| 1 | /* Copyright 2013-2017 Free Software Foundation, Inc. |
| 2 | This program is free software; you can redistribute it and/or modify |
| 3 | it under the terms of the GNU General Public License as published by |
| 4 | the Free Software Foundation; either version 3 of the License, or |
| 5 | (at your option) any later version. |
| 6 | |
| 7 | This program is distributed in the hope that it will be useful, |
| 8 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 9 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 10 | GNU General Public License for more details. |
| 11 | |
| 12 | You should have received a copy of the GNU General Public License |
| 13 | along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 14 | */ |
| 15 | |
| 16 | #include <unistd.h> |
| 17 | #include <fcntl.h> |
| 18 | #include <limits.h> |
| 19 | #include <stdio.h> |
| 20 | #include <stdlib.h> |
| 21 | #include <string.h> |
| 22 | #include <sys/mman.h> |
| 23 | |
| 24 | #include "sym-file-loader.h" |
| 25 | |
| 26 | #include <inttypes.h> |
| 27 | #include <ansidecl.h> |
| 28 | #include <elf/common.h> |
| 29 | #include <elf/external.h> |
| 30 | |
| 31 | #ifdef TARGET_LP64 |
| 32 | |
| 33 | typedef Elf64_External_Phdr Elf_External_Phdr; |
| 34 | typedef Elf64_External_Ehdr Elf_External_Ehdr; |
| 35 | typedef Elf64_External_Shdr Elf_External_Shdr; |
| 36 | typedef Elf64_External_Sym Elf_External_Sym; |
| 37 | typedef uint64_t Elf_Addr; |
| 38 | |
| 39 | #elif defined TARGET_ILP32 |
| 40 | |
| 41 | typedef Elf32_External_Phdr Elf_External_Phdr; |
| 42 | typedef Elf32_External_Ehdr Elf_External_Ehdr; |
| 43 | typedef Elf32_External_Shdr Elf_External_Shdr; |
| 44 | typedef Elf32_External_Sym Elf_External_Sym; |
| 45 | typedef uint32_t Elf_Addr; |
| 46 | |
| 47 | #endif |
| 48 | |
| 49 | #define GET(hdr, field) (\ |
| 50 | sizeof ((hdr)->field) == 1 ? (uint64_t) (hdr)->field[0] : \ |
| 51 | sizeof ((hdr)->field) == 2 ? (uint64_t) *(uint16_t *) (hdr)->field : \ |
| 52 | sizeof ((hdr)->field) == 4 ? (uint64_t) *(uint32_t *) (hdr)->field : \ |
| 53 | sizeof ((hdr)->field) == 8 ? *(uint64_t *) (hdr)->field : \ |
| 54 | *(uint64_t *) NULL) |
| 55 | |
| 56 | #define GETADDR(hdr, field) (\ |
| 57 | sizeof ((hdr)->field) == sizeof (Elf_Addr) ? *(Elf_Addr *) (hdr)->field : \ |
| 58 | *(Elf_Addr *) NULL) |
| 59 | |
| 60 | struct segment |
| 61 | { |
| 62 | uint8_t *mapped_addr; |
| 63 | size_t mapped_size; |
| 64 | Elf_External_Phdr *phdr; |
| 65 | struct segment *next; |
| 66 | }; |
| 67 | |
| 68 | struct library |
| 69 | { |
| 70 | int fd; |
| 71 | Elf_External_Ehdr *ehdr; |
| 72 | struct segment *segments; |
| 73 | }; |
| 74 | |
| 75 | static Elf_External_Shdr *find_shdr (Elf_External_Ehdr *ehdr, |
| 76 | const char *section); |
| 77 | static int translate_offset (uint64_t file_offset, struct segment *seg, |
| 78 | void **addr); |
| 79 | |
| 80 | #ifdef TARGET_LP64 |
| 81 | |
| 82 | uint8_t |
| 83 | elf_st_type (uint8_t st_info) |
| 84 | { |
| 85 | return ELF64_ST_TYPE (st_info); |
| 86 | } |
| 87 | |
| 88 | #elif defined TARGET_ILP32 |
| 89 | |
| 90 | uint8_t |
| 91 | elf_st_type (uint8_t st_info) |
| 92 | { |
| 93 | return ELF32_ST_TYPE (st_info); |
