From 1209339844601ec1766f4ff430673fbcfe42bb51 Mon Sep 17 00:00:00 2001 From: Yonghong Song Date: Fri, 6 Jun 2025 09:31:41 -0700 Subject: bpf: Implement mprog API on top of existing cgroup progs Current cgroup prog ordering is appending at attachment time. This is not ideal. In some cases, users want specific ordering at a particular cgroup level. To address this, the existing mprog API seems an ideal solution with supporting BPF_F_BEFORE and BPF_F_AFTER flags. But there are a few obstacles to directly use kernel mprog interface. Currently cgroup bpf progs already support prog attach/detach/replace and link-based attach/detach/replace. For example, in struct bpf_prog_array_item, the cgroup_storage field needs to be together with bpf prog. But the mprog API struct bpf_mprog_fp only has bpf_prog as the member, which makes it difficult to use kernel mprog interface. In another case, the current cgroup prog detach tries to use the same flag as in attach. This is different from mprog kernel interface which uses flags passed from user space. So to avoid modifying existing behavior, I made the following changes to support mprog API for cgroup progs: - The support is for prog list at cgroup level. Cross-level prog list (a.k.a. effective prog list) is not supported. - Previously, BPF_F_PREORDER is supported only for prog attach, now BPF_F_PREORDER is also supported by link-based attach. - For attach, BPF_F_BEFORE/BPF_F_AFTER/BPF_F_ID/BPF_F_LINK is supported similar to kernel mprog but with different implementation. - For detach and replace, use the existing implementation. - For attach, detach and replace, the revision for a particular prog list, associated with a particular attach type, will be updated by increasing count by 1. Signed-off-by: Yonghong Song Signed-off-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20250606163141.2428937-1-yonghong.song@linux.dev --- tools/include/uapi/linux/bpf.h | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'tools/include') diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index f1160ebbf526..25e9cf92ffaf 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -1794,6 +1794,13 @@ union bpf_attr { }; __u64 expected_revision; } netkit; + struct { + union { + __u32 relative_fd; + __u32 relative_id; + }; + __u64 expected_revision; + } cgroup; }; } link_create; -- cgit v1.2.3