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 C9D04C3F2D8 for ; Tue, 3 Mar 2020 20:05:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9501A2073B for ; Tue, 3 Mar 2020 20:05:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="eZtmMwLL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728002AbgCCUFZ (ORCPT ); Tue, 3 Mar 2020 15:05:25 -0500 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:46914 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731457AbgCCUFZ (ORCPT ); Tue, 3 Mar 2020 15:05:25 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1583265924; 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=oqvnJpDgLYD/tNq6zGIo7bmstN4/76XEt5bzM7y0dlA=; b=eZtmMwLLSnRbyUI0bWfzfE3z0Tmxj+yG5UBDwzZyPZg8MSnLzzpnmkLhNJQNERH31QyYrE uj9YjqBoyICpFPd/1+3i5wVMXpTWroNvq/sLwIvCc6v2MRbLHrcaTR39gxQZV9tLNKD7z1 VYpnQX5BdHb4YNzxlPSHZEbrhKV+7wI= 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-81-CtyHItd5Obm2rWsnsQNnWg-1; Tue, 03 Mar 2020 15:05:20 -0500 X-MC-Unique: CtyHItd5Obm2rWsnsQNnWg-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7571F107ACC4; Tue, 3 Mar 2020 20:05:18 +0000 (UTC) Received: from krava (ovpn-206-59.brq.redhat.com [10.40.206.59]) by smtp.corp.redhat.com (Postfix) with ESMTPS id B8E581001B3F; Tue, 3 Mar 2020 20:05:15 +0000 (UTC) Date: Tue, 3 Mar 2020 21:05:13 +0100 From: Jiri Olsa To: Andrii Nakryiko Cc: Jiri Olsa , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Networking , bpf , Yonghong Song , Martin KaFai Lau , Jakub Kicinski , David Miller , John Fastabend , Jesper Dangaard Brouer Subject: Re: [RFC] libbpf,selftests: Question on btf_dump__emit_type_decl for BTF_KIND_FUNC Message-ID: <20200303200513.GB74093@krava> References: <20200303140837.90056-1-jolsa@kernel.org> <20200303173314.GA74093@krava> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Mar 03, 2020 at 10:00:02AM -0800, Andrii Nakryiko wrote: > On Tue, Mar 3, 2020 at 9:33 AM Jiri Olsa wrote: > > > > On Tue, Mar 03, 2020 at 09:09:38AM -0800, Andrii Nakryiko wrote: > > > On Tue, Mar 3, 2020 at 6:12 AM Jiri Olsa wrote: > > > > > > > > hi, > > > > for bpftrace I'd like to print BTF functions (BTF_KIND_FUNC) > > > > declarations together with their names. > > > > > > > > I saw we have btf_dump__emit_type_decl and added BTF_KIND_FUNC, > > > > where it seemed to be missing, so it prints out something now > > > > (not sure it's the right fix though). > > > > > > > > Anyway, would you be ok with adding some flag/bool to struct > > > > btf_dump_emit_type_decl_opts, so I could get output like: > > > > > > > > kfunc:ksys_readahead(int fd, long long int offset, long unsigned int count) = ssize_t > > > > kfunc:ksys_read(unsigned int fd, char buf, long unsigned int count) = size_t > > > > > > > > ... to be able to the arguments and return type separated, > > > > so I could easily get to something like above? > > > > > > > > Current interface is just vfprintf callback and I'm not sure > > > > I can rely that it will allywas be called with same arguments, > > > > like having separated calls for parsed atoms like 'return type', > > > > '(', ')', '(', 'arg type', 'arg name', ... > > > > > > > > I'm open to any suggestion ;-) > > > > > > Hey Jiri! > > > > > > Can you please elaborate on the use case and problem you are trying to solve? > > > > > > I think we can (and probably even should) add such option and support > > > to dump functions, but whatever we do it should be a valid C syntax > > > and should be compilable. > > > Example above: > > > > > > kfunc:ksys_read(unsigned int fd, char buf, long unsigned int count) = size_t > > > > > > Is this really the syntax you need to get? I think btf_dump, when > > > (optionally) emitting function declaration, will have to emit that > > > particular one as: > > > > > > size_t ksys_read(unsigned int fd, char buf, long unsigned int count); > > > > > > But I'd like to hear the use case before we add this. Thanks! > > > > the use case is just for the 'bpftrace -l' output, which displays > > the probe names that could be used.. for kernel BTF kernel functions > > it's 'kfunc:function(args)' > > > > software:task-clock: > > hardware:backend-stalls: > > hardware:branch-instructions: > > ... > > tracepoint:kvmmmu:kvm_mmu_pagetable_walk > > tracepoint:kvmmmu:kvm_mmu_paging_element > > ... > > kprobe:console_on_rootfs > > kprobe:trace_initcall_start_cb > > kprobe:run_init_process > > kprobe:try_to_run_init_process > > ... > > kfunc:x86_reserve_hardware > > kfunc:hw_perf_lbr_event_destroy > > kfunc:x86_perf_event_update > > > > I dont want to print the return type as is in C, because it would > > mess up the whole output, hence the '= ' > > > > kfunc:ksys_readahead(int fd, long long int offset, long unsigned int count) = ssize_t > > kfunc:ksys_read(unsigned int fd, char buf, long unsigned int count) = size_t > > > > also possible only in verbose mode ;-) > > > > the final shape of the format will be decided in a bpftrace review, > > but in any case I think I'll need some way to get these bits: > > > > > > Ok, I think for your use case it's better for you to implement it > customly, I don't think this fits btf_dump() C output as is. But you > have all the right high-level APIs anyways. There is nothing irregular > about function declarations, thankfully. Pointers to functions are way > more involved, syntactically, which is already abstracted from you in > btf_dump__emit_type_decl(). Here's the code: > > static int dump_funcs(const struct btf *btf, struct btf_dump *d) > { > int err = 0, i, j, cnt = btf__get_nr_types(btf); > const struct btf_type *t; > const struct btf_param *p; > const char *name; > > for (i = 1; i <= cnt; i++) { > t = btf__type_by_id(btf, i); > if (!btf_is_func(t)) > continue; > > name = btf__name_by_offset(btf, t->name_off); > t = btf__type_by_id(btf, t->type); > if (!btf_is_func_proto(t)) > return -EINVAL; > > printf("kfunc:%s(", name); > for (j = 0, p = btf_params(t); j < btf_vlen(t); j++, p++) { > err = btf_dump__emit_type_decl(d, p->type, NULL); > if (err) > return err; > } > printf(") = "); > > err = btf_dump__emit_type_decl(d, t->type, NULL); > if (err) > return err; aaah right, we could move it one level down ;-) ok, that will do > > printf(";\n"); > } > return 0; > } > > Beware, this will crash right now due to NULL field_name, but I'm > fixing that with a tiny patch in just a second. > > Also beware, there are no argument names captures for func_protos... > > So with the above (and btf_dump__emit_type_decl() fix for NULL > field_name), this will produce output: > > kfunc:num_digits(int) = int; > kfunc:copy_from_user_nmi(void *const void *long unsigned int) = long > unsigned int; > kfunc:arch_wb_cache_pmem(void *size_t) = void; > kfunc:__clear_user(void *long unsigned int) = long unsigned int; thanks, I'll use that jirka