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=-15.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE,URIBL_BLOCKED,USER_AGENT_SANE_1 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 841D3C3E8C5 for ; Wed, 18 Nov 2020 17:53:32 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 B98CB24905 for ; Wed, 18 Nov 2020 17:53:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fIq9T6B0" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B98CB24905 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49502 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kfRe6-0006va-Gc for qemu-devel@archiver.kernel.org; Wed, 18 Nov 2020 12:53:30 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:47688) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kfRcX-0005bu-DV for qemu-devel@nongnu.org; Wed, 18 Nov 2020 12:51:53 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:58597) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kfRcT-0006dl-CR for qemu-devel@nongnu.org; Wed, 18 Nov 2020 12:51:52 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1605721906; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=BP7NwhKIZgKnhn5++mmFpz44kFmRv2peXMYx1/8TJc4=; b=fIq9T6B0Ylc/1L3n3dFazoeDWK/c6gbzQkp1sFnt5TF8CUH+JEp2tSY96/P8ac1M+OkfAf c11LRC2vDSkfGD8uOBLhBPLitKDBEwdJDpyC0+Xz1/lov1T/9nMm3RYQMAjBH8EMmly9ug C/NuhgFY9W57F5tvMe2IJi6sdW0D4JI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-396-BrgmlWAeP3uw4b4RS2r1dg-1; Wed, 18 Nov 2020 12:51:42 -0500 X-MC-Unique: BrgmlWAeP3uw4b4RS2r1dg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0DB91879A08; Wed, 18 Nov 2020 17:51:41 +0000 (UTC) Received: from redhat.com (ovpn-115-41.ams2.redhat.com [10.36.115.41]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 685A760C05; Wed, 18 Nov 2020 17:51:31 +0000 (UTC) Date: Wed, 18 Nov 2020 17:51:28 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Stefan Hajnoczi Subject: Re: [PATCH] trace: use STAP_SDT_V2 to work around symbol visibility Message-ID: <20201118175128.GH229461@redhat.com> References: <20201118174809.686094-1-stefanha@redhat.com> MIME-Version: 1.0 In-Reply-To: <20201118174809.686094-1-stefanha@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/17 19:41:43 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Peter Maydell , qemu-devel@nongnu.org, rjones@redhat.com, fche@redhat.com, kraxel@redhat.com, wcohen@redhat.com, mrezanin@redhat.com, ddepaula@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Nov 18, 2020 at 05:48:09PM +0000, Stefan Hajnoczi wrote: > QEMU binaries no longer launch successfully with recent SystemTap > releases. This is because modular QEMU builds link the sdt semaphores > into the main binary instead of into the shared objects where they are > used. The symbol visibility of semaphores is 'hidden' and the dynamic > linker prints an error during module loading: > > $ ./configure --enable-trace-backends=dtrace --enable-modules ... > ... > Failed to open module: /builddir/build/BUILD/qemu-4.2.0/s390x-softmmu/../block-curl.so: undefined symbol: qemu_curl_close_semaphore > > The long-term solution is to generate per-module dtrace .o files and > link them into the module instead of the main binary. > > In the short term we can define STAP_SDT_V2 so /usr/bin/dtrace produces > an .o file with 'default' symbol visibility instead of 'hidden'. This > workaround is small and easier to merge for QEMU 5.2. > > Cc: Daniel P. Berrangé > Cc: wcohen@redhat.com > Cc: fche@redhat.com > Cc: kraxel@redhat.com > Cc: rjones@redhat.com > Cc: mrezanin@redhat.com > Cc: ddepaula@redhat.com > Signed-off-by: Stefan Hajnoczi > --- > trace/meson.build | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/trace/meson.build b/trace/meson.build > index d5fc45c628..52be7c5b2c 100644 > --- a/trace/meson.build > +++ b/trace/meson.build > @@ -44,7 +44,7 @@ foreach dir : [ '.' ] + trace_events_subdirs > trace_dtrace_o = custom_target(fmt.format('trace-dtrace', 'o'), > output: fmt.format('trace-dtrace', 'o'), > input: trace_dtrace, > - command: [ 'dtrace', '-o', '@OUTPUT@', '-G', '-s', '@INPUT@' ]) > + command: [ 'dtrace', '-DSTAP_SDT_V2', '-o', '@OUTPUT@', '-G', '-s', '@INPUT@' ]) I'm a little concerned that we're not also setting this macro before including the generated trace.h headers, because those headers do check this STAP_SDT_V1 symbol. Currently the generated headers have same code for V2 and V3 (the default), so we won't break, but I'm concerned we could break if they introduce a future V4 and that impacts the generated headers. So I think the safe thing todo is set -DSTAP_SDT_V2 as a global compile arg for QEMU too, so all trace.h files see the symbol that matches the trace.o files Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|