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 4B8EDECAAD3 for ; Sun, 4 Sep 2022 06:18:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229872AbiIDGS3 (ORCPT ); Sun, 4 Sep 2022 02:18:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58696 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229478AbiIDGS3 (ORCPT ); Sun, 4 Sep 2022 02:18:29 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 697DD474FE; Sat, 3 Sep 2022 23:18:27 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id AB6DD60DE3; Sun, 4 Sep 2022 06:18:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E8918C433D6; Sun, 4 Sep 2022 06:18:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1662272306; bh=/suyhRp9htNZ81ks9sWUMbjb7xBK3OarUmyTbyGexNE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=A2OgtPlKClwMv/Q+gv0/o3j6NgvEXUGIigr3Ika3eRo3Q60dEqwxoO8i4699+0Gb3 3dAZ70P+B64g5VQDcdqeyp2RcGJu7KAOxYmoj8lX6xGve56HXeA+HZOmEYaYBnEMts p8IeXjWZ5NqyvM873vWTbdowznbjqai+u3H1QfPE= Date: Sun, 4 Sep 2022 08:18:22 +0200 From: Greg KH To: Arnaldo Carvalho de Melo Cc: Jiri Olsa , stable@vger.kernel.org, bpf@vger.kernel.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Yonghong Song Subject: Re: [PATCH bpf v2] bpf: Add config for skipping BTF enum64s Message-ID: References: <20220828233317.35464-1-yakoyoku@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Sat, Sep 03, 2022 at 11:13:45AM -0300, Arnaldo Carvalho de Melo wrote: > Em Sat, Sep 03, 2022 at 07:26:58AM +0200, Greg KH escreveu: > > On Fri, Sep 02, 2022 at 06:51:00PM +0200, Jiri Olsa wrote: > > > On Sun, Aug 28, 2022 at 08:33:17PM -0300, Martin Rodriguez Reboredo wrote: > > > > After the release of pahole 1.24 some people in the dwarves mailing list > > > > notified issues related to building the kernel with the BTF_DEBUG_INFO > > > > option toggled. They seem to be happenning due to the kernel and > > > > resolve_btfids interpreting btf types erroneously. In the dwarves list > > > > I've proposed a change to the scripts that I've written while testing > > > > the Rust kernel, it simply passes the --skip_encoding_btf_enum64 to > > > > pahole if it has version 1.24. > > > > > > > > v1 -> v2: > > > > - Switch to off by default and remove the config option. > > > > - Send it to stable instead. > > > > > > hi, > > > we have change that needs to go to stable kernels but does not have the > > > equivalent fix in Linus tree > > > > Why isn't it also relevant in Linus's tree? > > See below. > > > > what would be the best way to submit it? > > > > Submit it here and document the heck out of why this isn't in Linus's > > tree, what changes instead fixed it there, and so on. Look in the > > archives for examples of how this is done, one recent one that I can > > think of is here: > > https://lore.kernel.org/r/20220831191348.3388208-1-jannh@google.com > > > > > the issue is that new 'pahole' will generate BTF data that are not supported > > > by older kernels, so we need to add --skip_encoding_btf_enum64 option to > > > stable kernel's scripts/pahole-flags.sh to generate proper BTF data > > > > > > we got complains that after upgrading to latest pahole the stable kernel > > > compilation fails > > > > And what is happening in Linus's tree for this same issue? > > So, BTF_KIND_ENUM64 is a new BTF tag, one that is not accepted by older > kernels, but is accepted by the BPF verifier on Linus' tree. > > Its about avoiding having a pahole command line with lots of > --enable-new-feature-foo for new stuff with the default producing the > most recent BTF spec. > > One way to documenting it: if you update pahole, then please use > --skip_encoding_FOO for these new FOO features on kernels where those > aren't supported. > > So this isn't a backport from a fix on Linus' tree, as both the older > pahole that doesn't encode BTF_KIND_ENUM64 and the new one, that encodes > it by default, work with Linus' tree. > > Does this violates the stable@ rules? Not really, if it fixes an issue for those kernels when using newer tools, that's fine. Just document it well like you did here. thanks, greg k-h