From f5bfcd953d811dbb8913de36b96b38da6bb62135 Mon Sep 17 00:00:00 2001 From: Andrey Ignatov Date: Tue, 7 Jan 2020 17:40:06 -0800 Subject: [PATCH] bpf: Document BPF_F_QUERY_EFFECTIVE flag Document BPF_F_QUERY_EFFECTIVE flag, mostly to clarify how it affects attach_flags what may not be obvious and what may lead to confision. Specifically attach_flags is returned only for target_fd but if programs are inherited from an ancestor cgroup then returned attach_flags for current cgroup may be confusing. For example, two effective programs of same attach_type can be returned but w/o BPF_F_ALLOW_MULTI in attach_flags. Simple repro: # bpftool c s /sys/fs/cgroup/path/to/task ID AttachType AttachFlags Name # bpftool c s /sys/fs/cgroup/path/to/task effective ID AttachType AttachFlags Name 95043 ingress tw_ipt_ingress 95048 ingress tw_ingress Signed-off-by: Andrey Ignatov Signed-off-by: Alexei Starovoitov Acked-by: Song Liu Link: https://lore.kernel.org/bpf/20200108014006.938363-1-rdna@fb.com --- include/uapi/linux/bpf.h | 7 ++++++- tools/include/uapi/linux/bpf.h | 7 ++++++- 2 files changed, 12 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 2d6a2e572f56..52966e758fe5 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -359,7 +359,12 @@ enum bpf_attach_type { /* Enable memory-mapping BPF map */ #define BPF_F_MMAPABLE (1U << 10) -/* flags for BPF_PROG_QUERY */ +/* Flags for BPF_PROG_QUERY. */ + +/* Query effective (directly attached + inherited from ancestor cgroups) + * programs that will be executed for events within a cgroup. + * attach_flags with this flag are returned only for directly attached programs. + */ #define BPF_F_QUERY_EFFECTIVE (1U << 0) enum bpf_stack_build_id_status { diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index 2d6a2e572f56..52966e758fe5 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -359,7 +359,12 @@ enum bpf_attach_type { /* Enable memory-mapping BPF map */ #define BPF_F_MMAPABLE (1U << 10) -/* flags for BPF_PROG_QUERY */ +/* Flags for BPF_PROG_QUERY. */ + +/* Query effective (directly attached + inherited from ancestor cgroups) + * programs that will be executed for events within a cgroup. + * attach_flags with this flag are returned only for directly attached programs. + */ #define BPF_F_QUERY_EFFECTIVE (1U << 0) enum bpf_stack_build_id_status { -- 2.20.1