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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,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 E58BCC433ED for ; Mon, 10 May 2021 18:09:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B306A611C2 for ; Mon, 10 May 2021 18:09:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232156AbhEJSKG (ORCPT ); Mon, 10 May 2021 14:10:06 -0400 Received: from mx2.suse.de ([195.135.220.15]:45148 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230357AbhEJSKG (ORCPT ); Mon, 10 May 2021 14:10:06 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 5C4F9ADDC; Mon, 10 May 2021 18:09:00 +0000 (UTC) Date: Mon, 10 May 2021 20:08:58 +0200 From: Michal =?iso-8859-1?Q?Such=E1nek?= To: Martin KaFai Lau Cc: Nathan Chancellor , Jiri Slaby , Jiri Olsa , dwarves@vger.kernel.org, Arnaldo Carvalho de Melo , Andrii Nakryiko , bpf@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH v2 dwarves] btf: Remove ftrace filter Message-ID: <20210510180858.GI12700@kitsune.suse.cz> References: <20210506205622.3663956-1-kafai@fb.com> <20210508050321.2qrmkzq7zjpphqo7@kafai-mbp.dhcp.thefacebook.com> <20210508105301.GD12700@kitsune.suse.cz> <20210510180059.tz527zrb6bcqjrl7@kafai-mbp.dhcp.thefacebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20210510180059.tz527zrb6bcqjrl7@kafai-mbp.dhcp.thefacebook.com> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, May 10, 2021 at 11:00:59AM -0700, Martin KaFai Lau wrote: > On Sat, May 08, 2021 at 12:53:01PM +0200, Michal Suchánek wrote: > > On Fri, May 07, 2021 at 10:03:21PM -0700, Martin KaFai Lau wrote: > > > On Thu, May 06, 2021 at 07:54:37PM -0700, Nathan Chancellor wrote: > > > > On Thu, May 06, 2021 at 01:56:22PM -0700, Martin KaFai Lau wrote: > > > > > BTF is currently generated for functions that are in ftrace list > > > > > or extern. > > > > > > > > > > A recent use case also needs BTF generated for functions included in > > > > > allowlist. In particular, the kernel > > > > > commit e78aea8b2170 ("bpf: tcp: Put some tcp cong functions in allowlist for bpf-tcp-cc") > > > > > allows bpf program to directly call a few tcp cc kernel functions. Those > > > > > kernel functions are currently allowed only if CONFIG_DYNAMIC_FTRACE > > > > > is set to ensure they are in the ftrace list but this kconfig dependency > > > > > is unnecessary. > > > > > > > > > > Those kernel functions are specified under an ELF section .BTF_ids. > > > > > There was an earlier attempt [0] to add another filter for the functions in > > > > > the .BTF_ids section. That discussion concluded that the ftrace filter > > > > > should be removed instead. > > > > > > > > > > This patch is to remove the ftrace filter and its related functions. > > > > > > > > > > Number of BTF FUNC with and without is_ftrace_func(): > > > > > My kconfig in x86: 40643 vs 46225 > > > > > Jiri reported on arm: 25022 vs 55812 > > > > > > > > > > [0]: https://lore.kernel.org/dwarves/20210423213728.3538141-1-kafai@fb.com/ > > > > > > > > > > Cc: Andrii Nakryiko > > > > > Cc: Jiri Olsa > > > > > Signed-off-by: Martin KaFai Lau > > > > > > > > This fixes an issue with Fedora's s390x config that CKI noticed: > > > > > > > > https://groups.google.com/g/clang-built-linux/c/IzthpckBJvc/m/MPWGDmXiAwAJ > > > > > > > > Tested-by: Nathan Chancellor # build > > > Thanks all for reviewing and testing. > > > > > > In my cross compile ppc64 test, it does not solve the issue. > > > The problem is the tcp-cc functions (e.g. "cublictcp_*") > > > are not STT_FUNC in ppc64, so they are not collected in collect_function(). > > > The ".cubictcp_*" is STT_FUNC though. > > > > > > Since only the x86 (64 and 32) bpf jit can call these tcp-cc functions now > > > and there is no usage for adding them to .BTF_ids for other ARCHs, > > > I have post a patch to limit them to x86: > > > https://lore.kernel.org/bpf/20210508005011.3863757-1-kafai@fb.com/ > > > > That's probably not the way to go. If function symbols start with a dot > > in ppc64 elfv1 abi then pahole should learn to add a dot for ppc64 elfv1 > > abi. > > > > Or we can build ppc64 BE using the elfv2 abi and depend on elfv2 abi for > > BTF on ppc64. The patch for enabling elfv2 for BE is currently under > > discussion and I have the patch that adds the dependency ready as well. > ic. I just learned the elfv2/LE vs elfv1/BE difference in ppc64. > elfv2 BE ppc64 support is on its way, so it is better to have DEBUG_INFO_BTF > depending on the ppc64-elfv2 related kconfig(s) instead of making an exception > handling in pahole. > > If you have the BTF ppc64-elfv2 dependency patch ready, does it make > sense to land this patch first independent of the ppc64 elfv2/BE > effort? It kind of depends on the result of the config option name bikeshedding so it has to be merged after. Thanks Michal