1 /*- 2 * Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra. 3 * Copyright 2003 Alexander Kabaev <kan@FreeBSD.ORG>. 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 * $FreeBSD: src/libexec/rtld-elf/rtld.c,v 1.43.2.15 2003/02/20 20:42:46 kan Exp $ 27 * $DragonFly: src/libexec/rtld-elf/rtld.c,v 1.8 2004/11/18 10:01:47 dillon Exp $ 28 */ 29 30 /* 31 * Dynamic linker for ELF. 32 * 33 * John Polstra <jdp@polstra.com>. 34 */ 35 36 #ifndef __GNUC__ 37 #error "GCC is needed to compile this file" 38 #endif 39 40 #include <sys/param.h> 41 #include <sys/mman.h> 42 #include <sys/stat.h> 43 #include <sys/resident.h> 44 45 #include <dlfcn.h> 46 #include <err.h> 47 #include <errno.h> 48 #include <fcntl.h> 49 #include <stdarg.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include <unistd.h> 54 55 #include "debug.h" 56 #include "rtld.h" 57 58 #define END_SYM "_end" 59 #define PATH_RTLD "/usr/libexec/ld-elf.so.1" 60 #define LD_ARY_CACHE 16 61 62 /* Types. */ 63 typedef void (*func_ptr_type)(); 64 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg); 65 66 /* 67 * This structure provides a reentrant way to keep a list of objects and 68 * check which ones have already been processed in some way. 69 */ 70 typedef struct Struct_DoneList { 71 const Obj_Entry **objs; /* Array of object pointers */ 72 unsigned int num_alloc; /* Allocated size of the array */ 73 unsigned int num_used; /* Number of array slots used */ 74 } DoneList; 75 76 /* 77 * Function declarations. 78 */ 79 static void die(void); 80 static void digest_dynamic(Obj_Entry *); 81 static const char *_getenv_ld(const char *id); 82 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *); 83 static Obj_Entry *dlcheck(void *); 84 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *); 85 static bool donelist_check(DoneList *, const Obj_Entry *); 86 static void errmsg_restore(char *); 87 static char *errmsg_save(void); 88 static void *fill_search_info(const char *, size_t, void *); 89 static char *find_library(const char *, const Obj_Entry *); 90 static const char *gethints(void); 91 static void init_dag(Obj_Entry *); 92 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *); 93 static void init_rtld(caddr_t); 94 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list); 95 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, 96 Objlist *list); 97 static bool is_exported(const Elf_Sym *); 98 static void linkmap_add(Obj_Entry *); 99 static void linkmap_delete(Obj_Entry *); 100 static int load_needed_objects(Obj_Entry *); 101 static int load_preload_objects(void); 102 static Obj_Entry *load_object(char *); 103 static void lock_check(void); 104 static Obj_Entry *obj_from_addr(const void *); 105 static void objlist_call_fini(Objlist *); 106 static void objlist_call_init(Objlist *); 107 static void objlist_clear(Objlist *); 108 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *); 109 static void objlist_init(Objlist *); 110 static void objlist_push_head(Objlist *, Obj_Entry *); 111 static void objlist_push_tail(Objlist *, Obj_Entry *); 112 static void objlist_remove(Objlist *, Obj_Entry *); 113 static void objlist_remove_unref(Objlist *); 114 static void *path_enumerate(const char *, path_enum_proc, void *); 115 static int relocate_objects(Obj_Entry *, bool); 116 static int rtld_dirname(const char *, char *); 117 static void rtld_exit(void); 118 static char *search_library_path(const char *, const char *); 119 static const void **get_program_var_addr(const char *name); 120 static void set_program_var(const char *, const void *); 121 static const Elf_Sym *symlook_default(const char *, unsigned long hash, 122 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt); 123 static const Elf_Sym *symlook_list(const char *, unsigned long, 124 Objlist *, const Obj_Entry **, bool in_plt, DoneList *); 125 static void trace_loaded_objects(Obj_Entry *obj); 126 static void unlink_object(Obj_Entry *); 127 static void unload_object(Obj_Entry *); 128 static void unref_dag(Obj_Entry *); 129 130 void r_debug_state(struct r_debug*, struct link_map*); 131 132 /* 133 * Data declarations. 134 */ 135 static char *error_message; /* Message for dlerror(), or NULL */ 136 struct r_debug r_debug; /* for GDB; */ 137 static bool trust; /* False for setuid and setgid programs */ 138 static const char *ld_bind_now; /* Environment variable for immediate binding */ 139 static const char *ld_debug; /* Environment variable for debugging */ 140 static const char *ld_library_path; /* Environment variable for search path */ 141 static char *ld_preload; /* Environment variable for libraries to 142 load first */ 143 static const char *ld_tracing; /* Called from ldd(1) to print libs */ 144 static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 145 static Obj_Entry **obj_tail; /* Link field of last object in list */ 146 static Obj_Entry **preload_tail; 147 static Obj_Entry *obj_main; /* The main program shared object */ 148 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 149 static unsigned int obj_count; /* Number of objects in obj_list */ 150 static int ld_resident; /* Non-zero if resident */ 151 static const char *ld_ary[LD_ARY_CACHE]; 152 static int ld_index; 153 154 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 155 STAILQ_HEAD_INITIALIZER(list_global); 156 static Objlist list_main = /* Objects loaded at program startup */ 157 STAILQ_HEAD_INITIALIZER(list_main); 158 static Objlist list_fini = /* Objects needing fini() calls */ 159 STAILQ_HEAD_INITIALIZER(list_fini); 160 161 static LockInfo lockinfo; 162 163 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 164 165 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); 166 167 extern Elf_Dyn _DYNAMIC; 168 #pragma weak _DYNAMIC 169 170 /* 171 * These are the functions the dynamic linker exports to application 172 * programs. They are the only symbols the dynamic linker is willing 173 * to export from itself. 174 */ 175 static func_ptr_type exports[] = { 176 (func_ptr_type) &_rtld_error, 177 (func_ptr_type) &dlclose, 178 (func_ptr_type) &dlerror, 179 (func_ptr_type) &dlopen, 180 (func_ptr_type) &dlsym, 181 (func_ptr_type) &dladdr, 182 (func_ptr_type) &dllockinit, 183 (func_ptr_type) &dlinfo, 184 NULL 185 }; 186 187 /* 188 * Global declarations normally provided by crt1. The dynamic linker is 189 * not built with crt1, so we have to provide them ourselves. 190 */ 191 char *__progname; 192 char **environ; 193 194 /* 195 * Fill in a DoneList with an allocation large enough to hold all of 196 * the currently-loaded objects. Keep this as a macro since it calls 197 * alloca and we want that to occur within the scope of the caller. 198 */ 199 #define donelist_init(dlp) \ 200 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ 201 assert((dlp)->objs != NULL), \ 202 (dlp)->num_alloc = obj_count, \ 203 (dlp)->num_used = 0) 204 205 static __inline void 206 rlock_acquire(void) 207 { 208 lockinfo.rlock_acquire(lockinfo.thelock); 209 atomic_incr_int(&lockinfo.rcount); 210 lock_check(); 211 } 212 213 static __inline void 214 wlock_acquire(void) 215 { 216 lockinfo.wlock_acquire(lockinfo.thelock); 217 atomic_incr_int(&lockinfo.wcount); 218 lock_check(); 219 } 220 221 static __inline void 222 rlock_release(void) 223 { 224 atomic_decr_int(&lockinfo.rcount); 225 lockinfo.rlock_release(lockinfo.thelock); 226 } 227 228 static __inline void 229 wlock_release(void) 230 { 231 atomic_decr_int(&lockinfo.wcount); 232 lockinfo.wlock_release(lockinfo.thelock); 233 } 234 235 /* 236 * Main entry point for dynamic linking. The first argument is the 237 * stack pointer. The stack is expected to be laid out as described 238 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 239 * Specifically, the stack pointer points to a word containing 240 * ARGC. Following that in the stack is a null-terminated sequence 241 * of pointers to argument strings. Then comes a null-terminated 242 * sequence of pointers to environment strings. Finally, there is a 243 * sequence of "auxiliary vector" entries. 244 * 245 * The second argument points to a place to store the dynamic linker's 246 * exit procedure pointer and the third to a place to store the main 247 * program's object. 248 * 249 * The return value is the main program's entry point. 