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 * $FreeBSD$ 27 */ 28 29 /* 30 * Dynamic linker for ELF. 31 * 32 * John Polstra <jdp@polstra.com>. 33 */ 34 35 #ifndef __GNUC__ 36 #error "GCC is needed to compile this file" 37 #endif 38 39 #include <sys/param.h> 40 #include <sys/mman.h> 41 #include <sys/stat.h> 42 43 #include <dlfcn.h> 44 #include <err.h> 45 #include <errno.h> 46 #include <fcntl.h> 47 #include <stdarg.h> 48 #include <stdio.h> 49 #include <stdlib.h> 50 #include <string.h> 51 #include <unistd.h> 52 53 #include "debug.h" 54 #include "rtld.h" 55 56 #define END_SYM "_end" 57 #define PATH_RTLD "/usr/libexec/ld-elf.so.1" 58 59 /* Types. */ 60 typedef void (*func_ptr_type)(); 61 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg); 62 63 /* 64 * This structure provides a reentrant way to keep a list of objects and 65 * check which ones have already been processed in some way. 66 */ 67 typedef struct Struct_DoneList { 68 const Obj_Entry **objs; /* Array of object pointers */ 69 unsigned int num_alloc; /* Allocated size of the array */ 70 unsigned int num_used; /* Number of array slots used */ 71 } DoneList; 72 73 /* 74 * Function declarations. 75 */ 76 static const char *basename(const char *); 77 static void die(void); 78 static void digest_dynamic(Obj_Entry *, int); 79 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *); 80 static Obj_Entry *dlcheck(void *); 81 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *); 82 static bool donelist_check(DoneList *, const Obj_Entry *); 83 static void errmsg_restore(char *); 84 static char *errmsg_save(void); 85 static void *fill_search_info(const char *, size_t, void *); 86 static char *find_library(const char *, const Obj_Entry *); 87 static const char *gethints(void); 88 static void init_dag(Obj_Entry *); 89 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *); 90 static void init_rtld(caddr_t); 91 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list); 92 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, 93 Objlist *list); 94 static bool is_exported(const Elf_Sym *); 95 static void linkmap_add(Obj_Entry *); 96 static void linkmap_delete(Obj_Entry *); 97 static int load_needed_objects(Obj_Entry *); 98 static int load_preload_objects(void); 99 static Obj_Entry *load_object(char *); 100 static void lock_check(void); 101 static Obj_Entry *obj_from_addr(const void *); 102 static void objlist_call_fini(Objlist *); 103 static void objlist_call_init(Objlist *); 104 static void objlist_clear(Objlist *); 105 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *); 106 static void objlist_init(Objlist *); 107 static void objlist_push_head(Objlist *, Obj_Entry *); 108 static void objlist_push_tail(Objlist *, Obj_Entry *); 109 static void objlist_remove(Objlist *, Obj_Entry *); 110 static void objlist_remove_unref(Objlist *); 111 static void *path_enumerate(const char *, path_enum_proc, void *); 112 static int relocate_objects(Obj_Entry *, bool, Obj_Entry *); 113 static int rtld_dirname(const char *, char *); 114 static void rtld_exit(void); 115 static char *search_library_path(const char *, const char *); 116 static const void **get_program_var_addr(const char *name); 117 static void set_program_var(const char *, const void *); 118 static const Elf_Sym *symlook_default(const char *, unsigned long hash, 119 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt); 120 static const Elf_Sym *symlook_list(const char *, unsigned long, 121 Objlist *, const Obj_Entry **, bool in_plt, DoneList *); 122 static void trace_loaded_objects(Obj_Entry *obj); 123 static void unlink_object(Obj_Entry *); 124 static void unload_object(Obj_Entry *); 125 static void unref_dag(Obj_Entry *); 126 127 void r_debug_state(struct r_debug*, struct link_map*); 128 129 /* 130 * Data declarations. 131 */ 132 static char *error_message; /* Message for dlerror(), or NULL */ 133 struct r_debug r_debug; /* for GDB; */ 134 static bool trust; /* False for setuid and setgid programs */ 135 static char *ld_bind_now; /* Environment variable for immediate binding */ 136 static char *ld_debug; /* Environment variable for debugging */ 137 static char *ld_library_path; /* Environment variable for search path */ 138 static char *ld_preload; /* Environment variable for libraries to 139 load first */ 140 static char *ld_tracing; /* Called from ldd to print libs */ 141 static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 142 static Obj_Entry **obj_tail; /* Link field of last object in list */ 143 static Obj_Entry *obj_main; /* The main program shared object */ 144 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 145 static unsigned int obj_count; /* Number of objects in obj_list */ 146 147 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 148 STAILQ_HEAD_INITIALIZER(list_global); 149 static Objlist list_main = /* Objects loaded at program startup */ 150 STAILQ_HEAD_INITIALIZER(list_main); 151 static Objlist list_fini = /* Objects needing fini() calls */ 152 STAILQ_HEAD_INITIALIZER(list_fini); 153 154 static LockInfo lockinfo; 155 156 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 157 158 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); 159 160 extern Elf_Dyn _DYNAMIC; 161 #pragma weak _DYNAMIC 162 163 /* 164 * These are the functions the dynamic linker exports to application 165 * programs. They are the only symbols the dynamic linker is willing 166 * to export from itself. 