samples/bpf/bpf_load.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <stdio.h>
   3 #include <sys/types.h>
   4 #include <sys/stat.h>
   5 #include <fcntl.h>
   6 #include <libelf.h>
   7 #include <gelf.h>
   8 #include <errno.h>
   9 #include <unistd.h>
  10 #include <string.h>
  11 #include <stdbool.h>
  12 #include <stdlib.h>
  13 #include <linux/bpf.h>
  14 #include <linux/filter.h>
  15 #include <linux/perf_event.h>
  16 #include <linux/netlink.h>
  17 #include <linux/rtnetlink.h>
  18 #include <linux/types.h>
  19 #include <sys/types.h>
  20 #include <sys/socket.h>
  21 #include <sys/syscall.h>
  22 #include <sys/ioctl.h>
  23 #include <sys/mman.h>
  24 #include <poll.h>
  25 #include <ctype.h>
  26 #include <assert.h>
  27 #include "libbpf.h"
  28 #include "bpf_load.h"
  29 #include "perf-sys.h"
  30
  31 #define DEBUGFS "/sys/kernel/debug/tracing/"
  32
  33 static char license[128];
  34 static int kern_version;
  35 static bool processed_sec[128];
  36 char bpf_log_buf[BPF_LOG_BUF_SIZE];
  37 int map_fd[MAX_MAPS];
  38 int prog_fd[MAX_PROGS];
  39 int event_fd[MAX_PROGS];
  40 int prog_cnt;
  41 int prog_array_fd = -1;
  42
  43 struct bpf_map_data map_data[MAX_MAPS];
  44 int map_data_count = 0;
  45
  46 static int populate_prog_array(const char *event, int prog_fd)
  47 {
  48         int ind = atoi(event), err;
  49
  50         err = bpf_map_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY);
  51         if (err < 0) {
  52                 printf("failed to store prog_fd in prog_array\n");
  53                 return -1;
  54         }
  55         return 0;
  56 }
  57
  58 static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
  59 {
  60         bool is_socket = strncmp(event, "socket", 6) == 0;
  61         bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
  62         bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
  63         bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0;
  64         bool is_xdp = strncmp(event, "xdp", 3) == 0;
  65         bool is_perf_event = strncmp(event, "perf_event", 10) == 0;
  66         bool is_cgroup_skb = strncmp(event, "cgroup/skb", 10) == 0;
  67         bool is_cgroup_sk = strncmp(event, "cgroup/sock", 11) == 0;
  68         bool is_sockops = strncmp(event, "sockops", 7) == 0;
  69         bool is_sk_skb = strncmp(event, "sk_skb", 6) == 0;
  70         size_t insns_cnt = size / sizeof(struct bpf_insn);
  71         enum bpf_prog_type prog_type;
  72         char buf[256];
  73         int fd, efd, err, id;
  74         struct perf_event_attr attr = {};
  75
  76         attr.type = PERF_TYPE_TRACEPOINT;
  77         attr.sample_type = PERF_SAMPLE_RAW;
  78         attr.sample_period = 1;
  79         attr.wakeup_events = 1;
  80
  81         if (is_socket) {
  82                 prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
  83         } else if (is_kprobe || is_kretprobe) {
  84                 prog_type = BPF_PROG_TYPE_KPROBE;
  85         } else if (is_tracepoint) {
  86                 prog_type = BPF_PROG_TYPE_TRACEPOINT;
  87         } else if (is_xdp) {
  88                 prog_type = BPF_PROG_TYPE_XDP;
  89         } else if (is_perf_event) {
  90                 prog_type = BPF_PROG_TYPE_PERF_EVENT;
  91         } else if (is_cgroup_skb) {
  92                 prog_type = BPF_PROG_TYPE_CGROUP_SKB;
  93         } else if (is_cgroup_sk) {
  94                 prog_type = BPF_PROG_TYPE_CGROUP_SOCK;
  95         } else if (is_sockops) {
  96                 prog_type = BPF_PROG_TYPE_SOCK_OPS;
  97         } else if (is_sk_skb) {
  98                 prog_type = BPF_PROG_TYPE_SK_SKB;
  99         } else {
 100                 printf("Unknown event '%s'\n", event);
 101                 return -1;
 102         }
 103
 104         fd = bpf_load_program(prog_type, prog, insns_cnt, license, kern_version,
 105                               bpf_log_buf, BPF_LOG_BUF_SIZE);
 106         if (fd < 0) {
 107                 printf("bpf_load_program() err=%d\n%s", errno, bpf_log_buf);
 108                 return -1;
 109         }
 110
 111         prog_fd[prog_cnt++] = fd;
 112
 113         if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk)
 114                 return 0;
