From patchwork Thu Nov 13 19:02:55 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Pedro Alves X-Patchwork-Id: 3718 Received: (qmail 31857 invoked by alias); 13 Nov 2014 19:46:01 -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 31847 invoked by uid 89); 13 Nov 2014 19:46:00 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.5 required=5.0 tests=AWL, BAYES_00, RP_MATCHES_RCVD, SPF_HELO_PASS, SPF_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; Thu, 13 Nov 2014 19:45:59 +0000 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id sADJjvik021720 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Thu, 13 Nov 2014 14:45:58 -0500 Received: from brno.lan (ovpn01.gateway.prod.ext.ams2.redhat.com [10.39.146.11]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id sADJ2tDE019476 for ; Thu, 13 Nov 2014 14:02:56 -0500 From: Pedro Alves To: gdb-patches@sourceware.org Subject: [PATCH] follow-exec: handle targets that don't have thread exit events Date: Thu, 13 Nov 2014 19:02:55 +0000 Message-Id: <1415905375-29865-1-git-send-email-palves@redhat.com> ... such as remote. Ref: https://sourceware.org/ml/gdb-patches/2014-11/msg00268.html This fixes invalid reads Valgrind caught when debugging against a GDBserver patched with a series that adds exec events to the remote protocol. Like these, using the gdb.threads/thread-execl.exp test: $ valgrind ./gdb -data-directory=data-directory ./testsuite/gdb.threads/thread-execl -ex "tar extended-remote :9999" -ex "b thread_execler" -ex "c" -ex "set scheduler-locking on" ... Breakpoint 1, thread_execler (arg=0x0) at src/gdb/testsuite/gdb.threads/thread-execl.c:29 29 if (execl (image, image, NULL) == -1) (gdb) n Thread 32509.32509 is executing new program: build/gdb/testsuite/gdb.threads/thread-execl [New Thread 32509.32532] ==32510== Invalid read of size 4 ==32510== at 0x5AA7D8: delete_breakpoint (breakpoint.c:13989) ==32510== by 0x6285D3: delete_thread_breakpoint (thread.c:100) ==32510== by 0x628603: delete_step_resume_breakpoint (thread.c:109) ==32510== by 0x61622B: delete_thread_infrun_breakpoints (infrun.c:2928) ==32510== by 0x6162EF: for_each_just_stopped_thread (infrun.c:2958) ==32510== by 0x616311: delete_just_stopped_threads_infrun_breakpoints (infrun.c:2969) ==32510== by 0x616C96: fetch_inferior_event (infrun.c:3267) ==32510== by 0x63A2DE: inferior_event_handler (inf-loop.c:57) ==32510== by 0x4E0E56: remote_async_serial_handler (remote.c:11877) ==32510== by 0x4AF620: run_async_handler_and_reschedule (ser-base.c:137) ==32510== by 0x4AF6F0: fd_event (ser-base.c:182) ==32510== by 0x63806D: handle_file_event (event-loop.c:762) ==32510== Address 0xcf333e0 is 16 bytes inside a block of size 200 free'd ==32510== at 0x4A07577: free (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so) ==32510== by 0x77CB74: xfree (common-utils.c:98) ==32510== by 0x5AA954: delete_breakpoint (breakpoint.c:14056) ==32510== by 0x5988BD: update_breakpoints_after_exec (breakpoint.c:3765) ==32510== by 0x61360F: follow_exec (infrun.c:1091) ==32510== by 0x6186FA: handle_inferior_event (infrun.c:4061) ==32510== by 0x616C55: fetch_inferior_event (infrun.c:3261) ==32510== by 0x63A2DE: inferior_event_handler (inf-loop.c:57) ==32510== by 0x4E0E56: remote_async_serial_handler (remote.c:11877) ==32510== by 0x4AF620: run_async_handler_and_reschedule (ser-base.c:137) ==32510== by 0x4AF6F0: fd_event (ser-base.c:182) ==32510== by 0x63806D: handle_file_event (event-loop.c:762) ==32510== [Switching to Thread 32509.32532] Breakpoint 1, thread_execler (arg=0x0) at src/gdb/testsuite/gdb.threads/thread-execl.c:29 29 if (execl (image, image, NULL) == -1) (gdb) The breakpoint in question is the step-resume breakpoint of the non-main thread, the one that was "next"ed. Tested on x86_64 Fedora 20. gdb/ 2014-11-13 Pedro Alves * infrun.c (follow_exec): Delete all threads of the process except the event thread. Extended comments. --- gdb/infrun.c | 44 ++++++++++++++++++++++++++++++++------------ 1 file changed, 32 insertions(+), 12 deletions(-) diff --git a/gdb/infrun.c b/gdb/infrun.c index 7e59f55..0532d3e 100644 --- a/gdb/infrun.c +++ b/gdb/infrun.c @@ -1060,10 +1060,11 @@ show_follow_exec_mode_string (struct ui_file *file, int from_tty, /* EXECD_PATHNAME is assumed to be non-NULL. */ static void -follow_exec (ptid_t pid, char *execd_pathname) +follow_exec (ptid_t ptid, char *execd_pathname) { - struct thread_info *th = inferior_thread (); + struct thread_info *th, *tmp; struct inferior *inf = current_inferior (); + int pid = ptid_get_pid (ptid); /* This is an exec event that we actually wish to pay attention to. Refresh our symbol table to the newly exec'd program, remove any @@ -1088,24 +1089,43 @@ follow_exec (ptid_t pid, char *execd_pathname) mark_breakpoints_out (); - update_breakpoints_after_exec (); - - /* If there was one, it's gone now. We cannot truly step-to-next - statement through an exec(). */ + /* The target reports the exec event to the main thread, even if + some other thread does the exec, and even if the main thread was + stopped or already gone. On targets that don't have thread exit + events (like remote), we may still have non-leader threads of the + process on our list. When debugging remotely, it's best to avoid + extra traffic, when possible, so avoid syncing the thread list + with the target, and instead go ahead and delete all threads of + the process but one that reported the event. Note this must be + done before calling update_breakpoints_after_exec, as otherwise + clearing the threads' resources would reference stale thread + breakpoints -- it may have been one of these threads that stepped + across the exec. We could just clear their stepping states, but + as long as we're iterating, might as well delete them. Deleting + them now rather than at the next user-visible stop provides a + nicer sequence of events for user and MI notifications. */ + ALL_NON_EXITED_THREADS_SAFE (th, tmp) + if (ptid_get_pid (th->ptid) == pid && !ptid_equal (th->ptid, ptid)) + delete_thread (th->ptid); + + /* We also need to clear any left over stale state for the + leader/event thread. E.g., if there was any step-resume + breakpoint or similar, it's gone now. We cannot truly + step-to-next statement through an exec(). */ + th = inferior_thread (); th->control.step_resume_breakpoint = NULL; th->control.exception_resume_breakpoint = NULL; th->control.single_step_breakpoints = NULL; th->control.step_range_start = 0; th->control.step_range_end = 0; - /* The target reports the exec event to the main thread, even if - some other thread does the exec, and even if the main thread was - already stopped --- if debugging in non-stop mode, it's possible - the user had the main thread held stopped in the previous image - --- release it now. This is the same behavior as step-over-exec - with scheduler-locking on in all-stop mode. */ + /* The user may have had the main thread held stopped in the + previous image (e.g., schedlock on, or non-stop). Release + it now. */ th->stop_requested = 0; + update_breakpoints_after_exec (); + /* What is this a.out's name? */ printf_unfiltered (_("%s is executing new program: %s\n"), target_pid_to_str (inferior_ptid),