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Message-ID: <0ae37c13-e8d9-b0ca-00ca-1750dc2799c9@fb.com>
Date: Thu, 22 Apr 2021 08:33:15 -0700
From: Yonghong Song <yhs@...com>
To: Andrii Nakryiko <andrii@...nel.org>, <bpf@...r.kernel.org>,
<netdev@...r.kernel.org>, <ast@...com>, <daniel@...earbox.net>
CC: <kernel-team@...com>
Subject: Re: [PATCH v2 bpf-next 06/17] libbpf: refactor BTF map definition
parsing
On 4/16/21 1:23 PM, Andrii Nakryiko wrote:
> Refactor BTF-defined maps parsing logic to allow it to be nicely reused by BPF
> static linker. Further, at least for BPF static linker, it's important to know
> which attributes of a BPF map were defined explicitly, so provide a bit set
> for each known portion of BTF map definition. This allows BPF static linker to
> do a simple check when dealing with extern map declarations.
>
> The same capabilities allow to distinguish attributes explicitly set to zero
> (e.g., __uint(max_entries, 0)) vs the case of not specifying it at all (no
> max_entries attribute at all). Libbpf is currently not utilizing that, but it
> could be useful for backwards compatibility reasons later.
>
> Signed-off-by: Andrii Nakryiko <andrii@...nel.org>
> ---
> tools/lib/bpf/libbpf.c | 256 ++++++++++++++++++--------------
> tools/lib/bpf/libbpf_internal.h | 32 ++++
> 2 files changed, 177 insertions(+), 111 deletions(-)
>
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index a0e6d6bc47f3..f6f4126389ac 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -2025,255 +2025,262 @@ static int build_map_pin_path(struct bpf_map *map, const char *path)
> return bpf_map__set_pin_path(map, buf);
> }
>
> -
> -static int parse_btf_map_def(struct bpf_object *obj,
> - struct bpf_map *map,
> - const struct btf_type *def,
> - bool strict, bool is_inner,
> - const char *pin_root_path)
> +int parse_btf_map_def(const char *map_name, struct btf *btf,
> + const struct btf_type *def_t, bool strict,
> + struct btf_map_def *map_def, struct btf_map_def *inner_def)
> {
> const struct btf_type *t;
> const struct btf_member *m;
> + bool is_inner = inner_def == NULL;
> int vlen, i;
>
> - vlen = btf_vlen(def);
> - m = btf_members(def);
> + vlen = btf_vlen(def_t);
> + m = btf_members(def_t);
> for (i = 0; i < vlen; i++, m++) {
> - const char *name = btf__name_by_offset(obj->btf, m->name_off);
> + const char *name = btf__name_by_offset(btf, m->name_off);
>
[...]
> }
> else if (strcmp(name, "values") == 0) {
> + char inner_map_name[128];
> int err;
>
> if (is_inner) {
> pr_warn("map '%s': multi-level inner maps not supported.\n",
> - map->name);
> + map_name);
> return -ENOTSUP;
> }
> if (i != vlen - 1) {
> pr_warn("map '%s': '%s' member should be last.\n",
> - map->name, name);
> + map_name, name);
> return -EINVAL;
> }
> - if (!bpf_map_type__is_map_in_map(map->def.type)) {
> + if (!bpf_map_type__is_map_in_map(map_def->map_type)) {
> pr_warn("map '%s': should be map-in-map.\n",
> - map->name);
> + map_name);
> return -ENOTSUP;
> }
> - if (map->def.value_size && map->def.value_size != 4) {
> + if (map_def->value_size && map_def->value_size != 4) {
> pr_warn("map '%s': conflicting value size %u != 4.\n",
> - map->name, map->def.value_size);
> + map_name, map_def->value_size);
> return -EINVAL;
> }
> - map->def.value_size = 4;
> - t = btf__type_by_id(obj->btf, m->type);
> + 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);
> + map_name, 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);
> + map_name);
> return -EINVAL;
> }
> - t = skip_mods_and_typedefs(obj->btf, btf_array(t)->type,
> - NULL);
> + 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));
> + map_name, btf_kind_str(t));
> return -EINVAL;
> }
> - t = skip_mods_and_typedefs(obj->btf, t->type, NULL);
> + t = skip_mods_and_typedefs(btf, t->type, NULL);
> 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));
> + map_name, btf_kind_str(t));
> return -EINVAL;
> }
>
> - map->inner_map = calloc(1, sizeof(*map->inner_map));
> - if (!map->inner_map)
> - return -ENOMEM;
> - map->inner_map->fd = -1;
> - map->inner_map->sec_idx = obj->efile.btf_maps_shndx;
The refactoring didn't set map->inner_map->sec_idx. I guess since
inner_map is only used internally by libbpf, so it does not
have a user visible sec_idx and hence useless? It is worthwhile to
mention in the commit message for this difference, I think.
