From patchwork Thu Feb 2 16:30:55 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13126547 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 9179EC636D7 for ; Thu, 2 Feb 2023 16:31:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231743AbjBBQbL (ORCPT ); Thu, 2 Feb 2023 11:31:11 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231731AbjBBQbK (ORCPT ); Thu, 2 Feb 2023 11:31:10 -0500 Received: from mail-vk1-f178.google.com (mail-vk1-f178.google.com [209.85.221.178]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AEC1164698; Thu, 2 Feb 2023 08:31:07 -0800 (PST) Received: by mail-vk1-f178.google.com with SMTP id l129so1153178vkh.6; Thu, 02 Feb 2023 08:31:07 -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=anXQZojTFkdmfLnwafQXN0T5XgJCU3AiiRxtzHW7UPA=; b=p3N/foHYUlUmsH8ODPaCKJizAFJH320foFwlGY+eGU1UwoNRugrqUW5tbuer6xu9/Q R4K8O8G2xT+yjBiamG9PPv9Npb5R8bRkR2reUTIH9tSF9rYSKDD+5XfXsNcKTrgu+R2g Tn54fIfcgqhdNnbgAXzXR6ihwk4MIGBludXGnNow57ZKvah/LZH+O1xprT2ks4xw5RVm 454LDE0XSQLS8eSDxR8UYb9XBaMNi8w5vTQGDOX75iE+tK5oYtwS0BSMYoYUaB9CoGbM 2QOfePuJy3MJ44aEHQbXlnFNFKq0wZcFhsC+T3YS0eKBXNpQy0Zh4vtj2nZBL2yq5Rz4 sMzg== X-Gm-Message-State: AO0yUKXBG5M6tvEctpdDgvJUX/E6nTQ1SrFUTtpj12+3ZZ4x5nkuOG+d UnBWUPg7NTnHRgnguQwlg0p5n/OEGRAmYv30 X-Google-Smtp-Source: AK7set+VUsZMdfoZD6C4KYyS4uTpJw+OUDCHLDkRqwi21bPaaaCGxAudNJx1xHTQdMEYtBhqIGLDSA== X-Received: by 2002:a05:6122:731:b0:3e5:cfa3:124e with SMTP id 49-20020a056122073100b003e5cfa3124emr3646782vki.12.1675355466323; Thu, 02 Feb 2023 08:31:06 -0800 (PST) Received: from localhost ([24.1.27.177]) by smtp.gmail.com with ESMTPSA id c30-20020a05620a201e00b006e07228ed53sm36466qka.18.2023.02.02.08.31.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Feb 2023 08:31:05 -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, toke@redhat.com, brouer@redhat.com, corbet@lwn.net, linux-doc@vger.kernel.org Subject: [PATCH bpf-next 2/3] bpf: Add KF_DEPRECATED kfunc flag Date: Thu, 2 Feb 2023 10:30:55 -0600 Message-Id: <20230202163056.658641-3-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230202163056.658641-1-void@manifault.com> References: <20230202163056.658641-1-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 we have our kfunc lifecycle expectations clearly documented, and that KF_DEPRECATED is documented as an optional method for kfunc developers and maintainers to provide a deprecation story to BPF users, we need to actually implement the flag. This patch adds KF_DEPRECATED, and updates the verifier to issue a verifier log message if a deprecated kfunc is called. Currently, a BPF program either has to fail to verify, or be loaded with log level 2 in order to see the message. We could eventually enhance this to always be logged regardless of log level or verification status, or we could instead emit a warning to dmesg. This seems like the least controversial option for now. A subsequent patch will add a selftest that verifies this behavior. Signed-off-by: David Vernet --- include/linux/btf.h | 1 + kernel/bpf/verifier.c | 8 ++++++++ 2 files changed, 9 insertions(+) diff --git a/include/linux/btf.h b/include/linux/btf.h index 49e0fe6d8274..a0ea788ee9b0 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -71,6 +71,7 @@ #define KF_SLEEPABLE (1 << 5) /* kfunc may sleep */ #define KF_DESTRUCTIVE (1 << 6) /* kfunc performs destructive actions */ #define KF_RCU (1 << 7) /* kfunc only takes rcu pointer arguments */ +#define KF_DEPRECATED (1 << 8) /* kfunc is slated to be removed or deprecated */ /* * Tag marking a kernel function as a kfunc. This is meant to minimize the diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 4cc0e70ee71e..22adcf24f9e1 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -8511,6 +8511,11 @@ static bool is_kfunc_rcu(struct bpf_kfunc_call_arg_meta *meta) return meta->kfunc_flags & KF_RCU; } +static bool is_kfunc_deprecated(const struct bpf_kfunc_call_arg_meta *meta) +{ + return meta->kfunc_flags & KF_DEPRECATED; +} + static bool is_kfunc_arg_kptr_get(struct bpf_kfunc_call_arg_meta *meta, int arg) { return arg == 0 && (meta->kfunc_flags & KF_KPTR_GET); @@ -9646,6 +9651,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn, mark_btf_func_reg_size(env, regno, t->size); } + if (is_kfunc_deprecated(&meta)) + verbose(env, "calling deprecated kfunc %s\n", func_name); + return 0; }