From patchwork Fri Aug 21 23:37:33 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: 8390 Received: (qmail 103479 invoked by alias); 21 Aug 2015 23:37:50 -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 103402 invoked by uid 89); 21 Aug 2015 23:37:49 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.6 required=5.0 tests=AWL, BAYES_00, KAM_LAZY_DOMAIN_SECURITY, RP_MATCHES_RCVD, SPF_HELO_PASS autolearn=no 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; Fri, 21 Aug 2015 23:37:48 +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 638478CF7E for ; Fri, 21 Aug 2015 23:37:47 +0000 (UTC) Received: from psique.yyz.redhat.com (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 t7LNbk1A004671; Fri, 21 Aug 2015 19:37:47 -0400 From: Sergio Durigan Junior To: GDB Patches Cc: Sergio Durigan Junior Subject: [PATCH 2/2] Catching errors on probes-based dynamic linker interface Date: Fri, 21 Aug 2015 19:37:33 -0400 Message-Id: <1440200253-28603-3-git-send-email-sergiodj@redhat.com> In-Reply-To: <1440200253-28603-1-git-send-email-sergiodj@redhat.com> References: <1440200253-28603-1-git-send-email-sergiodj@redhat.com> X-IsSubscribed: yes This patch is intended to make the interaction between the probes-based dynamic linker interface and the SystemTap SDT probe code on GDB more robust. It does that by wrapping the calls to the probe API with TRY...CATCH'es, so that any exception thrown will be caught and handled properly. The idea for this patch came from , which is a bug initially filed against Fedora GDB (but now under Fedora GLIBC). This bug happens on armhfp (although it could happen on other targets as well), and is triggered because GCC generates a strange argument for one of the probes used by GDB in the dynamic linker interface. As can be seen in the bug, this argument is "-4@.L1052". I don't want to discuss the reasons for this argument to be there (this discussion belongs to the bug, or to another thread), but GDB could definitely do a better error handling here. Currently, one sees the following message when there is an error in the probes-based dynamic linker interface: (gdb) run Starting program: /bin/inferior warning: Probes-based dynamic linker interface failed. Reverting to original interface. Cannot parse expression `.L976 4@r4'. (gdb) Which means that one needs to explicitly issue a "continue" command to make GDB continue running the inferior, even though this error is not fatal and GDB will fallback to the old interface automatically. This is where this patch helps: it makes GDB still print the necessary warnings or error messages, but it *also* does not stop the inferior unnecessarily. I have tested this patch on the systems where this error happens, but I could not come up with a way to create a testcase for it. Nevertheless, it should be straightforward to see that this patch does improve the current situation. OK to apply? gdb/ChangeLog: 2015-08-21 Sergio Durigan Junior * solib-svr4.c (solib_event_probe_action): Call get_probe_argument_count using TRY...CATCH. (svr4_handle_solib_event): Likewise, for evaluate_probe_argument. --- gdb/solib-svr4.c | 36 +++++++++++++++++++++++++++++++++--- 1 file changed, 33 insertions(+), 3 deletions(-) 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) @@ -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 +1991,17 @@ 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);