 115
 116         if (is_socket || is_sockops || is_sk_skb) {
 117                 if (is_socket)
 118                         event += 6;
 119                 else
 120                         event += 7;
 121                 if (*event != '/')
 122                         return 0;
 123                 event++;
 124                 if (!isdigit(*event)) {
 125                         printf("invalid prog number\n");
 126                         return -1;
 127                 }
 128                 return populate_prog_array(event, fd);
 129         }
 130
 131         if (is_kprobe || is_kretprobe) {
 132                 if (is_kprobe)
 133                         event += 7;
 134                 else
 135                         event += 10;
 136
 137                 if (*event == 0) {
 138                         printf("event name cannot be empty\n");
 139                         return -1;
 140                 }
 141
 142                 if (isdigit(*event))
 143                         return populate_prog_array(event, fd);
 144
 145                 snprintf(buf, sizeof(buf),
 146                          "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
 147                          is_kprobe ? 'p' : 'r', event, event);
 148                 err = system(buf);
 149                 if (err < 0) {
 150                         printf("failed to create kprobe '%s' error '%s'\n",
 151                                event, strerror(errno));
 152                         return -1;
 153                 }
 154
 155                 strcpy(buf, DEBUGFS);
 156                 strcat(buf, "events/kprobes/");
 157                 strcat(buf, event);
 158                 strcat(buf, "/id");
 159         } else if (is_tracepoint) {
 160                 event += 11;
 161
 162                 if (*event == 0) {
 163                         printf("event name cannot be empty\n");
 164                         return -1;
 165                 }
 166                 strcpy(buf, DEBUGFS);
 167                 strcat(buf, "events/");
 168                 strcat(buf, event);
 169                 strcat(buf, "/id");
 170         }
 171
 172         efd = open(buf, O_RDONLY, 0);
 173         if (efd < 0) {
 174                 printf("failed to open event %s\n", event);
 175                 return -1;
 176         }
 177
 178         err = read(efd, buf, sizeof(buf));
 179         if (err < 0 || err >= sizeof(buf)) {
 180                 printf("read from '%s' failed '%s'\n", event, strerror(errno));
 181                 return -1;
 182         }
 183
 184         close(efd);
 185
 186         buf[err] = 0;
 187         id = atoi(buf);
 188         attr.config = id;
 189
 190         efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
 191         if (efd < 0) {
 192                 printf("event %d fd %d err %s\n", id, efd, strerror(errno));
 193                 return -1;
 194         }
 195         event_fd[prog_cnt - 1] = efd;
 196         err = ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
 197         if (err < 0) {
 198                 printf("ioctl PERF_EVENT_IOC_ENABLE failed err %s\n",
 199                        strerror(errno));
 200                 return -1;
 201         }
 202         err = ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
 203         if (err < 0) {
 204                 printf("ioctl PERF_EVENT_IOC_SET_BPF failed err %s\n",
 205                        strerror(errno));
 206                 return -1;
 207         }
 208
 209         return 0;
 210 }
 211
 212 static int load_maps(struct bpf_map_data *maps, int nr_maps,
 213                      fixup_map_cb fixup_map)
 214 {
 215         int i, numa_node;
 216
 217         for (i = 0; i < nr_maps; i++) {
 218                 if (fixup_map) {
 219                         fixup_map(&maps[i], i);
 220                         /* Allow userspace to assign map FD prior to creation */
 221                         if (maps[i].fd != -1) {
 222                                 map_fd[i] = maps[i].fd;
 223                                 continue;
 224                         }
 225                 }
 226
 227                 numa_node = maps[i].def.map_flags & BPF_F_NUMA_NODE ?