| 94 | } |
| 95 | |
| 96 | #endif |
| 97 | |
| 98 | /* Load a program segment. */ |
| 99 | |
| 100 | static struct segment * |
| 101 | load (uint8_t *addr, Elf_External_Phdr *phdr, struct segment *tail_seg) |
| 102 | { |
| 103 | struct segment *seg = NULL; |
| 104 | uint8_t *mapped_addr = NULL; |
| 105 | size_t mapped_size = 0; |
| 106 | void *from = NULL; |
| 107 | void *to = NULL; |
| 108 | |
| 109 | /* For the sake of simplicity all operations are permitted. */ |
| 110 | unsigned perm = PROT_READ | PROT_WRITE | PROT_EXEC; |
| 111 | |
| 112 | mapped_addr = (uint8_t *) mmap ((void *) GETADDR (phdr, p_vaddr), |
| 113 | GET (phdr, p_memsz), perm, |
| 114 | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0); |
| 115 | mapped_size = GET (phdr, p_memsz); |
| 116 | |
| 117 | from = (void *) (addr + GET (phdr, p_offset)); |
| 118 | to = (void *) mapped_addr; |
| 119 | |
| 120 | memcpy (to, from, GET (phdr, p_filesz)); |
| 121 | |
| 122 | seg = (struct segment *) malloc (sizeof (struct segment)); |
| 123 | |
| 124 | if (seg == 0) |
| 125 | return 0; |
| 126 | |
| 127 | seg->mapped_addr = mapped_addr; |
| 128 | seg->mapped_size = mapped_size; |
| 129 | seg->phdr = phdr; |
| 130 | seg->next = 0; |
| 131 | |
| 132 | if (tail_seg != 0) |
| 133 | tail_seg->next = seg; |
| 134 | |
| 135 | return seg; |
| 136 | } |
| 137 | |
| 138 | #ifdef __linux__ |
| 139 | # define SELF_LINK "/proc/self/exe" |
| 140 | #elif defined NETBSD |
| 141 | # define SELF_LINK "/proc/curproc/exe" |
| 142 | #elif defined __OpenBSD__ || defined __FreeBSD__ || defined __DragonFly__ |
| 143 | # define SELF_LINK "/proc/curproc/file" |
| 144 | #elif defined SunOS |
| 145 | # define SELF_LINK "/proc/self/path/a.out" |
| 146 | #endif |
| 147 | |
| 148 | /* Like RPATH=$ORIGIN, return the dirname of the current |
| 149 | executable. */ |
| 150 | |
| 151 | static const char * |
| 152 | get_origin (void) |
| 153 | { |
| 154 | static char self_path[PATH_MAX]; |
| 155 | static ssize_t self_path_len; |
| 156 | |
| 157 | if (self_path_len == 0) |
| 158 | { |
| 159 | #ifdef SELF_LINK |
| 160 | self_path_len = readlink (SELF_LINK, self_path, PATH_MAX - 1); |
| 161 | if (self_path_len != -1) |
| 162 | { |
| 163 | char *dirsep; |
| 164 | |
| 165 | self_path[self_path_len] = '\0'; |
| 166 | dirsep = strrchr (self_path, '/'); |
| 167 | *dirsep = '\0'; |
| 168 | } |
| 169 | #else |
| 170 | self_path_len = -1; |
| 171 | #endif |
| 172 | } |
| 173 | |
| 174 | if (self_path_len == -1) |
| 175 | return NULL; |
| 176 | else |
| 177 | return self_path; |
| 178 | } |
| 179 | |
| 180 | /* Unload/unmap a segment. */ |
| 181 | |
| 182 | static void |
| 183 | unload (struct segment *seg) |
| 184 | { |
| 185 | munmap (seg->mapped_addr, seg->mapped_size); |
| 186 | free (seg); |
| 187 | } |
| 188 | |
| 189 | void |
| 190 | unload_shlib (struct library *lib) |
| 191 | { |
| 192 | struct segment *seg, *next_seg; |
| 193 | |
| 194 | for (seg = lib->segments; seg != NULL; seg = next_seg) |
| 195 | { |
| 196 | next_seg = seg->next; |
| 197 | unload (seg); |
| 198 | } |
| 199 | |
| 200 | close (lib->fd); |
| 201 | free (lib); |
| 202 | } |
| 203 | |
| 204 | /* Mini shared library loader. No reallocation |
