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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 D7719C433E0 for ; Thu, 28 May 2020 17:24:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AFE3B208DB for ; Thu, 28 May 2020 17:24:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WlEAixXT" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2405508AbgE1RYB (ORCPT ); Thu, 28 May 2020 13:24:01 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:24588 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2405353AbgE1RYA (ORCPT ); Thu, 28 May 2020 13:24:00 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1590686639; 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=b10WE7v1A18G0MJHCfCrgYKCxbH7drfKcQ1AZUdmnb0=; b=WlEAixXTAXHbCVwmo/P/KsBiLKLkRXE3DTTERJmvGjzNSvV169o1jw9L0U0sKSTI/MMHeo eMTy916bkhrjpQ332omzlELc61FS0OspHBIXR5vVSdL0kynaWYGPE43FSF5awn086Q4U0x B4uvyIgyzV8br7xQmE3nu37fOCfWy5U= 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-376-lWRK6raQPligR1tcSuyMoQ-1; Thu, 28 May 2020 13:23:57 -0400 X-MC-Unique: lWRK6raQPligR1tcSuyMoQ-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5D86E8015D2; Thu, 28 May 2020 17:23:54 +0000 (UTC) Received: from krava (unknown [10.40.195.83]) by smtp.corp.redhat.com (Postfix) with SMTP id 310947A8A5; Thu, 28 May 2020 17:23:49 +0000 (UTC) Date: Thu, 28 May 2020 19:23:49 +0200 From: Jiri Olsa To: Andrii Nakryiko Cc: Alexei Starovoitov , Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Networking , bpf , Yonghong Song , Martin KaFai Lau , David Miller , John Fastabend , Jesper Dangaard Brouer , Wenbo Zhang , KP Singh , Andrii Nakryiko , Brendan Gregg , Florent Revest , Al Viro Subject: Re: [PATCH 7/9] bpf: Compile the BTF id whitelist data in vmlinux Message-ID: <20200528172349.GA506785@krava> References: <20200506132946.2164578-1-jolsa@kernel.org> <20200506132946.2164578-8-jolsa@kernel.org> <20200513182940.gil7v5vkthhwck3t@ast-mbp.dhcp.thefacebook.com> <20200514080515.GH3343750@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, May 14, 2020 at 03:46:26PM -0700, Andrii Nakryiko wrote: SNIP > > I was thinking of putting the names in __init section and generate the BTF > > ids on kernel start, but the build time generation seemed more convenient.. > > let's see the linking times with 'real size' whitelist and we can reconsider > > > > Being able to record such places where to put BTF ID in code would be > really nice, as Alexei mentioned. There are many potential use cases > where it would be good to have BTF IDs just put into arbitrary > variables/arrays. This would trigger compilation error, if someone > screws up the name, or function is renamed, or if function can be > compiled out under some configuration. E.g., assuming some reasonable > implementation of the macro hi, I'm struggling with this part.. to get some reasonable reference to function/name into 32 bits? any idea? ;-) jirka > > static const u32 d_path_whitelist[] = { > BTF_ID_FUNC(vfs_fallocate), > #ifdef CONFIG_WHATEVER > BTF_ID_FUNC(do_truncate), > #endif > }; > > Would be nice and very explicit. Given this is not going to be sorted, > you won't be able to use binary search, but if whitelists are > generally small, it should be fine as is. If not, hashmap could be > built in runtime and would be, probably, faster than binary search for > longer sets of BTF IDs. > > I wonder if we can do some assembly magic with generating extra > symbols and/or relocations to achieve this? What do you think? Is it > doable/desirable/better? > > > > thanks, > > jirka > > >