1 /*- 2 * Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 * 25 * $FreeBSD$ 26 */ 27 28 /* 29 * Dynamic linker for ELF. 30 * 31 * John Polstra <jdp@polstra.com>. 32 */ 33 34 #ifndef __GNUC__ 35 #error "GCC is needed to compile this file" 36 #endif 37 38 #include <sys/param.h> 39 #include <sys/mman.h> 40 #include <sys/stat.h> 41 42 #include <dlfcn.h> 43 #include <err.h> 44 #include <errno.h> 45 #include <fcntl.h> 46 #include <stdarg.h> 47 #include <stdio.h> 48 #include <stdlib.h> 49 #include <string.h> 50 #include <unistd.h> 51 52 #include "debug.h" 53 #include "rtld.h" 54 55 #define END_SYM "_end" 56 #define PATH_RTLD "/usr/libexec/ld-elf.so.1" 57 58 /* Types. */ 59 typedef void (*func_ptr_type)(); 60 61 typedef struct Struct_LockInfo { 62 void *context; /* Client context for creating locks */ 63 void *thelock; /* The one big lock */ 64 /* Methods */ 65 void (*rlock_acquire)(void *lock); 66 void (*wlock_acquire)(void *lock); 67 void (*lock_release)(void *lock); 68 void (*lock_destroy)(void *lock); 69 void (*context_destroy)(void *context); 70 } LockInfo; 71 72 /* 73 * Function declarations. 74 */ 75 static const char *basename(const char *); 76 static void die(void); 77 static void digest_dynamic(Obj_Entry *); 78 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *); 79 static Obj_Entry *dlcheck(void *); 80 static char *find_library(const char *, const Obj_Entry *); 81 static void funclist_call(Funclist *); 82 static void funclist_clear(Funclist *); 83 static void funclist_init(Funclist *); 84 static void funclist_push_head(Funclist *, InitFunc); 85 static void funclist_push_tail(Funclist *, InitFunc); 86 static const char *gethints(void); 87 static void init_dag(Obj_Entry *); 88 static void init_dag1(Obj_Entry *root, Obj_Entry *obj); 89 static void init_rtld(caddr_t); 90 static bool is_exported(const Elf_Sym *); 91 static void linkmap_add(Obj_Entry *); 92 static void linkmap_delete(Obj_Entry *); 93 static int load_needed_objects(Obj_Entry *); 94 static int load_preload_objects(void); 95 static Obj_Entry *load_object(char *); 96 static void lock_nop(void *); 97 static Obj_Entry *obj_from_addr(const void *); 98 static void objlist_add(Objlist *, Obj_Entry *); 99 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *); 100 static void objlist_remove(Objlist *, Obj_Entry *); 101 static int relocate_objects(Obj_Entry *, bool); 102 static void rtld_exit(void); 103 static char *search_library_path(const char *, const char *); 104 static void set_program_var(const char *, const void *); 105 static const Elf_Sym *symlook_list(const char *, unsigned long, 106 Objlist *, const Obj_Entry **, bool in_plt); 107 static void trace_loaded_objects(Obj_Entry *obj); 108 static void unload_object(Obj_Entry *); 109 static void unref_dag(Obj_Entry *); 110 111 void r_debug_state(void); 112 void xprintf(const char *, ...); 113 114 /* 115 * Data declarations. 116 */ 117 static char *error_message; /* Message for dlerror(), or NULL */ 118 struct r_debug r_debug; /* for GDB; */ 119 static bool trust; /* False for setuid and setgid programs */ 120 static char *ld_bind_now; /* Environment variable for immediate binding */ 121 static char *ld_debug; /* Environment variable for debugging */ 122 static char *ld_library_path; /* Environment variable for search path */ 123 static char *ld_preload; /* Environment variable for libraries to 124 load first */ 125 static char *ld_tracing; /* Called from ldd to print libs */ 126 static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 127 static Obj_Entry **obj_tail; /* Link field of last object in list */ 128 static Obj_Entry *obj_main; /* The main program shared object */ 129 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 130 static unsigned long curmark; /* Current mark value */ 131 132 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 133 STAILQ_HEAD_INITIALIZER(list_global); 134 static Objlist list_main = /* Objects loaded at program startup */ 135 STAILQ_HEAD_INITIALIZER(list_main); 136 137 static LockInfo lockinfo; 138 139 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 140 141 #define GDB_STATE(s) r_debug.r_state = s; r_debug_state(); 142 143 extern Elf_Dyn _DYNAMIC; 144 #pragma weak _DYNAMIC 145 146 /* 147 * These are the functions the dynamic linker exports to application 148 * programs. They are the only symbols the dynamic linker is willing 149 * to export from itself. 150 */ 151 static func_ptr_type exports[] = { 152 (func_ptr_type) &_rtld_error, 153 (func_ptr_type) &dlclose, 154 (func_ptr_type) &dlerror, 155 (func_ptr_type) &dlopen, 156 (func_ptr_type) &dlsym, 157 (func_ptr_type) &dladdr, 158 (func_ptr_type) &dllockinit, 159 NULL 160 }; 161 162 /* 163 * Global declarations normally provided by crt1. The dynamic linker is 164 * not built with crt1, so we have to provide them ourselves. 165 */ 166 char *__progname; 167 char **environ; 168 169 static __inline void 170 rlock_acquire(void) 171 { 172 lockinfo.rlock_acquire(lockinfo.thelock); 173 } 174 175 static __inline void 176 wlock_acquire(void) 177 { 178 lockinfo.wlock_acquire(lockinfo.thelock); 179 } 180 181 static __inline void 182 lock_release(void) 183 { 184 lockinfo.lock_release(lockinfo.thelock); 185 } 186 187 /* 188 * Main entry point for dynamic linking. The first argument is the 189 * stack pointer. The stack is expected to be laid out as described 190 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 191 * Specifically, the stack pointer points to a word containing 192 * ARGC. Following that in the stack is a null-terminated sequence 193 * of pointers to argument strings. Then comes a null-terminated 194 * sequence of pointers to environment strings. Finally, there is a 195 * sequence of "auxiliary vector" entries. 196 * 197 * The second argument points to a place to store the dynamic linker's 198 * exit procedure pointer and the third to a place to store the main 199 * program's object. 200 * 201 * The return value is the main program's entry point. 