Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759563AbZCWTWE (ORCPT ); Mon, 23 Mar 2009 15:22:04 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755852AbZCWTVw (ORCPT ); Mon, 23 Mar 2009 15:21:52 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:46104 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754881AbZCWTVw (ORCPT ); Mon, 23 Mar 2009 15:21:52 -0400 Date: Mon, 23 Mar 2009 15:21:49 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: "K.Prasad" cc: Ingo Molnar , Linux Kernel Mailing List , Andrew Morton , Benjamin Herrenschmidt , Frederic Weisbecker , Maneesh Soni , Roland McGrath , Steven Rostedt Subject: Re: [Patch 01/11] Introducing generic hardware breakpoint handler interfaces In-Reply-To: <20090323190328.GA23426@in.ibm.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1340 Lines: 37 On Tue, 24 Mar 2009, K.Prasad wrote: > > > Ok. Will do something like: > > > return (va <= (TASK_SIZE - (hw_breakpoint_length * word_size))); > > > > What is the purpose of word_size here? The breakpoint length should be > > specified in bytes, not words. > > > > Don't forget that that in arch_check_va_in_kernelspace() you need to > > check both for values that are too low and values that are too high > > (they overflow and wrap around back to a user address). > > > > While I understand the user-space checking using the length of the HW > Breakpoint, I don't really see how I can check for an upper-bound for > kernel-space virtual addresses. Most usage in the kernel only checks for > the address >= TASK_SIZE (while they check for add + len if the length > of the memory is known). I will be glad to have any suggestions in this > regard. Isn't that exactly the check you need to implement? addr >= TASK_SIZE && (addr + len) >= TASK_SIZE, or perhaps better, addr >= TASK_SIZE && (addr + len) >= addr. In this case you _do_ know the length of the breakpoint. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/