From patchwork Mon Aug 24 16:09:20 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sergio Durigan Junior X-Patchwork-Id: 8409 Received: (qmail 88722 invoked by alias); 24 Aug 2015 16:09:26 -0000 Mailing-List: contact gdb-patches-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gdb-patches-owner@sourceware.org Delivered-To: mailing list gdb-patches@sourceware.org Received: (qmail 88017 invoked by uid 89); 24 Aug 2015 16:09:25 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL, BAYES_00, KAM_LAZY_DOMAIN_SECURITY, RP_MATCHES_RCVD, SPF_HELO_PASS autolearn=ham version=3.3.2 X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Mon, 24 Aug 2015 16:09:22 +0000 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id 9C2818E367 for ; Mon, 24 Aug 2015 16:09:21 +0000 (UTC) Received: from localhost (unused-10-15-17-51.yyz.redhat.com [10.15.17.51]) by int-mx13.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t7OG9KKl021383 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Mon, 24 Aug 2015 12:09:21 -0400 From: Sergio Durigan Junior To: Gary Benson Cc: GDB Patches Subject: Re: [PATCH 2/2] Catching errors on probes-based dynamic linker interface References: <1440200253-28603-1-git-send-email-sergiodj@redhat.com> <1440200253-28603-3-git-send-email-sergiodj@redhat.com> <20150824084255.GA16508@blade.nx> X-URL: http://blog.sergiodj.net Date: Mon, 24 Aug 2015 12:09:20 -0400 In-Reply-To: <20150824084255.GA16508@blade.nx> (Gary Benson's message of "Mon, 24 Aug 2015 09:42:55 +0100") Message-ID: <87r3msd5xr.fsf@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 X-IsSubscribed: yes Thanks for the review, Gary. On Monday, August 24 2015, Gary Benson wrote: >> diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c >> index 1fb07d5..028c3d0 100644 >> --- a/gdb/solib-svr4.c >> +++ b/gdb/solib-svr4.c >> @@ -1786,7 +1786,17 @@ solib_event_probe_action (struct probe_and_action *pa) >> arg0: Lmid_t lmid (mandatory) >> arg1: struct r_debug *debug_base (mandatory) >> arg2: struct link_map *new (optional, for incremental updates) */ >> - probe_argc = get_probe_argument_count (pa->probe, frame); >> + TRY >> + { >> + probe_argc = get_probe_argument_count (pa->probe, frame); >> + } >> + CATCH (ex, RETURN_MASK_ERROR) >> + { >> + exception_print (gdb_stderr, ex); >> + probe_argc = 0; >> + } >> + END_CATCH >> + >> if (probe_argc == 2) >> action = FULL_RELOAD; >> else if (probe_argc < 2) > > Maybe this would be clearer and more robust: > > TRY > { > unsigned probe_argc; > > probe_argc = get_probe_argument_count (pa->probe, frame); > > if (probe_argc == 2) > action = FULL_RELOAD; > else if (probe_argc < 2) > action = PROBES_INTERFACE_FAILED; > } > CATCH (ex, RETURN_MASK_ERROR) > { > exception_print (gdb_stderr, ex); > action = PROBES_INTERFACE_FAILED; > } > END_CATCH Maybe it's a matter of preference, but I don't like this (and I don't see why it is more robust). I prefer to have as little code as possible running on the TRY block, and handle everything else outside of it. I think it also makes things a bit more confuse because you have two places where action can be PROBES_INTERFACE_FAILED. I am using this idiom in the other places as well, so I also think it is good to keep things similar across the code. >> @@ -1971,7 +1991,17 @@ svr4_handle_solib_event (void) >> >> if (action == UPDATE_OR_RELOAD) >> { >> - val = evaluate_probe_argument (pa->probe, 2, frame); >> + TRY >> + { >> + val = evaluate_probe_argument (pa->probe, 2, frame); >> + } >> + CATCH (ex, RETURN_MASK_ERROR) >> + { >> + exception_print (gdb_stderr, ex); >> + val = NULL; >> + } >> + END_CATCH >> + >> if (val != NULL) >> lm = value_as_address (val); >> > > This failure will not cause the probes interface to be disabled. > FULL_RELOAD is an ok thing to do here, but it could be difficult > to debug in future (if this one probe argument is broken GDB will > be very much slower than it could be.) So maybe this should be: > > CATCH (ex, RETURN_MASK_ERROR) > { > exception_print (gdb_stderr, ex); > do_cleanups (old_chain); > return; > } > END_CATCH You're right, thanks for... catching... this. > As an aside it would clarify this code greatly if "old_chain" > were renamed "disable_probes_interface" or similar. It took > me a while to figure out what the code was doing, and I wrote > it! Yeah. I'll leave this to another patch. Here's the updated version of the current patch. Thanks, diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c index 1fb07d5..fd90fc8 100644 --- a/gdb/solib-svr4.c +++ b/gdb/solib-svr4.c @@ -1786,7 +1786,17 @@ solib_event_probe_action (struct probe_and_action *pa) arg0: Lmid_t lmid (mandatory) arg1: struct r_debug *debug_base (mandatory) arg2: struct link_map *new (optional, for incremental updates) */ - probe_argc = get_probe_argument_count (pa->probe, frame); + TRY + { + probe_argc = get_probe_argument_count (pa->probe, frame); + } + CATCH (ex, RETURN_MASK_ERROR) + { + exception_print (gdb_stderr, ex); + probe_argc = 0; + } + END_CATCH + if (probe_argc == 2) action = FULL_RELOAD; else if (probe_argc < 2) @@ -1940,7 +1950,17 @@ svr4_handle_solib_event (void) usm_chain = make_cleanup (resume_section_map_updates_cleanup, current_program_space); - val = evaluate_probe_argument (pa->probe, 1, frame); + TRY + { + val = evaluate_probe_argument (pa->probe, 1, frame); + } + CATCH (ex, RETURN_MASK_ERROR) + { + exception_print (gdb_stderr, ex); + val = NULL; + } + END_CATCH + if (val == NULL) { do_cleanups (old_chain); @@ -1971,7 +1991,18 @@ svr4_handle_solib_event (void) if (action == UPDATE_OR_RELOAD) { - val = evaluate_probe_argument (pa->probe, 2, frame); + TRY + { + val = evaluate_probe_argument (pa->probe, 2, frame); + } + CATCH (ex, RETURN_MASK_ERROR) + { + exception_print (gdb_stderr, ex); + do_cleanups (old_chain); + return; + } + END_CATCH + if (val != NULL) lm = value_as_address (val);