bpftool: add ability to dump BTF types
Add new `btf dump` sub-command to bpftool. It allows to dump
human-readable low-level BTF types representation of BTF types. BTF can
be retrieved from few different sources:
- from BTF object by ID;
- from PROG, if it has associated BTF;
- from MAP, if it has associated BTF data; it's possible to narrow
down types to either key type, value type, both, or all BTF types;
- from ELF file (.BTF section).
Output format mostly follows BPF verifier log format with few notable
exceptions:
- all the type/field/param/etc names are enclosed in single quotes to
allow easier grepping and to stand out a little bit more;
- FUNC_PROTO output follows STRUCT/UNION/ENUM format of having one
line per each argument; this is more uniform and allows easy
grepping, as opposed to succinct, but inconvenient format that BPF
verifier log is using.
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Yonghong Song <yhs@fb.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
new file mode 100644
index 0000000..58a2cd0
--- /dev/null
+++ b/tools/bpf/bpftool/btf.c
@@ -0,0 +1,586 @@
+// 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 <gelf.h>
+#include <bpf.h>
+#include <linux/btf.h>
+
+#include "btf.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",
+};
+
+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_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_KIND(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:
+ if (json_output)
+ jsonw_uint_field(w, "type_id", t->type);
+ else
+ printf(" type_id=%u", t->type);
+ 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 bool check_btf_endianness(GElf_Ehdr *ehdr)
+{
+ static unsigned int const endian = 1;
+
+ switch (ehdr->e_ident[EI_DATA]) {
+ case ELFDATA2LSB:
+ return *(unsigned char const *)&endian == 1;
+ case ELFDATA2MSB:
+ return *(unsigned char const *)&endian == 0;
+ default:
+ return 0;
+ }
+}
+
+static int btf_load_from_elf(const char *path, struct btf **btf)
+{
+ int err = -1, fd = -1, idx = 0;
+ Elf_Data *btf_data = NULL;
+ Elf_Scn *scn = NULL;
+ Elf *elf = NULL;
+ GElf_Ehdr ehdr;
+
+ if (elf_version(EV_CURRENT) == EV_NONE) {
+ p_err("failed to init libelf for %s", path);
+ return -1;
+ }
+
+ fd = open(path, O_RDONLY);
+ if (fd < 0) {
+ p_err("failed to open %s: %s", path, strerror(errno));
+ return -1;
+ }
+
+ elf = elf_begin(fd, ELF_C_READ, NULL);
+ if (!elf) {
+ p_err("failed to open %s as ELF file", path);
+ goto done;
+ }
+ if (!gelf_getehdr(elf, &ehdr)) {
+ p_err("failed to get EHDR from %s", path);
+ goto done;
+ }
+ if (!check_btf_endianness(&ehdr)) {
+ p_err("non-native ELF endianness is not supported");
+ goto done;
+ }
+ if (!elf_rawdata(elf_getscn(elf, ehdr.e_shstrndx), NULL)) {
+ p_err("failed to get e_shstrndx from %s\n", path);
+ goto done;
+ }
+
+ while ((scn = elf_nextscn(elf, scn)) != NULL) {
+ GElf_Shdr sh;
+ char *name;
+
+ idx++;
+ if (gelf_getshdr(scn, &sh) != &sh) {
+ p_err("failed to get section(%d) header from %s",
+ idx, path);
+ goto done;
+ }
+ name = elf_strptr(elf, ehdr.e_shstrndx, sh.sh_name);
+ if (!name) {
+ p_err("failed to get section(%d) name from %s",
+ idx, path);
+ goto done;
+ }
+ if (strcmp(name, BTF_ELF_SEC) == 0) {
+ btf_data = elf_getdata(scn, 0);
+ if (!btf_data) {
+ p_err("failed to get section(%d, %s) data from %s",
+ idx, name, path);
+ goto done;
+ }
+ break;
+ }
+ }
+
+ if (!btf_data) {
+ p_err("%s ELF section not found in %s", BTF_ELF_SEC, path);
+ goto done;
+ }
+
+ *btf = btf__new(btf_data->d_buf, btf_data->d_size);
+ if (IS_ERR(*btf)) {
+ err = PTR_ERR(*btf);
+ *btf = NULL;
+ p_err("failed to load BTF data from %s: %s",
+ path, strerror(err));
+ goto done;
+ }
+
+ err = 0;
+done:
+ if (err) {
+ if (*btf) {
+ btf__free(*btf);
+ *btf = NULL;
+ }
+ }
+ if (elf)
+ elf_end(elf);
+ close(fd);
+ return err;
+}
+
+static int do_dump(int argc, char **argv)
+{
+ struct btf *btf = NULL;
+ __u32 root_type_ids[2];
+ int root_type_cnt = 0;
+ __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")) {
+ err = btf_load_from_elf(*argv, &btf);
+ if (err)
+ goto done;
+ NEXT_ARG();
+ } else {
+ err = -1;
+ p_err("unrecognized BTF source specifier: '%s'", src);
+ 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;
+ }
+ }
+
+ dump_btf_raw(btf, root_type_ids, root_type_cnt);
+
+done:
+ close(fd);
+ btf__free(btf);
+ return err;
+}
+
+static int do_help(int argc, char **argv)
+{
+ if (json_output) {
+ jsonw_null(json_wtr);
+ return 0;
+ }
+
+ fprintf(stderr,
+ "Usage: %s btf dump BTF_SRC\n"
+ " %s btf help\n"
+ "\n"
+ " BTF_SRC := { id BTF_ID | prog PROG | map MAP [{key | value | kv | all}] | file FILE }\n"
+ " " HELP_SPEC_MAP "\n"
+ " " HELP_SPEC_PROGRAM "\n"
+ " " HELP_SPEC_OPTIONS "\n"
+ "",
+ bin_name, bin_name);
+
+ return 0;
+}
+
+static const struct cmd cmds[] = {
+ { "help", do_help },
+ { "dump", do_dump },
+ { 0 }
+};
+
+int do_btf(int argc, char **argv)
+{
+ return cmd_select(cmds, argc, argv, do_help);
+}