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 void prebind(void *); 102 static int relocate_objects(Obj_Entry *, bool); 103 static void rtld_exit(void); 104 static char *search_library_path(const char *, const char *); 105 static void set_program_var(const char *, const void *); 106 static const Elf_Sym *symlook_list(const char *, unsigned long, 107 Objlist *, const Obj_Entry **, bool in_plt); 108 static void trace_loaded_objects(Obj_Entry *obj); 109 static void unload_object(Obj_Entry *); 110 static void unref_dag(Obj_Entry *); 111 112 void r_debug_state(void); 113 void xprintf(const char *, ...); 114 115 /* 116 * Data declarations. 117 */ 118 static char *error_message; /* Message for dlerror(), or NULL */ 119 struct r_debug r_debug; /* for GDB; */ 120 static bool trust; /* False for setuid and setgid programs */ 121 static char *ld_bind_now; /* Environment variable for immediate binding */ 122 static char *ld_debug; /* Environment variable for debugging */ 123 static char *ld_library_path; /* Environment variable for search path */ 124 static char *ld_preload; /* Environment variable for libraries to 125 load first */ 126 static char *ld_tracing; /* Called from ldd to print libs */ 127 static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 128 static Obj_Entry **obj_tail; /* Link field of last object in list */ 129 static Obj_Entry *obj_main; /* The main program shared object */ 130 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 131 static unsigned long curmark; /* Current mark value */ 132 133 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 134 STAILQ_HEAD_INITIALIZER(list_global); 135 static Objlist list_main = /* Objects loaded at program startup */ 136 STAILQ_HEAD_INITIALIZER(list_main); 137 138 static LockInfo lockinfo; 139 140 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 141 142 #define GDB_STATE(s) r_debug.r_state = s; r_debug_state(); 143 144 extern Elf_Dyn _DYNAMIC; 145 #pragma weak _DYNAMIC 146 147 /* 148 * These are the functions the dynamic linker exports to application 149 * programs. They are the only symbols the dynamic linker is willing 150 * to export from itself. 151 */ 152 static func_ptr_type exports[] = { 153 (func_ptr_type) &_rtld_error, 154 (func_ptr_type) &dlclose, 155 (func_ptr_type) &dlerror, 156 (func_ptr_type) &dlopen, 157 (func_ptr_type) &dlsym, 158 (func_ptr_type) &dladdr, 159 (func_ptr_type) &dllockinit, 160 NULL 161 }; 162 163 /* 164 * Global declarations normally provided by crt1. The dynamic linker is 165 * not built with crt1, so we have to provide them ourselves. 166 */ 167 char *__progname; 168 char **environ; 169 170 static __inline void 171 rlock_acquire(void) 172 { 173 lockinfo.rlock_acquire(lockinfo.thelock); 174 } 175 176 static __inline void 177 wlock_acquire(void) 178 { 179 lockinfo.wlock_acquire(lockinfo.thelock); 180 } 181 182 static __inline void 183 lock_release(void) 184 { 185 lockinfo.lock_release(lockinfo.thelock); 186 } 187 188 /* 189 * Main entry point for dynamic linking. The first argument is the 190 * stack pointer. The stack is expected to be laid out as described 191 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 192 * Specifically, the stack pointer points to a word containing 193 * ARGC. Following that in the stack is a null-terminated sequence 194 * of pointers to argument strings. Then comes a null-terminated 195 * sequence of pointers to environment strings. Finally, there is a 196 * sequence of "auxiliary vector" entries. 197 * 198 * The second argument points to a place to store the dynamic linker's 199 * exit procedure pointer and the third to a place to store the main 200 * program's object. 201 * 202 * The return value is the main program's entry point. 203 */ 204 func_ptr_type 205 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 206 { 207 Elf_Auxinfo *aux_info[AT_COUNT]; 208 int i; 209 int argc; 210 char **argv; 211 char **env; 212 Elf_Auxinfo *aux; 213 Elf_Auxinfo *auxp; 214 const char *argv0; 215 Obj_Entry *obj; 216 Funclist initlist; 217 218 /* 219 * On entry, the dynamic linker itself has not been relocated yet. 220 * Be very careful not to reference any global data until after 221 * init_rtld has returned. It is OK to reference file-scope statics 222 * and string constants, and to call static and global functions. 223 */ 224 225 /* Find the auxiliary vector on the stack. */ 226 argc = *sp++; 227 argv = (char **) sp; 228 sp += argc + 1; /* Skip over arguments and NULL terminator */ 229 env = (char **) sp; 230 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 231 ; 232 aux = (Elf_Auxinfo *) sp; 233 234 /* Digest the auxiliary vector. */ 235 for (i = 0; i < AT_COUNT; i++) 236 aux_info[i] = NULL; 237 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 238 if (auxp->a_type < AT_COUNT) 239 aux_info[auxp->a_type] = auxp; 240 } 241 242 /* Initialize and relocate ourselves. */ 243 assert(aux_info[AT_BASE] != NULL); 244 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 245 246 __progname = obj_rtld.path; 247 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 248 environ = env; 249 250 trust = geteuid() == getuid() && getegid() == getgid(); 251 252 ld_bind_now = getenv("LD_BIND_NOW"); 253 if (trust) { 254 ld_debug = getenv("LD_DEBUG"); 255 ld_library_path = getenv("LD_LIBRARY_PATH"); 256 ld_preload = getenv("LD_PRELOAD"); 257 } 258 ld_tracing = getenv("LD_TRACE_LOADED_OBJECTS"); 259 260 if (ld_debug != NULL && *ld_debug != '\0') 261 debug = 1; 262 dbg("%s is initialized, base address = %p", __progname, 263 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 264 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 265 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 266 267 /* 268 * Load the main program, or process its program header if it is 269 * already loaded. 