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         ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
 197         ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
 198
 199         return 0;
 200 }
 201
 202 static int load_maps(struct bpf_map_data *maps, int nr_maps,
 203                      fixup_map_cb fixup_map)
 204 {
 205         int i, numa_node;
 206
 207         for (i = 0; i < nr_maps; i++) {
 208                 if (fixup_map) {
 209                         fixup_map(&maps[i], i);
 210                         /* Allow userspace to assign map FD prior to creation */
 211                         if (maps[i].fd != -1) {
 212                                 map_fd[i] = maps[i].fd;
 213                                 continue;
 214                         }
 215                 }
 216
 217                 numa_node = maps[i].def.map_flags & BPF_F_NUMA_NODE ?
 218                         maps[i].def.numa_node : -1;
 219
 220                 if (maps[i].def.type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
 221                     maps[i].def.type == BPF_MAP_TYPE_HASH_OF_MAPS) {
 222                         int inner_map_fd = map_fd[maps[i].def.inner_map_idx];
 223
 224                         map_fd[i] = bpf_create_map_in_map_node(maps[i].def.type,
 225                                                         maps[i].name,
 226                                                         maps[i].def.key_size,
 227                                                         inner_map_fd,
 228                                                         maps[i].def.max_entries,
 229                                                         maps[i].def.map_flags,
 230                                                         numa_node);
 231                 } else {
 232                         map_fd[i] = bpf_create_map_node(maps[i].def.type,
 233                                                         maps[i].name,
 234                                                         maps[i].def.key_size,
 235                                                         maps[i].def.value_size,
 236                                                         maps[i].def.max_entries,
 237                                                         maps[i].def.map_flags,
 238                                                         numa_node);
 239                 }
 240                 if (map_fd[i] < 0) {
 241                         printf("failed to create a map: %d %s\n",
 242                                errno, strerror(errno));
 243                         return 1;
 244                 }
 245                 maps[i].fd = map_fd[i];
 246
 247                 if (maps[i].def.type == BPF_MAP_TYPE_PROG_ARRAY)
 248                         prog_array_fd = map_fd[i];
 249         }
 250         return 0;
 251 }
 252
 253 static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
 254                    GElf_Shdr *shdr, Elf_Data **data)
 255 {
 256         Elf_Scn *scn;
 257
 258         scn = elf_getscn(elf, i);
 259         if (!scn)
 260                 return 1;
 261
 262         if (gelf_getshdr(scn, shdr) != shdr)
 263                 return 2;
 264
 265         *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
 266         if (!*shname || !shdr->sh_size)
 267                 return 3;
 268
 269         *data = elf_getdata(scn, 0);
 270         if (!*data || elf_getdata(scn, *data) != NULL)
 271                 return 4;
 272
 273         return 0;
 274 }
 275
 276 static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
 277                                 GElf_Shdr *shdr, struct bpf_insn *insn,
 278                                 struct bpf_map_data *maps, int nr_maps)
 279 {
 280         int i, nrels;
 281
 282         nrels = shdr->sh_size / shdr->sh_entsize;
 283
 284         for (i = 0; i < nrels; i++) {
 285                 GElf_Sym sym;
 286                 GElf_Rel rel;
 287                 unsigned int insn_idx;
 288                 bool match = false;
 289                 int j, map_idx;
 290
 291                 gelf_getrel(data, i, &rel);
 292
 293                 insn_idx = rel.r_offset / sizeof(struct bpf_insn);
 294
 295                 gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
 296
 297                 if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
 298                         printf("invalid relo for insn[%d].code 0x%x\n",
 299                                insn_idx, insn[insn_idx].code);
 300                         return 1;
 301                 }
 302                 insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
 303
 304                 /* Match FD relocation against recorded map_data[] offset */
 305                 for (map_idx = 0; map_idx < nr_maps; map_idx++) {
 306                         if (maps[map_idx].elf_offset == sym.st_value) {
 307                                 match = true;
 308                                 break;
 309                         }
 310                 }
 311                 if (match) {
 312                         insn[insn_idx].imm = maps[map_idx].fd;
 313                 } else {
 314                         printf("invalid relo for insn[%d] no map_data match\n",
 315                                insn_idx);
 316                         return 1;
 317                 }
 318         }
 319
 320         return 0;
 321 }
 322
 323 static int cmp_symbols(const void *l, const void *r)
 324 {
 325         const GElf_Sym *lsym = (const GElf_Sym *)l;
 326         const GElf_Sym *rsym = (const GElf_Sym *)r;
 327
 328         if (lsym->st_value < rsym->st_value)
 329                 return -1;
 330         else if (lsym->st_value > rsym->st_value)
 331                 return 1;
 332         else
 333                 return 0;
 334 }
 335
 336 static int load_elf_maps_section(struct bpf_map_data *maps, int maps_shndx,
 337                                  Elf *elf, Elf_Data *symbols, int strtabidx)
 338 {
 339         int map_sz_elf, map_sz_copy;
 340         bool validate_zero = false;
 341         Elf_Data *data_maps;
 342         int i, nr_maps;
 343         GElf_Sym *sym;
 344         Elf_Scn *scn;
 345         int copy_sz;
 346
 347         if (maps_shndx < 0)
 348                 return -EINVAL;
 349         if (!symbols)
 350                 return -EINVAL;
 351
 352         /* Get data for maps section via elf index */
 353         scn = elf_getscn(elf, maps_shndx);
 354         if (scn)
 355                 data_maps = elf_getdata(scn, NULL);
 356         if (!scn || !data_maps) {
 357                 printf("Failed to get Elf_Data from maps section %d\n",
 358                        maps_shndx);
 359                 return -EINVAL;
 360         }
 361
 362         /* For each map get corrosponding symbol table entry */
 363         sym = calloc(MAX_MAPS+1, sizeof(GElf_Sym));
 364         for (i = 0, nr_maps = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) {
 365                 assert(nr_maps < MAX_MAPS+1);
 366                 if (!gelf_getsym(symbols, i, &sym[nr_maps]))
 367                         continue;
 368                 if (sym[nr_maps].st_shndx != maps_shndx)
 369                         continue;
 370                 /* Only increment iif maps section */
 371                 nr_maps++;
 372         }
 373
 374         /* Align to map_fd[] order, via sort on offset in sym.st_value */
 375         qsort(sym, nr_maps, sizeof(GElf_Sym), cmp_symbols);
 376
 377         /* Keeping compatible with ELF maps section changes
 378          * ------------------------------------------------
 379          * The program size of struct bpf_map_def is known by loader
 380          * code, but struct stored in ELF file can be different.
 381          *
 382          * Unfortunately sym[i].st_size is zero.  To calculate the
 383          * struct size stored in the ELF file, assume all struct have
 384          * the same size, and simply divide with number of map
 385          * symbols.
 386          */
 387         map_sz_elf = data_maps->d_size / nr_maps;
 388         map_sz_copy = sizeof(struct bpf_map_def);
 389         if (map_sz_elf < map_sz_copy) {
 390                 /*
 391                  * Backward compat, loading older ELF file with
 392                  * smaller struct, keeping remaining bytes zero.
 393                  */
 394                 map_sz_copy = map_sz_elf;
 395         } else if (map_sz_elf > map_sz_copy) {
 396                 /*
 397                  * Forward compat, loading newer ELF file with larger
 398                  * struct with unknown features. Assume zero means
 399                  * feature not used.  Thus, validate rest of struct
 400                  * data is zero.
