src/common/lttng-elf.c

   1 /*
   2  * Copyright (C) 2015  Antoine Busque <abusque@efficios.com>
   3  * Copyright (C) 2017  Francis Deslauriers <francis.deslauriers@efficios.com>
   4  * Copyright (C) 2017  Erica Bugden <erica.bugden@efficios.com>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #include <common/compat/endian.h>
  22 #include <common/error.h>
  23 #include <common/lttng-elf.h>
  24 #include <common/macros.h>
  25 #include <common/readwrite.h>
  26 #include <fcntl.h>
  27 #include <stdbool.h>
  28 #include <stdint.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <sys/stat.h>
  32 #include <sys/types.h>
  33 #include <unistd.h>
  34
  35 #include <elf.h>
  36
  37 #define BUF_LEN 4096
  38 #define TEXT_SECTION_NAME       ".text"
  39 #define SYMBOL_TAB_SECTION_NAME ".symtab"
  40 #define STRING_TAB_SECTION_NAME ".strtab"
  41 #define DYNAMIC_SYMBOL_TAB_SECTION_NAME ".dynsym"
  42 #define DYNAMIC_STRING_TAB_SECTION_NAME ".dynstr"
  43 #define NOTE_STAPSDT_SECTION_NAME ".note.stapsdt"
  44 #define NOTE_STAPSDT_NAME "stapsdt"
  45 #define NOTE_STAPSDT_TYPE 3
  46
  47 #if BYTE_ORDER == LITTLE_ENDIAN
  48 #define NATIVE_ELF_ENDIANNESS ELFDATA2LSB
  49 #else
  50 #define NATIVE_ELF_ENDIANNESS ELFDATA2MSB
  51 #endif
  52
  53 #define next_4bytes_boundary(x) (typeof(x)) ((((uint64_t)x) + 3) & ~0x03)
  54
  55 #define bswap(x)                                \
  56         do {                                    \
  57                 switch (sizeof(x)) {            \
  58                 case 8:                         \
  59                         x = be64toh((uint64_t)x);               \
  60                         break;                  \
  61                 case 4:                         \
  62                         x = be32toh((uint32_t)x);               \
  63                         break;                  \
  64                 case 2:                         \
  65                         x = be16toh((uint16_t)x);               \
  66                         break;                  \
  67                 case 1:                         \
  68                         break;                  \
  69                 default:                        \
  70                         abort();                \
  71                 }                               \
  72         } while (0)
  73
  74 #define bswap_shdr(shdr)            \
  75         do {                                \
  76                 bswap((shdr).sh_name);      \
  77                 bswap((shdr).sh_type);      \
  78                 bswap((shdr).sh_flags);     \
  79                 bswap((shdr).sh_addr);      \
  80                 bswap((shdr).sh_offset);    \
  81                 bswap((shdr).sh_size);      \
  82                 bswap((shdr).sh_link);      \
  83                 bswap((shdr).sh_info);      \
  84                 bswap((shdr).sh_addralign); \
  85                 bswap((shdr).sh_entsize);   \
  86         } while (0)
  87
  88 #define bswap_ehdr(ehdr)                                \
  89         do {                                            \
  90                 bswap((ehdr).e_type);                   \
  91                 bswap((ehdr).e_machine);                \
  92                 bswap((ehdr).e_version);                \
  93                 bswap((ehdr).e_entry);                  \
  94                 bswap((ehdr).e_phoff);                  \
  95                 bswap((ehdr).e_shoff);                  \
  96                 bswap((ehdr).e_flags);                  \
  97                 bswap((ehdr).e_ehsize);                 \
  98                 bswap((ehdr).e_phentsize);              \
  99                 bswap((ehdr).e_phnum);                  \
 100                 bswap((ehdr).e_shentsize);              \
 101                 bswap((ehdr).e_shnum);                  \
 102                 bswap((ehdr).e_shstrndx);               \
 103         } while (0)
 104
 105 #define copy_shdr(src_shdr, dst_shdr)                                   \
 106         do {                                                            \
 107                 (dst_shdr).sh_name = (src_shdr).sh_name;                \
 108                 (dst_shdr).sh_type = (src_shdr).sh_type;                \
 109                 (dst_shdr).sh_flags = (src_shdr).sh_flags;              \
 110                 (dst_shdr).sh_addr = (src_shdr).sh_addr;                \
 111                 (dst_shdr).sh_offset = (src_shdr).sh_offset;            \
 112                 (dst_shdr).sh_size = (src_shdr).sh_size;                \
 113                 (dst_shdr).sh_link = (src_shdr).sh_link;                \
 114                 (dst_shdr).sh_info = (src_shdr).sh_info;                \
 115                 (dst_shdr).sh_addralign = (src_shdr).sh_addralign;      \
 116                 (dst_shdr).sh_entsize = (src_shdr).sh_entsize;          \
 117         } while (0)
 118
 119 #define copy_ehdr(src_ehdr, dst_ehdr)                                   \
 120         do {                                                            \
 121                 (dst_ehdr).e_type = (src_ehdr).e_type;                  \
 122                 (dst_ehdr).e_machine = (src_ehdr).e_machine;            \
 123                 (dst_ehdr).e_version = (src_ehdr).e_version;            \
 124                 (dst_ehdr).e_entry = (src_ehdr).e_entry;                \
 125                 (dst_ehdr).e_phoff = (src_ehdr).e_phoff;                \
 126                 (dst_ehdr).e_shoff = (src_ehdr).e_shoff;                \
 127                 (dst_ehdr).e_flags = (src_ehdr).e_flags;                \
 128                 (dst_ehdr).e_ehsize = (src_ehdr).e_ehsize;              \
 129                 (dst_ehdr).e_phentsize = (src_ehdr).e_phentsize;        \
 130                 (dst_ehdr).e_phnum = (src_ehdr).e_phnum;                \
 131                 (dst_ehdr).e_shentsize = (src_ehdr).e_shentsize;        \
 132                 (dst_ehdr).e_shnum = (src_ehdr).e_shnum;                \
 133                 (dst_ehdr).e_shstrndx = (src_ehdr).e_shstrndx;          \
 134         } while (0)
 135
 136 #define copy_sym(src_sym, dst_sym)                      \
 137         do {                                            \
 138                 dst_sym.st_name = src_sym.st_name;      \
 139                 dst_sym.st_info = src_sym.st_info;      \
 140                 dst_sym.st_other = src_sym.st_other;    \
 141                 dst_sym.st_shndx = src_sym.st_shndx;    \
 142                 dst_sym.st_value = src_sym.st_value;    \
 143                 dst_sym.st_size = src_sym.st_size;      \
 144         } while (0)
 145
 146 /* Both 32bit and 64bit use the same 1 byte field for type. (See elf.h) */
 147 #define ELF_ST_TYPE(val) ELF32_ST_TYPE(val)
 148
 149 struct lttng_elf_ehdr {
 150         uint16_t e_type;
 151         uint16_t e_machine;
 152         uint32_t e_version;
 153         uint64_t e_entry;
 154         uint64_t e_phoff;
 155         uint64_t e_shoff;
 156         uint32_t e_flags;
 157         uint16_t e_ehsize;
 158         uint16_t e_phentsize;
 159         uint16_t e_phnum;
 160         uint16_t e_shentsize;
 161         uint16_t e_shnum;
 162         uint16_t e_shstrndx;
 163 };
 164
 165 struct lttng_elf_shdr {
 166         uint32_t sh_name;
 167         uint32_t sh_type;
 168         uint64_t sh_flags;
 169         uint64_t sh_addr;
 170         uint64_t sh_offset;
 171         uint64_t sh_size;
 172         uint32_t sh_link;
 173         uint32_t sh_info;
 174         uint64_t sh_addralign;
 175         uint64_t sh_entsize;
 176 };
 177
 178 /*
 179  * This struct can hold both 32bit and 64bit symbol description. It's used with
 180  * the copy_sym() macro. Using this abstraction, we can use the same code for
 181  * both bitness.
 182  */
 183 struct lttng_elf_sym {
 184         uint32_t st_name;
 185         uint8_t  st_info;
 186         uint8_t  st_other;
 187         uint16_t st_shndx;
 188         uint64_t st_value;
 189         uint64_t st_size;
 190 };
 191
 192 struct lttng_elf {
 193         int fd;
 194         uint8_t bitness;
 195         uint8_t endianness;
 196         /* Offset in bytes to start of section names string table. */
 197         off_t section_names_offset;
 198         /* Size in bytes of section names string table. */
 199         size_t section_names_size;
 200         struct lttng_elf_ehdr *ehdr;
 201 };
 202
 203 static inline
 204 int is_elf_32_bit(struct lttng_elf *elf)
 205 {
 206         return elf->bitness == ELFCLASS32;
 207 }
 208
 209 static inline
 210 int is_elf_native_endian(struct lttng_elf *elf)
 211 {
 212         return elf->endianness == NATIVE_ELF_ENDIANNESS;
 213 }
 214
 215 static
 216 int populate_section_header(struct lttng_elf * elf, struct lttng_elf_shdr *shdr,
 217                 uint32_t index)
 218 {
 219         int ret = 0;
 220         off_t offset;
 221
 222         /* Compute the offset of the section in the file */
 223         offset = (off_t) elf->ehdr->e_shoff
 224                         + (off_t) index * elf->ehdr->e_shentsize;
 225
 226         if (lseek(elf->fd, offset, SEEK_SET) < 0) {
 227                 PERROR("Error seeking to the beginning of ELF section header");
 228                 ret = -1;
 229                 goto error;
 230         }
 231
 232         if (is_elf_32_bit(elf)) {
 233                 Elf32_Shdr elf_shdr;
 234
 235                 if (lttng_read(elf->fd, &elf_shdr, sizeof(elf_shdr)) < sizeof(elf_shdr)) {
 236                         PERROR("Error reading ELF section header");
 237                         ret = -1;
 238                         goto error;
 239                 }
 240                 if (!is_elf_native_endian(elf)) {
 241                         bswap_shdr(elf_shdr);
 242                 }
 243                 copy_shdr(elf_shdr, *shdr);
 244         } else {
 245                 Elf64_Shdr elf_shdr;
 246
 247                 if (lttng_read(elf->fd, &elf_shdr, sizeof(elf_shdr)) < sizeof(elf_shdr)) {
 248                         PERROR("Error reading ELF section header");
 249                         ret = -1;
 250                         goto error;
 251                 }
 252                 if (!is_elf_native_endian(elf)) {
 253                         bswap_shdr(elf_shdr);
 254                 }
 255                 copy_shdr(elf_shdr, *shdr);
 256         }
 257
 258 error:
 259         return ret;
 260 }
 261
 262 static
 263 int populate_elf_header(struct lttng_elf *elf)
 264 {
 265         int ret = 0;
 266
 267         /*
 268          * Move the read pointer back to the beginning to read the full header
 269          * and copy it in our structure.
