From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 121136 invoked by alias); 22 Feb 2016 22:50:05 -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 121111 invoked by uid 89); 22 Feb 2016 22:50:04 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.8 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy= X-HELO: relay1.mentorg.com Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Mon, 22 Feb 2016 22:50:03 +0000 Received: from svr-orw-fem-02x.mgc.mentorg.com ([147.34.96.206] helo=SVR-ORW-FEM-02.mgc.mentorg.com) by relay1.mentorg.com with esmtp id 1aXzIm-0001Fo-NH from Luis_Gustavo@mentor.com ; Mon, 22 Feb 2016 14:50:00 -0800 Received: from [172.30.1.130] (147.34.91.1) by svr-orw-fem-02.mgc.mentorg.com (147.34.96.168) with Microsoft SMTP Server id 14.3.224.2; Mon, 22 Feb 2016 14:50:00 -0800 Subject: Re: [PATCH v2] Fix logic in exec_file_locate_attach References: <20160219102447.GA29870@blade.nx> <1455880879-310-1-git-send-email-gbenson@redhat.com> <56C736ED.9040505@codesourcery.com> <20160222104034.GA31531@blade.nx> <56CAF2E3.7050607@codesourcery.com> <20160222135109.GA2256@blade.nx> <56CB8506.3010602@codesourcery.com> To: Gary Benson CC: , Pedro Alves Reply-To: Luis Machado From: Luis Machado Message-ID: <56CB9095.9090908@codesourcery.com> Date: Mon, 22 Feb 2016 22:50:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <56CB8506.3010602@codesourcery.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-02/txt/msg00670.txt.bz2 On 02/22/2016 07:00 PM, Luis Machado wrote: > On 02/22/2016 10:51 AM, Gary Benson wrote: >> Luis Machado wrote: >>> On 02/22/2016 07:40 AM, Gary Benson wrote: >>>> Luis Machado wrote: >>>>> On 02/19/2016 09:21 AM, Gary Benson wrote: >>>>>> This is an updated version of the patch I posted yesterday. >>>>>> It fails silently rather than throwing if the executable is >>>>>> not in the sysroot, which both fixes the sysroot-escape issue >>>>>> and results in a better GDB session for the user. >>>>>> >>>>>> Built and regtested on RHEL 6.6 x86_64. >>>>>> >>>>>> Luis, I think this patch will fix your connection drop without >>>>>> any further changes. Could you test it please? >>>>> >>>>> Unfortunately it doesn't completely solve the problem i saw, as >>>>> exec_file_find will still potentially throw errors and will >>>>> disrupt the connection attempt or stop execution of a custom >>>>> sequence of commands (as Pedro noted) when "attach" is part of >>>>> the sequence. >>>>> >>>>> define foo >>>>> attach >>>>>>>>> execution stops here if an error is thrown >>>>> info threads >>>>> info registers >>>>> end >>>>> >>>>> It still looks like a TRY/CATCH block is needed around at least >>>>> exec_file_find. >>>> >>>> What is throwing in exec_file_find? I'm just seeing lots of calls >>>> to gdb_open_cloexec and openp, and I don't think either of those >>>> should throw except for assertion failures or running out of >>>> memory. >>> >>> Not sure why i had exec_file_find in my mind. I meant to say >>> exec_file_attach still throws errors, when openp fails and >>> scratch_chan < 0. Sorry. >> >> You shouldn't get that now, the "if (full_exec_path == NULL) return" >> should have caught it. Are you still seeing thrown errors with your >> setup? >> > > Yes. With your patch applied, i still see a case where we error out. > Suppose we have a test binary gdb/test, then: > > - chmod -r gdb/test > - Fire up gdbserver with a test binary: ./gdb/gdbserver/gdbserver :2345 > gdb/test > - Fire up GDB: ./gdb/gdb -ex "set sysroot" -ex "tar rem :2345" > > You will see something similar to the following: > > Sending packet: $qXfer:exec-file:read:3486:0,fff#5f...Packet received: > l/proc/13446/exe > /proc/13446/exe: Permission denied. > (gdb) i r > The program has no registers now. > (gdb) > > This was the testcase suggested by Pedro and it proved to be a good one. > >>> There is a symbol_file_add_main call right after calling >>> exec_file_attach in exec_file_locate_attach, but i didn't see any >>> errors being thrown from that one. >> >> You could probably race it (e.g. by deleting the file between the >> calls) but generally symbol_file_add_main won't fail because >> exec_file_attach would have failed if the file was missing or >> inaccessible. > > My idea was to guard both exec_file_attach and symbol_file_add_main. We > can't have anything in that function throwing an error that won't be > caught, otherwise the above connection attempt will fail. > > Luis > For the record, you patch does fix the case of native GDB trying to attach to a process without pre-loading a symbol file. We get a multi-frame backtrace as expected. It is the gdb/gdbserver case that still seems to be broken.