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 X-Spam-Level: X-Spam-Status: No, score=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 27CADC432BE for ; Thu, 5 Aug 2021 09:27:07 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E9EBF61029 for ; Thu, 5 Aug 2021 09:27:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org E9EBF61029 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:Content-Type: Content-Transfer-Encoding:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:CC:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=n2UrnzM6T7M7q88U2I0CkG7nGTPq8Wxg1lgHoulITJE=; b=Sho/Rn5jlYwtR/V+XK9L7MvnvP zoqaQmpyAQwfVmjUfIiIhmekBUlKm70j5maVkocCkk+l/JX0S1HAlC5ocER10LCbTYTkOl92WoQvZ fPVTUXi5jps8A5fgKtKyXMjGcsiE4X0fOfk2OVdmzID0sR/zYZfa0zBCp9j3pgXunJVCwbOJ1r8MD GjOZ5lifwF4mX/Ls8IPE+DJedylwcV1B7U9qB4K+p1DkvL9wPlmsqwySvM/ifkwQDKFI78qGn9HSP 2Cjvtiup/t6VxDvxfz55amTpCAtTkSc2+5DZmBuvBoie/WlHIuXD1X9bDAxSPyjTFlcdZacRbykHA Z723fclg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBZd1-008sm6-BX; Thu, 05 Aug 2021 09:25:27 +0000 Received: from szxga01-in.huawei.com ([45.249.212.187]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1mBZcw-008skf-9S for linux-arm-kernel@lists.infradead.org; Thu, 05 Aug 2021 09:25:24 +0000 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.56]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4GgNQx2lxTzZxK2; Thu, 5 Aug 2021 17:21:45 +0800 (CST) Received: from dggema757-chm.china.huawei.com (10.1.198.199) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Thu, 5 Aug 2021 17:25:19 +0800 Received: from [127.0.0.1] (10.69.38.203) by dggema757-chm.china.huawei.com (10.1.198.199) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Thu, 5 Aug 2021 17:25:19 +0800 Subject: Re: [PATCH v2] arm64: kprobe: Enable OPTPROBE for arm64 To: Masami Hiramatsu , Linuxarm CC: , , , , , , , , , , References: <20210804060209.95817-1-liuqi115@huawei.com> <20210805105401.4acd3217c566b4e3933f355c@kernel.org> From: "liuqi (BA)" Message-ID: Date: Thu, 5 Aug 2021 17:25:17 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20210805105401.4acd3217c566b4e3933f355c@kernel.org> Content-Language: en-GB X-Originating-IP: [10.69.38.203] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggema757-chm.china.huawei.com (10.1.198.199) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210805_022522_736893_E52991D1 X-CRM114-Status: GOOD ( 25.56 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Masami, On 2021/8/5 9:54, Masami Hiramatsu wrote: > On Wed, 4 Aug 2021 14:02:09 +0800 > Qi Liu wrote: > >> This patch introduce optprobe for ARM64. In optprobe, probed >> instruction is replaced by a branch instruction to detour >> buffer. Detour buffer contains trampoline code and a call to >> optimized_callback(). optimized_callback() calls opt_pre_handler() >> to execute kprobe handler. >> >> Limitations: >> - We only support !CONFIG_RANDOMIZE_MODULE_REGION_FULL case to >> guarantee the offset between probe point and kprobe pre_handler >> is not larger than 128MiB. >> >> Performance of optprobe on Hip08 platform is test using kprobe >> example module[1] to analyze the latency of a kernel function, >> and here is the result: >> >> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/kprobes/kretprobe_example.c >> >> kprobe before optimized: >> [280709.846380] do_empty returned 0 and took 1530 ns to execute >> [280709.852057] do_empty returned 0 and took 550 ns to execute >> [280709.857631] do_empty returned 0 and took 440 ns to execute >> [280709.863215] do_empty returned 0 and took 380 ns to execute >> [280709.868787] do_empty returned 0 and took 360 ns to execute >> [280709.874362] do_empty returned 0 and took 340 ns to execute >> [280709.879936] do_empty returned 0 and took 320 ns to execute >> [280709.885505] do_empty returned 0 and took 300 ns to execute >> [280709.891075] do_empty returned 0 and took 280 ns to execute >> [280709.896646] do_empty returned 0 and took 290 ns to execute >> [280709.902220] do_empty returned 0 and took 290 ns to execute >> [280709.907807] do_empty returned 0 and took 290 ns to execute >> >> optprobe: >> [ 2965.964572] do_empty