bpf: Document BPF_F_QUERY_EFFECTIVE flag (f5bfcd95) · Commits · 戴 / test

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 <rdna@fb.com> Signed-off-by:

Alexei Starovoitov <ast@kernel.org> Acked-by:

Song Liu <songliubraving@fb.com> Link: https://lore.kernel.org/bpf/20200108014006.938363-1-rdna@fb.com

include/uapi/linux/bpf.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -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 {

tools/include/uapi/linux/bpf.h

+6 −1

Original line number	Diff line number	Diff line
		@@ -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 {

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