From patchwork Fri Jan 20 19:25:18 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Vernet X-Patchwork-Id: 13110433 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 1652CC05027 for ; Fri, 20 Jan 2023 19:25:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230338AbjATTZr (ORCPT ); Fri, 20 Jan 2023 14:25:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57466 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230006AbjATTZj (ORCPT ); Fri, 20 Jan 2023 14:25:39 -0500 Received: from mail-vk1-f172.google.com (mail-vk1-f172.google.com [209.85.221.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 257638BA8F; Fri, 20 Jan 2023 11:25:32 -0800 (PST) Received: by mail-vk1-f172.google.com with SMTP id q21so3033979vka.3; Fri, 20 Jan 2023 11:25:32 -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=+w2MA7VgCoYzPDh+fd2OtSy1Z701e04EjKWG3BmqBSU=; b=BIu/K/Iem93j7QS66RsmIz3g2CpfsBUu/iHgX0bnoZkltvVUy0uXe+QJYLF9tty+U/ XlE9ngRUA8CD29XHL1AiQ18xRPMdSC/Ysj1Eci/VYWWWSMZAfjv9iXIQpNyYQ07DKpy5 vJmWtums6ZmCo6D42WWf1C/iA+CDr8fYbNrWvAF67FtSWeIynAnuiZOo8urmEUHY1aus qtEvWQxerDQp2+mbD+/vNNCoq8WgC7u4eciIawQxrjUi+fVwQy2/cpqMRJmlvtTQQh8Q RN+5oW09vZw0/BGDQ0fa7el4H47iBpWSFFYHPjrBPFtlq2HsudsJwIT97f2qGr6FI5jY snmQ== X-Gm-Message-State: AFqh2krSV0UPG87BYWQVI6aIkTZWn3G80h1NxLazBZ7H8TEh/yAIW9N1 DEkhuUP2oO5QadSvb5PYeJ/9cs2UEd95stZc X-Google-Smtp-Source: AMrXdXsMvzdKXfLOdoIZv+u1SE20F9JHZiMyk8pDiiSaS1/SjgUoOQYbaK1yHSQwmFw/aSryVCPykA== X-Received: by 2002:a05:6122:2086:b0:3dd:f28e:ca49 with SMTP id i6-20020a056122208600b003ddf28eca49mr13277770vkd.7.1674242730641; Fri, 20 Jan 2023 11:25:30 -0800 (PST) Received: from localhost ([2620:10d:c091:480::1:2fc9]) by smtp.gmail.com with ESMTPSA id x6-20020a05620a448600b0070736988c10sm4738108qkp.110.2023.01.20.11.25.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 20 Jan 2023 11:25:30 -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, tj@kernel.org, memxor@gmail.com Subject: [PATCH bpf-next v2 4/9] bpf: Enable cpumasks to be queried and used as kptrs Date: Fri, 20 Jan 2023 13:25:18 -0600 Message-Id: <20230120192523.3650503-5-void@manifault.com> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230120192523.3650503-1-void@manifault.com> References: <20230120192523.3650503-1-void@manifault.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net Certain programs may wish to be able to query cpumasks. For example, if a program that is tracing percpu operations may wish to track which tasks end up running on which CPUs, and it could be useful to associate that with the tasks' cpumasks. Similarly, a program tracking NUMA allocations, CPU scheduling domains, etc, would potentially benefit from being able to see which CPUs a task could be migrated to, etc. This patch enables these such cases by introducing a series of bpf_cpumask_* kfuncs. Amongst these kfuncs, there are two separate "classes" of operations: 1. kfuncs which allow the caller to allocate and mutate their own cpumasks in the form of a struct bpf_cpumask * object. Such kfuncs include e.g. bpf_cpumask_create() to allocate the cpumask, and bpf_cpumask_or() to mutate it. "Regular" cpumasks such as p->cpus_ptr may not be passed to these kfuncs, and the verifier will ensure this is the case by comparing BTF IDs. 2. Read-only operations which operate on const struct cpumask * arguments. For example, bpf_cpumask_test_cpu(), which tests whether a CPU is set in the cpumask. Any trusted struct cpumask * or struct bpf_cpumask * may be passed to these kfuncs. The verifier allows struct bpf_cpumask * even though the kfunc is defined with struct cpumask * because the first element of a struct bpf_cpumask is a cpumask_t, so it is safe to cast. A follow-on patch will add selftests which validate these kfuncs, and another will document them. Note that some of the kfuncs that were added would benefit from additional verification logic. For example, any kfunc taking a CPU argument that exceeds the