 228                         maps[i].def.numa_node : -1;
 229
 230                 if (maps[i].def.type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
 231                     maps[i].def.type == BPF_MAP_TYPE_HASH_OF_MAPS) {
 232                         int inner_map_fd = map_fd[maps[i].def.inner_map_idx];
 233
 234                         map_fd[i] = bpf_create_map_in_map_node(maps[i].def.type,
 235                                                         maps[i].name,
 236                                                         maps[i].def.key_size,
 237                                                         inner_map_fd,
 238                                                         maps[i].def.max_entries,
 239                                                         maps[i].def.map_flags,
 240                                                         numa_node);
 241                 } else {
 242                         map_fd[i] = bpf_create_map_node(maps[i].def.type,
 243                                                         maps[i].name,
 244                                                         maps[i].def.key_size,
 245                                                         maps[i].def.value_size,
 246                                                         maps[i].def.max_entries,
 247                                                         maps[i].def.map_flags,
 248                                                         numa_node);
 249                 }
 250                 if (map_fd[i] < 0) {
 251                         printf("failed to create a map: %d %s\n",
 252                                errno, strerror(errno));
 253                         return 1;
 254                 }
 255                 maps[i].fd = map_fd[i];
 256
 257                 if (maps[i].def.type == BPF_MAP_TYPE_PROG_ARRAY)
 258                         prog_array_fd = map_fd[i];
 259         }
 260         return 0;
 261 }
 262
 263 static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
 264                    GElf_Shdr *shdr, Elf_Data **data)
 265 {
 266         Elf_Scn *scn;
 267
 268         scn = elf_getscn(elf, i);
 269         if (!scn)
 270                 return 1;
 271
 272         if (gelf_getshdr(scn, shdr) != shdr)
 273                 return 2;
 274
 275         *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
 276         if (!*shname || !shdr->sh_size)
 277                 return 3;
 278
 279         *data = elf_getdata(scn, 0);
 280         if (!*data || elf_getdata(scn, *data) != NULL)
 281                 return 4;
 282
 283         return 0;
 284 }
 285
 286 static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
 287                                 GElf_Shdr *shdr, struct bpf_insn *insn,
 288                                 struct bpf_map_data *maps, int nr_maps)
 289 {
 290         int i, nrels;
 291
 292         nrels = shdr->sh_size / shdr->sh_entsize;
 293
 294         for (i = 0; i < nrels; i++) {
 295                 GElf_Sym sym;
 296                 GElf_Rel rel;
 297                 unsigned int insn_idx;
 298                 bool match = false;
 299                 int j, map_idx;
 300
 301                 gelf_getrel(data, i, &rel);
 302
 303                 insn_idx = rel.r_offset / sizeof(struct bpf_insn);
 304
 305                 gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
 306
 307                 if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
 308                         printf("invalid relo for insn[%d].code 0x%x\n",
 309                                insn_idx, insn[insn_idx].code);
 310                         return 1;
 311                 }
 312                 insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
 313
 314                 /* Match FD relocation against recorded map_data[] offset */
 315                 for (map_idx = 0; map_idx < nr_maps; map_idx++) {
 316                         if (maps[map_idx].elf_offset == sym.st_value) {
 317                                 match = true;
 318                                 break;
 319                         }
 320                 }
 321                 if (match) {
 322                         insn[insn_idx].imm = maps[map_idx].fd;
 323                 } else {
 324                         printf("invalid relo for insn[%d] no map_data match\n",
 325                                insn_idx);
 326                         return 1;
 327                 }
 328         }
 329
 330         return 0;
 331 }
 332
 333 static int cmp_symbols(const void *l, const void *r)
 334 {
 335         const GElf_Sym *lsym = (const GElf_Sym *)l;
 336         const GElf_Sym *rsym = (const GElf_Sym *)r;
 337
 338         if (lsym->st_value < rsym->st_value)
 339                 return -1;
 340         else if (lsym->st_value > rsym->st_value)
 341                 return 1;
 342         else
 343                 return 0;
 344 }
 345
 346 static int load_elf_maps_section(struct bpf_map_data *maps, int maps_shndx,
 347                                  Elf *elf, Elf_Data *symbols, int strtabidx)
 348 {
 349         int map_sz_elf, map_sz_copy;
 350         bool validate_zero = false;
 351         Elf_Data *data_maps;
 352         int i, nr_maps;
 353         GElf_Sym *sym;
 354         Elf_Scn *scn;
 355         int copy_sz;
 356
 357         if (maps_shndx < 0)
 358                 return -EINVAL;
 359         if (!symbols)
 360                 return -EINVAL;
 361
 362         /* Get data for maps section via elf index */
 363         scn = elf_getscn(elf, maps_shndx);
 364         if (scn)
 365                 data_maps = elf_getdata(scn, NULL);
 366         if (!scn || !data_maps) {
 367                 printf("Failed to get Elf_Data from maps section %d\n",
 368                        maps_shndx);
 369                 return -EINVAL;
 370         }
 371
 372         /* For each map get corrosponding symbol table entry */
 373         sym = calloc(MAX_MAPS+1, sizeof(GElf_Sym));
 374         for (i = 0, nr_maps = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) {
 375                 assert(nr_maps < MAX_MAPS+1);
 376                 if (!gelf_getsym(symbols, i, &sym[nr_maps]))
 377                         continue;
 378                 if (sym[nr_maps].st_shndx != maps_shndx)
 379                         continue;
 380                 /* Only increment iif maps section */
 381                 nr_maps++;
 382         }
 383
 384         /* Align to map_fd[] order, via sort on offset in sym.st_value */
 385         qsort(sym, nr_maps, sizeof(GElf_Sym), cmp_symbols);
 386
 387         /* Keeping compatible with ELF maps section changes
 388          * ------------------------------------------------
 389          * The program size of struct bpf_map_def is known by loader
 390          * code, but struct stored in ELF file can be different.
 391          *
 392          * Unfortunately sym[i].st_size is zero.  To calculate the
 393          * struct size stored in the ELF file, assume all struct have
 394          * the same size, and simply divide with number of map
 395          * symbols.
 396          */
 397         map_sz_elf = data_maps->d_size / nr_maps;
 398         map_sz_copy = sizeof(struct bpf_map_def);
 399         if (map_sz_elf < map_sz_copy) {
 400                 /*
 401                  * Backward compat, loading older ELF file with
 402                  * smaller struct, keeping remaining bytes zero.
 403                  */
 404                 map_sz_copy = map_sz_elf;
 405         } else if (map_sz_elf > map_sz_copy) {
 406                 /*
 407                  * Forward compat, loading newer ELF file with larger
 408                  * struct with unknown features. Assume zero means
 409                  * feature not used.  Thus, validate rest of struct
 410                  * data is zero.
 411                  */
 412                 validate_zero = true;
 413         }
 414
 415         /* Memcpy relevant part of ELF maps data to loader maps */
 416         for (i = 0; i < nr_maps; i++) {
 417                 unsigned char *addr, *end;
 418                 struct bpf_map_def *def;
 419                 const char *map_name;
 420                 size_t offset;
 421
 422                 map_name = elf_strptr(elf, strtabidx, sym[i].st_name);
 423                 maps[i].name = strdup(map_name);
 424                 if (!maps[i].name) {
 425                         printf("strdup(%s): %s(%d)\n", map_name,
 426                                strerror(errno), errno);
 427                         free(sym);
 428                         return -errno;
 429                 }
 430
 431                 /* Symbol value is offset into ELF maps section data area */
 432                 offset = sym[i].st_value;
 433                 def = (struct bpf_map_def *)(data_maps->d_buf + offset);
 434                 maps[i].elf_offset = offset;
 435                 memset(&maps[i].def, 0, sizeof(struct bpf_map_def));
 436                 memcpy(&maps[i].def, def, map_sz_copy);
 437
 438                 /* Verify no newer features were requested */
 439                 if (validate_zero) {
 440                         addr = (unsigned char*) def + map_sz_copy;
 441                         end  = (unsigned char*) def + map_sz_elf;
 442                         for (; addr < end; addr++) {
 443                                 if (*addr != 0) {
 444                                         free(sym);
 445                                         return -EFBIG;
 446                                 }
 447                         }
 448                 }
 449         }
 450
 451         free(sym);
 452         return nr_maps;
 453 }
 454
 455 static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
 456 {
 457         int fd, i, ret, maps_shndx = -1, strtabidx = -1;
 458         Elf *elf;
 459         GElf_Ehdr ehdr;
 460         GElf_Shdr shdr, shdr_prog;
 461         Elf_Data *data, *data_prog, *data_maps = NULL, *symbols = NULL;
 462         char *shname, *shname_prog;
 463         int nr_maps = 0;
 464
 465         /* reset global variables */
 466         kern_version = 0;
 467         memset(license, 0, sizeof(license));
 468         memset(processed_sec, 0, sizeof(processed_sec));
 469
 470         if (elf_version(EV_CURRENT) == EV_NONE)
 471                 return 1;
 472
 473         fd = open(path, O_RDONLY, 0);
 474         if (fd < 0)
 475                 return 1;
 476
 477         elf = elf_begin(fd, ELF_C_READ, NULL);
 478
 479         if (!elf)
 480                 return 1;
 481
 482         if (gelf_getehdr(elf, &ehdr) != &ehdr)
 483                 return 1;
 484
 485         /* clear all kprobes */
 486         i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
 487
 488         /* scan over all elf sections to get license and map info */
 489         for (i = 1; i < ehdr.e_shnum; i++) {
 490
 491                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 492                         continue;
 493
 494                 if (0) /* helpful for llvm debugging */
 495                         printf("section %d:%s data %p size %zd link %d flags %d\n",
 496                                i, shname, data->d_buf, data->d_size,
 497                                shdr.sh_link, (int) shdr.sh_flags);
 498
 499                 if (strcmp(shname, "license") == 0) {
 500                         processed_sec[i] = true;
 501                         memcpy(license, data->d_buf, data->d_size);
 502                 } else if (strcmp(shname, "version") == 0) {
 503                         processed_sec[i] = true;
 504                         if (data->d_size != sizeof(int)) {
 505                                 printf("invalid size of version section %zd\n",
 506                                        data->d_size);
 507                                 return 1;
 508                         }
 509                         memcpy(&kern_version, data->d_buf, sizeof(int));
 510                 } else if (strcmp(shname, "maps") == 0) {
 511                         int j;
 512
 513                         maps_shndx = i;
 514                         data_maps = data;
 515                         for (j = 0; j < MAX_MAPS; j++)
 516                                 map_data[j].fd = -1;
 517                 } else if (shdr.sh_type == SHT_SYMTAB) {
 518                         strtabidx = shdr.sh_link;
 519                         symbols = data;
 520                 }
 521         }
 522
 523         ret = 1;
 524
 525         if (!symbols) {
 526                 printf("missing SHT_SYMTAB section\n");
 527                 goto done;
 528         }
 529
 530         if (data_maps) {
 531                 nr_maps = load_elf_maps_section(map_data, maps_shndx,
 532                                                 elf, symbols, strtabidx);
 533                 if (nr_maps < 0) {
 534                         printf("Error: Failed loading ELF maps (errno:%d):%s\n",
 535                                nr_maps, strerror(-nr_maps));
 536                         ret = 1;
 537                         goto done;
 538                 }
 539                 if (load_maps(map_data, nr_maps, fixup_map))
 540                         goto done;
 541                 map_data_count = nr_maps;
 542
 543                 processed_sec[maps_shndx] = true;
 544         }
 545
 546         /* process all relo sections, and rewrite bpf insns for maps */
 547         for (i = 1; i < ehdr.e_shnum; i++) {
 548                 if (processed_sec[i])
 549                         continue;
 550
 551                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 552                         continue;
 553
 554                 if (shdr.sh_type == SHT_REL) {
 555                         struct bpf_insn *insns;
 556
 557                         /* locate prog sec that need map fixup (relocations) */
 558                         if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
 559                                     &shdr_prog, &data_prog))
 560                                 continue;
 561
 562                         if (shdr_prog.sh_type != SHT_PROGBITS ||
 563                             !(shdr_prog.sh_flags & SHF_EXECINSTR))
 564                                 continue;
 565
 566                         insns = (struct bpf_insn *) data_prog->d_buf;
 567                         processed_sec[i] = true; /* relo section */
 568
 569                         if (parse_relo_and_apply(data, symbols, &shdr, insns,
 570                                                  map_data, nr_maps))
 571                                 continue;
 572                 }
 573         }
 574
 575         /* load programs */
 576         for (i = 1; i < ehdr.e_shnum; i++) {
 577
 578                 if (processed_sec[i])
 579                         continue;
 580
 581                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 582                         continue;
 583
 584                 if (memcmp(shname, "kprobe/", 7) == 0 ||
 585                     memcmp(shname, "kretprobe/", 10) == 0 ||
 586                     memcmp(shname, "tracepoint/", 11) == 0 ||
 587                     memcmp(shname, "xdp", 3) == 0 ||
 588                     memcmp(shname, "perf_event", 10) == 0 ||
 589                     memcmp(shname, "socket", 6) == 0 ||
 590                     memcmp(shname, "cgroup/", 7) == 0 ||
 591                     memcmp(shname, "sockops", 7) == 0 ||
 592                     memcmp(shname, "sk_skb", 6) == 0) {
 593                         ret = load_and_attach(shname, data->d_buf,
 594                                               data->d_size);
 595                         if (ret != 0)
 596                                 goto done;
 597                 }
 598         }
 599
 600         ret = 0;
 601 done:
 602         close(fd);
 603         return ret;
 604 }
 605
 606 int load_bpf_file(char *path)
 607 {
 608         return do_load_bpf_file(path, NULL);
 609 }
 610
 611 int load_bpf_file_fixup_map(const char *path, fixup_map_cb fixup_map)
 612 {
 613         return do_load_bpf_file(path, fixup_map);
 614 }
 615
 616 void read_trace_pipe(void)
 617 {
 618         int trace_fd;
 619
 620         trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
 621         if (trace_fd < 0)
 622                 return;
 623
 624         while (1) {
 625                 static char buf[4096];
 626                 ssize_t sz;
 627
 628                 sz = read(trace_fd, buf, sizeof(buf) - 1);
 629                 if (sz > 0) {
 630                         buf[sz] = 0;
 631                         puts(buf);
 632                 }
 633         }
 634 }
 635
 636 #define MAX_SYMS 300000
 637 static struct ksym syms[MAX_SYMS];
 638 static int sym_cnt;
 639
 640 static int ksym_cmp(const void *p1, const void *p2)
 641 {
 642         return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
 643 }
 644
 645 int load_kallsyms(void)
 646 {
 647         FILE *f = fopen("/proc/kallsyms", "r");
 648         char func[256], buf[256];
 649         char symbol;
 650         void *addr;
 651         int i = 0;
 652
 653         if (!f)
 654                 return -ENOENT;
 655
 656         while (!feof(f)) {
 657                 if (!fgets(buf, sizeof(buf), f))
 658                         break;
 659                 if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
 660                         break;
 661                 if (!addr)
 662                         continue;
 663                 syms[i].addr = (long) addr;
 664                 syms[i].name = strdup(func);
 665                 i++;
 666         }
 667         sym_cnt = i;
 668         qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