202 */ 203 func_ptr_type 204 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 205 { 206 Elf_Auxinfo *aux_info[AT_COUNT]; 207 int i; 208 int argc; 209 char **argv; 210 char **env; 211 Elf_Auxinfo *aux; 212 Elf_Auxinfo *auxp; 213 const char *argv0; 214 Obj_Entry *obj; 215 Funclist initlist; 216 217 /* 218 * On entry, the dynamic linker itself has not been relocated yet. 219 * Be very careful not to reference any global data until after 220 * init_rtld has returned. It is OK to reference file-scope statics 221 * and string constants, and to call static and global functions. 222 */ 223 224 /* Find the auxiliary vector on the stack. */ 225 argc = *sp++; 226 argv = (char **) sp; 227 sp += argc + 1; /* Skip over arguments and NULL terminator */ 228 env = (char **) sp; 229 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 230 ; 231 aux = (Elf_Auxinfo *) sp; 232 233 /* Digest the auxiliary vector. */ 234 for (i = 0; i < AT_COUNT; i++) 235 aux_info[i] = NULL; 236 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 237 if (auxp->a_type < AT_COUNT) 238 aux_info[auxp->a_type] = auxp; 239 } 240 241 /* Initialize and relocate ourselves. */ 242 assert(aux_info[AT_BASE] != NULL); 243 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 244 245 __progname = obj_rtld.path; 246 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 247 environ = env; 248 249 trust = geteuid() == getuid() && getegid() == getgid(); 250 251 ld_bind_now = getenv("LD_BIND_NOW"); 252 if (trust) { 253 ld_debug = getenv("LD_DEBUG"); 254 ld_library_path = getenv("LD_LIBRARY_PATH"); 255 ld_preload = getenv("LD_PRELOAD"); 256 } 257 ld_tracing = getenv("LD_TRACE_LOADED_OBJECTS"); 258 259 if (ld_debug != NULL && *ld_debug != '\0') 260 debug = 1; 261 dbg("%s is initialized, base address = %p", __progname, 262 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 263 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 264 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 265 266 /* 267 * Load the main program, or process its program header if it is 268 * already loaded. 269 */ 270 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 271 int fd = aux_info[AT_EXECFD]->a_un.a_val; 272 dbg("loading main program"); 273 obj_main = map_object(fd, argv0, NULL); 274 close(fd); 275 if (obj_main == NULL) 276 die(); 277 } else { /* Main program already loaded. */ 278 const Elf_Phdr *phdr; 279 int phnum; 280 caddr_t entry; 281 282 dbg("processing main program's program header"); 283 assert(aux_info[AT_PHDR] != NULL); 284 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 285 assert(aux_info[AT_PHNUM] != NULL); 286 phnum = aux_info[AT_PHNUM]->a_un.a_val; 287 assert(aux_info[AT_PHENT] != NULL); 288 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 289 assert(aux_info[AT_ENTRY] != NULL); 290 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 291 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 292 die(); 293 } 294 295 obj_main->path = xstrdup(argv0); 296 obj_main->mainprog = true; 297 298 /* 299 * Get the actual dynamic linker pathname from the executable if 300 * possible. (It should always be possible.) That ensures that 301 * gdb will find the right dynamic linker even if a non-standard 302 * one is being used. 303 */ 304 if (obj_main->interp != NULL && 305 strcmp(obj_main->interp, obj_rtld.path) != 0) { 306 free(obj_rtld.path); 307 obj_rtld.path = xstrdup(obj_main->interp); 308 } 309 310 digest_dynamic(obj_main); 311 312 linkmap_add(obj_main); 313 linkmap_add(&obj_rtld); 314 315 /* Link the main program into the list of objects. */ 316 *obj_tail = obj_main; 317 obj_tail = &obj_main->next; 318 obj_main->refcount++; 319 320 /* Initialize a fake symbol for resolving undefined weak references. */ 321 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 322 sym_zero.st_shndx = SHN_ABS; 323 324 dbg("loading LD_PRELOAD libraries"); 325 if (load_preload_objects() == -1) 326 die(); 327 328 dbg("loading needed objects"); 329 if (load_needed_objects(obj_main) == -1) 330 die(); 331 332 /* 333 * Make a list of all objects loaded at startup. Also construct 334 * the list of init functions to call, in reverse order. 335 */ 336 funclist_init(&initlist); 337 for (obj = obj_list; obj != NULL; obj = obj->next) { 338 objlist_add(&list_main, obj); 339 if (obj->init != NULL && !obj->mainprog) 340 funclist_push_head(&initlist, obj->init); 341 } 342 343 if (ld_tracing) { /* We're done */ 344 trace_loaded_objects(obj_main); 345 exit(0); 346 } 347 348 if (relocate_objects(obj_main, 349 ld_bind_now != NULL && *ld_bind_now != '\0') == -1) 350 die(); 351 352 dbg("doing copy relocations"); 353 if (do_copy_relocations(obj_main) == -1) 354 die(); 355 356 dbg("initializing key program variables"); 357 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 358 set_program_var("environ", env); 359 360 dbg("initializing default locks"); 361 dllockinit(NULL, NULL, NULL, NULL, NULL, NULL, NULL); 362 363 r_debug_state(); /* say hello to gdb! */ 364 365 funclist_call(&initlist); 366 wlock_acquire(); 367 funclist_clear(&initlist); 368 lock_release(); 369 370 dbg("transferring control to program entry point = %p", obj_main->entry); 371 372 /* Return the exit procedure and the program entry point. */ 373 *exit_proc = rtld_exit; 374 *objp = obj_main; 375 return (func_ptr_type) obj_main->entry; 376 } 377 378 Elf_Addr 379 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 380 { 381 const Elf_Rel *rel; 382 const Elf_Sym *def; 383 const Obj_Entry *defobj; 384 Elf_Addr *where; 385 Elf_Addr target; 386 387 wlock_acquire(); 388 if (obj->pltrel) 389 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 390 else 391 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 392 393 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 394 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true); 395 if (def == NULL) 396 die(); 397 398 target = (Elf_Addr)(defobj->relocbase + def->st_value); 399 400 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 401 defobj->strtab + def->st_name, basename(obj->path), 402 (void *)target, basename(defobj->path)); 403 404 reloc_jmpslot(where, target); 405 lock_release(); 406 return target; 407 } 408 409 /* 410 * Error reporting function. Use it like printf. If formats the message 411 * into a buffer, and sets things up so that the next call to dlerror() 412 * will return the message. 413 */ 414 void 415 _rtld_error(const char *fmt, ...) 