From patchwork Wed Feb 21 01:23:24 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Kui-Feng Lee X-Patchwork-Id: 13564835 Received: from mail-yw1-f173.google.com (mail-yw1-f173.google.com [209.85.128.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1A1D65666 for ; Wed, 21 Feb 2024 01:23:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708478626; cv=none; b=Q9vdcWV0V2KadId+Y752Z+A6M9JBRM5LU9vk4el0EaEThSPAjixsknqG7sQNHRVSYKIg8v3NRq5OzSaoL4gwZ7wJ20t6m1OwFFXY1QS5RNi8G5rblQ4NCe8vCXGjruFgZowRLUucjcRcp7b/Lbim92VFqNMYOP4065ykaCAtr9o= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708478626; c=relaxed/simple; bh=M5b56MvbFN2+F8bzMhnHm+a+BVYzgfH5WrJpBurD9N8=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=nO3bTFy0wVVeBodo2LFlChlZH1sXigjSdOmkt+R4AOuipEJ5jxD8GKgTK+fIdu51POPOE1FOBrK+mjWponkk7HcRrLu+//4ud58e+qDT6+m5mrGCuR0VrTaFCC4q+uAQzWCrOERX681zoqgO0LlDXv3V6g7YOb8984SCiqQMYPE= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=C35CeE5E; arc=none smtp.client-ip=209.85.128.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="C35CeE5E" Received: by mail-yw1-f173.google.com with SMTP id 00721157ae682-607d8506099so59700537b3.0 for ; Tue, 20 Feb 2024 17:23:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1708478623; x=1709083423; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=WHHQj0Zeq5xAzYjYuMIobC7y/QzOmrc3C5mSoGi5804=; b=C35CeE5EmKXIo0DwAaXeH+52/rxCXtHwGFHnyO4518qVqk/qeJTPly4Kt4f18n5RjF ypAPnsNb/1cORJYmM5V438oaxdDZe2q2z4ZgzX1TEkr+aG5+JK2OBG1wVHdcmPO+30r0 btmxcoEWdYSZElPcs5krJtk5OCQvvhsDOXQhnIEbeYe7qnpwI82sdatTKmbPuP3Cftfi hArdTd4Di7+t6oIY0yQFEJXv5H7xGWiuf9num3kOfPNIG4ibCemszWwyy//XDLp7gqU3 T9jEI0xX6ipFNJqxJ1N8jRgF4ybeAopy6PvrsuT1ILahrsSfLF9wAFMnpG2fq8OJ9diH bN9A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1708478623; x=1709083423; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=WHHQj0Zeq5xAzYjYuMIobC7y/QzOmrc3C5mSoGi5804=; b=e9LvDzeXX3wQR2hC9WceETGpdNe8ibB63xZbjo8KonjOPckKJxZFmQwED91jF1Bm22 T4dyxuREEVVM6qFwB9Ft71UuIiJTTeCbOGr/lmRoRPrhC1HAKjJLv5qVQcqKQdgbhg7q 8lz4ZLAGN42h3P1bWF55mqJjD077ML5KPbnthPLElUVhKcrZHe3rSQp5H+Skevnv6uy4 OHyIVBv5qmOyv/xxan+GjVtdxjz6fkCj47JFwTdHzEfXVLYOBZB+Z6DwLX+s9DHszbPu iGMDWfSx/pMeMzsSmGWGHwHqBalo3shBn9qz3jt/rZ8P30hOo/0SvE+l+ClWt0tJM6Pu 2izg== X-Gm-Message-State: AOJu0YzChFQ6slV47TeGYNv2UUZGNj9M89y9/lXkaVepgrWm1T3ZTrLO v8A1VqqBrKlrm+jjiWAUFSHJUjRkktpmZYn5cHPkdPEG5Zafvh5/ye3pOsA0 X-Google-Smtp-Source: AGHT+IE6mpF789u+N/nQiOapxyHKadxA97YbFpYnrEV9jafqsZqFAdMVrFJxk0Y+taR8uyHeHgJR2Q== X-Received: by 2002:a81:a145:0:b0:607:9e4b:f0eb with SMTP id y66-20020a81a145000000b006079e4bf0ebmr15031138ywg.29.1708478623409; Tue, 20 Feb 2024 17:23:43 -0800 (PST) Received: from kickker.attlocal.net ([2600:1700:6cf8:1240:26eb:2942:8151:a089]) by smtp.gmail.com with ESMTPSA id j64-20020a0de043000000b00607ef065781sm2396801ywe.138.2024.02.20.17.23.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 20 Feb 2024 17:23:43 -0800 (PST) From: thinker.li@gmail.com To: bpf@vger.kernel.org, ast@kernel.org, martin.lau@linux.dev, song@kernel.org, kernel-team@meta.com, andrii@kernel.org Cc: sinquersw@gmail.com, kuifeng@meta.com, Kui-Feng Lee Subject: [PATCH bpf-next v3 0/5] Create shadow types for struct_ops maps in skeletons Date: Tue, 20 Feb 2024 17:23:24 -0800 Message-Id: <20240221012329.1387275-1-thinker.li@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net From: Kui-Feng Lee This patchset allows skeleton users to change the values of the fields in struct_ops maps at