 669         return 0;
 670 }
 671
 672 struct ksym *ksym_search(long key)
 673 {
 674         int start = 0, end = sym_cnt;
 675         int result;
 676
 677         while (start < end) {
 678                 size_t mid = start + (end - start) / 2;
 679
 680                 result = key - syms[mid].addr;
 681                 if (result < 0)
 682                         end = mid;
 683                 else if (result > 0)
 684                         start = mid + 1;
 685                 else
 686                         return &syms[mid];
 687         }
 688
 689         if (start >= 1 && syms[start - 1].addr < key &&
 690             key < syms[start].addr)
 691                 /* valid ksym */
 692                 return &syms[start - 1];
 693
 694         /* out of range. return _stext */
 695         return &syms[0];
 696 }
 697
 698 int set_link_xdp_fd(int ifindex, int fd, __u32 flags)
 699 {
 700         struct sockaddr_nl sa;
 701         int sock, seq = 0, len, ret = -1;
 702         char buf[4096];
 703         struct nlattr *nla, *nla_xdp;
 704         struct {
 705                 struct nlmsghdr  nh;
 706                 struct ifinfomsg ifinfo;
 707                 char             attrbuf[64];
 708         } req;
 709         struct nlmsghdr *nh;
 710         struct nlmsgerr *err;
 711
 712         memset(&sa, 0, sizeof(sa));
 713         sa.nl_family = AF_NETLINK;
 714
 715         sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 716         if (sock < 0) {
 717                 printf("open netlink socket: %s\n", strerror(errno));
 718                 return -1;
 719         }
 720
 721         if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
 722                 printf("bind to netlink: %s\n", strerror(errno));
 723                 goto cleanup;
 724         }
 725
 726         memset(&req, 0, sizeof(req));
 727         req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
 728         req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
 729         req.nh.nlmsg_type = RTM_SETLINK;
 730         req.nh.nlmsg_pid = 0;
 731         req.nh.nlmsg_seq = ++seq;
 732         req.ifinfo.ifi_family = AF_UNSPEC;
 733         req.ifinfo.ifi_index = ifindex;
 734
 735         /* started nested attribute for XDP */
 736         nla = (struct nlattr *)(((char *)&req)
 737                                 + NLMSG_ALIGN(req.nh.nlmsg_len));
 738         nla->nla_type = NLA_F_NESTED | 43/*IFLA_XDP*/;
 739         nla->nla_len = NLA_HDRLEN;
 740
 741         /* add XDP fd */
 742         nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
 743         nla_xdp->nla_type = 1/*IFLA_XDP_FD*/;
 744         nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
 745         memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
 746         nla->nla_len += nla_xdp->nla_len;
 747
 748         /* if user passed in any flags, add those too */
 749         if (flags) {
 750                 nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
 751                 nla_xdp->nla_type = 3/*IFLA_XDP_FLAGS*/;
 752                 nla_xdp->nla_len = NLA_HDRLEN + sizeof(flags);
 753                 memcpy((char *)nla_xdp + NLA_HDRLEN, &flags, sizeof(flags));
 754                 nla->nla_len += nla_xdp->nla_len;
 755         }
 756
 757         req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
 758
 759         if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
 760                 printf("send to netlink: %s\n", strerror(errno));
 761                 goto cleanup;
 762         }
 763
 764         len = recv(sock, buf, sizeof(buf), 0);
 765         if (len < 0) {
 766                 printf("recv from netlink: %s\n", strerror(errno));
 767                 goto cleanup;
 768         }
 769
 770         for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
 771              nh = NLMSG_NEXT(nh, len)) {
 772                 if (nh->nlmsg_pid != getpid()) {
 773                         printf("Wrong pid %d, expected %d\n",
 774                                nh->nlmsg_pid, getpid());
 775                         goto cleanup;
 776                 }
 777                 if (nh->nlmsg_seq != seq) {
 778                         printf("Wrong seq %d, expected %d\n",
 779                                nh->nlmsg_seq, seq);
 780                         goto cleanup;
 781                 }
 782                 switch (nh->nlmsg_type) {
 783                 case NLMSG_ERROR:
 784                         err = (struct nlmsgerr *)NLMSG_DATA(nh);
 785                         if (!err->error)
 786                                 continue;
 787                         printf("nlmsg error %s\n", strerror(-err->error));
 788                         goto cleanup;
 789                 case NLMSG_DONE:
 790                         break;
 791                 }
 792         }
 793
 794         ret = 0;
 795
 796 cleanup:
 797         close(sock);
 798         return ret;
 799 }