From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 54569C54EE9 for ; Fri, 23 Sep 2022 01:25:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230314AbiIWBZD (ORCPT ); Thu, 22 Sep 2022 21:25:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51938 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229691AbiIWBZB (ORCPT ); Thu, 22 Sep 2022 21:25:01 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AF51D107DF0; Thu, 22 Sep 2022 18:24:59 -0700 (PDT) Received: from kwepemi500012.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4MYZ971SjTzWh5r; Fri, 23 Sep 2022 09:20:59 +0800 (CST) Received: from [10.67.110.108] (10.67.110.108) by kwepemi500012.china.huawei.com (7.221.188.12) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Fri, 23 Sep 2022 09:24:56 +0800 Message-ID: <55c32279-1a96-0a31-ca2b-ae4e34365625@huawei.com> Date: Fri, 23 Sep 2022 09:24:55 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: [PATCH V2 3/3] arm64/kprobe: Optimize the performance of patching single-step slot To: Will Deacon CC: , , , , , , , , , , , , References: <20220913033454.104519-1-liaochang1@huawei.com> <20220913033454.104519-4-liaochang1@huawei.com> <20220922133850.GC12095@willie-the-truck> From: "liaochang (A)" In-Reply-To: <20220922133850.GC12095@willie-the-truck> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.110.108] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemi500012.china.huawei.com (7.221.188.12) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/9/22 21:38, Will Deacon 写道: > On Tue, Sep 13, 2022 at 11:34:54AM +0800, Liao Chang wrote: >> Single-step slot would not be used until kprobe is enabled, that means >> no race condition occurs on it under SMP, hence it is safe to pacth ss >> slot without stopping machine. >> >> Signed-off-by: Liao Chang >> --- >> arch/arm64/kernel/probes/kprobes.c | 5 ++--- >> 1 file changed, 2 insertions(+), 3 deletions(-) >> >> diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c >> index d1d182320245..5902e33fd3b6 100644 >> --- a/arch/arm64/kernel/probes/kprobes.c >> +++ b/arch/arm64/kernel/probes/kprobes.c >> @@ -44,11 +44,10 @@ post_kprobe_handler(struct kprobe *, struct kprobe_ctlblk *, struct pt_regs *); >> static void __kprobes arch_prepare_ss_slot(struct kprobe *p) >> { >> kprobe_opcode_t *addr = p->ainsn.api.insn; >> - void *addrs[] = {addr, addr + 1}; >> - u32 insns[] = {p->opcode, BRK64_OPCODE_KPROBES_SS}; >> >> /* prepare insn slot */ >> - aarch64_insn_patch_text(addrs, insns, 2); >> + aarch64_insn_write(addr, p->opcode); >> + aarch64_insn_write(addr + 1, BRK64_OPCODE_KPROBES_SS); >> >> flush_icache_range((uintptr_t)addr, (uintptr_t)(addr + MAX_INSN_SIZE)); > > Hmm, so it looks like prior to your change we were doing the cache > maintebnance twice: once in aarch64_insn_patch_text() from stop machine > context and then again in the flush_icache_range() call above. > > I suppose the cleanest thing would be to drop the flush_icache_range() > call and then use aarch64_insn_patch_text_nosync() instead of > aarch64_insn_write() in your change. OK，I will improve it in next version, thanks. > > Will > . -- BR, Liao, Chang