270 */ 271 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 272 int fd = aux_info[AT_EXECFD]->a_un.a_val; 273 dbg("loading main program"); 274 obj_main = map_object(fd, argv0, NULL); 275 close(fd); 276 if (obj_main == NULL) 277 die(); 278 } else { /* Main program already loaded. */ 279 const Elf_Phdr *phdr; 280 int phnum; 281 caddr_t entry; 282 283 dbg("processing main program's program header"); 284 assert(aux_info[AT_PHDR] != NULL); 285 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 286 assert(aux_info[AT_PHNUM] != NULL); 287 phnum = aux_info[AT_PHNUM]->a_un.a_val; 288 assert(aux_info[AT_PHENT] != NULL); 289 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 290 assert(aux_info[AT_ENTRY] != NULL); 291 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 292 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 293 die(); 294 } 295 296 obj_main->path = xstrdup(argv0); 297 obj_main->mainprog = true; 298 299 /* 300 * Get the actual dynamic linker pathname from the executable if 301 * possible. (It should always be possible.) That ensures that 302 * gdb will find the right dynamic linker even if a non-standard 303 * one is being used. 304 */ 305 if (obj_main->interp != NULL && 306 strcmp(obj_main->interp, obj_rtld.path) != 0) { 307 free(obj_rtld.path); 308 obj_rtld.path = xstrdup(obj_main->interp); 309 } 310 311 digest_dynamic(obj_main); 312 313 linkmap_add(obj_main); 314 linkmap_add(&obj_rtld); 315 316 /* Link the main program into the list of objects. */ 317 *obj_tail = obj_main; 318 obj_tail = &obj_main->next; 319 obj_main->refcount++; 320 321 /* Initialize a fake symbol for resolving undefined weak references. */ 322 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 323 sym_zero.st_shndx = SHN_ABS; 324 325 dbg("loading LD_PRELOAD libraries"); 326 if (load_preload_objects() == -1) 327 die(); 328 329 dbg("loading needed objects"); 330 if (load_needed_objects(obj_main) == -1) 331 die(); 332 333 /* 334 * Make a list of all objects loaded at startup. Also construct 335 * the list of init functions to call, in reverse order. 336 */ 337 funclist_init(&initlist); 338 for (obj = obj_list; obj != NULL; obj = obj->next) { 339 objlist_add(&list_main, obj); 340 if (obj->init != NULL && !obj->mainprog) 341 funclist_push_head(&initlist, obj->init); 342 } 343 344 if (ld_tracing) { /* We're done */ 345 trace_loaded_objects(obj_main); 346 exit(0); 347 } 348 349 if (relocate_objects(obj_main, 350 ld_bind_now != NULL && *ld_bind_now != '\0') == -1) 351 die(); 352 353 dbg("doing copy relocations"); 354 if (do_copy_relocations(obj_main) == -1) 355 die(); 356 357 dbg("initializing key program variables"); 358 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 359 set_program_var("environ", env); 360 361 dbg("initializing default locks"); 362 dllockinit(NULL, NULL, NULL, NULL, NULL, NULL, NULL); 363 364 r_debug_state(); /* say hello to gdb! */ 365 366 funclist_call(&initlist); 367 wlock_acquire(); 368 funclist_clear(&initlist); 369 lock_release(); 370 371 dbg("transferring control to program entry point = %p", obj_main->entry); 372 373 /* Return the exit procedure and the program entry point. */ 374 *exit_proc = rtld_exit; 375 *objp = obj_main; 376 return (func_ptr_type) obj_main->entry; 377 } 378 379 Elf_Addr 380 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 381 { 382 const Elf_Rel *rel; 383 const Elf_Sym *def; 384 const Obj_Entry *defobj; 385 Elf_Addr *where; 386 Elf_Addr target; 387 388 wlock_acquire(); 389 if (obj->pltrel) 390 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 391 else 392 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 393 394 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 395 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true); 396 if (def == NULL) 397 die(); 398 399 target = (Elf_Addr)(defobj->relocbase + def->st_value); 400 401 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 402 defobj->strtab + def->st_name, basename(obj->path), 403 (void *)target, basename(defobj->path)); 404 405 reloc_jmpslot(where, target); 406 lock_release(); 407 return target; 408 } 409 410 /* 411 * Error reporting function. Use it like printf. If formats the message 412 * into a buffer, and sets things up so that the next call to dlerror() 413 * will return the message. 414 */ 415 void 416 _rtld_error(const char *fmt, ...) 417 { 418 static char buf[512]; 419 va_list ap; 420 421 va_start(ap, fmt); 422 vsnprintf(buf, sizeof buf, fmt, ap); 423 error_message = buf; 424 va_end(ap); 425 } 426 427 static const char * 428 basename(const char *name) 429 { 430 const char *p = strrchr(name, '/'); 431 return p != NULL ? p + 1 : name; 432 } 433 434 static void 435 die(void) 436 { 437 const char *msg = dlerror(); 438 439 if (msg == NULL) 440 msg = "Fatal error"; 441 errx(1, "%s", msg); 442 } 443 444 /* 445 * Process a shared object's DYNAMIC section, and save the important 446 * information in its Obj_Entry structure. 447 */ 448 static void 449 digest_dynamic(Obj_Entry *obj) 450 { 451 const Elf_Dyn *dynp; 452 Needed_Entry **needed_tail = &obj->needed; 453 const Elf_Dyn *dyn_rpath = NULL; 454 int plttype = DT_REL; 455 456 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 457 switch (dynp->d_tag) { 458 459 case DT_REL: 460 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 461 break; 462 463 case DT_RELSZ: 464 obj->relsize = dynp->d_un.d_val; 465 break; 466 467 case DT_RELENT: 468 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 469 break; 470 471 case DT_JMPREL: 472 obj->pltrel = (const Elf_Rel *) 473 (obj->relocbase + dynp->d_un.d_ptr); 474 break; 475 476 case DT_PLTRELSZ: 477 obj->pltrelsize = dynp->d_un.d_val; 478 break; 479 480 case DT_RELA: 481 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 482 break; 483 484 case DT_RELASZ: 485 obj->relasize = dynp->d_un.d_val; 486 break; 487 488 case DT_RELAENT: 489 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 490 break; 491 492 case DT_PLTREL: 493 plttype = dynp->d_un.d_val; 494 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 495 break; 496 497 case DT_SYMTAB: 498 obj->symtab = (const Elf_Sym *) 499 (obj->relocbase + dynp->d_un.d_ptr); 500 break; 501 502 case DT_SYMENT: 503 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 504 break; 505 506 case DT_STRTAB: 507 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 508 break; 509 510 case DT_STRSZ: 511 obj->strsize = dynp->d_un.d_val; 512 break; 513 514 case DT_HASH: 515 { 516 const Elf_Addr *hashtab = (const Elf_Addr *) 517 (obj->relocbase + dynp->d_un.d_ptr); 518 obj->nbuckets = hashtab[0]; 519 obj->nchains = hashtab[1]; 520 obj->buckets = hashtab + 2; 521 obj->chains = obj->buckets + obj->nbuckets; 522 } 523 break; 524 525 case DT_NEEDED: 526 if (!obj->rtld) { 527 Needed_Entry *nep = NEW(Needed_Entry); 528 nep->name = dynp->d_un.d_val; 529 nep->obj = NULL; 530 nep->next = NULL; 531 532 *needed_tail = nep; 533 needed_tail = &nep->next; 534 } 535 break; 536 537 case DT_PLTGOT: 538 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 539 break; 540 541 case DT_TEXTREL: 542 obj->textrel = true; 543 break; 544 545 case DT_SYMBOLIC: 546 obj->symbolic = true; 547 break; 548 549 case DT_RPATH: 550 /* 551 * We have to wait until later to process this, because we 552 * might not have gotten the address of the string table yet. 553 */ 554 dyn_rpath = dynp; 555 break; 556 557 case DT_SONAME: 558 /* Not used by the dynamic linker. */ 559 break; 560 561 case DT_INIT: 562 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 563 break; 564 565 case DT_FINI: 566 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 567 break; 568 569 case DT_DEBUG: 570 /* XXX - not implemented yet */ 571 dbg("Filling in DT_DEBUG entry"); 572 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 573 break; 574 575 default: 576 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag); 577 break; 578 } 579 } 580 581 obj->traced = false; 582 583 if (plttype == DT_RELA) { 584 obj->pltrela = (const Elf_Rela *) obj->pltrel; 585 obj->pltrel = NULL; 586 obj->pltrelasize = obj->pltrelsize; 587 obj->pltrelsize = 0; 588 } 589 590 if (dyn_rpath != NULL) 591 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 592 } 593 594 /* 595 * Process a shared object's program header. This is used only for the 596 * main program, when the kernel has already loaded the main program 597 * into memory before calling the dynamic linker. It creates and 598 * returns an Obj_Entry structure. 599 */ 600 static Obj_Entry * 601 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 602 { 603 Obj_Entry *obj; 604 const Elf_Phdr *phlimit = phdr + phnum; 605 const Elf_Phdr *ph; 606 int nsegs = 0; 607 608 obj = obj_new(); 609 for (ph = phdr; ph < phlimit; ph++) { 610 switch (ph->p_type) { 611 612 case PT_PHDR: 613 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 614 _rtld_error("%s: invalid PT_PHDR", path); 615 return NULL; 616 } 617 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 618 obj->phsize = ph->p_memsz; 619 break; 620 621 case PT_INTERP: 622 obj->interp = (const char *) ph->p_vaddr; 623 break; 624 625 case PT_LOAD: 626 if (nsegs >= 2) { 627 _rtld_error("%s: too many PT_LOAD segments", path); 628 return NULL; 629 } 630 if (nsegs == 0) { /* First load segment */ 631 obj->vaddrbase = trunc_page(ph->p_vaddr); 632 obj->mapbase = (caddr_t) obj->vaddrbase; 633 obj->relocbase = obj->mapbase - obj->vaddrbase; 634 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 635 obj->vaddrbase; 636 } else { /* Last load segment */ 637 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 638 obj->vaddrbase; 639 } 640 nsegs++; 641 break; 642 643 case PT_DYNAMIC: 644 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 645 break; 646 } 647 } 648 if (nsegs < 2) { 649 _rtld_error("%s: too few PT_LOAD segments", path); 650 return NULL; 651 } 652 653 obj->entry = entry; 654 return obj; 655 } 656 657 static Obj_Entry * 658 dlcheck(void *handle) 659 { 660 Obj_Entry *obj; 661 662 for (obj = obj_list; obj != NULL; obj = obj->next) 663 if (obj == (Obj_Entry *) handle) 664 break; 665 666 if (obj == NULL || obj->dl_refcount == 0) { 667 _rtld_error("Invalid shared object handle %p", handle); 668 return NULL; 669 } 670 return obj; 671 } 672 673 /* 674 * Hash function for symbol table lookup. Don't even think about changing 675 * this. It is specified by the System V ABI. 676 */ 677 unsigned long 678 elf_hash(const char *name) 679 { 680 const unsigned char *p = (const unsigned char *) name; 681 unsigned long h = 0; 682 unsigned long g; 683 684 while (*p != '\0') { 685 h = (h << 4) + *p++; 686 if ((g = h & 0xf0000000) != 0) 687 h ^= g >> 24; 688 h &= ~g; 689 } 690 return h; 691 } 692 693 /* 694 * Find the library with the given name, and return its full pathname. 695 * The returned string is dynamically allocated. Generates an error 696 * message and returns NULL if the library cannot be found. 697 * 698 * If the second argument is non-NULL, then it refers to an already- 699 * loaded shared object, whose library search path will be searched. 700 * 701 * The search order is: 702 * rpath in the referencing file 703 * LD_LIBRARY_PATH 704 * ldconfig hints 705 * /usr/lib 706 */ 707 static char * 708 find_library(const char *name, const Obj_Entry *refobj) 709 { 710 char *pathname; 711 712 if (strchr(name, '/') != NULL) { /* Hard coded pathname */ 713 if (name[0] != '/' && !trust) { 714 _rtld_error("Absolute pathname required for shared object \"%s\"", 715 name); 716 return NULL; 717 } 718 return xstrdup(name); 719 } 720 721 dbg(" Searching for \"%s\"", name); 722 723 if ((refobj != NULL && 724 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 725 (pathname = search_library_path(name, ld_library_path)) != NULL || 726 (pathname = search_library_path(name, gethints())) != NULL || 727 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 728 return pathname; 729 730 _rtld_error("Shared object \"%s\" not found", name); 731 return NULL; 732 } 733 734 /* 735 * Given a symbol number in a referencing object, find the corresponding 736 * definition of the symbol. Returns a pointer to the symbol, or NULL if 737 * no definition was found. Returns a pointer to the Obj_Entry of the 738 * defining object via the reference parameter DEFOBJ_OUT. 739 */ 740 const Elf_Sym * 741 find_symdef(unsigned long symnum, Obj_Entry *refobj, 742 const Obj_Entry **defobj_out, bool in_plt) 743 { 744 const Elf_Sym *ref; 745 const Elf_Sym *def; 746 const Elf_Sym *symp; 747 const Obj_Entry *obj; 748 const Obj_Entry *defobj; 749 const Objlist_Entry *elm; 750 const char *name; 751 unsigned long hash; 752 753 ref = refobj->symtab + symnum; 754 name = refobj->strtab + ref->st_name; 755 hash = elf_hash(name); 756 def = NULL; 757 defobj = NULL; 758 curmark++; 759 760 if (refobj->symbolic) { /* Look first in the referencing object */ 761 symp = symlook_obj(name, hash, refobj, in_plt); 762 refobj->mark = curmark; 763 if (symp != NULL) { 764 def = symp; 765 defobj = refobj; 766 } 767 } 768 769 /* Search all objects loaded at program start up. */ 770 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 771 symp = symlook_list(name, hash, &list_main, &obj, in_plt); 772 if (symp != NULL && 773 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 774 def = symp; 775 defobj = obj; 776 } 777 } 778 779 /* Search all dlopened DAGs containing the referencing object. */ 780 STAILQ_FOREACH(elm, &refobj->dldags, link) { 781 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 782 break; 783 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt); 784 if (symp != NULL && 785 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 786 def = symp; 787 defobj = obj; 788 } 789 } 790 791 /* Search all RTLD_GLOBAL objects. */ 792 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 793 symp = symlook_list(name, hash, &list_global, &obj, in_plt); 794 if (symp != NULL && 795 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 796 def = symp; 797 defobj = obj; 798 } 799 } 800 801 /* 802 * Search the dynamic linker itself, and possibly resolve the 803 * symbol from there. This is how the application links to 804 * dynamic linker services such as dlopen. Only the values listed 805 * in the "exports" array can be resolved from the dynamic linker. 806 */ 807 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 808 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 809 if (symp != NULL && is_exported(symp)) { 810 def = symp; 811 defobj = &obj_rtld; 812 } 813 } 814 815 /* 816 * If we found no definition and the reference is weak, treat the 817 * symbol as having the value zero. 818 */ 819 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 820 def = &sym_zero; 821 defobj = obj_main; 822 } 823 824 if (def != NULL) 825 *defobj_out = defobj; 826 else 827 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 828 return def; 829 } 830 831 static void 832 funclist_call(Funclist *list) 833 { 834 Funclist_Entry *elm; 835 836 STAILQ_FOREACH(elm, list, link) { 837 dbg("calling init/fini function at %p", elm->func); 838 (*elm->func)(); 839 } 840 } 841 842 static void 843 funclist_clear(Funclist *list) 844 { 845 Funclist_Entry *elm; 846 847 while (!STAILQ_EMPTY(list)) { 848 elm = STAILQ_FIRST(list); 849 STAILQ_REMOVE_HEAD(list, link); 850 free(elm); 851 } 852 } 853 854 static void 855 funclist_init(Funclist *list) 856 { 857 STAILQ_INIT(list); 858 } 859 860 static void 861 funclist_push_head(Funclist *list, InitFunc func) 862 { 863 Funclist_Entry *elm; 864 865 elm = NEW(Funclist_Entry); 866 elm->func = func; 867 STAILQ_INSERT_HEAD(list, elm, link); 868 } 869 870 static void 871 funclist_push_tail(Funclist *list, InitFunc func) 872 { 873 Funclist_Entry *elm; 874 875 elm = NEW(Funclist_Entry); 876 elm->func = func; 877 STAILQ_INSERT_TAIL(list, elm, link); 878 } 879 880 /* 881 * Return the search path from the ldconfig hints file, reading it if 882 * necessary. Returns NULL if there are problems with the hints file, 883 * or if the search path there is empty. 884 */ 885 static const char * 886 gethints(void) 887 { 888 static char *hints; 889 890 if (hints == NULL) { 891 int fd; 892 struct elfhints_hdr hdr; 893 char *p; 894 895 /* Keep from trying again in case the hints file is bad. */ 896 hints = ""; 897 898 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 899 return NULL; 900 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 901 hdr.magic != ELFHINTS_MAGIC || 902 hdr.version != 1) { 903 close(fd); 904 return NULL; 905 } 906 p = xmalloc(hdr.dirlistlen + 1); 907 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 908 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { 909 free(p); 910 close(fd); 911 return NULL; 912 } 913 hints = p; 914 close(fd); 915 } 916 return hints[0] != '\0' ? hints : NULL; 917 } 918 919 static void 920 init_dag(Obj_Entry *root) 921 { 922 curmark++; 923 init_dag1(root, root); 924 } 925 926 static void 927 init_dag1(Obj_Entry *root, Obj_Entry *obj) 928 { 929 const Needed_Entry *needed; 930 931 if (obj->mark == curmark) 932 return; 933 obj->mark = curmark; 934 objlist_add(&obj->dldags, root); 935 objlist_add(&root->dagmembers, obj); 936 for (needed = obj->needed; needed != NULL; needed = needed->next) 937 if (needed->obj != NULL) 938 init_dag1(root, needed->obj); 939 } 940 941 /* 942 * Initialize the dynamic linker. The argument is the address at which 943 * the dynamic linker has been mapped into memory. The primary task of 944 * this function is to relocate the dynamic linker. 945 */ 946 static void 947 init_rtld(caddr_t mapbase) 948 { 949 /* 950 * Conjure up an Obj_Entry structure for the dynamic linker. 951 * 952 * The "path" member is supposed to be dynamically-allocated, but we 953 * aren't yet initialized sufficiently to do that. Below we will 954 * replace the static version with a dynamically-allocated copy. 955 */ 956 obj_rtld.path = PATH_RTLD; 957 obj_rtld.rtld = true; 958 obj_rtld.mapbase = mapbase; 959 #ifdef PIC 960 obj_rtld.relocbase = mapbase; 961 #endif 962 if (&_DYNAMIC != 0) { 963 obj_rtld.dynamic = rtld_dynamic(&obj_rtld); 964 digest_dynamic(&obj_rtld); 965 assert(obj_rtld.needed == NULL); 966 assert(!obj_rtld.textrel); 967 968 /* 969 * Temporarily put the dynamic linker entry into the object list, so 970 * that symbols can be found. 971 */ 972 obj_list = &obj_rtld; 973 obj_tail = &obj_rtld.next; 974 975 relocate_objects(&obj_rtld, true); 976 } 977 978 /* Make the object list empty again. */ 979 obj_list = NULL; 980 obj_tail = &obj_list; 981 982 /* Replace the path with a dynamically allocated copy. */ 983 obj_rtld.path = xstrdup(obj_rtld.path); 984 985 r_debug.r_brk = r_debug_state; 986 r_debug.r_state = RT_CONSISTENT; 987 } 988 989 static bool 990 is_exported(const Elf_Sym *def) 991 { 992 func_ptr_type value; 993 const func_ptr_type *p; 994 995 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value); 996 for (p = exports; *p != NULL; p++) 997 if (*p == value) 998 return true; 999 return false; 1000 } 1001 1002 /* 1003 * Given a shared object, traverse its list of needed objects, and load 1004 * each of them. Returns 0 on success. Generates an error message and 1005 * returns -1 on failure. 1006 */ 1007 static int 1008 load_needed_objects(Obj_Entry *first) 1009 { 1010 Obj_Entry *obj; 1011 1012 for (obj = first; obj != NULL; obj = obj->next) { 1013 Needed_Entry *needed; 1014 1015 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1016 const char *name = obj->strtab + needed->name; 1017 char *path = find_library(name, obj); 1018 1019 needed->obj = NULL; 1020 if (path == NULL && !ld_tracing) 1021 return -1; 1022 1023 if (path) { 1024 needed->obj = load_object(path); 1025 if (needed->obj == NULL && !ld_tracing) 1026 return -1; /* XXX - cleanup */ 1027 } 1028 } 1029 } 1030 1031 return 0; 1032 } 1033 1034 static int 1035 load_preload_objects(void) 1036 { 1037 char *p = ld_preload; 1038 static const char delim[] = " \t:;"; 1039 1040 if (p == NULL) 1041 return NULL; 1042 1043 p += strspn(p, delim); 1044 while (*p != '\0') { 1045 size_t len = strcspn(p, delim); 1046 char *path; 1047 char savech; 1048 1049 savech = p[len]; 1050 p[len] = '\0'; 1051 if ((path = find_library(p, NULL)) == NULL) 1052 return -1; 1053 if (load_object(path) == NULL) 1054 return -1; /* XXX - cleanup */ 1055 p[len] = savech; 1056 p += len; 1057 p += strspn(p, delim); 1058 } 1059 return 0; 1060 } 1061 1062 /* 1063 * Load a shared object into memory, if it is not already loaded. The 1064 * argument must be a string allocated on the heap. This function assumes 1065 * responsibility for freeing it when necessary. 1066 * 1067 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1068 * on failure. 1069 */ 1070 static Obj_Entry * 1071 load_object(char *path) 1072 { 1073 Obj_Entry *obj; 1074 int fd = -1; 1075 struct stat sb; 1076 1077 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1078 if (strcmp(obj->path, path) == 0) 1079 break; 1080 1081 /* 1082 * If we didn't find a match by pathname, open the file and check 1083 * again by device and inode. This avoids false mismatches caused 1084 * by multiple links or ".." in pathnames. 1085 * 1086 * To avoid a race, we open the file and use fstat() rather than 1087 * using stat(). 1088 */ 1089 if (obj == NULL) { 1090 if ((fd = open(path, O_RDONLY)) == -1) { 1091 _rtld_error("Cannot open \"%s\"", path); 1092 return NULL; 1093 } 1094 if (fstat(fd, &sb) == -1) { 1095 _rtld_error("Cannot fstat \"%s\"", path); 1096 close(fd); 1097 return NULL; 1098 } 1099 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1100 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) { 1101 close(fd); 1102 break; 1103 } 1104 } 1105 } 1106 1107 if (obj == NULL) { /* First use of this object, so we must map it in */ 1108 dbg("loading \"%s\"", path); 1109 obj = map_object(fd, path, &sb); 1110 close(fd); 1111 if (obj == NULL) { 1112 free(path); 1113 return NULL; 1114 } 1115 1116 obj->path = path; 1117 digest_dynamic(obj); 1118 1119 *obj_tail = obj; 1120 obj_tail = &obj->next; 1121 linkmap_add(obj); /* for GDB */ 1122 1123 dbg(" %p .. %p: %s", obj->mapbase, 1124 obj->mapbase + obj->mapsize - 1, obj->path); 1125 if (obj->textrel) 1126 dbg(" WARNING: %s has impure text", obj->path); 1127 } else 1128 free(path); 1129 1130 obj->refcount++; 1131 return obj; 1132 } 1133 1134 static void 1135 lock_nop(void *lock) 1136 { 1137 } 1138 1139 static Obj_Entry * 1140 obj_from_addr(const void *addr) 1141 { 1142 unsigned long endhash; 1143 Obj_Entry *obj; 1144 1145 endhash = elf_hash(END_SYM); 1146 for (obj = obj_list; obj != NULL; obj = obj->next) { 1147 const Elf_Sym *endsym; 1148 1149 if (addr < (void *) obj->mapbase) 1150 continue; 1151 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL) 1152 continue; /* No "end" symbol?! */ 1153 if (addr < (void *) (obj->relocbase + endsym->st_value)) 1154 return obj; 1155 } 1156 return NULL; 1157 } 1158 1159 static void 1160 objlist_add(Objlist *list, Obj_Entry *obj) 1161 { 1162 Objlist_Entry *elm; 1163 1164 elm = NEW(Objlist_Entry); 1165 elm->obj = obj; 1166 STAILQ_INSERT_TAIL(list, elm, link); 1167 } 1168 1169 static Objlist_Entry * 1170 objlist_find(Objlist *list, const Obj_Entry *obj) 1171 { 1172 Objlist_Entry *elm; 1173 1174 STAILQ_FOREACH(elm, list, link) 1175 if (elm->obj == obj) 1176 return elm; 1177 return NULL; 1178 } 1179 1180 static void 1181 objlist_remove(Objlist *list, Obj_Entry *obj) 1182 { 1183 Objlist_Entry *elm; 1184 1185 if ((elm = objlist_find(list, obj)) != NULL) { 1186 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1187 free(elm); 1188 } 1189 } 1190 1191 /* 1192 * Relocate newly-loaded shared objects. The argument is a pointer to 1193 * the Obj_Entry for the first such object. All objects from the first 1194 * to the end of the list of objects are relocated. Returns 0 on success, 1195 * or -1 on failure. 1196 */ 1197 static int 1198 relocate_objects(Obj_Entry *first, bool bind_now) 1199 { 1200 Obj_Entry *obj; 1201 1202 for (obj = first; obj != NULL; obj = obj->next) { 1203 if (obj != &obj_rtld) 1204 dbg("relocating \"%s\"", obj->path); 1205 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1206 obj->symtab == NULL || obj->strtab == NULL) { 1207 _rtld_error("%s: Shared object has no run-time symbol table", 1208 obj->path); 1209 return -1; 1210 } 1211 1212 if (obj->textrel) { 1213 /* There are relocations to the write-protected text segment. */ 1214 if (mprotect(obj->mapbase, obj->textsize, 1215 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1216 _rtld_error("%s: Cannot write-enable text segment: %s", 1217 obj->path, strerror(errno)); 1218 return -1; 1219 } 1220 } 1221 1222 /* Process the non-PLT relocations. */ 1223 if (reloc_non_plt(obj, &obj_rtld)) 1224 return -1; 1225 1226 if (obj->textrel) { /* Re-protected the text segment. */ 1227 if (mprotect(obj->mapbase, obj->textsize, 1228 PROT_READ|PROT_EXEC) == -1) { 1229 _rtld_error("%s: Cannot write-protect text segment: %s", 1230 obj->path, strerror(errno)); 1231 return -1; 1232 } 1233 } 1234 1235 /* Process the PLT relocations. */ 1236 if (reloc_plt(obj) == -1) 1237 return -1; 1238 /* Relocate the jump slots if we are doing immediate binding. */ 1239 if (bind_now) 1240 if (reloc_jmpslots(obj) == -1) 1241 return -1; 1242 1243 1244 /* 1245 * Set up the magic number and version in the Obj_Entry. These 1246 * were checked in the crt1.o from the original ElfKit, so we 1247 * set them for backward compatibility. 1248 */ 1249 obj->magic = RTLD_MAGIC; 1250 obj->version = RTLD_VERSION; 1251 1252 /* Set the special PLT or GOT entries. */ 1253 init_pltgot(obj); 1254 } 1255 1256 return 0; 1257 } 1258 1259 /* 1260 * Cleanup procedure. It will be called (by the atexit mechanism) just 1261 * before the process exits. 1262 */ 1263 static void 1264 rtld_exit(void) 1265 { 1266 Obj_Entry *obj; 1267 1268 dbg("rtld_exit()"); 1269 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1270 if (obj->fini != NULL) 1271 (*obj->fini)(); 1272 } 1273 1274 static char * 1275 search_library_path(const char *name, const char *path) 1276 { 1277 size_t namelen = strlen(name); 1278 const char *p = path; 1279 1280 if (p == NULL) 1281 return NULL; 1282 1283 p += strspn(p, ":;"); 1284 while (*p != '\0') { 1285 size_t len = strcspn(p, ":;"); 1286 1287 if (*p == '/' || trust) { 1288 char *pathname; 1289 const char *dir = p; 1290 size_t dirlen = len; 1291 1292 pathname = xmalloc(dirlen + 1 + namelen + 1); 1293 strncpy(pathname, dir, dirlen); 1294 pathname[dirlen] = '/'; 1295 strcpy(pathname + dirlen + 1, name); 1296 1297 dbg(" Trying \"%s\"", pathname); 1298 if (access(pathname, F_OK) == 0) /* We found it */ 1299 return pathname; 1300 1301 free(pathname); 1302 } 1303 p += len; 1304 p += strspn(p, ":;"); 1305 } 1306 1307 return NULL; 1308 } 1309 1310 int 1311 dlclose(void *handle) 1312 { 1313 Obj_Entry *root; 1314 Obj_Entry *obj; 1315 Funclist finilist; 1316 1317 wlock_acquire(); 1318 root = dlcheck(handle); 1319 if (root == NULL) { 1320 lock_release(); 1321 return -1; 1322 } 1323 1324 /* Unreference the object and its dependencies. */ 1325 root->dl_refcount--; 1326 unref_dag(root); 1327 1328 if (root->refcount == 0) { 1329 /* 1330 * The object is no longer referenced, so we must unload it. 1331 * First, make a list of the fini functions and then call them 1332 * with no locks held. 1333 */ 1334 funclist_init(&finilist); 1335 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1336 if (obj->refcount == 0 && obj->fini != NULL) 1337 funclist_push_tail(&finilist, obj->fini); 1338 1339 lock_release(); 1340 funclist_call(&finilist); 1341 wlock_acquire(); 1342 funclist_clear(&finilist); 1343 1344 /* Finish cleaning up the newly-unreferenced objects. */ 1345 GDB_STATE(RT_DELETE); 1346 unload_object(root); 1347 GDB_STATE(RT_CONSISTENT); 1348 } 1349 lock_release(); 1350 return 0; 1351 } 1352 1353 const char * 1354 dlerror(void) 1355 { 1356 char *msg = error_message; 1357 error_message = NULL; 1358 return msg; 1359 } 1360 1361 void 1362 dllockinit(void *context, 1363 void *(*lock_create)(void *context), 1364 void (*rlock_acquire)(void *lock), 1365 void (*wlock_acquire)(void *lock), 1366 void (*lock_release)(void *lock), 1367 void (*lock_destroy)(void *lock), 1368 void (*context_destroy)(void *context)) 1369 { 1370 bool is_dflt = false; 1371 1372 /* NULL arguments mean reset to the built-in locks. */ 1373 if (lock_create == NULL) { 1374 is_dflt = true; 1375 context = NULL; 1376 lock_create = lockdflt_create; 1377 rlock_acquire = wlock_acquire = lockdflt_acquire; 1378 lock_release = lockdflt_release; 1379 lock_destroy = lockdflt_destroy; 1380 context_destroy = NULL; 1381 } 1382 1383 /* Temporarily set locking methods to no-ops. */ 1384 lockinfo.rlock_acquire = lock_nop; 1385 lockinfo.wlock_acquire = lock_nop; 1386 lockinfo.lock_release = lock_nop; 1387 1388 /* Release any existing locks and context. */ 1389 if (lockinfo.lock_destroy != NULL) 1390 lockinfo.lock_destroy(lockinfo.thelock); 1391 if (lockinfo.context_destroy != NULL) 1392 lockinfo.context_destroy(lockinfo.context); 1393 1394 /* 1395 * Make sure the shared objects containing the locking methods are 1396 * fully bound, to avoid infinite recursion when they are called 1397 * from the lazy binding code. 1398 */ 1399 if (!is_dflt) { 1400 prebind((void *)rlock_acquire); 1401 prebind((void *)wlock_acquire); 1402 prebind((void *)lock_release); 1403 } 1404 1405 /* Allocate our lock. */ 1406 lockinfo.thelock = lock_create(lockinfo.context); 1407 1408 /* Record the new method information. */ 1409 lockinfo.context = context; 1410 lockinfo.rlock_acquire = rlock_acquire; 1411 lockinfo.wlock_acquire = wlock_acquire; 1412 lockinfo.lock_release = lock_release; 1413 lockinfo.lock_destroy = lock_destroy; 1414 lockinfo.context_destroy = context_destroy; 1415 } 1416 1417 static void 1418 prebind(void *addr) 1419 { 1420 Obj_Entry *obj; 1421 1422 if ((obj = obj_from_addr(addr)) == NULL) { 1423 _rtld_error("Cannot determine shared object of locking method at %p", 1424 addr); 1425 die(); 1426 } 1427 if (!obj->rtld && !obj->jmpslots_done) { 1428 dbg("Pre-binding %s for locking", obj->path); 1429 if (reloc_jmpslots(obj) == -1) 1430 die(); 1431 } 1432 } 1433 1434 void * 1435 dlopen(const char *name, int mode) 1436 { 1437 Obj_Entry **old_obj_tail; 1438 Obj_Entry *obj; 1439 Obj_Entry *initobj; 1440 Funclist initlist; 1441 1442 funclist_init(&initlist); 1443 1444 wlock_acquire(); 1445 GDB_STATE(RT_ADD); 1446 1447 old_obj_tail = obj_tail; 1448 obj = NULL; 1449 if (name == NULL) { 1450 obj = obj_main; 1451 obj->refcount++; 1452 } else { 1453 char *path = find_library(name, obj_main); 1454 if (path != NULL) 1455 obj = load_object(path); 1456 } 1457 1458 if (obj) { 1459 obj->dl_refcount++; 1460 if (mode & RTLD_GLOBAL && objlist_find(&list_global, obj) == NULL) 1461 objlist_add(&list_global, obj); 1462 mode &= RTLD_MODEMASK; 1463 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1464 assert(*old_obj_tail == obj); 1465 1466 if (load_needed_objects(obj) == -1 || 1467 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) { 1468 obj->dl_refcount--; 1469 unref_dag(obj); 1470 if (obj->refcount == 0) 1471 unload_object(obj); 1472 obj = NULL; 1473 } else { 1474 /* Make list of init functions to call, in reverse order */ 1475 for (initobj = obj; initobj != NULL; initobj = initobj->next) 1476 if (initobj->init != NULL) 1477 funclist_push_head(&initlist, initobj->init); 1478 } 1479 } 1480 } 1481 1482 GDB_STATE(RT_CONSISTENT); 1483 1484 /* Call the init functions with no locks held. */ 1485 lock_release(); 1486 funclist_call(&initlist); 1487 wlock_acquire(); 1488 funclist_clear(&initlist); 1489 lock_release(); 1490 return obj; 1491 } 1492 1493 void * 1494 dlsym(void *handle, const char *name) 1495 { 1496 const Obj_Entry *obj; 1497 unsigned long hash; 1498 const Elf_Sym *def; 1499 const Obj_Entry *defobj; 1500 1501 hash = elf_hash(name); 1502 def = NULL; 1503 defobj = NULL; 1504 1505 wlock_acquire(); 1506 if (handle == NULL || handle == RTLD_NEXT) { 1507 void *retaddr; 1508 1509 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1510 if ((obj = obj_from_addr(retaddr)) == NULL) { 1511 _rtld_error("Cannot determine caller's shared object"); 1512 lock_release(); 1513 return NULL; 1514 } 1515 if (handle == NULL) { /* Just the caller's shared object. */ 1516 def = symlook_obj(name, hash, obj, true); 1517 defobj = obj; 1518 } else { /* All the shared objects after the caller's */ 1519 while ((obj = obj->next) != NULL) { 1520 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1521 defobj = obj; 1522 break; 1523 } 1524 } 1525 } 1526 } else { 1527 if ((obj = dlcheck(handle)) == NULL) { 1528 lock_release(); 1529 return NULL; 1530 } 1531 1532 if (obj->mainprog) { 1533 /* Search main program and all libraries loaded by it. */ 1534 curmark++; 1535 def = symlook_list(name, hash, &list_main, &defobj, true); 1536 } else { 1537 /* 1538 * XXX - This isn't correct. The search should include the whole 1539 * DAG rooted at the given object. 1540 */ 1541 def = symlook_obj(name, hash, obj, true); 1542 defobj = obj; 1543 } 1544 } 1545 1546 if (def != NULL) { 1547 lock_release(); 1548 return defobj->relocbase + def->st_value; 1549 } 1550 1551 _rtld_error("Undefined symbol \"%s\"", name); 1552 lock_release(); 1553 return NULL; 1554 } 1555 1556 int 1557 dladdr(const void *addr, Dl_info *info) 1558 { 1559 const Obj_Entry *obj; 1560 const Elf_Sym *def; 1561 void *symbol_addr; 1562 unsigned long symoffset; 1563 1564 wlock_acquire(); 1565 obj = obj_from_addr(addr); 1566 if (obj == NULL) { 1567 _rtld_error("No shared object contains address"); 1568 lock_release(); 1569 return 0; 1570 } 1571 info->dli_fname = obj->path; 1572 info->dli_fbase = obj->mapbase; 1573 info->dli_saddr = (void *)0; 1574 info->dli_sname = NULL; 1575 1576 /* 1577 * Walk the symbol list looking for the symbol whose address is 1578 * closest to the address sent in. 1579 */ 1580 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1581 def = obj->symtab + symoffset; 1582 1583 /* 1584 * For skip the symbol if st_shndx is either SHN_UNDEF or 1585 * SHN_COMMON. 1586 */ 1587 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1588 continue; 1589 1590 /* 1591 * If the symbol is greater than the specified address, or if it 1592 * is further away from addr than the current nearest symbol, 1593 * then reject it. 1594 */ 1595 symbol_addr = obj->relocbase + def->st_value; 1596 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1597 continue; 1598 1599 /* Update our idea of the nearest symbol. */ 1600 info->dli_sname = obj->strtab + def->st_name; 1601 info->dli_saddr = symbol_addr; 1602 1603 /* Exact match? */ 1604 if (info->dli_saddr == addr) 1605 break; 1606 } 1607 lock_release(); 1608 return 1; 1609 } 1610 1611 static void 1612 linkmap_add(Obj_Entry *obj) 1613 { 1614 struct link_map *l = &obj->linkmap; 1615 struct link_map *prev; 1616 1617 obj->linkmap.l_name = obj->path; 1618 obj->linkmap.l_addr = obj->mapbase; 1619 obj->linkmap.l_ld = obj->dynamic; 1620 #ifdef __mips__ 1621 /* GDB needs load offset on MIPS to use the symbols */ 1622 obj->linkmap.l_offs = obj->relocbase; 1623 #endif 1624 1625 if (r_debug.r_map == NULL) { 1626 r_debug.r_map = l; 1627 return; 1628 } 1629 1630 /* 1631 * Scan to the end of the list, but not past the entry for the 1632 * dynamic linker, which we want to keep at the very end. 1633 */ 1634 for (prev = r_debug.r_map; 1635 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 1636 prev = prev->l_next) 1637 ; 1638 1639 /* Link in the new entry. */ 1640 l->l_prev = prev; 1641 l->l_next = prev->l_next; 1642 if (l->l_next != NULL) 1643 l->l_next->l_prev = l; 1644 prev->l_next = l; 1645 } 1646 1647 static void 1648 linkmap_delete(Obj_Entry *obj) 1649 { 1650 struct link_map *l = &obj->linkmap; 1651 1652 if (l->l_prev == NULL) { 1653 if ((r_debug.r_map = l->l_next) != NULL) 1654 l->l_next->l_prev = NULL; 1655 return; 1656 } 1657 1658 if ((l->l_prev->l_next = l->l_next) != NULL) 1659 l->l_next->l_prev = l->l_prev; 1660 } 1661 1662 /* 1663 * Function for the debugger to set a breakpoint on to gain control. 1664 */ 1665 void 1666 r_debug_state(void) 1667 { 1668 } 1669 1670 /* 1671 * Set a pointer variable in the main program to the given value. This 1672 * is used to set key variables such as "environ" before any of the 1673 * init functions are called. 1674 */ 1675 static void 1676 set_program_var(const char *name, const void *value) 1677 { 1678 const Obj_Entry *obj; 1679 unsigned long hash; 1680 1681 hash = elf_hash(name); 1682 for (obj = obj_main; obj != NULL; obj = obj->next) { 1683 const Elf_Sym *def; 1684 1685 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 1686 const void **addr; 1687 1688 addr = (const void **)(obj->relocbase + def->st_value); 1689 dbg("\"%s\": *%p <-- %p", name, addr, value); 1690 *addr = value; 1691 break; 1692 } 1693 } 1694 } 1695 1696 static const Elf_Sym * 1697 symlook_list(const char *name, unsigned long hash, Objlist *objlist, 1698 const Obj_Entry **defobj_out, bool in_plt) 1699 { 1700 const Elf_Sym *symp; 1701 const Elf_Sym *def; 1702 const Obj_Entry *defobj; 1703 const Objlist_Entry *elm; 1704 1705 def = NULL; 1706 defobj = NULL; 1707 STAILQ_FOREACH(elm, objlist, link) { 1708 if (elm->obj->mark == curmark) 1709 continue; 1710 elm->obj->mark = curmark; 1711 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 1712 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 1713 def = symp; 1714 defobj = elm->obj; 1715 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 1716 break; 1717 } 1718 } 1719 } 1720 if (def != NULL) 1721 *defobj_out = defobj; 1722 return def; 1723 } 1724 1725 /* 1726 * Search the symbol table of a single shared object for a symbol of 1727 * the given name. Returns a pointer to the symbol, or NULL if no 1728 * definition was found. 1729 * 1730 * The symbol's hash value is passed in for efficiency reasons; that 1731 * eliminates many recomputations of the hash value. 1732 */ 1733 const Elf_Sym * 1734 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 1735 bool in_plt) 1736 { 1737 if (obj->buckets != NULL) { 1738 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 1739 1740 while (symnum != STN_UNDEF) { 1741 const Elf_Sym *symp; 1742 const char *strp; 1743 1744 if (symnum >= obj->nchains) 1745 return NULL; /* Bad object */ 1746 symp = obj->symtab + symnum; 1747 strp = obj->strtab + symp->st_name; 1748 1749 if (strcmp(name, strp) == 0) 1750 return symp->st_shndx != SHN_UNDEF || 1751 (!in_plt && symp->st_value != 0 && 1752 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 1753 1754 symnum = obj->chains[symnum]; 1755 } 1756 } 1757 return NULL; 1758 } 1759 1760 static void 1761 trace_loaded_objects(Obj_Entry *obj) 1762 { 1763 char *fmt1, *fmt2, *fmt, *main_local; 1764 int c; 1765 1766 if ((main_local = getenv("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 1767 main_local = ""; 1768 1769 if ((fmt1 = getenv("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 1770 fmt1 = "\t%o => %p (%x)\n"; 1771 1772 if ((fmt2 = getenv("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 1773 fmt2 = "\t%o (%x)\n"; 1774 1775 for (; obj; obj = obj->next) { 1776 Needed_Entry *needed; 1777 char *name, *path; 1778 bool is_lib; 1779 1780 for (needed = obj->needed; needed; needed = needed->next) { 1781 if (needed->obj != NULL) { 1782 if (needed->obj->traced) 1783 continue; 1784 needed->obj->traced = true; 1785 path = needed->obj->path; 1786 } else 1787 path = "not found"; 1788 1789 name = (char *)obj->strtab + needed->name; 1790 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 1791 1792 fmt = is_lib ? fmt1 : fmt2; 1793 while ((c = *fmt++) != '\0') { 1794 switch (c) { 1795 default: 1796 putchar(c); 1797 continue; 1798 case '\\': 1799 switch (c = *fmt) { 1800 case '\0': 1801 continue; 1802 case 'n': 1803 putchar('\n'); 1804 break; 1805 case 't': 1806 putchar('\t'); 1807 break; 1808 } 1809 break; 1810 case '%': 1811 switch (c = *fmt) { 1812 case '\0': 1813 continue; 1814 case '%': 1815 default: 1816 putchar(c); 1817 break; 1818 case 'A': 1819 printf("%s", main_local); 1820 break; 1821 case 'a': 1822 printf("%s", obj_main->path); 1823 break; 1824 case 'o': 1825 printf("%s", name); 1826 break; 1827 #if 0 1828 case 'm': 1829 printf("%d", sodp->sod_major); 1830 break; 1831 case 'n': 1832 printf("%d", sodp->sod_minor); 1833 break; 1834 #endif 1835 case 'p': 1836 printf("%s", path); 1837 break; 1838 case 'x': 1839 printf("%p", needed->obj ? needed->obj->mapbase : 0); 1840 break; 1841 } 1842 break; 1843 } 1844 ++fmt; 1845 } 1846 } 1847 } 1848 } 1849 1850 /* 1851 * Unload a dlopened object and its dependencies from memory and from 1852 * our data structures. It is assumed that the DAG rooted in the 1853 * object has already been unreferenced, and that the object has a 1854 * reference count of 0. 1855 */ 1856 static void 1857 unload_object(Obj_Entry *root) 1858 { 1859 Obj_Entry *obj; 1860 Obj_Entry **linkp; 1861 Objlist_Entry *elm; 1862 1863 assert(root->refcount == 0); 1864 1865 /* Remove the DAG from all objects' DAG lists. */ 1866 STAILQ_FOREACH(elm, &root->dagmembers , link) 1867 objlist_remove(&elm->obj->dldags, root); 1868 1869 /* Remove the DAG from the RTLD_GLOBAL list. */ 1870 objlist_remove(&list_global, root); 1871 1872 /* Unmap all objects that are no longer referenced. */ 1873 linkp = &obj_list->next; 1874 while ((obj = *linkp) != NULL) { 1875 if (obj->refcount == 0) { 1876 dbg("unloading \"%s\"", obj->path); 1877 munmap(obj->mapbase, obj->mapsize); 1878 linkmap_delete(obj); 1879 *linkp = obj->next; 1880 obj_free(obj); 1881 } else 1882 linkp = &obj->next; 1883 } 1884 obj_tail = linkp; 1885 } 1886 1887 static void 1888 unref_dag(Obj_Entry *root) 1889 { 1890 const Needed_Entry *needed; 1891 1892 assert(root->refcount != 0); 1893 root->refcount--; 1894 if (root->refcount == 0) 1895 for (needed = root->needed; needed != NULL; needed = needed->next) 1896 if (needed->obj != NULL) 1897 unref_dag(needed->obj); 1898 } 1899 1900 /* 1901 * Non-mallocing printf, for use by malloc itself. 1902 * XXX - This doesn't belong in this module. 1903 */ 1904 void 1905 xprintf(const char *fmt, ...) 1906 { 1907 char buf[256]; 1908 va_list ap; 1909 1910 va_start(ap, fmt); 1911 vsprintf(buf, fmt, ap); 1912 (void)write(1, buf, strlen(buf)); 1913 va_end(ap); 1914 } 1915