From patchwork Thu Mar 16 05:40:24 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13177003 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 3A879C7618A for ; Thu, 16 Mar 2023 05:40:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229787AbjCPFkk (ORCPT ); Thu, 16 Mar 2023 01:40:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229785AbjCPFki (ORCPT ); Thu, 16 Mar 2023 01:40:38 -0400 Received: from mail-qv1-f44.google.com (mail-qv1-f44.google.com [209.85.219.44]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E9F335A1B1; Wed, 15 Mar 2023 22:40:37 -0700 (PDT) Received: by mail-qv1-f44.google.com with SMTP id x8so555597qvr.9; Wed, 15 Mar 2023 22:40:37 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678945237; 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=LqdX1QaRwIooZT8c9LoVfwKnRXDO5nO+/Pj89wdMEuk=; b=uhG3Z31MYUExDONsAkQsL4axFQe4FDkcwSnde04edN1C7CH8k9GE2xK67BRLBMTY17 W8afpqQBw7FbOh1b4e9QamcBYhbgG4Xit2cNX2hPWqnr8xwhgcWS4VXhKTDT30EN7AEa AJXEJZV+PlsY/5fpSeaeKmlxA9IeJCXEa3boQx/xNlUbyxAiOP3CCpCZILL58QZT7gh3 2SwTFtYi9gr5+FVVTPc2lkCJ2TNFCb53GKB2MJiu+neWHdvxI/BHSDUIcbrjiZa4p5SZ 149Y+StTEcZICRr/iWMSFeMsY8Hslo9ZH2QwZyJSalBi3ZStgjkXlVW4jnRxdRAOzdne jotA== X-Gm-Message-State: AO0yUKXlGLapgcBSSUJtJKXndqmvNnrODN2Zhp31ujtpQOKtYAZ7JLtm imKCSfSqf6/b7th/sAUXTiYx2rO0BS4tUY0r X-Google-Smtp-Source: AK7set/efTvVWm71l12hfzdyvLilNhTEqIyWrk1Pjc/PsSHMFmUcnWAjCkMK4OwM5AMYH7AIgnmvIw== X-Received: by 2002:a05:6214:1c81:b0:577:4ea5:243f with SMTP id ib1-20020a0562141c8100b005774ea5243fmr29565976qvb.7.1678945236627; Wed, 15 Mar 2023 22:40:36 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:7f57]) by smtp.gmail.com with ESMTPSA id r8-20020ae9d608000000b0073b7f2a0bcbsm5199468qkk.36.2023.03.15.22.40.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Mar 2023 22:40:36 -0700 (PDT) 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@fb.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 Subject: [PATCH bpf-next v2 1/5] bpf: Free struct bpf_cpumask in call_rcu handler Date: Thu, 16 Mar 2023 00:40:24 -0500 Message-Id: <20230316054028.88924-2-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230316054028.88924-1-void@manifault.com> References: <20230316054028.88924-1-void@manifault.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net The struct bpf_cpumask type uses the bpf_mem_cache_{alloc,free}() APIs to allocate and free its cpumasks. The bpf_mem allocator may currently immediately reuse some memory when its freed, without waiting for an RCU read cycle to elapse. We want to be able to treat struct bpf_cpumask objects as completely RCU safe. This is necessary for two reasons: 1. bpf_cpumask_kptr_get() currently does an RCU-protected refcnt_inc_not_zero(). This of course assumes that the underlying memory is not reused, and is therefore unsafe in its current form. 2. We want to be able to get rid of bpf_cpumask_kptr_get() entirely, and intead use the superior kptr RCU semantics now afforded by the verifier. This patch fixes (1), and enables (2), by making struct bpf_cpumask RCU safe. A subsequent patch will update the verifier to allow struct bpf_cpumask * pointers to be passed to KF_RCU kfuncs, and then a latter patch will remove bpf_cpumask_kptr_get(). Fixes: 516f4d3397c9 ("bpf: Enable cpumasks to be queried and used as kptrs") Signed-off-by: David Vernet --- kernel/bpf/cpumask.c | 19 ++++++++++++++----- 1 file changed, 14 insertions(+), 5 deletions(-) diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c index b6587ec40f1b..98eea62b6b7b 100644 --- a/kernel/bpf/cpumask.c +++ b/kernel/bpf/cpumask.c @@ -9,6 +9,7 @@ /** * struct bpf_cpumask - refcounted BPF cpumask wrapper structure * @cpumask: The actual cpumask embedded in the struct. + * @rcu: The RCU head used to free the cpumask with RCU safety. * @usage: Object reference counter. When the refcount goes to 0, the * memory is released back to the BPF allocator, which provides * RCU safety. @@ -24,6 +25,7 @@ */ struct bpf_cpumask { cpumask_t cpumask; + struct rcu_head rcu; refcount_t usage; }; @@ -108,6 +110,16 @@ __bpf_kfunc struct bpf_cpumask *bpf_cpumask_kptr_get(struct bpf_cpumask **cpumas return cpumask; } +static void cpumask_free_cb(struct rcu_head *head) +{ + struct bpf_cpumask *cpumask; + + cpumask = container_of(head, struct bpf_cpumask, rcu); + migrate_disable(); + bpf_mem_cache_free(&bpf_cpumask_ma, cpumask); + migrate_enable(); +} + /** * bpf_cpumask_release() - Release a previously acquired BPF cpumask. * @cpumask: The cpumask being released. @@ -121,11 +133,8 @@ __bpf_kfunc void bpf_cpumask_release(struct bpf_cpumask *cpumask) if (!cpumask) return; - if (refcount_dec_and_test(&cpumask->usage)) { - migrate_disable(); - bpf_mem_cache_free(&bpf_cpumask_ma, cpumask); - migrate_enable(); - } + if (refcount_dec_and_test(&cpumask->usage)) + call_rcu(&cpumask->rcu, cpumask_free_cb); } /** From patchwork Thu Mar 16 05:40:25 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13177004 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 7A9ACC6FD19 for ; Thu, 16 Mar 2023 05:40:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229797AbjCPFkl (ORCPT ); Thu, 16 Mar 2023 01:40:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47102 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229487AbjCPFkk (ORCPT ); Thu, 16 Mar 2023 01:40:40 -0400 Received: from mail-qt1-f177.google.com (mail-qt1-f177.google.com [209.85.160.177]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 530965CC1A; Wed, 15 Mar 2023 22:40:39 -0700 (PDT) Received: by mail-qt1-f177.google.com with SMTP id c19so610265qtn.13; Wed, 15 Mar 2023 22:40:39 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678945238; 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=/+xUrg9q1AAptwCu8YnIT5AXN2cGpwLJEELj3y+obxs=; b=Ec5zskyA+CcxxKTcQLOE4iemb6Ht/F4YGEjYmARn3IJU9zMTopdvLtEQOFRc+dkxCM iVUw3qJimroFMgDMUJeswElwKP0HIcXQ3DXHKlGpD6IlpYAyv8VrMuDJKbHHQ+Hc9XFV Tcs69aCIaDSPQ7vuM6e2c0ewBJDZWp/f0CMk3ZvtPU85LeiVnPa4rD8ZCRGl8stTdkQa Pi6o3s0ZPOvOdoX396/WCIDa0QFnE9pneGmXcQH/ZpV/30i6O05VueCVDMNbga09pjuH jo5/n1c6d1/ZjsnhUqdE6gYmRT9tXBD3MRehJoStgyvz0oaSutOYafK4nl8XoTLAgUqt P8MA== X-Gm-Message-State: AO0yUKU5qcyhjm06mOYTHYHxVFpYXsiJRjS6wXmP9K+GC+8oO7lYdL/v i1Nqs7QlL0nd+ZV2zeiI0mV/dYLN9+U97wYd X-Google-Smtp-Source: AK7set96ow2rNLkxVUlOBvSS6JIA2gPxQ4/d5kIAjCx/ebg6wH9zyfZtvFK7EwugjOQzJWYW8JPdOw== X-Received: by 2002:a05:622a:1049:b0:3d4:f850:2e9 with SMTP id f9-20020a05622a104900b003d4f85002e9mr4349342qte.31.1678945237984; Wed, 15 Mar 2023 22:40:37 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:7f57]) by smtp.gmail.com with ESMTPSA id d63-20020a37b442000000b0073b575f3603sm5153630qkf.101.2023.03.15.22.40.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Mar 2023 22:40:37 -0700 (PDT) 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@fb.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 Subject: [PATCH bpf-next v2 2/5] bpf: Mark struct bpf_cpumask as rcu protected Date: Thu, 16 Mar 2023 00:40:25 -0500 Message-Id: <20230316054028.88924-3-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230316054028.88924-1-void@manifault.com> References: <20230316054028.88924-1-void@manifault.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net struct bpf_cpumask is a BPF-wrapper around the struct cpumask type which can be instantiated by a BPF program, and then queried as a cpumask in similar fashion to normal kernel code. The previous patch in this series makes the type fully RCU safe, so the type can be included in the rcu_protected_type BTF ID list. A subsequent patch will remove bpf_cpumask_kptr_get(), as it's no longer useful now that we can just treat the type as RCU safe by default and do our own if check. Signed-off-by: David Vernet --- kernel/bpf/verifier.