x86@kernel.org, LKML , Linus Torvalds , Kernel Hardening , Borislav Petkov Message-ID: <20180128190035.q2bqchwhc2fww6io@gmail.com> References: <462dff8d4d64dfbfc851fbf3130641809d980ecd.1517164461.git.luto@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <462dff8d4d64dfbfc851fbf3130641809d980ecd.1517164461.git.luto@kernel.org> User-Agent: NeoMutt/20170609 (1.8.3) Subject: [kernel-hardening] Re: [PATCH 1/3] x86/entry/64: Remove the SYSCALL64 fast path X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1590862571103745235?= X-GMAIL-MSGID: =?utf-8?q?1590863913287218766?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: * Andy Lutomirski wrote: > The SYCALLL64 fast path was a nice, if small, optimization back in > the good old days when syscalls were actually reasonably fast. Now > we have PTI to slow everything down, and indirect branches are > verboten, making everything messier. The retpoline code in the fast > path was particularly nasty. > > Just get rid of the fast path. The slow path is barely slower. > > Signed-off-by: Andy Lutomirski > --- > > This isn't quite identical to Linus' patch. I cleaned up the > SYSCALL64 entry code to use all pushes rather than pushing all but 6 > regs and moving the rest. Hm, could we please have this in two parts please, out of general paranoia? One patch doing the easy fast path removal, the other doing the mov/push conversion? Bisectability, reviewability and all that. Exact same patch result. Thanks, Ingo