 270          */
 271         if (lseek(elf->fd, 0, SEEK_SET) < 0) {
 272                 PERROR("Error seeking to the beginning of the file");
 273                 ret = -1;
 274                 goto error;
 275         }
 276
 277         /*
 278          * Use macros to set fields in the ELF header struct for both 32bit and
 279          * 64bit.
 280          */
 281         if (is_elf_32_bit(elf)) {
 282                 Elf32_Ehdr elf_ehdr;
 283
 284                 if (lttng_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr)) < sizeof(elf_ehdr)) {
 285                         ret = -1;
 286                         goto error;
 287                 }
 288                 if (!is_elf_native_endian(elf)) {
 289                         bswap_ehdr(elf_ehdr);
 290                 }
 291                 copy_ehdr(elf_ehdr, *(elf->ehdr));
 292         } else {
 293                 Elf64_Ehdr elf_ehdr;
 294
 295                 if (lttng_read(elf->fd, &elf_ehdr, sizeof(elf_ehdr)) < sizeof(elf_ehdr)) {
 296                         ret = -1;
 297                         goto error;
 298                 }
 299                 if (!is_elf_native_endian(elf)) {
 300                         bswap_ehdr(elf_ehdr);
 301                 }
 302                 copy_ehdr(elf_ehdr, *(elf->ehdr));
 303         }
 304 error:
 305         return ret;
 306 }
 307
 308 /*
 309  * Retrieve the nth (where n is the `index` argument) shdr (section
 310  * header) from the given elf instance.
 311  *
 312  * 0 is returned on succes, -1 on failure.
 313  */
 314 static
 315 int lttng_elf_get_section_hdr(struct lttng_elf *elf,
 316                 uint16_t index, struct lttng_elf_shdr *out_header)
 317 {
 318         int ret = 0;
 319
 320         if (!elf) {
 321                 ret = -1;
 322                 goto error;
 323         }
 324
 325         if (index >= elf->ehdr->e_shnum) {
 326                 ret = -1;
 327                 goto error;
 328         }
 329
 330         ret = populate_section_header(elf, out_header, index);
 331         if (ret) {
 332                 DBG("Error populating section header.");
 333                 goto error;
 334         }
 335
 336 error:
 337         return ret;
 338 }
 339
 340 /*
 341  * Lookup a section's name from a given offset (usually from an shdr's
 342  * sh_name value) in bytes relative to the beginning of the section
 343  * names string table.
 344  *
 345  * If no name is found, NULL is returned.
 346  */
 347 static
 348 char *lttng_elf_get_section_name(struct lttng_elf *elf, off_t offset)
 349 {
 350         char *name = NULL;
 351         size_t name_length = 0, to_read;        /* name_length does not include \0 */
 352
 353         if (!elf) {
 354                 goto error;
 355         }
 356
 357         if (offset >= elf->section_names_size) {
 358                 goto error;
 359         }
 360
 361         if (lseek(elf->fd, elf->section_names_offset + offset, SEEK_SET) < 0) {
 362                 PERROR("Error seeking to the beginning of ELF string table section");
 363                 goto error;
 364         }
 365
 366         to_read = elf->section_names_size - offset;
 367
 368         /* Find first \0 after or at current location, remember name_length. */
 369         for (;;) {
 370                 char buf[BUF_LEN];
 371                 ssize_t read_len;
 372                 size_t i;
 373
 374                 if (!to_read) {
 375                         goto error;
 376                 }
 377                 read_len = lttng_read(elf->fd, buf, min_t(size_t, BUF_LEN, to_read));
 378                 if (read_len <= 0) {
 379                         PERROR("Error reading ELF string table section");
 380                         goto error;
 381                 }
 382                 for (i = 0; i < read_len; i++) {
 383                         if (buf[i] == '\0') {
 384                                 name_length += i;
 385                                 goto end;
 386                         }
 387                 }
 388                 name_length += read_len;
 389                 to_read -= read_len;
 390         }
 391 end:
 392         /*
 393          * We found the length of the section name, now seek back to the
 394          * beginning of the name and copy it in the newly allocated buffer.
