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,USER_AGENT_SANE_1 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 B4942C4708C for ; Fri, 28 May 2021 06:24:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8832B613D1 for ; Fri, 28 May 2021 06:24:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230127AbhE1G0S (ORCPT ); Fri, 28 May 2021 02:26:18 -0400 Received: from smtp-out2.suse.de ([195.135.220.29]:38708 "EHLO smtp-out2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229753AbhE1G0R (ORCPT ); Fri, 28 May 2021 02:26:17 -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-out2.suse.de (Postfix) with ESMTPS id A03F91FD2E; Fri, 28 May 2021 06:24:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1622183082; 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=7O16xmQehx80n7fVVBeuMQ81Au9qauhcCf9P3KVa6HM=; b=dGed2PMDS6s5Tjfp2/y9GXu3gsBolu2eTmGGc1lndrnGRe/9lu9xconJyR/NWp+vFTyHia ogcHIXMAiR/mnZBv7Z+x6U2SHwqKo8mXjsmntR9KL/ABoDbN3Ic0Nq80OTIoqsRafLvdhD aP4owL9u2LALkxnsBpQ0pUzQjhF319Q= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1622183082; 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=7O16xmQehx80n7fVVBeuMQ81Au9qauhcCf9P3KVa6HM=; b=djEs2zWPnsnI0YOR+Ds9bPwCWxyQOF1MFxYLghSYNHo0acdrwkzj7uJBsLeo0xP6RBe6aa iAxG7WR/wwDO51AA== Received: from director2.suse.de (director2.suse-dmz.suse.de [192.168.254.72]) by imap.suse.de (Postfix) with ESMTPSA id 8570611A98; Fri, 28 May 2021 06:24:42 +0000 (UTC) Date: Fri, 28 May 2021 08:24:41 +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: <20210528062441.GJ8544@kitsune.suse.cz> References: <20210524234222.278676-1-andrii@kernel.org> <20210527152758.GI8544@kitsune.suse.cz> 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: bpf@vger.kernel.org On Thu, May 27, 2021 at 01:47:41PM -0300, Arnaldo Carvalho de Melo wrote: > Em Thu, May 27, 2021 at 12:38:38PM -0300, Arnaldo Carvalho de Melo escreveu: > > Em Thu, May 27, 2021 at 05:27:58PM +0200, Michal Suchánek escreveu: > > > 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. > > > > Ok, I'm test building with torvalds/master, will try with linux-next > > afterwards, > > I build and booted torvalds/master, all seems to work, now moving to > linux-next. [ 9s] /usr/bin/qemu-kvm -nodefaults -no-reboot -nographic -vga none -cpu host -object rng-random,filename=/dev/random,id=rng0 -device virtio-rng-pci,rng=rng0 -runas qemu -net none -kernel /var/cache/obs/worker/root_2/.mount/boot/kernel -initrd /var/cache/obs/worker/root_2/.mount/boot/initrd -append root=/dev/disk/by-id/virtio-0 rootfstype=ext4 rootflags=noatime ext4.allow_unsupported=1 mitigations=off panic=1 quiet no-kvmclock elevator=noop nmi_watchdog=0 rw rd.driver.pre=binfmt_misc console=ttyS0 init=/.build/build -m 8192 -drive file=/var/cache/obs/worker/root_2/root,format=raw,if=none,id=disk,cache=unsafe -device virtio-blk-pci,drive=disk,serial=0 -drive file=/var/cache/obs/worker/root_2/swap,format=raw,if=none,id=swap,cache=unsafe -device virtio-blk-pci,drive=swap,serial=1 -serial stdio -chardev socket,id=monitor,server,nowait,path=/var/cache/obs/worker/root_2/root.qemu/monitor -mon chardev=monitor,mode=readline -smp 8 [ 9s] c[?7l[2J[0mSeaBIOS (version rel-1.14.0-0-g155821a-rebuilt.opensuse.org) [ 15s] Booting from ROM..c[?7l[2J### VM INTERACTION END ### [ 15s] 2nd stage started in virtual machine [ 15s] machine type: x86_64 [ 15s] Linux version: 5.13.0-rc3-next-2[ 5.210478] sysrq: Changing Loglevel [ 15s] 0210526-2.g3bd43[ 5.211566] sysrq: Loglevel set to 4 [ 15s] 9f-vanilla #1 SMP Thu May 27 18:27:17 UTC 2021 (3bd439f) [ 15s] Increasing log level from now on... [ 15s] Enable sysrq operations [ 15s] Setting up swapspace version 1, size = 2 GiB (2097147904 bytes) [ 15s] no label, UUID=6e22796c-6df5-4859-a291-24acde2e92e5 [ 15s] swapon: /dev/vdb: found signature [pagesize=4096, signature=swap] [ 15s] swapon: /dev/vdb: pagesize=4096, swapsize=2097152000, devsize=2097152000 [ 15s] swapon /dev/vdb [ 15s] WARNING: udev not running, creating extra device nodes [ 15s] logging output to //.build.log... next-20210527 does not build becuase of missing symbol but next-20210526 built with the patched pahole boots. Tested-by: Michal Suchánek Thanks Michal > > > Thanks, > > > > - Arnaldo > > > > > 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 > > > > -- > > > > - Arnaldo > > -- > > - Arnaldo