From owner-svn-src-all@freebsd.org Mon Aug 29 06:58:19 2016 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 53DBFBC762A; Mon, 29 Aug 2016 06:58:19 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from kib.kiev.ua (kib.kiev.ua [IPv6:2001:470:d5e7:1::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id DFC6939F; Mon, 29 Aug 2016 06:58:18 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from tom.home (kib@localhost [127.0.0.1]) by kib.kiev.ua (8.15.2/8.15.2) with ESMTPS id u7T6wDSL054674 (version=TLSv1 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Mon, 29 Aug 2016 09:58:14 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua u7T6wDSL054674 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id u7T6wD7b054673; Mon, 29 Aug 2016 09:58:13 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: tom.home: kostik set sender to kostikbel@gmail.com using -f Date: Mon, 29 Aug 2016 09:58:13 +0300 From: Konstantin Belousov To: John Baldwin Cc: Andrey Chernov , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r304928 - in head/lib/libc: amd64/sys i386/sys sys Message-ID: <20160829065813.GP83214@kib.kiev.ua> References: <201608272303.u7RN3N0D078505@repo.freebsd.org> <80ad9e03-74bc-8c99-666f-787772bef2b9@freebsd.org> <20160828015210.GI83214@kib.kiev.ua> <1595604.93PBdSz0kX@ralph.baldwin.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1595604.93PBdSz0kX@ralph.baldwin.cx> User-Agent: Mutt/1.6.1 (2016-04-27) X-Spam-Status: No, score=-2.0 required=5.0 tests=ALL_TRUSTED,BAYES_00, DKIM_ADSP_CUSTOM_MED,FREEMAIL_FROM,NML_ADSP_CUSTOM_MED autolearn=no autolearn_force=no version=3.4.1 X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on tom.home X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.22 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: Mon, 29 Aug 2016 06:58:19 -0000 On Sun, Aug 28, 2016 at 04:09:51PM -0700, John Baldwin wrote: > OTOH, given that we explicitly documented it as not being true, I suspect > any applications that are using ptrace() are going off the documentation, not > the implementation artifact. Note that Linux's ptrace() documents the same > requirement as before this change (caller is required to clear errno), so I > doubt there is any actual software out there that expects the > FreeBSD-specific behavior. Given that and the extra maintenance overhead of > having to dink with errno in assembly on X architectures, I'd rather we keep > the old language in the manpage and remove the 'errno' frobbing in the system > call wrappers. To be honest, my first response to this commit was one of > surprise that we modify errno directly as that is inconsistent with other > system calls. (I haven't looked to see if any other system call wrappers > modify errno for non-error cases.) The problematic calls are PT_PEEK_I and PT_PEEK_D, as far as I understand. I dug into the ptrace(2) consumers, I found a lot of things using it which I would not expect to use, besides usual suspects of gdb lldb libunwind reptyr etc. Most surprising was that even high-profile consumers including gdb sometimes fail to check errno after PT_PEEK. On the other hand, I did not found a case in gdb where errno is checked after PT_PEEK but not zeroed before the syscall. I almost agreed with you after the reading, but then I decided to look into glibc just in case. What I found there is really fascinating. >From glibc/sysdeps/unix/sysv/linux: res = INLINE_SYSCALL (ptrace, 4, request, pid, addr, data); if (res >= 0 && request > 0 && request < 4) { __set_errno (0); return ret; } #define PTRACE_PEEKTEXT 1 #define PTRACE_PEEKDATA 2 #define PTRACE_PEEKUSR 3 In the end, I might consider changing the ptrace wrappers into consolidated C source, it would look like that int ptrace(int request, pid_t pid, caddr_t addr, int data) { errno = 0; return (__sys_ptrace(request, pid, addr, data)); }