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 60793f793ca6..15b5c5c729f9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4599,6 +4599,7 @@ static bool in_rcu_cs(struct bpf_verifier_env *env) BTF_SET_START(rcu_protected_types) BTF_ID(struct, prog_test_ref_kfunc) BTF_ID(struct, cgroup) +BTF_ID(struct, bpf_cpumask) BTF_SET_END(rcu_protected_types) static bool rcu_protected_object(const struct btf *btf, u32 btf_id) From patchwork Thu Mar 16 05:40:26 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13177005 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 15E92C6FD1F for ; Thu, 16 Mar 2023 05:40:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229830AbjCPFkq (ORCPT ); Thu, 16 Mar 2023 01:40:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229802AbjCPFkm (ORCPT ); Thu, 16 Mar 2023 01:40:42 -0400 Received: from mail-qt1-f175.google.com (mail-qt1-f175.google.com [209.85.160.175]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1CAA75F21D; Wed, 15 Mar 2023 22:40:40 -0700 (PDT) Received: by mail-qt1-f175.google.com with SMTP id t9so630315qtx.8; Wed, 15 Mar 2023 22:40:40 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678945239; 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=fa2fhlw1TqFXS4nJVOwTl5oF6HLkgTrJ78c4jwZcDqU=; b=J1aGYm4XpzzJNzoci0JgQFAA5Yb5hgQwylVi/6HvBAnpI72YsuZj3CumC2gNQm7cwu qDlCeZi4h7DgNg9vNEY+5Fm9A3bxJGAK3WcKjeWOmwzCACg/Kmj5VWzuddxLwZDKf8zZ 885sIOorIvcz8K1Bp7zoCtI+ziyP5C1zu0zrqQOJlML1mSDDXzhVbnAZrXf6WLNdinVa 5Ubu7oWm1v5n44Y2SXIeDlsunluOFEzeFBtSpTVuwLawJoIz5kgBPjIzgqY4gGkg+MPC xkn9zJlYfWeXMyT2gH3kpp9NLApSuvJWPLAFpVQLDBHbRlnbo4EI+Fd0VS53rvAWTI/B Mgog== X-Gm-Message-State: AO0yUKU1BwDviIYwGrE1RerHzSLnW24zIJl3Jk362HmGNNCGq9LitiG+ D/AmzUMZ/Kppe0mLu9/c4ODDr66Ivzqi1JGD X-Google-Smtp-Source: AK7set+rZ9Aply+gc6/6dEFQe9Yi92wuLTMOtrpEXExmliE4f0Rsh6NZRkibpaiPeVAVFtxP2d+kgw== X-Received: by 2002:a05:622a:174c:b0:3bf:db29:b793 with SMTP id l12-20020a05622a174c00b003bfdb29b793mr4696811qtk.20.1678945239228; Wed, 15 Mar 2023 22:40:39 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:7f57]) by smtp.gmail.com with ESMTPSA id d192-20020ae9efc9000000b00745df1fac2bsm3876535qkg.76.2023.03.15.22.40.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Mar 2023 22:40:38 -0700 (PDT) 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@fb.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 Subject: [PATCH bpf-next v2 3/5] bpf/selftests: Test using global cpumask kptr with RCU Date: Thu, 16 Mar 2023 00:40:26 -0500 Message-Id: <20230316054028.88924-4-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230316054028.88924-1-void@manifault.com> References: <20230316054028.88924-1-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 struct bpf_cpumask * is considered an RCU-safe type according to the verifier, we should add tests that validate its common usages. This patch adds those tests to the cpumask test suite. A subsequent changes will remove bpf_cpumask_kptr_get(), and will adjust the selftest and BPF documentation accordingly. Signed-off-by: David Vernet --- .../selftests/bpf/prog_tests/cpumask.c | 1 + .../selftests/bpf/progs/cpumask_common.h | 6 ++ .../selftests/bpf/progs/cpumask_failure.c | 62 +++++++++++++++++++ .../selftests/bpf/progs/cpumask_success.c | 33 ++++++++++ 4 files changed, 102 insertions(+) diff --git a/tools/testing/selftests/bpf/prog_tests/cpumask.c b/tools/testing/selftests/bpf/prog_tests/cpumask.c index 5fbe457c4ebe..6c0fe23498c7 100644 --- a/tools/testing/selftests/bpf/prog_tests/cpumask.c +++ b/tools/testing/selftests/bpf/prog_tests/cpumask.c @@ -17,6 +17,7 @@ static const char * const cpumask_success_testcases[] = { "test_insert_leave", "test_insert_remove_release", "test_insert_kptr_get_release", + "test_global_mask_rcu", }; static void verify_success(const char *prog_name) diff --git a/tools/testing/selftests/bpf/progs/cpumask_common.h b/tools/testing/selftests/bpf/progs/cpumask_common.h index 65e5496ca1b2..7623782fbd62 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_common.h +++ b/tools/testing/selftests/bpf/progs/cpumask_common.h @@ -9,6 +9,9 @@ int err; +#define private(name) SEC(".bss." #name) __hidden __attribute__((aligned(8))) +private(MASK) static struct bpf_cpumask __kptr * global_mask; + struct __cpumask_map_value { struct bpf_cpumask __kptr * cpumask; }; @@ -51,6 +54,9 @@ void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask *src) __ksym u32 bpf_cpumask_any(const struct cpumask *src) __ksym; u32 bpf_cpumask_any_and(const struct cpumask *src1, const struct cpumask *src2) __ksym; +void bpf_rcu_read_lock(void) __ksym; +void bpf_rcu_read_unlock(void) __ksym; + static inline const struct cpumask *cast(struct bpf_cpumask *cpumask) { return (const struct cpumask *)cpumask; diff --git a/tools/testing/selftests/bpf/progs/cpumask_failure.c b/tools/testing/selftests/bpf/progs/cpumask_failure.c index cfe83f0ef9e2..9f726d55f747 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_failure.c +++ b/tools/testing/selftests/bpf/progs/cpumask_failure.c @@ -127,3 +127,65 @@ int BPF_PROG(test_cpumask_null, struct task_struct *task, u64 clone_flags) return 0; } + +SEC("tp_btf/task_newtask") +__failure __msg("R2 must be a rcu pointer") +int BPF_PROG(test_global_mask_out_of_rcu, struct task_struct *task, u64 clone_flags) +{ + struct bpf_cpumask *local, *prev; + + local = create_cpumask(); + if (!local) + return 0; + + prev = bpf_kptr_xchg(&global_mask, local); + if (prev) { + bpf_cpumask_release(prev); + err = 3; + return 0; + } + + bpf_rcu_read_lock(); + local = global_mask; + if (!local) { + err = 4; + bpf_rcu_read_unlock(); + return 0; + } + + bpf_rcu_read_unlock(); + + /* RCU region is exited before calling KF_RCU kfunc. */ + + bpf_cpumask_test_cpu(0, (const struct cpumask *)local); + + return 0; +} + +SEC("tp_btf/task_newtask") +__failure __msg("NULL pointer passed to trusted arg1") +int BPF_PROG(test_global_mask_no_null_check, struct task_struct *task, u64 clone_flags) +{ + struct bpf_cpumask *local, *prev; + + local = create_cpumask(); + if (!local) + return 0; + + prev = bpf_kptr_xchg(&global_mask, local); + if (prev) { + bpf_cpumask_release(prev); + err = 3; + return 0; + } + + bpf_rcu_read_lock(); + local = global_mask; + + /* No NULL check is performed on global cpumask kptr. */ + bpf_cpumask_test_cpu(0, (const struct cpumask *)local); + + bpf_rcu_read_unlock(); + + return 0; +} diff --git a/tools/testing/selftests/bpf/progs/cpumask_success.c b/tools/testing/selftests/bpf/progs/cpumask_success.c index 97ed08c4ff03..fe928ff72a06 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_success.c +++ b/tools/testing/selftests/bpf/progs/cpumask_success.c @@ -423,3 +423,36 @@ int BPF_PROG(test_insert_kptr_get_release, struct task_struct *task, u64 clone_f return 0; } + +SEC("tp_btf/task_newtask") +int BPF_PROG(test_global_mask_rcu, struct task_struct *task, u64 clone_flags) +{ + struct bpf_cpumask *local, *prev; + + if (!is_test_task()) + return 0; + + local = create_cpumask(); + if (!local) + return 0; + + prev = bpf_kptr_xchg(&global_mask, local); + if (prev) { + bpf_cpumask_release(prev); + err = 3; + return 0; + } + + bpf_rcu_read_lock(); + local = global_mask; + if (!local) { + err = 4; + bpf_rcu_read_unlock(); + return 0; + } + + bpf_cpumask_test_cpu(0, (const struct cpumask *)local); + bpf_rcu_read_unlock(); + + return 0; +} From patchwork Thu Mar 16 05:40:27 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13177006 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 E4931C6FD19 for ; Thu, 16 Mar 2023 05:41:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229845AbjCPFk7 (ORCPT ); Thu, 16 Mar 2023 01:40:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229790AbjCPFkp (ORCPT ); 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Wed, 15 Mar 2023 22:40:40 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:7f57]) by smtp.gmail.com with ESMTPSA id j5-20020a37b905000000b00745bca3c8a0sm5145783qkf.43.2023.03.15.22.40.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Mar 2023 22:40:40 -0700 (PDT) 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@fb.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 Subject: [PATCH bpf-next v2 4/5] bpf: Remove bpf_cpumask_kptr_get() kfunc Date: Thu, 16 Mar 2023 00:40:27 -0500 Message-Id: <20230316054028.88924-5-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230316054028.88924-1-void@manifault.com> References: <20230316054028.88924-1-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 struct bpf_cpumask is RCU safe, there's no need for this kfunc. Rather than doing the following: private(MASK) static struct bpf_cpumask __kptr *global; int BPF_PROG(prog, s32 cpu, ...) { struct bpf_cpumask *cpumask; bpf_rcu_read_lock(); cpumask = bpf_cpumask_kptr_get(&global); if (!cpumask) { bpf_rcu_read_unlock(); return -1; } bpf_cpumask_setall(cpumask); ... bpf_cpumask_release(cpumask); bpf_rcu_read_unlock(); } Programs can instead simply do (assume same global cpumask): int BPF_PROG(prog, ...) { struct bpf_cpumask *cpumask; bpf_rcu_read_lock(); cpumask = global; if (!cpumask) { bpf_rcu_read_unlock(); return -1; } bpf_cpumask_setall(cpumask); ... bpf_rcu_read_unlock(); } In other words, no extra atomic acquire / release, and less boilerplate code. This patch removes both the kfunc, as well as its selftests and documentation. Signed-off-by: David Vernet --- kernel/bpf/cpumask.c | 29 ------------------ .../selftests/bpf/prog_tests/cpumask.c | 1 - .../selftests/bpf/progs/cpumask_common.h | 1 - .../selftests/bpf/progs/cpumask_failure.c | 24 --------------- .../selftests/bpf/progs/cpumask_success.c | 30 ------------------- 5 files changed, 85 deletions(-) diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c index 98eea62b6b7b..db9da2194c1a 100644 --- a/kernel/bpf/cpumask.c +++ b/kernel/bpf/cpumask.c @@ -82,34 +82,6 @@ __bpf_kfunc struct bpf_cpumask *bpf_cpumask_acquire(struct bpf_cpumask *cpumask) return cpumask; } -/** - * bpf_cpumask_kptr_get() - Attempt to acquire a reference to a BPF cpumask - * stored in a map. - * @cpumaskp: A pointer to a BPF cpumask map value. - * - * Attempts to acquire a reference to a BPF cpumask stored in a map value. The - * cpumask returned by this function must either be embedded in a map as a - * kptr, or freed with bpf_cpumask_release(). This function may return NULL if - * no BPF cpumask was found in the specified map value. - */ -__bpf_kfunc struct bpf_cpumask *bpf_cpumask_kptr_get(struct bpf_cpumask **cpumaskp) -{ - struct bpf_cpumask *cpumask; - - /* The BPF memory allocator frees memory backing its caches in an RCU - * callback. Thus, we can safely use RCU to ensure that the cpumask is - * safe to read. - */ - rcu_read_lock(); - - cpumask = READ_ONCE(*cpumaskp); - if (cpumask && !refcount_inc_not_zero(&cpumask->usage)) - cpumask = NULL; - - rcu_read_unlock(); - return cpumask; -} - static void cpumask_free_cb(struct rcu_head *head) { struct bpf_cpumask *cpumask; @@ -435,7 +407,6 @@ BTF_SET8_START(cpumask_kfunc_btf_ids) BTF_ID_FLAGS(func, bpf_cpumask_create, KF_ACQUIRE | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cpumask_release, KF_RELEASE | KF_TRUSTED_ARGS) BTF_ID_FLAGS(func, bpf_cpumask_acquire, KF_ACQUIRE | KF_TRUSTED_ARGS) -BTF_ID_FLAGS(func, bpf_cpumask_kptr_get, KF_ACQUIRE | KF_KPTR_GET | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cpumask_first, KF_RCU) BTF_ID_FLAGS(func, bpf_cpumask_first_zero, KF_RCU) BTF_ID_FLAGS(func, bpf_cpumask_set_cpu, KF_RCU) diff --git a/tools/testing/selftests/bpf/prog_tests/cpumask.c b/tools/testing/selftests/bpf/prog_tests/cpumask.c index 6c0fe23498c7..cdf4acc18e4c 100644 --- a/tools/testing/selftests/bpf/prog_tests/cpumask.c +++ b/tools/testing/selftests/bpf/prog_tests/cpumask.c @@ -16,7 +16,6 @@ static const char * const cpumask_success_testcases[] = { "test_copy_any_anyand", "test_insert_leave", "test_insert_remove_release", - "test_insert_kptr_get_release", "test_global_mask_rcu", }; diff --git a/tools/testing/selftests/bpf/progs/cpumask_common.h b/tools/testing/selftests/bpf/progs/cpumask_common.h index 7623782fbd62..0c5b785a93e4 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_common.h +++ b/tools/testing/selftests/bpf/progs/cpumask_common.h @@ -26,7 +26,6 @@ struct array_map { struct bpf_cpumask *bpf_cpumask_create(void) __ksym; void bpf_cpumask_release(struct bpf_cpumask *cpumask) __ksym; struct bpf_cpumask *bpf_cpumask_acquire(struct bpf_cpumask *cpumask) __ksym; -struct bpf_cpumask *bpf_cpumask_kptr_get(struct bpf_cpumask **cpumask) __ksym; u32 bpf_cpumask_first(const struct cpumask *cpumask) __ksym; u32 bpf_cpumask_first_zero(const struct cpumask *cpumask) __ksym; void bpf_cpumask_set_cpu(u32 cpu, struct bpf_cpumask *cpumask) __ksym; diff --git a/tools/testing/selftests/bpf/progs/cpumask_failure.c b/tools/testing/selftests/bpf/progs/cpumask_failure.c index 9f726d55f747..db4f94e72b61 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_failure.c +++ b/tools/testing/selftests/bpf/progs/cpumask_failure.c @@ -94,30 +94,6 @@ int BPF_PROG(test_insert_remove_no_release, struct task_struct *task, u64 clone_ return 0; } -SEC("tp_btf/task_newtask") -__failure __msg("Unreleased reference") -int BPF_PROG(test_kptr_get_no_release, struct task_struct *task, u64 clone_flags) -{ - struct bpf_cpumask *cpumask; - struct __cpumask_map_value *v; - - cpumask = create_cpumask(); - if (!cpumask) - return 0; - - if (cpumask_map_insert(cpumask)) - return 0; - - v = cpumask_map_value_lookup(); - if (!v) - return 0; - - cpumask = bpf_cpumask_kptr_get(&v->cpumask); - - /* cpumask is never released. */ - return 0; -} - SEC("tp_btf/task_newtask") __failure __msg("NULL pointer passed to trusted arg0") int BPF_PROG(test_cpumask_null, struct task_struct *task, u64 clone_flags) diff --git a/tools/testing/selftests/bpf/progs/cpumask_success.c b/tools/testing/selftests/bpf/progs/cpumask_success.c index fe928ff72a06..2fcdd7f68ac7 100644 --- a/tools/testing/selftests/bpf/progs/cpumask_success.c +++ b/tools/testing/selftests/bpf/progs/cpumask_success.c @@ -394,36 +394,6 @@ int BPF_PROG(test_insert_remove_release, struct task_struct *task, u64 clone_fla return 0; } -SEC("tp_btf/task_newtask") -int BPF_PROG(test_insert_kptr_get_release, struct task_struct *task, u64 clone_flags) -{ - struct bpf_cpumask *cpumask; - struct __cpumask_map_value *v; - - cpumask = create_cpumask(); - if (!cpumask) - return 0; - - if (cpumask_map_insert(cpumask)) { - err = 3; - return 0; - } - - v = cpumask_map_value_lookup(); - if (!v) { - err = 4; - return 0; - } - - cpumask = bpf_cpumask_kptr_get(&v->cpumask); - if (cpumask) - bpf_cpumask_release(cpumask); - else - err = 5; - - return 0; -} - SEC("tp_btf/task_newtask") int BPF_PROG(test_global_mask_rcu, struct task_struct *task, u64 clone_flags) { From patchwork Thu Mar 16 05:40:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13177007 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 211DEC7618A for ; 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Wed, 15 Mar 2023 22:40:42 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:7f57]) by smtp.gmail.com with ESMTPSA id q8-20020a374308000000b0074589d41342sm5152303qka.17.2023.03.15.22.40.