On 9/25/23 16:09, Andrii Nakryiko wrote:
On Wed, Sep 20, 2023 at 9:00 AM <thinker.li@xxxxxxxxx> wrote:From: Kui-Feng Lee <thinker.li@xxxxxxxxx> Find module BTFs for struct_ops maps and progs and pass them to the kernel. It ensures the kernel resolve type IDs from correct module BTFs. For the map of a struct_ops object, mod_btf is added to bpf_map to keep a reference to the module BTF. It's FD is passed to the kernel as mod_btf_fd when it is created. For a prog attaching to a struct_ops object, attach_btf_obj_fd of bpf_prog is the FD pointing to a module BTF in the kernel. Signed-off-by: Kui-Feng Lee <thinker.li@xxxxxxxxx> --- tools/lib/bpf/bpf.c | 3 +- tools/lib/bpf/bpf.h | 4 +- tools/lib/bpf/libbpf.c | 121 ++++++++++++++++++++++++----------------- 3 files changed, 75 insertions(+), 53 deletions(-) diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index b0f1913763a3..df4b7570ad92 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -169,7 +169,7 @@ int bpf_map_create(enum bpf_map_type map_type, __u32 max_entries, const struct bpf_map_create_opts *opts) { - const size_t attr_sz = offsetofend(union bpf_attr, map_extra); + const size_t attr_sz = offsetofend(union bpf_attr, mod_btf_fd); union bpf_attr attr; int fd; @@ -191,6 +191,7 @@ int bpf_map_create(enum bpf_map_type map_type, attr.btf_key_type_id = OPTS_GET(opts, btf_key_type_id, 0); attr.btf_value_type_id = OPTS_GET(opts, btf_value_type_id, 0); attr.btf_vmlinux_value_type_id = OPTS_GET(opts, btf_vmlinux_value_type_id, 0); + attr.mod_btf_fd = OPTS_GET(opts, mod_btf_fd, 0); attr.inner_map_fd = OPTS_GET(opts, inner_map_fd, 0); attr.map_flags = OPTS_GET(opts, map_flags, 0); diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h index 74c2887cfd24..d18f75b0ccc9 100644 --- a/tools/lib/bpf/bpf.h +++ b/tools/lib/bpf/bpf.h @@ -51,8 +51,10 @@ struct bpf_map_create_opts { __u32 numa_node; __u32 map_ifindex; + + __u32 mod_btf_fd;please add `size_t :0;` at the end to avoid compiler leaving garbage in added padding at the end of opts struct
Ok!
}; -#define bpf_map_create_opts__last_field map_ifindex +#define bpf_map_create_opts__last_field mod_btf_fd LIBBPF_API int bpf_map_create(enum bpf_map_type map_type, const char *map_name, diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 3a6108e3238b..df6ba5494adb 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -519,6 +519,7 @@ struct bpf_map { struct bpf_map_def def; __u32 numa_node; __u32 btf_var_idx; + struct module_btf *mod_btf;It would be simpler to just store btf_fd instead of entire struct module_btf pointer. You only need this to set btf_obj_fd on map creation and program loading, right?
Yes!
__u32 btf_key_type_id; __u32 btf_value_type_id; __u32 btf_vmlinux_value_type_id; @@ -893,6 +894,42 @@ bpf_object__add_programs(struct bpf_object *obj, Elf_Data *sec_data, return 0; } +static int load_module_btfs(struct bpf_object *obj); + +static int find_kern_btf_id(struct bpf_object *obj, const char *kern_name, + __u16 kind, struct btf **res_btf, + struct module_btf **res_mod_btf) +{ + struct module_btf *mod_btf; + struct btf *btf; + int i, id, err; + + btf = obj->btf_vmlinux; + mod_btf = NULL; + id = btf__find_by_name_kind(btf, kern_name, kind); + + if (id == -ENOENT) { + err = load_module_btfs(obj); + if (err) + return err; + + for (i = 0; i < obj->btf_module_cnt; i++) { + /* we assume module_btf's BTF FD is always >0 */ + mod_btf = &obj->btf_modules[i]; + btf = mod_btf->btf; + id = btf__find_by_name_kind_own(btf, kern_name, kind); + if (id != -ENOENT) + break; + } + } + if (id <= 0) + return -ESRCH; + + *res_btf = btf; + *res_mod_btf = mod_btf; + return id; +} +there is no need to move the entire function body here, just add a forward declaration. It will also make it easier to see what actually changed about the function (if at all)
Got it
static const struct btf_member * find_member_by_offset(const struct btf_type *t, __u32 bit_offset) { @@ -927,17 +964,23 @@ static int find_btf_by_prefix_kind(const struct btf *btf, const char *prefix, const char *name, __u32 kind); static int -find_struct_ops_kern_types(const struct btf *btf, const char *tname, +find_struct_ops_kern_types(struct bpf_object *obj, const char *tname, + struct module_btf **mod_btf, const struct btf_type **type, __u32 *type_id, const struct btf_type **vtype, __u32 *vtype_id, const struct btf_member **data_member) { const struct btf_type *kern_type, *kern_vtype; const struct btf_member *kern_data_member; + struct btf *btf; __s32 kern_vtype_id, kern_type_id; __u32 i; - kern_type_id = btf__find_by_name_kind(btf, tname, BTF_KIND_STRUCT); + /* XXX: should search module BTFs as well. We need module name here + * to locate a correct BTF type. + */aren't we searching module BTFs? Is this comment still relevant?+ kern_type_id = find_kern_btf_id(obj, tname, BTF_KIND_STRUCT, + &btf, mod_btf); if (kern_type_id < 0) { pr_warn("struct_ops init_kern: struct %s is not found in kernel BTF\n", tname); @@ -992,13 +1035,15 @@ static bool bpf_map__is_struct_ops(const struct bpf_map *map) /* Init the map's fields that depend on kern_btf */ static int bpf_map__init_kern_struct_ops(struct bpf_map *map, - const struct btf *btf, - const struct btf *kern_btf) + struct bpf_object *obj)no need to pass obj separately, you can get it through `map->obj`
Good to know!
{ const struct btf_member *member, *kern_member, *kern_data_member; const struct btf_type *type, *kern_type, *kern_vtype; __u32 i, kern_type_id, kern_vtype_id, kern_data_off; struct bpf_struct_ops *st_ops; + const struct btf *kern_btf; + struct module_btf *mod_btf; + const struct btf *btf = obj->btf; void *data, *kern_data; const char *tname; int err; @@ -1006,16 +1051,19 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map, st_ops = map->st_ops; type = st_ops->type; tname = st_ops->tname; - err = find_struct_ops_kern_types(kern_btf, tname, + err = find_struct_ops_kern_types(obj, tname, &mod_btf, &kern_type, &kern_type_id, &kern_vtype, &kern_vtype_id, &kern_data_member); if (err) return err; + kern_btf = mod_btf ? mod_btf->btf : obj->btf_vmlinux; + pr_debug("struct_ops init_kern %s: type_id:%u kern_type_id:%u kern_vtype_id:%u\n", map->name, st_ops->type_id, kern_type_id, kern_vtype_id); + map->mod_btf = mod_btf; map->def.value_size = kern_vtype->size; map->btf_vmlinux_value_type_id = kern_vtype_id; @@ -1091,6 +1139,9 @@ static int bpf_map__init_kern_struct_ops(struct bpf_map *map, return -ENOTSUP; } + /* XXX: attach_btf_obj_fd is needed as well */seems like all these XXX comments are outdated and the code is already doing all that, is that right? If so, please remove them, they are confusing
Sure!
+ 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; @@ -1133,8 +1184,8 @@ static int bpf_object__init_kern_struct_ops_maps(struct bpf_object *obj) if (!bpf_map__is_struct_ops(map)) continue; - err = bpf_map__init_kern_struct_ops(map, obj->btf, - obj->btf_vmlinux); + /* XXX: should be a module btf if not vmlinux */ + err = bpf_map__init_kern_struct_ops(map, obj); if (err) return err; }[...]
