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