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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id C73CEC433F5 for ; Wed, 16 Mar 2022 14:30:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=nfcTQTQos83Y6Z0qjGEmExP6urM3XfVCzW6KPvHF+D8=; b=d9B2n1v3/pUyK+ rkWWWlUoeM2W3EHNp+gKgH4SJG+3hT0cNGOFnB8T3sZIKjs3f/a1nIM2Kcc3rCyMjAuRNTMiH+OCE Vdn1Qr94cHsUTx4T7Ps/TtDpyOXWNVXlkZRnI2Nkw5AbLSeRjOk17nrQLh0BrYNvcRFN/pYlhpZ60 Les8myegAnHcqUiQu/x0C7v7gcn9oGFTQzprNmo5oMye/O59LwoNhQ3hsFggZAG/AnRW03mkqm7SI DyhxnE8T6YBqSwo3/+WMKEtan8sjvO/lAERxEGNu+lgfbxb5MTH3+It4tdZKXq5/93fbU0uFxveRb 8DKlmjAYW9jEOkUxChqg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nUUeH-00DGaN-Rn; Wed, 16 Mar 2022 14:29:13 +0000 Received: from dfw.source.kernel.org ([2604:1380:4641:c500::1]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1nUUeE-00DGZi-1a for linux-arm-kernel@lists.infradead.org; Wed, 16 Mar 2022 14:29:11 +0000 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 1154B6154D; Wed, 16 Mar 2022 14:29:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1F33EC340E9; Wed, 16 Mar 2022 14:29:07 +0000 (UTC) Date: Wed, 16 Mar 2022 10:29:05 -0400 From: Steven Rostedt To: Wang ShaoBo Cc: , , , , , , , , , , Peter Zijlstra Subject: Re: [RFC PATCH -next v2 0/4] arm64/ftrace: support dynamic trampoline Message-ID: <20220316102905.3e3b5358@gandalf.local.home> In-Reply-To: <20220316100132.244849-1-bobo.shaobowang@huawei.com> References: <20220316100132.244849-1-bobo.shaobowang@huawei.com> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220316_072910_221110_16B3D9A7 X-CRM114-Status: GOOD ( 21.88 ) 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, 16 Mar 2022 18:01:28 +0800 Wang ShaoBo wrote: > This implements dynamic trampoline in ARM64, as reference said, we > complete whole design of supporting long jump in dynamic trampoline: > > .text section: > funcA: | funcA(): funcB():| > `-> +-----+ | | ... mov x9 | > | ... | | | adrp <- bl <> | > | nop | | | mov > | nop | | | br x16 ---+ > funcB | nop | | | ftrace_(regs_)caller_tramp: > `-> +-----+ | `--> +---------------------+ > | nop | | | ... | > | nop | | ftrace callsite +---------------------+ > | ... | | `-----> | PLT entry: | > | nop | | | adrp | > | nop | | | add | > funcC: | nop | | ftrace graph callsite | br x16 | > `-> +-----+ | `-----> +---------------------+ > | nop | | | ... | > | nop | | +---------------------+ > > But there is still a tricky problem that is how to adjust tracing ip, > waiting to be solved: > > For ARM64, somecases there may be extra instructions inserted into the > head of tracable functions(but not all) by compiler, for instance BTI[1]. > > This dump vmlinux with CONFIG_BTI=y: > > (1) function gic_handle_irq has bti in its head, so we adjust rec->ip+=5 to last nop > ffffffc0080100e0: d53cd042 mrs x2, tpidr_el2 > ... > ffffffc0080100f0: d503201f nop //__mcount_loc tells the rec->ip > ffffffc0080100f4: d503201f nop > ffffffc0080100f8: d503201f nop > > ffffffc0080100fc : > ffffffc0080100fc: d503245f bti c > ffffffc008010100: d503201f nop > ffffffc008010104: d503201f nop //we adjust origin rec->ip+5 to here > ffffffc008010108: d503233f paciasp > (2) name_to_dev_t.part.0 do not has bti in its head, so we should adjust rec->ip+=4 to last nop > ffff8000080137d4: d503201f nop > ffff8000080137d8: d503201f nop > ffff8000080137dc: d503201f nop > > ffff8000080137e0 : > ffff8000080137e0: d503201f nop > ffff8000080137e4: d503201f nop > ffff8000080137e8: d503233f paciasp > > So at this time we have no idea to identify rec->ip for each tracable function. This looks like the same issue that Peter Zijlstra is handling for IBT on x86, which I think can be useful for you too. https://lore.kernel.org/all/20220308153011.021123062@infradead.org/ Specifically this patch: https://lore.kernel.org/all/20220308154318.227581603@infradead.org/ Which modifies the ftrace_location() to return the rec->ip if you pass in the ip of the function and kallsyms returns that the ip passed in has an offset of zero. -- Steve > > we are looking forward to follow-up discussions. > > References: > [1] https://developer.arm.com/documentation/100076/0100/a64-instruction-set-reference/a64-general-instructions/bti > [2] https://lore.kernel.org/linux-arm-kernel/20200109142736.1122-1-cj.chengjian@huawei.com/ > > Cheng Jian (4): > arm64: introduce aarch64_insn_gen_load_literal > arm64/ftrace: introduce ftrace dynamic trampoline entrances > arm64/ftrace: support dynamically allocated trampolines > arm64/ftrace: implement long jump for dynamic trampolines > > arch/arm64/Makefile | 2 +- > arch/arm64/include/asm/ftrace.h | 10 +- > arch/arm64/include/asm/insn.h | 6 + > arch/arm64/include/asm/module.h | 9 + > arch/arm64/kernel/entry-ftrace.S | 88 ++++++-- > arch/arm64/kernel/ftrace.c | 366 ++++++++++++++++++++++++++++--- > arch/arm64/kernel/module-plts.c | 50 +++++ > arch/arm64/lib/insn.c | 49 +++++ > 8 files changed, 532 insertions(+), 48 deletions(-) > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel