From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f52.google.com (mail-pj1-f52.google.com [209.85.216.52]) (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 286BD2E2DC1 for ; Tue, 4 Nov 2025 17:26:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762277218; cv=none; b=hMMRwaSyFvmvqvoIrqcJXzsr9FonhzvKS+v+WKq1ZhCNP5lKqd1lekZfcyOxpk7sQo/DULBi9b/7pk+sOOAtoq6ktWHTmgih0IoUOYycw+aWQZcNENP5Jo1N3Y/J+FRNVHzx036vU0Jm6fFdO7ov8QWW17soIJ3wHT2cM1md5JA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762277218; c=relaxed/simple; bh=Wevo2Y4OmrLXFTmuAJOHd+4d+3TkpCLlFEfPIh3FzEw=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Pcw56H0keQRr0f7KEBV9kYbTZdgan6iSCumaNUs9cY6beFBe7g598/9NT8shfVvWpglfn+TkWx8g+2BTEN5Eueiujf3mVLk291zjyGQQM3sVdcgrVKjLLoFVRXMPbfSLzBM5p6RgeATu7h5/4uZRu7L2gmazOW/QvgYUmSvnSd8= 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=Zax35KqU; arc=none smtp.client-ip=209.85.216.52 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="Zax35KqU" Received: by mail-pj1-f52.google.com with SMTP id 98e67ed59e1d1-33db8fde85cso5583876a91.0 for ; Tue, 04 Nov 2025 09:26:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1762277216; x=1762882016; 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=JSh4mlRZT0Y24WMccxIDboDo6bfkByxubsl31YznsC4=; b=Zax35KqUsSCTmAmObdHYRkgYSP9cY6kqOEb7JSdAV7XHi6GITegAyLr1cSSbt2SfFG rHBwWXhWBTwhfOs6DZRr10ZOldPXQffeQT4VGeRASWhxjxFNGIKf5jOvUGIOgVuzibgg pTUhEtSoxE3hVLKGJGXY/965Z7b5+/9SA8yk09g726v/srpD11ifot9MkKO2ybRvuPRi u7c8OvqmJW4oba2dRAYI13Kh5juI8ajPlJxc4px55vMem96CP4vd8Lpp944GEhHkX11l MFrZLOCy7/IN1xMxDQWGqTc1WHIk5uCW6n/uVCv2VjdKVoivhdWFyVqVh5iSdjjAhvxk mZ4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1762277216; x=1762882016; 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=JSh4mlRZT0Y24WMccxIDboDo6bfkByxubsl31YznsC4=; b=H097jDYW4BVSVtRZXIfniasgslnxSjFinGwUBT/VoLufkOqa1VFCp7OSZCarGaDGkK HpGD6AI+dvsfAtl6iSqYzxDy2rGZtmjHi6rwnoFokUBh5Q/mQpbaDESQuf5KCRyf/J0n Rxh10QL/72NLccP2cAkUmOcK3D2FahxYyAouPEwIjtMiW04yKuPaTpir1NIoXkJGWGgL Z2iWwF+wVZFK2K1IKvdfcnTp/jugga/bMQ635Ikmv27POqOKOWPhA9IhNXo/SMfRNO6H tGNbswVcn3qUuDSJgBPGyBVOrg4PpTH+L1m69iuDuERzl30VKA4JisSNSgLn/AwJHiee GLLA== X-Gm-Message-State: AOJu0YwVPH5Hw5nj7fPrtyDcM7qtEmn4xgttG0rgCux8WqeL7XA2ts96 Cp3r0iKeK6kFwcZbt5qqq2MBn0u5XXVFeI3DCubhBO43f+mYvZjzYg/8dGIyAA== X-Gm-Gg: ASbGncucuIWvSTtZrGznX5lsM+Hdq0laBJ4NqcF+EL1T6g7/zeaw1neO4KEA4n7/MQX sh6vNoVKo8a3Ysz0My9YWU9/FQTd8+Awqc4aBNdRG718z8qQxo+AaAYVemNIvgakR8+uDtG+64f +7FPe4t7sI481qvHXYP9X76y4RS0krLcvZPTmsDKV3LcArUH/37i6KvPm2pCtiuhckY9a+BGrYe HvPnfmuoO+wpPiJcRPhbdMJKvr0oFEtDzBJ3NtA6C4XrTYhqVVtqt0ztSbomRnS0t5QhcdGJeYt cG6uBfk8RF6hoG33uiyMQ8nNcdX8QyVPO6GsLM/ITawJVeJFiQjmljJFtFG7TneVzCxEViuRq4B conGcp/XODYVDm462LdMfl+OHAG0E8PcbbNC6xP+mT+cRWF4MuTq0kLexyq3lZwmE7zA= X-Google-Smtp-Source: AGHT+IFw2guSVLHKtwMI2ykXFRrbGXDUlz5eJAzpQePpdyOsYuNehk5p+cRdkY2/ZbSoIywZBVXbbA== X-Received: by 2002:a17:903:1ce:b0:292:dca8:c140 with SMTP id d9443c01a7336-2962adb9205mr5441665ad.44.1762277215727; Tue, 04 Nov 2025 09:26:55 -0800 (PST) Received: from localhost ([2a03:2880:ff:51::]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-29601a3a80esm33281995ad.73.2025.11.04.09.26.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 04 Nov 2025 09:26:55 -0800 (PST) From: Amery Hung To: bpf@vger.kernel.org Cc: netdev@vger.kernel.org, alexei.starovoitov@gmail.com, andrii@kernel.org, daniel@iogearbox.net, tj@kernel.org, martin.lau@kernel.org, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v5 0/7] Support associating BPF programs with struct_ops Date: Tue, 4 Nov 2025 09:26:45 -0800 Message-ID: <20251104172652.1746988-1-ameryhung@gmail.com> X-Mailer: git-send-email 2.47.3 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit v4 -> v5 - Simplify the API for getting associated struct_ops and dont't expose struct_ops map lifecycle management (Andrii, Alexei) Link: https://lore.kernel.org/bpf/20251024212914.1474337-1-ameryhung@gmail.com/ v3 -> v4 - Fix potential dangling pointer in timer callback. Protect st_ops_assoc with RCU. The get helper now needs to be paired with bpf_struct_ops_put() - The command should only increase refcount once for a program (Andrii) - Test a struct_ops program reused in two struct_ops maps - Test getting associated struct_ops in timer callback Link: https://lore.kernel.org/bpf/20251017215627.722338-1-ameryhung@gmail.com/ v2 -> v3 - Change the type of st_ops_assoc from void* (i.e., kdata) to bpf_map (Andrii) - Fix a bug that clears BPF_PTR_POISON when