 395          */
 396         name = zmalloc(sizeof(char) * (name_length + 1));       /* + 1 for \0 */
 397         if (!name) {
 398                 PERROR("Error allocating ELF section name buffer");
 399                 goto error;
 400         }
 401         if (lseek(elf->fd, elf->section_names_offset + offset, SEEK_SET) < 0) {
 402                 PERROR("Error seeking to the offset of the ELF section name");
 403                 goto error;
 404         }
 405         if (lttng_read(elf->fd, name, name_length + 1) < name_length + 1) {
 406                 PERROR("Error reading the ELF section name");
 407                 goto error;
 408         }
 409
 410         return name;
 411
 412 error:
 413         free(name);
 414         return NULL;
 415 }
 416
 417 static
 418 int lttng_elf_validate_and_populate(struct lttng_elf *elf)
 419 {
 420         uint8_t version;
 421         uint8_t e_ident[EI_NIDENT];
 422         uint8_t *magic_number = NULL;
 423         int ret = 0;
 424
 425         if (elf->fd == -1) {
 426                 DBG("fd error");
 427                 ret = LTTNG_ERR_ELF_PARSING;
 428                 goto end;
 429         }
 430
 431         /*
 432          * First read the magic number, endianness and version to later populate
 433          * the ELF header with the correct endianness and bitness.
 434          * (see elf.h)
 435          */
 436
 437         if (lseek(elf->fd, 0, SEEK_SET) < 0) {
 438                 PERROR("Error seeking the beginning of ELF file");
 439                 ret = LTTNG_ERR_ELF_PARSING;
 440                 goto end;
 441         }
 442         ret = lttng_read(elf->fd, e_ident, EI_NIDENT);
 443         if (ret < EI_NIDENT) {
 444                 DBG("Error reading the ELF identification fields");
 445                 if (ret == -1) {
 446                         PERROR("Error reading the ELF identification fields");
 447                 }
 448                 ret = LTTNG_ERR_ELF_PARSING;
 449                 goto end;
 450         }
 451
 452         /*
 453          * Copy fields used to check that the target file is in fact a valid ELF
 454          * file.
 455          */
 456         elf->bitness = e_ident[EI_CLASS];
 457         elf->endianness = e_ident[EI_DATA];
 458         version = e_ident[EI_VERSION];
 459         magic_number = &e_ident[EI_MAG0];
 460
 461         /*
 462          * Check the magic number.
 463          */
 464         if (memcmp(magic_number, ELFMAG, SELFMAG) != 0) {
 465                 DBG("Error check ELF magic number.");
 466                 ret = LTTNG_ERR_ELF_PARSING;
 467                 goto end;
 468         }
 469
 470         /*
 471          * Check the bitness is either ELFCLASS32 or ELFCLASS64.
 472          */
 473         if (elf->bitness <= ELFCLASSNONE || elf->bitness >= ELFCLASSNUM) {
 474                 DBG("ELF class error.");
 475                 ret = LTTNG_ERR_ELF_PARSING;
 476                 goto end;
 477         }
 478
 479         /*
 480          * Check the endianness is either ELFDATA2LSB or ELFDATA2MSB.
 481          */
 482         if (elf->endianness <= ELFDATANONE || elf->endianness >= ELFDATANUM) {
 483                 DBG("ELF endianness error.");
 484                 ret = LTTNG_ERR_ELF_PARSING;
 485                 goto end;
 486         }
 487
 488         /*
 489          * Check the version is ELF_CURRENT.
 490          */
 491         if (version <= EV_NONE || version >= EV_NUM) {
 492                 DBG("Wrong ELF version.");
 493                 ret = LTTNG_ERR_ELF_PARSING;
 494                 goto end;
 495         }
 496
 497         elf->ehdr = zmalloc(sizeof(struct lttng_elf_ehdr));
 498         if (!elf->ehdr) {
 499                 PERROR("Error allocation buffer for ELF header");
 500                 ret = LTTNG_ERR_NOMEM;
 501                 goto end;
 502         }
 503
 504         /*
 505          * Copy the content of the elf header.
 506          */
 507         ret = populate_elf_header(elf);
 508         if (ret) {
 509                 DBG("Error reading ELF header,");
 510                 goto free_elf_error;
 511         }
 512
 513         goto end;
 514
 515 free_elf_error:
 516         free(elf->ehdr);
 517         elf->ehdr = NULL;
 518 end:
 519         return ret;
 520 }
 521
 522 /*
 523  * Create an instance of lttng_elf for the ELF file located at
 524  * `path`.
 525  *
 526  * Return a pointer to the instance on success, NULL on failure.
