From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964955Ab2JSDRc (ORCPT ); Thu, 18 Oct 2012 23:17:32 -0400 Received: from mail.kernel.org ([198.145.19.201]:54430 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757842Ab2JSDRW (ORCPT ); Thu, 18 Oct 2012 23:17:22 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Greg Kroah-Hartman , alan@lxorguk.ukuu.org.uk, Jason Wessel , Masami Hiramatsu , "David S. Miller" Subject: [ 05/37] mips,kgdb: fix recursive page fault with CONFIG_KPROBES Date: Thu, 18 Oct 2012 20:16:28 -0700 Message-Id: <20121019031303.646702741@linuxfoundation.org> X-Mailer: git-send-email 1.8.0.rc0.18.gf84667d In-Reply-To: <20121019031302.789593147@linuxfoundation.org> References: <20121019031302.789593147@linuxfoundation.org> User-Agent: quilt/0.60-2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.0-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jason Wessel commit f0a996eeeda214f4293e234df33b29bec003b536 upstream. This fault was detected using the kgdb test suite on boot and it crashes recursively due to the fact that CONFIG_KPROBES on mips adds an extra die notifier in the page fault handler. The crash signature looks like this: kgdbts:RUN bad memory access test KGDB: re-enter exception: ALL breakpoints killed Call Trace: [<807b7548>] dump_stack+0x20/0x54 [<807b7548>] dump_stack+0x20/0x54 The fix for now is to have kgdb return immediately if the fault type is DIE_PAGE_FAULT and allow the kprobe code to decide what is supposed to happen. Signed-off-by: Jason Wessel Cc: Masami Hiramatsu Cc: David S. Miller Signed-off-by: Greg Kroah-Hartman --- arch/mips/kernel/kgdb.c | 9 +++++++++ 1 file changed, 9 insertions(+) --- a/arch/mips/kernel/kgdb.c +++ b/arch/mips/kernel/kgdb.c @@ -283,6 +283,15 @@ static int kgdb_mips_notify(struct notif struct pt_regs *regs = args->regs; int trap = (regs->cp0_cause & 0x7c) >> 2; +#ifdef CONFIG_KPROBES + /* + * Return immediately if the kprobes fault notifier has set + * DIE_PAGE_FAULT. + */ + if (cmd == DIE_PAGE_FAULT) + return NOTIFY_DONE; +#endif /* CONFIG_KPROBES */ + /* Userspace events, ignore. */ if (user_mode(regs)) return NOTIFY_DONE;