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=-16.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, 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 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 91F62C43460 for ; Tue, 27 Apr 2021 11:38:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6BBA16100B for ; Tue, 27 Apr 2021 11:38:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235428AbhD0LjU (ORCPT ); Tue, 27 Apr 2021 07:39:20 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:51220 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237966AbhD0LjK (ORCPT ); Tue, 27 Apr 2021 07:39:10 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619523507; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=hnFEYH2ir5X1i0lkoWLMXh/bSKWjZ05zbFcheXKiHLo=; b=UCvnqM9aQjc2HLzch22OwuTZgKj7liZ7Fq7cVD7B0+G8geuGd1CVXqzum+H7EE1ZJbbZwW pyT3PUKwK1BOjkbHHNB720Xtai1ldDsRtH6qjg6kRbOsQeNdR5B4pQCgkEl16jJXFrf0ej /g0prMApisl3OrHq7jhfZnlkthY+5c8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-265-dG4WkvbnO2q6rE-GMwNdBg-1; Tue, 27 Apr 2021 07:38:24 -0400 X-MC-Unique: dG4WkvbnO2q6rE-GMwNdBg-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 37BD480ED8B; Tue, 27 Apr 2021 11:38:23 +0000 (UTC) Received: from krava (unknown [10.40.192.237]) by smtp.corp.redhat.com (Postfix) with SMTP id 6835F62AF7; Tue, 27 Apr 2021 11:38:21 +0000 (UTC) Date: Tue, 27 Apr 2021 13:38:20 +0200 From: Jiri Olsa To: Andrii Nakryiko Cc: Martin KaFai Lau , Jiri Olsa , dwarves@vger.kernel.org, Arnaldo Carvalho de Melo , bpf , Kernel Team , Andrii Nakryiko Subject: Re: [PATCH dwarves] btf: Generate btf for functions in the .BTF_ids section Message-ID: References: <20210423213728.3538141-1-kafai@fb.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Apr 26, 2021 at 04:26:11PM -0700, Andrii Nakryiko wrote: > On Fri, Apr 23, 2021 at 2:37 PM 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 > > functions are specified under an ELF section .BTF_ids. The symbols > > in this ELF section is like __BTF_ID__func____[digit]+. > > For example, __BTF_ID__func__cubictcp_init__1. 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. > > > > pahole can generate BTF for those kernel functions if it knows they > > are in the allowlist. This patch is to capture those symbols > > in the .BTF_ids section and generate BTF for them. > > > > Cc: Andrii Nakryiko > > Signed-off-by: Martin KaFai Lau > > --- > > I wonder if we just record all functions how bad that would be. Jiri, > do you remember from the time you were experimenting with static > functions how much more functions we'd be recording if we didn't do > ftrace filtering? hum, I can't find that.. but should be just matter of removing that is_ftrace_func check if we decided to do that, maybe we could add some bit indicating that the function is traceable? it would save us check with available_filter_functions file jirka > > > btf_encoder.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++--- > > libbtf.c | 10 ++++ > > libbtf.h | 2 + > > 3 files changed, 142 insertions(+), 6 deletions(-) > > > > diff --git a/btf_encoder.c b/btf_encoder.c > > index 80e896961d4e..48c183915ddd 100644 > > --- a/btf_encoder.c > > +++ b/btf_encoder.c > > @@ -106,6 +106,121 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym, > > return 0; > > } > > > > +#define BTF_ID_FUNC_PREFIX "__BTF_ID__func__" > > +#define BTF_ID_FUNC_PREFIX_LEN (sizeof(BTF_ID_FUNC_PREFIX) - 1) > > + > > +static char **listed_functions; > > +static int listed_functions_alloc; > > +static int listed_functions_cnt; > > maybe just use struct btf as a container of strings, which is what you > need here? You can do btf__add_str() and btf__find_str(), which are > both fast and memory-efficient, and you won't have to manage all the > memory and do sorting, etc, etc. > > [...] >