From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755340Ab3JYPWn (ORCPT ); Fri, 25 Oct 2013 11:22:43 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:51554 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753478Ab3JYPWm (ORCPT ); Fri, 25 Oct 2013 11:22:42 -0400 Date: Fri, 25 Oct 2013 16:22:36 +0100 From: Will Deacon To: Sandeepa Prabhu Cc: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "patches@linaro.org" , "linaro-kernel@lists.linaro.org" , Catalin Marinas , "steve.capper@linaro.org" , "nico@linaro.org" , "srikar@linux.vnet.ibm.com" , "rostedt@goodmis.org" , "masami.hiramatsu.pt@hitachi.com" , "dsaxena@linaro.org" , "jiang.liu@huawei.com" , "Vijaya.Kumar@caviumnetworks.com" Subject: Re: [PATCH RFC v4 1/6] arm64: support single-step and breakpoint handler hooks Message-ID: <20131025152236.GC10673@mudshark.cambridge.arm.com> References: <1382008671-4515-1-git-send-email-sandeepa.prabhu@linaro.org> <1382008671-4515-2-git-send-email-sandeepa.prabhu@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1382008671-4515-2-git-send-email-sandeepa.prabhu@linaro.org> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sandeepa, This is getting there, thanks for persevering with it. I still have a few minor comments though. On Thu, Oct 17, 2013 at 12:17:46PM +0100, Sandeepa Prabhu wrote: > AArch64 Single Steping and Breakpoint debug exceptions will be > used by multiple debug framworks like kprobes & kgdb. > > This patch implements the hooks for those frameworks to register > their own handlers for handling breakpoint and single step events. > > Reworked the debug exception handler in entry.S: do_dbg to route > software breakpoint (BRK64) exception to do_debug_exception() > > Signed-off-by: Sandeepa Prabhu > Signed-off-by: Deepak Saxena > --- > arch/arm64/include/asm/debug-monitors.h | 21 ++++++++ > arch/arm64/kernel/debug-monitors.c | 86 ++++++++++++++++++++++++++++++++- > arch/arm64/kernel/entry.S | 2 + > 3 files changed, 108 insertions(+), 1 deletion(-) [...] > @@ -215,7 +257,10 @@ static int single_step_handler(unsigned long addr, unsigned int esr, > */ > user_rewind_single_step(current); > } else { > - /* TODO: route to KGDB */ > + /* call registered single step handlers */ Don't bother with this comment (it's crystal clear from the code). > + if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED) > + return 0; > + > pr_warning("Unexpected kernel single-step exception at EL1\n"); > /* > * Re-enable stepping since we know that we will be > @@ -227,11 +272,50 @@ static int single_step_handler(unsigned long addr, unsigned int esr, > return 0; > } > > + > +static LIST_HEAD(break_hook); > +DEFINE_RWLOCK(break_hook_lock); This guy can be a plain old spinlock. That way, the readers have less overhead but things still work because we only call a single hook function. Will