 527  */
 528 static
 529 struct lttng_elf *lttng_elf_create(int fd)
 530 {
 531         struct lttng_elf_shdr section_names_shdr;
 532         struct lttng_elf *elf = NULL;
 533         int ret;
 534
 535         if (fd < 0) {
 536                 goto error;
 537         }
 538
 539         elf = zmalloc(sizeof(struct lttng_elf));
 540         if (!elf) {
 541                 PERROR("Error allocating struct lttng_elf");
 542                 goto error;
 543         }
 544
 545         elf->fd = dup(fd);
 546         if (elf->fd < 0) {
 547                 PERROR("Error duplicating file descriptor to binary");
 548                 goto error;
 549         }
 550
 551         ret = lttng_elf_validate_and_populate(elf);
 552         if (ret) {
 553                 goto error;
 554         }
 555
 556         ret = lttng_elf_get_section_hdr(
 557                         elf, elf->ehdr->e_shstrndx, &section_names_shdr);
 558         if (ret) {
 559                 goto error;
 560         }
 561
 562         elf->section_names_offset = section_names_shdr.sh_offset;
 563         elf->section_names_size = section_names_shdr.sh_size;
 564         return elf;
 565
 566 error:
 567         if (elf) {
 568                 if (elf->ehdr) {
 569                         free(elf->ehdr);
 570                 }
 571                 if (elf->fd >= 0) {
 572                         if (close(elf->fd)) {
 573                                 PERROR("Error closing file descriptor in error path");
 574                                 abort();
 575                         }
 576                 }
 577                 free(elf);
 578         }
 579         return NULL;
 580 }
 581
 582 /*
 583  * Destroy the given lttng_elf instance.
 584  */
 585 static
 586 void lttng_elf_destroy(struct lttng_elf *elf)
 587 {
 588         if (!elf) {
 589                 return;
 590         }
 591
 592         free(elf->ehdr);
 593         if (close(elf->fd)) {
 594                 PERROR("Error closing file description in error path");
 595                 abort();
 596         }
 597         free(elf);
 598 }
 599
 600 static
 601 int lttng_elf_get_section_hdr_by_name(struct lttng_elf *elf,
 602                 const char *section_name, struct lttng_elf_shdr *section_hdr)
 603 {
 604         int i;
 605         char *curr_section_name;
 606
 607         for (i = 0; i < elf->ehdr->e_shnum; ++i) {
 608                 bool name_equal;
 609                 int ret = lttng_elf_get_section_hdr(elf, i, section_hdr);
 610
 611                 if (ret) {
 612                         break;
 613                 }
 614                 curr_section_name = lttng_elf_get_section_name(elf,
 615                                 section_hdr->sh_name);
 616                 if (!curr_section_name) {
 617                         continue;
 618                 }
 619                 name_equal = strcmp(curr_section_name, section_name) == 0;
 620                 free(curr_section_name);
 621                 if (name_equal) {
 622                         return 0;
 623                 }
 624         }
 625         return LTTNG_ERR_ELF_PARSING;
 626 }
 627
 628 static
 629 char *lttng_elf_get_section_data(struct lttng_elf *elf,
 630                 struct lttng_elf_shdr *shdr)
 631 {
 632         int ret;
 633         off_t section_offset;
 634         char *data;
 635
 636         if (!elf || !shdr) {
 637                 goto error;
 638         }
 639
 640         section_offset = shdr->sh_offset;
 641         if (lseek(elf->fd, section_offset, SEEK_SET) < 0) {
 642                 PERROR("Error seeking to section offset");
 643                 goto error;
 644         }
 645
 646         data = zmalloc(shdr->sh_size);
 647         if (!data) {
 648                 PERROR("Error allocating buffer for ELF section data");
 649                 goto error;
 650         }
 651         ret = lttng_read(elf->fd, data, shdr->sh_size);
 652         if (ret == -1) {
 653                 PERROR("Error reading ELF section data");
 654                 goto free_error;
 655         }
 656
 657         return data;
 658
 659 free_error:
 660         free(data);
 661 error:
 662         return NULL;
 663 }
 664
 665 /*
 666  * Convert the virtual address in a binary's mapping to the offset of
 667  * the corresponding instruction in the binary file.
 668  * This function assumes the address is in the text section.
 669  *
 670  * Returns the offset on success or non-zero in case of failure.
 671  */
 672 static
 673 int lttng_elf_convert_addr_in_text_to_offset(struct lttng_elf *elf_handle,
 674                 size_t addr, uint64_t *offset)
 675 {
 676         int ret = 0;
 677         off_t text_section_offset;
 678         off_t text_section_addr_beg;
 679         off_t text_section_addr_end;
 680         off_t offset_in_section;
 681         struct lttng_elf_shdr text_section_hdr;
 682
 683         if (!elf_handle) {
 684                 DBG("Invalid ELF handle.");
 685                 ret = LTTNG_ERR_ELF_PARSING;
 686                 goto error;
 687         }
 688
 689         /* Get a pointer to the .text section header. */
 690         ret = lttng_elf_get_section_hdr_by_name(elf_handle,
 691                         TEXT_SECTION_NAME, &text_section_hdr);
 692         if (ret) {
 693                 DBG("Text section not found in binary.");
 694                 ret = LTTNG_ERR_ELF_PARSING;
 695                 goto error;
 696         }
 697
 698         text_section_offset = text_section_hdr.sh_offset;
 699         text_section_addr_beg = text_section_hdr.sh_addr;
 700         text_section_addr_end =
 701                         text_section_addr_beg + text_section_hdr.sh_size;
 702
 703         /*
 704          * Verify that the address is within the .text section boundaries.
