From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 15432 invoked by alias); 3 Mar 2018 17:45:46 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Received: (qmail 128164 invoked by uid 89); 3 Mar 2018 17:45:33 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.5 required=5.0 tests=AWL,BAYES_00,SPF_PASS autolearn=ham version=3.3.2 spammy=charge X-HELO: 9pmail.ess.barracuda.com Received: from 9pmail.ess.barracuda.com (HELO 9pmail.ess.barracuda.com) (64.235.154.210) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sat, 03 Mar 2018 17:45:32 +0000 Received: from MIPSMAIL01.mipstec.com (mailrelay.mips.com [12.201.5.28]) by mx1412.ess.rzc.cudaops.com (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NO); Sat, 03 Mar 2018 17:45:22 +0000 Received: from [10.20.78.175] (10.20.78.175) by mips01.mipstec.com (10.20.43.31) with Microsoft SMTP Server id 14.3.361.1; Sat, 3 Mar 2018 09:42:58 -0800 Date: Sat, 03 Mar 2018 17:45:00 -0000 From: "Maciej W. Rozycki" To: John Baldwin CC: Subject: Re: [PATCH] Workaround a FreeBSD ptrace() bug with clearing thread events. In-Reply-To: <2023036.DDCG60uWOK@ralph.baldwin.cx> Message-ID: References: <20180224000935.43344-1-jhb@FreeBSD.org> <1908872.BAzsX71dkG@ralph.baldwin.cx> <2023036.DDCG60uWOK@ralph.baldwin.cx> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-BESS-ID: 1520099121-452060-9089-103336-14 X-BESS-VER: 2018.2.1-r1802232342 X-BESS-Apparent-Source-IP: 12.201.5.28 X-BESS-Outbound-Spam-Score: 0.00 X-BESS-Outbound-Spam-Report: Code version 3.2, rules version 3.2.2.190638 Rule breakdown below pts rule name description ---- ---------------------- -------------------------------- 0.00 BSF_BESS_OUTBOUND META: BESS Outbound X-BESS-Outbound-Spam-Status: SCORE=0.00 using account:ESS59374 scores of KILL_LEVEL=7.0 tests=BSF_BESS_OUTBOUND X-BESS-BRTS-Status:1 X-SW-Source: 2018-03/txt/msg00093.txt.bz2 On Fri, 2 Mar 2018, John Baldwin wrote: > > Is the one-way compatibility enforced though, by a system library runtime > > or the kernel somehow, by refusing to run a binary built for a kernel that > > is newer than one currently in charge of the system? Otherwise the rule > > would be quite fragile and error prone, asking for extra care to be taken > > by the user. > > It is enforced in some ways but not others. Kernel modules do depend on a > version number in such a way that attempting to load a newer kernel module > on an older kernel will fail. However, the general policy of only supporting > one-way compatibility is well-known among the FreeBSD userbase (for example, > the instructions for upgrading a system from source require booting into a > new kernel before installing the matching userland binaries). That all sounds right, however does not really address my concern where a user *unknowingly* tries a program binary that has been compiled for a newer kernel version and then faces all kinds of issues. This is bound to happen sooner or later for someone, the Murphy's law guarantees it. Maciej