From: Martin KaFai Lau kafai@fb.com
[ Upstream commit d2836dddc95d5dd82c7cb23726c97d8c9147f050 ]
When libbpf initializes the kernel's struct_ops in "bpf_map__init_kern_struct_ops()", it enforces all pointer types must be a function pointer and rejects others. It turns out to be too strict. For example, when directly using "struct tcp_congestion_ops" from vmlinux.h, it has a "struct module *owner" member and it is set to NULL in a bpf_tcp_cc.o.
Instead, it only needs to ensure the member is a function pointer if it has been set (relocated) to a bpf-prog. This patch moves the "btf_is_func_proto(kern_mtype)" check after the existing "if (!prog) { continue; }". The original debug message in "if (!prog) { continue; }" is also removed since it is no longer valid. Beside, there is a later debug message to tell which function pointer is set.
The "btf_is_func_proto(mtype)" has already been guaranteed in "bpf_object__collect_st_ops_relos()" which has been run before "bpf_map__init_kern_struct_ops()". Thus, this check is removed.
v2: - Remove outdated debug message (Andrii) Remove because there is a later debug message to tell which function pointer is set. - Following mtype->type is no longer needed. Remove: "skip_mods_and_typedefs(btf, mtype->type, &mtype_id)" - Do "if (!prog)" test before skip_mods_and_typedefs.
Fixes: 590a00888250 ("bpf: libbpf: Add STRUCT_OPS support") Signed-off-by: Martin KaFai Lau kafai@fb.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Acked-by: Andrii Nakryiko andrii@kernel.org Link: https://lore.kernel.org/bpf/20210212021030.266932-1-kafai@fb.com Signed-off-by: Sasha Levin sashal@kernel.org --- tools/lib/bpf/libbpf.c | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index ad165e6e74bc0..b954db52bb807 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -865,24 +865,24 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map, if (btf_is_ptr(mtype)) { struct bpf_program *prog;
- mtype = skip_mods_and_typedefs(btf, mtype->type, &mtype_id); + prog = st_ops->progs[i]; + if (!prog) + continue; + kern_mtype = skip_mods_and_typedefs(kern_btf, kern_mtype->type, &kern_mtype_id); - if (!btf_is_func_proto(mtype) || - !btf_is_func_proto(kern_mtype)) { - pr_warn("struct_ops init_kern %s: non func ptr %s is not supported\n", + + /* mtype->type must be a func_proto which was + * guaranteed in bpf_object__collect_st_ops_relos(), + * so only check kern_mtype for func_proto here. + */ + if (!btf_is_func_proto(kern_mtype)) { + pr_warn("struct_ops init_kern %s: kernel member %s is not a func ptr\n", map->name, mname); return -ENOTSUP; }
- prog = st_ops->progs[i]; - if (!prog) { - pr_debug("struct_ops init_kern %s: func ptr %s is not set\n", - map->name, mname); - continue; - } - prog->attach_btf_id = kern_type_id; prog->expected_attach_type = kern_member_idx;