416 { 417 static char buf[512]; 418 va_list ap; 419 420 va_start(ap, fmt); 421 vsnprintf(buf, sizeof buf, fmt, ap); 422 error_message = buf; 423 va_end(ap); 424 } 425 426 static const char * 427 basename(const char *name) 428 { 429 const char *p = strrchr(name, '/'); 430 return p != NULL ? p + 1 : name; 431 } 432 433 static void 434 die(void) 435 { 436 const char *msg = dlerror(); 437 438 if (msg == NULL) 439 msg = "Fatal error"; 440 errx(1, "%s", msg); 441 } 442 443 /* 444 * Process a shared object's DYNAMIC section, and save the important 445 * information in its Obj_Entry structure. 446 */ 447 static void 448 digest_dynamic(Obj_Entry *obj) 449 { 450 const Elf_Dyn *dynp; 451 Needed_Entry **needed_tail = &obj->needed; 452 const Elf_Dyn *dyn_rpath = NULL; 453 int plttype = DT_REL; 454 455 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 456 switch (dynp->d_tag) { 457 458 case DT_REL: 459 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 460 break; 461 462 case DT_RELSZ: 463 obj->relsize = dynp->d_un.d_val; 464 break; 465 466 case DT_RELENT: 467 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 468 break; 469 470 case DT_JMPREL: 471 obj->pltrel = (const Elf_Rel *) 472 (obj->relocbase + dynp->d_un.d_ptr); 473 break; 474 475 case DT_PLTRELSZ: 476 obj->pltrelsize = dynp->d_un.d_val; 477 break; 478 479 case DT_RELA: 480 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 481 break; 482 483 case DT_RELASZ: 484 obj->relasize = dynp->d_un.d_val; 485 break; 486 487 case DT_RELAENT: 488 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 489 break; 490 491 case DT_PLTREL: 492 plttype = dynp->d_un.d_val; 493 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 494 break; 495 496 case DT_SYMTAB: 497 obj->symtab = (const Elf_Sym *) 498 (obj->relocbase + dynp->d_un.d_ptr); 499 break; 500 501 case DT_SYMENT: 502 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 503 break; 504 505 case DT_STRTAB: 506 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 507 break; 508 509 case DT_STRSZ: 510 obj->strsize = dynp->d_un.d_val; 511 break; 512 513 case DT_HASH: 514 { 515 const Elf_Addr *hashtab = (const Elf_Addr *) 516 (obj->relocbase + dynp->d_un.d_ptr); 517 obj->nbuckets = hashtab[0]; 518 obj->nchains = hashtab[1]; 519 obj->buckets = hashtab + 2; 520 obj->chains = obj->buckets + obj->nbuckets; 521 } 522 break; 523 524 case DT_NEEDED: 525 if (!obj->rtld) { 526 Needed_Entry *nep = NEW(Needed_Entry); 527 nep->name = dynp->d_un.d_val; 528 nep->obj = NULL; 529 nep->next = NULL; 530 531 *needed_tail = nep; 532 needed_tail = &nep->next; 533 } 534 break; 535 536 case DT_PLTGOT: 537 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 538 break; 539 540 case DT_TEXTREL: 541 obj->textrel = true; 542 break; 543 544 case DT_SYMBOLIC: 545 obj->symbolic = true; 546 break; 547 548 case DT_RPATH: 549 /* 550 * We have to wait until later to process this, because we 551 * might not have gotten the address of the string table yet. 552 */ 553 dyn_rpath = dynp; 554 break; 555 556 case DT_SONAME: 557 /* Not used by the dynamic linker. */ 558 break; 559 560 case DT_INIT: 561 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 562 break; 563 564 case DT_FINI: 565 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 566 break; 567 568 case DT_DEBUG: 569 /* XXX - not implemented yet */ 570 dbg("Filling in DT_DEBUG entry"); 571 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 572 break; 573 574 default: 575 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag); 576 break; 577 } 578 } 579 580 obj->traced = false; 581 582 if (plttype == DT_RELA) { 583 obj->pltrela = (const Elf_Rela *) obj->pltrel; 584 obj->pltrel = NULL; 585 obj->pltrelasize = obj->pltrelsize; 586 obj->pltrelsize = 0; 587 } 588 589 if (dyn_rpath != NULL) 590 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 591 } 592 593 /* 594 * Process a shared object's program header. This is used only for the 595 * main program, when the kernel has already loaded the main program 596 * into memory before calling the dynamic linker. It creates and 597 * returns an Obj_Entry structure. 598 */ 599 static Obj_Entry * 600 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 601 { 602 Obj_Entry *obj; 603 const Elf_Phdr *phlimit = phdr + phnum; 604 const Elf_Phdr *ph; 605 int nsegs = 0; 606 607 obj = obj_new(); 608 for (ph = phdr; ph < phlimit; ph++) { 609 switch (ph->p_type) { 610 611 case PT_PHDR: 612 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 613 _rtld_error("%s: invalid PT_PHDR", path); 614 return NULL; 615 } 616 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 617 obj->phsize = ph->p_memsz; 618 break; 619 620 case PT_INTERP: 621 obj->interp = (const char *) ph->p_vaddr; 622 break; 623 624 case PT_LOAD: 625 if (nsegs >= 2) { 626 _rtld_error("%s: too many PT_LOAD segments", path); 627 return NULL; 628 } 629 if (nsegs == 0) { /* First load segment */ 630 obj->vaddrbase = trunc_page(ph->p_vaddr); 631 obj->mapbase = (caddr_t) obj->vaddrbase; 632 obj->relocbase = obj->mapbase - obj->vaddrbase; 633 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 634 obj->vaddrbase; 635 } else { /* Last load segment */ 636 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 637 obj->vaddrbase; 638 } 639 nsegs++; 640 break; 641 642 case PT_DYNAMIC: 643 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 644 break; 645 } 646 } 647 if (nsegs < 2) { 648 _rtld_error("%s: too few PT_LOAD segments", path); 649 return NULL; 650 } 651 652 obj->entry = entry; 653 return obj; 654 } 655 656 static Obj_Entry * 657 dlcheck(void *handle) 658 { 659 Obj_Entry *obj; 660 661 for (obj = obj_list; obj != NULL; obj = obj->next) 662 if (obj == (Obj_Entry *) handle) 663 break; 664 665 if (obj == NULL || obj->dl_refcount == 0) { 666 _rtld_error("Invalid shared object handle %p", handle); 667 return NULL; 668 } 669 return obj; 670 } 671 672 /* 673 * Hash function for symbol table lookup. Don't even think about changing 674 * this. It is specified by the System V ABI. 675 */ 676 unsigned long 677 elf_hash(const char *name) 678 { 679 const unsigned char *p = (const unsigned char *) name; 680 unsigned long h = 0; 681 unsigned long g; 682 683 while (*p != '\0') { 684 h = (h << 4) + *p++; 685 if ((g = h & 0xf0000000) != 0) 686 h ^= g >> 24; 687 h &= ~g; 688 } 689 return h; 690 } 691 692 /* 693 * Find the library with the given name, and return its full pathname. 