From patchwork Mon Dec 6 23:22:19 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Luo X-Patchwork-Id: 12660497 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 680FAC433F5 for ; Mon, 6 Dec 2021 23:22:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343821AbhLFX0C (ORCPT ); Mon, 6 Dec 2021 18:26:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242479AbhLFX0C (ORCPT ); Mon, 6 Dec 2021 18:26:02 -0500 Received: from mail-pf1-x449.google.com (mail-pf1-x449.google.com [IPv6:2607:f8b0:4864:20::449]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4BD9EC061746 for ; Mon, 6 Dec 2021 15:22:33 -0800 (PST) Received: by mail-pf1-x449.google.com with SMTP id b26-20020aa7951a000000b004a815eb3a3aso7416596pfp.16 for ; Mon, 06 Dec 2021 15:22:33 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=E21RldZfy03eyCEIqqzDfAZe2+SS0wPacoHltYAwiG8=; b=g2/DMWBuIngBWHMY4tcr6K/wQ329mTY64H70g7ZQncijP7q6o4a1rkfAC2OXHaKRZO kunsnYhCnWsI8zcp8O8Rq+Va94gH+If7qnPQO8GQU7ihS9FI6EoKfnSoGG+cN4fIJQEM QpIPUpvp7Bo3yFh1o9Mq3ZueB6chhe2VZC49fHUITKyljvPPhjYsbQnRHDNlZuV6iFdF yPfsm/VHM2rQXGSPpCpPEH+m2jh9pCN9OYFJj4J964t7FDqYy5ZPto086Rv9DqZMtHC8 mtwtDwG7s/2zfUIzaHDlykxPYX/C6XSDCrCsGdnzySq+epGVbZkDfeNZJ6jQfqgouzRJ b2qQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=E21RldZfy03eyCEIqqzDfAZe2+SS0wPacoHltYAwiG8=; b=Hv8TcRn90HUDL8JT1qZoqaDy0BOTBZ9KT9pcLUUPCJX8b1dDTBloygr6u3Qjb4wEt/ QovZVLdAFwnD+mv90nQJ7+9i5giaS8rJHgPuYv88Q4/vNKpCtCxhivqEFKJeddmSaknQ Zxe7h6BBFiW2Phv2LC9C13fOECSGjcURIT+yGr2LNvPghogqWADSpFVH7t8Zmw2ZP004 Y2OtMRMq/g+3CoX84tjTn719/hy/DFJkRDsHk1s+msav3v5NOw1vCeEKgDh0sk7IgPmj ySf9qUzsOGYG7k2AO8oka12a/e+i6gAHv9OSQVHtToMWx+o/gAutk5KrbjFNs1ykvXYY L0Fg== X-Gm-Message-State: AOAM530fy+MsXaOrUNyqcgpZ+Q7JdejHX9QWQDQV8ALk4+exBNMEm3X6 p22c0ZREmINaMWIU6J20pmA16inQzIA= X-Google-Smtp-Source: ABdhPJxkSBVjAwin6+43Urghnd1WyBgqYpCfB0CL+L2968RX1rHD9MsqirQMQUWYi3FQLZ7aZoRM5JjbJC8= X-Received: from haoluo.svl.corp.google.com ([2620:15c:2cd:202:2977:d88c:3c3:c52a]) (user=haoluo job=sendgmr) by 2002:a17:902:9684:b0:143:cc70:6472 with SMTP id n4-20020a170902968400b00143cc706472mr47389006plp.70.1638832952798; Mon, 06 Dec 2021 15:22:32 -0800 (PST) Date: Mon, 6 Dec 2021 15:22:19 -0800 In-Reply-To: <20211206232227.3286237-1-haoluo@google.com> Message-Id: <20211206232227.3286237-2-haoluo@google.com> Mime-Version: 1.0 References: <20211206232227.3286237-1-haoluo@google.com> X-Mailer: git-send-email 2.34.1.400.ga245620fadb-goog Subject: [PATCH bpf-next v1 1/9] bpf: Introduce composable reg, ret and arg types. From: Hao Luo To: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann Cc: Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , bpf@vger.kernel.org, Hao Luo Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net There are some common properties shared between bpf reg, ret and arg values. For instance, a value may be a NULL pointer, or a pointer to a read-only memory. Previously, to express these properties, enumeration was used. For example, in order to test whether a reg value can be NULL, reg_type_may_be_null() simply enumerates all types that are possibly NULL. The problem of this approach is that it's not scalable and causes a lot of duplication. These properties can be combined, for example, a type could be either MAYBE_NULL or RDONLY, or both. This patch series rewrites the layout of reg_type, arg_type and ret_type, so that common properties can be extracted and represented as composable flag. For example, one can write ARG_PTR_TO_MEM | PTR_MAYBE_NULL which is equivalent to the previous ARG_PTR_TO_MEM_OR_NULL The type ARG_PTR_TO_MEM are called "base type" in this patch. Base types can be extended with flags. A flag occupies the higher bits while base types sits in the lower bits. This patch in particular sets up a set of macro for this purpose. The following patches will rewrite arg_types, ret_types and reg_types respectively. Signed-off-by: Hao Luo --- include/linux/bpf.h | 42 ++++++++++++++++++++++++++++++++++++ include/linux/bpf_verifier.h | 13 +++++++++++ 2 files changed, 55 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index cc7a0c36e7df..d8e6f8cd78a2 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -297,6 +297,29 @@ bool bpf_map_meta_equal(const struct bpf_map *meta0, extern const struct bpf_map_ops bpf_map_offload_ops; +/* bpf_type_flag contains a set of flags that are applicable to the values of + * arg_type, ret_type and reg_type. For example, a pointer value may be null, + * or a memory is read-only. We classify types into two categories: base types + * and extended types. Extended types are base types combined with a type flag. + * + * Currently there are no more than 32 base types in arg_type, ret_type and + * reg_types. + */ +#define BPF_BASE_TYPE_BITS 8 + +enum bpf_type_flag { + /* PTR may be NULL. */ + PTR_MAYBE_NULL = BIT(0 + BPF_BASE_TYPE_BITS), + + __BPF_TYPE_LAST_FLAG = PTR_MAYBE_NULL, +}; + +/* Max number of base types. */ +#define BPF_BASE_TYPE_LIMIT (1UL << BPF_BASE_TYPE_BITS) + +/* Max number of all types. */ +#define BPF_TYPE_LIMIT (__BPF_TYPE_LAST_FLAG | (__BPF_TYPE_LAST_FLAG - 1)) + /* function argument constraints */ enum bpf_arg_type { ARG_DONTCARE = 0, /* unused argument in helper function */ @@ -343,7 +366,13 @@ enum bpf_arg_type { ARG_PTR_TO_CONST_STR, /* pointer to a null terminated read-only string */ ARG_PTR_TO_TIMER, /* pointer to bpf_timer */ __BPF_ARG_TYPE_MAX, + + /* This must be the last entry. Its purpose is to ensure the enum is + * wide enough to hold the higher bits reserved for bpf_type_flag. + */ + __BPF_ARG_TYPE_LIMIT = BPF_TYPE_LIMIT, }; +static_assert(__BPF_ARG_TYPE_MAX <= BPF_BASE_TYPE_LIMIT); /* type of values returned from helper functions */ enum bpf_return_type { @@ -359,7 +388,14 @@ enum bpf_return_type { RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL, /* returns a pointer to a valid memory or a btf_id or NULL */ RET_PTR_TO_MEM_OR_BTF_ID, /* returns a pointer to a valid memory or a btf_id */ RET_PTR_TO_BTF_ID, /* returns a pointer to a btf_id */ + __BPF_RET_TYPE_MAX, + + /* This must be the last entry. Its purpose is to ensure the enum is + * wide enough to hold the higher bits reserved for bpf_type_flag. + */ + __BPF_RET_TYPE_LIMIT = BPF_TYPE_LIMIT, }; +static_assert(__BPF_RET_TYPE_MAX <= BPF_BASE_TYPE_LIMIT); /* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs * to in-kernel helper functions and for adjusting imm32 field in BPF_CALL @@ -461,7 +497,13 @@ enum bpf_reg_type { PTR_TO_FUNC, /* reg points to a bpf program function */ PTR_TO_MAP_KEY, /* reg points to a map element key */ __BPF_REG_TYPE_MAX, + + /* This must be the last entry. Its purpose is to ensure the enum is + * wide enough to hold the higher bits reserved for bpf_type_flag. + */ + __BPF_REG_TYPE_LIMIT = BPF_TYPE_LIMIT, }; +static_assert(__BPF_REG_TYPE_MAX <= BPF_BASE_TYPE_LIMIT); /* The information passed from prog-specific *_is_valid_access * back to the verifier. diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index c8a78e830fca..0840c3025822 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -529,5 +529,18 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, struct bpf_attach_target_info *tgt_info); void bpf_free_kfunc_btf_tab(struct bpf_kfunc_btf_tab *tab); +#define BPF_BASE_TYPE_MASK GENMASK(BPF_BASE_TYPE_BITS - 1, 0) + +/* extract base type from bpf_{arg, return, reg}_type. */ +static inline u32 base_type(u32 type) +{ + return type & BPF_BASE_TYPE_MASK; +} + +/* extract flags from an extended type. See bpf_type_flag in bpf.h. */ +static inline u32 type_flag(u32 type) +{ + return type & ~BPF_BASE_TYPE_MASK; +} #endif /* _LINUX_BPF_VERIFIER_H */