runtime. It will create a shadow type pointer in a skeleton for each struct_ops map, allowing users to access the values of fields through these pointers. For instance, if there is an integer field named "FOO" in a struct_ops map called "testmap", you can access the value of "FOO" in this way. skel->struct_ops.testmap->FOO = 13; With this feature, the users can pass flags or other data along with the map from the user space to the kernel without creating separate struct_ops map for different values in BPF. == Shadow Type == The shadow type of a struct_ops map is a variant of the original struct type of the map. The code generator translates each field in the original struct type to a field in the shadow type. The type of a field in the shadow type may not be the same as the corresponding field in the original struct type. For example, modifiers like volatile, const, etc., are removed from the fields in a shadow type. Function pointers are translated to pointers of struct bpf_program. Currently, only scalar types and function pointers are supported. Fields belonging to structs, unions, non-function pointers, arrays, or other types are not supported. For those unsupported fields, they are converted to arrays of characters to preserve their space within the original struct type. The padding between consecutive fields is handled by padding fields (__padding_*). This helps to maintain the memory layout consistent with the original struct_type. Here is an example of shadow types. The origin struct type of a struct_ops map is struct bpf_testmod_ops { int (*test_1)(void); void (*test_2)(int a, int b); /* Used to test nullable arguments. */ int (*test_maybe_null)(int dummy, struct task_struct *task); /* The following fields are used to test shadow copies. */ char onebyte; struct { int a; int b; } unsupported; int data; }; The struct_ops map, named testmod_1, of this type will be translated to a pointer in the shadow type. struct { struct { const struct bpf_program *test_1; const struct bpf_program *test_2; const struct bpf_program *test_maybe_null; char onebyte; char __padding_3[3]; char __padding_4[8]; int data; } *testmod_1; } struct_ops; == Convert st_ops->data to Shadow Type == libbpf converts st_ops->data to the format of the shadow type for each struct_ops map. This means that the bytes where function pointers are located are converted to the values of the pointers of struct bpf_program. The fields of other types are kept as they were. Libbpf will synchronize the pointers of struct bpf_program with st_ops->progs[] so that users can change function pointers (bpf_program) before loading the map. --- v2: https://lore.kernel.org/all/20240214020836.1845354-1-thinker.li@gmail.com/ v1: https://lore.kernel.org/all/20240124224130.859921-1-thinker.li@gmail.com/ Kui-Feng Lee (5): libbpf: expose resolve_func_ptr() through libbpf_internal.h. libbpf: set btf_value_type_id of struct bpf_map for struct_ops. libbpf: Convert st_ops->data to shadow type. bpftool: generated shadow variables for struct_ops maps. selftests/bpf: Test if shadow types work correctly. tools/bpf/bpftool/gen.c | 229 +++++++++++++++++- tools/lib/bpf/libbpf.c | 60 ++++- tools/lib/bpf/libbpf_internal.h | 1 + .../selftests/bpf/bpf_testmod/bpf_testmod.c | 11 +- .../selftests/bpf/bpf_testmod/bpf_testmod.h | 8 + .../bpf/prog_tests/test_struct_ops_module.c | 19 +- .../selftests/bpf/progs/struct_ops_module.c | 8 + 7 files changed, 328 insertions(+), 8 deletions(-)