250 */ 251 func_ptr_type 252 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 253 { 254 Elf_Auxinfo *aux_info[AT_COUNT]; 255 int i; 256 int argc; 257 char **argv; 258 char **env; 259 Elf_Auxinfo *aux; 260 Elf_Auxinfo *auxp; 261 const char *argv0; 262 Obj_Entry *obj; 263 Objlist initlist; 264 265 ld_index = 0; /* don't use old env cache in case we are resident */ 266 267 /* 268 * On entry, the dynamic linker itself has not been relocated yet. 269 * Be very careful not to reference any global data until after 270 * init_rtld has returned. It is OK to reference file-scope statics 271 * and string constants, and to call static and global functions. 272 */ 273 274 /* Find the auxiliary vector on the stack. */ 275 argc = *sp++; 276 argv = (char **) sp; 277 sp += argc + 1; /* Skip over arguments and NULL terminator */ 278 env = (char **) sp; 279 280 /* 281 * If we aren't already resident we have to dig out some more info. 282 * Note that auxinfo does not exist when we are resident. 283 */ 284 if (ld_resident == 0) { 285 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 286 ; 287 aux = (Elf_Auxinfo *) sp; 288 289 /* Digest the auxiliary vector. */ 290 for (i = 0; i < AT_COUNT; i++) 291 aux_info[i] = NULL; 292 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 293 if (auxp->a_type < AT_COUNT) 294 aux_info[auxp->a_type] = auxp; 295 } 296 297 /* Initialize and relocate ourselves. */ 298 assert(aux_info[AT_BASE] != NULL); 299 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 300 } 301 302 __progname = obj_rtld.path; 303 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 304 environ = env; 305 306 trust = (geteuid() == getuid()) && (getegid() == getgid()); 307 308 ld_bind_now = _getenv_ld("LD_BIND_NOW"); 309 if (trust) { 310 ld_debug = _getenv_ld("LD_DEBUG"); 311 ld_library_path = _getenv_ld("LD_LIBRARY_PATH"); 312 ld_preload = (char *)_getenv_ld("LD_PRELOAD"); 313 } 314 ld_tracing = _getenv_ld("LD_TRACE_LOADED_OBJECTS"); 315 316 if (ld_debug != NULL && *ld_debug != '\0') 317 debug = 1; 318 dbg("%s is initialized, base address = %p", __progname, 319 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 320 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 321 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 322 323 /* 324 * If we are resident we can skip work that we have already done. 325 * Note that the stack is reset and there is no Elf_Auxinfo 326 * when running from a resident image, and the static globals setup 327 * between here and resident_skip will have already been setup. 328 */ 329 if (ld_resident) 330 goto resident_skip1; 331 332 /* 333 * Load the main program, or process its program header if it is 334 * already loaded. 335 */ 336 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 337 int fd = aux_info[AT_EXECFD]->a_un.a_val; 338 dbg("loading main program"); 339 obj_main = map_object(fd, argv0, NULL); 340 close(fd); 341 if (obj_main == NULL) 342 die(); 343 } else { /* Main program already loaded. */ 344 const Elf_Phdr *phdr; 345 int phnum; 346 caddr_t entry; 347 348 dbg("processing main program's program header"); 349 assert(aux_info[AT_PHDR] != NULL); 350 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 351 assert(aux_info[AT_PHNUM] != NULL); 352 phnum = aux_info[AT_PHNUM]->a_un.a_val; 353 assert(aux_info[AT_PHENT] != NULL); 354 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 355 assert(aux_info[AT_ENTRY] != NULL); 356 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 357 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 358 die(); 359 } 360 361 obj_main->path = xstrdup(argv0); 362 obj_main->mainprog = true; 363 364 /* 365 * Get the actual dynamic linker pathname from the executable if 366 * possible. (It should always be possible.) That ensures that 367 * gdb will find the right dynamic linker even if a non-standard 368 * one is being used. 369 */ 370 if (obj_main->interp != NULL && 371 strcmp(obj_main->interp, obj_rtld.path) != 0) { 372 free(obj_rtld.path); 373 obj_rtld.path = xstrdup(obj_main->interp); 374 } 375 376 digest_dynamic(obj_main); 377 378 linkmap_add(obj_main); 379 linkmap_add(&obj_rtld); 380 381 /* Link the main program into the list of objects. */ 382 *obj_tail = obj_main; 383 obj_tail = &obj_main->next; 384 obj_count++; 385 obj_main->refcount++; 386 /* Make sure we don't call the main program's init and fini functions. */ 387 obj_main->init = obj_main->fini = NULL; 388 389 /* Initialize a fake symbol for resolving undefined weak references. */ 390 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 391 sym_zero.st_shndx = SHN_ABS; 392 393 dbg("loading LD_PRELOAD libraries"); 394 if (load_preload_objects() == -1) 395 die(); 396 preload_tail = obj_tail; 397 398 dbg("loading needed objects"); 399 if (load_needed_objects(obj_main) == -1) 400 die(); 401 402 /* Make a list of all objects loaded at startup. */ 403 for (obj = obj_list; obj != NULL; obj = obj->next) 404 objlist_push_tail(&list_main, obj); 405 406 resident_skip1: 407 408 if (ld_tracing) { /* We're done */ 409 trace_loaded_objects(obj_main); 410 exit(0); 411 } 412 413 if (ld_resident) /* XXX clean this up! */ 414 goto resident_skip2; 415 416 if (relocate_objects(obj_main, 417 ld_bind_now != NULL && *ld_bind_now != '\0') == -1) 418 die(); 419 420 dbg("doing copy relocations"); 421 if (do_copy_relocations(obj_main) == -1) 422 die(); 423 424 resident_skip2: 425 426 if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) { 427 if (exec_sys_unregister(-1) < 0) { 428 dbg("exec_sys_unregister failed %d\n", errno); 429 exit(errno); 430 } 431 dbg("exec_sys_unregister success\n"); 432 exit(0); 433 } 434 435 dbg("initializing key program variables"); 436 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 437 set_program_var("environ", env); 438 439 if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) { 440 extern void resident_start(void); 441 ld_resident = 1; 442 if (exec_sys_register(resident_start) < 0) { 443 dbg("exec_sys_register failed %d\n", errno); 444 exit(errno); 445 } 446 dbg("exec_sys_register success\n"); 447 exit(0); 448 } 449 450 dbg("initializing thread locks"); 451 lockdflt_init(&lockinfo); 452 lockinfo.thelock = lockinfo.lock_create(lockinfo.context); 453 454 /* Make a list of init functions to call. */ 455 objlist_init(&initlist); 456 initlist_add_objects(obj_list, preload_tail, &initlist); 457 458 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ 459 460 objlist_call_init(&initlist); 461 wlock_acquire(); 462 objlist_clear(&initlist); 463 wlock_release(); 464 465 466 467 dbg("transferring control to program entry point = %p", obj_main->entry); 468 469 /* Return the exit procedure and the program entry point. */ 470 *exit_proc = rtld_exit; 471 *objp = obj_main; 472 return (func_ptr_type) obj_main->entry; 473 } 474 475 Elf_Addr 476 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 477 { 478 const Elf_Rel *rel; 479 const Elf_Sym *def; 480 const Obj_Entry *defobj; 481 Elf_Addr *where; 482 Elf_Addr target; 483 484 rlock_acquire(); 485 if (obj->pltrel) 486 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 487 else 488 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 489 490 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 491 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 492 if (def == NULL) 493 die(); 494 495 target = (Elf_Addr)(defobj->relocbase + def->st_value); 496 497 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 498 defobj->strtab + def->st_name, basename(obj->path), 499 (void *)target, basename(defobj->path)); 500 501 reloc_jmpslot(where, target); 502 rlock_release(); 503 return target; 504 } 505 506 /* 507 * Error reporting function. Use it like printf. If formats the message 508 * into a buffer, and sets things up so that the next call to dlerror() 509 * will return the message. 510 */ 511 void 512 _rtld_error(const char *fmt, ...) 513 { 514 static char buf[512]; 515 va_list ap; 516 517 va_start(ap, fmt); 518 vsnprintf(buf, sizeof buf, fmt, ap); 519 error_message = buf; 520 va_end(ap); 521 } 522 523 /* 524 * Return a dynamically-allocated copy of the current error message, if any. 525 */ 526 static char * 527 errmsg_save(void) 528 { 529 return error_message == NULL ? NULL : xstrdup(error_message); 530 } 531 532 /* 533 * Restore the current error message from a copy which was previously saved 534 * by errmsg_save(). The copy is freed. 