From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19667 invoked by alias); 3 Jul 2019 19:29:03 -0000 Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org Received: (qmail 19659 invoked by uid 89); 3 Jul 2019 19:29:03 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-5.3 required=5.0 tests=AWL,BAYES_00,GIT_PATCH_1,HTML_MESSAGE,KAM_SHORT,RCVD_IN_DNSWL_NONE autolearn=ham version=3.3.1 spammy=lightweight, H*c:alternative, shipping, talk X-HELO: mail-vs1-f43.google.com Received: from mail-vs1-f43.google.com (HELO mail-vs1-f43.google.com) (209.85.217.43) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 03 Jul 2019 19:29:01 +0000 Received: by mail-vs1-f43.google.com with SMTP id v6so504456vsq.4 for ; Wed, 03 Jul 2019 12:29:01 -0700 (PDT) MIME-Version: 1.0 From: Aaron Merey Date: Wed, 03 Jul 2019 19:29:00 -0000 Message-ID: Subject: debuginfo server progress update To: systemtap@sourceware.org, elfutils-devel@sourceware.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-IsSubscribed: yes X-SW-Source: 2019-q3/txt/msg00003.txt.bz2 Hello, The debuginfo server, a web service that offers lightweight on-demand lookups of debuginfo-related data, along with its elfutils client have begun to take shape so I want to provide an update on where we currently are in its development and how to use it. We plan on shipping debuginfo server with elfutils and it is currently available on the branch 'fche/dbgserver' of the elfutils git repo. The http web server itself is able to scan a directory tree for any debuginfo, executable and source files and index them by build-id. The elfutils client hooks into libdwfl and provides a fallback so that if the library is not able to locate a debuginfo file, the client, if enabled, will attempt to query debuginfo servers for debuginfo containing a particular build-id. As an example, suppose we are trying to trace some program with systemtap. One of the stap probes we want to run requires DWARF debuginfo but the executable has been stripped of this information and the corresponding debuginfo file is not in any of the default directories that stap checks. $ stap -e 'probe process("/path/to/exec").function("*") { [...] }' semantic error: while resolving probe point: identifier 'process' at t.stp:1:7 source: probe process("/path/to/exec").function("*") { semantic error: no match (similar functions: exit, open, textdomain, tfind, dup) Systemtap uses elfutils to locate and read debuginfo files, so it is able to make use of debuginfo server's elfutils client. First we run debuginfo server and point it to the directory containing the stripped debuginfo. $ dbgserver -vvv -p 8002 -F ~/debuginfo_dir & [Tue Jul 2 15:00:37] (20459/20462): file-path scanning /home/amerey/debuginfo_dir [Tue Jul 2 15:00:37] (20459/20459): Started http server on port 8002, database path /home/amerey/.dbgserver.sqlite [Tue Jul 2 15:00:37] (20459/20462): fts traversing /home/amerey/debuginfo_dir [Tue Jul 2 15:00:37] (20459/20462): fts traversing /home/amerey/debuginfo_dir/debuginfo [Tue Jul 2 15:00:37] (20459/20462): recorded buildid=3D0a0cd15e690a378ec77359bb2eeb76ea0f8d67f8 \ file=3D/home/amerey/debuginfo_dir/debuginfo mtime=3D1561060856 as executable and debuginfo [...] In order to enable the elfutils client, there must be a $DBGSERVER_URLS environment variable containing at least one URL of a debuginfo server (multiple URLs should be separated by spaces). When we run stap again, elfutils will query the debuginfo server for debuginfo with the build-id of the executable. $ export DBGSERVER_URLS=3Dlocalhost:8002 $ stap -v -e 'probe process("/path/to/exec").function("*") { [...] }' [...] Pass 5: starting run This time systemtap successfully acquires the debuginfo and begins running the probe. Although in this example everything is running locally, the server and the debuginfo could just as well be on a remote host. Debuginfo server development is ongoing. Some of the features we have planned include a gdb client that could query debuginfo servers for debuginfo or source code and the ability for the server to automatically search rpms for any of the files requested by a client. We also are planning a talk/demo at GNU Cauldron this September in Montr=C3=A9al, Canada ( https://gcc.gnu.org/wiki/cauldron2019). Hopefully this helped give you a sense of how to use debuginfo server, where it is in its development, and what is to come. Feedback is always appreciated! Aaron Merey