From owner-svn-src-all@freebsd.org Wed Jan 17 23:09:03 2018 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E2330EBE3C7; Wed, 17 Jan 2018 23:09:03 +0000 (UTC) (envelope-from glebius@FreeBSD.org) Received: from cell.glebi.us (glebi.us [96.95.210.25]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "cell.glebi.us", Issuer "cell.glebi.us" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 3366F3E31; Wed, 17 Jan 2018 23:09:03 +0000 (UTC) (envelope-from glebius@FreeBSD.org) Received: from cell.glebi.us (localhost [127.0.0.1]) by cell.glebi.us (8.15.2/8.15.2) with ESMTPS id w0HN92fo017291 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 17 Jan 2018 15:09:02 -0800 (PST) (envelope-from glebius@FreeBSD.org) Received: (from glebius@localhost) by cell.glebi.us (8.15.2/8.15.2/Submit) id w0HN92s7017290; Wed, 17 Jan 2018 15:09:02 -0800 (PST) (envelope-from glebius@FreeBSD.org) X-Authentication-Warning: cell.glebi.us: glebius set sender to glebius@FreeBSD.org using -f Date: Wed, 17 Jan 2018 15:09:02 -0800 From: Gleb Smirnoff To: Colin Percival Cc: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r327423 - in head/sys: kern sys Message-ID: <20180117230902.GP8113@FreeBSD.org> References: <201712310921.vBV9L133042419@repo.freebsd.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201712310921.vBV9L133042419@repo.freebsd.org> User-Agent: Mutt/1.9.1 (2017-09-22) X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.25 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 17 Jan 2018 23:09:04 -0000 Hi Colin, On Sun, Dec 31, 2017 at 09:21:01AM +0000, Colin Percival wrote: C> Author: cperciva C> Date: Sun Dec 31 09:21:01 2017 C> New Revision: 327423 C> URL: https://svnweb.freebsd.org/changeset/base/327423 C> C> Log: C> Code for recording timestamps of events, especially function entries/exits. C> This is a very primitive system, intended for use in measuring performance C> during the early system boot, before more sophisticated tools like DTrace C> or infrastructure like kernel memory allocation and mutexes are available. C> C> Because this code records pointers to strings rather than copying strings C> (in order to keep the memory usage more manageable), if a kernel module is C> unloaded after logging an event, Bad Things can happen. Users are advised C> to not do that. C> C> Since cycle counts from the early kernel boot are used as an initial entropy C> source, publishing this information to userland could result in inadequate C> entropy being kept private to the kernel RNG. Users are advised to not C> enable this on systems with untrusted users. C> C> Discussed on: freebsd-current Sorry if my question is too lame and late. Why can't you use ktr(4) tracer for that purpose? The discussion on freebsd-current also doesn't have answer. -- Gleb Smirnoff