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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 C085BC433E0 for ; Tue, 16 Mar 2021 21:58:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F1FE64F8A for ; Tue, 16 Mar 2021 21:58:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229890AbhCPV5j (ORCPT ); Tue, 16 Mar 2021 17:57:39 -0400 Received: from www62.your-server.de ([213.133.104.62]:42774 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229545AbhCPV5U (ORCPT ); Tue, 16 Mar 2021 17:57:20 -0400 Received: from sslproxy05.your-server.de ([78.46.172.2]) by www62.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92.3) (envelope-from ) id 1lMHgh-0001W9-La; Tue, 16 Mar 2021 22:57:15 +0100 Received: from [85.7.101.30] (helo=pc-9.home) by sslproxy05.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lMHgh-000Lt3-CZ; Tue, 16 Mar 2021 22:57:15 +0100 Subject: Re: [PATCH] libbpf: avoid inline hint definition from 'linux/stddef.h' To: Andrii Nakryiko Cc: Pedro Tammela , Alexei Starovoitov , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Nathan Chancellor , Nick Desaulniers , Networking , bpf , open list , clang-built-linux References: <20210314173839.457768-1-pctammela@gmail.com> <5083f82b-39fc-9d46-bcd0-3a6be2fc7f98@iogearbox.net> From: Daniel Borkmann Message-ID: <3b05d3c8-1f4a-194a-098f-0eb7ab43d455@iogearbox.net> Date: Tue, 16 Mar 2021 22:57:14 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.4/26110/Tue Mar 16 12:05:23 2021) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/16/21 10:34 PM, Andrii Nakryiko wrote: > On Tue, Mar 16, 2021 at 2:01 PM Daniel Borkmann wrote: >> On 3/14/21 6:38 PM, Pedro Tammela wrote: >>> Linux headers might pull 'linux/stddef.h' which defines >>> '__always_inline' as the following: >>> >>> #ifndef __always_inline >>> #define __always_inline __inline__ >>> #endif >>> >>> This becomes an issue if the program picks up the 'linux/stddef.h' >>> definition as the macro now just hints inline to clang. >> >> How did the program end up including linux/stddef.h ? Would be good to >> also have some more details on how we got here for the commit desc. > > It's an UAPI header, so why not? Is there anything special about > stddef.h that makes it unsuitable to be included? Hm, fair enough, looks like linux/types.h already pulls it in, so no. We defined our own stddef.h longer time ago, so looks like we never ran into this issue. >>> This change now enforces the proper definition for BPF programs >>> regardless of the include order. >>> >>> Signed-off-by: Pedro Tammela >>> --- >>> tools/lib/bpf/bpf_helpers.h | 7 +++++-- >>> 1 file changed, 5 insertions(+), 2 deletions(-) >>> >>> diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h >>> index ae6c975e0b87..5fa483c0b508 100644 >>> --- a/tools/lib/bpf/bpf_helpers.h >>> +++ b/tools/lib/bpf/bpf_helpers.h >>> @@ -29,9 +29,12 @@ >>> */ >>> #define SEC(NAME) __attribute__((section(NAME), used)) >>> >>> -#ifndef __always_inline >>> +/* >>> + * Avoid 'linux/stddef.h' definition of '__always_inline'. >>> + */ >> >> I think the comment should have more details on 'why' we undef it as in >> few months looking at it again, the next question to dig into would be >> what was wrong with linux/stddef.h. Providing a better rationale would >> be nice for readers here. > > So for whatever reason commit bot didn't send notification, but I've > already landed this yesterday. To me, with #undef + #define it's > pretty clear that we "force-define" __always_inline exactly how we > want it, but we can certainly add clarifying comment in the follow up, > if you think it's needed. Up to you, but given you applied it it's probably not worth the trouble; missed it earlier given I didn't see the patchbot message in the thread initially. :/ >>> +#undef __always_inline >>> #define __always_inline inline __attribute__((always_inline)) >>> -#endif >>> + >>> #ifndef __noinline >>> #define __noinline __attribute__((noinline)) >>> #endif >>> >>