From patchwork Sun Sep 14 12:06:33 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yao Qi X-Patchwork-Id: 2836 Received: (qmail 12709 invoked by alias); 14 Sep 2014 12:11:15 -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 12698 invoked by uid 89); 14 Sep 2014 12:11:14 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-1.7 required=5.0 tests=AWL, BAYES_00 autolearn=no version=3.3.2 X-HELO: relay1.mentorg.com Received: from relay1.mentorg.com (HELO relay1.mentorg.com) (192.94.38.131) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Sun, 14 Sep 2014 12:11:13 +0000 Received: from svr-orw-fem-06.mgc.mentorg.com ([147.34.97.120]) by relay1.mentorg.com with esmtp id 1XT8e6-00010Z-EE from Yao_Qi@mentor.com for gdb-patches@sourceware.org; Sun, 14 Sep 2014 05:11:10 -0700 Received: from qiyao.dyndns.org.com (147.34.91.1) by SVR-ORW-FEM-06.mgc.mentorg.com (147.34.97.120) with Microsoft SMTP Server id 14.3.181.6; Sun, 14 Sep 2014 05:11:09 -0700 From: Yao Qi To: Subject: [PATCH] Honour SIGILL and SIGSEGV in cancel breakpoint Date: Sun, 14 Sep 2014 20:06:33 +0800 Message-ID: <1410696393-29327-1-git-send-email-yao@codesourcery.com> MIME-Version: 1.0 X-IsSubscribed: yes I see the following fail on are-none-linux-gnueabi testing, (gdb) continue^M Continuing.^M ^M Program received signal SIGILL, Illegal instruction.^M [Switching to Thread 1003]^M handler (signo=10) at /scratch/yqi/arm-none-linux-gnueabi/src/gdb-trunk/gdb/testsuite/gdb.threads/sigstep-threads.c:33^M 33 tgkill (getpid (), gettid (), SIGUSR1); /* step-2 */^M (gdb) FAIL: gdb.threads/sigstep-threads.exp: continue the cause is that GDBserver doesn't cancel the breakpoint if the stop signal is SIGILL. The kernel used here is a little old, 2.6.x, and doesn't translate SIGILL to SIGTRAP when program hits breakpoint instruction (which is an illegal instruction actually). GDB and GDBserver can translate SIGILL to SIGTRAP under certain circumstance, so it is not a problem here. See gdbserver/linux-low.c:linux_wait_1 /* If this event was not handled before, and is not a SIGTRAP, we report it. SIGILL and SIGSEGV are also treated as traps in case a breakpoint is inserted at the current PC. If this target does not support internal breakpoints at all, we also report the SIGTRAP without further processing; it's of no concern to us. */ maybe_internal_trap = (supports_breakpoints () && (WSTOPSIG (w) == SIGTRAP || ((WSTOPSIG (w) == SIGILL || WSTOPSIG (w) == SIGSEGV) && (*the_low_target.breakpoint_at) (event_child->stop_pc)))); However, SIGILL and SIGSEGV is not considered when cancelling breakpoint, which causes the fail above. That is, when GDB is doing software single step on address ADDR, both thread A and thread B hits the software single step breakpoint, and get SIGILL. GDB selects the event from thread A, removes the software single step breakpoint, and resume the program. The event (SIGILL) from thread B is reported to GDB, but GDB doesn't regard this SIGILL as SIGTRAP, because the breakpoint on address ADDR was removed, so GDB reports "Program received signal SIGILL". The patch is to allow calling cancel_breakpoint if the signal is SIGILL and SIGSEGV. This patch fixes the fail above. Regression tested on arm-none-linux-gnueabi and x86_64-linux. gdb/gdbserver: 2014-09-12 Yao Qi * linux-low.c (cancel_breakpoints_callback): Allow calling cancel_breakpoint if stop signal is SIGILL or SIGSEGV. (linux_low_filter_event): Likewise. --- gdb/gdbserver/linux-low.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c index ec3260e..e2c9814 100644 --- a/gdb/gdbserver/linux-low.c +++ b/gdb/gdbserver/linux-low.c @@ -1936,7 +1936,12 @@ linux_low_filter_event (ptid_t filter_ptid, int lwpid, int wstat) the core before this one is handled. All-stop always cancels breakpoint hits in all threads. */ if (non_stop - && WSTOPSIG (wstat) == SIGTRAP + && (WSTOPSIG (wstat) == SIGTRAP + /* SIGILL and SIGSEGV are also treated as traps in + case a breakpoint is inserted at the current PC, + which is checked in cancel_breakpoints below. */ + || WSTOPSIG (wstat) == SIGILL + || WSTOPSIG (wstat) == SIGSEGV) && cancel_breakpoint (child)) { /* Throw away the SIGTRAP. */ @@ -2273,7 +2278,12 @@ cancel_breakpoints_callback (struct inferior_list_entry *entry, void *data) && thread->last_status.kind == TARGET_WAITKIND_IGNORE && lp->status_pending_p && WIFSTOPPED (lp->status_pending) - && WSTOPSIG (lp->status_pending) == SIGTRAP + && (WSTOPSIG (lp->status_pending) == SIGTRAP + /* SIGILL and SIGSEGV are also treated as traps in case a + breakpoint is inserted at the current PC, which is checked + in cancel_breakpoints below. */ + || WSTOPSIG (lp->status_pending) == SIGILL + || WSTOPSIG (lp->status_pending) == SIGSEGV) && !lp->stepping && !lp->stopped_by_watchpoint && cancel_breakpoint (lp))