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=-4.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 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 AD169C4743C for ; Mon, 14 Jun 2021 13:34:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 87213611CE for ; Mon, 14 Jun 2021 13:34:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234028AbhFNNgY (ORCPT ); Mon, 14 Jun 2021 09:36:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44086 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233394AbhFNNgW (ORCPT ); Mon, 14 Jun 2021 09:36:22 -0400 Received: from mail-lf1-x12a.google.com (mail-lf1-x12a.google.com [IPv6:2a00:1450:4864:20::12a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 972EEC061766; Mon, 14 Jun 2021 06:34:07 -0700 (PDT) Received: by mail-lf1-x12a.google.com with SMTP id bp38so21243163lfb.0; Mon, 14 Jun 2021 06:34:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=y+VpVa/Mc1+kFCgRsz56WptJ2EZlhOZN6aWdeyarFVI=; b=XmuESoouVc/r6kZdVBYkje+JZAMeYXN3l+u2/CEUJmYTVI3rRrGWDATCLHlH/nMhIU AMb9rp/mLhgbE4wwm+vOvADqPpcDIqBVDZq7XxE398qNeKRh0Bi1tVahCS2GEXHLTecG iW9jF4CTmnyjHOi494BGqYZ6fsrG9dEAmh9u8b93W0UMN+6JZdUh/sh1xLljHyaStk5V V6fSbv1IVdlKCheWECR4shY9ltLAdpqyaBYFkoHnZDnUN/GegVZ0RHG0iNF1in9Gj35p n8FJeNI2PrycRv6ZzDLw/k+M7lWkyMtVyDiBTSikaTofkWSFZJ2w+8fxSXnmwEVDwBVG ogOA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=y+VpVa/Mc1+kFCgRsz56WptJ2EZlhOZN6aWdeyarFVI=; b=MqGUbYLRek34gVhU/bamnm24pm2T6pLVv9SFRPf1WJxFXiVNxs+oVGXSBtnz3X3/Jz Ola37a6gRsQjYYoYJ16lL3AyR+Xva5B4F4bSD8ti8lQF9ERPYYYOhNp6j7EN2051+5/p T7GTO3B/1VQl66YXXRJCj+wTvhi/0CgU3+D8dI5u7N/koz4xZAo/hMIeifRKKD3TdTQ7 VkdHWBBCx7/0zS83vm/alovGtF0q8IxdkDl/kn+1YomRtr1JSmZdmP6ujBPuY4g6xFY4 e6RffC7HUhP2Pii/mh3gSnX4zNWzM+hibs2lFh4BxeDLUmK3sOAmZyqGpjMqskSswIZL fsfA== X-Gm-Message-State: AOAM530n1QAFmWS7EQjD0PoKzbVC+62enKVbAaU6IYMmiNVkKYya873o Lb9BBwpOkOeTWZZLADNyuaM= X-Google-Smtp-Source: ABdhPJyAEIRZ7T8Bcy7B3MxB9ivA7zWCG4wfzOrjH8mWXFik1quzXUsOomybWlj9iwugKVYc7WzhnQ== X-Received: by 2002:a05:6512:3d8f:: with SMTP id k15mr12457575lfv.362.1623677645915; Mon, 14 Jun 2021 06:34:05 -0700 (PDT) Received: from localhost.localdomain ([94.103.229.24]) by smtp.gmail.com with ESMTPSA id w24sm1486513lfl.123.2021.06.14.06.34.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Jun 2021 06:34:05 -0700 (PDT) Date: Mon, 14 Jun 2021 16:34:01 +0300 From: Pavel Skripkin To: Dongliang Mu Cc: alex.aring@gmail.com, "David S. Miller" , Jakub Kicinski , linux-kernel , linux-wpan@vger.kernel.org, netdev@vger.kernel.org, stefan@datenfreihafen.org, syzkaller-bugs , syzbot+b80c9959009a9325cdff@syzkaller.appspotmail.com, Dan Carpenter , Greg KH Subject: Re: Suggestions on how to debug kernel crashes where printk and gdb both does not work Message-ID: <20210614163401.52807197@gmail.com> In-Reply-To: References: X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-suse-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, 14 Jun 2021 21:22:43 +0800 Dongliang Mu wrote: > Dear kernel developers, > > I was trying to debug the crash - memory leak in hwsim_add_one [1] > recently. However, I encountered a disgusting issue: my breakpoint and > printk/pr_alert in the functions that will be surely executed do not > work. The stack trace is in the following. I wrote this email to ask > for some suggestions on how to debug such cases? > > Thanks very much. Looking forward to your reply. > Hi, Dongliang! This bug is not similar to others on the dashboard. I spent some time debugging it a week ago. The main problem here, that memory allocation happens in the boot time: > [] kernel_init+0xc/0x1a7 init/main.c:1447 and reproducer simply tries to free this data. You can use ftrace to look at it. Smth like this: $ echo 'hwsim_*' > $TRACE_DIR/set_ftrace_filter would work. With regards, Pavel Skripkin