number of CPUs on the system, etc. For now, we silently check for and ignore these cases at runtime. When we have e.g. per-argument kfunc flags, it might be helpful to add another KF_CPU-type flag that specifies that the verifier should validate that it's a valid CPU. Signed-off-by: David Vernet --- kernel/bpf/Makefile | 1 + kernel/bpf/cpumask.c | 269 +++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 270 insertions(+) create mode 100644 kernel/bpf/cpumask.c diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile index 3a12e6b400a2..02242614dcc7 100644 --- a/kernel/bpf/Makefile +++ b/kernel/bpf/Makefile @@ -36,6 +36,7 @@ obj-$(CONFIG_DEBUG_INFO_BTF) += sysfs_btf.o endif ifeq ($(CONFIG_BPF_JIT),y) obj-$(CONFIG_BPF_SYSCALL) += bpf_struct_ops.o +obj-$(CONFIG_BPF_SYSCALL) += cpumask.o obj-${CONFIG_BPF_LSM} += bpf_lsm.o endif obj-$(CONFIG_BPF_PRELOAD) += preload/ diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c new file mode 100644 index 000000000000..92eedc84dbfc --- /dev/null +++ b/kernel/bpf/cpumask.c @@ -0,0 +1,269 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2023 Meta, Inc + */ +#include +#include +#include +#include +#include + +/** + * struct bpf_cpumask - refcounted BPF cpumask wrapper structure + * @cpumask: The actual cpumask embedded in the struct. + * @usage: Object reference counter. When the refcount goes to 0, the + * memory is released back to the BPF allocator, which provides + * RCU safety. + * + * Note that we explicitly embed a cpumask_t rather than a cpumask_var_t. This + * is done to avoid confusing the verifier due to the typedef of cpumask_var_t + * changing depending on whether CONFIG_CPUMASK_OFFSTACK is defined or not. See + * the details in . The consequence is that this structure is + * likely a bit larger than it needs to be when CONFIG_CPUMASK_OFFSTACK is + * defined due to embedding the whole NR_CPUS-size bitmap, but the extra memory + * overhead is minimal. For the more typical case of CONFIG_CPUMASK_OFFSTACK + * not being defined, the structure is the same size regardless. + */ +struct bpf_cpumask { + cpumask_t cpumask; + refcount_t usage; +}; + +static struct bpf_mem_alloc bpf_cpumask_ma; + +static bool cpu_valid(u32 cpu) +{ + return cpu < nr_cpu_ids; +} + +__diag_push(); +__diag_ignore_all("-Wmissing-prototypes", + "Global kfuncs as their definitions will be in BTF"); + +struct bpf_cpumask *bpf_cpumask_create(void) +{ + struct bpf_cpumask *cpumask; + + cpumask = bpf_mem_alloc(&bpf_cpumask_ma, sizeof(*cpumask)); + if (!cpumask) + return NULL; + + memset(cpumask, 0, sizeof(*cpumask)); + refcount_set(&cpumask->usage, 1); + + return cpumask; +} + +struct bpf_cpumask *bpf_cpumask_acquire(struct bpf_cpumask *cpumask) +{ + refcount_inc(&cpumask->usage); + return cpumask; +} + +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; +} + +void bpf_cpumask_release(struct bpf_cpumask *cpumask) +{ + if (!cpumask) + return; + + if (refcount_dec_and_test(&cpumask->usage)) { + migrate_disable(); + bpf_mem_free(&bpf_cpumask_ma, cpumask); + migrate_enable(); + } +} + +u32 bpf_cpumask_first(const struct cpumask *cpumask) +{ + return cpumask_first(cpumask); +} + +u32 bpf_cpumask_first_zero(const struct cpumask *cpumask) +{ + return cpumask_first_zero(cpumask); +} + +void bpf_cpumask_set_cpu(u32 cpu, struct bpf_cpumask *cpumask) +{ + if (!cpu_valid(cpu)) + return; + + cpumask_set_cpu(cpu, (struct cpumask *)cpumask); +} + +void bpf_cpumask_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask) +{ + if (!cpu_valid(cpu)) + return; + + cpumask_clear_cpu(cpu, (struct cpumask *)cpumask); +} + +bool bpf_cpumask_test_cpu(u32 cpu, const struct cpumask *cpumask) +{ + if (!cpu_valid(cpu)) + return false; + + return cpumask_test_cpu(cpu, (struct cpumask *)cpumask); +} + +bool bpf_cpumask_test_and_set_cpu(u32 cpu, struct bpf_cpumask *cpumask) +{ + if (!cpu_valid(cpu)) + return false; + + return cpumask_test_and_set_cpu(cpu, (struct cpumask *)cpumask); +} + +bool bpf_cpumask_test_and_clear_cpu(u32 cpu, struct bpf_cpumask *cpumask) +{ + if (!cpu_valid(cpu)) + return false; + + return cpumask_test_and_clear_cpu(cpu, (struct cpumask *)cpumask); +} + +void bpf_cpumask_setall(struct bpf_cpumask *cpumask) +{ + cpumask_setall((struct cpumask *)cpumask); +} + +void bpf_cpumask_clear(struct bpf_cpumask *cpumask) +{ + cpumask_clear((struct cpumask *)cpumask); +} + +bool bpf_cpumask_and(struct bpf_cpumask *dst, + const struct cpumask *src1, + const struct cpumask *src2) +{ + return cpumask_and((struct cpumask *)dst, src1, src2); +} + +void bpf_cpumask_or(struct bpf_cpumask *dst, + const struct cpumask *src1, + const struct cpumask *src2) +{ + cpumask_or((struct cpumask *)dst, src1, src2); +} + +void bpf_cpumask_xor(struct bpf_cpumask *dst, + const struct cpumask *src1, + const struct cpumask *src2) +{ + cpumask_xor((struct cpumask *)dst, src1, src2); +} + +bool bpf_cpumask_equal(const struct cpumask *src1, const struct cpumask *src2) +{ + return cpumask_equal(src1, src2); +} + +bool bpf_cpumask_intersects(const struct cpumask *src1, const struct cpumask *src2) +{ + return cpumask_intersects(src1, src2); +} + +bool bpf_cpumask_subset(const struct cpumask *src1, const struct cpumask *src2) +{ + return cpumask_subset(src1, src2); +} + +bool bpf_cpumask_empty(const struct cpumask *cpumask) +{ + return cpumask_empty(cpumask); +} + +bool bpf_cpumask_full(const struct cpumask *cpumask) +{ + return cpumask_full(cpumask); +} + +void bpf_cpumask_copy(struct bpf_cpumask *dst, const struct cpumask *src) +{ + cpumask_copy((struct cpumask *)dst, src); +} + +u32 bpf_cpumask_any(const struct cpumask *cpumask) +{ + return cpumask_any(cpumask); +} + +u32 bpf_cpumask_any_and(const struct cpumask *src1, const struct cpumask *src2) +{ + return cpumask_any_and(src1, src2); +} + +__diag_pop(); + +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_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_first_zero, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_set_cpu, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_clear_cpu, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_test_cpu, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_test_and_set_cpu, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_test_and_clear_cpu, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_setall, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_clear, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_and, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_or, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_xor, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_equal, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_intersects, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_subset, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_empty, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_full, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_copy, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_any, KF_TRUSTED_ARGS) +BTF_ID_FLAGS(func, bpf_cpumask_any_and, KF_TRUSTED_ARGS) +BTF_SET8_END(cpumask_kfunc_btf_ids) + +static const struct btf_kfunc_id_set cpumask_kfunc_set = { + .owner = THIS_MODULE, + .set = &cpumask_kfunc_btf_ids, +}; + +BTF_ID_LIST(cpumask_dtor_ids) +BTF_ID(struct, bpf_cpumask) +BTF_ID(func, bpf_cpumask_release) + +static int __init cpumask_kfunc_init(void) +{ + int ret; + const struct btf_id_dtor_kfunc cpumask_dtors[] = { + { + .btf_id = cpumask_dtor_ids[0], + .kfunc_btf_id = cpumask_dtor_ids[1] + }, + }; + + ret = bpf_mem_alloc_init(&bpf_cpumask_ma, 0, false); + ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &cpumask_kfunc_set); + ret = ret ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_STRUCT_OPS, &cpumask_kfunc_set); + return ret ?: register_btf_id_dtor_kfuncs(cpumask_dtors, + ARRAY_SIZE(cpumask_dtors), + THIS_MODULE); +} + +late_initcall(cpumask_kfunc_init);