bpftool: add ability to dump BTF types
authorAndrii Nakryiko <andriin@fb.com>
Thu, 25 Apr 2019 22:30:08 +0000 (15:30 -0700)
committerAlexei Starovoitov <ast@kernel.org>
Fri, 26 Apr 2019 04:45:14 +0000 (21:45 -0700)
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>
tools/bpf/bpftool/btf.c [new file with mode: 0644]
tools/bpf/bpftool/main.c
tools/bpf/bpftool/main.h

diff --git a/tools/bpf/bpftool/btf.c b/tools/bpf/bpftool/btf.c
new file mode 100644 (file)
index 0000000..58a2cd0
--- /dev/null
@@ -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);
+}
index a9d5e9e6a7327d9a8af33825e8daa93f4c06fc4e..1ac1fc520e6ab6a7f789b1b658351f3840d30e8b 100644 (file)
@@ -56,7 +56,7 @@ static int do_help(int argc, char **argv)
                "       %s batch file FILE\n"
                "       %s version\n"
                "\n"
-               "       OBJECT := { prog | map | cgroup | perf | net | feature }\n"
+               "       OBJECT := { prog | map | cgroup | perf | net | feature | btf }\n"
                "       " HELP_SPEC_OPTIONS "\n"
                "",
                bin_name, bin_name, bin_name);
@@ -188,6 +188,7 @@ static const struct cmd cmds[] = {
        { "perf",       do_perf },
        { "net",        do_net },
        { "feature",    do_feature },
+       { "btf",        do_btf },
        { "version",    do_version },
        { 0 }
 };
index 1ccc46169a1957627694469c035d0cf78a723c89..3d63feb7f852fb8cb9a23a5b6b51b25d860ffceb 100644 (file)
@@ -150,6 +150,7 @@ int do_perf(int argc, char **arg);
 int do_net(int argc, char **arg);
 int do_tracelog(int argc, char **arg);
 int do_feature(int argc, char **argv);
+int do_btf(int argc, char **argv);
 
 int parse_u32_arg(int *argc, char ***argv, __u32 *val, const char *what);
 int prog_parse_fd(int *argc, char ***argv);