On 3/7/23 16:46, Andrii Nakryiko wrote:
On Tue, Mar 7, 2023 at 3:33 PM Kui-Feng Lee <kuifeng@xxxxxxxx> wrote:bpf_map__attach_struct_ops() was creating a dummy bpf_link as a placeholder, but now it is constructing an authentic one by calling bpf_link_create() if the map has the BPF_F_LINK flag. You can flag a struct_ops map with BPF_F_LINK by calling bpf_map__set_map_flags(). Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx> --- tools/lib/bpf/libbpf.c | 84 +++++++++++++++++++++++++++++++----------- 1 file changed, 62 insertions(+), 22 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 35a698eb825d..a67efc3b3763 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -115,6 +115,7 @@ static const char * const attach_type_name[] = { [BPF_SK_REUSEPORT_SELECT_OR_MIGRATE] = "sk_reuseport_select_or_migrate", [BPF_PERF_EVENT] = "perf_event", [BPF_TRACE_KPROBE_MULTI] = "trace_kprobe_multi", + [BPF_STRUCT_OPS] = "struct_ops", }; static const char * const link_type_name[] = { @@ -7677,6 +7678,26 @@ static int bpf_object__resolve_externs(struct bpf_object *obj, return 0; } +static void bpf_map_prepare_vdata(const struct bpf_map *map) +{ + struct bpf_struct_ops *st_ops; + __u32 i; + + st_ops = map->st_ops; + for (i = 0; i < btf_vlen(st_ops->type); i++) { + struct bpf_program *prog = st_ops->progs[i]; + void *kern_data; + int prog_fd; + + if (!prog) + continue; + + prog_fd = bpf_program__fd(prog); + kern_data = st_ops->kern_vdata + st_ops->kern_func_off[i]; + *(unsigned long *)kern_data = prog_fd; + } +} + static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const char *target_btf_path) { int err, i; @@ -7728,6 +7749,10 @@ static int bpf_object_load(struct bpf_object *obj, int extra_log_level, const ch btf__free(obj->btf_vmlinux); obj->btf_vmlinux = NULL; + for (i = 0; i < obj->nr_maps; i++) + if (bpf_map__is_struct_ops(&obj->maps[i])) + bpf_map_prepare_vdata(&obj->maps[i]);This is similar in spirit to what bpf_object_init_prog_arrays() is doing, let's add this as a separate step. How about bpf_object_prepare_struct_ops()?
Good!
+ obj->loaded = true; /* doesn't matter if successfully or not */ if (err) @@ -11429,22 +11454,34 @@ struct bpf_link *bpf_program__attach(const struct bpf_program *prog) return link; } +struct bpf_link_struct_ops { + struct bpf_link link; + int map_fd; +}; + static int bpf_link__detach_struct_ops(struct bpf_link *link) { + struct bpf_link_struct_ops *st_link; __u32 zero = 0; - if (bpf_map_delete_elem(link->fd, &zero)) - return -errno; + st_link = container_of(link, struct bpf_link_struct_ops, link); - return 0; + if (st_link->map_fd < 0) { + /* Fake bpf_link */ + if (bpf_map_delete_elem(link->fd, &zero)) + return -errno; + return 0;just `return bpf_map_delete_elem(...)`, it will return actual error (libbpf 1.0 simplification)
Got it!
+ } + + /* Doesn't support detaching. */ + return -EOPNOTSUPP; } struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map) { - struct bpf_struct_ops *st_ops; - struct bpf_link *link; - __u32 i, zero = 0; - int err; + struct bpf_link_struct_ops *link; + __u32 zero = 0; + int err, fd; if (!bpf_map__is_struct_ops(map) || map->fd == -1) return libbpf_err_ptr(-EINVAL); @@ -11453,31 +11490,34 @@ struct bpf_link *bpf_map__attach_struct_ops(const struct bpf_map *map) if (!link) return libbpf_err_ptr(-EINVAL); - st_ops = map->st_ops; - for (i = 0; i < btf_vlen(st_ops->type); i++) { - struct bpf_program *prog = st_ops->progs[i]; - void *kern_data; - int prog_fd; + /* kern_vdata should be prepared during the loading phase. */ + err = bpf_map_update_elem(map->fd, &zero, map->st_ops->kern_vdata, 0); + if (err) { + err = -errno;no need to deal with -errno, err is already the error you need
ok!
+ free(link); + return libbpf_err_ptr(err); + } - if (!prog) - continue; - prog_fd = bpf_program__fd(prog); - kern_data = st_ops->kern_vdata + st_ops->kern_func_off[i]; - *(unsigned long *)kern_data = prog_fd; + if (!(map->def.map_flags & BPF_F_LINK)) { + /* Fake bpf_link */ + link->link.fd = map->fd; + link->map_fd = -1; + link->link.detach = bpf_link__detach_struct_ops; + return &link->link; } - err = bpf_map_update_elem(map->fd, &zero, st_ops->kern_vdata, 0); - if (err) { + fd = bpf_link_create(map->fd, -1, BPF_STRUCT_OPS, NULL); + if (fd < 0) { err = -errno;same, fd is an error, it's true for all low-level libbpf APIs
Good to know!
free(link); return libbpf_err_ptr(err); } - link->detach = bpf_link__detach_struct_ops; - link->fd = map->fd; + link->link.fd = fd; + link->map_fd = map->fd; - return link; + return &link->link; } typedef enum bpf_perf_event_ret (*bpf_perf_event_print_t)(struct perf_event_header *hdr, -- 2.34.1