694 * The returned string is dynamically allocated. Generates an error 695 * message and returns NULL if the library cannot be found. 696 * 697 * If the second argument is non-NULL, then it refers to an already- 698 * loaded shared object, whose library search path will be searched. 699 * 700 * The search order is: 701 * rpath in the referencing file 702 * LD_LIBRARY_PATH 703 * ldconfig hints 704 * /usr/lib 705 */ 706 static char * 707 find_library(const char *name, const Obj_Entry *refobj) 708 { 709 char *pathname; 710 711 if (strchr(name, '/') != NULL) { /* Hard coded pathname */ 712 if (name[0] != '/' && !trust) { 713 _rtld_error("Absolute pathname required for shared object \"%s\"", 714 name); 715 return NULL; 716 } 717 return xstrdup(name); 718 } 719 720 dbg(" Searching for \"%s\"", name); 721 722 if ((refobj != NULL && 723 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 724 (pathname = search_library_path(name, ld_library_path)) != NULL || 725 (pathname = search_library_path(name, gethints())) != NULL || 726 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 727 return pathname; 728 729 _rtld_error("Shared object \"%s\" not found", name); 730 return NULL; 731 } 732 733 /* 734 * Given a symbol number in a referencing object, find the corresponding 735 * definition of the symbol. Returns a pointer to the symbol, or NULL if 736 * no definition was found. Returns a pointer to the Obj_Entry of the 737 * defining object via the reference parameter DEFOBJ_OUT. 738 */ 739 const Elf_Sym * 740 find_symdef(unsigned long symnum, Obj_Entry *refobj, 741 const Obj_Entry **defobj_out, bool in_plt) 742 { 743 const Elf_Sym *ref; 744 const Elf_Sym *def; 745 const Elf_Sym *symp; 746 const Obj_Entry *obj; 747 const Obj_Entry *defobj; 748 const Objlist_Entry *elm; 749 const char *name; 750 unsigned long hash; 751 752 ref = refobj->symtab + symnum; 753 name = refobj->strtab + ref->st_name; 754 hash = elf_hash(name); 755 def = NULL; 756 defobj = NULL; 757 curmark++; 758 759 if (refobj->symbolic) { /* Look first in the referencing object */ 760 symp = symlook_obj(name, hash, refobj, in_plt); 761 refobj->mark = curmark; 762 if (symp != NULL) { 763 def = symp; 764 defobj = refobj; 765 } 766 } 767 768 /* Search all objects loaded at program start up. */ 769 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 770 symp = symlook_list(name, hash, &list_main, &obj, in_plt); 771 if (symp != NULL && 772 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 773 def = symp; 774 defobj = obj; 775 } 776 } 777 778 /* Search all dlopened DAGs containing the referencing object. */ 779 STAILQ_FOREACH(elm, &refobj->dldags, link) { 780 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 781 break; 782 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt); 783 if (symp != NULL && 784 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 785 def = symp; 786 defobj = obj; 787 } 788 } 789 790 /* Search all RTLD_GLOBAL objects. */ 791 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 792 symp = symlook_list(name, hash, &list_global, &obj, in_plt); 793 if (symp != NULL && 794 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 795 def = symp; 796 defobj = obj; 797 } 798 } 799 800 /* 801 * Search the dynamic linker itself, and possibly resolve the 802 * symbol from there. This is how the application links to 803 * dynamic linker services such as dlopen. Only the values listed 804 * in the "exports" array can be resolved from the dynamic linker. 805 */ 806 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 807 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 808 if (symp != NULL && is_exported(symp)) { 809 def = symp; 810 defobj = &obj_rtld; 811 } 812 } 813 814 /* 815 * If we found no definition and the reference is weak, treat the 816 * symbol as having the value zero. 817 */ 818 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 819 def = &sym_zero; 820 defobj = obj_main; 821 } 822 823 if (def != NULL) 824 *defobj_out = defobj; 825 else 826 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 827 return def; 828 } 829 830 static void 831 funclist_call(Funclist *list) 832 { 833 Funclist_Entry *elm; 834 835 STAILQ_FOREACH(elm, list, link) { 836 dbg("calling init/fini function at %p", elm->func); 837 (*elm->func)(); 838 } 839 } 840 841 static void 842 funclist_clear(Funclist *list) 843 { 844 Funclist_Entry *elm; 845 846 while (!STAILQ_EMPTY(list)) { 847 elm = STAILQ_FIRST(list); 848 STAILQ_REMOVE_HEAD(list, link); 849 free(elm); 850 } 851 } 852 853 static void 854 funclist_init(Funclist *list) 855 { 856 STAILQ_INIT(list); 857 } 858 859 static void 860 funclist_push_head(Funclist *list, InitFunc func) 861 { 862 Funclist_Entry *elm; 863 864 elm = NEW(Funclist_Entry); 865 elm->func = func; 866 STAILQ_INSERT_HEAD(list, elm, link); 867 } 868 869 static void 870 funclist_push_tail(Funclist *list, InitFunc func) 871 { 872 Funclist_Entry *elm; 873 874 elm = NEW(Funclist_Entry); 875 elm->func = func; 876 STAILQ_INSERT_TAIL(list, elm, link); 877 } 878 879 /* 880 * Return the search path from the ldconfig hints file, reading it if 881 * necessary. Returns NULL if there are problems with the hints file, 882 * or if the search path there is empty. 883 */ 884 static const char * 885 gethints(void) 886 { 887 static char *hints; 888 889 if (hints == NULL) { 890 int fd; 891 struct elfhints_hdr hdr; 892 char *p; 893 894 /* Keep from trying again in case the hints file is bad. */ 895 hints = ""; 896 897 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 898 return NULL; 899 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 900 hdr.magic != ELFHINTS_MAGIC || 901 hdr.version != 1) { 902 close(fd); 903 return NULL; 904 } 905 p = xmalloc(hdr.dirlistlen + 1); 906 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 907 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { 908 free(p); 909 close(fd); 910 return NULL; 911 } 912 hints = p; 913 close(fd); 914 } 915 return hints[0] != '\0' ? hints : NULL; 916 } 917 918 static void 919 init_dag(Obj_Entry *root) 920 { 921 curmark++; 922 init_dag1(root, root); 923 } 924 925 static void 926 init_dag1(Obj_Entry *root, Obj_Entry *obj) 927 { 928 const Needed_Entry *needed; 929 930 if (obj->mark == curmark) 931 return; 932 obj->mark = curmark; 933 objlist_add(&obj->dldags, root); 934 objlist_add(&root->dagmembers, obj); 935 for (needed = obj->needed; needed != NULL; needed = needed->next) 936 if (needed->obj != NULL) 937 init_dag1(root, needed->obj); 938 } 939 940 /* 941 * Initialize the dynamic linker. The argument is the address at which 942 * the dynamic linker has been mapped into memory. The primary task of 943 * this function is to relocate the dynamic linker. 944 */ 945 static void 946 init_rtld(caddr_t mapbase) 947 { 948 /* 949 * Conjure up an Obj_Entry structure for the dynamic linker. 950 * 951 * The "path" member is supposed to be dynamically-allocated, but we 952 * aren't yet initialized sufficiently to do that. Below we will 953 * replace the static version with a dynamically-allocated copy. 954 */ 955 obj_rtld.path = PATH_RTLD; 956 obj_rtld.rtld = true; 957 obj_rtld.mapbase = mapbase; 958 #ifdef PIC 959 obj_rtld.relocbase = mapbase; 960 #endif 961 if (&_DYNAMIC != 0) { 962 obj_rtld.dynamic = rtld_dynamic(&obj_rtld); 963 digest_dynamic(&obj_rtld); 964 assert(obj_rtld.needed == NULL); 965 assert(!obj_rtld.textrel); 966 967 /* 968 * Temporarily put the dynamic linker entry into the object list, so 969 * that symbols can be found. 970 */ 971 obj_list = &obj_rtld; 972 obj_tail = &obj_rtld.next; 973 974 relocate_objects(&obj_rtld, true); 975 } 976 977 /* Make the object list empty again. */ 978 obj_list = NULL; 979 obj_tail = &obj_list; 980 981 /* Replace the path with a dynamically allocated copy. */ 982 obj_rtld.path = xstrdup(obj_rtld.path); 983 984 r_debug.r_brk = r_debug_state; 985 r_debug.r_state = RT_CONSISTENT; 986 } 987 988 static bool 989 is_exported(const Elf_Sym *def) 990 { 991 func_ptr_type value; 992 const func_ptr_type *p; 993 994 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value); 995 for (p = exports; *p != NULL; p++) 996 if (*p == value) 997 return true; 998 return false; 999 } 1000 1001 /* 1002 * Given a shared object, traverse its list of needed objects, and load 1003 * each of them. Returns 0 on success. Generates an error message and 1004 * returns -1 on failure. 1005 */ 1006 static int 1007 load_needed_objects(Obj_Entry *first) 1008 { 1009 Obj_Entry *obj; 1010 1011 for (obj = first; obj != NULL; obj = obj->next) { 1012 Needed_Entry *needed; 1013 1014 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1015 const char *name = obj->strtab + needed->name; 1016 char *path = find_library(name, obj); 1017 1018 needed->obj = NULL; 1019 if (path == NULL && !ld_tracing) 1020 return -1; 1021 1022 if (path) { 1023 needed->obj = load_object(path); 1024 if (needed->obj == NULL && !ld_tracing) 1025 return -1; /* XXX - cleanup */ 1026 } 1027 } 1028 } 1029 1030 return 0; 1031 } 1032 1033 static int 1034 load_preload_objects(void) 1035 { 1036 char *p = ld_preload; 1037 1038 if (p == NULL) 1039 return NULL; 1040 1041 p += strspn(p, ":;"); 1042 while (*p != '\0') { 1043 size_t len = strcspn(p, ":;"); 1044 char *path; 1045 char savech; 1046 1047 savech = p[len]; 1048 p[len] = '\0'; 1049 if ((path = find_library(p, NULL)) == NULL) 1050 return -1; 1051 if (load_object(path) == NULL) 1052 return -1; /* XXX - cleanup */ 1053 p[len] = savech; 1054 p += len; 1055 p += strspn(p, ":;"); 1056 } 1057 return 0; 1058 } 1059 1060 /* 1061 * Load a shared object into memory, if it is not already loaded. The 1062 * argument must be a string allocated on the heap. This function assumes 1063 * responsibility for freeing it when necessary. 1064 * 1065 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1066 * on failure. 1067 */ 1068 static Obj_Entry * 1069 load_object(char *path) 1070 { 1071 Obj_Entry *obj; 1072 int fd = -1; 1073 struct stat sb; 1074 1075 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1076 if (strcmp(obj->path, path) == 0) 1077 break; 1078 1079 /* 1080 * If we didn't find a match by pathname, open the file and check 1081 * again by device and inode. This avoids false mismatches caused 1082 * by multiple links or ".." in pathnames. 1083 * 1084 * To avoid a race, we open the file and use fstat() rather than 1085 * using stat(). 1086 */ 1087 if (obj == NULL) { 1088 if ((fd = open(path, O_RDONLY)) == -1) { 1089 _rtld_error("Cannot open \"%s\"", path); 1090 return NULL; 1091 } 1092 if (fstat(fd, &sb) == -1) { 1093 _rtld_error("Cannot fstat \"%s\"", path); 1094 close(fd); 1095 return NULL; 1096 } 1097 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1098 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) { 1099 close(fd); 1100 break; 1101 } 1102 } 1103 } 1104 1105 if (obj == NULL) { /* First use of this object, so we must map it in */ 1106 dbg("loading \"%s\"", path); 1107 obj = map_object(fd, path, &sb); 1108 close(fd); 1109 if (obj == NULL) { 1110 free(path); 1111 return NULL; 1112 } 1113 1114 obj->path = path; 1115 digest_dynamic(obj); 1116 1117 *obj_tail = obj; 1118 obj_tail = &obj->next; 1119 linkmap_add(obj); /* for GDB */ 1120 1121 dbg(" %p .. %p: %s", obj->mapbase, 1122 obj->mapbase + obj->mapsize - 1, obj->path); 1123 if (obj->textrel) 1124 dbg(" WARNING: %s has impure text", obj->path); 1125 } else 1126 free(path); 1127 1128 obj->refcount++; 1129 return obj; 1130 } 1131 1132 static void 1133 lock_nop(void *lock) 1134 { 1135 } 1136 1137 static Obj_Entry * 1138 obj_from_addr(const void *addr) 1139 { 1140 unsigned long endhash; 1141 Obj_Entry *obj; 1142 1143 endhash = elf_hash(END_SYM); 1144 for (obj = obj_list; obj != NULL; obj = obj->next) { 1145 const Elf_Sym *endsym; 1146 1147 if (addr < (void *) obj->mapbase) 1148 continue; 1149 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL) 1150 continue; /* No "end" symbol?! */ 1151 if (addr < (void *) (obj->relocbase + endsym->st_value)) 1152 return obj; 1153 } 1154 return NULL; 1155 } 1156 1157 static void 1158 objlist_add(Objlist *list, Obj_Entry *obj) 1159 { 1160 Objlist_Entry *elm; 1161 1162 elm = NEW(Objlist_Entry); 1163 elm->obj = obj; 1164 STAILQ_INSERT_TAIL(list, elm, link); 1165 } 1166 1167 static Objlist_Entry * 1168 objlist_find(Objlist *list, const Obj_Entry *obj) 1169 { 1170 Objlist_Entry *elm; 1171 1172 STAILQ_FOREACH(elm, list, link) 1173 if (elm->obj == obj) 1174 return elm; 1175 return NULL; 1176 } 1177 1178 static void 1179 objlist_remove(Objlist *list, Obj_Entry *obj) 1180 { 1181 Objlist_Entry *elm; 1182 1183 if ((elm = objlist_find(list, obj)) != NULL) { 1184 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1185 free(elm); 1186 } 1187 } 1188 1189 /* 1190 * Relocate newly-loaded shared objects. The argument is a pointer to 1191 * the Obj_Entry for the first such object. All objects from the first 1192 * to the end of the list of objects are relocated. Returns 0 on success, 1193 * or -1 on failure. 