 401                  */
 402                 validate_zero = true;
 403         }
 404
 405         /* Memcpy relevant part of ELF maps data to loader maps */
 406         for (i = 0; i < nr_maps; i++) {
 407                 unsigned char *addr, *end;
 408                 struct bpf_map_def *def;
 409                 const char *map_name;
 410                 size_t offset;
 411
 412                 map_name = elf_strptr(elf, strtabidx, sym[i].st_name);
 413                 maps[i].name = strdup(map_name);
 414                 if (!maps[i].name) {
 415                         printf("strdup(%s): %s(%d)\n", map_name,
 416                                strerror(errno), errno);
 417                         free(sym);
 418                         return -errno;
 419                 }
 420
 421                 /* Symbol value is offset into ELF maps section data area */
 422                 offset = sym[i].st_value;
 423                 def = (struct bpf_map_def *)(data_maps->d_buf + offset);
 424                 maps[i].elf_offset = offset;
 425                 memset(&maps[i].def, 0, sizeof(struct bpf_map_def));
 426                 memcpy(&maps[i].def, def, map_sz_copy);
 427
 428                 /* Verify no newer features were requested */
 429                 if (validate_zero) {
 430                         addr = (unsigned char*) def + map_sz_copy;
 431                         end  = (unsigned char*) def + map_sz_elf;
 432                         for (; addr < end; addr++) {
 433                                 if (*addr != 0) {
 434                                         free(sym);
 435                                         return -EFBIG;
 436                                 }
 437                         }
 438                 }
 439         }
 440
 441         free(sym);
 442         return nr_maps;
 443 }
 444
 445 static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
 446 {
 447         int fd, i, ret, maps_shndx = -1, strtabidx = -1;
 448         Elf *elf;
 449         GElf_Ehdr ehdr;
 450         GElf_Shdr shdr, shdr_prog;
 451         Elf_Data *data, *data_prog, *data_maps = NULL, *symbols = NULL;
 452         char *shname, *shname_prog;
 453         int nr_maps = 0;
 454
 455         /* reset global variables */
 456         kern_version = 0;
 457         memset(license, 0, sizeof(license));
 458         memset(processed_sec, 0, sizeof(processed_sec));
 459
 460         if (elf_version(EV_CURRENT) == EV_NONE)
 461                 return 1;
 462
 463         fd = open(path, O_RDONLY, 0);
 464         if (fd < 0)
 465                 return 1;
 466
 467         elf = elf_begin(fd, ELF_C_READ, NULL);
 468
 469         if (!elf)
 470                 return 1;
 471
 472         if (gelf_getehdr(elf, &ehdr) != &ehdr)
 473                 return 1;
 474
 475         /* clear all kprobes */
 476         i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
 477
 478         /* scan over all elf sections to get license and map info */
 479         for (i = 1; i < ehdr.e_shnum; i++) {
 480
 481                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 482                         continue;
 483
 484                 if (0) /* helpful for llvm debugging */
 485                         printf("section %d:%s data %p size %zd link %d flags %d\n",
 486                                i, shname, data->d_buf, data->d_size,
 487                                shdr.sh_link, (int) shdr.sh_flags);
 488
 489                 if (strcmp(shname, "license") == 0) {
 490                         processed_sec[i] = true;
 491                         memcpy(license, data->d_buf, data->d_size);
 492                 } else if (strcmp(shname, "version") == 0) {
 493                         processed_sec[i] = true;
 494                         if (data->d_size != sizeof(int)) {
 495                                 printf("invalid size of version section %zd\n",
 496                                        data->d_size);
 497                                 return 1;
 498                         }
 499                         memcpy(&kern_version, data->d_buf, sizeof(int));
 500                 } else if (strcmp(shname, "maps") == 0) {
 501                         int j;
 502
 503                         maps_shndx = i;
 504                         data_maps = data;
 505                         for (j = 0; j < MAX_MAPS; j++)
 506                                 map_data[j].fd = -1;
 507                 } else if (shdr.sh_type == SHT_SYMTAB) {
 508                         strtabidx = shdr.sh_link;
 509                         symbols = data;
 510                 }
 511         }
 512
 513         ret = 1;
 514
 515         if (!symbols) {
 516                 printf("missing SHT_SYMTAB section\n");
 517                 goto done;
 518         }
 519
 520         if (data_maps) {
 521                 nr_maps = load_elf_maps_section(map_data, maps_shndx,