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Mar 2023 22:40:41 -0700 (PDT) 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@fb.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 Subject: [PATCH bpf-next v2 5/5] bpf,docs: Remove bpf_cpumask_kptr_get() from documentation Date: Thu, 16 Mar 2023 00:40:28 -0500 Message-Id: <20230316054028.88924-6-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230316054028.88924-1-void@manifault.com> References: <20230316054028.88924-1-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 kfunc no longer exists, we can remove it and instead describe how RCU can be used to get a struct bpf_cpumask from a map value. This patch updates the BPF documentation accordingly. Signed-off-by: David Vernet --- Documentation/bpf/cpumasks.rst | 30 ++++++++++-------------------- 1 file changed, 10 insertions(+), 20 deletions(-) diff --git a/Documentation/bpf/cpumasks.rst b/Documentation/bpf/cpumasks.rst index 75344cd230e5..41efd8874eeb 100644 --- a/Documentation/bpf/cpumasks.rst +++ b/Documentation/bpf/cpumasks.rst @@ -117,12 +117,7 @@ For example: As mentioned and illustrated above, these ``struct bpf_cpumask *`` objects can also be stored in a map and used as kptrs. If a ``struct bpf_cpumask *`` is in a map, the reference can be removed from the map with bpf_kptr_xchg(), or -opportunistically acquired with bpf_cpumask_kptr_get(): - -.. kernel-doc:: kernel/bpf/cpumask.c - :identifiers: bpf_cpumask_kptr_get - -Here is an example of a ``struct bpf_cpumask *`` being retrieved from a map: +opportunistically acquired using RCU: .. code-block:: c @@ -144,7 +139,7 @@ Here is an example of a ``struct bpf_cpumask *`` being retrieved from a map: /** * A simple example tracepoint program showing how a * struct bpf_cpumask * kptr that is stored in a map can - * be acquired using the bpf_cpumask_kptr_get() kfunc. + * be passed to kfuncs using RCU protection. */ SEC("tp_btf/cgroup_mkdir") int BPF_PROG(cgrp_ancestor_example, struct cgroup *cgrp, const char *path) @@ -158,26 +153,21 @@ Here is an example of a ``struct bpf_cpumask *`` being retrieved from a map: if (!v) return -ENOENT; + bpf_rcu_read_lock(); /* Acquire a reference to the bpf_cpumask * kptr that's already stored in the map. */ - kptr = bpf_cpumask_kptr_get(&v->cpumask); - if (!kptr) + kptr = v->cpumask; + if (!kptr) { /* If no bpf_cpumask was present in the map, it's because * we're racing with another CPU that removed it with * bpf_kptr_xchg() between the bpf_map_lookup_elem() - * above, and our call to bpf_cpumask_kptr_get(). - * bpf_cpumask_kptr_get() internally safely handles this - * race, and will return NULL if the cpumask is no longer - * present in the map by the time we invoke the kfunc. + * above, and our load of the pointer from the map. */ + bpf_rcu_read_unlock(); return -EBUSY; + } - /* Free the reference we just took above. Note that the - * original struct bpf_cpumask * kptr is still in the map. It will - * be freed either at a later time if another context deletes - * it from the map, or automatically by the BPF subsystem if - * it's still present when the map is destroyed. - */ - bpf_cpumask_release(kptr); + bpf_cpumask_setall(kptr); + bpf_rcu_read_unlock(); return 0; }