Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 938 insertions, 0 deletions

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
new file mode 100644
index 000000000..592803af9
--- /dev/null
+++ b/tools/bpf/bpftool/btf.c
@@ -0,0 +1,938 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/* Copyright (C) 2019 Facebook */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/err.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <bpf/bpf.h>
+#include <bpf/btf.h>
+#include <bpf/libbpf.h>
+#include <linux/btf.h>
+#include <linux/hashtable.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+
+#include "json_writer.h"
+#include "main.h"
+
+static const char * const btf_kind_str[NR_BTF_KINDS] = {
+	[BTF_KIND_UNKN]		= "UNKNOWN",
+	[BTF_KIND_INT]		= "INT",
+	[BTF_KIND_PTR]		= "PTR",
+	[BTF_KIND_ARRAY]	= "ARRAY",
+	[BTF_KIND_STRUCT]	= "STRUCT",
+	[BTF_KIND_UNION]	= "UNION",
+	[BTF_KIND_ENUM]		= "ENUM",
+	[BTF_KIND_FWD]		= "FWD",
+	[BTF_KIND_TYPEDEF]	= "TYPEDEF",
+	[BTF_KIND_VOLATILE]	= "VOLATILE",
+	[BTF_KIND_CONST]	= "CONST",
+	[BTF_KIND_RESTRICT]	= "RESTRICT",
+	[BTF_KIND_FUNC]		= "FUNC",
+	[BTF_KIND_FUNC_PROTO]	= "FUNC_PROTO",
+	[BTF_KIND_VAR]		= "VAR",
+	[BTF_KIND_DATASEC]	= "DATASEC",
+};
+
+struct btf_attach_table {
+	DECLARE_HASHTABLE(table, 16);
+};
+
+struct btf_attach_point {
+	__u32 obj_id;
+	__u32 btf_id;
+	struct hlist_node hash;
+};
+
+static const char *btf_int_enc_str(__u8 encoding)
+{
+	switch (encoding) {
+	case 0:
+		return "(none)";
+	case BTF_INT_SIGNED:
+		return "SIGNED";
+	case BTF_INT_CHAR:
+		return "CHAR";
+	case BTF_INT_BOOL:
+		return "BOOL";
+	default:
+		return "UNKN";
+	}
+}
+
+static const char *btf_var_linkage_str(__u32 linkage)
+{
+	switch (linkage) {
+	case BTF_VAR_STATIC:
+		return "static";
+	case BTF_VAR_GLOBAL_ALLOCATED:
+		return "global-alloc";
+	default:
+		return "(unknown)";
+	}
+}
+
+static const char *btf_func_linkage_str(const struct btf_type *t)
+{
+	switch (btf_vlen(t)) {
+	case BTF_FUNC_STATIC:
+		return "static";
+	case BTF_FUNC_GLOBAL:
+		return "global";
+	case BTF_FUNC_EXTERN:
+		return "extern";
+	default:
+		return "(unknown)";
+	}
+}
+
+static const char *btf_str(const struct btf *btf, __u32 off)
+{
+	if (!off)
+		return "(anon)";
+	return btf__name_by_offset(btf, off) ? : "(invalid)";
+}
+
+static int dump_btf_type(const struct btf *btf, __u32 id,
+			 const struct btf_type *t)
+{
+	json_writer_t *w = json_wtr;
+	int kind, safe_kind;
+
+	kind = BTF_INFO_KIND(t->info);
+	safe_kind = kind <= BTF_KIND_MAX ? kind : BTF_KIND_UNKN;
+
+	if (json_output) {
+		jsonw_start_object(w);
+		jsonw_uint_field(w, "id", id);
+		jsonw_string_field(w, "kind", btf_kind_str[safe_kind]);
+		jsonw_string_field(w, "name", btf_str(btf, t->name_off));
+	} else {
+		printf("[%u] %s '%s'", id, btf_kind_str[safe_kind],
+		       btf_str(btf, t->name_off));
+	}
+
+	switch (BTF_INFO_KIND(t->info)) {
+	case BTF_KIND_INT: {
+		__u32 v = *(__u32 *)(t + 1);
+		const char *enc;
+
+		enc = btf_int_enc_str(BTF_INT_ENCODING(v));
+
+		if (json_output) {
+			jsonw_uint_field(w, "size", t->size);
+			jsonw_uint_field(w, "bits_offset", BTF_INT_OFFSET(v));
+			jsonw_uint_field(w, "nr_bits", BTF_INT_BITS(v));
+			jsonw_string_field(w, "encoding", enc);
+		} else {
+			printf(" size=%u bits_offset=%u nr_bits=%u encoding=%s",
+			       t->size, BTF_INT_OFFSET(v), BTF_INT_BITS(v),
+			       enc);
+		}
+		break;
+	}
+	case BTF_KIND_PTR:
+	case BTF_KIND_CONST:
+	case BTF_KIND_VOLATILE:
+	case BTF_KIND_RESTRICT:
+	case BTF_KIND_TYPEDEF:
+		if (json_output)
+			jsonw_uint_field(w, "type_id", t->type);
+		else
+			printf(" type_id=%u", t->type);
+		break;
+	case BTF_KIND_ARRAY: {
+		const struct btf_array *arr = (const void *)(t + 1);
+
+		if (json_output) {
+			jsonw_uint_field(w, "type_id", arr->type);
+			jsonw_uint_field(w, "index_type_id", arr->index_type);
+			jsonw_uint_field(w, "nr_elems", arr->nelems);
+		} else {
+			printf(" type_id=%u index_type_id=%u nr_elems=%u",
+			       arr->type, arr->index_type, arr->nelems);
+		}
+		break;
+	}
+	case BTF_KIND_STRUCT:
+	case BTF_KIND_UNION: {
+		const struct btf_member *m = (const void *)(t + 1);
+		__u16 vlen = BTF_INFO_VLEN(t->info);
+		int i;
+
+		if (json_output) {
+			jsonw_uint_field(w, "size", t->size);
+			jsonw_uint_field(w, "vlen", vlen);
+			jsonw_name(w, "members");
+			jsonw_start_array(w);
+		} else {
+			printf(" size=%u vlen=%u", t->size, vlen);
+		}
+		for (i = 0; i < vlen; i++, m++) {
+			const char *name = btf_str(btf, m->name_off);
+			__u32 bit_off, bit_sz;
+
+			if (BTF_INFO_KFLAG(t->info)) {
+				bit_off = BTF_MEMBER_BIT_OFFSET(m->offset);
+				bit_sz = BTF_MEMBER_BITFIELD_SIZE(m->offset);
+			} else {
+				bit_off = m->offset;
+				bit_sz = 0;
+			}
+
+			if (json_output) {
+				jsonw_start_object(w);
+				jsonw_string_field(w, "name", name);
+				jsonw_uint_field(w, "type_id", m->type);
+				jsonw_uint_field(w, "bits_offset", bit_off);
+				if (bit_sz) {
+					jsonw_uint_field(w, "bitfield_size",
+							 bit_sz);
+				}
+				jsonw_end_object(w);
+			} else {
+				printf("\n\t'%s' type_id=%u bits_offset=%u",
+				       name, m->type, bit_off);
+				if (bit_sz)
+					printf(" bitfield_size=%u", bit_sz);
+			}
+		}
+		if (json_output)
+			jsonw_end_array(w);
+		break;
+	}
+	case BTF_KIND_ENUM: {
+		const struct btf_enum *v = (const void *)(t + 1);
+		__u16 vlen = BTF_INFO_VLEN(t->info);
+		int i;
+
+		if (json_output) {
+			jsonw_uint_field(w, "size", t->size);
+			jsonw_uint_field(w, "vlen", vlen);
+			jsonw_name(w, "values");
+			jsonw_start_array(w);
+		} else {
+			printf(" size=%u vlen=%u", t->size, vlen);
+		}
+		for (i = 0; i < vlen; i++, v++) {
+			const char *name = btf_str(btf, v->name_off);
+
+			if (json_output) {
+				jsonw_start_object(w);
+				jsonw_string_field(w, "name", name);
+				jsonw_uint_field(w, "val", v->val);
+				jsonw_end_object(w);
+			} else {
+				printf("\n\t'%s' val=%u", name, v->val);
+			}
+		}
+		if (json_output)
+			jsonw_end_array(w);
+		break;
+	}
+	case BTF_KIND_FWD: {
+		const char *fwd_kind = BTF_INFO_KFLAG(t->info) ? "union"
+							       : "struct";
+
+		if (json_output)
+			jsonw_string_field(w, "fwd_kind", fwd_kind);
+		else
+			printf(" fwd_kind=%s", fwd_kind);
+		break;
+	}
+	case BTF_KIND_FUNC: {
+		const char *linkage = btf_func_linkage_str(t);
+
+		if (json_output) {
+			jsonw_uint_field(w, "type_id", t->type);
+			jsonw_string_field(w, "linkage", linkage);
+		} else {
+			printf(" type_id=%u linkage=%s", t->type, linkage);
+		}
+		break;
+	}
+	case BTF_KIND_FUNC_PROTO: {
+		const struct btf_param *p = (const void *)(t + 1);
+		__u16 vlen = BTF_INFO_VLEN(t->info);
+		int i;
+
+		if (json_output) {
+			jsonw_uint_field(w, "ret_type_id", t->type);
+			jsonw_uint_field(w, "vlen", vlen);
+			jsonw_name(w, "params");
+			jsonw_start_array(w);
+		} else {
+			printf(" ret_type_id=%u vlen=%u", t->type, vlen);
+		}
+		for (i = 0; i < vlen; i++, p++) {
+			const char *name = btf_str(btf, p->name_off);
+
+			if (json_output) {
+				jsonw_start_object(w);
+				jsonw_string_field(w, "name", name);
+				jsonw_uint_field(w, "type_id", p->type);
+				jsonw_end_object(w);
+			} else {
+				printf("\n\t'%s' type_id=%u", name, p->type);
+			}
+		}
+		if (json_output)
+			jsonw_end_array(w);
+		break;
+	}
+	case BTF_KIND_VAR: {
+		const struct btf_var *v = (const void *)(t + 1);
+		const char *linkage;
+
+		linkage = btf_var_linkage_str(v->linkage);
+
+		if (json_output) {
+			jsonw_uint_field(w, "type_id", t->type);
+			jsonw_string_field(w, "linkage", linkage);
+		} else {
+			printf(" type_id=%u, linkage=%s", t->type, linkage);
+		}
+		break;
+	}
+	case BTF_KIND_DATASEC: {
+		const struct btf_var_secinfo *v = (const void *)(t+1);
+		__u16 vlen = BTF_INFO_VLEN(t->info);
+		int i;
+
+		if (json_output) {
+			jsonw_uint_field(w, "size", t->size);
+			jsonw_uint_field(w, "vlen", vlen);
+			jsonw_name(w, "vars");
+			jsonw_start_array(w);
+		} else {
+			printf(" size=%u vlen=%u", t->size, vlen);
+		}
+		for (i = 0; i < vlen; i++, v++) {
+			if (json_output) {
+				jsonw_start_object(w);
+				jsonw_uint_field(w, "type_id", v->type);
+				jsonw_uint_field(w, "offset", v->offset);
+				jsonw_uint_field(w, "size", v->size);
+				jsonw_end_object(w);
+			} else {
+				printf("\n\ttype_id=%u offset=%u size=%u",
+				       v->type, v->offset, v->size);
+			}
+		}
+		if (json_output)
+			jsonw_end_array(w);
+		break;
+	}
+	default:
+		break;
+	}
+
+	if (json_output)
+		jsonw_end_object(json_wtr);
+	else
+		printf("\n");
+
+	return 0;
+}
+
+static int dump_btf_raw(const struct btf *btf,
+			__u32 *root_type_ids, int root_type_cnt)
+{
+	const struct btf_type *t;
+	int i;
+
+	if (json_output) {
+		jsonw_start_object(json_wtr);
+		jsonw_name(json_wtr, "types");
+		jsonw_start_array(json_wtr);
+	}
+
+	if (root_type_cnt) {
+		for (i = 0; i < root_type_cnt; i++) {
+			t = btf__type_by_id(btf, root_type_ids[i]);
+			dump_btf_type(btf, root_type_ids[i], t);
+		}
+	} else {
+		int cnt = btf__get_nr_types(btf);
+
+		for (i = 1; i <= cnt; i++) {
+			t = btf__type_by_id(btf, i);
+			dump_btf_type(btf, i, t);
+		}
+	}
+
+	if (json_output) {
+		jsonw_end_array(json_wtr);
+		jsonw_end_object(json_wtr);
+	}
+	return 0;
+}
+
+static void __printf(2, 0) btf_dump_printf(void *ctx,
+					   const char *fmt, va_list args)
+{
+	vfprintf(stdout, fmt, args);
+}
+
+static int dump_btf_c(const struct btf *btf,
+		      __u32 *root_type_ids, int root_type_cnt)
+{
+	struct btf_dump *d;
+	int err = 0, i;
+
+	d = btf_dump__new(btf, NULL, NULL, btf_dump_printf);
+	if (IS_ERR(d))
+		return PTR_ERR(d);
+
+	printf("#ifndef __VMLINUX_H__\n");
+	printf("#define __VMLINUX_H__\n");
+	printf("\n");
+	printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
+	printf("#pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)\n");
+	printf("#endif\n\n");
+
+	if (root_type_cnt) {
+		for (i = 0; i < root_type_cnt; i++) {
+			err = btf_dump__dump_type(d, root_type_ids[i]);
+			if (err)
+				goto done;
+		}
+	} else {
+		int cnt = btf__get_nr_types(btf);
+
+		for (i = 1; i <= cnt; i++) {
+			err = btf_dump__dump_type(d, i);
+			if (err)
+				goto done;
+		}
+	}
+
+	printf("#ifndef BPF_NO_PRESERVE_ACCESS_INDEX\n");
+	printf("#pragma clang attribute pop\n");
+	printf("#endif\n");
+	printf("\n");
+	printf("#endif /* __VMLINUX_H__ */\n");
+
+done:
+	btf_dump__free(d);
+	return err;
+}
+
+static int do_dump(int argc, char **argv)
+{
+	struct btf *btf = NULL;
+	__u32 root_type_ids[2];
+	int root_type_cnt = 0;
+	bool dump_c = false;
+	__u32 btf_id = -1;
+	const char *src;
+	int fd = -1;
+	int err;
+
+	if (!REQ_ARGS(2)) {
+		usage();
+		return -1;
+	}
+	src = GET_ARG();
+
+	if (is_prefix(src, "map")) {
+		struct bpf_map_info info = {};
+		__u32 len = sizeof(info);
+
+		if (!REQ_ARGS(2)) {
+			usage();
+			return -1;
+		}
+
+		fd = map_parse_fd_and_info(&argc, &argv, &info, &len);
+		if (fd < 0)
+			return -1;
+
+		btf_id = info.btf_id;
+		if (argc && is_prefix(*argv, "key")) {
+			root_type_ids[root_type_cnt++] = info.btf_key_type_id;
+			NEXT_ARG();
+		} else if (argc && is_prefix(*argv, "value")) {
+			root_type_ids[root_type_cnt++] = info.btf_value_type_id;
+			NEXT_ARG();
+		} else if (argc && is_prefix(*argv, "all")) {
+			NEXT_ARG();
+		} else if (argc && is_prefix(*argv, "kv")) {
+			root_type_ids[root_type_cnt++] = info.btf_key_type_id;
+			root_type_ids[root_type_cnt++] = info.btf_value_type_id;
+			NEXT_ARG();
+		} else {
+			root_type_ids[root_type_cnt++] = info.btf_key_type_id;
+			root_type_ids[root_type_cnt++] = info.btf_value_type_id;
+		}
+	} else if (is_prefix(src, "prog")) {
+		struct bpf_prog_info info = {};
+		__u32 len = sizeof(info);
+
+		if (!REQ_ARGS(2)) {
+			usage();
+			return -1;
+		}
+
+		fd = prog_parse_fd(&argc, &argv);
+		if (fd < 0)
+			return -1;
+
+		err = bpf_obj_get_info_by_fd(fd, &info, &len);
+		if (err) {
+			p_err("can't get prog info: %s", strerror(errno));
+			goto done;
+		}
+
+		btf_id = info.btf_id;
+	} else if (is_prefix(src, "id")) {
+		char *endptr;
+
+		btf_id = strtoul(*argv, &endptr, 0);
+		if (*endptr) {
+			p_err("can't parse %s as ID", *argv);
+			return -1;
+		}
+		NEXT_ARG();
+	} else if (is_prefix(src, "file")) {
+		btf = btf__parse(*argv, NULL);
+		if (IS_ERR(btf)) {
+			err = -PTR_ERR(btf);
+			btf = NULL;
+			p_err("failed to load BTF from %s: %s",
+			      *argv, strerror(err));
+			goto done;
+		}
+		NEXT_ARG();
+	} else {
+		err = -1;
+		p_err("unrecognized BTF source specifier: '%s'", src);
+		goto done;
+	}
+
+	while (argc) {
+		if (is_prefix(*argv, "format")) {
+			NEXT_ARG();
+			if (argc < 1) {
+				p_err("expecting value for 'format' option\n");
+				err = -EINVAL;
+				goto done;
+			}
+			if (strcmp(*argv, "c") == 0) {
+				dump_c = true;
+			} else if (strcmp(*argv, "raw") == 0) {
+				dump_c = false;
+			} else {
+				p_err("unrecognized format specifier: '%s', possible values: raw, c",
+				      *argv);
+				err = -EINVAL;
+				goto done;
+			}
+			NEXT_ARG();
+		} else {
+			p_err("unrecognized option: '%s'", *argv);
+			err = -EINVAL;
+			goto done;
+		}
+	}
+
+	if (!btf) {
+		err = btf__get_from_id(btf_id, &btf);
+		if (err) {
+			p_err("get btf by id (%u): %s", btf_id, strerror(err));
+			goto done;
+		}
+		if (!btf) {
+			err = -ENOENT;
+			p_err("can't find btf with ID (%u)", btf_id);
+			goto done;
+		}
+	}
+
+	if (dump_c) {
+		if (json_output) {
+			p_err("JSON output for C-syntax dump is not supported");
+			err = -ENOTSUP;
+			goto done;
+		}
+		err = dump_btf_c(btf, root_type_ids, root_type_cnt);
+	} else {
+		err = dump_btf_raw(btf, root_type_ids, root_type_cnt);
+	}
+
+done:
+	close(fd);
+	btf__free(btf);
+	return err;
+}
+
+static int btf_parse_fd(int *argc, char ***argv)
+{
+	unsigned int id;
+	char *endptr;
+	int fd;
+
+	if (!is_prefix(*argv[0], "id")) {
+		p_err("expected 'id', got: '%s'?", **argv);
+		return -1;
+	}
+	NEXT_ARGP();
+
+	id = strtoul(**argv, &endptr, 0);
+	if (*endptr) {
+		p_err("can't parse %s as ID", **argv);
+		return -1;
+	}
+	NEXT_ARGP();
+
+	fd = bpf_btf_get_fd_by_id(id);
+	if (fd < 0)
+		p_err("can't get BTF object by id (%u): %s",
+		      id, strerror(errno));
+
+	return fd;
+}
+
+static void delete_btf_table(struct btf_attach_table *tab)
+{
+	struct btf_attach_point *obj;
+	struct hlist_node *tmp;
+
+	unsigned int bkt;
+
+	hash_for_each_safe(tab->table, bkt, tmp, obj, hash) {
+		hash_del(&obj->hash);
+		free(obj);
+	}
+}
+
+static int
+build_btf_type_table(struct btf_attach_table *tab, enum bpf_obj_type type,
+		     void *info, __u32 *len)
+{
+	static const char * const names[] = {
+		[BPF_OBJ_UNKNOWN]	= "unknown",
+		[BPF_OBJ_PROG]		= "prog",
+		[BPF_OBJ_MAP]		= "map",
+	};
+	struct btf_attach_point *obj_node;
+	__u32 btf_id, id = 0;
+	int err;
+	int fd;
+
+	while (true) {
+		switch (type) {
+		case BPF_OBJ_PROG:
+			err = bpf_prog_get_next_id(id, &id);
+			break;
+		case BPF_OBJ_MAP:
+			err = bpf_map_get_next_id(id, &id);
+			break;
+		default:
+			err = -1;
+			p_err("unexpected object type: %d", type);
+			goto err_free;
+		}
+		if (err) {
+			if (errno == ENOENT) {
+				err = 0;
+				break;
+			}
+			p_err("can't get next %s: %s%s", names[type],
+			      strerror(errno),
+			      errno == EINVAL ? " -- kernel too old?" : "");
+			goto err_free;
+		}
+
+		switch (type) {
+		case BPF_OBJ_PROG:
+			fd = bpf_prog_get_fd_by_id(id);
+			break;
+		case BPF_OBJ_MAP:
+			fd = bpf_map_get_fd_by_id(id);
+			break;
+		default:
+			err = -1;
+			p_err("unexpected object type: %d", type);
+			goto err_free;
+		}
+		if (fd < 0) {
+			if (errno == ENOENT)
+				continue;
+			p_err("can't get %s by id (%u): %s", names[type], id,
+			      strerror(errno));
+			err = -1;
+			goto err_free;
+		}
+
+		memset(info, 0, *len);
+		err = bpf_obj_get_info_by_fd(fd, info, len);
+		close(fd);
+		if (err) {
+			p_err("can't get %s info: %s", names[type],
+			      strerror(errno));
+			goto err_free;
+		}
+
+		switch (type) {
+		case BPF_OBJ_PROG:
+			btf_id = ((struct bpf_prog_info *)info)->btf_id;
+			break;
+		case BPF_OBJ_MAP:
+			btf_id = ((struct bpf_map_info *)info)->btf_id;
+			break;
+		default:
+			err = -1;
+			p_err("unexpected object type: %d", type);
+			goto err_free;
+		}
+		if (!btf_id)
+			continue;
+
+		obj_node = calloc(1, sizeof(*obj_node));
+		if (!obj_node) {
+			p_err("failed to allocate memory: %s", strerror(errno));
+			err = -ENOMEM;
+			goto err_free;
+		}
+
+		obj_node->obj_id = id;
+		obj_node->btf_id = btf_id;
+		hash_add(tab->table, &obj_node->hash, obj_node->btf_id);
+	}
+
+	return 0;
+
+err_free:
+	delete_btf_table(tab);
+	return err;
+}
+
+static int
+build_btf_tables(struct btf_attach_table *btf_prog_table,
+		 struct btf_attach_table *btf_map_table)
+{
+	struct bpf_prog_info prog_info;
+	__u32 prog_len = sizeof(prog_info);
+	struct bpf_map_info map_info;
+	__u32 map_len = sizeof(map_info);
+	int err = 0;
+
+	err = build_btf_type_table(btf_prog_table, BPF_OBJ_PROG, &prog_info,
+				   &prog_len);
+	if (err)
+		return err;
+
+	err = build_btf_type_table(btf_map_table, BPF_OBJ_MAP, &map_info,
+				   &map_len);
+	if (err) {
+		delete_btf_table(btf_prog_table);
+		return err;
+	}
+
+	return 0;
+}
+
+static void
+show_btf_plain(struct bpf_btf_info *info, int fd,
+	       struct btf_attach_table *btf_prog_table,
+	       struct btf_attach_table *btf_map_table)
+{
+	struct btf_attach_point *obj;
+	int n;
+
+	printf("%u: ", info->id);
+	printf("size %uB", info->btf_size);
+
+	n = 0;
+	hash_for_each_possible(btf_prog_table->table, obj, hash, info->id) {
+		if (obj->btf_id == info->id)
+			printf("%s%u", n++ == 0 ? "  prog_ids " : ",",
+			       obj->obj_id);
+	}
+
+	n = 0;
+	hash_for_each_possible(btf_map_table->table, obj, hash, info->id) {
+		if (obj->btf_id == info->id)
+			printf("%s%u", n++ == 0 ? "  map_ids " : ",",
+			       obj->obj_id);
+	}
+	emit_obj_refs_plain(&refs_table, info->id, "\n\tpids ");
+
+	printf("\n");
+}
+
+static void
+show_btf_json(struct bpf_btf_info *info, int fd,
+	      struct btf_attach_table *btf_prog_table,
+	      struct btf_attach_table *btf_map_table)
+{
+	struct btf_attach_point *obj;
+
+	jsonw_start_object(json_wtr);	/* btf object */
+	jsonw_uint_field(json_wtr, "id", info->id);
+	jsonw_uint_field(json_wtr, "size", info->btf_size);
+
+	jsonw_name(json_wtr, "prog_ids");
+	jsonw_start_array(json_wtr);	/* prog_ids */
+	hash_for_each_possible(btf_prog_table->table, obj, hash,
+			       info->id) {
+		if (obj->btf_id == info->id)
+			jsonw_uint(json_wtr, obj->obj_id);
+	}
+	jsonw_end_array(json_wtr);	/* prog_ids */
+
+	jsonw_name(json_wtr, "map_ids");
+	jsonw_start_array(json_wtr);	/* map_ids */
+	hash_for_each_possible(btf_map_table->table, obj, hash,
+			       info->id) {
+		if (obj->btf_id == info->id)
+			jsonw_uint(json_wtr, obj->obj_id);
+	}
+	jsonw_end_array(json_wtr);	/* map_ids */
+
+	emit_obj_refs_json(&refs_table, info->id, json_wtr); /* pids */
+
+	jsonw_end_object(json_wtr);	/* btf object */
+}
+
+static int
+show_btf(int fd, struct btf_attach_table *btf_prog_table,
+	 struct btf_attach_table *btf_map_table)
+{
+	struct bpf_btf_info info = {};
+	__u32 len = sizeof(info);
+	int err;
+
+	err = bpf_obj_get_info_by_fd(fd, &info, &len);
+	if (err) {
+		p_err("can't get BTF object info: %s", strerror(errno));
+		return -1;
+	}
+
+	if (json_output)
+		show_btf_json(&info, fd, btf_prog_table, btf_map_table);
+	else
+		show_btf_plain(&info, fd, btf_prog_table, btf_map_table);
+
+	return 0;
+}
+
+static int do_show(int argc, char **argv)
+{
+	struct btf_attach_table btf_prog_table;
+	struct btf_attach_table btf_map_table;
+	int err, fd = -1;
+	__u32 id = 0;
+
+	if (argc == 2) {
+		fd = btf_parse_fd(&argc, &argv);
+		if (fd < 0)
+			return -1;
+	}
+
+	if (argc) {
+		if (fd >= 0)
+			close(fd);
+		return BAD_ARG();
+	}
+
+	hash_init(btf_prog_table.table);
+	hash_init(btf_map_table.table);
+	err = build_btf_tables(&btf_prog_table, &btf_map_table);
+	if (err) {
+		if (fd >= 0)
+			close(fd);
+		return err;
+	}
+	build_obj_refs_table(&refs_table, BPF_OBJ_BTF);
+
+	if (fd >= 0) {
+		err = show_btf(fd, &btf_prog_table, &btf_map_table);
+		close(fd);
+		goto exit_free;
+	}
+
+	if (json_output)
+		jsonw_start_array(json_wtr);	/* root array */
+
+	while (true) {
+		err = bpf_btf_get_next_id(id, &id);
+		if (err) {
+			if (errno == ENOENT) {
+				err = 0;
+				break;
+			}
+			p_err("can't get next BTF object: %s%s",
+			      strerror(errno),
+			      errno == EINVAL ? " -- kernel too old?" : "");
+			err = -1;
+			break;
+		}
+
+		fd = bpf_btf_get_fd_by_id(id);
+		if (fd < 0) {
+			if (errno == ENOENT)
+				continue;
+			p_err("can't get BTF object by id (%u): %s",
+			      id, strerror(errno));
+			err = -1;
+			break;
+		}
+
+		err = show_btf(fd, &btf_prog_table, &btf_map_table);
+		close(fd);
+		if (err)
+			break;
+	}
+
+	if (json_output)
+		jsonw_end_array(json_wtr);	/* root array */
+
+exit_free:
+	delete_btf_table(&btf_prog_table);
+	delete_btf_table(&btf_map_table);
+	delete_obj_refs_table(&refs_table);
+
+	return err;
+}
+
+static int do_help(int argc, char **argv)
+{
+	if (json_output) {
+		jsonw_null(json_wtr);
+		return 0;
+	}
+
+	fprintf(stderr,
+		"Usage: %1$s %2$s { show | list } [id BTF_ID]\n"
+		"       %1$s %2$s dump BTF_SRC [format FORMAT]\n"
+		"       %1$s %2$s help\n"
+		"\n"
+		"       BTF_SRC := { id BTF_ID | prog PROG | map MAP [{key | value | kv | all}] | file FILE }\n"
+		"       FORMAT  := { raw | c }\n"
+		"       " HELP_SPEC_MAP "\n"
+		"       " HELP_SPEC_PROGRAM "\n"
+		"       " HELP_SPEC_OPTIONS "\n"
+		"",
+		bin_name, "btf");
+
+	return 0;
+}
+
+static const struct cmd cmds[] = {
+	{ "show",	do_show },
+	{ "list",	do_show },
+	{ "help",	do_help },
+	{ "dump",	do_dump },
+	{ 0 }
+};
+
+int do_btf(int argc, char **argv)
+{
+	return cmd_select(cmds, argc, argv, do_help);
+}