| 205 | is performed for the sake of simplicity. */ |
| 206 | |
| 207 | struct library * |
| 208 | load_shlib (const char *file) |
| 209 | { |
| 210 | struct library *lib; |
| 211 | uint64_t i; |
| 212 | int fd = -1; |
| 213 | off_t fsize; |
| 214 | uint8_t *addr; |
| 215 | Elf_External_Ehdr *ehdr; |
| 216 | Elf_External_Phdr *phdr; |
| 217 | struct segment *head_seg = NULL; |
| 218 | struct segment *tail_seg = NULL; |
| 219 | const char *origin; |
| 220 | char *path; |
| 221 | |
| 222 | /* Map the lib in memory for reading. |
| 223 | |
| 224 | If the file name is relative, try looking it up relative to the |
| 225 | main executable's path. I.e., emulate RPATH=$ORIGIN. */ |
| 226 | if (file[0] != '/') |
| 227 | { |
| 228 | origin = get_origin (); |
| 229 | if (origin == NULL) |
| 230 | { |
| 231 | fprintf (stderr, "get_origin not implemented."); |
| 232 | return NULL; |
| 233 | } |
| 234 | |
| 235 | path = alloca (strlen (origin) + 1 + strlen (file) + 1); |
| 236 | sprintf (path, "%s/%s", origin, file); |
| 237 | fd = open (path, O_RDONLY); |
| 238 | } |
| 239 | |
| 240 | if (fd < 0) |
| 241 | fd = open (file, O_RDONLY); |
| 242 | |
| 243 | if (fd < 0) |
| 244 | { |
| 245 | perror ("fopen failed."); |
| 246 | return NULL; |
| 247 | } |
| 248 | |
| 249 | fsize = lseek (fd, 0, SEEK_END); |
| 250 | |
| 251 | if (fsize < 0) |
| 252 | { |
| 253 | perror ("lseek failed."); |
| 254 | return NULL; |
| 255 | } |
| 256 | |
| 257 | addr = (uint8_t *) mmap (NULL, fsize, PROT_READ, MAP_PRIVATE, fd, 0); |
| 258 | if (addr == (uint8_t *) -1) |
| 259 | { |
| 260 | perror ("mmap failed."); |
| 261 | return NULL; |
| 262 | } |
| 263 | |
| 264 | /* Check if the lib is an ELF file. */ |
| 265 | ehdr = (Elf_External_Ehdr *) addr; |
| 266 | if (ehdr->e_ident[EI_MAG0] != ELFMAG0 |
| 267 | || ehdr->e_ident[EI_MAG1] != ELFMAG1 |
| 268 | || ehdr->e_ident[EI_MAG2] != ELFMAG2 |
| 269 | || ehdr->e_ident[EI_MAG3] != ELFMAG3) |
| 270 | { |
| 271 | printf ("Not an ELF file: %x\n", ehdr->e_ident[EI_MAG0]); |
| 272 | return NULL; |
| 273 | } |
| 274 | |
| 275 | if (ehdr->e_ident[EI_CLASS] == ELFCLASS32) |
| 276 | { |
| 277 | if (sizeof (void *) != 4) |
| 278 | { |
| 279 | printf ("Architecture mismatch."); |
| 280 | return NULL; |
| 281 | } |
| 282 | } |
| 283 | else if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) |
| 284 | { |
| 285 | if (sizeof (void *) != 8) |
| 286 | { |
| 287 | printf ("Architecture mismatch."); |
| 288 | return NULL; |
| 289 | } |
| 290 | } |
| 291 | |
| 292 | lib = malloc (sizeof (struct library)); |
| 293 | if (lib == NULL) |
| 294 | { |
| 295 | printf ("malloc failed."); |
| 296 | return NULL; |
| 297 | } |
| 298 | |
| 299 | lib->fd = fd; |
| 300 | |
| 301 | /* Load the program segments. For the sake of simplicity |
| 302 | assume that no reallocation is needed. */ |
| 303 | phdr = (Elf_External_Phdr *) (addr + GET (ehdr, e_phoff)); |
| 304 | for (i = 0; i < GET (ehdr, e_phnum); i++, phdr++) |
| 305 | { |
| 306 | if (GET (phdr, p_type) == PT_LOAD) |
| 307 | { |
| 308 | struct segment *next_seg = load (addr, phdr, tail_seg); |
| 309 | if (next_seg == 0) |
| 310 | continue; |
| 311 | tail_seg = next_seg; |
