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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2B59C433F5 for ; Sat, 29 Jan 2022 01:11:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344784AbiA2BLs (ORCPT ); Fri, 28 Jan 2022 20:11:48 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229812AbiA2BLr (ORCPT ); Fri, 28 Jan 2022 20:11:47 -0500 Received: from mail-pl1-x62f.google.com (mail-pl1-x62f.google.com [IPv6:2607:f8b0:4864:20::62f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7D22BC061714; Fri, 28 Jan 2022 17:11:46 -0800 (PST) Received: by mail-pl1-x62f.google.com with SMTP id x11so7711918plg.6; Fri, 28 Jan 2022 17:11:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=sKsBVhQwSlJcRatjipRMtQLnHaf6lN3tRXCvoF5/r20=; b=puOMkZ0UFGv9hyGOgycf4HKKTdfZqIGO1mTa/jfGvU4s52IdOFDx07S+Y+hkfcroi5 wa8t9B+tb1Mdxsl9DSHh57cjQLi8qZ8iY0IXkAEhw914wvy/cPM9+Zhz1vqB1YtfhWbV D1dDGEMpDPTc8AwnDiBMYXs3i429EAI1d0x6GhgylerxkcMn+3EP+/2MEsldY8RjW6Im xEJkGOEtdmHkH80zc2weJ9eMATeLBwGpkKhpI+0ffNn/BT4P9uXRAcO4owmMcon1Nbrf 9MqewY7KWoLlWuE0MHuvIJIQm/62c+wrFiVoKa9rj2npQ3z/OBJJW/iN/zAX6puCSxeR 4rtA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=sKsBVhQwSlJcRatjipRMtQLnHaf6lN3tRXCvoF5/r20=; b=gzZT1ydAZ97oWjMqhlGta1MY3Yrpd+yKWn8vBUXGxHinC4WVQ50c010+ZFd3a3WWdN qaU2WEJ0niE7AT+Fcf6c7V09fBxSXkUD/8OcDJ5CV/o148XJOr64imXIjg8LtMGCa4yR +NIXIoJ8pG4/XytNRoHTFgjrQRvSSeRltS7U8qn19MFfAcxX+zm1OioF5BmbR5A/wJCH DRGioeLCqAZ7KrI64sj3qkynCMTG8qyn5QwQemK1jepgHdMxpRRJY5645jn2AQAviMoe U7baBw3Cw4tpP1I5wDCapkrteWZJ56EyTNSUvLumLPQfylU5taFWVOwb0ZzFb2+kcvk1 FzOQ== X-Gm-Message-State: AOAM532tF9Gu5724+ttvxYCCDueXqPkgkpug8FROPmL8Tt9u+Rgxchf2 LKNzGUSK6yzoRXkKfVnP4WwWr6YfrWIGrk6/KLg= X-Google-Smtp-Source: ABdhPJwpZJefhaXw6b9jI+aK36Vigr5rNrt3zdJ8hyeB/f3ZBlfA/8bmw/aLvPYYd7zdgrbxJhmkE5wrT7fcFfxdJF8= X-Received: by 2002:a17:902:e54c:: with SMTP id n12mr10841591plf.78.1643418705879; Fri, 28 Jan 2022 17:11:45 -0800 (PST) MIME-Version: 1.0 References: <20211210172034.13614-1-mcroce@linux.microsoft.com> <177da568-8410-36d6-5f95-c5792ba47d62@fb.com> In-Reply-To: From: Alexei Starovoitov Date: Fri, 28 Jan 2022 17:11:34 -0800 Message-ID: Subject: Re: [PATCH bpf-next] bpf: limit bpf_core_types_are_compat() recursion To: Matteo Croce Cc: Yonghong Song , bpf , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Jan 28, 2022 at 4:36 PM Matteo Croce wrote: > > On Fri, Jan 28, 2022 at 9:09 PM Alexei Starovoitov > wrote: > > > > On Fri, Jan 28, 2022 at 10:51 AM Matteo Croce > > wrote: > > > > > > On Fri, Jan 28, 2022 at 6:31 AM Alexei Starovoitov > > > wrote: > > > > > > > > On Mon, Dec 20, 2021 at 10:34 PM Yonghong Song wrote: > > > > > > > > > > > > > > > https://reviews.llvm.org/D116063 improved the error message as below > > > > > to make it a little bit more evident what is the problem: > > > > > > > > > > $ clang -target bpf -O2 -g -c bug.c > > > > > > > > > > fatal error: error in backend: SubroutineType not supported for > > > > > BTF_TYPE_ID_REMOTE reloc > > > > > > > > Hi Matteo, > > > > > > > > Are you still working on a test? > > > > What's a timeline to repost the patch set? > > > > > > > > Thanks! > > > > > > Hi Alexei, > > > > > > The change itself is ready, I'm just stuck at writing a test which > > > will effectively calls __bpf_core_types_are_compat() with some > > > recursion. > > > I guess that I have to generate a BTF_KIND_FUNC_PROTO type somehow, so > > > __bpf_core_types_are_compat() is called again to check the prototipe > > > arguments type. > > > I tried with these two, with no luck: > > > > > > // 1 > > > typedef int (*func_proto_typedef)(struct sk_buff *); > > > bpf_core_type_exists(func_proto_typedef); > > > > > > // 2 > > > void func_proto(int, unsigned int); > > > bpf_core_type_id_kernel(func_proto); > > > > > > Which is a simple way to generate a BTF_KIND_FUNC_PROTO BTF field? > > > > What do you mean 'no luck'? > > Have you tried what progs/test_core_reloc_type_id.c is doing? > > typedef int (*func_proto_typedef)(long); > > bpf_core_type_id_kernel(func_proto_typedef); > > > > Without macros: > > typedef int (*func_proto_typedef)(long); > > > > int test() { > > return __builtin_btf_type_id(*(typeof(func_proto_typedef) *)0, 1); > > } > > int test2() { > > return __builtin_preserve_type_info(*(typeof(func_proto_typedef) *)0, 0); > > } > > > > > > compiles fine and generates relos. > > Yes, I tried that one. > We reach bpf_core_apply_relo_insn() but not bpf_core_spec_match(), > since cands->len is 0. > > [ 16.424821] bpf_core_apply_relo_insn:1202 cands->len: 0 > > That's a very simple raw_tracepoint/sys_enter program: Did you forget to attach it ? If it's doing bpf_core_type_id_kernel(func_proto_typedef) then, of course, cands->len will be zero. You need to add this typedef to bpf_testmod first. Then use two typedef flavors: func_proto_typedef___match and func_proto_typedef___doesnt_match with matching and mismatching prototypes, so both can call into bpf_core_types_are_compat() and return different results. Then build on top to test recursion.