From owner-svn-src-head@freebsd.org Mon Aug 29 19:10:41 2016 Return-Path: Delivered-To: svn-src-head@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 1324CBC3FA5; Mon, 29 Aug 2016 19:10:41 +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 7604DC40; Mon, 29 Aug 2016 19:10:40 +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 u7TJAZSD035395 (version=TLSv1 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Mon, 29 Aug 2016 22:10:35 +0300 (EEST) (envelope-from kostikbel@gmail.com) DKIM-Filter: OpenDKIM Filter v2.10.3 kib.kiev.ua u7TJAZSD035395 Received: (from kostik@localhost) by tom.home (8.15.2/8.15.2/Submit) id u7TJAZ5j035394; Mon, 29 Aug 2016 22:10:35 +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 22:10:35 +0300 From: Konstantin Belousov To: Andrey Chernov Cc: John Baldwin , 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: <20160829191035.GV83214@kib.kiev.ua> References: <201608272303.u7RN3N0D078505@repo.freebsd.org> <1595604.93PBdSz0kX@ralph.baldwin.cx> <20160829065813.GP83214@kib.kiev.ua> <18206408.GMLM77D01s@ralph.baldwin.cx> <20160829180454.GU83214@kib.kiev.ua> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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-head@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 29 Aug 2016 19:10:41 -0000 On Mon, Aug 29, 2016 at 09:16:29PM +0300, Andrey Chernov wrote: > Previous text is documented everywhere and describing usual good > practice, so it should remains in place, in that means r304928 should be > reverted, because replace proper way of doing things with obsoleted > feature description. > > What I suggest is not _replace_ old text with new, but _add_ new text as > describing current and not recommended way, with the direct mention that > this feature is obsoleted and not recommended for relay on it. > diff --git a/lib/libc/sys/ptrace.2 b/lib/libc/sys/ptrace.2 index 48802f4..d406efc 100644 --- a/lib/libc/sys/ptrace.2 +++ b/lib/libc/sys/ptrace.2 @@ -2,7 +2,7 @@ .\" $NetBSD: ptrace.2,v 1.2 1995/02/27 12:35:37 cgd Exp $ .\" .\" This file is in the public domain. -.Dd August 28, 2016 +.Dd August 29, 2016 .Dt PTRACE 2 .Os .Sh NAME @@ -900,19 +900,29 @@ argument is ignored. .Pp Additionally, other machine-specific requests can exist. .Sh RETURN VALUES +Most requests return 0 on success and \-1 on error. Some requests can cause .Fn ptrace to return \-1 -as a non-error value; to disambiguate, +as a non-error value, among them are +.Dv PT_READ_I +and +.Dv PT_READ_D , +which return the value read from the process memory on success. +To disambiguate, .Va errno -is set to 0 in the libc wrapper for the -.Fn ptrace -system call and +can be set to 0 before the call and checked afterwards. +.Pp +Current .Fn ptrace -callers can reliably check +implementation always sets +.Va errno +to 0 before calling into kernel, both for historic reasons and for +consistency with other operating systems. +It is recommended to assign zero to .Va errno -for non-zero value afterwards. +explicitely for future compatibility. .Sh ERRORS The .Fn ptrace