> - map->inner_map->name = malloc(strlen(map->name) +
> - sizeof(".inner") + 1);
> - if (!map->inner_map->name)
> - return -ENOMEM;
> - sprintf(map->inner_map->name, "%s.inner", map->name);
> -
> - err = parse_btf_map_def(obj, map->inner_map, t, strict,
> - true /* is_inner */, NULL);
> + snprintf(inner_map_name, sizeof(inner_map_name), "%s.inner", map_name);
> + err = parse_btf_map_def(inner_map_name, btf, t, strict, inner_def, NULL);
> if (err)
> return err;
> +
> + map_def->parts |= MAP_DEF_INNER_MAP;
> } else if (strcmp(name, "pinning") == 0) {
> __u32 val;
> - int err;
>
> if (is_inner) {
> - pr_debug("map '%s': inner def can't be pinned.\n",
> - map->name);
> + pr_warn("map '%s': inner def can't be pinned.\n", map_name);
> return -EINVAL;
> }
> - if (!get_map_field_int(map->name, obj->btf, m, &val))
> + if (!get_map_field_int(map_name, btf, m, &val))
> return -EINVAL;
> - pr_debug("map '%s': found pinning = %u.\n",
> - map->name, val);
> -
> - if (val != LIBBPF_PIN_NONE &&
> - val != LIBBPF_PIN_BY_NAME) {
> + if (val != LIBBPF_PIN_NONE && val != LIBBPF_PIN_BY_NAME) {
> pr_warn("map '%s': invalid pinning value %u.\n",
> - map->name, val);
> + map_name, val);
> return -EINVAL;
> }
> - if (val == LIBBPF_PIN_BY_NAME) {
> - err = build_map_pin_path(map, pin_root_path);
> - if (err) {
> - pr_warn("map '%s': couldn't build pin path.\n",
> - map->name);
> - return err;
> - }
> - }
> + map_def->pinning = val;
> + map_def->parts |= MAP_DEF_PINNING;
> } else {
> if (strict) {
> - pr_warn("map '%s': unknown field '%s'.\n",
> - map->name, name);
> + pr_warn("map '%s': unknown field '%s'.\n", map_name, name);
> return -ENOTSUP;
> }
> - pr_debug("map '%s': ignoring unknown field '%s'.\n",
> - map->name, name);
> + pr_debug("map '%s': ignoring unknown field '%s'.\n", map_name, name);
> }
> }
>
> - if (map->def.type == BPF_MAP_TYPE_UNSPEC) {
> - pr_warn("map '%s': map type isn't specified.\n", map->name);
> + if (map_def->map_type == BPF_MAP_TYPE_UNSPEC) {
> + pr_warn("map '%s': map type isn't specified.\n", map_name);
> return -EINVAL;
> }
>
> return 0;
> }
>
> +static void fill_map_from_def(struct bpf_map *map, const struct btf_map_def *def)
> +{
[...]
> +}
> +
> static int bpf_object__init_user_btf_map(struct bpf_object *obj,
> const struct btf_type *sec,
> int var_idx, int sec_idx,
> const Elf_Data *data, bool strict,
> const char *pin_root_path)
> {
> + struct btf_map_def map_def = {}, inner_def = {};
> const struct btf_type *var, *def;
> const struct btf_var_secinfo *vi;
> const struct btf_var *var_extra;
> const char *map_name;
> struct bpf_map *map;
> + int err;
>
> vi = btf_var_secinfos(sec) + var_idx;
> var = btf__type_by_id(obj->btf, vi->type);
> @@ -2327,7 +2334,34 @@ static int bpf_object__init_user_btf_map(struct bpf_object *obj,
> pr_debug("map '%s': at sec_idx %d, offset %zu.\n",
> map_name, map->sec_idx, map->sec_offset);
>
> - return parse_btf_map_def(obj, map, def, strict, false, pin_root_path);
> + err = parse_btf_map_def(map->name, obj->btf, def, strict, &map_def, &inner_def);
> + if (err)
> + return err;
> +
> + fill_map_from_def(map, &map_def);
> +
> + if (map_def.pinning == LIBBPF_PIN_BY_NAME) {
> + err = build_map_pin_path(map, pin_root_path);
> + if (err) {
> + pr_warn("map '%s': couldn't build pin path.\n", map->name);
> + return err;
> + }
> + }
> +
> + if (map_def.parts & MAP_DEF_INNER_MAP) {
> + map->inner_map = calloc(1, sizeof(*map->inner_map));
> + if (!map->inner_map)
> + return -ENOMEM;
> + map->inner_map->fd = -1;
missing set map->inner_map->sec_idx here.
> + map->inner_map->name = malloc(strlen(map_name) + sizeof(".inner") + 1);
> + if (!map->inner_map->name)
> + return -ENOMEM;
> + sprintf(map->inner_map->name, "%s.inner", map_name);
> +
> + fill_map_from_def(map->inner_map, &inner_def);
> + }
> +
> + return 0;
> }
>
> static int bpf_object__init_user_btf_maps(struct bpf_object *obj, bool strict,
> diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h
> index 92b7eae10c6d..17883073710c 100644
> --- a/tools/lib/bpf/libbpf_internal.h
> +++ b/tools/lib/bpf/libbpf_internal.h
> @@ -138,6 +138,38 @@ static inline __u32 btf_type_info(int kind, int vlen, int kflag)
> return (kflag << 31) | (kind << 24) | vlen;
> }
>
[...]
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