From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: how to creat watchpoint in kernel for data access debug Date: Mon, 16 Jun 2014 13:55:06 +0100 Message-ID: <20140616125506.GD16758@arm.com> References: <35FD53F367049845BC99AC72306C23D1029A276569F3@CNBJMBX05.corpusers.net> <35FD53F367049845BC99AC72306C23D1029A276569F4@CNBJMBX05.corpusers.net> <20140523134550.GB21319@arm.com> <35FD53F367049845BC99AC72306C23D1029A276569FC@CNBJMBX05.corpusers.net> <20140603164512.GT23149@arm.com> <35FD53F367049845BC99AC72306C23D1029A27656A2F@CNBJMBX05.corpusers.net> <20140604180139.GD27881@arm.com> <35FD53F367049845BC99AC72306C23D1029A27656A34@CNBJMBX05.corpusers.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:50482 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751127AbaFPMzP (ORCPT ); Mon, 16 Jun 2014 08:55:15 -0400 Content-Disposition: inline In-Reply-To: <35FD53F367049845BC99AC72306C23D1029A27656A34@CNBJMBX05.corpusers.net> Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: "Wang, Yalin" Cc: "'linux-mmc@vger.kernel.org'" , "'linux-arch-owner@vger.kernel.org'" On Thu, Jun 05, 2014 at 04:40:02AM +0100, Wang, Yalin wrote: > Hi Will, > > Thanks for your point out very much , > I see your meaning , > And I do a try , > But Seems it can just work when you register a > Perf event with a NULL callback function, > > https://git.kernel.org/cgit/linux/kernel/git/will/linux.git/tree/arch/arm/kernel/hw_breakpoint.c#n758 > > i don't know why it design like this? That's so that ptrace users can deal with the stepping themselves, which is expected by programs such as GDB. Also, not all ARM CPUs have mismatch breakpoints (e.g. ARMv6), so software emulation is required there. Will