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libbpf: Support static initialization of BPF_MAP_TYPE_PROG_ARRAY
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Support static initialization of BPF_MAP_TYPE_PROG_ARRAY with a
syntax similar to map-in-map initialization ([0]):

    SEC("socket")
    int tailcall_1(void *ctx)
    {
        return 0;
    }

    struct {
        __uint(type, BPF_MAP_TYPE_PROG_ARRAY);
        __uint(max_entries, 2);
        __uint(key_size, sizeof(__u32));
        __array(values, int (void *));
    } prog_array_init SEC(".maps") = {
        .values = {
            [1] = (void *)&tailcall_1,
        },
    };

Here's the relevant part of libbpf debug log showing what's
going on with prog-array initialization:

libbpf: sec '.relsocket': collecting relocation for section(3) 'socket'
libbpf: sec '.relsocket': relo #0: insn #2 against 'prog_array_init'
libbpf: prog 'entry': found map 0 (prog_array_init, sec 4, off 0) for insn #0
libbpf: .maps relo #0: for 3 value 0 rel->r_offset 32 name 53 ('tailcall_1')
libbpf: .maps relo #0: map 'prog_array_init' slot [1] points to prog 'tailcall_1'
libbpf: map 'prog_array_init': created successfully, fd=5
libbpf: map 'prog_array_init': slot [1] set to prog 'tailcall_1' fd=6

  [0] Closes: #354

Signed-off-by: Hengqi Chen <hengqi.chen@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211128141633.502339-2-hengqi.chen@gmail.com
  • Loading branch information
@chenhengqi @anakryiko
chenhengqi authored and anakryiko committed Nov 29, 2021
1 parent c86cb27 commit 472c072
Showing 1 changed file with 121 additions and 33 deletions.
154 changes: 121 additions & 33 deletions src/libbpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2277,6 +2277,9 @@ int parse_btf_map_def(const char *map_name, struct btf *btf,
map_def->parts |= MAP_DEF_VALUE_SIZE | MAP_DEF_VALUE_TYPE;
}
else if (strcmp(name, "values") == 0) {
bool is_map_in_map = bpf_map_type__is_map_in_map(map_def->map_type);
bool is_prog_array = map_def->map_type == BPF_MAP_TYPE_PROG_ARRAY;
const char *desc = is_map_in_map ? "map-in-map inner" : "prog-array value";
char inner_map_name[128];
int err;

Expand All @@ -2290,8 +2293,8 @@ int parse_btf_map_def(const char *map_name, struct btf *btf,
map_name, name);
return -EINVAL;
}
if (!bpf_map_type__is_map_in_map(map_def->map_type)) {
pr_warn("map '%s': should be map-in-map.\n",
if (!is_map_in_map && !is_prog_array) {
pr_warn("map '%s': should be map-in-map or prog-array.\n",
map_name);
return -ENOTSUP;
}
Expand All @@ -2303,22 +2306,30 @@ int parse_btf_map_def(const char *map_name, struct btf *btf,
map_def->value_size = 4;
t = btf__type_by_id(btf, m->type);
if (!t) {
pr_warn("map '%s': map-in-map inner type [%d] not found.\n",
map_name, m->type);
pr_warn("map '%s': %s type [%d] not found.\n",
map_name, desc, m->type);
return -EINVAL;
}
if (!btf_is_array(t) || btf_array(t)->nelems) {
pr_warn("map '%s': map-in-map inner spec is not a zero-sized array.\n",
map_name);
pr_warn("map '%s': %s spec is not a zero-sized array.\n",
map_name, desc);
return -EINVAL;
}
t = skip_mods_and_typedefs(btf, btf_array(t)->type, NULL);
if (!btf_is_ptr(t)) {
pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",
map_name, btf_kind_str(t));
pr_warn("map '%s': %s def is of unexpected kind %s.\n",
map_name, desc, btf_kind_str(t));
return -EINVAL;
}
t = skip_mods_and_typedefs(btf, t->type, NULL);
if (is_prog_array) {
if (!btf_is_func_proto(t)) {
pr_warn("map '%s': prog-array value def is of unexpected kind %s.\n",
map_name, btf_kind_str(t));
return -EINVAL;
}
continue;
}
if (!btf_is_struct(t)) {
pr_warn("map '%s': map-in-map inner def is of unexpected kind %s.\n",
map_name, btf_kind_str(t));
Expand Down Expand Up @@ -4940,7 +4951,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
return err;
}

static int init_map_slots(struct bpf_object *obj, struct bpf_map *map)
static int init_map_in_map_slots(struct bpf_object *obj, struct bpf_map *map)
{
const struct bpf_map *targ_map;
unsigned int i;
Expand All @@ -4952,6 +4963,7 @@ static int init_map_slots(struct bpf_object *obj, struct bpf_map *map)

targ_map = map->init_slots[i];
fd = bpf_map__fd(targ_map);

if (obj->gen_loader) {
pr_warn("// TODO map_update_elem: idx %td key %d value==map_idx %td\n",
map - obj->maps, i, targ_map - obj->maps);
Expand All @@ -4962,8 +4974,7 @@ static int init_map_slots(struct bpf_object *obj, struct bpf_map *map)
if (err) {
err = -errno;
pr_warn("map '%s': failed to initialize slot [%d] to map '%s' fd=%d: %d\n",
map->name, i, targ_map->name,
fd, err);
map->name, i, targ_map->name, fd, err);
return err;
}
pr_debug("map '%s': slot [%d] set to map '%s' fd=%d\n",
Expand All @@ -4976,6 +4987,59 @@ static int init_map_slots(struct bpf_object *obj, struct bpf_map *map)
return 0;
}

static int init_prog_array_slots(struct bpf_object *obj, struct bpf_map *map)
{
const struct bpf_program *targ_prog;
unsigned int i;
int fd, err;

if (obj->gen_loader)
return -ENOTSUP;

for (i = 0; i < map->init_slots_sz; i++) {
if (!map->init_slots[i])
continue;

targ_prog = map->init_slots[i];
fd = bpf_program__fd(targ_prog);

err = bpf_map_update_elem(map->fd, &i, &fd, 0);
if (err) {
err = -errno;
pr_warn("map '%s': failed to initialize slot [%d] to prog '%s' fd=%d: %d\n",
map->name, i, targ_prog->name, fd, err);
return err;
}
pr_debug("map '%s': slot [%d] set to prog '%s' fd=%d\n",
map->name, i, targ_prog->name, fd);
}

zfree(&map->init_slots);
map->init_slots_sz = 0;

return 0;
}

static int bpf_object_init_prog_arrays(struct bpf_object *obj)
{
struct bpf_map *map;
int i, err;

for (i = 0; i < obj->nr_maps; i++) {
map = &obj->maps[i];

if (!map->init_slots_sz || map->def.type != BPF_MAP_TYPE_PROG_ARRAY)
continue;

err = init_prog_array_slots(obj, map);
if (err < 0) {
zclose(map->fd);
return err;
}
}
return 0;
}

static int
bpf_object__create_maps(struct bpf_object *obj)
{
Expand Down Expand Up @@ -5042,8 +5106,8 @@ bpf_object__create_maps(struct bpf_object *obj)
}
}

if (map->init_slots_sz) {
err = init_map_slots(obj, map);
if (map->init_slots_sz && map->def.type != BPF_MAP_TYPE_PROG_ARRAY) {
err = init_map_in_map_slots(obj, map);
if (err < 0) {
zclose(map->fd);
goto err_out;
Expand Down Expand Up @@ -6189,9 +6253,11 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj,
int i, j, nrels, new_sz;
const struct btf_var_secinfo *vi = NULL;
const struct btf_type *sec, *var, *def;
struct bpf_map *map = NULL, *targ_map;
struct bpf_map *map = NULL, *targ_map = NULL;
struct bpf_program *targ_prog = NULL;
bool is_prog_array, is_map_in_map;
const struct btf_member *member;
const char *name, *mname;
const char *name, *mname, *type;
unsigned int moff;
Elf64_Sym *sym;
Elf64_Rel *rel;
Expand All @@ -6218,11 +6284,6 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj,
return -LIBBPF_ERRNO__FORMAT;
}
name = elf_sym_str(obj, sym->st_name) ?: "<?>";
if (sym->st_shndx != obj->efile.btf_maps_shndx) {
pr_warn(".maps relo #%d: '%s' isn't a BTF-defined map\n",
i, name);
return -LIBBPF_ERRNO__RELOC;
}