167 */ 168 static func_ptr_type exports[] = { 169 (func_ptr_type) &_rtld_error, 170 (func_ptr_type) &dlclose, 171 (func_ptr_type) &dlerror, 172 (func_ptr_type) &dlopen, 173 (func_ptr_type) &dlsym, 174 (func_ptr_type) &dladdr, 175 (func_ptr_type) &dllockinit, 176 (func_ptr_type) &dlinfo, 177 NULL 178 }; 179 180 /* 181 * Global declarations normally provided by crt1. The dynamic linker is 182 * not built with crt1, so we have to provide them ourselves. 183 */ 184 char *__progname; 185 char **environ; 186 187 /* 188 * Fill in a DoneList with an allocation large enough to hold all of 189 * the currently-loaded objects. Keep this as a macro since it calls 190 * alloca and we want that to occur within the scope of the caller. 191 */ 192 #define donelist_init(dlp) \ 193 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ 194 assert((dlp)->objs != NULL), \ 195 (dlp)->num_alloc = obj_count, \ 196 (dlp)->num_used = 0) 197 198 static __inline void 199 rlock_acquire(void) 200 { 201 lockinfo.rlock_acquire(lockinfo.thelock); 202 atomic_incr_int(&lockinfo.rcount); 203 lock_check(); 204 } 205 206 static __inline void 207 wlock_acquire(void) 208 { 209 lockinfo.wlock_acquire(lockinfo.thelock); 210 atomic_incr_int(&lockinfo.wcount); 211 lock_check(); 212 } 213 214 static __inline void 215 rlock_release(void) 216 { 217 atomic_decr_int(&lockinfo.rcount); 218 lockinfo.rlock_release(lockinfo.thelock); 219 } 220 221 static __inline void 222 wlock_release(void) 223 { 224 atomic_decr_int(&lockinfo.wcount); 225 lockinfo.wlock_release(lockinfo.thelock); 226 } 227 228 /* 229 * Main entry point for dynamic linking. The first argument is the 230 * stack pointer. The stack is expected to be laid out as described 231 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 232 * Specifically, the stack pointer points to a word containing 233 * ARGC. Following that in the stack is a null-terminated sequence 234 * of pointers to argument strings. Then comes a null-terminated 235 * sequence of pointers to environment strings. Finally, there is a 236 * sequence of "auxiliary vector" entries. 237 * 238 * The second argument points to a place to store the dynamic linker's 239 * exit procedure pointer and the third to a place to store the main 240 * program's object. 241 * 242 * The return value is the main program's entry point. 243 */ 244 func_ptr_type 245 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 246 { 247 Elf_Auxinfo *aux_info[AT_COUNT]; 248 int i; 249 int argc; 250 char **argv; 251 char **env; 252 Elf_Auxinfo *aux; 253 Elf_Auxinfo *auxp; 254 const char *argv0; 255 Obj_Entry *obj; 256 Obj_Entry **preload_tail; 257 Objlist initlist; 258 259 /* 260 * On entry, the dynamic linker itself has not been relocated yet. 261 * Be very careful not to reference any global data until after 262 * init_rtld has returned. It is OK to reference file-scope statics 263 * and string constants, and to call static and global functions. 264 */ 265 266 /* Find the auxiliary vector on the stack. */ 267 argc = *sp++; 268 argv = (char **) sp; 269 sp += argc + 1; /* Skip over arguments and NULL terminator */ 270 env = (char **) sp; 271 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 272 ; 273 aux = (Elf_Auxinfo *) sp; 274 275 /* Digest the auxiliary vector. */ 276 for (i = 0; i < AT_COUNT; i++) 277 aux_info[i] = NULL; 278 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 279 if (auxp->a_type < AT_COUNT) 280 aux_info[auxp->a_type] = auxp; 281 } 282 283 /* Initialize and relocate ourselves. */ 284 assert(aux_info[AT_BASE] != NULL); 285 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 286 287 __progname = obj_rtld.path; 288 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 289 environ = env; 290 291 trust = geteuid() == getuid() && getegid() == getgid(); 292 293 ld_bind_now = getenv("LD_BIND_NOW"); 294 if (trust) { 295 ld_debug = getenv("LD_DEBUG"); 296 ld_library_path = getenv("LD_LIBRARY_PATH"); 297 ld_preload = getenv("LD_PRELOAD"); 298 } 299 ld_tracing = getenv("LD_TRACE_LOADED_OBJECTS"); 300 301 if (ld_debug != NULL && *ld_debug != '\0') 302 debug = 1; 303 dbg("%s is initialized, base address = %p", __progname, 304 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 305 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 306 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 307 308 /* 309 * Load the main program, or process its program header if it is 310 * already loaded. 