1194 */ 1195 static int 1196 relocate_objects(Obj_Entry *first, bool bind_now) 1197 { 1198 Obj_Entry *obj; 1199 1200 for (obj = first; obj != NULL; obj = obj->next) { 1201 if (obj != &obj_rtld) 1202 dbg("relocating \"%s\"", obj->path); 1203 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1204 obj->symtab == NULL || obj->strtab == NULL) { 1205 _rtld_error("%s: Shared object has no run-time symbol table", 1206 obj->path); 1207 return -1; 1208 } 1209 1210 if (obj->textrel) { 1211 /* There are relocations to the write-protected text segment. */ 1212 if (mprotect(obj->mapbase, obj->textsize, 1213 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1214 _rtld_error("%s: Cannot write-enable text segment: %s", 1215 obj->path, strerror(errno)); 1216 return -1; 1217 } 1218 } 1219 1220 /* Process the non-PLT relocations. */ 1221 if (reloc_non_plt(obj, &obj_rtld)) 1222 return -1; 1223 1224 if (obj->textrel) { /* Re-protected the text segment. */ 1225 if (mprotect(obj->mapbase, obj->textsize, 1226 PROT_READ|PROT_EXEC) == -1) { 1227 _rtld_error("%s: Cannot write-protect text segment: %s", 1228 obj->path, strerror(errno)); 1229 return -1; 1230 } 1231 } 1232 1233 /* Process the PLT relocations. */ 1234 if (reloc_plt(obj, bind_now)) 1235 return -1; 1236 1237 /* 1238 * Set up the magic number and version in the Obj_Entry. These 1239 * were checked in the crt1.o from the original ElfKit, so we 1240 * set them for backward compatibility. 1241 */ 1242 obj->magic = RTLD_MAGIC; 1243 obj->version = RTLD_VERSION; 1244 1245 /* Set the special PLT or GOT entries. */ 1246 init_pltgot(obj); 1247 } 1248 1249 return 0; 1250 } 1251 1252 /* 1253 * Cleanup procedure. It will be called (by the atexit mechanism) just 1254 * before the process exits. 1255 */ 1256 static void 1257 rtld_exit(void) 1258 { 1259 Obj_Entry *obj; 1260 1261 dbg("rtld_exit()"); 1262 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1263 if (obj->fini != NULL) 1264 (*obj->fini)(); 1265 } 1266 1267 static char * 1268 search_library_path(const char *name, const char *path) 1269 { 1270 size_t namelen = strlen(name); 1271 const char *p = path; 1272 1273 if (p == NULL) 1274 return NULL; 1275 1276 p += strspn(p, ":;"); 1277 while (*p != '\0') { 1278 size_t len = strcspn(p, ":;"); 1279 1280 if (*p == '/' || trust) { 1281 char *pathname; 1282 const char *dir = p; 1283 size_t dirlen = len; 1284 1285 pathname = xmalloc(dirlen + 1 + namelen + 1); 1286 strncpy(pathname, dir, dirlen); 1287 pathname[dirlen] = '/'; 1288 strcpy(pathname + dirlen + 1, name); 1289 1290 dbg(" Trying \"%s\"", pathname); 1291 if (access(pathname, F_OK) == 0) /* We found it */ 1292 return pathname; 1293 1294 free(pathname); 1295 } 1296 p += len; 1297 p += strspn(p, ":;"); 1298 } 1299 1300 return NULL; 1301 } 1302 1303 int 1304 dlclose(void *handle) 1305 { 1306 Obj_Entry *root; 1307 Obj_Entry *obj; 1308 Funclist finilist; 1309 1310 wlock_acquire(); 1311 root = dlcheck(handle); 1312 if (root == NULL) { 1313 lock_release(); 1314 return -1; 1315 } 1316 1317 /* Unreference the object and its dependencies. */ 1318 root->dl_refcount--; 1319 unref_dag(root); 1320 1321 if (root->refcount == 0) { 1322 /* 1323 * The object is no longer referenced, so we must unload it. 1324 * First, make a list of the fini functions and then call them 1325 * with no locks held. 1326 */ 1327 funclist_init(&finilist); 1328 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1329 if (obj->refcount == 0 && obj->fini != NULL) 1330 funclist_push_tail(&finilist, obj->fini); 1331 1332 lock_release(); 1333 funclist_call(&finilist); 1334 wlock_acquire(); 1335 funclist_clear(&finilist); 1336 1337 /* Finish cleaning up the newly-unreferenced objects. */ 1338 GDB_STATE(RT_DELETE); 1339 unload_object(root); 1340 GDB_STATE(RT_CONSISTENT); 1341 } 1342 lock_release(); 1343 return 0; 1344 } 1345 1346 const char * 1347 dlerror(void) 1348 { 1349 char *msg = error_message; 1350 error_message = NULL; 1351 return msg; 1352 } 1353 1354 void 1355 dllockinit(void *context, 1356 void *(*lock_create)(void *context), 1357 void (*rlock_acquire)(void *lock), 1358 void (*wlock_acquire)(void *lock), 1359 void (*lock_release)(void *lock), 1360 void (*lock_destroy)(void *lock), 1361 void (*context_destroy)(void *context)) 1362 { 1363 /* NULL arguments mean reset to the built-in locks. */ 1364 if (lock_create == NULL) { 1365 context = NULL; 1366 lock_create = lockdflt_create; 1367 rlock_acquire = wlock_acquire = lockdflt_acquire; 1368 lock_release = lockdflt_release; 1369 lock_destroy = lockdflt_destroy; 1370 context_destroy = NULL; 1371 } 1372 1373 /* Temporarily set locking methods to no-ops. */ 1374 lockinfo.rlock_acquire = lock_nop; 1375 lockinfo.wlock_acquire = lock_nop; 1376 lockinfo.lock_release = lock_nop; 1377 1378 /* Release any existing locks and context. */ 1379 if (lockinfo.lock_destroy != NULL) 1380 lockinfo.lock_destroy(lockinfo.thelock); 1381 if (lockinfo.context_destroy != NULL) 1382 lockinfo.context_destroy(lockinfo.context); 1383 1384 /* 1385 * Allocate the locks we will need and call all the new locking 1386 * methods, to accomplish any needed lazy binding for the methods 1387 * themselves. 