From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755543AbaHHCHj (ORCPT ); Thu, 7 Aug 2014 22:07:39 -0400 Received: from mail7.hitachi.co.jp ([133.145.228.42]:39465 "EHLO mail7.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754999AbaHHCHh (ORCPT ); Thu, 7 Aug 2014 22:07:37 -0400 Message-ID: <53E430E2.3040709@hitachi.com> Date: Fri, 08 Aug 2014 11:07:30 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Wang Nan Cc: Ananth N Mavinakayanahalli , Anil S Keshavamurthy , davem@davemloft.net, Russell King , Will Deacon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, peifeiyue@huawei.com, Li Zefan Subject: Re: [RFC PATCH] kprobes: arm: enable OPTPROBES for arm 32 References: <1407223697-74911-1-git-send-email-wangnan0@huawei.com> <53E1B2A0.1040807@hitachi.com> <53E1CA11.1030206@huawei.com> <53E323D1.8020209@hitachi.com> <53E42704.3090909@huawei.com> In-Reply-To: <53E42704.3090909@huawei.com> 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 (2014/08/08 10:25), Wang Nan wrote: > On 2014/8/7 14:59, Masami Hiramatsu wrote: >> (2014/08/06 15:24), Wang Nan wrote: >>>>> + >>>>> +static void >>>>> +optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) >>>>> +{ >>>>> + unsigned long flags; >>>>> + >>>>> + regs->ARM_pc = (unsigned long)op->kp.addr; >>>>> + regs->ARM_ORIG_r0 = ~0UL; >>>>> + >>>>> + >>>>> + local_irq_save(flags); >>>>> + /* >>>>> + * This is possible if op is under delayed unoptimizing. >>>>> + * We need simulate the replaced instruction. >>>>> + */ >>>>> + if (kprobe_disabled(&op->kp)) { >>>>> + struct kprobe *p = &op->kp; >>>>> + op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); >>>>> + } else { >>>>> + kprobe_handler(regs); >>>>> + } >>>> >>>> You don't need brace "{}" for one statement. >>>> By the way, why don't you call opt_pre_handler()? >>>> >>> >>> I use kprobe_handler because it handles instruction emulation. >>> >>> In addition, I'm not very sure whether skipping the complex checks >>> in kprobe_handler() is safe or not. >> >> That seems to do same thing on x86. Then you should do something like >> the optimized_callback() on x86 as below. >> >> static void >> optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) >> { >> struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); >> unsigned long flags; >> >> local_irq_save(flags); >> if (kprobe_running()) { >> kprobes_inc_nmissed_count(&op->kp); > > In this case we still need a singlestep, right? Ah, right! and if the singlestep requires setting up the regs->ARM_pc, we also do that before this check. So the right code will be; static void optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) { struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); unsigned long flags; local_irq_save(flags); /* Save skipped registers */ regs->ARM_pc = (unsigned long)op->kp.addr; regs->ARM_ORIG_r0 = ~0UL; if (kprobe_running()) kprobes_inc_nmissed_count(&op->kp); else { __this_cpu_write(current_kprobe, &op->kp); kcb->kprobe_status = KPROBE_HIT_ACTIVE; opt_pre_handler(&op->kp, regs); __this_cpu_write(current_kprobe, NULL); } op->kp.ainsn.insn_singlestep(op->kp.opcode, &op->kp.ainsn, regs); local_irq_restore(flags); } Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com