a struct_ops map is freed (Andrii) - Return NULL if the map is not fully initialized (Martin) - Move struct_ops map refcount inc/dec into internal helpers (Martin) - Add libbpf API, bpf_program__assoc_struct_ops (Andrii) Link: https://lore.kernel.org/bpf/20251016204503.3203690-1-ameryhung@gmail.com/ v1 -> v2 - Poison st_ops_assoc when reusing the program in more than one struct_ops maps and add a helper to access the pointer (Andrii) - Minor style and naming changes (Andrii) Link: https://lore.kernel.org/bpf/20251010174953.2884682-1-ameryhung@gmail.com/ --- Hi, This patchset adds a new BPF command BPF_PROG_ASSOC_STRUCT_OPS to the bpf() syscall to allow associating a BPF program with a struct_ops. The command is introduced to address a emerging need from struct_ops users. As the number of subsystems adopting struct_ops grows, more users are building their struct_ops-based solution with some help from other BPF programs. For exmample, scx_layer uses a syscall program as a user space trigger to refresh layers [0]. It also uses tracing program to infer whether a task is using GPU and needs to be prioritized [1]. In these use cases, when there are multiple struct_ops instances, the struct_ops kfuncs called from different BPF programs, whether struct_ops or not needs to be able to refer to a specific one, which currently is not possible. The new BPF command will allow users to explicitly associate a BPF program with a struct_ops map. The libbpf wrapper can be called after loading programs and before attaching programs and struct_ops. Internally, it will set prog->aux->st_ops_assoc to the struct_ops map. struct_ops kfuncs can then get the associated struct_ops struct by calling bpf_prog_get_assoc_struct_ops() with prog->aux, which can be acquired from a "__prog" argument. The value of the speical argument will be fixed up by the verifier during verification. The command conceptually associates the implementation of BPF programs with struct_ops map, not the attachment. A program associated with the map will take a refcount of it so that st_ops_assoc always points to a valid struct_ops struct. struct_ops implementers can use the helper, bpf_prog_get_assoc_struct_ops to get the pointer. The returned struct_ops if not NULL is guaranteed to be valid and initialized. However, it is not guarantted that the struct_ops is attached. The struct_ops implementer still need to take stepis to track and check the state of the struct_ops in kdata, if the use case demand the struct_ops to be attached. We can also consider support associating struct_ops link with BPF programs, which on one hand make struct_ops implementer's job easier, but might complicate libbpf workflow and does not apply to legacy struct_ops attachment. [0] https://github.com/sched-ext/scx/blob/main/scheds/rust/scx_layered/src/bpf/main.bpf.c#L557 [1] https://github.com/sched-ext/scx/blob/main/scheds/rust/scx_layered/src/bpf/main.bpf.c#L754 --- Amery Hung (7): bpf: Allow verifier to fixup kernel module kfuncs bpf: Support associating BPF program with struct_ops bpf: Pin associated struct_ops when registering async callback libbpf: Add support for associating BPF program with struct_ops selftests/bpf: Test BPF_PROG_ASSOC_STRUCT_OPS command selftests/bpf: Test ambiguous associated struct_ops selftests/bpf: Test getting associated struct_ops in timer callback include/linux/bpf.h | 16 ++ include/uapi/linux/bpf.h | 17 ++ kernel/bpf/bpf_struct_ops.c | 90 ++++++++ kernel/bpf/core.c | 3 + kernel/bpf/helpers.c | 105 +++++++--- kernel/bpf/syscall.c | 46 +++++ kernel/bpf/verifier.c | 3 +- tools/include/uapi/linux/bpf.h | 17 ++ tools/lib/bpf/bpf.c | 19 ++ tools/lib/bpf/bpf.h | 21 ++ tools/lib/bpf/libbpf.c | 30 +++ tools/lib/bpf/libbpf.h | 16 ++ tools/lib/bpf/libbpf.map | 2 + .../bpf/prog_tests/test_struct_ops_assoc.c | 194 ++++++++++++++++++ .../selftests/bpf/progs/struct_ops_assoc.c | 105 ++++++++++ .../bpf/progs/struct_ops_assoc_in_timer.c | 77 +++++++ .../bpf/progs/struct_ops_assoc_reuse.c | 75 +++++++ .../selftests/bpf/test_kmods/bpf_testmod.c | 17 ++ .../bpf/test_kmods/bpf_testmod_kfunc.h | 1 + 19 files changed, 819 insertions(+), 35 deletions(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/test_struct_ops_assoc.c create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_assoc.c create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_assoc_in_timer.c create mode 100644 tools/testing/selftests/bpf/progs/struct_ops_assoc_reuse.c -- 2.47.3