From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 12723 invoked by alias); 20 Jun 2013 12:26:10 -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 12714 invoked by uid 89); 20 Jun 2013 12:26:09 -0000 X-Spam-SWARE-Status: No, score=-4.2 required=5.0 tests=AWL,BAYES_00,KHOP_RCVD_UNTRUST,KHOP_THREADED,MISSING_HEADERS,RCVD_IN_HOSTKARMA_W,RCVD_IN_HOSTKARMA_WL,TW_RG autolearn=no version=3.3.1 Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.84/v0.84-167-ge50287c) with ESMTP; Thu, 20 Jun 2013 12:26:08 +0000 Received: from svr-orw-fem-01.mgc.mentorg.com ([147.34.98.93]) by relay1.mentorg.com with esmtp id 1UpdwD-0005P3-MW from Luis_Gustavo@mentor.com ; Thu, 20 Jun 2013 05:26:05 -0700 Received: from NA1-MAIL.mgc.mentorg.com ([147.34.98.181]) by svr-orw-fem-01.mgc.mentorg.com with Microsoft SMTPSVC(6.0.3790.4675); Thu, 20 Jun 2013 05:26:05 -0700 Received: from [172.30.14.165] ([172.30.14.165]) by NA1-MAIL.mgc.mentorg.com with Microsoft SMTPSVC(6.0.3790.3959); Thu, 20 Jun 2013 05:26:04 -0700 Message-ID: <51C2F4D7.1050802@codesourcery.com> Date: Thu, 20 Jun 2013 13:39:00 -0000 From: Luis Machado Reply-To: lgustavo@codesourcery.com User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130329 Thunderbird/17.0.5 MIME-Version: 1.0 CC: Pedro Alves , "'gdb-patches@sourceware.org'" , Mike Frysinger Subject: Re: [PATCH, gdbsim] Avoid silly crash when no binary is loaded References: <51C0C7E3.1030603@codesourcery.com> <51C193AE.7010608@redhat.com> <51C19FF0.8000005@codesourcery.com> <51C1BBE4.5080107@redhat.com> <51C1CB26.2070602@codesourcery.com> In-Reply-To: <51C1CB26.2070602@codesourcery.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2013-06/txt/msg00534.txt.bz2 Thought it would be best to cc Mike. On 06/19/2013 12:15 PM, Luis Machado wrote: > On 06/19/2013 11:10 AM, Pedro Alves wrote: >> On 06/19/2013 01:11 PM, Luis Machado wrote: >>> Hi, >>> >>> On 06/19/2013 08:19 AM, Pedro Alves wrote: >>>> On 06/18/2013 09:49 PM, Luis Machado wrote: >>>>> Hi, >>>>> >>>>> This patch prevents the long-standing crash scenario where we start >>>>> gdbsim and "run" without any binaries. Warnings are issued, but those >>>>> don't prevent the simulator from proceeding with garbage data. >>>> >>>> Which sim and backtrace? I suspect this to be sim/arch dependent. >>> >>> This is arm. Other simulators (mips and powerpc) have different >>> behaviors. No crashes, but they go all over the place in terms of >>> messages. >>> >>> I'm questioning the use case of attempting to let the simulator go >>> without loading any image to it. If it is useful, then we should state >>> that and make it stop crashing. >> >> I don't really know. All I see is that from the code at it was >> supported at least at some point. >> >>> >>> There is already a barrier, see >>> remote-sim.c:gdbsim_xfer_inferior_memory. The same message will be >>> displayed there with an error. >>> >>> if (!sim_data->program_loaded) >>> error (_("No program loaded.")); >>> >>> So, in a way, we're already preventing this scenario later on. If we >>> want to keep the old behavior, for whatever old reason that may be, i'm >>> ok with it. >>> >>> #0 0x00000000006a0580 in ARMul_SetPC (state=0x0, value=0) at >>> ../../../gdb-head/sim/arm/armsupp.c:83 >> >> Curious. 'state' is initialized by the ARM sim's 'init' function in >> the same file, and init is called only by sim_write, sim_read, >> sim_store_register and sim_fetch_register. 'init' ends up >> getting called by "load", through sim_load -> sim_load_file -> >> sim_write. >> >>> #1 0x0000000000690cef in sim_create_inferior (sd=0x1, abfd=0x0, >>> argv=0x0, env=0xc21d90) at ../../../gdb-head/sim/arm/wrapper.c:249 >>> #2 0x0000000000456a93 in gdbsim_create_inferior (target=0xb58100 >>> , exec_file=0x0, args=0xc39df0 "", env=0xc21d90, from_tty=1) >>> at ../../gdb-head/gdb/remote-sim.c:646 >> >> >>>>> >>>>> Replacing those warnings with error calls seems to be the most >>>>> appropriate here. >>>> >>>> Well, the code seems to have been written like that for a reason. >>>> >>>> Real boards can be powered on with no real program in memory >>>> too... >>>> >>> >>> Of course. The question is if there is any useful use case of letting >>> the simulator run without any images loaded. >> >> I'll leave that up to Mike. >> >>> >>>>> if (exec_file == 0 || exec_bfd == 0) >>>>> - warning (_("No executable file specified.")); >>>>> + error (_("No executable file specified.")); >>>>> if (!sim_data->program_loaded) >>>>> - warning (_("No program loaded.")); >>>>> + error (_("No program loaded.")); >>>>> >>>> >>>> There's code just below that does: >>>> >>>>> if (remote_debug) >>>>> printf_filtered ("gdbsim_create_inferior: exec_file \"%s\", >>>>> args \"%s\"\n", >>>> ... >>>>> if (exec_file != NULL) >>>>> { >>>>> len = strlen (exec_file) + 1 + strlen (args) + 1 + /*slop */ >>>>> 10; >>>>> arg_buf = (char *) alloca (len); >>>>> arg_buf[0] = '\0'; >>>>> strcat (arg_buf, exec_file); >>>>> strcat (arg_buf, " "); >>>>> strcat (arg_buf, args); >>>>> argv = gdb_buildargv (arg_buf); >>>>> make_cleanup_freeargv (argv); >>>>> } >>>>> else >>>>> argv = NULL; >>>> >>>> So if we error out, then these NULL checks are now dead. >>>> >>> >>> Right. This may turn to be dead code and may need removal. >> >> I have no doubt it ends up as dead code. ;-) The patch just >> looks obviously incomplete as is, and that prompted my reply. >> >>> Is there a good reason why bfin would allow things to proceed without >>> any image? It doesn't even run past that point really. >>> >>> All i see, for whatever operation, is "No memory". >> >> Leaving to Mike. I just picked bfin because it's a maintained sim. >> >>> ppc gives me "No program loaded", "The program is not being run" and >>> "The program has no registers now" >>> >>> mips says "sim_monitor: unhandled reason = 0, pc = 0xbfc00000", then >>> falls into the old "Cannot execute this command while the selected >>> thread is running" or "sim-events.c:231: assertion failed - >>> events->resume_wallclock == 0". >>> >>> If running, and by that i mean issuing run/start/continue/step commands, >>> the simulators with no image is a valid use case, then sounds like >>> steering the arm simulator to just do more or less what the other >>> simulators do is the right thing. >>> >>> If the use case is not useful at all, i think we should just wipe it out >>> rather than preserve some old unclear feature. >> >> Thank you -- all this analysis is much clearer and a stronger >> rationale than the original "silly", or just calling out >> that things seem appropriate with no backing. ;-) >> > > Ok. That's good. :-) > > I'll wait for Mike's feedback before attempting any other changes for > this particular issue. > > Luis > >