From patchwork Wed Feb 1 17:30:14 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13124796 X-Patchwork-Delegate: bpf@iogearbox.net 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 814DEC05027 for ; Wed, 1 Feb 2023 17:31:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231803AbjBARbY (ORCPT ); Wed, 1 Feb 2023 12:31:24 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54074 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231893AbjBARax (ORCPT ); Wed, 1 Feb 2023 12:30:53 -0500 Received: from mail-qt1-f178.google.com (mail-qt1-f178.google.com [209.85.160.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 91A227D6CE; Wed, 1 Feb 2023 09:30:25 -0800 (PST) Received: by mail-qt1-f178.google.com with SMTP id f10so4102851qtv.1; Wed, 01 Feb 2023 09:30:25 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=13KNfT/+JOQqYlkhtzi2SYuhI4+Je2/xoJvmyEaI8R4=; b=1WOFnItPm8cfLydzOcTpVyi9IUz47dRXzGcITOyiJapfdt1eu7KyqNWnbwezL3x45M UJqfTTSYa1AboaLGiBd2ETMZLmkl+/XGbkhhzlmx2YBb4hIungH6sO1fFkzoTpuot6lF 8vpnU6qg6wJLluMmfatmpQKqRqb6WnpWT4tXa5kFr37kmz4OodWziDu0kVdZtWXY9mLA Gwd0t7N96Gp4Jcc75ZeEWThzXLMWFizk4oHYXyHR1+VLhhhWX7DVbFAlI/PUsJF2PqXh X5wZ8xrJHgnJ3LnOCkBaqSV1SsunV4Yrsi17ffNbiAcj1OB3PlrfP7FPEq3UjRykORi3 gP7g== X-Gm-Message-State: AO0yUKVxmuYIRivshwXv5L5u7JskZY0YG0zSOm3CdC9AVYPYmO/mpcue skziUDT3aMd5lIii5ii0UL2ZLyBvWq1czN7n X-Google-Smtp-Source: AK7set8gDUM85Zrq24nQC9jG/YhLtejz6JWWARcOkU0uuhtoi0Zhn2aEqASBbHAKEz/Ct82F/dIsRg== X-Received: by 2002:a05:622a:34e:b0:3b9:bda7:bfa7 with SMTP id r14-20020a05622a034e00b003b9bda7bfa7mr3145620qtw.40.1675272624232; Wed, 01 Feb 2023 09:30:24 -0800 (PST) Received: from localhost ([2620:10d:c091:480::1:1971]) by smtp.gmail.com with ESMTPSA id x14-20020a05620a258e00b0071b368cf074sm9158367qko.118.2023.02.01.09.30.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Feb 2023 09:30:23 -0800 (PST) From: David Vernet To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, song@kernel.org, yhs@meta.com, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@google.com, haoluo@google.com, jolsa@kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, corbet@lwn.net, hch@infradead.org, acme@kernel.org, alan.maguire@oracle.com Subject: [PATCH bpf-next v3 2/4] bpf: Document usage of the new __bpf_kfunc macro Date: Wed, 1 Feb 2023 11:30:14 -0600 Message-Id: <20230201173016.342758-3-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230201173016.342758-1-void@manifault.com> References: <20230201173016.342758-1-void@manifault.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Now that the __bpf_kfunc macro has been added to linux/btf.h, include a blurb about it in the kfuncs.rst file. In order for the macro to successfully render with .. kernel-doc, we'll also need to add it to the c_id_attributes array. Acked-by: Stanislav Fomichev Signed-off-by: David Vernet --- Documentation/bpf/kfuncs.rst | 20 +++++++++++++++++--- Documentation/conf.py | 3 +++ 2 files changed, 20 insertions(+), 3 deletions(-) diff --git a/Documentation/bpf/kfuncs.rst b/Documentation/bpf/kfuncs.rst index 1a683225d080..0bd07b39c2a4 100644 --- a/Documentation/bpf/kfuncs.rst +++ b/Documentation/bpf/kfuncs.rst @@ -41,7 +41,7 @@ An example is given below:: __diag_ignore_all("-Wmissing-prototypes", "Global kfuncs as their definitions will be in BTF"); - struct task_struct *bpf_find_get_task_by_vpid(pid_t nr) + __bpf_kfunc struct task_struct *bpf_find_get_task_by_vpid(pid_t nr) { return find_get_task_by_vpid(nr); } @@ -66,7 +66,7 @@ kfunc with a __tag, where tag may be one of the supported annotations. This annotation is used to indicate a memory and size pair in the argument list. An example is given below:: - void bpf_memzero(void *mem, int mem__sz) + __bpf_kfunc void bpf_memzero(void *mem, int mem__sz) { ... } @@ -86,7 +86,7 @@ safety of the program. An example is given below:: - void *bpf_obj_new(u32 local_type_id__k, ...) + __bpf_kfunc void *bpf_obj_new(u32 local_type_id__k, ...) { ... } @@ -125,6 +125,20 @@ flags on a set of kfuncs as follows:: This set encodes the BTF ID of each kfunc listed above, and encodes the flags along with it. Ofcourse, it is also allowed to specify no flags. +kfunc definitions should also always be annotated with the ``__bpf_kfunc`` +macro. This prevents issues such as the compiler inlining the kfunc if it's a +static kernel function, or the function being elided in an LTO build as it's +not used in the rest of the kernel. Developers should not manually add +annotations to their kfunc to prevent these issues. If an annotation is +required to prevent such an issue with your kfunc, it is a bug and should be +added to the definition of the macro so that other kfuncs are similarly +protected. An example is given below:: + + __bpf_kfunc struct task_struct *bpf_get_task_pid(s32 pid) + { + ... + } + 2.4.1 KF_ACQUIRE flag --------------------- diff --git a/Documentation/conf.py b/Documentation/conf.py index d927737e3c10..8b4e5451a02d 100644 --- a/Documentation/conf.py +++ b/Documentation/conf.py @@ -116,6 +116,9 @@ if major >= 3: # include/linux/linkage.h: "asmlinkage", + + # include/linux/btf.h + "__bpf_kfunc", ] else: