Commit d66562fb authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Alexei Starovoitov

libbpf: Add BPF object skeleton support

Add new set of APIs, allowing to open/load/attach BPF object through BPF
object skeleton, generated by bpftool for a specific BPF object file. All the
xxx_skeleton() APIs wrap up corresponding bpf_object_xxx() APIs, but
additionally also automate map/program lookups by name, global data
initialization and mmap()-ing, etc.  All this greatly improves and simplifies
userspace usability of working with BPF programs. See follow up patches for
examples.
Signed-off-by: default avatarAndrii Nakryiko <andriin@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20191214014341.3442258-13-andriin@fb.com
parent 3f519353
......@@ -6793,3 +6793,165 @@ int libbpf_num_possible_cpus(void)
WRITE_ONCE(cpus, tmp_cpus);
return tmp_cpus;
}
int bpf_object__open_skeleton(struct bpf_object_skeleton *s,
const struct bpf_object_open_opts *opts)
{
DECLARE_LIBBPF_OPTS(bpf_object_open_opts, skel_opts,
.object_name = s->name,
);
struct bpf_object *obj;
int i;
/* Attempt to preserve opts->object_name, unless overriden by user
* explicitly. Overwriting object name for skeletons is discouraged,
* as it breaks global data maps, because they contain object name
* prefix as their own map name prefix. When skeleton is generated,
* bpftool is making an assumption that this name will stay the same.
*/
if (opts) {
memcpy(&skel_opts, opts, sizeof(*opts));
if (!opts->object_name)
skel_opts.object_name = s->name;
}
obj = bpf_object__open_mem(s->data, s->data_sz, &skel_opts);
if (IS_ERR(obj)) {
pr_warn("failed to initialize skeleton BPF object '%s': %ld\n",
s->name, PTR_ERR(obj));
return PTR_ERR(obj);
}
*s->obj = obj;
for (i = 0; i < s->map_cnt; i++) {
struct bpf_map **map = s->maps[i].map;
const char *name = s->maps[i].name;
void **mmaped = s->maps[i].mmaped;
*map = bpf_object__find_map_by_name(obj, name);
if (!*map) {
pr_warn("failed to find skeleton map '%s'\n", name);
return -ESRCH;
}
if (mmaped)
*mmaped = (*map)->mmaped;
}
for (i = 0; i < s->prog_cnt; i++) {
struct bpf_program **prog = s->progs[i].prog;
const char *name = s->progs[i].name;
*prog = bpf_object__find_program_by_name(obj, name);
if (!*prog) {
pr_warn("failed to find skeleton program '%s'\n", name);
return -ESRCH;
}
}
return 0;
}
int bpf_object__load_skeleton(struct bpf_object_skeleton *s)
{
int i, err;
err = bpf_object__load(*s->obj);
if (err) {
pr_warn("failed to load BPF skeleton '%s': %d\n", s->name, err);
return err;
}
for (i = 0; i < s->map_cnt; i++) {
struct bpf_map *map = *s->maps[i].map;
size_t mmap_sz = bpf_map_mmap_sz(map);
int prot, map_fd = bpf_map__fd(map);
void **mmaped = s->maps[i].mmaped;
void *remapped;
if (!mmaped)
continue;
if (!(map->def.map_flags & BPF_F_MMAPABLE)) {
*mmaped = NULL;
continue;
}
if (map->def.map_flags & BPF_F_RDONLY_PROG)
prot = PROT_READ;
else
prot = PROT_READ | PROT_WRITE;
/* Remap anonymous mmap()-ed "map initialization image" as
* a BPF map-backed mmap()-ed memory, but preserving the same
* memory address. This will cause kernel to change process'
* page table to point to a different piece of kernel memory,
* but from userspace point of view memory address (and its
* contents, being identical at this point) will stay the
* same. This mapping will be released by bpf_object__close()
* as per normal clean up procedure, so we don't need to worry
* about it from skeleton's clean up perspective.
*/
remapped = mmap(*mmaped, mmap_sz, prot, MAP_SHARED | MAP_FIXED,
map_fd, 0);
if (remapped == MAP_FAILED) {
err = -errno;
*mmaped = NULL;
pr_warn("failed to re-mmap() map '%s': %d\n",
bpf_map__name(map), err);
return err;
}
}
return 0;
}
int bpf_object__attach_skeleton(struct bpf_object_skeleton *s)
{
int i;
for (i = 0; i < s->prog_cnt; i++) {
struct bpf_program *prog = *s->progs[i].prog;
struct bpf_link **link = s->progs[i].link;
const struct bpf_sec_def *sec_def;
const char *sec_name = bpf_program__title(prog, false);
sec_def = find_sec_def(sec_name);
if (!sec_def || !sec_def->attach_fn)
continue;
*link = sec_def->attach_fn(sec_def, prog);
if (IS_ERR(*link)) {
pr_warn("failed to auto-attach program '%s': %ld\n",
bpf_program__name(prog), PTR_ERR(*link));
return PTR_ERR(*link);
}
}
return 0;
}
void bpf_object__detach_skeleton(struct bpf_object_skeleton *s)
{
int i;
for (i = 0; i < s->prog_cnt; i++) {
struct bpf_link **link = s->progs[i].link;
if (!IS_ERR_OR_NULL(*link))
bpf_link__destroy(*link);
*link = NULL;
}
}
void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s)
{
if (s->progs)
bpf_object__detach_skeleton(s);
if (s->obj)
bpf_object__close(*s->obj);
free(s->maps);
free(s->progs);
free(s);
}
......@@ -631,6 +631,44 @@ BPF_EMBED_OBJ_DECLARE(NAME)
#define BPF_EMBED_OBJ(NAME, PATH) __BPF_EMBED_OBJ(NAME, PATH, 16, ".quad")
#endif
struct bpf_map_skeleton {
const char *name;
struct bpf_map **map;
void **mmaped;
};
struct bpf_prog_skeleton {
const char *name;
struct bpf_program **prog;
struct bpf_link **link;
};
struct bpf_object_skeleton {
size_t sz; /* size of this struct, for forward/backward compatibility */
const char *name;
void *data;
size_t data_sz;
struct bpf_object **obj;
int map_cnt;
int map_skel_sz; /* sizeof(struct bpf_skeleton_map) */
struct bpf_map_skeleton *maps;
int prog_cnt;
int prog_skel_sz; /* sizeof(struct bpf_skeleton_prog) */
struct bpf_prog_skeleton *progs;
};
LIBBPF_API int
bpf_object__open_skeleton(struct bpf_object_skeleton *s,
const struct bpf_object_open_opts *opts);
LIBBPF_API int bpf_object__load_skeleton(struct bpf_object_skeleton *s);
LIBBPF_API int bpf_object__attach_skeleton(struct bpf_object_skeleton *s);
LIBBPF_API void bpf_object__detach_skeleton(struct bpf_object_skeleton *s);
LIBBPF_API void bpf_object__destroy_skeleton(struct bpf_object_skeleton *s);
#ifdef __cplusplus
} /* extern "C" */
#endif
......
......@@ -213,6 +213,11 @@ LIBBPF_0.0.7 {
global:
btf_dump__emit_type_decl;
bpf_object__find_program_by_name;
bpf_object__attach_skeleton;
bpf_object__destroy_skeleton;
bpf_object__detach_skeleton;
bpf_object__load_skeleton;
bpf_object__open_skeleton;
bpf_program__attach;
bpf_program__name;
btf__align_of;
......
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