311 */ 312 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 313 int fd = aux_info[AT_EXECFD]->a_un.a_val; 314 dbg("loading main program"); 315 obj_main = map_object(fd, argv0, NULL); 316 close(fd); 317 if (obj_main == NULL) 318 die(); 319 } else { /* Main program already loaded. */ 320 const Elf_Phdr *phdr; 321 int phnum; 322 caddr_t entry; 323 324 dbg("processing main program's program header"); 325 assert(aux_info[AT_PHDR] != NULL); 326 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 327 assert(aux_info[AT_PHNUM] != NULL); 328 phnum = aux_info[AT_PHNUM]->a_un.a_val; 329 assert(aux_info[AT_PHENT] != NULL); 330 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 331 assert(aux_info[AT_ENTRY] != NULL); 332 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 333 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 334 die(); 335 } 336 337 obj_main->path = xstrdup(argv0); 338 obj_main->mainprog = true; 339 340 /* 341 * Get the actual dynamic linker pathname from the executable if 342 * possible. (It should always be possible.) That ensures that 343 * gdb will find the right dynamic linker even if a non-standard 344 * one is being used. 345 */ 346 if (obj_main->interp != NULL && 347 strcmp(obj_main->interp, obj_rtld.path) != 0) { 348 free(obj_rtld.path); 349 obj_rtld.path = xstrdup(obj_main->interp); 350 } 351 352 digest_dynamic(obj_main, 0); 353 354 linkmap_add(obj_main); 355 linkmap_add(&obj_rtld); 356 357 /* Link the main program into the list of objects. */ 358 *obj_tail = obj_main; 359 obj_tail = &obj_main->next; 360 obj_count++; 361 obj_main->refcount++; 362 /* Make sure we don't call the main program's init and fini functions. */ 363 obj_main->init = obj_main->fini = NULL; 364 365 /* Initialize a fake symbol for resolving undefined weak references. */ 366 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 367 sym_zero.st_shndx = SHN_UNDEF; 368 369 dbg("loading LD_PRELOAD libraries"); 370 if (load_preload_objects() == -1) 371 die(); 372 preload_tail = obj_tail; 373 374 dbg("loading needed objects"); 375 if (load_needed_objects(obj_main) == -1) 376 die(); 377 378 /* Make a list of all objects loaded at startup. */ 379 for (obj = obj_list; obj != NULL; obj = obj->next) 380 objlist_push_tail(&list_main, obj); 381 382 if (ld_tracing) { /* We're done */ 383 trace_loaded_objects(obj_main); 384 exit(0); 385 } 386 387 if (relocate_objects(obj_main, 388 ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1) 389 die(); 390 391 dbg("doing copy relocations"); 392 if (do_copy_relocations(obj_main) == -1) 393 die(); 394 395 dbg("initializing key program variables"); 396 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 397 set_program_var("environ", env); 398 399 dbg("initializing thread locks"); 400 lockdflt_init(&lockinfo); 401 lockinfo.thelock = lockinfo.lock_create(lockinfo.context); 402 403 /* Make a list of init functions to call. */ 404 objlist_init(&initlist); 405 initlist_add_objects(obj_list, preload_tail, &initlist); 406 407 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ 408 409 objlist_call_init(&initlist); 410 wlock_acquire(); 411 objlist_clear(&initlist); 412 wlock_release(); 413 414 dbg("transferring control to program entry point = %p", obj_main->entry); 415 416 /* Return the exit procedure and the program entry point. */ 417 *exit_proc = rtld_exit; 418 *objp = obj_main; 419 return (func_ptr_type) obj_main->entry; 420 } 421 422 Elf_Addr 423 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 424 { 425 const Elf_Rel *rel; 426 const Elf_Sym *def; 427 const Obj_Entry *defobj; 428 Elf_Addr *where; 429 Elf_Addr target; 430 431 rlock_acquire(); 432 if (obj->pltrel) 433 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 434 else 435 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 436 437 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 438 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 439 if (def == NULL) 440 die(); 441 442 target = (Elf_Addr)(defobj->relocbase + def->st_value); 443 444 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 445 defobj->strtab + def->st_name, basename(obj->path), 446 (void *)target, basename(defobj->path)); 447 448 /* 449 * Write the new contents for the jmpslot. Note that depending on 450 * architecture, the value which we need to return back to the 451 * lazy binding trampoline may or may not be the target 452 * address. The value returned from reloc_jmpslot() is the value 453 * that the trampoline needs. 454 */ 455 target = reloc_jmpslot(where, target, defobj, obj, rel); 456 rlock_release(); 457 return target; 458 } 459 460 /* 461 * Error reporting function. Use it like printf. If formats the message 462 * into a buffer, and sets things up so that the next call to dlerror() 463 * will return the message. 464 */ 465 void 466 _rtld_error(const char *fmt, ...) 467 { 468 static char buf[512]; 469 va_list ap; 470 471 va_start(ap, fmt); 472 vsnprintf(buf, sizeof buf, fmt, ap); 473 error_message = buf; 474 va_end(ap); 475 } 476 477 /* 478 * Return a dynamically-allocated copy of the current error message, if any. 479 */ 480 static char * 481 errmsg_save(void) 482 { 483 return error_message == NULL ? NULL : xstrdup(error_message); 484 } 485 486 /* 487 * Restore the current error message from a copy which was previously saved 488 * by errmsg_save(). The copy is freed. 