From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 128865 invoked by alias); 11 Apr 2019 02:49:18 -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 128846 invoked by uid 89); 11 Apr 2019 02:49:17 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-5.9 required=5.0 tests=AWL,BAYES_50,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.1 spammy=territory, stapprobec, UD:stap-probe.c, stap-probe.c X-HELO: simark.ca Received: from simark.ca (HELO simark.ca) (158.69.221.121) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 11 Apr 2019 02:49:15 +0000 Received: from [10.0.0.11] (unknown [192.222.164.54]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by simark.ca (Postfix) with ESMTPSA id 994551E0A9; Wed, 10 Apr 2019 22:49:12 -0400 (EDT) Subject: Re: [PATCH] Fix "nosharedlibrary + continue + shared lib event" crash To: Pedro Alves , gdb-patches@sourceware.org References: <20190409131410.10205-1-palves@redhat.com> From: Simon Marchi Message-ID: Date: Thu, 11 Apr 2019 02:49:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <20190409131410.10205-1-palves@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-SW-Source: 2019-04/txt/msg00195.txt.bz2 On 2019-04-09 9:14 a.m., Pedro Alves wrote: > GDB misbehaves if you run the "nosharelibrary" command, continue > execution, and then the program hits the shared library event > breakpoint. On my system it aborts like this: > > (gdb) nosharedlibrary > (gdb) c > Continuing. > pure virtual method called > terminate called without an active exception > Aborted (core dumped) > > Though it's really undefined behavior territory, caused by deferencing > a dangling solib event probe pointer. > > I've observed this by running "nosharedlibrary" when stopped at the > entry point, but it should happen at any other point, if the program > does a dlopen/dlclose after. > > The fix is to discard an objfile's probes from the svr4 probes table > when an objfile is about to be released. > > New test included, works with both native and gdbserver testing. > > Valgrind log: > > (gdb) starti > (gdb) nosharedlibrary > (gdb) c > Continuing. > ==24895== Invalid read of size 8 > ==24895== at 0x89E5FB: solib_event_probe_action(probe_and_action*) (solib-svr4.c:1735) > ==24895== by 0x89E95A: svr4_handle_solib_event() (solib-svr4.c:1872) > ==24895== by 0x8A7198: handle_solib_event() (solib.c:1274) > ==24895== by 0x4E3407: bpstat_stop_status(address_space const*, unsigned long, thread_info*, target_waitstatus const*, bpstats*) (breakpoint.c:5407) > ==24895== by 0x721F41: handle_signal_stop(execution_control_state*) (infrun.c:5685) > ==24895== by 0x720B11: handle_inferior_event(execution_control_state*) (infrun.c:5129) > ==24895== by 0x71DD93: fetch_inferior_event(void*) (infrun.c:3748) > ==24895== by 0x7059C3: inferior_event_handler(inferior_event_type, void*) (inf-loop.c:43) > ==24895== by 0x874DF0: remote_async_serial_handler(serial*, void*) (remote.c:14039) > ==24895== by 0x894101: run_async_handler_and_reschedule(serial*) (ser-base.c:137) > ==24895== by 0x8941E6: fd_event(int, void*) (ser-base.c:188) > ==24895== by 0x67AFEF: handle_file_event(file_handler*, int) (event-loop.c:732) > ==24895== Address 0x18b63860 is 0 bytes inside a block of size 136 free'd > ==24895== at 0x4C2E616: operator delete(void*, unsigned long) (vg_replace_malloc.c:585) > ==24895== by 0x8C6A12: stap_probe::~stap_probe() (stap-probe.c:124) > ==24895== by 0x66F7DB: probe_key_free(bfd*, void*) (elfread.c:1382) > ==24895== by 0x69B705: bfdregistry_callback_adaptor(void (*)(registry_container*, void*), registry_container*, void*) (gdb_bfd.c:131) > ==24895== by 0x855A57: registry_clear_data(registry_data_registry*, void (*)(void (*)(registry_container*, void*), registry_container*, void*), registry_container*, registry_fields*) (registry.c:79) > ==24895== by 0x855B01: registry_container_free_data(registry_data_registry*, void (*)(void (*)(registry_container*, void*), registry_container*, void*), registry_container*, registry_fields*) (registry.c:92) > ==24895== by 0x69B783: bfd_free_data(bfd*) (gdb_bfd.c:131) > ==24895== by 0x69C4BA: gdb_bfd_unref(bfd*) (gdb_bfd.c:609) > ==24895== by 0x7CC33F: objfile::~objfile() (objfiles.c:651) > ==24895== by 0x7CD559: objfile_purge_solibs() (objfiles.c:1021) > ==24895== by 0x8A7132: no_shared_libraries(char const*, int) (solib.c:1252) > ==24895== by 0x548E3D: do_const_cfunc(cmd_list_element*, char const*, int) (cli-decode.c:106) > ==24895== Block was alloc'd at > ==24895== at 0x4C2D42A: operator new(unsigned long) (vg_replace_malloc.c:334) > ==24895== by 0x8C527C: handle_stap_probe(objfile*, sdt_note*, std::vector >*, unsigned long) (stap-probe.c:1561) > ==24895== by 0x8C5535: stap_static_probe_ops::get_probes(std::vector >*, objfile*) const (stap-probe.c:1656) > ==24895== by 0x66F71B: elf_get_probes(objfile*) (elfread.c:1365) > ==24895== by 0x7EDD85: find_probes_in_objfile(objfile*, char const*, char const*) (probe.c:227) > ==24895== by 0x4DF382: create_longjmp_master_breakpoint() (breakpoint.c:3275) > ==24895== by 0x4F6562: breakpoint_re_set() (breakpoint.c:13828) > ==24895== by 0x8A66AA: solib_add(char const*, int, int) (solib.c:1010) > ==24895== by 0x89F7C6: enable_break(svr4_info*, int) (solib-svr4.c:2360) > ==24895== by 0x8A104C: svr4_solib_create_inferior_hook(int) (solib-svr4.c:2992) > ==24895== by 0x8A70B9: solib_create_inferior_hook(int) (solib.c:1215) > ==24895== by 0x70C073: post_create_inferior(target_ops*, int) (infcmd.c:467) > ==24895== > pure virtual method called > terminate called without an active exception > ==24895== > ==24895== Process terminating with default action of signal 6 (SIGABRT): dumping core > ==24895== at 0x7CF3750: raise (raise.c:51) > ==24895== by 0x7CF4D30: abort (abort.c:79) > ==24895== by 0xB008F4: __gnu_cxx::__verbose_terminate_handler() (in build/gdb/gdb) > ==24895== by 0xAFF845: __cxxabiv1::__terminate(void (*)()) (in build/gdb/gdb) > ==24895== by 0xAFF890: std::terminate() (in build/gdb/gdb) > ==24895== by 0xAFF95E: __cxa_pure_virtual (in build/gdb/gdb) > ==24895== by 0x89E610: solib_event_probe_action(probe_and_action*) (solib-svr4.c:1735) > ==24895== by 0x89E95A: svr4_handle_solib_event() (solib-svr4.c:1872) > ==24895== by 0x8A7198: handle_solib_event() (solib.c:1274) > ==24895== by 0x4E3407: bpstat_stop_status(address_space const*, unsigned long, thread_info*, target_waitstatus const*, bpstats*) (breakpoint.c:5407) > ==24895== by 0x721F41: handle_signal_stop(execution_control_state*) (infrun.c:5685) > ==24895== by 0x720B11: handle_inferior_event(execution_control_state*) (infrun.c:5129) > ==24895== > > Note, this little bit in the patch is just a cleanup that I noticed: > > - lookup.prob = prob; > lookup.address = address; > > That line isn't necessary because hashing/comparison only looks at the > address. I am not able to reproduce the problem, and the test doesn't fail here, without the rest of the patch applied. I think it's because on my system gdb doesn't use the probe based interface. Anyhow, the fix makes sense. Since the probe is deleted on objfile destruction, the corresponding probe_and_action structures should too. Simon