535 */ 536 static void 537 errmsg_restore(char *saved_msg) 538 { 539 if (saved_msg == NULL) 540 error_message = NULL; 541 else { 542 _rtld_error("%s", saved_msg); 543 free(saved_msg); 544 } 545 } 546 547 const char * 548 basename(const char *name) 549 { 550 const char *p = strrchr(name, '/'); 551 return p != NULL ? p + 1 : name; 552 } 553 554 static void 555 die(void) 556 { 557 const char *msg = dlerror(); 558 559 if (msg == NULL) 560 msg = "Fatal error"; 561 errx(1, "%s", msg); 562 } 563 564 /* 565 * Process a shared object's DYNAMIC section, and save the important 566 * information in its Obj_Entry structure. 567 */ 568 static void 569 digest_dynamic(Obj_Entry *obj) 570 { 571 const Elf_Dyn *dynp; 572 Needed_Entry **needed_tail = &obj->needed; 573 const Elf_Dyn *dyn_rpath = NULL; 574 int plttype = DT_REL; 575 576 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 577 switch (dynp->d_tag) { 578 579 case DT_REL: 580 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 581 break; 582 583 case DT_RELSZ: 584 obj->relsize = dynp->d_un.d_val; 585 break; 586 587 case DT_RELENT: 588 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 589 break; 590 591 case DT_JMPREL: 592 obj->pltrel = (const Elf_Rel *) 593 (obj->relocbase + dynp->d_un.d_ptr); 594 break; 595 596 case DT_PLTRELSZ: 597 obj->pltrelsize = dynp->d_un.d_val; 598 break; 599 600 case DT_RELA: 601 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 602 break; 603 604 case DT_RELASZ: 605 obj->relasize = dynp->d_un.d_val; 606 break; 607 608 case DT_RELAENT: 609 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 610 break; 611 612 case DT_PLTREL: 613 plttype = dynp->d_un.d_val; 614 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 615 break; 616 617 case DT_SYMTAB: 618 obj->symtab = (const Elf_Sym *) 619 (obj->relocbase + dynp->d_un.d_ptr); 620 break; 621 622 case DT_SYMENT: 623 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 624 break; 625 626 case DT_STRTAB: 627 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 628 break; 629 630 case DT_STRSZ: 631 obj->strsize = dynp->d_un.d_val; 632 break; 633 634 case DT_HASH: 635 { 636 const Elf_Addr *hashtab = (const Elf_Addr *) 637 (obj->relocbase + dynp->d_un.d_ptr); 638 obj->nbuckets = hashtab[0]; 639 obj->nchains = hashtab[1]; 640 obj->buckets = hashtab + 2; 641 obj->chains = obj->buckets + obj->nbuckets; 642 } 643 break; 644 645 case DT_NEEDED: 646 if (!obj->rtld) { 647 Needed_Entry *nep = NEW(Needed_Entry); 648 nep->name = dynp->d_un.d_val; 649 nep->obj = NULL; 650 nep->next = NULL; 651 652 *needed_tail = nep; 653 needed_tail = &nep->next; 654 } 655 break; 656 657 case DT_PLTGOT: 658 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 659 break; 660 661 case DT_TEXTREL: 662 obj->textrel = true; 663 break; 664 665 case DT_SYMBOLIC: 666 obj->symbolic = true; 667 break; 668 669 case DT_RPATH: 670 /* 671 * We have to wait until later to process this, because we 672 * might not have gotten the address of the string table yet. 673 */ 674 dyn_rpath = dynp; 675 break; 676 677 case DT_SONAME: 678 /* Not used by the dynamic linker. */ 679 break; 680 681 case DT_INIT: 682 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 683 break; 684 685 case DT_FINI: 686 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 687 break; 688 689 case DT_DEBUG: 690 /* XXX - not implemented yet */ 691 dbg("Filling in DT_DEBUG entry"); 692 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 693 break; 694 695 default: 696 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag); 697 break; 698 } 699 } 700 701 obj->traced = false; 702 703 if (plttype == DT_RELA) { 704 obj->pltrela = (const Elf_Rela *) obj->pltrel; 705 obj->pltrel = NULL; 706 obj->pltrelasize = obj->pltrelsize; 707 obj->pltrelsize = 0; 708 } 709 710 if (dyn_rpath != NULL) 711 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 712 } 713 714 /* 715 * Process a shared object's program header. This is used only for the 716 * main program, when the kernel has already loaded the main program 717 * into memory before calling the dynamic linker. It creates and 718 * returns an Obj_Entry structure. 719 */ 720 static Obj_Entry * 721 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 722 { 723 Obj_Entry *obj; 724 const Elf_Phdr *phlimit = phdr + phnum; 725 const Elf_Phdr *ph; 726 int nsegs = 0; 727 728 obj = obj_new(); 729 for (ph = phdr; ph < phlimit; ph++) { 730 switch (ph->p_type) { 731 732 case PT_PHDR: 733 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 734 _rtld_error("%s: invalid PT_PHDR", path); 735 return NULL; 736 } 737 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 738 obj->phsize = ph->p_memsz; 739 break; 740 741 case PT_INTERP: 742 obj->interp = (const char *) ph->p_vaddr; 743 break; 744 745 case PT_LOAD: 746 if (nsegs == 0) { /* First load segment */ 747 obj->vaddrbase = trunc_page(ph->p_vaddr); 748 obj->mapbase = (caddr_t) obj->vaddrbase; 749 obj->relocbase = obj->mapbase - obj->vaddrbase; 750 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 751 obj->vaddrbase; 752 } else { /* Last load segment */ 753 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 754 obj->vaddrbase; 755 } 756 nsegs++; 757 break; 758 759 case PT_DYNAMIC: 760 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 761 break; 762 } 763 } 764 if (nsegs < 1) { 765 _rtld_error("%s: too few PT_LOAD segments", path); 766 return NULL; 767 } 768 769 obj->entry = entry; 770 return obj; 771 } 772 773 static Obj_Entry * 774 dlcheck(void *handle) 775 { 776 Obj_Entry *obj; 777 778 for (obj = obj_list; obj != NULL; obj = obj->next) 779 if (obj == (Obj_Entry *) handle) 780 break; 781 782 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { 783 _rtld_error("Invalid shared object handle %p", handle); 784 return NULL; 785 } 786 return obj; 787 } 788 789 /* 790 * If the given object is already in the donelist, return true. Otherwise 791 * add the object to the list and return false. 792 */ 793 static bool 794 donelist_check(DoneList *dlp, const Obj_Entry *obj) 795 { 796 unsigned int i; 797 798 for (i = 0; i < dlp->num_used; i++) 799 if (dlp->objs[i] == obj) 800 return true; 801 /* 802 * Our donelist allocation should always be sufficient. But if 803 * our threads locking isn't working properly, more shared objects 804 * could have been loaded since we allocated the list. That should 805 * never happen, but we'll handle it properly just in case it does. 806 */ 807 if (dlp->num_used < dlp->num_alloc) 808 dlp->objs[dlp->num_used++] = obj; 809 return false; 810 } 811 812 /* 813 * Hash function for symbol table lookup. Don't even think about changing 814 * this. It is specified by the System V ABI. 815 */ 816 unsigned long 817 elf_hash(const char *name) 818 { 819 const unsigned char *p = (const unsigned char *) name; 820 unsigned long h = 0; 821 unsigned long g; 822 823 while (*p != '\0') { 824 h = (h << 4) + *p++; 825 if ((g = h & 0xf0000000) != 0) 826 h ^= g >> 24; 827 h &= ~g; 828 } 829 return h; 830 } 831 832 /* 833 * Find the library with the given name, and return its full pathname. 834 * The returned string is dynamically allocated. Generates an error 835 * message and returns NULL if the library cannot be found. 836 * 837 * If the second argument is non-NULL, then it refers to an already- 838 * loaded shared object, whose library search path will be searched. 839 * 840 * The search order is: 841 * LD_LIBRARY_PATH 842 * rpath in the referencing file 843 * ldconfig hints 844 * /usr/lib 845 */ 846 static char * 847 find_library(const char *name, const Obj_Entry *refobj) 848 { 849 char *pathname; 850 851 if (strchr(name, '/') != NULL) { /* Hard coded pathname */ 852 if (name[0] != '/' && !trust) { 853 _rtld_error("Absolute pathname required for shared object \"%s\"", 854 name); 855 return NULL; 856 } 857 return xstrdup(name); 858 } 859 860 dbg(" Searching for \"%s\"", name); 861 862 if ((pathname = search_library_path(name, ld_library_path)) != NULL || 863 (refobj != NULL && 864 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 865 (pathname = search_library_path(name, gethints())) != NULL || 866 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 867 return pathname; 868 869 _rtld_error("Shared object \"%s\" not found", name); 870 return NULL; 871 } 872 873 /* 874 * Given a symbol number in a referencing object, find the corresponding 875 * definition of the symbol. Returns a pointer to the symbol, or NULL if 876 * no definition was found. Returns a pointer to the Obj_Entry of the 877 * defining object via the reference parameter DEFOBJ_OUT. 878 */ 879 const Elf_Sym * 880 find_symdef(unsigned long symnum, const Obj_Entry *refobj, 881 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) 882 { 883 const Elf_Sym *ref; 884 const Elf_Sym *def; 885 const Obj_Entry *defobj; 886 const char *name; 887 unsigned long hash; 888 889 /* 890 * If we have already found this symbol, get the information from 891 * the cache. 