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=-11.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS 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 9EA40C433ED for ; Wed, 28 Apr 2021 22:05:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 669C9613F1 for ; Wed, 28 Apr 2021 22:05:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229890AbhD1WGB (ORCPT ); Wed, 28 Apr 2021 18:06:01 -0400 Received: from mail.kernel.org ([198.145.29.99]:39260 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229488AbhD1WGA (ORCPT ); Wed, 28 Apr 2021 18:06:00 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 191F961352; Wed, 28 Apr 2021 22:05:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1619647515; bh=FGs86d/LbRhfYZZhsLqUx+A4yXtI4DHMtl9ILbHTC3E=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=UEzHubqR+m7QG1aXffYAgFrz0w5mve6G+A5ppTPBxuiB5o4awjNLU+9iXyxUhtcgK CGQcQZIv9h0rJXnGSvgcPFmSHs+FqW/9eZQ9+2F1vuRCBH+q1JmCIXV2QugbiXPU5F 0/5qguK5ESy1LyRh2E0GWbhgKep6BhGDfMkntJL2Q4qFLnsiA8tIdVDiXNCf7PWpqX /+/5/B/BUVOOSmKPlUufujKiAq2IJfHx97VsKq2pFyaeE2A1qBYhvl3jGANdlY0gTL fTaBRlr0FArzvM5JRrgQ2Tv3n2IjbAgXZ0Qh/3QV88tEeOUAj/TrkCXo4si87guxbg m/6AhDImFNZpA== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 3A0394034C; Wed, 28 Apr 2021 19:05:12 -0300 (-03) Date: Wed, 28 Apr 2021 19:05:12 -0300 From: Arnaldo Carvalho de Melo To: Andrii Nakryiko Cc: Arnaldo Carvalho de Melo , Jiri Olsa , Martin KaFai Lau , Jiri Olsa , dwarves@vger.kernel.org, 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-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: dwarves@vger.kernel.org Em Wed, Apr 28, 2021 at 12:45:10PM -0700, Andrii Nakryiko escreveu: > On Wed, Apr 28, 2021 at 6:10 AM Arnaldo Carvalho de Melo wrote: > > Em Tue, Apr 27, 2021 at 01:38:51PM -0700, Andrii Nakryiko escreveu: > > > On Tue, Apr 27, 2021 at 5:34 AM Arnaldo Carvalho de Melo wrote: > > > > And tools that expect to trace a function can get that information from > > > > the BTF info instead of getting some failure when trying to trace those > > > > functions, right? > > > I don't think it belongs in BTF, though. > > My thinking was that since BTF is used when tracing, one would be > > interested in knowing if some functions can't be used for that. > > > Plus there are additional limitations enforced by BPF verifier that > > > will prevent some functions to be attached. So just because the > > > function is in BTF doesn't mean it's 100% attachable. > > Well, at least we would avoid some that can't for sure be used for > > tracing. But, a bit in there is precious, so probably geting a NACK from > > the kernel should be a good enough capability query. :-) > > Tools should just silently prune things in wildcards provided by the > > user that aren't traceable, silently, and provide an error message when > > the user explicitely asks for tracing a verbotten function. > Yep, that's what I'm doing in my retsnoop tool (I both filter by > available kprobes [0], and have extra blacklist [1]). Loading kprobes > is pretty simple and fast enough, shouldn't be a problem. > [0] https://github.com/anakryiko/retsnoop/blob/master/src/mass_attacher.c#L495 > [1] https://github.com/anakryiko/retsnoop/blob/master/src/mass_attacher.c#L41 Oh my, one more tool to download, build, try, have updated, etc. Will look at it, thanks for the pointer. - Arnaldo