1388 */ 1389 lockinfo.thelock = lock_create(lockinfo.context); 1390 rlock_acquire(lockinfo.thelock); 1391 lock_release(lockinfo.thelock); 1392 wlock_acquire(lockinfo.thelock); 1393 lock_release(lockinfo.thelock); 1394 1395 /* Record the new method information. */ 1396 lockinfo.context = context; 1397 lockinfo.rlock_acquire = rlock_acquire; 1398 lockinfo.wlock_acquire = wlock_acquire; 1399 lockinfo.lock_release = lock_release; 1400 lockinfo.lock_destroy = lock_destroy; 1401 lockinfo.context_destroy = context_destroy; 1402 } 1403 1404 void * 1405 dlopen(const char *name, int mode) 1406 { 1407 Obj_Entry **old_obj_tail; 1408 Obj_Entry *obj; 1409 Obj_Entry *initobj; 1410 Funclist initlist; 1411 1412 funclist_init(&initlist); 1413 1414 wlock_acquire(); 1415 GDB_STATE(RT_ADD); 1416 1417 old_obj_tail = obj_tail; 1418 obj = NULL; 1419 if (name == NULL) { 1420 obj = obj_main; 1421 obj->refcount++; 1422 } else { 1423 char *path = find_library(name, obj_main); 1424 if (path != NULL) 1425 obj = load_object(path); 1426 } 1427 1428 if (obj) { 1429 obj->dl_refcount++; 1430 if (mode & RTLD_GLOBAL && objlist_find(&list_global, obj) == NULL) 1431 objlist_add(&list_global, obj); 1432 mode &= RTLD_MODEMASK; 1433 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1434 assert(*old_obj_tail == obj); 1435 1436 if (load_needed_objects(obj) == -1 || 1437 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) { 1438 obj->dl_refcount--; 1439 unref_dag(obj); 1440 if (obj->refcount == 0) 1441 unload_object(obj); 1442 obj = NULL; 1443 } else { 1444 /* Make list of init functions to call, in reverse order */ 1445 for (initobj = obj; initobj != NULL; initobj = initobj->next) 1446 if (initobj->init != NULL) 1447 funclist_push_head(&initlist, initobj->init); 1448 } 1449 } 1450 } 1451 1452 GDB_STATE(RT_CONSISTENT); 1453 1454 /* Call the init functions with no locks held. */ 1455 lock_release(); 1456 funclist_call(&initlist); 1457 wlock_acquire(); 1458 funclist_clear(&initlist); 1459 lock_release(); 1460 return obj; 1461 } 1462 1463 void * 1464 dlsym(void *handle, const char *name) 1465 { 1466 const Obj_Entry *obj; 1467 unsigned long hash; 1468 const Elf_Sym *def; 1469 const Obj_Entry *defobj; 1470 1471 hash = elf_hash(name); 1472 def = NULL; 1473 defobj = NULL; 1474 1475 wlock_acquire(); 1476 if (handle == NULL || handle == RTLD_NEXT) { 1477 void *retaddr; 1478 1479 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1480 if ((obj = obj_from_addr(retaddr)) == NULL) { 1481 _rtld_error("Cannot determine caller's shared object"); 1482 lock_release(); 1483 return NULL; 1484 } 1485 if (handle == NULL) { /* Just the caller's shared object. */ 1486 def = symlook_obj(name, hash, obj, true); 1487 defobj = obj; 1488 } else { /* All the shared objects after the caller's */ 1489 while ((obj = obj->next) != NULL) { 1490 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1491 defobj = obj; 1492 break; 1493 } 1494 } 1495 } 1496 } else { 1497 if ((obj = dlcheck(handle)) == NULL) { 1498 lock_release(); 1499 return NULL; 1500 } 1501 1502 if (obj->mainprog) { 1503 /* Search main program and all libraries loaded by it. */ 1504 curmark++; 1505 def = symlook_list(name, hash, &list_main, &defobj, true); 1506 } else { 1507 /* 1508 * XXX - This isn't correct. The search should include the whole 1509 * DAG rooted at the given object. 1510 */ 1511 def = symlook_obj(name, hash, obj, true); 1512 defobj = obj; 1513 } 1514 } 1515 1516 if (def != NULL) { 1517 lock_release(); 1518 return defobj->relocbase + def->st_value; 1519 } 1520 1521 _rtld_error("Undefined symbol \"%s\"", name); 1522 lock_release(); 1523 return NULL; 1524 } 1525 1526 int 1527 dladdr(const void *addr, Dl_info *info) 1528 { 1529 const Obj_Entry *obj; 1530 const Elf_Sym *def; 1531 void *symbol_addr; 1532 unsigned long symoffset; 1533 1534 wlock_acquire(); 1535 obj = obj_from_addr(addr); 1536 if (obj == NULL) { 1537 _rtld_error("No shared object contains address"); 1538 lock_release(); 1539 return 0; 1540 } 1541 info->dli_fname = obj->path; 1542 info->dli_fbase = obj->mapbase; 1543 info->dli_saddr = (void *)0; 1544 info->dli_sname = NULL; 1545 1546 /* 1547 * Walk the symbol list looking for the symbol whose address is 1548 * closest to the address sent in. 1549 */ 1550 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1551 def = obj->symtab + symoffset; 1552 1553 /* 1554 * For skip the symbol if st_shndx is either SHN_UNDEF or 1555 * SHN_COMMON. 1556 */ 1557 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1558 continue; 1559 1560 /* 1561 * If the symbol is greater than the specified address, or if it 1562 * is further away from addr than the current nearest symbol, 1563 * then reject it. 1564 */ 1565 symbol_addr = obj->relocbase + def->st_value; 1566 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1567 continue; 1568 1569 /* Update our idea of the nearest symbol. */ 1570 info->dli_sname = obj->strtab + def->st_name; 1571 info->dli_saddr = symbol_addr; 1572 1573 /* Exact match? */ 1574 if (info->dli_saddr == addr) 1575 break; 1576 } 1577 lock_release(); 1578 return 1; 1579 } 1580 1581 static void 1582 linkmap_add(Obj_Entry *obj) 1583 { 1584 struct link_map *l = &obj->linkmap; 1585 struct link_map *prev; 1586 1587 obj->linkmap.l_name = obj->path; 1588 obj->linkmap.l_addr = obj->mapbase; 1589 obj->linkmap.l_ld = obj->dynamic; 1590 #ifdef __mips__ 1591 /* GDB needs load offset on MIPS to use the symbols */ 1592 obj->linkmap.l_offs = obj->relocbase; 1593 #endif 1594 1595 if (r_debug.r_map == NULL) { 1596 r_debug.r_map = l; 1597 return; 1598 } 1599 1600 /* 1601 * Scan to the end of the list, but not past the entry for the 1602 * dynamic linker, which we want to keep at the very end. 1603 */ 1604 for (prev = r_debug.r_map; 1605 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 1606 prev = prev->l_next) 1607 ; 1608 1609 /* Link in the new entry. */ 1610 l->l_prev = prev; 1611 l->l_next = prev->l_next; 1612 if (l->l_next != NULL) 1613 l->l_next->l_prev = l; 1614 prev->l_next = l; 1615 } 1616 1617 static void 1618 linkmap_delete(Obj_Entry *obj) 1619 { 1620 struct link_map *l = &obj->linkmap; 1621 1622 if (l->l_prev == NULL) { 1623 if ((r_debug.r_map = l->l_next) != NULL) 1624 l->l_next->l_prev = NULL; 1625 return; 1626 } 1627 1628 if ((l->l_prev->l_next = l->l_next) != NULL) 1629 l->l_next->l_prev = l->l_prev; 1630 } 1631 1632 /* 1633 * Function for the debugger to set a breakpoint on to gain control. 