489 */ 490 static void 491 errmsg_restore(char *saved_msg) 492 { 493 if (saved_msg == NULL) 494 error_message = NULL; 495 else { 496 _rtld_error("%s", saved_msg); 497 free(saved_msg); 498 } 499 } 500 501 static const char * 502 basename(const char *name) 503 { 504 const char *p = strrchr(name, '/'); 505 return p != NULL ? p + 1 : name; 506 } 507 508 static void 509 die(void) 510 { 511 const char *msg = dlerror(); 512 513 if (msg == NULL) 514 msg = "Fatal error"; 515 errx(1, "%s", msg); 516 } 517 518 /* 519 * Process a shared object's DYNAMIC section, and save the important 520 * information in its Obj_Entry structure. 521 */ 522 static void 523 digest_dynamic(Obj_Entry *obj, int early) 524 { 525 const Elf_Dyn *dynp; 526 Needed_Entry **needed_tail = &obj->needed; 527 const Elf_Dyn *dyn_rpath = NULL; 528 int plttype = DT_REL; 529 530 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 531 switch (dynp->d_tag) { 532 533 case DT_REL: 534 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 535 break; 536 537 case DT_RELSZ: 538 obj->relsize = dynp->d_un.d_val; 539 break; 540 541 case DT_RELENT: 542 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 543 break; 544 545 case DT_JMPREL: 546 obj->pltrel = (const Elf_Rel *) 547 (obj->relocbase + dynp->d_un.d_ptr); 548 break; 549 550 case DT_PLTRELSZ: 551 obj->pltrelsize = dynp->d_un.d_val; 552 break; 553 554 case DT_RELA: 555 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 556 break; 557 558 case DT_RELASZ: 559 obj->relasize = dynp->d_un.d_val; 560 break; 561 562 case DT_RELAENT: 563 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 564 break; 565 566 case DT_PLTREL: 567 plttype = dynp->d_un.d_val; 568 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 569 break; 570 571 case DT_SYMTAB: 572 obj->symtab = (const Elf_Sym *) 573 (obj->relocbase + dynp->d_un.d_ptr); 574 break; 575 576 case DT_SYMENT: 577 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 578 break; 579 580 case DT_STRTAB: 581 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 582 break; 583 584 case DT_STRSZ: 585 obj->strsize = dynp->d_un.d_val; 586 break; 587 588 case DT_HASH: 589 { 590 const Elf_Hashelt *hashtab = (const Elf_Hashelt *) 591 (obj->relocbase + dynp->d_un.d_ptr); 592 obj->nbuckets = hashtab[0]; 593 obj->nchains = hashtab[1]; 594 obj->buckets = hashtab + 2; 595 obj->chains = obj->buckets + obj->nbuckets; 596 } 597 break; 598 599 case DT_NEEDED: 600 if (!obj->rtld) { 601 Needed_Entry *nep = NEW(Needed_Entry); 602 nep->name = dynp->d_un.d_val; 603 nep->obj = NULL; 604 nep->next = NULL; 605 606 *needed_tail = nep; 607 needed_tail = &nep->next; 608 } 609 break; 610 611 case DT_PLTGOT: 612 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 613 break; 614 615 case DT_TEXTREL: 616 obj->textrel = true; 617 break; 618 619 case DT_SYMBOLIC: 620 obj->symbolic = true; 621 break; 622 623 case DT_RPATH: 624 /* 625 * We have to wait until later to process this, because we 626 * might not have gotten the address of the string table yet. 627 */ 628 dyn_rpath = dynp; 629 break; 630 631 case DT_SONAME: 632 /* Not used by the dynamic linker. */ 633 break; 634 635 case DT_INIT: 636 obj->init = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr); 637 break; 638 639 case DT_FINI: 640 obj->fini = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr); 641 break; 642 643 case DT_DEBUG: 644 /* XXX - not implemented yet */ 645 if (!early) 646 dbg("Filling in DT_DEBUG entry"); 647 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 648 break; 649 650 default: 651 if (!early) { 652 dbg("Ignoring d_tag %ld = %#lx", (long)dynp->d_tag, 653 (long)dynp->d_tag); 654 } 655 break; 656 } 657 } 658 659 obj->traced = false; 660 661 if (plttype == DT_RELA) { 662 obj->pltrela = (const Elf_Rela *) obj->pltrel; 663 obj->pltrel = NULL; 664 obj->pltrelasize = obj->pltrelsize; 665 obj->pltrelsize = 0; 666 } 667 668 if (dyn_rpath != NULL) 669 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 670 } 671 672 /* 673 * Process a shared object's program header. This is used only for the 674 * main program, when the kernel has already loaded the main program 675 * into memory before calling the dynamic linker. It creates and 676 * returns an Obj_Entry structure. 677 */ 678 static Obj_Entry * 679 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 680 { 681 Obj_Entry *obj; 682 const Elf_Phdr *phlimit = phdr + phnum; 683 const Elf_Phdr *ph; 684 int nsegs = 0; 685 686 obj = obj_new(); 687 for (ph = phdr; ph < phlimit; ph++) { 688 switch (ph->p_type) { 689 690 case PT_PHDR: 691 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 692 _rtld_error("%s: invalid PT_PHDR", path); 693 return NULL; 694 } 695 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 696 obj->phsize = ph->p_memsz; 697 break; 698 699 case PT_INTERP: 700 obj->interp = (const char *) ph->p_vaddr; 701 break; 702 703 case PT_LOAD: 704 if (nsegs == 0) { /* First load segment */ 705 obj->vaddrbase = trunc_page(ph->p_vaddr); 706 obj->mapbase = (caddr_t) obj->vaddrbase; 707 obj->relocbase = obj->mapbase - obj->vaddrbase; 708 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 709 obj->vaddrbase; 710 } else { /* Last load segment */ 711 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 712 obj->vaddrbase; 713 } 714 nsegs++; 715 break; 716 717 case PT_DYNAMIC: 718 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 719 break; 720 } 721 } 722 if (nsegs < 1) { 723 _rtld_error("%s: too few PT_LOAD segments", path); 724 return NULL; 725 } 726 727 obj->entry = entry; 728 return obj; 729 } 730 731 static Obj_Entry * 732 dlcheck(void *handle) 733 { 734 Obj_Entry *obj; 735 736 for (obj = obj_list; obj != NULL; obj = obj->next) 737 if (obj == (Obj_Entry *) handle) 738 break; 739 740 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { 741 _rtld_error("Invalid shared object handle %p", handle); 742 return NULL; 743 } 744 return obj; 745 } 746 747 /* 748 * If the given object is already in the donelist, return true. Otherwise 749 * add the object to the list and return false. 750 */ 751 static bool 752 donelist_check(DoneList *dlp, const Obj_Entry *obj) 753 { 754 unsigned int i; 755 756 for (i = 0; i < dlp->num_used; i++) 757 if (dlp->objs[i] == obj) 758 return true; 759 /* 760 * Our donelist allocation should always be sufficient. But if 761 * our threads locking isn't working properly, more shared objects 762 * could have been loaded since we allocated the list. That should 763 * never happen, but we'll handle it properly just in case it does. 764 */ 765 if (dlp->num_used < dlp->num_alloc) 766 dlp->objs[dlp->num_used++] = obj; 767 return false; 768 } 769 770 /* 771 * Hash function for symbol table lookup. Don't even think about changing 772 * this. It is specified by the System V ABI. 773 */ 774 unsigned long 775 elf_hash(const char *name) 776 { 777 const unsigned char *p = (const unsigned char *) name; 778 unsigned long h = 0; 779 unsigned long g; 780 781 while (*p != '\0') { 782 h = (h << 4) + *p++; 783 if ((g = h & 0xf0000000) != 0) 784 h ^= g >> 24; 785 h &= ~g; 786 } 787 return h; 788 } 789 790 /* 791 * Find the library with the given name, and return its full pathname. 792 * The returned string is dynamically allocated. Generates an error 793 * message and returns NULL if the library cannot be found. 794 * 795 * If the second argument is non-NULL, then it refers to an already- 796 * loaded shared object, whose library search path will be searched. 797 * 798 * The search order is: 799 * rpath in the referencing file 800 * LD_LIBRARY_PATH 801 * ldconfig hints 802 * /usr/lib 803 */ 804 static char * 805 find_library(const char *name, const Obj_Entry *refobj) 806 { 807 char *pathname; 808 809 if (strchr(name, '/') != NULL) { /* Hard coded pathname */ 810 if (name[0] != '/' && !trust) { 811 _rtld_error("Absolute pathname required for shared object \"%s\"", 812 name); 813 return NULL; 814 } 815 return xstrdup(name); 816 } 817 818 dbg(" Searching for \"%s\"", name); 819 820 if ((pathname = search_library_path(name, ld_library_path)) != NULL || 821 (refobj != NULL && 822 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 823 (pathname = search_library_path(name, gethints())) != NULL || 824 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 825 return pathname; 826 827 _rtld_error("Shared object \"%s\" not found", name); 828 return NULL; 829 } 830 831 /* 832 * Given a symbol number in a referencing object, find the corresponding 833 * definition of the symbol. Returns a pointer to the symbol, or NULL if 834 * no definition was found. Returns a pointer to the Obj_Entry of the 835 * defining object via the reference parameter DEFOBJ_OUT. 836 */ 837 const Elf_Sym * 838 find_symdef(unsigned long symnum, const Obj_Entry *refobj, 839 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) 840 { 841 const Elf_Sym *ref; 842 const Elf_Sym *def; 843 const Obj_Entry *defobj; 844 const char *name; 845 unsigned long hash; 846 847 /* 848 * If we have already found this symbol, get the information from 849 * the cache. 850 */ 851 if (symnum >= refobj->nchains) 852 return NULL; /* Bad object */ 853 if (cache != NULL && cache[symnum].sym != NULL) { 854 *defobj_out = cache[symnum].obj; 855 return cache[symnum].sym; 856 } 857 858 ref = refobj->symtab + symnum; 859 name = refobj->strtab + ref->st_name; 860 defobj = NULL; 861 862 /* 863 * We don't have to do a full scale lookup if the symbol is local. 864 * We know it will bind to the instance in this load module; to 865 * which we already have a pointer (ie ref). By not doing a lookup, 866 * we not only improve performance, but it also avoids unresolvable 867 * symbols when local symbols are not in the hash table. This has 868 * been seen with the ia64 toolchain. 869 */ 870 if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) { 871 if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) { 872 _rtld_error("%s: Bogus symbol table entry %lu", refobj->path, 873 symnum); 874 } 875 hash = elf_hash(name); 876 def = symlook_default(name, hash, refobj, &defobj, in_plt); 877 } else { 878 def = ref; 879 defobj = refobj; 880 } 881 882 /* 883 * If we found no definition and the reference is weak, treat the 884 * symbol as having the value zero. 885 */ 886 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 887 def = &sym_zero; 888 defobj = obj_main; 889 } 890 891 if (def != NULL) { 892 *defobj_out = defobj; 893 /* Record the information in the cache to avoid subsequent lookups. */ 894 if (cache != NULL) { 895 cache[symnum].sym = def; 896 cache[symnum].obj = defobj; 897 } 898 } else { 899 if (refobj != &obj_rtld) 900 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 901 } 902 return def; 903 } 904 905 /* 906 * Return the search path from the ldconfig hints file, reading it if 907 * necessary. Returns NULL if there are problems with the hints file, 908 * or if the search path there is empty. 909 */ 910 static const char * 911 gethints(void) 912 { 913 static char *hints; 914 915 if (hints == NULL) { 916 int fd; 917 struct elfhints_hdr hdr; 918 char *p; 919 920 /* Keep from trying again in case the hints file is bad. */ 921 hints = ""; 922 923 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 924 return NULL; 925 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 926 hdr.magic != ELFHINTS_MAGIC || 927 hdr.version != 1) { 928 close(fd); 929 return NULL; 930 } 931 p = xmalloc(hdr.dirlistlen + 1); 932 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 933 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { 934 free(p); 935 close(fd); 936 return NULL; 937 } 938 hints = p; 939 close(fd); 940 } 941 return hints[0] != '\0' ? hints : NULL; 942 } 943 944 static void 945 init_dag(Obj_Entry *root) 946 { 947 DoneList donelist; 948 949 donelist_init(&donelist); 950 init_dag1(root, root, &donelist); 951 } 952 953 static void 954 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) 955 { 956 const Needed_Entry *needed; 957 958 if (donelist_check(dlp, obj)) 959 return; 960 objlist_push_tail(&obj->dldags, root); 961 objlist_push_tail(&root->dagmembers, obj); 962 for (needed = obj->needed; needed != NULL; needed = needed->next) 963 if (needed->obj != NULL) 964 init_dag1(root, needed->obj, dlp); 965 } 966 967 /* 968 * Initialize the dynamic linker. The argument is the address at which 969 * the dynamic linker has been mapped into memory. The primary task of 970 * this function is to relocate the dynamic linker. 971 */ 972 static void 973 init_rtld(caddr_t mapbase) 974 { 975 Obj_Entry objtmp; /* Temporary rtld object */ 976 977 /* 978 * Conjure up an Obj_Entry structure for the dynamic linker. 979 * 980 * The "path" member can't be initialized yet because string constatns 981 * cannot yet be acessed. Below we will set it correctly. 982 */ 983 objtmp.path = NULL; 984 objtmp.rtld = true; 985 objtmp.mapbase = mapbase; 986 #ifdef PIC 987 objtmp.relocbase = mapbase; 988 #endif 989 if (&_DYNAMIC != 0) { 990 objtmp.dynamic = rtld_dynamic(&objtmp); 991 digest_dynamic(&objtmp, 1); 992 assert(objtmp.needed == NULL); 993 assert(!objtmp.textrel); 994 995 /* 996 * Temporarily put the dynamic linker entry into the object list, so 997 * that symbols can be found. 998 */ 999 1000 relocate_objects(&objtmp, true, &objtmp); 1001 } 1002 1003 /* Initialize the object list. */ 1004 obj_tail = &obj_list; 1005 1006 /* Now that non-local variables can be accesses, copy out obj_rtld. */ 1007 memcpy(&obj_rtld, &objtmp, sizeof(obj_rtld)); 1008 1009 /* Replace the path with a dynamically allocated copy. */ 1010 obj_rtld.path = xstrdup(PATH_RTLD); 1011 1012 r_debug.r_brk = r_debug_state; 1013 r_debug.r_state = RT_CONSISTENT; 1014 } 1015 1016 /* 1017 * Add the init functions from a needed object list (and its recursive 1018 * needed objects) to "list". This is not used directly; it is a helper 1019 * function for initlist_add_objects(). The write lock must be held 1020 * when this function is called. 1021 */ 1022 static void 1023 initlist_add_neededs(Needed_Entry *needed, Objlist *list) 1024 { 1025 /* Recursively process the successor needed objects. */ 1026 if (needed->next != NULL) 1027 initlist_add_neededs(needed->next, list); 1028 1029 /* Process the current needed object. */ 1030 if (needed->obj != NULL) 1031 initlist_add_objects(needed->obj, &needed->obj->next, list); 1032 } 1033 1034 /* 1035 * Scan all of the DAGs rooted in the range of objects from "obj" to 1036 * "tail" and add their init functions to "list". This recurses over 1037 * the DAGs and ensure the proper init ordering such that each object's 1038 * needed libraries are initialized before the object itself. At the 1039 * same time, this function adds the objects to the global finalization 1040 * list "list_fini" in the opposite order. The write lock must be 1041 * held when this function is called. 1042 */ 1043 static void 1044 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) 1045 { 1046 if (obj->init_done) 1047 return; 1048 obj->init_done = true; 1049 1050 /* Recursively process the successor objects. */ 1051 if (&obj->next != tail) 1052 initlist_add_objects(obj->next, tail, list); 1053 1054 /* Recursively process the needed objects. */ 1055 if (obj->needed != NULL) 1056 initlist_add_neededs(obj->needed, list); 1057 1058 /* Add the object to the init list. */ 1059 if (obj->init != NULL) 1060 objlist_push_tail(list, obj); 1061 1062 /* Add the object to the global fini list in the reverse order. */ 1063 if (obj->fini != NULL) 1064 objlist_push_head(&list_fini, obj); 1065 } 1066 1067 #ifndef FPTR_TARGET 1068 #define FPTR_TARGET(f) ((Elf_Addr) (f)) 1069 #endif 1070 1071 static bool 1072 is_exported(const Elf_Sym *def) 1073 { 1074 Elf_Addr value; 1075 const func_ptr_type *p; 1076 1077 value = (Elf_Addr)(obj_rtld.relocbase + def->st_value); 1078 for (p = exports; *p != NULL; p++) 1079 if (FPTR_TARGET(*p) == value) 1080 return true; 1081 return false; 1082 } 1083 1084 /* 1085 * Given a shared object, traverse its list of needed objects, and load 1086 * each of them. Returns 0 on success. Generates an error message and 1087 * returns -1 on failure. 1088 */ 1089 static int 1090 load_needed_objects(Obj_Entry *first) 1091 { 1092 Obj_Entry *obj; 1093 1094 for (obj = first; obj != NULL; obj = obj->next) { 1095 Needed_Entry *needed; 1096 1097 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1098 const char *name = obj->strtab + needed->name; 1099 char *path = find_library(name, obj); 1100 1101 needed->obj = NULL; 1102 if (path == NULL && !ld_tracing) 1103 return -1; 1104 1105 if (path) { 1106 needed->obj = load_object(path); 1107 if (needed->obj == NULL && !ld_tracing) 1108 return -1; /* XXX - cleanup */ 1109 } 1110 } 1111 } 1112 1113 return 0; 1114 } 1115 1116 static int 1117 load_preload_objects(void) 1118 { 1119 char *p = ld_preload; 1120 static const char delim[] = " \t:;"; 1121 1122 if (p == NULL) 1123 return NULL; 1124 1125 p += strspn(p, delim); 1126 while (*p != '\0') { 1127 size_t len = strcspn(p, delim); 1128 char *path; 1129 char savech; 1130 1131 savech = p[len]; 1132 p[len] = '\0'; 1133 if ((path = find_library(p, NULL)) == NULL) 1134 return -1; 1135 if (load_object(path) == NULL) 1136 return -1; /* XXX - cleanup */ 1137 p[len] = savech; 1138 p += len; 1139 p += strspn(p, delim); 1140 } 1141 return 0; 1142 } 1143 1144 /* 1145 * Load a shared object into memory, if it is not already loaded. The 1146 * argument must be a string allocated on the heap. This function assumes 1147 * responsibility for freeing it when necessary. 1148 * 1149 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1150 * on failure. 1151 */ 1152 static Obj_Entry * 1153 load_object(char *path) 1154 { 1155 Obj_Entry *obj; 1156 int fd = -1; 1157 struct stat sb; 1158 1159 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1160 if (strcmp(obj->path, path) == 0) 1161 break; 1162 1163 /* 1164 * If we didn't find a match by pathname, open the file and check 1165 * again by device and inode. This avoids false mismatches caused 1166 * by multiple links or ".." in pathnames. 1167 * 1168 * To avoid a race, we open the file and use fstat() rather than 1169 * using stat(). 1170 */ 1171 if (obj == NULL) { 1172 if ((fd = open(path, O_RDONLY)) == -1) { 1173 _rtld_error("Cannot open \"%s\"", path); 1174 return NULL; 1175 } 1176 if (fstat(fd, &sb) == -1) { 1177 _rtld_error("Cannot fstat \"%s\"", path); 1178 close(fd); 1179 return NULL; 1180 } 1181 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1182 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) { 1183 close(fd); 1184 break; 1185 } 1186 } 1187 } 1188 1189 if (obj == NULL) { /* First use of this object, so we must map it in */ 1190 dbg("loading \"%s\"", path); 1191 obj = map_object(fd, path, &sb); 1192 close(fd); 1193 if (obj == NULL) { 1194 free(path); 1195 return NULL; 1196 } 1197 1198 obj->path = path; 1199 digest_dynamic(obj, 0); 1200 1201 *obj_tail = obj; 1202 obj_tail = &obj->next; 1203 obj_count++; 1204 linkmap_add(obj); /* for GDB & dlinfo() */ 1205 1206 dbg(" %p .. %p: %s", obj->mapbase, 1207 obj->mapbase + obj->mapsize - 1, obj->path); 1208 if (obj->textrel) 1209 dbg(" WARNING: %s has impure text", obj->path); 1210 } else 1211 free(path); 1212 1213 obj->refcount++; 1214 return obj; 1215 } 1216 1217 /* 1218 * Check for locking violations and die if one is found. 