 522                                                 elf, symbols, strtabidx);
 523                 if (nr_maps < 0) {
 524                         printf("Error: Failed loading ELF maps (errno:%d):%s\n",
 525                                nr_maps, strerror(-nr_maps));
 526                         ret = 1;
 527                         goto done;
 528                 }
 529                 if (load_maps(map_data, nr_maps, fixup_map))
 530                         goto done;
 531                 map_data_count = nr_maps;
 532
 533                 processed_sec[maps_shndx] = true;
 534         }
 535
 536         /* process all relo sections, and rewrite bpf insns for maps */
 537         for (i = 1; i < ehdr.e_shnum; i++) {
 538                 if (processed_sec[i])
 539                         continue;
 540
 541                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 542                         continue;
 543
 544                 if (shdr.sh_type == SHT_REL) {
 545                         struct bpf_insn *insns;
 546
 547                         /* locate prog sec that need map fixup (relocations) */
 548                         if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
 549                                     &shdr_prog, &data_prog))
 550                                 continue;
 551
 552                         if (shdr_prog.sh_type != SHT_PROGBITS ||
 553                             !(shdr_prog.sh_flags & SHF_EXECINSTR))
 554                                 continue;
 555
 556                         insns = (struct bpf_insn *) data_prog->d_buf;
 557                         processed_sec[i] = true; /* relo section */
 558
 559                         if (parse_relo_and_apply(data, symbols, &shdr, insns,
 560                                                  map_data, nr_maps))
 561                                 continue;
 562                 }
 563         }
 564
 565         /* load programs */
 566         for (i = 1; i < ehdr.e_shnum; i++) {
 567
 568                 if (processed_sec[i])
 569                         continue;
 570
 571                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
 572                         continue;
 573
 574                 if (memcmp(shname, "kprobe/", 7) == 0 ||
 575                     memcmp(shname, "kretprobe/", 10) == 0 ||
 576                     memcmp(shname, "tracepoint/", 11) == 0 ||
 577                     memcmp(shname, "xdp", 3) == 0 ||
 578                     memcmp(shname, "perf_event", 10) == 0 ||
 579                     memcmp(shname, "socket", 6) == 0 ||
 580                     memcmp(shname, "cgroup/", 7) == 0 ||
 581                     memcmp(shname, "sockops", 7) == 0 ||
 582                     memcmp(shname, "sk_skb", 6) == 0) {
 583                         ret = load_and_attach(shname, data->d_buf,
 584                                               data->d_size);
 585                         if (ret != 0)
 586                                 goto done;
 587                 }
 588         }
 589
 590         ret = 0;
 591 done:
 592         close(fd);
 593         return ret;
 594 }
 595
 596 int load_bpf_file(char *path)
 597 {
 598         return do_load_bpf_file(path, NULL);
 599 }
 600
 601 int load_bpf_file_fixup_map(const char *path, fixup_map_cb fixup_map)
 602 {
 603         return do_load_bpf_file(path, fixup_map);
 604 }
 605
 606 void read_trace_pipe(void)
 607 {
 608         int trace_fd;
 609
 610         trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
 611         if (trace_fd < 0)
 612                 return;
 613
 614         while (1) {
 615                 static char buf[4096];
 616                 ssize_t sz;
 617
 618                 sz = read(trace_fd, buf, sizeof(buf));
 619                 if (sz > 0) {
 620                         buf[sz] = 0;
 621                         puts(buf);
 622                 }
 623         }
 624 }
 625
 626 #define MAX_SYMS 300000
 627 static struct ksym syms[MAX_SYMS];
 628 static int sym_cnt;
 629
 630 static int ksym_cmp(const void *p1, const void *p2)
 631 {
 632         return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
 633 }
 634
 635 int load_kallsyms(void)
 636 {
 637         FILE *f = fopen("/proc/kallsyms", "r");
 638         char func[256], buf[256];
 639         char symbol;
 640         void *addr;
 641         int i = 0;
 642
 643         if (!f)
 644                 return -ENOENT;
 645
 646         while (!feof(f)) {
 647                 if (!fgets(buf, sizeof(buf), f))
 648                         break;
 649                 if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
 650                         break;
 651                 if (!addr)
 652                         continue;
 653                 syms[i].addr = (long) addr;
 654                 syms[i].name = strdup(func);
 655                 i++;
 656         }
 657         sym_cnt = i;
 658         qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