892 */ 893 if (symnum >= refobj->nchains) 894 return NULL; /* Bad object */ 895 if (cache != NULL && cache[symnum].sym != NULL) { 896 *defobj_out = cache[symnum].obj; 897 return cache[symnum].sym; 898 } 899 900 ref = refobj->symtab + symnum; 901 name = refobj->strtab + ref->st_name; 902 hash = elf_hash(name); 903 defobj = NULL; 904 905 def = symlook_default(name, hash, refobj, &defobj, in_plt); 906 907 /* 908 * If we found no definition and the reference is weak, treat the 909 * symbol as having the value zero. 910 */ 911 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 912 def = &sym_zero; 913 defobj = obj_main; 914 } 915 916 if (def != NULL) { 917 *defobj_out = defobj; 918 /* Record the information in the cache to avoid subsequent lookups. */ 919 if (cache != NULL) { 920 cache[symnum].sym = def; 921 cache[symnum].obj = defobj; 922 } 923 } else 924 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 925 return def; 926 } 927 928 /* 929 * Return the search path from the ldconfig hints file, reading it if 930 * necessary. Returns NULL if there are problems with the hints file, 931 * or if the search path there is empty. 932 */ 933 static const char * 934 gethints(void) 935 { 936 static char *hints; 937 938 if (hints == NULL) { 939 int fd; 940 struct elfhints_hdr hdr; 941 char *p; 942 943 /* Keep from trying again in case the hints file is bad. */ 944 hints = ""; 945 946 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 947 return NULL; 948 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 949 hdr.magic != ELFHINTS_MAGIC || 950 hdr.version != 1) { 951 close(fd); 952 return NULL; 953 } 954 p = xmalloc(hdr.dirlistlen + 1); 955 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 956 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { 957 free(p); 958 close(fd); 959 return NULL; 960 } 961 hints = p; 962 close(fd); 963 } 964 return hints[0] != '\0' ? hints : NULL; 965 } 966 967 static void 968 init_dag(Obj_Entry *root) 969 { 970 DoneList donelist; 971 972 donelist_init(&donelist); 973 init_dag1(root, root, &donelist); 974 } 975 976 static void 977 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) 978 { 979 const Needed_Entry *needed; 980 981 if (donelist_check(dlp, obj)) 982 return; 983 objlist_push_tail(&obj->dldags, root); 984 objlist_push_tail(&root->dagmembers, obj); 985 for (needed = obj->needed; needed != NULL; needed = needed->next) 986 if (needed->obj != NULL) 987 init_dag1(root, needed->obj, dlp); 988 } 989 990 /* 991 * Initialize the dynamic linker. The argument is the address at which 992 * the dynamic linker has been mapped into memory. The primary task of 993 * this function is to relocate the dynamic linker. 994 */ 995 static void 996 init_rtld(caddr_t mapbase) 997 { 998 /* 999 * Conjure up an Obj_Entry structure for the dynamic linker. 1000 * 1001 * The "path" member is supposed to be dynamically-allocated, but we 1002 * aren't yet initialized sufficiently to do that. Below we will 1003 * replace the static version with a dynamically-allocated copy. 1004 */ 1005 obj_rtld.path = PATH_RTLD; 1006 obj_rtld.rtld = true; 1007 obj_rtld.mapbase = mapbase; 1008 #ifdef PIC 1009 obj_rtld.relocbase = mapbase; 1010 #endif 1011 if (&_DYNAMIC != 0) { 1012 obj_rtld.dynamic = rtld_dynamic(&obj_rtld); 1013 digest_dynamic(&obj_rtld); 1014 assert(obj_rtld.needed == NULL); 1015 assert(!obj_rtld.textrel); 1016 1017 /* 1018 * Temporarily put the dynamic linker entry into the object list, so 1019 * that symbols can be found. 1020 */ 1021 obj_list = &obj_rtld; 1022 obj_tail = &obj_rtld.next; 1023 obj_count = 1; 1024 1025 relocate_objects(&obj_rtld, true); 1026 } 1027 1028 /* Make the object list empty again. */ 1029 obj_list = NULL; 1030 obj_tail = &obj_list; 1031 obj_count = 0; 1032 1033 /* Replace the path with a dynamically allocated copy. */ 1034 obj_rtld.path = xstrdup(obj_rtld.path); 1035 1036 r_debug.r_brk = r_debug_state; 1037 r_debug.r_state = RT_CONSISTENT; 1038 } 1039 1040 /* 1041 * Add the init functions from a needed object list (and its recursive 1042 * needed objects) to "list". This is not used directly; it is a helper 1043 * function for initlist_add_objects(). The write lock must be held 1044 * when this function is called. 1045 */ 1046 static void 1047 initlist_add_neededs(Needed_Entry *needed, Objlist *list) 1048 { 1049 /* Recursively process the successor needed objects. */ 1050 if (needed->next != NULL) 1051 initlist_add_neededs(needed->next, list); 1052 1053 /* Process the current needed object. */ 1054 if (needed->obj != NULL) 1055 initlist_add_objects(needed->obj, &needed->obj->next, list); 1056 } 1057 1058 /* 1059 * Scan all of the DAGs rooted in the range of objects from "obj" to 1060 * "tail" and add their init functions to "list". This recurses over 1061 * the DAGs and ensure the proper init ordering such that each object's 1062 * needed libraries are initialized before the object itself. At the 1063 * same time, this function adds the objects to the global finalization 1064 * list "list_fini" in the opposite order. The write lock must be 1065 * held when this function is called. 1066 */ 1067 static void 1068 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) 1069 { 1070 if (obj->init_done) 1071 return; 1072 obj->init_done = true; 1073 1074 /* Recursively process the successor objects. */ 1075 if (&obj->next != tail) 1076 initlist_add_objects(obj->next, tail, list); 1077 1078 /* Recursively process the needed objects. */ 1079 if (obj->needed != NULL) 1080 initlist_add_neededs(obj->needed, list); 1081 1082 /* Add the object to the init list. */ 1083 if (obj->init != NULL) 1084 objlist_push_tail(list, obj); 1085 1086 /* Add the object to the global fini list in the reverse order. */ 1087 if (obj->fini != NULL) 1088 objlist_push_head(&list_fini, obj); 1089 } 1090 1091 static bool 1092 is_exported(const Elf_Sym *def) 1093 { 1094 func_ptr_type value; 1095 const func_ptr_type *p; 1096 1097 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value); 1098 for (p = exports; *p != NULL; p++) 1099 if (*p == value) 1100 return true; 1101 return false; 1102 } 1103 1104 /* 1105 * Given a shared object, traverse its list of needed objects, and load 1106 * each of them. Returns 0 on success. Generates an error message and 1107 * returns -1 on failure. 1108 */ 1109 static int 1110 load_needed_objects(Obj_Entry *first) 1111 { 1112 Obj_Entry *obj; 1113 1114 for (obj = first; obj != NULL; obj = obj->next) { 1115 Needed_Entry *needed; 1116 1117 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1118 const char *name = obj->strtab + needed->name; 1119 char *path = find_library(name, obj); 1120 1121 needed->obj = NULL; 1122 if (path == NULL && !ld_tracing) 1123 return -1; 1124 1125 if (path) { 1126 needed->obj = load_object(path); 1127 if (needed->obj == NULL && !ld_tracing) 1128 return -1; /* XXX - cleanup */ 1129 } 1130 } 1131 } 1132 1133 return 0; 1134 } 1135 1136 static int 1137 load_preload_objects(void) 1138 { 1139 char *p = ld_preload; 1140 static const char delim[] = " \t:;"; 1141 1142 if (p == NULL) 1143 return NULL; 1144 1145 p += strspn(p, delim); 1146 while (*p != '\0') { 1147 size_t len = strcspn(p, delim); 1148 char *path; 1149 char savech; 1150 1151 savech = p[len]; 1152 p[len] = '\0'; 1153 if ((path = find_library(p, NULL)) == NULL) 1154 return -1; 1155 if (load_object(path) == NULL) 1156 return -1; /* XXX - cleanup */ 1157 p[len] = savech; 1158 p += len; 1159 p += strspn(p, delim); 1160 } 1161 return 0; 1162 } 1163 1164 /* 1165 * Load a shared object into memory, if it is not already loaded. The 1166 * argument must be a string allocated on the heap. This function assumes 1167 * responsibility for freeing it when necessary. 1168 * 1169 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1170 * on failure. 