diff options
| -rw-r--r-- | tools/lib/bpf/btf.c | 319 | ||||
| -rw-r--r-- | tools/lib/bpf/btf.h | 21 | ||||
| -rw-r--r-- | tools/lib/bpf/libbpf.map | 1 |
3 files changed, 335 insertions, 6 deletions
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 775ca55a541c..407ed92b4134 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c @@ -1770,9 +1770,8 @@ static int btf_rewrite_str(struct btf_pipe *p, __u32 *str_off) return 0; } -int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_type *src_type) +static int btf_add_type(struct btf_pipe *p, const struct btf_type *src_type) { - struct btf_pipe p = { .src = src_btf, .dst = btf }; struct btf_field_iter it; struct btf_type *t; __u32 *str_off; @@ -1783,10 +1782,10 @@ int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_t return libbpf_err(sz); /* deconstruct BTF, if necessary, and invalidate raw_data */ - if (btf_ensure_modifiable(btf)) + if (btf_ensure_modifiable(p->dst)) return libbpf_err(-ENOMEM); - t = btf_add_type_mem(btf, sz); + t = btf_add_type_mem(p->dst, sz); if (!t) return libbpf_err(-ENOMEM); @@ -1797,12 +1796,19 @@ int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_t return libbpf_err(err); while ((str_off = btf_field_iter_next(&it))) { - err = btf_rewrite_str(&p, str_off); + err = btf_rewrite_str(p, str_off); if (err) return libbpf_err(err); } - return btf_commit_type(btf, sz); + return btf_commit_type(p->dst, sz); +} + +int btf__add_type(struct btf *btf, const struct btf *src_btf, const struct btf_type *src_type) +{ + struct btf_pipe p = { .src = src_btf, .dst = btf }; + + return btf_add_type(&p, src_type); } static size_t btf_dedup_identity_hash_fn(long key, void *ctx); @@ -5276,3 +5282,304 @@ int btf_ext_visit_str_offs(struct btf_ext *btf_ext, str_off_visit_fn visit, void return 0; } + +struct btf_distill { + struct btf_pipe pipe; + int *id_map; + unsigned int split_start_id; + unsigned int split_start_str; + int diff_id; +}; + +static int btf_add_distilled_type_ids(struct btf_distill *dist, __u32 i) +{ + struct btf_type *split_t = btf_type_by_id(dist->pipe.src, i); + struct btf_field_iter it; + __u32 *id; + int err; + + err = btf_field_iter_init(&it, split_t, BTF_FIELD_ITER_IDS); + if (err) + return err; + while ((id = btf_field_iter_next(&it))) { + struct btf_type *base_t; + + if (!*id) + continue; + /* split BTF id, not needed */ + if (*id >= dist->split_start_id) + continue; + /* already added ? */ + if (dist->id_map[*id] > 0) + continue; + + /* only a subset of base BTF types should be referenced from + * split BTF; ensure nothing unexpected is referenced. + */ + base_t = btf_type_by_id(dist->pipe.src, *id); + switch (btf_kind(base_t)) { + case BTF_KIND_INT: + case BTF_KIND_FLOAT: + case BTF_KIND_FWD: + case BTF_KIND_ARRAY: + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + case BTF_KIND_TYPEDEF: + case BTF_KIND_ENUM: + case BTF_KIND_ENUM64: + case BTF_KIND_PTR: + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + case BTF_KIND_VOLATILE: + case BTF_KIND_FUNC_PROTO: + case BTF_KIND_TYPE_TAG: + dist->id_map[*id] = *id; + break; + default: + pr_warn("unexpected reference to base type[%u] of kind [%u] when creating distilled base BTF.\n", + *id, btf_kind(base_t)); + return -EINVAL; + } + /* If a base type is used, ensure types it refers to are + * marked as used also; so for example if we find a PTR to INT + * we need both the PTR and INT. + * + * The only exception is named struct/unions, since distilled + * base BTF composite types have no members. + */ + if (btf_is_composite(base_t) && base_t->name_off) + continue; + err = btf_add_distilled_type_ids(dist, *id); + if (err) + return err; + } + return 0; +} + +static int btf_add_distilled_types(struct btf_distill *dist) +{ + bool adding_to_base = dist->pipe.dst->start_id == 1; + int id = btf__type_cnt(dist->pipe.dst); + struct btf_type *t; + int i, err = 0; + + + /* Add types for each of the required references to either distilled + * base or split BTF, depending on type characteristics. + */ + for (i = 1; i < dist->split_start_id; i++) { + const char *name; + int kind; + + if (!dist->id_map[i]) + continue; + t = btf_type_by_id(dist->pipe.src, i); + kind = btf_kind(t); + name = btf__name_by_offset(dist->pipe.src, t->name_off); + + switch (kind) { + case BTF_KIND_INT: + case BTF_KIND_FLOAT: + case BTF_KIND_FWD: + /* Named int, float, fwd are added to base. */ + if (!adding_to_base) + continue; + err = btf_add_type(&dist->pipe, t); + break; + case BTF_KIND_STRUCT: + case BTF_KIND_UNION: + /* Named struct/union are added to base as 0-vlen + * struct/union of same size. Anonymous struct/unions + * are added to split BTF as-is. + */ + if (adding_to_base) { + if (!t->name_off) + continue; + err = btf_add_composite(dist->pipe.dst, kind, name, t->size); + } else { + if (t->name_off) + continue; + err = btf_add_type(&dist->pipe, t); + } + break; + case BTF_KIND_ENUM: + case BTF_KIND_ENUM64: + /* Named enum[64]s are added to base as a sized + * enum; relocation will match with appropriately-named + * and sized enum or enum64. + * + * Anonymous enums are added to split BTF as-is. + */ + if (adding_to_base) { + if (!t->name_off) + continue; + err = btf__add_enum(dist->pipe.dst, name, t->size); + } else { + if (t->name_off) + continue; + err = btf_add_type(&dist->pipe, t); + } + break; + case BTF_KIND_ARRAY: + case BTF_KIND_TYPEDEF: + case BTF_KIND_PTR: + case BTF_KIND_CONST: + case BTF_KIND_RESTRICT: + case BTF_KIND_VOLATILE: + case BTF_KIND_FUNC_PROTO: + case BTF_KIND_TYPE_TAG: + /* All other types are added to split BTF. */ + if (adding_to_base) + continue; + err = btf_add_type(&dist->pipe, t); + break; + default: + pr_warn("unexpected kind when adding base type '%s'[%u] of kind [%u] to distilled base BTF.\n", + name, i, kind); + return -EINVAL; + + } + if (err < 0) + break; + dist->id_map[i] = id++; + } + return err; +} + +/* Split BTF ids without a mapping will be shifted downwards since distilled + * base BTF is smaller than the original base BTF. For those that have a + * mapping (either to base or updated split BTF), update the id based on + * that mapping. + */ +static int btf_update_distilled_type_ids(struct btf_distill *dist, __u32 i) +{ + struct btf_type *t = btf_type_by_id(dist->pipe.dst, i); + struct btf_field_iter it; + __u32 *id; + int err; + + err = btf_field_iter_init(&it, t, BTF_FIELD_ITER_IDS); + if (err) + return err; + while ((id = btf_field_iter_next(&it))) { + if (dist->id_map[*id]) + *id = dist->id_map[*id]; + else if (*id >= dist->split_start_id) + *id -= dist->diff_id; + } + return 0; +} + +/* Create updated split BTF with distilled base BTF; distilled base BTF + * consists of BTF information required to clarify the types that split + * BTF refers to, omitting unneeded details. Specifically it will contain + * base types and memberless definitions of named structs, unions and enumerated + * types. Associated reference types like pointers, arrays and anonymous + * structs, unions and enumerated types will be added to split BTF. + * Size is recorded for named struct/unions to help guide matching to the + * target base BTF during later relocation. + * + * The only case where structs, unions or enumerated types are fully represented + * is when they are anonymous; in such cases, the anonymous type is added to + * split BTF in full. + * + * We return newly-created split BTF where the split BTF refers to a newly-created + * distilled base BTF. Both must be freed separately by the caller. + */ +int btf__distill_base(const struct btf *src_btf, struct btf **new_base_btf, + struct btf **new_split_btf) +{ + struct btf *new_base = NULL, *new_split = NULL; + const struct btf *old_base; + unsigned int n = btf__type_cnt(src_btf); + struct btf_distill dist = {}; + struct btf_type *t; + int i, err = 0; + + /* src BTF must be split BTF. */ + old_base = btf__base_btf(src_btf); + if (!new_base_btf || !new_split_btf || !old_base) + return libbpf_err(-EINVAL); + + new_base = btf__new_empty(); + if (!new_base) + return libbpf_err(-ENOMEM); + dist.id_map = calloc(n, sizeof(*dist.id_map)); + if (!dist.id_map) { + err = -ENOMEM; + goto done; + } + dist.pipe.src = src_btf; + dist.pipe.dst = new_base; + dist.pipe.str_off_map = hashmap__new(btf_dedup_identity_hash_fn, btf_dedup_equal_fn, NULL); + if (IS_ERR(dist.pipe.str_off_map)) { + err = -ENOMEM; + goto done; + } + dist.split_start_id = btf__type_cnt(old_base); + dist.split_start_str = old_base->hdr->str_len; + + /* Pass over src split BTF; generate the list of base BTF type ids it + * references; these will constitute our distilled BTF set to be + * distributed over base and split BTF as appropriate. + */ + for (i = src_btf->start_id; i < n; i++) { + err = btf_add_distilled_type_ids(&dist, i); + if (err < 0) + goto done; + } + /* Next add types for each of the required references to base BTF and split BTF + * in turn. + */ + err = btf_add_distilled_types(&dist); + if (err < 0) + goto done; + + /* Create new split BTF with distilled base BTF as its base; the final + * state is split BTF with distilled base BTF that represents enough + * about its base references to allow it to be relocated with the base + * BTF available. + */ + new_split = btf__new_empty_split(new_base); + if (!new_split_btf) { + err = -errno; + goto done; + } + dist.pipe.dst = new_split; + /* First add all split types */ + for (i = src_btf->start_id; i < n; i++) { + t = btf_type_by_id(src_btf, i); + err = btf_add_type(&dist.pipe, t); + if (err < 0) + goto done; + } + /* Now add distilled types to split BTF that are not added to base. */ + err = btf_add_distilled_types(&dist); + if (err < 0) + goto done; + + /* All split BTF ids will be shifted downwards since there are less base + * BTF ids in distilled base BTF. + */ + dist.diff_id = dist.split_start_id - btf__type_cnt(new_base); + + n = btf__type_cnt(new_split); + /* Now update base/split BTF ids. */ + for (i = 1; i < n; i++) { + err = btf_update_distilled_type_ids(&dist, i); + if (err < 0) + break; + } +done: + free(dist.id_map); + hashmap__free(dist.pipe.str_off_map); + if (err) { + btf__free(new_split); + btf__free(new_base); + return libbpf_err(err); + } + *new_base_btf = new_base; + *new_split_btf = new_split; + + return 0; +} diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index 8e6880d91c84..cb08ee9a5a10 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h @@ -107,6 +107,27 @@ LIBBPF_API struct btf *btf__new_empty(void); */ LIBBPF_API struct btf *btf__new_empty_split(struct btf *base_btf); +/** + * @brief **btf__distill_base()** creates new versions of the split BTF + * *src_btf* and its base BTF. The new base BTF will only contain the types + * needed to improve robustness of the split BTF to small changes in base BTF. + * When that split BTF is loaded against a (possibly changed) base, this + * distilled base BTF will help update references to that (possibly changed) + * base BTF. + * + * Both the new split and its associated new base BTF must be freed by + * the caller. + * + * If successful, 0 is returned and **new_base_btf** and **new_split_btf** + * will point at new base/split BTF. Both the new split and its associated + * new base BTF must be freed by the caller. + * + * A negative value is returned on error and the thread-local `errno` variable + * is set to the error code as well. + */ +LIBBPF_API int btf__distill_base(const struct btf *src_btf, struct btf **new_base_btf, + struct btf **new_split_btf); + LIBBPF_API struct btf *btf__parse(const char *path, struct btf_ext **btf_ext); LIBBPF_API struct btf *btf__parse_split(const char *path, struct btf *base_btf); LIBBPF_API struct btf *btf__parse_elf(const char *path, struct btf_ext **btf_ext); diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index 40595233dc7f..175d1536e070 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map @@ -419,6 +419,7 @@ LIBBPF_1.4.0 { LIBBPF_1.5.0 { global: + btf__distill_base; bpf_map__autoattach; bpf_map__set_autoattach; bpf_program__attach_sockmap; |