| 312 | if (head_seg == 0) |
| 313 | head_seg = next_seg; |
| 314 | } |
| 315 | } |
| 316 | lib->ehdr = ehdr; |
| 317 | lib->segments = head_seg; |
| 318 | return lib; |
| 319 | } |
| 320 | |
| 321 | int |
| 322 | get_text_addr (struct library *lib, void **text_addr) |
| 323 | { |
| 324 | Elf_External_Shdr *text; |
| 325 | |
| 326 | /* Get the text section. */ |
| 327 | text = find_shdr (lib->ehdr, ".text"); |
| 328 | if (text == NULL) |
| 329 | return -1; |
| 330 | |
| 331 | if (translate_offset (GET (text, sh_offset), lib->segments, text_addr) |
| 332 | != 0) |
| 333 | return -1; |
| 334 | |
| 335 | return 0; |
| 336 | } |
| 337 | |
| 338 | /* Return the section-header table. */ |
| 339 | |
| 340 | Elf_External_Shdr * |
| 341 | find_shdrtab (Elf_External_Ehdr *ehdr) |
| 342 | { |
| 343 | return (Elf_External_Shdr *) (((uint8_t *) ehdr) + GET (ehdr, e_shoff)); |
| 344 | } |
| 345 | |
| 346 | /* Return the string table of the section headers. */ |
| 347 | |
| 348 | const char * |
| 349 | find_shstrtab (Elf_External_Ehdr *ehdr, uint64_t *size) |
| 350 | { |
| 351 | const Elf_External_Shdr *shdr; |
| 352 | const Elf_External_Shdr *shstr; |
| 353 | |
| 354 | if (GET (ehdr, e_shnum) <= GET (ehdr, e_shstrndx)) |
| 355 | { |
| 356 | printf ("The index of the string table is corrupt."); |
| 357 | return NULL; |
| 358 | } |
| 359 | |
| 360 | shdr = find_shdrtab (ehdr); |
| 361 | |
| 362 | shstr = &shdr[GET (ehdr, e_shstrndx)]; |
| 363 | *size = GET (shstr, sh_size); |
| 364 | return ((const char *) ehdr) + GET (shstr, sh_offset); |
| 365 | } |
| 366 | |
| 367 | /* Return the string table named SECTION. */ |
| 368 | |
| 369 | const char * |
| 370 | find_strtab (Elf_External_Ehdr *ehdr, |
| 371 | const char *section, uint64_t *strtab_size) |
| 372 | { |
| 373 | uint64_t shstrtab_size = 0; |
| 374 | const char *shstrtab; |
| 375 | uint64_t i; |
| 376 | const Elf_External_Shdr *shdr = find_shdrtab (ehdr); |
| 377 | |
| 378 | /* Get the string table of the section headers. */ |
| 379 | shstrtab = find_shstrtab (ehdr, &shstrtab_size); |
| 380 | if (shstrtab == NULL) |
| 381 | return NULL; |
| 382 | |
| 383 | for (i = 0; i < GET (ehdr, e_shnum); i++) |
| 384 | { |
| 385 | uint64_t name = GET (shdr + i, sh_name); |
| 386 | if (GET (shdr + i, sh_type) == SHT_STRTAB && name <= shstrtab_size |
| 387 | && strcmp ((const char *) &shstrtab[name], section) == 0) |
| 388 | { |
| 389 | *strtab_size = GET (shdr + i, sh_size); |
| 390 | return ((const char *) ehdr) + GET (shdr + i, sh_offset); |
| 391 | } |
| 392 | |
| 393 | } |
| 394 | return NULL; |
| 395 | } |
| 396 | |
| 397 | /* Return the section header named SECTION. */ |
| 398 | |
| 399 | static Elf_External_Shdr * |
| 400 | find_shdr (Elf_External_Ehdr *ehdr, const char *section) |
| 401 | { |
| 402 | uint64_t shstrtab_size = 0; |
| 403 | const char *shstrtab; |
| 404 | uint64_t i; |
| 405 | |
| 406 | /* Get the string table of the section headers. */ |
| 407 | shstrtab = find_shstrtab (ehdr, &shstrtab_size); |
| 408 | if (shstrtab == NULL) |
| 409 | return NULL; |
| 410 | |
| 411 | Elf_External_Shdr *shdr = find_shdrtab (ehdr); |
| 412 | for (i = 0; i < GET (ehdr, e_shnum); i++) |
| 413 | { |