1171 */ 1172 static Obj_Entry * 1173 load_object(char *path) 1174 { 1175 Obj_Entry *obj; 1176 int fd = -1; 1177 struct stat sb; 1178 1179 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1180 if (strcmp(obj->path, path) == 0) 1181 break; 1182 1183 /* 1184 * If we didn't find a match by pathname, open the file and check 1185 * again by device and inode. This avoids false mismatches caused 1186 * by multiple links or ".." in pathnames. 1187 * 1188 * To avoid a race, we open the file and use fstat() rather than 1189 * using stat(). 1190 */ 1191 if (obj == NULL) { 1192 if ((fd = open(path, O_RDONLY)) == -1) { 1193 _rtld_error("Cannot open \"%s\"", path); 1194 return NULL; 1195 } 1196 if (fstat(fd, &sb) == -1) { 1197 _rtld_error("Cannot fstat \"%s\"", path); 1198 close(fd); 1199 return NULL; 1200 } 1201 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1202 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) { 1203 close(fd); 1204 break; 1205 } 1206 } 1207 } 1208 1209 if (obj == NULL) { /* First use of this object, so we must map it in */ 1210 dbg("loading \"%s\"", path); 1211 obj = map_object(fd, path, &sb); 1212 close(fd); 1213 if (obj == NULL) { 1214 free(path); 1215 return NULL; 1216 } 1217 1218 obj->path = path; 1219 digest_dynamic(obj); 1220 1221 *obj_tail = obj; 1222 obj_tail = &obj->next; 1223 obj_count++; 1224 linkmap_add(obj); /* for GDB & dlinfo() */ 1225 1226 dbg(" %p .. %p: %s", obj->mapbase, 1227 obj->mapbase + obj->mapsize - 1, obj->path); 1228 if (obj->textrel) 1229 dbg(" WARNING: %s has impure text", obj->path); 1230 } else 1231 free(path); 1232 1233 obj->refcount++; 1234 return obj; 1235 } 1236 1237 /* 1238 * Check for locking violations and die if one is found. 1239 */ 1240 static void 1241 lock_check(void) 1242 { 1243 int rcount, wcount; 1244 1245 rcount = lockinfo.rcount; 1246 wcount = lockinfo.wcount; 1247 assert(rcount >= 0); 1248 assert(wcount >= 0); 1249 if (wcount > 1 || (wcount != 0 && rcount != 0)) { 1250 _rtld_error("Application locking error: %d readers and %d writers" 1251 " in dynamic linker. See DLLOCKINIT(3) in manual pages.", 1252 rcount, wcount); 1253 die(); 1254 } 1255 } 1256 1257 static Obj_Entry * 1258 obj_from_addr(const void *addr) 1259 { 1260 unsigned long endhash; 1261 Obj_Entry *obj; 1262 1263 endhash = elf_hash(END_SYM); 1264 for (obj = obj_list; obj != NULL; obj = obj->next) { 1265 const Elf_Sym *endsym; 1266 1267 if (addr < (void *) obj->mapbase) 1268 continue; 1269 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL) 1270 continue; /* No "end" symbol?! */ 1271 if (addr < (void *) (obj->relocbase + endsym->st_value)) 1272 return obj; 1273 } 1274 return NULL; 1275 } 1276 1277 /* 1278 * Call the finalization functions for each of the objects in "list" 1279 * which are unreferenced. All of the objects are expected to have 1280 * non-NULL fini functions. 1281 */ 1282 static void 1283 objlist_call_fini(Objlist *list) 1284 { 1285 Objlist_Entry *elm; 1286 char *saved_msg; 1287 1288 /* 1289 * Preserve the current error message since a fini function might 1290 * call into the dynamic linker and overwrite it. 1291 */ 1292 saved_msg = errmsg_save(); 1293 STAILQ_FOREACH(elm, list, link) { 1294 if (elm->obj->refcount == 0) { 1295 dbg("calling fini function for %s", elm->obj->path); 1296 (*elm->obj->fini)(); 1297 } 1298 } 1299 errmsg_restore(saved_msg); 1300 } 1301 1302 /* 1303 * Call the initialization functions for each of the objects in 1304 * "list". All of the objects are expected to have non-NULL init 1305 * functions. 1306 */ 1307 static void 1308 objlist_call_init(Objlist *list) 1309 { 1310 Objlist_Entry *elm; 1311 char *saved_msg; 1312 1313 /* 1314 * Preserve the current error message since an init function might 1315 * call into the dynamic linker and overwrite it. 1316 */ 1317 saved_msg = errmsg_save(); 1318 STAILQ_FOREACH(elm, list, link) { 1319 dbg("calling init function for %s", elm->obj->path); 1320 (*elm->obj->init)(); 1321 } 1322 errmsg_restore(saved_msg); 1323 } 1324 1325 static void 1326 objlist_clear(Objlist *list) 1327 { 1328 Objlist_Entry *elm; 1329 1330 while (!STAILQ_EMPTY(list)) { 1331 elm = STAILQ_FIRST(list); 1332 STAILQ_REMOVE_HEAD(list, link); 1333 free(elm); 1334 } 1335 } 1336 1337 static Objlist_Entry * 1338 objlist_find(Objlist *list, const Obj_Entry *obj) 1339 { 1340 Objlist_Entry *elm; 1341 1342 STAILQ_FOREACH(elm, list, link) 1343 if (elm->obj == obj) 1344 return elm; 1345 return NULL; 1346 } 1347 1348 static void 1349 objlist_init(Objlist *list) 1350 { 1351 STAILQ_INIT(list); 1352 } 1353 1354 static void 1355 objlist_push_head(Objlist *list, Obj_Entry *obj) 1356 { 1357 Objlist_Entry *elm; 1358 1359 elm = NEW(Objlist_Entry); 1360 elm->obj = obj; 1361 STAILQ_INSERT_HEAD(list, elm, link); 1362 } 1363 1364 static void 1365 objlist_push_tail(Objlist *list, Obj_Entry *obj) 1366 { 1367 Objlist_Entry *elm; 1368 1369 elm = NEW(Objlist_Entry); 1370 elm->obj = obj; 1371 STAILQ_INSERT_TAIL(list, elm, link); 1372 } 1373 1374 static void 1375 objlist_remove(Objlist *list, Obj_Entry *obj) 1376 { 1377 Objlist_Entry *elm; 1378 1379 if ((elm = objlist_find(list, obj)) != NULL) { 1380 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1381 free(elm); 1382 } 1383 } 1384 1385 /* 1386 * Remove all of the unreferenced objects from "list". 1387 */ 1388 static void 1389 objlist_remove_unref(Objlist *list) 1390 { 1391 Objlist newlist; 1392 Objlist_Entry *elm; 1393 1394 STAILQ_INIT(&newlist); 1395 while (!STAILQ_EMPTY(list)) { 1396 elm = STAILQ_FIRST(list); 1397 STAILQ_REMOVE_HEAD(list, link); 1398 if (elm->obj->refcount == 0) 1399 free(elm); 1400 else 1401 STAILQ_INSERT_TAIL(&newlist, elm, link); 1402 } 1403 *list = newlist; 1404 } 1405 1406 /* 1407 * Relocate newly-loaded shared objects. The argument is a pointer to 1408 * the Obj_Entry for the first such object. All objects from the first 1409 * to the end of the list of objects are relocated. Returns 0 on success, 1410 * or -1 on failure. 1411 */ 1412 static int 1413 relocate_objects(Obj_Entry *first, bool bind_now) 1414 { 1415 Obj_Entry *obj; 1416 1417 for (obj = first; obj != NULL; obj = obj->next) { 1418 if (obj != &obj_rtld) 1419 dbg("relocating \"%s\"", obj->path); 1420 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1421 obj->symtab == NULL || obj->strtab == NULL) { 1422 _rtld_error("%s: Shared object has no run-time symbol table", 1423 obj->path); 1424 return -1; 1425 } 1426 1427 if (obj->textrel) { 1428 /* There are relocations to the write-protected text segment. */ 1429 if (mprotect(obj->mapbase, obj->textsize, 1430 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1431 _rtld_error("%s: Cannot write-enable text segment: %s", 1432 obj->path, strerror(errno)); 1433 return -1; 1434 } 1435 } 1436 1437 /* Process the non-PLT relocations. */ 1438 if (reloc_non_plt(obj, &obj_rtld)) 1439 return -1; 1440 1441 /* 1442 * Reprotect the text segment. Make sure it is included in the 1443 * core dump since we modified it. This unfortunately causes the 1444 * entire text segment to core-out but we don't have much of a 1445 * choice. We could try to only reenable core dumps on pages 1446 * in which relocations occured but that is likely most of the text 1447 * pages anyway, and even that would not work because the rest of 1448 * the text pages would wind up as a read-only OBJT_DEFAULT object 1449 * (created due to our modifications) backed by the original OBJT_VNODE 1450 * object, and the ELF coredump code is currently only able to dump 1451 * vnode records for pure vnode-backed mappings, not vnode backings 1452 * to memory objects. 1453 */ 1454 if (obj->textrel) { 1455 madvise(obj->mapbase, obj->textsize, MADV_CORE); 1456 if (mprotect(obj->mapbase, obj->textsize, 1457 PROT_READ|PROT_EXEC) == -1) { 1458 _rtld_error("%s: Cannot write-protect text segment: %s", 1459 obj->path, strerror(errno)); 1460 return -1; 1461 } 1462 } 1463 1464 /* Process the PLT relocations. */ 1465 if (reloc_plt(obj) == -1) 1466 return -1; 1467 /* Relocate the jump slots if we are doing immediate binding. */ 1468 if (bind_now) 1469 if (reloc_jmpslots(obj) == -1) 1470 return -1; 1471 1472 1473 /* 1474 * Set up the magic number and version in the Obj_Entry. These 1475 * were checked in the crt1.o from the original ElfKit, so we 1476 * set them for backward compatibility. 1477 */ 1478 obj->magic = RTLD_MAGIC; 1479 obj->version = RTLD_VERSION; 1480 1481 /* Set the special PLT or GOT entries. */ 1482 init_pltgot(obj); 1483 } 1484 1485 return 0; 1486 } 1487 1488 /* 1489 * Cleanup procedure. It will be called (by the atexit mechanism) just 1490 * before the process exits. 1491 */ 1492 static void 1493 rtld_exit(void) 1494 { 1495 Obj_Entry *obj; 1496 1497 dbg("rtld_exit()"); 1498 /* Clear all the reference counts so the fini functions will be called. */ 1499 for (obj = obj_list; obj != NULL; obj = obj->next) 1500 obj->refcount = 0; 1501 objlist_call_fini(&list_fini); 1502 /* No need to remove the items from the list, since we are exiting. */ 1503 } 1504 1505 static void * 1506 path_enumerate(const char *path, path_enum_proc callback, void *arg) 1507 { 1508 if (path == NULL) 1509 return (NULL); 1510 1511 path += strspn(path, ":;"); 1512 while (*path != '\0') { 1513 size_t len; 1514 char *res; 1515 1516 len = strcspn(path, ":;"); 1517 res = callback(path, len, arg); 1518 1519 if (res != NULL) 1520 return (res); 1521 1522 path += len; 1523 path += strspn(path, ":;"); 1524 } 1525 1526 return (NULL); 1527 } 1528 1529 struct try_library_args { 1530 const char *name; 1531 size_t namelen; 1532 char *buffer; 1533 size_t buflen; 1534 }; 1535 1536 static void * 1537 try_library_path(const char *dir, size_t dirlen, void *param) 1538 { 1539 struct try_library_args *arg; 1540 1541 arg = param; 1542 if (*dir == '/' || trust) { 1543 char *pathname; 1544 1545 if (dirlen + 1 + arg->namelen + 1 > arg->buflen) 1546 return (NULL); 1547 1548 pathname = arg->buffer; 1549 strncpy(pathname, dir, dirlen); 1550 pathname[dirlen] = '/'; 1551 strcpy(pathname + dirlen + 1, arg->name); 1552 1553 dbg(" Trying \"%s\"", pathname); 1554 if (access(pathname, F_OK) == 0) { /* We found it */ 1555 pathname = xmalloc(dirlen + 1 + arg->namelen + 1); 1556 strcpy(pathname, arg->buffer); 1557 return (pathname); 1558 } 1559 } 1560 return (NULL); 1561 } 1562 1563 static char * 1564 search_library_path(const char *name, const char *path) 1565 { 1566 char *p; 1567 struct try_library_args arg; 1568 1569 if (path == NULL) 1570 return NULL; 1571 1572 arg.name = name; 1573 arg.namelen = strlen(name); 1574 arg.buffer = xmalloc(PATH_MAX); 1575 arg.buflen = PATH_MAX; 1576 1577 p = path_enumerate(path, try_library_path, &arg); 1578 1579 free(arg.buffer); 1580 1581 return (p); 1582 } 1583 1584 int 1585 dlclose(void *handle) 1586 { 1587 Obj_Entry *root; 1588 1589 wlock_acquire(); 1590 root = dlcheck(handle); 1591 if (root == NULL) { 1592 wlock_release(); 1593 return -1; 1594 } 1595 1596 /* Unreference the object and its dependencies. */ 1597 root->dl_refcount--; 1598 unref_dag(root); 1599 1600 if (root->refcount == 0) { 1601 /* 1602 * The object is no longer referenced, so we must unload it. 1603 * First, call the fini functions with no locks held. 1604 */ 1605 wlock_release(); 1606 objlist_call_fini(&list_fini); 1607 wlock_acquire(); 1608 objlist_remove_unref(&list_fini); 1609 1610 /* Finish cleaning up the newly-unreferenced objects. */ 1611 GDB_STATE(RT_DELETE,&root->linkmap); 1612 unload_object(root); 1613 GDB_STATE(RT_CONSISTENT,NULL); 1614 } 1615 wlock_release(); 1616 return 0; 1617 } 1618 1619 const char * 1620 dlerror(void) 1621 { 1622 char *msg = error_message; 1623 error_message = NULL; 1624 return msg; 1625 } 1626 1627 /* 1628 * This function is deprecated and has no effect. 1629 */ 1630 void 1631 dllockinit(void *context, 1632 void *(*lock_create)(void *context), 1633 void (*rlock_acquire)(void *lock), 1634 void (*wlock_acquire)(void *lock), 1635 void (*lock_release)(void *lock), 1636 void (*lock_destroy)(void *lock), 1637 void (*context_destroy)(void *context)) 1638 { 1639 static void *cur_context; 1640 static void (*cur_context_destroy)(void *); 1641 1642 /* Just destroy the context from the previous call, if necessary. */ 1643 if (cur_context_destroy != NULL) 1644 cur_context_destroy(cur_context); 1645 cur_context = context; 1646 cur_context_destroy = context_destroy; 1647 } 1648 1649 void * 1650 dlopen(const char *name, int mode) 1651 { 1652 Obj_Entry **old_obj_tail; 1653 Obj_Entry *obj; 1654 Objlist initlist; 1655 int result; 1656 1657 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1"; 1658 if (ld_tracing != NULL) 1659 environ = (char **)*get_program_var_addr("environ"); 1660 1661 objlist_init(&initlist); 1662 1663 wlock_acquire(); 1664 GDB_STATE(RT_ADD,NULL); 1665 1666 old_obj_tail = obj_tail; 1667 obj = NULL; 1668 if (name == NULL) { 1669 obj = obj_main; 1670 obj->refcount++; 1671 } else { 1672 char *path = find_library(name, obj_main); 1673 if (path != NULL) 1674 obj = load_object(path); 1675 } 1676 1677 if (obj) { 1678 obj->dl_refcount++; 1679 if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL) 1680 objlist_push_tail(&list_global, obj); 1681 mode &= RTLD_MODEMASK; 1682 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1683 assert(*old_obj_tail == obj); 1684 1685 result = load_needed_objects(obj); 1686 if (result != -1 && ld_tracing) 1687 goto trace; 1688 1689 if (result == -1 || 1690 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) { 1691 obj->dl_refcount--; 1692 unref_dag(obj); 1693 if (obj->refcount == 0) 1694 unload_object(obj); 1695 obj = NULL; 1696 } else { 1697 /* Make list of init functions to call. */ 1698 initlist_add_objects(obj, &obj->next, &initlist); 1699 } 1700 } else if (ld_tracing) 1701 goto trace; 1702 } 1703 1704 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); 1705 1706 /* Call the init functions with no locks held. */ 1707 wlock_release(); 1708 objlist_call_init(&initlist); 1709 wlock_acquire(); 1710 objlist_clear(&initlist); 1711 wlock_release(); 1712 return obj; 1713 trace: 1714 trace_loaded_objects(obj); 1715 wlock_release(); 1716 exit(0); 1717 } 1718 1719 void * 1720 dlsym(void *handle, const char *name) 1721 { 1722 const Obj_Entry *obj; 1723 unsigned long hash; 1724 const Elf_Sym *def; 1725 const Obj_Entry *defobj; 1726 1727 hash = elf_hash(name); 1728 def = NULL; 1729 defobj = NULL; 1730 1731 rlock_acquire(); 1732 if (handle == NULL || handle == RTLD_NEXT || 1733 handle == RTLD_DEFAULT || handle == RTLD_SELF) { 1734 void *retaddr; 1735 1736 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1737 if ((obj = obj_from_addr(retaddr)) == NULL) { 1738 _rtld_error("Cannot determine caller's shared object"); 1739 rlock_release(); 1740 return NULL; 1741 } 1742 if (handle == NULL) { /* Just the caller's shared object. */ 1743 def = symlook_obj(name, hash, obj, true); 1744 defobj = obj; 1745 } else if (handle == RTLD_NEXT || /* Objects after caller's */ 1746 handle == RTLD_SELF) { /* ... caller included */ 1747 if (handle == RTLD_NEXT) 1748 obj = obj->next; 1749 for (; obj != NULL; obj = obj->next) { 1750 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1751 defobj = obj; 1752 break; 1753 } 1754 } 1755 } else { 1756 assert(handle == RTLD_DEFAULT); 1757 def = symlook_default(name, hash, obj, &defobj, true); 1758 } 1759 } else { 1760 if ((obj = dlcheck(handle)) == NULL) { 1761 rlock_release(); 1762 return NULL; 1763 } 1764 1765 if (obj->mainprog) { 1766 DoneList donelist; 1767 1768 /* Search main program and all libraries loaded by it. */ 1769 donelist_init(&donelist); 1770 def = symlook_list(name, hash, &list_main, &defobj, true, 1771 &donelist); 1772 } else { 1773 /* 1774 * XXX - This isn't correct. The search should include the whole 1775 * DAG rooted at the given object. 1776 */ 1777 def = symlook_obj(name, hash, obj, true); 1778 defobj = obj; 1779 } 1780 } 1781 1782 if (def != NULL) { 1783 rlock_release(); 1784 return defobj->relocbase + def->st_value; 1785 } 1786 1787 _rtld_error("Undefined symbol \"%s\"", name); 1788 rlock_release(); 1789 return NULL; 1790 } 1791 1792 int 1793 dladdr(const void *addr, Dl_info *info) 1794 { 1795 const Obj_Entry *obj; 1796 const Elf_Sym *def; 1797 void *symbol_addr; 1798 unsigned long symoffset; 1799 1800 rlock_acquire(); 1801 obj = obj_from_addr(addr); 1802 if (obj == NULL) { 1803 _rtld_error("No shared object contains address"); 1804 rlock_release(); 1805 return 0; 1806 } 1807 info->dli_fname = obj->path; 1808 info->dli_fbase = obj->mapbase; 1809 info->dli_saddr = (void *)0; 1810 info->dli_sname = NULL; 1811 1812 /* 1813 * Walk the symbol list looking for the symbol whose address is 1814 * closest to the address sent in. 1815 */ 1816 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1817 def = obj->symtab + symoffset; 1818 1819 /* 1820 * For skip the symbol if st_shndx is either SHN_UNDEF or 1821 * SHN_COMMON. 1822 */ 1823 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1824 continue; 1825 1826 /* 1827 * If the symbol is greater than the specified address, or if it 1828 * is further away from addr than the current nearest symbol, 1829 * then reject it. 1830 */ 1831 symbol_addr = obj->relocbase + def->st_value; 1832 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1833 continue; 1834 1835 /* Update our idea of the nearest symbol. */ 1836 info->dli_sname = obj->strtab + def->st_name; 1837 info->dli_saddr = symbol_addr; 1838 1839 /* Exact match? */ 1840 if (info->dli_saddr == addr) 1841 break; 1842 } 1843 rlock_release(); 1844 return 1; 1845 } 1846 1847 int 1848 dlinfo(void *handle, int request, void *p) 1849 { 1850 const Obj_Entry *obj; 1851 int error; 1852 1853 rlock_acquire(); 1854 1855 if (handle == NULL || handle == RTLD_SELF) { 1856 void *retaddr; 1857 1858 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1859 if ((obj = obj_from_addr(retaddr)) == NULL) 1860 _rtld_error("Cannot determine caller's shared object"); 1861 } else 1862 obj = dlcheck(handle); 1863 1864 if (obj == NULL) { 1865 rlock_release(); 1866 return (-1); 1867 } 1868 1869 error = 0; 1870 switch (request) { 1871 case RTLD_DI_LINKMAP: 1872 *((struct link_map const **)p) = &obj->linkmap; 1873 break; 1874 case RTLD_DI_ORIGIN: 1875 error = rtld_dirname(obj->path, p); 1876 break; 1877 1878 case RTLD_DI_SERINFOSIZE: 1879 case RTLD_DI_SERINFO: 1880 error = do_search_info(obj, request, (struct dl_serinfo *)p); 1881 break; 1882 1883 default: 1884 _rtld_error("Invalid request %d passed to dlinfo()", request); 1885 error = -1; 1886 } 1887 1888 rlock_release(); 1889 1890 return (error); 1891 } 1892 1893 struct fill_search_info_args { 1894 int request; 1895 unsigned int flags; 1896 Dl_serinfo *serinfo; 1897 Dl_serpath *serpath; 1898 char *strspace; 1899 }; 1900 1901 static void * 1902 fill_search_info(const char *dir, size_t dirlen, void *param) 1903 { 1904 struct fill_search_info_args *arg; 1905 1906 arg = param; 1907 1908 if (arg->request == RTLD_DI_SERINFOSIZE) { 1909 arg->serinfo->dls_cnt ++; 1910 arg->serinfo->dls_size += dirlen + 1; 1911 } else { 1912 struct dl_serpath *s_entry; 1913 1914 s_entry = arg->serpath; 1915 s_entry->dls_name = arg->strspace; 1916 s_entry->dls_flags = arg->flags; 1917 1918 strncpy(arg->strspace, dir, dirlen); 1919 arg->strspace[dirlen] = '\0'; 1920 1921 arg->strspace += dirlen + 1; 1922 arg->serpath++; 1923 } 1924 1925 return (NULL); 1926 } 1927 1928 static int 1929 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info) 1930 { 1931 struct dl_serinfo _info; 1932 struct fill_search_info_args args; 1933 1934 args.request = RTLD_DI_SERINFOSIZE; 1935 args.serinfo = &_info; 1936 1937 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath); 1938 _info.dls_cnt = 0; 1939 1940 path_enumerate(ld_library_path, fill_search_info, &args); 1941 path_enumerate(obj->rpath, fill_search_info, &args); 1942 path_enumerate(gethints(), fill_search_info, &args); 1943 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args); 1944 1945 1946 if (request == RTLD_DI_SERINFOSIZE) { 1947 info->dls_size = _info.dls_size; 1948 info->dls_cnt = _info.dls_cnt; 1949 return (0); 1950 } 1951 1952 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) { 1953 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()"); 1954 return (-1); 1955 } 1956 1957 args.request = RTLD_DI_SERINFO; 1958 args.serinfo = info; 1959 args.serpath = &info->dls_serpath[0]; 1960 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt]; 1961 1962 args.flags = LA_SER_LIBPATH; 1963 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL) 1964 return (-1); 1965 1966 args.flags = LA_SER_RUNPATH; 1967 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL) 1968 return (-1); 1969 1970 args.flags = LA_SER_CONFIG; 1971 if (path_enumerate(gethints(), fill_search_info, &args) != NULL) 1972 return (-1); 1973 1974 args.flags = LA_SER_DEFAULT; 1975 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL) 1976 return (-1); 1977 return (0); 1978 } 1979 1980 static int 1981 rtld_dirname(const char *path, char *bname) 1982 { 1983 const char *endp; 1984 1985 /* Empty or NULL string gets treated as "." */ 1986 if (path == NULL || *path == '\0') { 1987 bname[0] = '.'; 1988 bname[1] = '\0'; 1989 return (0); 1990 } 1991 1992 /* Strip trailing slashes */ 1993 endp = path + strlen(path) - 1; 1994 while (endp > path && *endp == '/') 1995 endp--; 1996 1997 /* Find the start of the dir */ 1998 while (endp > path && *endp != '/') 1999 endp--; 2000 2001 /* Either the dir is "/" or there are no slashes */ 2002 if (endp == path) { 2003 bname[0] = *endp == '/' ? '/' : '.'; 2004 bname[1] = '\0'; 2005 return (0); 2006 } else { 2007 do { 2008 endp--; 2009 } while (endp > path && *endp == '/'); 2010 } 2011 2012 if (endp - path + 2 > PATH_MAX) 2013 { 2014 _rtld_error("Filename is too long: %s", path); 2015 return(-1); 2016 } 2017 2018 strncpy(bname, path, endp - path + 1); 2019 bname[endp - path + 1] = '\0'; 2020 return (0); 2021 } 2022 2023 static void 2024 linkmap_add(Obj_Entry *obj) 2025 { 2026 struct link_map *l = &obj->linkmap; 2027 struct link_map *prev; 2028 2029 obj->linkmap.l_name = obj->path; 2030 obj->linkmap.l_addr = obj->mapbase; 2031 obj->linkmap.l_ld = obj->dynamic; 2032 #ifdef __mips__ 2033 /* GDB needs load offset on MIPS to use the symbols */ 2034 obj->linkmap.l_offs = obj->relocbase; 2035 #endif 2036 2037 if (r_debug.r_map == NULL) { 2038 r_debug.r_map = l; 2039 return; 2040 } 2041 2042 /* 2043 * Scan to the end of the list, but not past the entry for the 2044 * dynamic linker, which we want to keep at the very end. 2045 */ 2046 for (prev = r_debug.r_map; 2047 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 2048 prev = prev->l_next) 2049 ; 2050 2051 /* Link in the new entry. */ 2052 l->l_prev = prev; 2053 l->l_next = prev->l_next; 2054 if (l->l_next != NULL) 2055 l->l_next->l_prev = l; 2056 prev->l_next = l; 2057 } 2058 2059 static void 2060 linkmap_delete(Obj_Entry *obj) 2061 { 2062 struct link_map *l = &obj->linkmap; 2063 2064 if (l->l_prev == NULL) { 2065 if ((r_debug.r_map = l->l_next) != NULL) 2066 l->l_next->l_prev = NULL; 2067 return; 2068 } 2069 2070 if ((l->l_prev->l_next = l->l_next) != NULL) 2071 l->l_next->l_prev = l->l_prev; 2072 } 2073 2074 /* 2075 * Function for the debugger to set a breakpoint on to gain control. 2076 * 2077 * The two parameters allow the debugger to easily find and determine 2078 * what the runtime loader is doing and to whom it is doing it. 2079 * 2080 * When the loadhook trap is hit (r_debug_state, set at program 2081 * initialization), the arguments can be found on the stack: 2082 * 2083 * +8 struct link_map *m 2084 * +4 struct r_debug *rd 2085 * +0 RetAddr 2086 */ 2087 void 2088 r_debug_state(struct r_debug* rd, struct link_map *m) 2089 { 2090 } 2091 2092 /* 2093 * Get address of the pointer variable in the main program. 2094 */ 2095 static const void ** 2096 get_program_var_addr(const char *name) 2097 { 2098 const Obj_Entry *obj; 2099 unsigned long hash; 2100 2101 hash = elf_hash(name); 2102 for (obj = obj_main; obj != NULL; obj = obj->next) { 2103 const Elf_Sym *def; 2104 2105 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 2106 const void **addr; 2107 2108 addr = (const void **)(obj->relocbase + def->st_value); 2109 return addr; 2110 } 2111 } 2112 return NULL; 2113 } 2114 2115 /* 2116 * Set a pointer variable in the main program to the given value. This 2117 * is used to set key variables such as "environ" before any of the 2118 * init functions are called. 