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 F386FC433EF for ; Tue, 10 May 2022 09:11:27 +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=bukAcr0MsjXNVj0TTyNQLkvdfzb0WLa3sNCZKTWZRoU=; b=YJcuGRTF5zL7YL iOi75cUiY5vjnrOC7gHUjjXDLvPwhc2mV5UHbw7N/jRN0If56oBRd50iDh064Tp964xU34LCBmqlA kzeAILGTVMUYhDrAdJZ88AFOLMwYJZlZycZSPJJlS5TJEoo64fEdiq7v5l/E+vUwYHuc+TeEi4tJP AEEPTPgRQQxU4vQtS4/NAxOU/P13mGM6GYLm3W3QGjPzZ8F7R4noi2MN6oBLmVpMG8ZnK9LsoLWjp GZrIGjkzz2j9x5rsG50m5y7dG3ZsEf/E8njlqGNtpnFGBdi/gs1jO3I4aguP067OKZkCPIpUbOjqL 6Yh80t5p8BuS3Ix4F7fA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1noLss-000khC-9M; Tue, 10 May 2022 09:10:22 +0000 Received: from dfw.source.kernel.org ([139.178.84.217]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1noLsp-000kg7-Br for linux-arm-kernel@lists.infradead.org; Tue, 10 May 2022 09:10:20 +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 5F68F614BD; Tue, 10 May 2022 09:10:18 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 267ACC385A6; Tue, 10 May 2022 09:10:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1652173817; bh=GXpVDYbkF84LLdJ5bx4YwYoSn9Krmcs/u8uVEyFBHiY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=oLb653JNx2KBVbvxGYK7oIFvppbFBTPIYSJD85hFi0sCGzZ1akOP6cPOLeqVNVLjf GLBNMceSMifw+ciRgtuIiZn0keibYMP1pMVYnR8HY4fjLkGHijzfBfdPgUWwDBn4b9 0/3/bvyL6OXPJgxD5cn7/81QNgOSCuEXc+ceYs8g7dGbVfE04bi2zMd2Gs7DGNDWkc 6fYkMlfUr9ckP7s1qG1kHlkcT3c+wVO5K2B5vS7zwIL2kAlgi2mu6phelLWTwM6mVZ uVvdtlvolPNog6AqZ+S11H1LQsVrxO5YHSTo/n0do/5r45zuhHxbk4qC+56zWo55qN 58h8zSW774MTg== Date: Tue, 10 May 2022 18:10:12 +0900 From: Masami Hiramatsu To: Steven Rostedt Cc: Mark Rutland , Wang ShaoBo , cj.chengjian@huawei.com, huawei.libin@huawei.com, xiexiuqi@huawei.com, liwei391@huawei.com, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, will@kernel.org, zengshun.wu@outlook.com, Jiri Olsa Subject: Re: [RFC PATCH -next v2 3/4] arm64/ftrace: support dynamically allocated trampolines Message-Id: <20220510181012.d5cba23a2547f14d14f016b9@kernel.org> In-Reply-To: <20220509142203.6c4f2913@gandalf.local.home> References: <20220421100639.03c0d123@gandalf.local.home> <20220421114201.21228eeb@gandalf.local.home> <20220421130648.56b21951@gandalf.local.home> <20220422114541.34d71ad9@gandalf.local.home> <20220426174749.b5372c5769af7bf901649a05@kernel.org> <20220505121538.04773ac98e2a8ba17f675d39@kernel.org> <20220509142203.6c4f2913@gandalf.local.home> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; 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-20220510_021019_528800_4D6E5350 X-CRM114-Status: GOOD ( 27.64 ) 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 Hi Steve, On Mon, 9 May 2022 14:22:03 -0400 Steven Rostedt wrote: > On Thu, 5 May 2022 12:15:38 +0900 > Masami Hiramatsu wrote: > > > OK. But my interest is that the ftrace on arm64 can provide a limited > > access to registers via pt_regs or not. I don't mind the contained values > > so much because in the most case, 'users' will (most likely) access to the > > ARGs via BPF or tracefs (and we can just warn users if they try to access > > the registers which is not saved.) But if the arm64 ftrace only provides > > a special data structure, arch-independent code must have 2 different access > > code. That is inefficient. That is my concern. > > IOW, I'm interested in interface abstraction. > > Note, ftrace now has a ftrace_regs structure that is passed to the > callbacks for the function tracer. > > It then has an arch dependent helper function ftrace_get_regs(fregs), that > returns a pt_regs from the fregs only if the fregs has a full pt_regs to > return. If not, it returns NULL. > > This was suggested by both Peter Zijlstra and Thomas Gleixner when I > introduced FTRACE_WITH_ARGS, where all functions can now get the arguments > from fregs, but not the full pt_regs. Hmm, I thought the ftrace_get_regs() is the all-or-nothing interface, or is there any way to get the arguments from fregs? > If a ftrace_ops has the REGS flag set > (using ftrace_regs_caller), the ftrace_get_regs(fregs) will return the > pt_regs, or it will return NULL if ftrace_regs_caller was not used. > > This way the same parameter can provide full pt_regs or a subset, and have > an generic interface to tell the difference. If it can provide a partial (subset of) pt_regs, that could be good for me too, since at least kprobe-events on ftrace can check the traced register is in the subset or not and reject it if it doesn't saved. Thank you, -- Masami Hiramatsu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel