From d9ab2f76ef5abb76190ffb42d83bdc6caede807e Mon Sep 17 00:00:00 2001 From: Eduard Zingerman Date: Wed, 6 Mar 2024 12:45:16 +0200 Subject: [PATCH] libbpf: Tie struct_ops programs to kernel BTF ids, not to local ids Enforce the following existing limitation on struct_ops programs based on kernel BTF id instead of program-local BTF id: struct_ops BPF prog can be re-used between multiple .struct_ops & .struct_ops.link as long as it's the same struct_ops struct definition and the same function pointer field This allows reusing same BPF program for versioned struct_ops map definitions, e.g.: SEC("struct_ops/test") int BPF_PROG(foo) { ... } struct some_ops___v1 { int (*test)(void); }; struct some_ops___v2 { int (*test)(void); }; SEC(".struct_ops.link") struct some_ops___v1 a = { .test = foo } SEC(".struct_ops.link") struct some_ops___v2 b = { .test = foo } Signed-off-by: Eduard Zingerman Signed-off-by: Andrii Nakryiko Acked-by: Andrii Nakryiko Link: https://lore.kernel.org/bpf/20240306104529.6453-3-eddyz87@gmail.com --- tools/lib/bpf/libbpf.c | 49 ++++++++++++++++++++++-------------------- 1 file changed, 26 insertions(+), 23 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index e2a4c409980b..2c0cb72bc7a4 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -1146,8 +1146,32 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map) if (mod_btf) prog->attach_btf_obj_fd = mod_btf->fd; - prog->attach_btf_id = kern_type_id; - prog->expected_attach_type = kern_member_idx; + + /* if we haven't yet processed this BPF program, record proper + * attach_btf_id and member_idx + */ + if (!prog->attach_btf_id) { + prog->attach_btf_id = kern_type_id; + prog->expected_attach_type = kern_member_idx; + } + + /* struct_ops BPF prog can be re-used between multiple + * .struct_ops & .struct_ops.link as long as it's the + * same struct_ops struct definition and the same + * function pointer field + */ + if (prog->attach_btf_id != kern_type_id) { + pr_warn("struct_ops init_kern %s func ptr %s: invalid reuse of prog %s in sec %s with type %u: attach_btf_id %u != kern_type_id %u\n", + map->name, mname, prog->name, prog->sec_name, prog->type, + prog->attach_btf_id, kern_type_id); + return -EINVAL; + } + if (prog->expected_attach_type != kern_member_idx) { + pr_warn("struct_ops init_kern %s func ptr %s: invalid reuse of prog %s in sec %s with type %u: expected_attach_type %u != kern_member_idx %u\n", + map->name, mname, prog->name, prog->sec_name, prog->type, + prog->expected_attach_type, kern_member_idx); + return -EINVAL; + } st_ops->kern_func_off[i] = kern_data_off + kern_moff; @@ -9428,27 +9452,6 @@ static int bpf_object__collect_st_ops_relos(struct bpf_object *obj, return -EINVAL; } - /* if we haven't yet processed this BPF program, record proper - * attach_btf_id and member_idx - */ - if (!prog->attach_btf_id) { - prog->attach_btf_id = st_ops->type_id; - prog->expected_attach_type = member_idx; - } - - /* struct_ops BPF prog can be re-used between multiple - * .struct_ops & .struct_ops.link as long as it's the - * same struct_ops struct definition and the same - * function pointer field - */ - if (prog->attach_btf_id != st_ops->type_id || - prog->expected_attach_type != member_idx) { - pr_warn("struct_ops reloc %s: cannot use prog %s in sec %s with type %u attach_btf_id %u expected_attach_type %u for func ptr %s\n", - map->name, prog->name, prog->sec_name, prog->type, - prog->attach_btf_id, prog->expected_attach_type, name); - return -EINVAL; - } - st_ops->progs[member_idx] = prog; /* st_ops->data will be exposed to users, being returned by