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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=unavailable 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 57322C4707F for ; Thu, 27 May 2021 14:58:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 381FC61186 for ; Thu, 27 May 2021 14:58:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236574AbhE0PAC (ORCPT ); Thu, 27 May 2021 11:00:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:38840 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233563AbhE0PAA (ORCPT ); Thu, 27 May 2021 11:00:00 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 57EC46128D; Thu, 27 May 2021 14:58:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622127507; bh=WKWmt3FGSvjzfL/CX2du+GW3pa/sDXJn59U2jNVd9IM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hlXzuCmH56nds8Lgvodx+rNvBqDtKkQy7UDqVjwlZg0PmyE8ENcsjNK+p567xh0aV LuKvcT7BZpU4CpmgnGv6n0bzOI4rRPkL0xmzwU4K1eC2vSQGtI5Y/RkSHAlcxHIW9k 6uVXGZuJ4INkdyo1r/b7bL44de6TjQeB9gSlLgaqrtz2sC1LGbP8FA3GjPcNvvomI5 5PjYr1etvgPNr6CuCfzWSLPL3NT25optElhBxd6Mq763Z8t+lsvOWmvGH/VMk7aNYH oxTAa8Nepi+z2QPIzK+JaPGMbG/arIzDlDiMdM4Bt+kRIkcE8HGBx0gmK/3uRbnNU+ lmeQRSJg4ZEGA== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 54AD64011C; Thu, 27 May 2021 11:58:24 -0300 (-03) Date: Thu, 27 May 2021 11:58:24 -0300 From: Arnaldo Carvalho de Melo To: Michal =?iso-8859-1?Q?Such=E1nek?= Cc: Andrii Nakryiko , dwarves@vger.kernel.org, bpf@vger.kernel.org, jolsa@kernel.org, kernel-team@fb.com Subject: Re: [PATCH dwarves] btf_encoder: fix and complete filtering out zero-sized per-CPU variables Message-ID: References: <20210524234222.278676-1-andrii@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Em Thu, May 27, 2021 at 11:55:10AM -0300, Arnaldo Carvalho de Melo escreveu: > Em Mon, May 24, 2021 at 04:42:22PM -0700, Andrii Nakryiko escreveu: > > btf_encoder is ignoring zero-sized per-CPU ELF symbols, but the same has to be > > done for DWARF variables when matching them with ELF symbols. This is due to > > zero-sized DWARF variables matching unrelated (non-zero-sized) variable that > > happens to be allocated at the exact same address, leading to a lot of > > confusion in BTF. > > > See [0] for when this causes big problems. > > > [0] https://lore.kernel.org/bpf/CAEf4BzZ0-sihSL-UAm21JcaCCY92CqfNxycHRZYXcoj8OYb=wA@mail.gmail.com/ I also added this: Reported-by: Michal Suchánek Michal, so you tested this patch and verified it fixed the problem? If so please let me know so that I also add: Tested-by: Michal Suchánek Thanks, - Arnaldo > > +++ b/btf_encoder.c > > @@ -550,6 +551,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > > > /* addr has to be recorded before we follow spec */ > > addr = var->ip.addr; > > + dwarf_name = variable__name(var, cu); > > > > /* DWARF takes into account .data..percpu section offset > > * within its segment, which for vmlinux is 0, but for kernel > > @@ -582,11 +584,9 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > * modules per-CPU data section has non-zero offset so all > > * per-CPU symbols have non-zero values. > > */ > > - if (var->ip.addr == 0) { > > - dwarf_name = variable__name(var, cu); > > + if (var->ip.addr == 0) > > if (!dwarf_name || strcmp(dwarf_name, name)) > > continue; > > - } > > > > if (var->spec) > > var = var->spec; > > @@ -600,6 +600,13 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > I just changed the above hunk to be: > > @@ -583,7 +585,6 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > * per-CPU symbols have non-zero values. > */ > if (var->ip.addr == 0) { > - dwarf_name = variable__name(var, cu); > if (!dwarf_name || strcmp(dwarf_name, name)) > continue; > } > > > Which is shorter and keeps the {} around a multi line if block, ok? > > Thanks, applied! > > - Arnaldo -- - Arnaldo