pr_debug(".maps relo #%d: for %zd value %zd rel->r_offset %zu name %d ('%s')\n",
i, (ssize_t)(rel->r_info >> 32), (size_t)sym->st_value,
Expand All @@ -6244,19 +6305,45 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj,
return -EINVAL;
}

if (!bpf_map_type__is_map_in_map(map->def.type))
return -EINVAL;
if (map->def.type == BPF_MAP_TYPE_HASH_OF_MAPS &&
map->def.key_size != sizeof(int)) {
pr_warn(".maps relo #%d: hash-of-maps '%s' should have key size %zu.\n",
i, map->name, sizeof(int));
is_map_in_map = bpf_map_type__is_map_in_map(map->def.type);
is_prog_array = map->def.type == BPF_MAP_TYPE_PROG_ARRAY;
type = is_map_in_map ? "map" : "prog";
if (is_map_in_map) {
if (sym->st_shndx != obj->efile.btf_maps_shndx) {
pr_warn(".maps relo #%d: '%s' isn't a BTF-defined map\n",
i, name);
return -LIBBPF_ERRNO__RELOC;
}
if (map->def.type == BPF_MAP_TYPE_HASH_OF_MAPS &&
map->def.key_size != sizeof(int)) {
pr_warn(".maps relo #%d: hash-of-maps '%s' should have key size %zu.\n",
i, map->name, sizeof(int));
return -EINVAL;
}
targ_map = bpf_object__find_map_by_name(obj, name);
if (!targ_map) {
pr_warn(".maps relo #%d: '%s' isn't a valid map reference\n",
i, name);
return -ESRCH;
}
} else if (is_prog_array) {
targ_prog = bpf_object__find_program_by_name(obj, name);
if (!targ_prog) {
pr_warn(".maps relo #%d: '%s' isn't a valid program reference\n",
i, name);
return -ESRCH;
}
if (targ_prog->sec_idx != sym->st_shndx ||
targ_prog->sec_insn_off * 8 != sym->st_value ||
prog_is_subprog(obj, targ_prog)) {
pr_warn(".maps relo #%d: '%s' isn't an entry-point program\n",
i, name);
return -LIBBPF_ERRNO__RELOC;
}
} else {
return -EINVAL;
}

targ_map = bpf_object__find_map_by_name(obj, name);
if (!targ_map)
return -ESRCH;

var = btf__type_by_id(obj->btf, vi->type);
def = skip_mods_and_typedefs(obj->btf, var->type, NULL);
if (btf_vlen(def) == 0)
Expand Down Expand Up @@ -6287,10 +6374,10 @@ static int bpf_object__collect_map_relos(struct bpf_object *obj,
(new_sz - map->init_slots_sz) * host_ptr_sz);
map->init_slots_sz = new_sz;
}
map->init_slots[moff] = targ_map;
map->init_slots[moff] = is_map_in_map ? (void *)targ_map : (void *)targ_prog;

pr_debug(".maps relo #%d: map '%s' slot [%d] points to map '%s'\n",
i, map->name, moff, name);
pr_debug(".maps relo #%d: map '%s' slot [%d] points to %s '%s'\n",
i, map->name, moff, type, name);
}

return 0;
Expand Down Expand Up @@ -7304,6 +7391,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr)
err = err ? : bpf_object__create_maps(obj);
err = err ? : bpf_object__relocate(obj, obj->btf_custom_path ? : attr->target_btf_path);
err = err ? : bpf_object__load_progs(obj, attr->log_level);
err = err ? : bpf_object_init_prog_arrays(obj);

if (obj->gen_loader) {
/* reset FDs */
Expand Down

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