 705          */
 706         if (addr < text_section_addr_beg || addr > text_section_addr_end) {
 707                 DBG("Address found is outside of the .text section addr=0x%zx, "
 708                         ".text section=[0x%jd - 0x%jd].", addr, (intmax_t)text_section_addr_beg,
 709                         (intmax_t)text_section_addr_end);
 710                 ret = LTTNG_ERR_ELF_PARSING;
 711                 goto error;
 712         }
 713
 714         offset_in_section = addr - text_section_addr_beg;
 715
 716         /*
 717          * Add the target offset in the text section to the offset of this text
 718          * section from the beginning of the binary file.
 719          */
 720         *offset = text_section_offset + offset_in_section;
 721
 722 error:
 723         return ret;
 724 }
 725
 726 /*
 727  * Compute the offset of a symbol from the begining of the ELF binary.
 728  *
 729  * On success, returns 0 offset parameter is set to the computed value
 730  * On failure, returns -1.
 731  */
 732 int lttng_elf_get_symbol_offset(int fd, char *symbol, uint64_t *offset)
 733 {
 734         int ret = 0;
 735         int sym_found = 0;
 736         int sym_count = 0;
 737         int sym_idx = 0;
 738         uint64_t addr = 0;
 739         char *curr_sym_str = NULL;
 740         char *symbol_table_data = NULL;
 741         char *string_table_data = NULL;
 742         char *string_table_name = NULL;
 743         struct lttng_elf_shdr symtab_hdr;
 744         struct lttng_elf_shdr strtab_hdr;
 745         struct lttng_elf *elf = NULL;
 746
 747         if (!symbol || !offset ) {
 748                 ret = LTTNG_ERR_ELF_PARSING;
 749                 goto end;
 750         }
 751
 752         elf = lttng_elf_create(fd);
 753         if (!elf) {
 754                 ret = LTTNG_ERR_ELF_PARSING;
 755                 goto end;
 756         }
 757
 758         /*
 759          * The .symtab section might not exist on stripped binaries.
 760          * Try to get the symbol table section header first. If it's absent,
 761          * try to get the dynamic symbol table. All symbols in the dynamic
 762          * symbol tab are in the (normal) symbol table if it exists.
 763          */
 764         ret = lttng_elf_get_section_hdr_by_name(elf, SYMBOL_TAB_SECTION_NAME,
 765                         &symtab_hdr);
 766         if (ret) {
 767                 DBG("Cannot get ELF Symbol Table section. Trying to get ELF Dynamic Symbol Table section.");
 768                 /* Get the dynamic symbol table section header. */
 769                 ret = lttng_elf_get_section_hdr_by_name(elf, DYNAMIC_SYMBOL_TAB_SECTION_NAME,
 770                                 &symtab_hdr);
 771                 if (ret) {
 772                         DBG("Cannot get ELF Symbol Table nor Dynamic Symbol Table sections.");
 773                         ret = LTTNG_ERR_ELF_PARSING;
 774                         goto destroy_elf;
 775                 }
 776                 string_table_name = DYNAMIC_STRING_TAB_SECTION_NAME;
 777         } else {
 778                 string_table_name = STRING_TAB_SECTION_NAME;
 779         }
 780
 781         /* Get the data associated with the symbol table section. */
 782         symbol_table_data = lttng_elf_get_section_data(elf, &symtab_hdr);
 783         if (symbol_table_data == NULL) {
 784                 DBG("Cannot get ELF Symbol Table data.");
 785                 ret = LTTNG_ERR_ELF_PARSING;
 786                 goto destroy_elf;
 787         }
 788
 789         /* Get the string table section header. */
 790         ret = lttng_elf_get_section_hdr_by_name(elf, string_table_name,
 791                         &strtab_hdr);
 792         if (ret) {
 793                 DBG("Cannot get ELF string table section.");
 794                 goto free_symbol_table_data;
 795         }
 796
 797         /* Get the data associated with the string table section. */
 798         string_table_data = lttng_elf_get_section_data(elf, &strtab_hdr);
 799         if (string_table_data == NULL) {
 800                 DBG("Cannot get ELF string table section data.");
 801                 ret = LTTNG_ERR_ELF_PARSING;
 802                 goto free_symbol_table_data;
 803         }
 804
 805         /* Get the number of symbol in the table for the iteration. */
 806         sym_count = symtab_hdr.sh_size / symtab_hdr.sh_entsize;
 807
 808         /* Loop over all symbol. */
 809         for (sym_idx = 0; sym_idx < sym_count; sym_idx++) {
 810                 struct lttng_elf_sym curr_sym;
 811
 812                 /* Get the symbol at the current index. */
 813                 if (is_elf_32_bit(elf)) {
 814                         Elf32_Sym tmp = ((Elf32_Sym *) symbol_table_data)[sym_idx];
 815                         copy_sym(tmp, curr_sym);
 816                 } else {
 817                         Elf64_Sym tmp = ((Elf64_Sym *) symbol_table_data)[sym_idx];
 818                         copy_sym(tmp, curr_sym);
 819                 }
 820
 821                 /*
 822                  * If the st_name field is zero, there is no string name for
 823                  * this symbol; skip to the next symbol.
