Commit 5b84bd10 authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

libbpf: Add support for BTF_KIND_TAG 



Add BTF_KIND_TAG support for parsing and dedup.
Also added sanitization for BTF_KIND_TAG. If BTF_KIND_TAG is not
supported in the kernel, sanitize it to INTs.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210914223025.246687-1-yhs@fb.com
parent 30025e8b

tools/lib/bpf/btf.c

+68 −0
Original line number Diff line number Diff line
@@ -304,6 +304,8 @@ static int btf_type_size(const struct btf_type *t) 
		return base_size + sizeof(struct btf_var);

	case BTF_KIND_DATASEC:

		return base_size + vlen * sizeof(struct btf_var_secinfo);

	case BTF_KIND_TAG:

		return base_size + sizeof(struct btf_tag);

	default:

		pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));

		return -EINVAL;
@@ -376,6 +378,9 @@ static int btf_bswap_type_rest(struct btf_type *t) 
			v->size = bswap_32(v->size);

		}

		return 0;

	case BTF_KIND_TAG:

		btf_tag(t)->component_idx = bswap_32(btf_tag(t)->component_idx);

		return 0;

	default:

		pr_debug("Unsupported BTF_KIND:%u\n", btf_kind(t));

		return -EINVAL;
@@ -586,6 +591,7 @@ __s64 btf__resolve_size(const struct btf *btf, __u32 type_id) 
		case BTF_KIND_CONST:

		case BTF_KIND_RESTRICT:

		case BTF_KIND_VAR:

		case BTF_KIND_TAG:

			type_id = t->type;

			break;

		case BTF_KIND_ARRAY:
@@ -2440,6 +2446,48 @@ int btf__add_datasec_var_info(struct btf *btf, int var_type_id, __u32 offset, __ 
	return 0;

}



/*

 * Append new BTF_KIND_TAG type with:

 *   - *value* - non-empty/non-NULL string;

 *   - *ref_type_id* - referenced type ID, it might not exist yet;

 *   - *component_idx* - -1 for tagging reference type, otherwise struct/union

 *     member or function argument index;

 * Returns:

 *   - >0, type ID of newly added BTF type;

 *   - <0, on error.

 */

int btf__add_tag(struct btf *btf, const char *value, int ref_type_id,

		 int component_idx)

{

	struct btf_type *t;

	int sz, value_off;



	if (!value || !value[0] || component_idx < -1)

		return libbpf_err(-EINVAL);



	if (validate_type_id(ref_type_id))

		return libbpf_err(-EINVAL);



	if (btf_ensure_modifiable(btf))

		return libbpf_err(-ENOMEM);



	sz = sizeof(struct btf_type) + sizeof(struct btf_tag);

	t = btf_add_type_mem(btf, sz);

	if (!t)

		return libbpf_err(-ENOMEM);



	value_off = btf__add_str(btf, value);

	if (value_off < 0)

		return value_off;



	t->name_off = value_off;

	t->info = btf_type_info(BTF_KIND_TAG, 0, false);

	t->type = ref_type_id;

	btf_tag(t)->component_idx = component_idx;



	return btf_commit_type(btf, sz);

}



struct btf_ext_sec_setup_param {

	__u32 off;

	__u32 len;
@@ -3535,6 +3583,7 @@ static int btf_dedup_prep(struct btf_dedup *d) 
			h = btf_hash_common(t);

			break;

		case BTF_KIND_INT:

		case BTF_KIND_TAG:

			h = btf_hash_int_tag(t);

			break;

		case BTF_KIND_ENUM:
@@ -3590,6 +3639,7 @@ static int btf_dedup_prim_type(struct btf_dedup *d, __u32 type_id) 
	case BTF_KIND_FUNC_PROTO:

	case BTF_KIND_VAR:

	case BTF_KIND_DATASEC:

	case BTF_KIND_TAG:

		return 0;



	case BTF_KIND_INT:
@@ -4210,6 +4260,23 @@ static int btf_dedup_ref_type(struct btf_dedup *d, __u32 type_id) 
		}

		break;



	case BTF_KIND_TAG:

		ref_type_id = btf_dedup_ref_type(d, t->type);

		if (ref_type_id < 0)

			return ref_type_id;

		t->type = ref_type_id;



		h = btf_hash_int_tag(t);

		for_each_dedup_cand(d, hash_entry, h) {

			cand_id = (__u32)(long)hash_entry->value;

			cand = btf_type_by_id(d->btf, cand_id);

			if (btf_equal_int_tag(t, cand)) {

				new_id = cand_id;

				break;

			}

		}

		break;



	case BTF_KIND_ARRAY: {

		struct btf_array *info = btf_array(t);
@@ -4482,6 +4549,7 @@ int btf_type_visit_type_ids(struct btf_type *t, type_id_visit_fn visit, void *ct 
	case BTF_KIND_TYPEDEF:

	case BTF_KIND_FUNC:

	case BTF_KIND_VAR:

	case BTF_KIND_TAG:

		return visit(&t->type, ctx);



	case BTF_KIND_ARRAY: {

tools/lib/bpf/btf.h

+15 −0
Original line number Diff line number Diff line
@@ -143,6 +143,10 @@ LIBBPF_API int btf__add_datasec(struct btf *btf, const char *name, __u32 byte_sz 
LIBBPF_API int btf__add_datasec_var_info(struct btf *btf, int var_type_id,

					 __u32 offset, __u32 byte_sz);



/* tag construction API */

LIBBPF_API int btf__add_tag(struct btf *btf, const char *value, int ref_type_id,

			    int component_idx);



struct btf_dedup_opts {

	unsigned int dedup_table_size;

	bool dont_resolve_fwds;
@@ -330,6 +334,11 @@ static inline bool btf_is_float(const struct btf_type *t) 
	return btf_kind(t) == BTF_KIND_FLOAT;

}



static inline bool btf_is_tag(const struct btf_type *t)

{

	return btf_kind(t) == BTF_KIND_TAG;

}



static inline __u8 btf_int_encoding(const struct btf_type *t)

{

	return BTF_INT_ENCODING(*(__u32 *)(t + 1));
@@ -398,6 +407,12 @@ btf_var_secinfos(const struct btf_type *t) 
	return (struct btf_var_secinfo *)(t + 1);

}



struct btf_tag;

static inline struct btf_tag *btf_tag(const struct btf_type *t)

{

	return (struct btf_tag *)(t + 1);

}



#ifdef __cplusplus

} /* extern "C" */

#endif

tools/lib/bpf/btf_dump.c

+3 −0
Original line number Diff line number Diff line
@@ -316,6 +316,7 @@ static int btf_dump_mark_referenced(struct btf_dump *d) 
		case BTF_KIND_TYPEDEF:

		case BTF_KIND_FUNC:

		case BTF_KIND_VAR:

		case BTF_KIND_TAG:

			d->type_states[t->type].referenced = 1;

			break;
@@ -583,6 +584,7 @@ static int btf_dump_order_type(struct btf_dump *d, __u32 id, bool through_ptr) 
	case BTF_KIND_FUNC:

	case BTF_KIND_VAR:

	case BTF_KIND_DATASEC:

	case BTF_KIND_TAG:

		d->type_states[id].order_state = ORDERED;

		return 0;
@@ -2215,6 +2217,7 @@ static int btf_dump_dump_type_data(struct btf_dump *d, 
	case BTF_KIND_FWD:

	case BTF_KIND_FUNC:

	case BTF_KIND_FUNC_PROTO:

	case BTF_KIND_TAG:

		err = btf_dump_unsupported_data(d, t, id);

		break;

	case BTF_KIND_INT:

tools/lib/bpf/libbpf.c

+28 −3
Original line number Diff line number Diff line
@@ -195,6 +195,8 @@ enum kern_feature_id { 
	FEAT_BTF_FLOAT,

	/* BPF perf link support */

	FEAT_PERF_LINK,

	/* BTF_KIND_TAG support */

	FEAT_BTF_TAG,

	__FEAT_CNT,

};
@@ -1986,6 +1988,7 @@ static const char *__btf_kind_str(__u16 kind) 
	case BTF_KIND_VAR: return "var";

	case BTF_KIND_DATASEC: return "datasec";

	case BTF_KIND_FLOAT: return "float";

	case BTF_KIND_TAG: return "tag";

	default: return "unknown";

	}

}
@@ -2485,8 +2488,9 @@ static bool btf_needs_sanitization(struct bpf_object *obj) 
	bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);

	bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);

	bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);

	bool has_tag = kernel_supports(obj, FEAT_BTF_TAG);



	return !has_func || !has_datasec || !has_func_global || !has_float;

	return !has_func || !has_datasec || !has_func_global || !has_float || !has_tag;

}



static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf)
@@ -2495,14 +2499,15 @@ static void bpf_object__sanitize_btf(struct bpf_object *obj, struct btf *btf) 
	bool has_datasec = kernel_supports(obj, FEAT_BTF_DATASEC);

	bool has_float = kernel_supports(obj, FEAT_BTF_FLOAT);

	bool has_func = kernel_supports(obj, FEAT_BTF_FUNC);

	bool has_tag = kernel_supports(obj, FEAT_BTF_TAG);

	struct btf_type *t;

	int i, j, vlen;



	for (i = 1; i <= btf__get_nr_types(btf); i++) {

		t = (struct btf_type *)btf__type_by_id(btf, i);



		if (!has_datasec && btf_is_var(t)) {

			/* replace VAR with INT */

		if ((!has_datasec && btf_is_var(t)) || (!has_tag && btf_is_tag(t))) {

			/* replace VAR/TAG with INT */

			t->info = BTF_INFO_ENC(BTF_KIND_INT, 0, 0);

			/*

			 * using size = 1 is the safest choice, 4 will be too
@@ -4212,6 +4217,23 @@ static int probe_kern_btf_float(void) 
					     strs, sizeof(strs)));

}



static int probe_kern_btf_tag(void)

{

	static const char strs[] = "\0tag";

	__u32 types[] = {

		/* int */

		BTF_TYPE_INT_ENC(0, BTF_INT_SIGNED, 0, 32, 4),  /* [1] */

		/* VAR x */                                     /* [2] */

		BTF_TYPE_ENC(1, BTF_INFO_ENC(BTF_KIND_VAR, 0, 0), 1),

		BTF_VAR_STATIC,

		/* attr */

		BTF_TYPE_TAG_ENC(1, 2, -1),

	};



	return probe_fd(libbpf__load_raw_btf((char *)types, sizeof(types),

					     strs, sizeof(strs)));

}



static int probe_kern_array_mmap(void)

{

	struct bpf_create_map_attr attr = {
@@ -4428,6 +4450,9 @@ static struct kern_feature_desc { 
	[FEAT_PERF_LINK] = {

		"BPF perf link support", probe_perf_link,

	},

	[FEAT_BTF_TAG] = {

		"BTF_KIND_TAG support", probe_kern_btf_tag,

	},

};



static bool kernel_supports(const struct bpf_object *obj, enum kern_feature_id feat_id)

tools/lib/bpf/libbpf.map

+2 −0
Original line number Diff line number Diff line
@@ -388,4 +388,6 @@ LIBBPF_0.5.0 { 
} LIBBPF_0.4.0;



LIBBPF_0.6.0 {

	global:

		btf__add_tag;

} LIBBPF_0.5.0;