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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1F126C27C76 for ; Wed, 25 Jan 2023 21:37:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236334AbjAYVhA (ORCPT ); Wed, 25 Jan 2023 16:37:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34702 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236147AbjAYVhA (ORCPT ); Wed, 25 Jan 2023 16:37:00 -0500 Received: from mail-pf1-x430.google.com (mail-pf1-x430.google.com [IPv6:2607:f8b0:4864:20::430]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 136A51BE5 for ; Wed, 25 Jan 2023 13:36:59 -0800 (PST) Received: by mail-pf1-x430.google.com with SMTP id z3so14369520pfb.2 for ; Wed, 25 Jan 2023 13:36:59 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20210112.gappssmtp.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=tRBRtRNX/F1vOSBKhU+3xdFKMEaN2ZI+XOBv7Dgi33A=; b=SJ1UQkilc+cXJsjB41rirabpwgipNi1sNFJoGiWYfOVtKbfE1WmT7SboZChsjfXpgG LKxLqrzCwSRBLjm4tVYr/YCuLPm3HFduaMfjeD0bUVPxupwMufsho3TEif62HeW360qJ ZQ+3n8qgh6c2qm+Z3I6w00ebSHBZfl+zHXiDbWYWNtTTb3VHHBRsoN7KavrOTCJaX/D5 x5rLF2Mi7JPYTqvNrVvvW192s1e/AQha3DrOzIaYdeuYHwbcfEHEk62bsCymlizEyz5u ccZ27W5J+XX+a7N1W0ZOfo382iuN0Neh4+WrtLhjV7WQnldm+XueGY25orv05HMBZqH7 VnPg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=tRBRtRNX/F1vOSBKhU+3xdFKMEaN2ZI+XOBv7Dgi33A=; b=TNdfkpcm3RJe/4Y2wKm1W4uP8BOpbF0War3rlzTmkGON15ndspBoOuCJgnIAtKt2r8 pJdmed1F7J6ETN91ZkMOG85GkM7kDbsmZD0cDnzcpOxTtLWTdaXqC9MzJ5TChG12sQPT xz6G5gZbct22v+Rk43joTEUhr8FcqtzIkY7aPwBJjfJsbhhIwGRgPFLtBO4Z9Atyiqli pvZZ6kW+vfdJJYEUnXHVXj/3HuUSUXK5cnuV4M5kEnzdI8Jgp9d4MgUlPYH/B+GKJW6X rR4eNQXbOFKFmIuy9+gk2Zn1VMk/Srd8odYHiLpgl+xeRIsKRgLB7zOITqrGrDh3UC0U udAw== X-Gm-Message-State: AFqh2krg5iQwyjyEOVza7N8ZroAepY9YU/53YmeTK0lKHdZHqZ7OZEpg 6F6KnVpVErLrRFONoUrnpU9t9bjOCt6GVG77 X-Google-Smtp-Source: AMrXdXt2nPyG/wsEGP3IwZANB0Y7ch0Mg36kft0pKpcPc7CP44mpeEbhs+V3UsQDnb4f5e3AlkFqlw== X-Received: by 2002:aa7:85d5:0:b0:582:6732:ee0b with SMTP id z21-20020aa785d5000000b005826732ee0bmr53985841pfn.28.1674682617841; Wed, 25 Jan 2023 13:36:57 -0800 (PST) Received: from telecaster ([2620:10d:c090:500::4:92fd]) by smtp.gmail.com with ESMTPSA id s10-20020aa78d4a000000b0058e08796e98sm4067408pfe.196.2023.01.25.13.36.57 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Jan 2023 13:36:57 -0800 (PST) Date: Wed, 25 Jan 2023 13:36:56 -0800 From: Omar Sandoval To: linux-debuggers@vger.kernel.org Subject: Re: Linux Kernel Debugging Tools Monthly Meeting on Wednesday, January 25th Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-debuggers@vger.kernel.org On Mon, Jan 23, 2023 at 12:10:50PM -0800, Omar Sandoval wrote: > Hello! The first Linux Kernel Debugging Tools meeting of 2023 is this > Wednesday, January 25th at 11:30 AM Pacific time. We've been having > these for a few years as a forum to discuss development of Linux kernel > debugging tools like drgn, crash, and more. Now that we have this > mailing list, I figured it'd be nice to publicize it more widely. If you > would like to attend, please email me offlist. > > The agenda so far is roughly: > > - Is there a good way to iterate over all online `struct page`s? See > https://github.com/osandov/drgn/pull/228 > - Pending drgn work > - Pluggable symbol finder from Stephen > - Slab helpers from Imran > - Dealing with `DW_OP_entry_value` and `DW_TAG_call_site_parameter`. See > https://github.com/osandov/drgn/issues/233 > - Call for drgn/contrib scripts: > https://github.com/osandov/drgn/tree/main/contrib > > Please reply with anything else you'd like to add to the agenda. > > Thanks! > Omar Here are notes from the meeting: - There doesn't seem to be a better way currently to get the constants needed for iterating sparsemem. We should bite the bullet and make them enums upstream. This won't be too hard, but it'll be a bit tedious since they're defined separately for each architecture. And it will only solve it for new kernels. - Stephen Brennan is working on making symbol finding pluggable (as opposed to only from ELF symbols). This will make it possible to find debug info for kernel modules from `kallsyms` without loading the module debug info, for BPF functions, and more. - Imran Khan has a bunch of new slab helpers, and on top of those, helpers for validating that the slab metadata makes sense, to help with debugging memory corruptions. Some of these require `slub_debug` to be enabled. - Ross Zwisler is working on setting aside the vmcore from the kdump kernel for the full kernel to access. This works on x86 by marking it in the e820 table, but Arm will need something different (maybe in device tree). - I'll merge the workaround for `DW_OP_entry_value` from https://github.com/osandov/drgn/issues/233, but there's potentially more we can do to actually recover the value when `DW_TAG_call_site_parameter` is available. - Jeremy Carin, a teaching assistant at Columbia University's Operating Systems course, is looking for good resources to teach beginners kernel debugging. - We weren't aware of anything great that already exists, but we had some ideas for the future. Specifically, I would love to have step-by-step walkthroughs through kernel bugs with the core dumps and debug info available for download so that you can follow along with drgn. - I may or may not be around for the meeting next month since I have a baby coming around then. Thanks everyone!