 824                  */
 825                 if (curr_sym.st_name == 0) {
 826                         continue;
 827                 }
 828
 829                 /*
 830                  * Use the st_name field in the lttng_elf_sym struct to get offset of
 831                  * the symbol's name from the beginning of the string table.
 832                  */
 833                 curr_sym_str = string_table_data + curr_sym.st_name;
 834
 835                 /*
 836                  * If the current symbol is not a function; skip to the next symbol.
 837                  */
 838                 if (ELF_ST_TYPE(curr_sym.st_info) != STT_FUNC) {
 839                         continue;
 840                 }
 841
 842                 /*
 843                  * Compare with the search symbol. If there is a match set the address
 844                  * output parameter and return success.
 845                  */
 846                 if (strcmp(symbol, curr_sym_str) == 0 ) {
 847                         sym_found = 1;
 848                         addr = curr_sym.st_value;
 849                         break;
 850                 }
 851         }
 852
 853         if (!sym_found) {
 854                 DBG("Symbol not found.");
 855                 ret = LTTNG_ERR_ELF_PARSING;
 856                 goto free_string_table_data;
 857         }
 858
 859         /*
 860          * Use the virtual address of the symbol to compute the offset of this
 861          * symbol from the beginning of the executable file.
 862          */
 863         ret = lttng_elf_convert_addr_in_text_to_offset(elf, addr, offset);
 864         if (ret) {
 865                 DBG("Cannot convert addr to offset.");
 866                 goto free_string_table_data;
 867         }
 868
 869
 870 free_string_table_data:
 871         free(string_table_data);
 872 free_symbol_table_data:
 873         free(symbol_table_data);
 874 destroy_elf:
 875         lttng_elf_destroy(elf);
 876 end:
 877         return ret;
 878 }
 879
 880 /*
 881  * Compute the offsets of SDT probes from the begining of the ELF binary.
 882  *
 883  * On success, returns 0 and the nb_probes parameter is set to the number of
 884  * offsets found and the offsets parameter points to an array of offsets where
 885  * the SDT probes are.
 886  * On failure, returns -1.
 887  */
 888 int lttng_elf_get_sdt_probe_offsets(int fd, const char *provider_name,
 889                 const char *probe_name, uint64_t **offsets, uint32_t *nb_probes)
 890 {
 891         int ret = 0, nb_match = 0;
 892         struct lttng_elf_shdr stap_note_section_hdr;
 893         struct lttng_elf *elf = NULL;
 894         char *stap_note_section_data = NULL;
 895         char *curr_note_section_begin, *curr_data_ptr, *curr_probe, *curr_provider;
 896         char *next_note_ptr;
 897         uint32_t name_size, desc_size, note_type;
 898         uint64_t curr_probe_location, curr_probe_offset, curr_semaphore_location;
 899         uint64_t *probe_locs = NULL, *new_probe_locs = NULL;
 900
 901         if (!provider_name || !probe_name || !nb_probes || !offsets) {
 902                 DBG("Invalid arguments.");
 903                 ret = LTTNG_ERR_ELF_PARSING;
 904                 goto error;
 905         }
 906
 907         elf = lttng_elf_create(fd);
 908         if (!elf) {
 909                 DBG("Error allocation ELF.");
 910                 ret = LTTNG_ERR_ELF_PARSING;
 911                 goto error;
 912         }
 913
 914         /* Get the stap note section header. */
 915         ret = lttng_elf_get_section_hdr_by_name(elf, NOTE_STAPSDT_SECTION_NAME,
 916                         &stap_note_section_hdr);
 917         if (ret) {
 918                 DBG("Cannot get ELF stap note section.");
 919                 goto destroy_elf_error;
 920         }
 921
 922         /* Get the data associated with the stap note section. */
 923         stap_note_section_data =
 924                         lttng_elf_get_section_data(elf, &stap_note_section_hdr);
 925         if (stap_note_section_data == NULL) {
 926                 DBG("Cannot get ELF stap note section data.");
 927                 ret = LTTNG_ERR_ELF_PARSING;
 928                 goto destroy_elf_error;
 929         }
 930
 931         next_note_ptr = stap_note_section_data;
 932         curr_note_section_begin = stap_note_section_data;
 933
 934         *offsets = NULL;
 935         while (1) {
 936                 curr_data_ptr = next_note_ptr;
 937                 /* Check if we have reached the end of the note section. */
 938                 if (curr_data_ptr >=
 939                                 curr_note_section_begin +
 940                                                 stap_note_section_hdr.sh_size) {
 941                         *nb_probes = nb_match;
 942                         *offsets = probe_locs;
 943                         ret = 0;
 944                         break;
 945                 }
 946                 /* Get name size field. */
 947                 name_size = next_4bytes_boundary(*(uint32_t*) curr_data_ptr);
 948                 curr_data_ptr += sizeof(uint32_t);
 949
 950                 /* Sanity check; a zero name_size is reserved. */
 951                 if (name_size == 0) {
 952                         DBG("Invalid name size field in SDT probe descriptions"
 953                                 "section.");
 954                         ret = -1;
 955                         goto realloc_error;
 956                 }
 957
 958                 /* Get description size field. */
 959                 desc_size = next_4bytes_boundary(*(uint32_t*) curr_data_ptr);
 960                 curr_data_ptr += sizeof(uint32_t);
 961
 962                 /* Get type field. */
 963                 note_type = *(uint32_t *) curr_data_ptr;
 964                 curr_data_ptr += sizeof(uint32_t);
 965
 966                 /*
 967                  * Move the pointer to the next note to be ready for the next
 968                  * iteration. The current note is made of 3 unsigned 32bit
 969                  * integers (name size, descriptor size and note type), the
 970                  * name and the descriptor. To move to the next note, we move
 971                  * the pointer according to those values.
 972                  */
 973                 next_note_ptr = next_note_ptr +
 974                         (3 * sizeof(uint32_t)) + desc_size + name_size;
 975
 976                 /*
 977                  * Move ptr to the end of the name string (we don't need it)
 978                  * and go to the next 4 byte alignement.
 979                  */
 980                 if (note_type != NOTE_STAPSDT_TYPE ||
 981                         strncmp(curr_data_ptr, NOTE_STAPSDT_NAME, name_size) != 0) {
 982                         continue;
 983                 }
 984
 985                 curr_data_ptr += name_size;
 986
 987                 /* Get probe location.  */
 988                 curr_probe_location = *(uint64_t *) curr_data_ptr;
 989                 curr_data_ptr += sizeof(uint64_t);
 990
 991                 /* Pass over the base. Not needed. */
 992                 curr_data_ptr += sizeof(uint64_t);
 993
 994                 /* Get semaphore location. */
 995                 curr_semaphore_location = *(uint64_t *) curr_data_ptr;
 996                 curr_data_ptr += sizeof(uint64_t);
 997                 /* Get provider name. */
 998                 curr_provider = curr_data_ptr;
 999                 curr_data_ptr += strlen(curr_provider) + 1;
1000
1001                 /* Get probe name. */
1002                 curr_probe = curr_data_ptr;
1003
1004                 /* Check if the provider and probe name match */
1005                 if (strcmp(provider_name, curr_provider) == 0 &&
1006                                 strcmp(probe_name, curr_probe) == 0) {
1007                         int new_size;
1008
1009                         /*
1010                          * We currently don't support SDT probes with semaphores. Return
1011                          * success as we found a matching probe but it's guarded by a
1012                          * semaphore.
1013                          */
1014                         if (curr_semaphore_location != 0) {
1015                                 ret = LTTNG_ERR_SDT_PROBE_SEMAPHORE;
1016                                 goto realloc_error;
1017                         }
1018
1019                         new_size = (++nb_match) * sizeof(uint64_t);
1020
1021                         /*
1022                          * Found a match with not semaphore, we need to copy the
1023                          * probe_location to the output parameter.
1024                          */
1025                         new_probe_locs = realloc(probe_locs, new_size);
1026                         if (!new_probe_locs) {
1027                                 /* Error allocating a larger buffer */
1028                                 DBG("Allocation error in SDT.");
1029                                 ret = LTTNG_ERR_NOMEM;
1030                                 goto realloc_error;
1031                         }
1032                         probe_locs = new_probe_locs;
1033                         new_probe_locs = NULL;
1034
1035                         /*
1036                          * Use the virtual address of the probe to compute the offset of
1037                          * this probe from the beginning of the executable file.
1038                          */
1039                         ret = lttng_elf_convert_addr_in_text_to_offset(elf,
1040                                         curr_probe_location, &curr_probe_offset);
1041                         if (ret) {
1042                                 DBG("Conversion error in SDT.");
1043                                 goto realloc_error;
1044                         }
1045
1046                         probe_locs[nb_match - 1] = curr_probe_offset;
1047                 }
1048         }
1049
1050 end:
1051         free(stap_note_section_data);
1052 destroy_elf_error:
1053         lttng_elf_destroy(elf);
1054 error:
1055         return ret;
1056 realloc_error:
1057         free(probe_locs);
1058         goto end;
1059 }