From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759872AbZBMQ01 (ORCPT ); Fri, 13 Feb 2009 11:26:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752872AbZBMQ0T (ORCPT ); Fri, 13 Feb 2009 11:26:19 -0500 Received: from e23smtp05.au.ibm.com ([202.81.31.147]:41391 "EHLO e23smtp05.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752661AbZBMQ0S (ORCPT ); Fri, 13 Feb 2009 11:26:18 -0500 Date: Fri, 13 Feb 2009 20:23:01 +0530 From: "K.Prasad" To: Ingo Molnar Cc: Andrew Morton , Alan Stern , Roland McGrath , richardj_moore@uk.ibm.com, jason.wessel@windriver.com Subject: [Patch 00/10] Hardware Breakpoint interfaces Message-ID: <20090213145301.GA31546@in.ibm.com> Reply-To: prasad@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ingo, Please find the patches that introduce interfaces to access Hardware Breakpoint (or watchpoint) registers and an arch-specific implementation for x86/x86_64 architecture. The patches have been re-based to -tip tree (commit 4e3bae758b552d6bd094fb36e78a4d738cb42257) A short description of the framework and interfaces is provided below. Some of the details will be specific to x86/x86_64 architecture and may vary depending upon the support provided by the target processor. Kindly accept these patches to become a part of -tip tree. Description ------------- The Hardware Breakpoint registers can be used for tracing changes to a variable or data location (even I/O ports in x86/x86_64) and will be extremely helpful in debugging problems such as memory corruption. While these registers have been used by user-space debuggers for long (through 'ptrace' syscalls), Kgdb exploited them for kernel-space addresses. The proposed framework, introduces interfaces to use them directly on both user- and kernel-space addresses apart from arbitrating requests from various such users for the limited number of registers. The interfaces are: int register_kernel_hw_breakpoint(struct hw_breakpoint *); void unregister_kernel_hw_breakpoint(struct hw_breakpoint *bp); int register_user_hw_breakpoint(struct task_struct *tsk, struct hw_breakpoint *bp); void unregister_user_hw_breakpoint(struct task_struct *tsk, struct hw_breakpoint *bp); The 'struct hw_breakpoint' will be the anchor data-structure containing all the necessary information such as name or address, type, length, priority and pointers to handler functions (some of which are arch-specific). More information about the role of each field, the handler functions and their return values can be found in the descriptive comments preceding these functions and in "include/asm-generic/hw_breakpoint.h". While (un)register_user_hw_breakpoint() isn't exported yet, its worker-routine __register_user-hw_breakpoint() is used by ptrace syscall for all breakpoint register requirements. For the kernel-space, a simple use case to trace 'write' operations on a kernel variable can be found in samples/hw_breakpoint/data_breakpoint.c. In the current patchset, support is provided only for read and read-write breakpoints on data locations, which can be later expand to include instruction and I/O breakpoints for x86/x86_64. There is pending integration with 'KGDB' without which mutual exclusion between them (KGDB and HW breakpoint use through above interfaces) needs to be observed. Thanks, K.Prasad