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=-6.0 required=3.0 tests=BAYES_00,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 942C7C48BCD for ; Wed, 9 Jun 2021 13:33:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AF4C613B8 for ; Wed, 9 Jun 2021 13:33:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236382AbhFINfk (ORCPT ); Wed, 9 Jun 2021 09:35:40 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:40742 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236379AbhFINfi (ORCPT ); Wed, 9 Jun 2021 09:35:38 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623245623; 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=ym1naShMb/FjUs80jLgteJ3jD85pxMGWwBsQDwktStk=; b=XcG/2lV21nmQQP5mnCH0jk/uX0tX2I+JunG3wqTlbqIkMt74Mb1+bwuoZb178B6lJyOYVV NhzauHAx72dCq80ARXDCIlA+sAj9ngXRIuVMsYPsYXnhMQiz+TAEpoCZm3htK/NQ3xbPY1 cv+FOuLbjHBAW9ZD7dvChbSTxukJu+I= 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-374-bsp-ZMP3P1m4y1oE8edkQQ-1; Wed, 09 Jun 2021 09:33:42 -0400 X-MC-Unique: bsp-ZMP3P1m4y1oE8edkQQ-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 0ED61100B3AF; Wed, 9 Jun 2021 13:33:40 +0000 (UTC) Received: from krava (unknown [10.40.195.97]) by smtp.corp.redhat.com (Postfix) with SMTP id 85F2060BD8; Wed, 9 Jun 2021 13:33:36 +0000 (UTC) Date: Wed, 9 Jun 2021 15:33:35 +0200 From: Jiri Olsa To: Alexei Starovoitov Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , "Steven Rostedt (VMware)" , Network Development , bpf , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Daniel Xu , Viktor Malik Subject: Re: [PATCH 13/19] bpf: Add support to link multi func tracing program Message-ID: References: <20210605111034.1810858-1-jolsa@kernel.org> <20210605111034.1810858-14-jolsa@kernel.org> <20210608184903.rgnv65jimekqugol@ast-mbp.dhcp.thefacebook.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 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Jun 08, 2021 at 04:05:29PM -0700, Alexei Starovoitov wrote: > On Tue, Jun 8, 2021 at 2:07 PM Jiri Olsa wrote: > > > > On Tue, Jun 08, 2021 at 11:49:03AM -0700, Alexei Starovoitov wrote: > > > On Tue, Jun 08, 2021 at 08:17:00PM +0200, Jiri Olsa wrote: > > > > On Tue, Jun 08, 2021 at 08:42:32AM -0700, Alexei Starovoitov wrote: > > > > > On Sat, Jun 5, 2021 at 4:11 AM Jiri Olsa wrote: > > > > > > > > > > > > Adding support to attach multiple functions to tracing program > > > > > > by using the link_create/link_update interface. > > > > > > > > > > > > Adding multi_btf_ids/multi_btf_ids_cnt pair to link_create struct > > > > > > API, that define array of functions btf ids that will be attached > > > > > > to prog_fd. > > > > > > > > > > > > The prog_fd needs to be multi prog tracing program (BPF_F_MULTI_FUNC). > > > > > > > > > > > > The new link_create interface creates new BPF_LINK_TYPE_TRACING_MULTI > > > > > > link type, which creates separate bpf_trampoline and registers it > > > > > > as direct function for all specified btf ids. > > > > > > > > > > > > The new bpf_trampoline is out of scope (bpf_trampoline_lookup) of > > > > > > standard trampolines, so all registered functions need to be free > > > > > > of direct functions, otherwise the link fails. > > > > > > > > > > Overall the api makes sense to me. > > > > > The restriction of multi vs non-multi is too severe though. > > > > > The multi trampoline can serve normal fentry/fexit too. > > > > > > > > so multi trampoline gets called from all the registered functions, > > > > so there would need to be filter for specific ip before calling the > > > > standard program.. single cmp/jnz might not be that bad, I'll check > > > > > > You mean reusing the same multi trampoline for all IPs and regenerating > > > it with a bunch of cmp/jnz checks? There should be a better way to scale. > > > Maybe clone multi trampoline instead? > > > IPs[1-10] will point to multi. > > > IP[11] will point to a clone of multi that serves multi prog and > > > fentry/fexit progs specific for that IP. > > > > ok, so we'd clone multi trampoline if there's request to attach > > standard trampoline to some IP from multi trampoline > > > > .. and transform currently attached standard trampoline for IP > > into clone of multi trampoline, if there's request to create > > multi trampoline that covers that IP > > yep. For every IP==btf_id there will be only two possible trampolines. > Should be easy enough to track and transition between them. > The standard fentry/fexit will only get negligible slowdown from > going through multi. > multi+fexit and fmod_ret needs to be thought through as well. > That's why I thought that 'ip' at the end should simplify things. > Only multi will have access to it. > But we can store it first too. fentry/fexit will see ctx=r1 with +8 offset > and will have normal args in ctx. Like ip isn't even there. > While multi trampoline is always doing ip, arg1,arg2, .., arg6 > and passes ctx = &ip into multi prog and ctx = &arg1 into fentry/fexit. > 'ret' for fexit is problematic though. hmm. > Maybe such clone multi trampoline for specific ip with 2 args will do: > ip, arg1, arg2, ret, 0, 0, 0, ret. we could call multi progs first and setup new args and call non-multi progs with that jirka > Then multi will have 6 args, though 3rd is actually ret. > Then fexit will have ret in the right place and multi prog will have > it as 7th arg. >