 659         return 0;
 660 }
 661
 662 struct ksym *ksym_search(long key)
 663 {
 664         int start = 0, end = sym_cnt;
 665         int result;
 666
 667         while (start < end) {
 668                 size_t mid = start + (end - start) / 2;
 669
 670                 result = key - syms[mid].addr;
 671                 if (result < 0)
 672                         end = mid;
 673                 else if (result > 0)
 674                         start = mid + 1;
 675                 else
 676                         return &syms[mid];
 677         }
 678
 679         if (start >= 1 && syms[start - 1].addr < key &&
 680             key < syms[start].addr)
 681                 /* valid ksym */
 682                 return &syms[start - 1];
 683
 684         /* out of range. return _stext */
 685         return &syms[0];
 686 }
 687
 688 int set_link_xdp_fd(int ifindex, int fd, __u32 flags)
 689 {
 690         struct sockaddr_nl sa;
 691         int sock, seq = 0, len, ret = -1;
 692         char buf[4096];
 693         struct nlattr *nla, *nla_xdp;
 694         struct {
 695                 struct nlmsghdr  nh;
 696                 struct ifinfomsg ifinfo;
 697                 char             attrbuf[64];
 698         } req;
 699         struct nlmsghdr *nh;
 700         struct nlmsgerr *err;
 701
 702         memset(&sa, 0, sizeof(sa));
 703         sa.nl_family = AF_NETLINK;
 704
 705         sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
 706         if (sock < 0) {
 707                 printf("open netlink socket: %s\n", strerror(errno));
 708                 return -1;
 709         }
 710
 711         if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
 712                 printf("bind to netlink: %s\n", strerror(errno));
 713                 goto cleanup;
 714         }
 715
 716         memset(&req, 0, sizeof(req));
 717         req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
 718         req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
 719         req.nh.nlmsg_type = RTM_SETLINK;
 720         req.nh.nlmsg_pid = 0;
 721         req.nh.nlmsg_seq = ++seq;
 722         req.ifinfo.ifi_family = AF_UNSPEC;
 723         req.ifinfo.ifi_index = ifindex;
 724
 725         /* started nested attribute for XDP */
 726         nla = (struct nlattr *)(((char *)&req)
 727                                 + NLMSG_ALIGN(req.nh.nlmsg_len));
 728         nla->nla_type = NLA_F_NESTED | 43/*IFLA_XDP*/;
 729         nla->nla_len = NLA_HDRLEN;
 730
 731         /* add XDP fd */
 732         nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
 733         nla_xdp->nla_type = 1/*IFLA_XDP_FD*/;
 734         nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
 735         memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
 736         nla->nla_len += nla_xdp->nla_len;
 737
 738         /* if user passed in any flags, add those too */
 739         if (flags) {
 740                 nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
 741                 nla_xdp->nla_type = 3/*IFLA_XDP_FLAGS*/;
 742                 nla_xdp->nla_len = NLA_HDRLEN + sizeof(flags);
 743                 memcpy((char *)nla_xdp + NLA_HDRLEN, &flags, sizeof(flags));
 744                 nla->nla_len += nla_xdp->nla_len;
 745         }
 746
 747         req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
 748
 749         if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
 750                 printf("send to netlink: %s\n", strerror(errno));
 751                 goto cleanup;
 752         }
 753
 754         len = recv(sock, buf, sizeof(buf), 0);
 755         if (len < 0) {
 756                 printf("recv from netlink: %s\n", strerror(errno));
 757                 goto cleanup;
 758         }
 759
 760         for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
 761              nh = NLMSG_NEXT(nh, len)) {
 762                 if (nh->nlmsg_pid != getpid()) {
 763                         printf("Wrong pid %d, expected %d\n",
 764                                nh->nlmsg_pid, getpid());
 765                         goto cleanup;
 766                 }
 767                 if (nh->nlmsg_seq != seq) {
 768                         printf("Wrong seq %d, expected %d\n",
 769                                nh->nlmsg_seq, seq);
 770                         goto cleanup;
 771                 }
 772                 switch (nh->nlmsg_type) {
 773                 case NLMSG_ERROR:
 774                         err = (struct nlmsgerr *)NLMSG_DATA(nh);
 775                         if (!err->error)
 776                                 continue;
 777                         printf("nlmsg error %s\n", strerror(-err->error));
 778                         goto cleanup;
 779                 case NLMSG_DONE:
 780                         break;
 781                 }
 782         }
 783
 784         ret = 0;
 785
 786 cleanup:
 787         close(sock);
 788         return ret;
 789 }