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=-17.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 3B4DDC4708B for ; Thu, 27 May 2021 15:28:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1B3E5613BA for ; Thu, 27 May 2021 15:28:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236002AbhE0P3d (ORCPT ); Thu, 27 May 2021 11:29:33 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:56874 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235993AbhE0P3d (ORCPT ); Thu, 27 May 2021 11:29:33 -0400 Received: from imap.suse.de (imap-alt.suse-dmz.suse.de [192.168.254.47]) (using TLSv1.2 with cipher ECDHE-ECDSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 5CFA82190B; Thu, 27 May 2021 15:27:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1622129279; h=from:from:reply-to: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=YmugS6FPrOG42kEGuD/GJW6gSUg5RqZ4LgvC0qWJI30=; b=bG5uEsa/CZlv1fMBsX5f1mZBlLA/XoyLJsbKNGjkmtlHIzFEhyDaFwWhOGzY+FjBx1+Zs3 kbb4IwYdvc60mIWXcccRaFDm+YJpl1/gAcQHzgAn+pYMC5xbcVzLDPrhxTzBdWzQLFpxk9 pipedj6BqviJRDCIJEt4ko/yPgYi3lM= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1622129279; h=from:from:reply-to: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=YmugS6FPrOG42kEGuD/GJW6gSUg5RqZ4LgvC0qWJI30=; b=CWhbYhqEmo7AdIg7GodhC2XDDljoO1pWYnhorj0HgyS00jp28GWcbTffPYy4JZOExZu2C7 ACOYUiLjsYgNyPCQ== Received: from director2.suse.de (director2.suse-dmz.suse.de [192.168.254.72]) by imap.suse.de (Postfix) with ESMTPSA id 4A93B11A98; Thu, 27 May 2021 15:27:59 +0000 (UTC) Date: Thu, 27 May 2021 17:27:58 +0200 From: Michal =?iso-8859-1?Q?Such=E1nek?= To: Arnaldo Carvalho de Melo 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: <20210527152758.GI8544@kitsune.suse.cz> 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: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: dwarves@vger.kernel.org Hello, On Thu, May 27, 2021 at 11:58:24AM -0300, Arnaldo Carvalho de Melo wrote: > 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: This is the first time I see this patch. Given that linux-next does not build for me at the moment I don't think I will test it soon. Thanks Michal > > 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