bpf: Add bpf_struct_ops_for_each_prog()

Add a helper that walks the member progs of the struct_ops map
containing a given @kdata vmtable. struct_ops ->reg() callbacks (and
similar) sometimes need to inspect the loaded BPF programs, e.g. to
discover maps they reference via prog->aux->used_maps.

The implementation mirrors bpf_struct_ops_id(): container_of @kdata
to recover the bpf_struct_ops_map, then iterate st_map->links[i]->prog
for i in [0, funcs_cnt). Same access pattern, no new locking - by the
time ->reg() fires st_map is fully populated and stable.

A sched_ext follow-up walks the member progs of a cid-form scheduler's
struct_ops map, reads prog->aux->arena directly, and requires all member
progs to reference exactly one arena, without requiring the BPF program
to call a registration kfunc.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260522172219.1423324-5-tj@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c00be24e7244..491cc6750504 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2131,6 +2131,9 @@ int bpf_prog_assoc_struct_ops(struct bpf_prog *prog, struct bpf_map *map);
 void bpf_prog_disassoc_struct_ops(struct bpf_prog *prog);
 void *bpf_prog_get_assoc_struct_ops(const struct bpf_prog_aux *aux);
 u32 bpf_struct_ops_id(const void *kdata);
+int bpf_struct_ops_for_each_prog(const void *kdata,
+				 int (*cb)(struct bpf_prog *prog, void *data),
+				 void *data);
 
 #ifdef CONFIG_NET
 /* Define it here to avoid the use of forward declaration */