2119 */ 2120 static void 2121 set_program_var(const char *name, const void *value) 2122 { 2123 const void **addr; 2124 2125 if ((addr = get_program_var_addr(name)) != NULL) { 2126 dbg("\"%s\": *%p <-- %p", name, addr, value); 2127 *addr = value; 2128 } 2129 } 2130 2131 /* 2132 * This is a special version of getenv which is far more efficient 2133 * at finding LD_ environment vars. 2134 */ 2135 static 2136 const char * 2137 _getenv_ld(const char *id) 2138 { 2139 const char *envp; 2140 int i, j; 2141 int idlen = strlen(id); 2142 2143 if (ld_index == LD_ARY_CACHE) 2144 return(getenv(id)); 2145 if (ld_index == 0) { 2146 for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) { 2147 if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_') 2148 ld_ary[j++] = envp; 2149 } 2150 if (j == 0) 2151 ld_ary[j++] = ""; 2152 ld_index = j; 2153 } 2154 for (i = ld_index - 1; i >= 0; --i) { 2155 if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=') 2156 return(ld_ary[i] + idlen + 1); 2157 } 2158 return(NULL); 2159 } 2160 2161 /* 2162 * Given a symbol name in a referencing object, find the corresponding 2163 * definition of the symbol. Returns a pointer to the symbol, or NULL if 2164 * no definition was found. Returns a pointer to the Obj_Entry of the 2165 * defining object via the reference parameter DEFOBJ_OUT. 2166 */ 2167 static const Elf_Sym * 2168 symlook_default(const char *name, unsigned long hash, 2169 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) 2170 { 2171 DoneList donelist; 2172 const Elf_Sym *def; 2173 const Elf_Sym *symp; 2174 const Obj_Entry *obj; 2175 const Obj_Entry *defobj; 2176 const Objlist_Entry *elm; 2177 def = NULL; 2178 defobj = NULL; 2179 donelist_init(&donelist); 2180 2181 /* Look first in the referencing object if linked symbolically. */ 2182 if (refobj->symbolic && !donelist_check(&donelist, refobj)) { 2183 symp = symlook_obj(name, hash, refobj, in_plt); 2184 if (symp != NULL) { 2185 def = symp; 2186 defobj = refobj; 2187 } 2188 } 2189 2190 /* Search all objects loaded at program start up. */ 2191 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2192 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); 2193 if (symp != NULL && 2194 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2195 def = symp; 2196 defobj = obj; 2197 } 2198 } 2199 2200 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */ 2201 STAILQ_FOREACH(elm, &list_global, link) { 2202 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2203 break; 2204 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2205 &donelist); 2206 if (symp != NULL && 2207 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2208 def = symp; 2209 defobj = obj; 2210 } 2211 } 2212 2213 /* Search all dlopened DAGs containing the referencing object. */ 2214 STAILQ_FOREACH(elm, &refobj->dldags, link) { 2215 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2216 break; 2217 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2218 &donelist); 2219 if (symp != NULL && 2220 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2221 def = symp; 2222 defobj = obj; 2223 } 2224 } 2225 2226 /* 2227 * Search the dynamic linker itself, and possibly resolve the 2228 * symbol from there. This is how the application links to 2229 * dynamic linker services such as dlopen. Only the values listed 2230 * in the "exports" array can be resolved from the dynamic linker. 2231 */ 2232 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2233 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 2234 if (symp != NULL && is_exported(symp)) { 2235 def = symp; 2236 defobj = &obj_rtld; 2237 } 2238 } 2239 2240 if (def != NULL) 2241 *defobj_out = defobj; 2242 return def; 2243 } 2244 2245 static const Elf_Sym * 2246 symlook_list(const char *name, unsigned long hash, Objlist *objlist, 2247 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 2248 { 2249 const Elf_Sym *symp; 2250 const Elf_Sym *def; 2251 const Obj_Entry *defobj; 2252 const Objlist_Entry *elm; 2253 2254 def = NULL; 2255 defobj = NULL; 2256 STAILQ_FOREACH(elm, objlist, link) { 2257 if (donelist_check(dlp, elm->obj)) 2258 continue; 2259 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 2260 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 2261 def = symp; 2262 defobj = elm->obj; 2263 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 2264 break; 2265 } 2266 } 2267 } 2268 if (def != NULL) 2269 *defobj_out = defobj; 2270 return def; 2271 } 2272 2273 /* 2274 * Search the symbol table of a single shared object for a symbol of 2275 * the given name. Returns a pointer to the symbol, or NULL if no 2276 * definition was found. 2277 * 2278 * The symbol's hash value is passed in for efficiency reasons; that 2279 * eliminates many recomputations of the hash value. 2280 */ 2281 const Elf_Sym * 2282 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 2283 bool in_plt) 2284 { 2285 if (obj->buckets != NULL) { 2286 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 2287 2288 while (symnum != STN_UNDEF) { 2289 const Elf_Sym *symp; 2290 const char *strp; 2291 2292 if (symnum >= obj->nchains) 2293 return NULL; /* Bad object */ 2294 symp = obj->symtab + symnum; 2295 strp = obj->strtab + symp->st_name; 2296 2297 if (name[0] == strp[0] && strcmp(name, strp) == 0) 2298 return symp->st_shndx != SHN_UNDEF || 2299 (!in_plt && symp->st_value != 0 && 2300 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 2301 2302 symnum = obj->chains[symnum]; 2303 } 2304 } 2305 return NULL; 2306 } 2307 2308 static void 2309 trace_loaded_objects(Obj_Entry *obj) 2310 { 2311 const char *fmt1, *fmt2, *fmt, *main_local; 2312 int c; 2313 2314 if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 2315 main_local = ""; 2316 2317 if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 2318 fmt1 = "\t%o => %p (%x)\n"; 2319 2320 if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 2321 fmt2 = "\t%o (%x)\n"; 2322 2323 for (; obj; obj = obj->next) { 2324 Needed_Entry *needed; 2325 char *name, *path; 2326 bool is_lib; 2327 2328 for (needed = obj->needed; needed; needed = needed->next) { 2329 if (needed->obj != NULL) { 2330 if (needed->obj->traced) 2331 continue; 2332 needed->obj->traced = true; 2333 path = needed->obj->path; 2334 } else 2335 path = "not found"; 2336 2337 name = (char *)obj->strtab + needed->name; 2338 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 2339 2340 fmt = is_lib ? fmt1 : fmt2; 2341 while ((c = *fmt++) != '\0') { 2342 switch (c) { 2343 default: 2344 putchar(c); 2345 continue; 2346 case '\\': 2347 switch (c = *fmt) { 2348 case '\0': 2349 continue; 2350 case 'n': 2351 putchar('\n'); 2352 break; 2353 case 't': 2354 putchar('\t'); 2355 break; 2356 } 2357 break; 2358 case '%': 2359 switch (c = *fmt) { 2360 case '\0': 2361 continue; 2362 case '%': 2363 default: 2364 putchar(c); 2365 break; 2366 case 'A': 2367 printf("%s", main_local); 2368 break; 2369 case 'a': 2370 printf("%s", obj_main->path); 2371 break; 2372 case 'o': 2373 printf("%s", name); 2374 break; 2375 #if 0 2376 case 'm': 2377 printf("%d", sodp->sod_major); 2378 break; 2379 case 'n': 2380 printf("%d", sodp->sod_minor); 2381 break; 2382 #endif 2383 case 'p': 2384 printf("%s", path); 2385 break; 2386 case 'x': 2387 printf("%p", needed->obj ? needed->obj->mapbase : 0); 2388 break; 2389 } 2390 break; 2391 } 2392 ++fmt; 2393 } 2394 } 2395 } 2396 } 2397 2398 /* 2399 * Unload a dlopened object and its dependencies from memory and from 2400 * our data structures. It is assumed that the DAG rooted in the 2401 * object has already been unreferenced, and that the object has a 2402 * reference count of 0. 2403 */ 2404 static void 2405 unload_object(Obj_Entry *root) 2406 { 2407 Obj_Entry *obj; 2408 Obj_Entry **linkp; 2409 2410 assert(root->refcount == 0); 2411 2412 /* 2413 * Pass over the DAG removing unreferenced objects from 2414 * appropriate lists. 2415 */ 2416 unlink_object(root); 2417 2418 /* Unmap all objects that are no longer referenced. */ 2419 linkp = &obj_list->next; 2420 while ((obj = *linkp) != NULL) { 2421 if (obj->refcount == 0) { 2422 dbg("unloading \"%s\"", obj->path); 2423 munmap(obj->mapbase, obj->mapsize); 2424 linkmap_delete(obj); 2425 *linkp = obj->next; 2426 obj_count--; 2427 obj_free(obj); 2428 } else 2429 linkp = &obj->next; 2430 } 2431 obj_tail = linkp; 2432 } 2433 2434 static void 2435 unlink_object(Obj_Entry *root) 2436 { 2437 const Needed_Entry *needed; 2438 Objlist_Entry *elm; 2439 2440 if (root->refcount == 0) { 2441 /* Remove the object from the RTLD_GLOBAL list. */ 2442 objlist_remove(&list_global, root); 2443 2444 /* Remove the object from all objects' DAG lists. */ 2445 STAILQ_FOREACH(elm, &root->dagmembers , link) 2446 objlist_remove(&elm->obj->dldags, root); 2447 } 2448 2449 for (needed = root->needed; needed != NULL; needed = needed->next) 2450 if (needed->obj != NULL) 2451 unlink_object(needed->obj); 2452 } 2453 2454 static void 2455 unref_dag(Obj_Entry *root) 2456 { 2457 const Needed_Entry *needed; 2458 2459 if (root->refcount == 0) 2460 return; 2461 root->refcount--; 2462 if (root->refcount == 0) 2463 for (needed = root->needed; needed != NULL; needed = needed->next) 2464 if (needed->obj != NULL) 2465 unref_dag(needed->obj); 2466 } 2467