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 2C365C38145 for ; Sat, 3 Sep 2022 14:13:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231127AbiICONw (ORCPT ); Sat, 3 Sep 2022 10:13:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229463AbiICONv (ORCPT ); Sat, 3 Sep 2022 10:13:51 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D5F7958517; Sat, 3 Sep 2022 07:13:49 -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 4AC126151E; Sat, 3 Sep 2022 14:13:49 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8490CC433C1; Sat, 3 Sep 2022 14:13:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1662214428; bh=wR96nJJd4WNj9UMkwxs6pSZVS/BHL8f9p4HAQZWJjJ4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Z3KeN3h26tWcHPiPLDiRO4iFIQGbenqR+bbtXn+Gm+0Mj+oZjU9/kFZRypspfbkXu M07a/V/D2PNHdKU1SowaN+ZbmpawwguKXZ+xnmJnihSw3ITOR/wMz+y7N4LjroLGEh RXFY2pv6jxQoJnnx0k0tiicFmdOshTpjVf4EuETNLVIT5VPpIUDnq7IpDuEXxzDpD/ wOFgFnOddWCi6B2Zoff/qcDqLE+hER+qRV5rGnraBrvB9H2u81jECvO8wOKsEi0//c lGkfTCz5Zhw832mHKjDB4ZA9tdIkExmy/TAjm9uD97oNRPpguFbAYf5u5B4rmwVBhF u+vDa7vg8Kfiw== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 0CE6F404A1; Sat, 3 Sep 2022 11:13:46 -0300 (-03) Date: Sat, 3 Sep 2022 11:13:45 -0300 From: Arnaldo Carvalho de Melo To: Greg KH 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: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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? - Arnaldo