returned 0 and took 90 ns to execute >> [ 2965.969952] do_empty returned 0 and took 80 ns to execute >> [ 2965.975332] do_empty returned 0 and took 70 ns to execute >> [ 2965.980714] do_empty returned 0 and took 60 ns to execute >> [ 2965.986128] do_empty returned 0 and took 80 ns to execute >> [ 2965.991507] do_empty returned 0 and took 70 ns to execute >> [ 2965.996884] do_empty returned 0 and took 70 ns to execute >> [ 2966.002262] do_empty returned 0 and took 80 ns to execute >> [ 2966.007642] do_empty returned 0 and took 70 ns to execute >> [ 2966.013020] do_empty returned 0 and took 70 ns to execute >> [ 2966.018400] do_empty returned 0 and took 70 ns to execute >> [ 2966.023779] do_empty returned 0 and took 70 ns to execute >> [ 2966.029158] do_empty returned 0 and took 70 ns to execute >> >> Signed-off-by: Qi Liu >> >> --- >> >> Changes since V1: >> - Address the comments from Masami, checks for all branch instructions, and >> use aarch64_insn_patch_text_nosync() instead of aarch64_insn_patch_text() >> in each probe. > > Is it safe for the multicore system? If it is safe because it modifies > just one instruction (modifying 32bit in atomic), I understand it. Seems raw_spin_lock_irqsave is used in aarch64_insn_patch_text_nosync() and spinlock could support a protection in multicore system. > BTW, anyway, you should use _nosync() variant in arch_prepare_optimized_kprobe() > too, beacause the optprobe insn buffer is not touched until the probed instruction > is optimized by br. > Yes, sounds resonable. > [...] >> +int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *orig) >> +{ >> + kprobe_opcode_t *code; >> + u32 insn; >> + int ret, i; >> + void *addrs[TMPL_END_IDX]; >> + void *addr; >> + >> + code = get_optinsn_slot(); >> + if (!code) >> + return -ENOMEM; >> + >> + if (!is_offset_in_range((unsigned long)code, >> + (unsigned long)orig->addr + 8)) >> + goto error; >> + >> + if (!is_offset_in_range((unsigned long)code + TMPL_CALL_BACK, >> + (unsigned long)optimized_callback)) >> + goto error; >> + >> + if (!is_offset_in_range((unsigned long)&code[TMPL_RESTORE_END], >> + (unsigned long)op->kp.addr + 4)) >> + goto error; >> + >> + /* Setup template */ >> + for (i = 0; i < TMPL_END_IDX; i++) >> + addrs[i] = code + i; >> + >> + ret = aarch64_insn_patch_text(addrs, optprobe_template_entry, >> + TMPL_END_IDX); > > You should use aarch64_insn_patch_text_nosync() here (and all the > aarch64_insn_patch_text() in this function too), because the insn > buffer must not executed until the probe point is optimized. > aarch64_insn_patch_text() could patch multi instructions to code[] each time and aarch64_insn_patch_text_nosync() could only patch one instruction each time, so maybe aarch64_insn_patch_text() is better here. I'll replace other aarch64_insn_patch_text() in this function. Thanks, Qi >> + if (ret < 0) >> + goto error; >> + >> + /* Set probe information */ >> + addr = code + TMPL_VAL_IDX; >> + insn = (unsigned long long)op & 0xffffffff; >> + aarch64_insn_patch_text(&addr, &insn, 1); >> + >> + addr = addr + 4; >> + insn = ((unsigned long long)op & GENMASK_ULL(63, 32)) >> 32; >> + aarch64_insn_patch_text(&addr, &insn, 1); >> + >> + addr = code + TMPL_CALL_BACK; >> + insn = aarch64_insn_gen_branch_imm((unsigned long)addr, >> + (unsigned long)optimized_callback, >> + AARCH64_INSN_BRANCH_LINK); >> + aarch64_insn_patch_text(&addr, &insn, 1); >> + >> + /* The original probed instruction */ >> + addr = code + TMPL_RESTORE_ORIGN_INSN; >> + insn = orig->opcode; >> + aarch64_insn_patch_text(&addr, &insn, 1); >> + >> + /* Jump back to next instruction */ >> + addr = code + TMPL_RESTORE_END; >> + insn = aarch64_insn_gen_branch_imm( >> + (unsigned long)(&code[TMPL_RESTORE_END]), >> + (unsigned long)(op->kp.addr) + 4, >> + AARCH64_INSN_BRANCH_NOLINK); >> + aarch64_insn_patch_text(&addr, &insn, 1); >> + >> + flush_icache_range((unsigned long)code, >> + (unsigned long)(&code[TMPL_END_IDX])); >> + /* Set op->optinsn.insn means prepared. */ >> + op->optinsn.insn = code; >> + >> + return 0; > > Thank you, > > > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel