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=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 E655AC433E2 for ; Thu, 16 Jul 2020 13:07:09 +0000 (UTC) Received: from lists.lttng.org (lists.lttng.org [167.114.26.123]) (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 A2DA72065F for ; Thu, 16 Jul 2020 13:07:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.lttng.org header.i=@lists.lttng.org header.b="TsmW4oXj" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A2DA72065F Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=lists.lttng.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lttng-dev-bounces@lists.lttng.org Received: from lists-lttng01.efficios.com (localhost [IPv6:::1]) by lists.lttng.org (Postfix) with ESMTP id 4B6vfh6rqkz1XfL; Thu, 16 Jul 2020 09:07:08 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=lists.lttng.org; s=default; t=1594904829; bh=1s8LsmFVdtV+UqEQvBRPDaYYvLiFrueigAoO7qm0eDg=; h=Date:To:In-Reply-To:References:Subject:List-Id:List-Unsubscribe: List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc: From; b=TsmW4oXjfurr9YDLDBjmR6hJyUBNI/JVr3YT0k/72ici9etZlbJd4hEoKlE+AKI35 i+10LEXkh0vGt40hIvJZgysGCzMo4e/dlt09ITszkSok4tv/kTHyMjiiL4Uz4vEDP7 TX5eUMfQghB2+1XL7LP759c/yJjNVtusibtjcRzjBahlYizjhso2S+LRJ9PbW7MPWP y0XZRxW8a6ZtRP9AkAZ4/WQhf8NpZwl/GR7Nb8qubfvqiGv5Aunshk2AfKsnr0jQVT MN8VXyytHnRAgvkFy5Y8uUpspQSM6ko4RhlESO7+UDmxZTfFNvhlDRNj/QfbtCQDEn v1gp3p6ebrCpg== Received: from mail.ut.ac.ir (mail.ut.ac.ir [80.66.177.10]) by lists.lttng.org (Postfix) with ESMTPS id 4B6X6H0bYqz1XvG for ; Wed, 15 Jul 2020 18:26:14 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.ut.ac.ir (Postfix) with ESMTP id 333C21DADD1; Thu, 16 Jul 2020 02:56:00 +0430 (+0430) Received: from mail.ut.ac.ir ([127.0.0.1]) by localhost (mail.ut.ac.ir [127.0.0.1]) (amavisd-new, port 10024) with LMTP id XRKwxLQuqr2s; Thu, 16 Jul 2020 02:55:59 +0430 (+0430) Received: from mail.ut.ac.ir (mail.ut.ac.ir [194.225.0.10]) by mail.ut.ac.ir (Postfix) with ESMTP id 2B3F31DADD0; Thu, 16 Jul 2020 02:55:59 +0430 (+0430) MIME-Version: 1.0 Date: Thu, 16 Jul 2020 02:55:59 +0430 To: Steven Rostedt In-Reply-To: <20200715174858.4698803c@oasis.local.home> References: <20200715142849.0bfe909a@oasis.local.home> <83963025.14828.1594838718290.JavaMail.zimbra@efficios.com> <98de6fe15a816d8f06ba3d5df0f10540@ut.ac.ir> <20200715174858.4698803c@oasis.local.home> Message-ID: <46b174cf30872f07a08f97be1d7eb514@ut.ac.ir> X-Sender: ahmadkhorrami@ut.ac.ir User-Agent: Roundcube Webmail/1.3.6 X-Mailman-Approved-At: Thu, 16 Jul 2020 09:07:01 -0400 Subject: Re: [lttng-dev] Capturing User-Level Function Calls/Returns X-BeenThere: lttng-dev@lists.lttng.org X-Mailman-Version: 2.1.31 Precedence: list List-Id: LTTng development list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: ahmadkhorrami via lttng-dev Reply-To: ahmadkhorrami Cc: linux-trace-users-owner@vger.kernel.org, linux-trace-users , lttng-dev , Namhyung Kim Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: lttng-dev-bounces@lists.lttng.org Sender: "lttng-dev" Message-ID: <20200715222559.BguzAr1zC-5n1Eq2uHpARdrgL2-qa8vzkFXLBLqUDA8@z> So, the only barrier to the user-level implementation is the problem with instruction sizes. That's an enlightening point. Thanks for the detailed answer! Thanks everybody specially Steven and Mathieu. Regards. On 2020-07-16 02:18, Steven Rostedt wrote: > On Thu, 16 Jul 2020 02:09:50 +0430 > ahmadkhorrami wrote: > >> Hi Steven and Mathieu, >> Firstly, many thanks! This method seems to be the most efficient >> method. >> But, IIUC, what you suggest requires source code compilation. I need >> an >> efficient dynamic method that, given the function address, captures >> its >> occurrence and stores some information from the execution context. Is >> there anything better than Uprobes perhaps with no trap into the >> kernel? >> Why do we need traps? >> Regards. > > Without recompiling, how would that be implemented? > > You would need to insert a jump on top of code, and still be able to > preserve that code. What a trap does, is to insert a int3, that will > trap into the kernel, it would then emulate the code that the int3 was > on, and also call some code that can trace the current state. > > To do it in user land, you would need to find way to replace the code > at the location you want to trace, with a jump to the tracing > infrastructure, that will also be able to emulate the code that the > jump was inserted on top of. As on x86, that jump will need to be 5 > bytes long (covering 5 bytes of text to emulate), where as a int3 is a > single byte. > > Thus, you either recompile and insert nops where you want to place your > jumps, or you trap using int3 that can do the work from within the > kernel. > > -- Steve _______________________________________________ lttng-dev mailing list lttng-dev@lists.lttng.org https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev