linux/tools/bpf/bpftool/btf.c
Andrii Nakryiko c93cc69004 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>
2019-04-25 21:45:14 -07:00

587 lines
13 KiB
C

// 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);
}