| 414 | uint64_t name = GET (shdr + i, sh_name); |
| 415 | if (name <= shstrtab_size) |
| 416 | { |
| 417 | if (strcmp ((const char *) &shstrtab[name], section) == 0) |
| 418 | return &shdr[i]; |
| 419 | } |
| 420 | |
| 421 | } |
| 422 | return NULL; |
| 423 | } |
| 424 | |
| 425 | /* Return the symbol table. */ |
| 426 | |
| 427 | static Elf_External_Sym * |
| 428 | find_symtab (Elf_External_Ehdr *ehdr, uint64_t *symtab_size) |
| 429 | { |
| 430 | uint64_t i; |
| 431 | const Elf_External_Shdr *shdr = find_shdrtab (ehdr); |
| 432 | |
| 433 | for (i = 0; i < GET (ehdr, e_shnum); i++) |
| 434 | { |
| 435 | if (GET (shdr + i, sh_type) == SHT_SYMTAB) |
| 436 | { |
| 437 | *symtab_size = GET (shdr + i, sh_size) / sizeof (Elf_External_Sym); |
| 438 | return (Elf_External_Sym *) (((const char *) ehdr) + |
| 439 | GET (shdr + i, sh_offset)); |
| 440 | } |
| 441 | } |
| 442 | return NULL; |
| 443 | } |
| 444 | |
| 445 | /* Translate a file offset to an address in a loaded segment. */ |
| 446 | |
| 447 | static int |
| 448 | translate_offset (uint64_t file_offset, struct segment *seg, void **addr) |
| 449 | { |
| 450 | while (seg) |
| 451 | { |
| 452 | uint64_t p_from, p_to; |
| 453 | |
| 454 | Elf_External_Phdr *phdr = seg->phdr; |
| 455 | |
| 456 | if (phdr == NULL) |
| 457 | { |
| 458 | seg = seg->next; |
| 459 | continue; |
| 460 | } |
| 461 | |
| 462 | p_from = GET (phdr, p_offset); |
| 463 | p_to = p_from + GET (phdr, p_filesz); |
| 464 | |
| 465 | if (p_from <= file_offset && file_offset < p_to) |
| 466 | { |
| 467 | *addr = (void *) (seg->mapped_addr + (file_offset - p_from)); |
| 468 | return 0; |
| 469 | } |
| 470 | seg = seg->next; |
| 471 | } |
| 472 | |
| 473 | return -1; |
| 474 | } |
| 475 | |
| 476 | /* Lookup the address of FUNC. */ |
| 477 | |
| 478 | int |
| 479 | lookup_function (struct library *lib, const char *func, void **addr) |
| 480 | { |
| 481 | const char *strtab; |
| 482 | uint64_t strtab_size = 0; |
| 483 | Elf_External_Sym *symtab; |
| 484 | uint64_t symtab_size = 0; |
| 485 | uint64_t i; |
| 486 | Elf_External_Ehdr *ehdr = lib->ehdr; |
| 487 | struct segment *seg = lib->segments; |
| 488 | |
| 489 | /* Get the string table for the symbols. */ |
| 490 | strtab = find_strtab (ehdr, ".strtab", &strtab_size); |
| 491 | if (strtab == NULL) |
| 492 | { |
| 493 | printf (".strtab not found."); |
| 494 | return -1; |
| 495 | } |
| 496 | |
| 497 | /* Get the symbol table. */ |
| 498 | symtab = find_symtab (ehdr, &symtab_size); |
| 499 | if (symtab == NULL) |
| 500 | { |
| 501 | printf ("symbol table not found."); |
| 502 | return -1; |
| 503 | } |
| 504 | |
| 505 | for (i = 0; i < symtab_size; i++) |
| 506 | { |
| 507 | Elf_External_Sym *sym = &symtab[i]; |
| 508 | |
| 509 | if (elf_st_type (GET (sym, st_info)) != STT_FUNC) |
| 510 | continue; |
| 511 | |
| 512 | if (GET (sym, st_name) < strtab_size) |
| 513 | { |
| 514 | const char *name = &strtab[GET (sym, st_name)]; |
| 515 | if (strcmp (name, func) == 0) |
| 516 | { |
| 517 | |
| 518 | uint64_t offset = GET (sym, st_value); |
| 519 | return translate_offset (offset, seg, addr); |
| 520 | } |
| 521 | } |
| 522 | } |
| 523 | |
| 524 | return -1; |
| 525 | } |