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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 72815C2B9F4 for ; Mon, 14 Jun 2021 16:07:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4355B61378 for ; Mon, 14 Jun 2021 16:07:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234471AbhFNQJs (ORCPT ); Mon, 14 Jun 2021 12:09:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233543AbhFNQJr (ORCPT ); Mon, 14 Jun 2021 12:09:47 -0400 Received: from mail-ej1-x633.google.com (mail-ej1-x633.google.com [IPv6:2a00:1450:4864:20::633]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 32264C061574 for ; Mon, 14 Jun 2021 09:07:29 -0700 (PDT) Received: by mail-ej1-x633.google.com with SMTP id l1so17481277ejb.6 for ; Mon, 14 Jun 2021 09:07:29 -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:references:mime-version :content-disposition:in-reply-to; bh=MNFWmm34MZytbVprgUqS0jda1g7ZVugrknZ1TlYtDUQ=; b=dXOpEReFQg7wxCEciDmPS8hg+xqA1WcwdZEuSGxmkOK9XEgFlPkXNXXZgJ/3NJsbMp Wg+q2rExZaTxTDSEzdg7Opcj14+Is2NjQX546+BRiVwbmsFEaiJFFNhyglTnVyRY/lwC 4tWZs/2fMAq7L/3T1qKt6XPJdyf5GYyoxdDaHb8emgFi3yJJL/XPq2AkP65Dwt08r0rl W5XLzU1tjknpMp9uXty/svjU1SOX49Ijsb7QjsoVnDLeGenKbIXN2395pr43Nfy7oipD yjfUL9h9dbdlEIPkuZ6jcg+nS8TUv29a5xwP5l2GamHvnFvrB034UC7ajFvq5yaSeyQ4 waLA== 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:references :mime-version:content-disposition:in-reply-to; bh=MNFWmm34MZytbVprgUqS0jda1g7ZVugrknZ1TlYtDUQ=; b=H/hz5oyac1bIDwVa1ya1xZS+YE4BFIf24HKmF9hImsA3Rfovj0QwASBBebRgTJqH7U X0zTIQXaf2+PprTU8s6u6FC4IyL9nUDBjIevMUYYKX4PUOh/c5wvYhCoFT8NnxBmBUbp gGqok6Bt9PsmLh3+MxqZ6R+69Jvb2xlTKKIGSdEVQWZOjnH1BExMsglEaH9uKzOkgWr1 qERD+TGOHh9dIZWDNTlOsxB38nlvgxXC4Zrz/BxfxwdnzTlD9divzFci7oe7Yk/LLY3v 5alCXa1ZvJLxAg4BAKbDAMexmreclSED/s1L+AacwMS/06YtJyzBRN/WKCgGiDELSVSB fDKg== X-Gm-Message-State: AOAM5324BrNeQe+yLmRh7wF0ZQikn23zYiBN5ussjiCvMt+sw04kqDkW kqSLnBhGzel2RfxTsEuyEA== X-Google-Smtp-Source: ABdhPJwX3iEKNIeEi0O2uxmQbWz1orJGi2aByHnwYZUCUgIPB6464igySWPOIiWEDysOY7JTQvG9Vw== X-Received: by 2002:a17:906:1815:: with SMTP id v21mr15849724eje.376.1623686847826; Mon, 14 Jun 2021 09:07:27 -0700 (PDT) Received: from localhost.localdomain ([46.53.252.135]) by smtp.gmail.com with ESMTPSA id e22sm9503078edu.35.2021.06.14.09.07.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Jun 2021 09:07:27 -0700 (PDT) Date: Mon, 14 Jun 2021 19:07:25 +0300 From: Alexey Dobriyan To: dhowells@redhat.com Cc: linux-afs@lists.infradead.org, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] afs: fix tracepoint string placement with built-in AFS Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org ping! Currently "perf record -e [tracepoint]" is unusable if AFS is builtin. On Fri, May 28, 2021 at 01:04:46AM +0300, Alexey Dobriyan wrote: > I was adding custom tracepoint to the kernel, grabbed full F34 kernel > .config, disabled modules and booted whole shebang as VM kernel. > > Then did > > perf record -a -e ... > > It crashed: > > general protection fault, probably for non-canonical address 0x435f5346592e4243: 0000 [#1] SMP PTI > CPU: 1 PID: 842 Comm: cat Not tainted 5.12.6+ #26 > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014 > RIP: 0010:t_show+0x22/0xd0 > > Then reproducer was narrowed to > > # cat /sys/kernel/tracing/printk_formats > > Original F34 kernel with modules didn't crash. > > So I started to disable options and after disabling AFS everything > started working again. > > The root cause is that AFS was placing char arrays content into a section > full of _pointers_ to strings with predictable consequences. > > Non canonical address 435f5346592e4243 is "CB.YFS_" which came from > CM_NAME macro. > > The fix is to create char array and pointer to it separatedly. > > Steps to reproduce: > > CONFIG_AFS=y > CONFIG_TRACING=y > > # cat /sys/kernel/tracing/printk_formats > > Signed-off-by: Alexey Dobriyan (SK hynix) > --- > > fs/afs/cmservice.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > --- a/fs/afs/cmservice.c > +++ b/fs/afs/cmservice.c > @@ -30,8 +30,9 @@ static void SRXAFSCB_TellMeAboutYourself(struct work_struct *); > static int afs_deliver_yfs_cb_callback(struct afs_call *); > > #define CM_NAME(name) \ > - char afs_SRXCB##name##_name[] __tracepoint_string = \ > - "CB." #name > + const char afs_SRXCB##name##_name[] = "CB." #name; \ > + static const char *_afs_SRXCB##name##_name __tracepoint_string =\ > + afs_SRXCB##name##_name > > /* > * CB.CallBack operation type