Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936649AbXLQVx1 (ORCPT ); Mon, 17 Dec 2007 16:53:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763033AbXLQVxN (ORCPT ); Mon, 17 Dec 2007 16:53:13 -0500 Received: from mx1.redhat.com ([66.187.233.31]:43699 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761518AbXLQVxL (ORCPT ); Mon, 17 Dec 2007 16:53:11 -0500 Message-ID: <4766EFA8.9070907@redhat.com> Date: Mon, 17 Dec 2007 16:52:40 -0500 From: Masami Hiramatsu User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Harvey Harrison CC: Srikar Dronamraju , Ingo Molnar , LKML , Maneesh Soni , srinivasa@in.ibm.com, Jim Keniston , Ananth N Mavinakayanahalli , Masami Hiramatsu , Rusty Lynch , Masami Hiramatsu , Keshavamurthy Anil S Subject: Re: FInal kprobes rollup patches References: <1197708350.898.87.camel@brick> <20071215085015.GA9720@elte.hu> <1197709442.898.97.camel@brick> <20071215131204.GE9720@elte.hu> <20071217142235.GA21379@linux.vnet.ibm.com> <1197919234.23402.5.camel@brick> <4766E9FC.7050101@redhat.com> <1197927385.23402.41.camel@brick> In-Reply-To: <1197927385.23402.41.camel@brick> X-Enigmail-Version: 0.95.5 Content-Type: text/plain; charset=ISO-2022-JP Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2334 Lines: 64 Hi Harvey, Harvey Harrison wrote: > On Mon, 2007-12-17 at 16:28 -0500, Masami Hiramatsu wrote: >> Hi Harvey, >> If you mention about a relative jump which is inserted by >> resume_execution(), I think you might misunderstand that relative jump. >> >> The size of that relative jump, which will be embedded by kprobe-booster, is >> 5-bytes(not 1 byte). So it needs 5 bytes space. >> And we decided not to expand MAX_INSN_SIZE when we developed the booster. >> The reasons are: >> - it is supplemental feature(just accelerating kprobes), if we have no space, >> we can disable it. >> - 5 bytes are big enough compared with 15(=MAX_INSN_SIZE) >> - the lengths of most of instructions are less than 10 bytes. >> >> Additionally, MAX_INSN_SIZE is used in kernel/kprobes.c to allocate an >> instruction buffer which will be assigned to p->ainsn.insn. Since the >> instruction buffer size is MAX_INSN_SIZE, you can not copy instructions >> more than MAX_INSN_SIZE. >> >> BTW, in my patch, I unified MAX_INSN_SIZE to bigger one(16). >> I think it is enough for us. >> > > I went with 15 in mine, I thought it made the code a little more > readable, but I will defer if you think 16 is better. If you want me > to send the whole series to you, let me know. Before porting, could you tell me what differences are important to you? We can discuss about it. > I just sent out a series of 4 patches equivalent to your patches 1-4/6 > but based on my already unified kprobes.c/h, You may want to check your > handling of restored registers in trampoline_probe_handler which I found > when rebasing yours on top of my cleanups. Not sure if this is > important, but it was a difference I found. > > X86_32: > regs->cs = __KERNEL_CS | get_kernel_rpl(); > > yours: > regs->cs = __KERNEL_CS; Because of kretprobe's compatibility, on x86-32 cs should be set rpl(). But get_kernel_rpl() does not exist on x86-64. Thanks, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division e-mail: mhiramat@redhat.com, masami.hiramatsu.pt@hitachi.com -- 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/