From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758131Ab2IMPGb (ORCPT ); Thu, 13 Sep 2012 11:06:31 -0400 Received: from mail-pb0-f46.google.com ([209.85.160.46]:40064 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758112Ab2IMPG1 (ORCPT ); Thu, 13 Sep 2012 11:06:27 -0400 From: Anton Vorontsov To: Andrew Morton , Russell King , Jason Wessel , Greg Kroah-Hartman , Alan Cox Cc: =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= , Colin Cross , Brian Swetland , John Stultz , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linaro-kernel@lists.linaro.org, patches@linaro.org, kernel-team@android.com, kgdb-bugreport@lists.sourceforge.net, linux-serial@vger.kernel.org Subject: [PATCH 01/11] kernel/debug: Mask KGDB NMI upon entry Date: Thu, 13 Sep 2012 08:03:25 -0700 Message-Id: <1347548615-18227-1-git-send-email-anton.vorontsov@linaro.org> X-Mailer: git-send-email 1.7.11.5 In-Reply-To: <20120913150133.GA16238@lizard> References: <20120913150133.GA16238@lizard> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The new arch callback should manage NMIs that usually cause KGDB to enter. That is, not all NMIs should be enabled/disabled, but only those that issue kgdb_handle_exception(). We must mask it as serial-line interrupt can be used as an NMI, so if the original KGDB-entry cause was say a breakpoint, then every input to KDB console will cause KGDB to reenter, which we don't want. Signed-off-by: Anton Vorontsov --- include/linux/kgdb.h | 23 +++++++++++++++++++++++ kernel/debug/debug_core.c | 36 +++++++++++++++++++++++++++++++++--- 2 files changed, 56 insertions(+), 3 deletions(-) diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h index c4d2fc1..3b111a6 100644 --- a/include/linux/kgdb.h +++ b/include/linux/kgdb.h @@ -221,6 +221,29 @@ extern int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt); */ extern void kgdb_arch_late(void); +/** + * kgdb_arch_enable_nmi - Enable or disable KGDB-entry NMI + * @on: Flag to either enable or disable an NMI + * + * This is an architecture-specific "back-end" for kgdb_enable_nmi(). The + * call does not count disable/enable requests, do not use it directly. + */ +extern void kgdb_arch_enable_nmi(bool on); + +/** + * kgdb_enable_nmi - Enable or disable KGDB-entry NMI + * @on: Flag to either enable or disable an NMI + * + * This function manages NMIs that usually cause KGDB to enter. That is, + * not all NMIs should be enabled or disabled, but only those that issue + * kgdb_handle_exception(). + * + * The call counts disable requests, and thus allows to nest disables. + * But trying to enable already enabled NMI is an error. The call returns + * 1 if NMI has been actually enabled after the call, and a value <= 0 if + * it is still disabled. + */ +extern int kgdb_enable_nmi(bool on); /** * struct kgdb_arch - Describe architecture specific values. diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c index 0557f24..b621d1e 100644 --- a/kernel/debug/debug_core.c +++ b/kernel/debug/debug_core.c @@ -214,6 +214,30 @@ int __weak kgdb_skipexception(int exception, struct pt_regs *regs) return 0; } +void __weak kgdb_arch_enable_nmi(bool on) +{ +} + +int kgdb_enable_nmi(bool on) +{ + static atomic_t cnt; + int ret; + + ret = atomic_add_return(on ? 1 : -1, &cnt); + if (ret > 1 && on) { + /* + * There should be only one instance that calls this function + * in "enable, disable" order. All other users must call + * disable first, then enable. If not, something is wrong. + */ + WARN_ON(1); + return 1; + } + + kgdb_arch_enable_nmi(ret > 0); + return ret; +} + /* * Some architectures need cache flushes when we set/clear a * breakpoint: @@ -672,6 +696,9 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) { struct kgdb_state kgdb_var; struct kgdb_state *ks = &kgdb_var; + int ret = 0; + + kgdb_enable_nmi(0); ks->cpu = raw_smp_processor_id(); ks->ex_vector = evector; @@ -681,11 +708,14 @@ kgdb_handle_exception(int evector, int signo, int ecode, struct pt_regs *regs) ks->linux_regs = regs; if (kgdb_reenter_check(ks)) - return 0; /* Ouch, double exception ! */ + goto out; /* Ouch, double exception ! */ if (kgdb_info[ks->cpu].enter_kgdb != 0) - return 0; + goto out; - return kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); + ret = kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER); +out: + kgdb_enable_nmi(1); + return ret; } int kgdb_nmicallback(int cpu, void *regs) -- 1.7.11.5