1634 */ 1635 void 1636 r_debug_state(void) 1637 { 1638 } 1639 1640 /* 1641 * Set a pointer variable in the main program to the given value. This 1642 * is used to set key variables such as "environ" before any of the 1643 * init functions are called. 1644 */ 1645 static void 1646 set_program_var(const char *name, const void *value) 1647 { 1648 const Obj_Entry *obj; 1649 unsigned long hash; 1650 1651 hash = elf_hash(name); 1652 for (obj = obj_main; obj != NULL; obj = obj->next) { 1653 const Elf_Sym *def; 1654 1655 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 1656 const void **addr; 1657 1658 addr = (const void **)(obj->relocbase + def->st_value); 1659 dbg("\"%s\": *%p <-- %p", name, addr, value); 1660 *addr = value; 1661 break; 1662 } 1663 } 1664 } 1665 1666 static const Elf_Sym * 1667 symlook_list(const char *name, unsigned long hash, Objlist *objlist, 1668 const Obj_Entry **defobj_out, bool in_plt) 1669 { 1670 const Elf_Sym *symp; 1671 const Elf_Sym *def; 1672 const Obj_Entry *defobj; 1673 const Objlist_Entry *elm; 1674 1675 def = NULL; 1676 defobj = NULL; 1677 STAILQ_FOREACH(elm, objlist, link) { 1678 if (elm->obj->mark == curmark) 1679 continue; 1680 elm->obj->mark = curmark; 1681 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 1682 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 1683 def = symp; 1684 defobj = elm->obj; 1685 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 1686 break; 1687 } 1688 } 1689 } 1690 if (def != NULL) 1691 *defobj_out = defobj; 1692 return def; 1693 } 1694 1695 /* 1696 * Search the symbol table of a single shared object for a symbol of 1697 * the given name. Returns a pointer to the symbol, or NULL if no 1698 * definition was found. 1699 * 1700 * The symbol's hash value is passed in for efficiency reasons; that 1701 * eliminates many recomputations of the hash value. 1702 */ 1703 const Elf_Sym * 1704 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 1705 bool in_plt) 1706 { 1707 if (obj->buckets != NULL) { 1708 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 1709 1710 while (symnum != STN_UNDEF) { 1711 const Elf_Sym *symp; 1712 const char *strp; 1713 1714 if (symnum >= obj->nchains) 1715 return NULL; /* Bad object */ 1716 symp = obj->symtab + symnum; 1717 strp = obj->strtab + symp->st_name; 1718 1719 if (strcmp(name, strp) == 0) 1720 return symp->st_shndx != SHN_UNDEF || 1721 (!in_plt && symp->st_value != 0 && 1722 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 1723 1724 symnum = obj->chains[symnum]; 1725 } 1726 } 1727 return NULL; 1728 } 1729 1730 static void 1731 trace_loaded_objects(Obj_Entry *obj) 1732 { 1733 char *fmt1, *fmt2, *fmt, *main_local; 1734 int c; 1735 1736 if ((main_local = getenv("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 1737 main_local = ""; 1738 1739 if ((fmt1 = getenv("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 1740 fmt1 = "\t%o => %p (%x)\n"; 1741 1742 if ((fmt2 = getenv("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 1743 fmt2 = "\t%o (%x)\n"; 1744 1745 for (; obj; obj = obj->next) { 1746 Needed_Entry *needed; 1747 char *name, *path; 1748 bool is_lib; 1749 1750 for (needed = obj->needed; needed; needed = needed->next) { 1751 if (needed->obj != NULL) { 1752 if (needed->obj->traced) 1753 continue; 1754 needed->obj->traced = true; 1755 path = needed->obj->path; 1756 } else 1757 path = "not found"; 1758 1759 name = (char *)obj->strtab + needed->name; 1760 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 1761 1762 fmt = is_lib ? fmt1 : fmt2; 1763 while ((c = *fmt++) != '\0') { 1764 switch (c) { 1765 default: 1766 putchar(c); 1767 continue; 1768 case '\\': 1769 switch (c = *fmt) { 1770 case '\0': 1771 continue; 1772 case 'n': 1773 putchar('\n'); 1774 break; 1775 case 't': 1776 putchar('\t'); 1777 break; 1778 } 1779 break; 1780 case '%': 1781 switch (c = *fmt) { 1782 case '\0': 1783 continue; 1784 case '%': 1785 default: 1786 putchar(c); 1787 break; 1788 case 'A': 1789 printf("%s", main_local); 1790 break; 1791 case 'a': 1792 printf("%s", obj_main->path); 1793 break; 1794 case 'o': 1795 printf("%s", name); 1796 break; 1797 #if 0 1798 case 'm': 1799 printf("%d", sodp->sod_major); 1800 break; 1801 case 'n': 1802 printf("%d", sodp->sod_minor); 1803 break; 1804 #endif 1805 case 'p': 1806 printf("%s", path); 1807 break; 1808 case 'x': 1809 printf("%p", needed->obj ? needed->obj->mapbase : 0); 1810 break; 1811 } 1812 break; 1813 } 1814 ++fmt; 1815 } 1816 } 1817 } 1818 } 1819 1820 /* 1821 * Unload a dlopened object and its dependencies from memory and from 1822 * our data structures. It is assumed that the DAG rooted in the 1823 * object has already been unreferenced, and that the object has a 1824 * reference count of 0. 1825 */ 1826 static void 1827 unload_object(Obj_Entry *root) 1828 { 1829 Obj_Entry *obj; 1830 Obj_Entry **linkp; 1831 Objlist_Entry *elm; 1832 1833 assert(root->refcount == 0); 1834 1835 /* Remove the DAG from all objects' DAG lists. */ 1836 STAILQ_FOREACH(elm, &root->dagmembers , link) 1837 objlist_remove(&elm->obj->dldags, root); 1838 1839 /* Remove the DAG from the RTLD_GLOBAL list. */ 1840 objlist_remove(&list_global, root); 1841 1842 /* Unmap all objects that are no longer referenced. */ 1843 linkp = &obj_list->next; 1844 while ((obj = *linkp) != NULL) { 1845 if (obj->refcount == 0) { 1846 dbg("unloading \"%s\"", obj->path); 1847 munmap(obj->mapbase, obj->mapsize); 1848 linkmap_delete(obj); 1849 *linkp = obj->next; 1850 obj_free(obj); 1851 } else 1852 linkp = &obj->next; 1853 } 1854 obj_tail = linkp; 1855 } 1856 1857 static void 1858 unref_dag(Obj_Entry *root) 1859 { 1860 const Needed_Entry *needed; 1861 1862 assert(root->refcount != 0); 1863 root->refcount--; 1864 if (root->refcount == 0) 1865 for (needed = root->needed; needed != NULL; needed = needed->next) 1866 if (needed->obj != NULL) 1867 unref_dag(needed->obj); 1868 } 1869 1870 /* 1871 * Non-mallocing printf, for use by malloc itself. 1872 * XXX - This doesn't belong in this module. 1873 */ 1874 void 1875 xprintf(const char *fmt, ...) 1876 { 1877 char buf[256]; 1878 va_list ap; 1879 1880 va_start(ap, fmt); 1881 vsprintf(buf, fmt, ap); 1882 (void)write(1, buf, strlen(buf)); 1883 va_end(ap); 1884 } 1885