From patchwork Tue Nov 30 01:29:40 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Hao Luo X-Patchwork-Id: 12646149 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 4CA66C433EF for ; Tue, 30 Nov 2021 01:29:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236288AbhK3BdO (ORCPT ); Mon, 29 Nov 2021 20:33:14 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46614 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236282AbhK3BdO (ORCPT ); Mon, 29 Nov 2021 20:33:14 -0500 Received: from mail-pl1-x649.google.com (mail-pl1-x649.google.com [IPv6:2607:f8b0:4864:20::649]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 58434C061574 for ; Mon, 29 Nov 2021 17:29:56 -0800 (PST) Received: by mail-pl1-x649.google.com with SMTP id j6-20020a17090276c600b0014377d8ede3so7281806plt.21 for ; Mon, 29 Nov 2021 17:29:56 -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=cNX39YmimwuX4mdXBgMYmfyTx7hzHdSKI43Z5rrPPBA=; b=eWnxmrJ8HsAvvpVZ0nyg0cw31RqVgXGSVXZ/c+ljm4dTyZpBt9B7XW0VUqrrgC2mC1 AnXi0ESreHA7zqsSpsj+iZssDo60W8+XBDX4qg9xsciSLorrVfNj4stMejy0fmKfr4hp pN+g5hbw6sqs5yxxVj/Sa45tKFNBOhH4vmQBDelKmR7U3s5/gw+IJ5zQV27+dj3l31CO Gl3OyBdbHcP4SIQJTx1xGeyA5bFhn/tjD21xAnf2omthfcqSLd9OC+8ulsnh4mbA8PBI BmRwnwdXBG5YVpQVe8l3jnjECiTrZhTEs9vtvvArlVoNHjts1RI1wbCqQ7J/Co1XVJDv t4GQ== 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=cNX39YmimwuX4mdXBgMYmfyTx7hzHdSKI43Z5rrPPBA=; b=HK2O1xKmNFrMaxwAEsN/cCMGeY0z69q8HglI9gT0BRAf7di2bQqfdGrAv1yT/8DSjo cI0fdTmaknkAr0PmBRghrka7eE8FK37aMg0ldnfzgxE5WiLroQCneOtVpi+jZgSSk35F JFBcmqEpgVvNSquPwqlwcuV7UCsl+GL9Z9glF8YgIenidR/W+xCSFoQYP8tgTcb61Ohf BJuTWYQOwY+2U5gcBqA+9rx+GNZYIT16cGFOkeBVwd9SlJ6tBXt5LLwq9guCZY6STtBa G6+/N99OA2nbhzsozqF+tb+BRrHJrtQpJUQx5/jDcfMVT1xcdW9vXcDVIMiPPmNtjt88 lI/g== X-Gm-Message-State: AOAM532xlBtyCL0wSf052GDyRWwiUC6Q9Q7o44TLWqn7pVd7eM13GwgY BfFGBAHA0H/Ew32N6hL6PGsEmfjlz1k= X-Google-Smtp-Source: ABdhPJzCUUwsHuYCXYCHfg/4DPK7WiwDtk2Fw+XOK87kM4e9rBJ/c76sSmV1CN925Bg9kvBmWUIqJOHbu7A= X-Received: from haoluo.svl.corp.google.com ([2620:15c:2cd:202:bbf5:5c09:9dfe:483c]) (user=haoluo job=sendgmr) by 2002:a17:90b:4c85:: with SMTP id my5mr2120747pjb.26.1638235795706; Mon, 29 Nov 2021 17:29:55 -0800 (PST) Date: Mon, 29 Nov 2021 17:29:40 -0800 In-Reply-To: <20211130012948.380602-1-haoluo@google.com> Message-Id: <20211130012948.380602-2-haoluo@google.com> Mime-Version: 1.0 References: <20211130012948.380602-1-haoluo@google.com> X-Mailer: git-send-email 2.34.0.384.gca35af8252-goog Subject: [RFC PATCH bpf-next v2 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 X-Patchwork-State: RFC 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 types" 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 followed patches rewrites arg_types, ret_types and reg_types respectively. Signed-off-by: Hao Luo --- include/linux/bpf.h | 50 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 50 insertions(+) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index cc7a0c36e7df..b592b3f7d223 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -297,6 +297,37 @@ 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, +}; + +#define BPF_BASE_TYPE_MASK GENMASK(BPF_BASE_TYPE_BITS, 0) + +/* 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)) + +/* extract base type. */ +#define BPF_BASE_TYPE(x) ((x) & BPF_BASE_TYPE_MASK) + +/* extract flags from an extended type. */ +#define BPF_TYPE_FLAG(x) ((enum bpf_type_flag)((x) & ~BPF_BASE_TYPE_MASK)) + /* function argument constraints */ enum bpf_arg_type { ARG_DONTCARE = 0, /* unused argument in helper function */ @@ -343,7 +374,13 @@ 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 +396,14 @@ 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 +505,13 @@ 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.