X-Recipient: archive-cygwin AT delorie DOT com X-SWARE-Spam-Status: No, hits=-1.3 required=5.0 tests=AWL,BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS X-Spam-Check-By: sourceware.org To: cygwin AT cygwin DOT com From: Andrew DeFaria Subject: Re: /proc/*/cmdline corrupted Date: Sun, 16 Oct 2011 16:59:06 -0700 Lines: 47 Message-ID: References: <32663265 DOT post AT talk DOT nabble DOT com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110923 Thunderbird/7.0 In-Reply-To: <32663265.post@talk.nabble.com> X-Stationery: 0.7.5 X-IsSubscribed: yes Mailing-List: contact cygwin-help AT cygwin DOT com; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner AT cygwin DOT com Mail-Followup-To: cygwin AT cygwin DOT com Delivered-To: mailing list cygwin AT cygwin DOT com On 10/16/11 14:31, jan.kolar wrote: >> jc807j 2668 1 0 08:59 tty0 00:00:00 xterm -e ssh server > 80x72+285+0 -e ssh server >> jc807j 3004 1 0 08:59 tty0 00:00:00 xterm -e ssh server >> 80x72-8+0 -e ssh server >> jc807j 2928 5852 0 09:12 ? 00:00:00 xterm 20000 +tb >> The actual command lines for the 3 xterm processes are: >> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72+285+0 -e ssh server >> C:\cygwin\bin\xterm.exe -sl 20000 +tb -geometry 80x72-8+0 -e ssh server >> C:\cygwin\bin\xterm.exe -sl 20000 +tb > xterm calls XrmParseCommand() that > "parses an (argc, argv) pair according to the specified option table ... and > modifies the (argc, argv) pair to remove all recognized options." > > Therefore > "-sl 20000 +tb -geometry 80x72+285+0" > is properly removed > and "-e ssh server" is moved to __argv[1 .. 3]. > Then __argv[4] (respectively __argv[1] for the shorter command) is assigned > null pointer > which results in the second "\0" in the od-output below. > > > HOWEVER: > > Either XrmParseCommand() does not update argc > or the change does not propagate (how would that be possible?) to __argc. > Therefore the command lines appear corrupted this particular way. > > > /proc/*/cmdline uses a copy of __argc named __argc_safe > which is hardly to be updated anyway. > " for (int i = 0; i< __argc_safe; i++) " > > Funny enough, /proc/self/cmdline is likely to contain shortened version of > cmdline: > " for (char **a = __argv; *a; a++)" > [ pinfo.cc from cygwin 1.7.9-1 ] Why wouldn't exec(1) be responsible for setting up /proc and therefore fill in cmdline with effectively $0 *before* the program itself ever got around to calling XrmParseCommand? (I'm not well versed in the underlying mechanics here and I have not reviewed the code but I would have thought that something like exec would have examined argv/argc before the program was ever able to modify it). -- Andrew DeFaria Chastity is curable if detected early. -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple