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