1219 */ 1220 static void 1221 lock_check(void) 1222 { 1223 int rcount, wcount; 1224 1225 rcount = lockinfo.rcount; 1226 wcount = lockinfo.wcount; 1227 assert(rcount >= 0); 1228 assert(wcount >= 0); 1229 if (wcount > 1 || (wcount != 0 && rcount != 0)) { 1230 _rtld_error("Application locking error: %d readers and %d writers" 1231 " in dynamic linker. See DLLOCKINIT(3) in manual pages.", 1232 rcount, wcount); 1233 die(); 1234 } 1235 } 1236 1237 static Obj_Entry * 1238 obj_from_addr(const void *addr) 1239 { 1240 unsigned long endhash; 1241 Obj_Entry *obj; 1242 1243 endhash = elf_hash(END_SYM); 1244 for (obj = obj_list; obj != NULL; obj = obj->next) { 1245 const Elf_Sym *endsym; 1246 1247 if (addr < (void *) obj->mapbase) 1248 continue; 1249 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL) 1250 continue; /* No "end" symbol?! */ 1251 if (addr < (void *) (obj->relocbase + endsym->st_value)) 1252 return obj; 1253 } 1254 return NULL; 1255 } 1256 1257 /* 1258 * Call the finalization functions for each of the objects in "list" 1259 * which are unreferenced. All of the objects are expected to have 1260 * non-NULL fini functions. 1261 */ 1262 static void 1263 objlist_call_fini(Objlist *list) 1264 { 1265 Objlist_Entry *elm; 1266 char *saved_msg; 1267 1268 /* 1269 * Preserve the current error message since a fini function might 1270 * call into the dynamic linker and overwrite it. 1271 */ 1272 saved_msg = errmsg_save(); 1273 STAILQ_FOREACH(elm, list, link) { 1274 if (elm->obj->refcount == 0) { 1275 dbg("calling fini function for %s at %p", elm->obj->path, 1276 (void *)elm->obj->fini); 1277 call_initfini_pointer(elm->obj, elm->obj->fini); 1278 } 1279 } 1280 errmsg_restore(saved_msg); 1281 } 1282 1283 /* 1284 * Call the initialization functions for each of the objects in 1285 * "list". All of the objects are expected to have non-NULL init 1286 * functions. 1287 */ 1288 static void 1289 objlist_call_init(Objlist *list) 1290 { 1291 Objlist_Entry *elm; 1292 char *saved_msg; 1293 1294 /* 1295 * Preserve the current error message since an init function might 1296 * call into the dynamic linker and overwrite it. 1297 */ 1298 saved_msg = errmsg_save(); 1299 STAILQ_FOREACH(elm, list, link) { 1300 dbg("calling init function for %s at %p", elm->obj->path, 1301 (void *)elm->obj->init); 1302 call_initfini_pointer(elm->obj, elm->obj->init); 1303 } 1304 errmsg_restore(saved_msg); 1305 } 1306 1307 static void 1308 objlist_clear(Objlist *list) 1309 { 1310 Objlist_Entry *elm; 1311 1312 while (!STAILQ_EMPTY(list)) { 1313 elm = STAILQ_FIRST(list); 1314 STAILQ_REMOVE_HEAD(list, link); 1315 free(elm); 1316 } 1317 } 1318 1319 static Objlist_Entry * 1320 objlist_find(Objlist *list, const Obj_Entry *obj) 1321 { 1322 Objlist_Entry *elm; 1323 1324 STAILQ_FOREACH(elm, list, link) 1325 if (elm->obj == obj) 1326 return elm; 1327 return NULL; 1328 } 1329 1330 static void 1331 objlist_init(Objlist *list) 1332 { 1333 STAILQ_INIT(list); 1334 } 1335 1336 static void 1337 objlist_push_head(Objlist *list, Obj_Entry *obj) 1338 { 1339 Objlist_Entry *elm; 1340 1341 elm = NEW(Objlist_Entry); 1342 elm->obj = obj; 1343 STAILQ_INSERT_HEAD(list, elm, link); 1344 } 1345 1346 static void 1347 objlist_push_tail(Objlist *list, Obj_Entry *obj) 1348 { 1349 Objlist_Entry *elm; 1350 1351 elm = NEW(Objlist_Entry); 1352 elm->obj = obj; 1353 STAILQ_INSERT_TAIL(list, elm, link); 1354 } 1355 1356 static void 1357 objlist_remove(Objlist *list, Obj_Entry *obj) 1358 { 1359 Objlist_Entry *elm; 1360 1361 if ((elm = objlist_find(list, obj)) != NULL) { 1362 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1363 free(elm); 1364 } 1365 } 1366 1367 /* 1368 * Remove all of the unreferenced objects from "list". 1369 */ 1370 static void 1371 objlist_remove_unref(Objlist *list) 1372 { 1373 Objlist newlist; 1374 Objlist_Entry *elm; 1375 1376 STAILQ_INIT(&newlist); 1377 while (!STAILQ_EMPTY(list)) { 1378 elm = STAILQ_FIRST(list); 1379 STAILQ_REMOVE_HEAD(list, link); 1380 if (elm->obj->refcount == 0) 1381 free(elm); 1382 else 1383 STAILQ_INSERT_TAIL(&newlist, elm, link); 1384 } 1385 *list = newlist; 1386 } 1387 1388 /* 1389 * Relocate newly-loaded shared objects. The argument is a pointer to 1390 * the Obj_Entry for the first such object. All objects from the first 1391 * to the end of the list of objects are relocated. Returns 0 on success, 1392 * or -1 on failure. 1393 */ 1394 static int 1395 relocate_objects(Obj_Entry *first, bool bind_now, Obj_Entry *rtldobj) 1396 { 1397 Obj_Entry *obj; 1398 1399 for (obj = first; obj != NULL; obj = obj->next) { 1400 if (obj != rtldobj) 1401 dbg("relocating \"%s\"", obj->path); 1402 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1403 obj->symtab == NULL || obj->strtab == NULL) { 1404 _rtld_error("%s: Shared object has no run-time symbol table", 1405 obj->path); 1406 return -1; 1407 } 1408 1409 if (obj->textrel) { 1410 /* There are relocations to the write-protected text segment. */ 1411 if (mprotect(obj->mapbase, obj->textsize, 1412 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1413 _rtld_error("%s: Cannot write-enable text segment: %s", 1414 obj->path, strerror(errno)); 1415 return -1; 1416 } 1417 } 1418 1419 /* Process the non-PLT relocations. */ 1420 if (reloc_non_plt(obj, rtldobj)) 1421 return -1; 1422 1423 if (obj->textrel) { /* Re-protected the text segment. */ 1424 if (mprotect(obj->mapbase, obj->textsize, 1425 PROT_READ|PROT_EXEC) == -1) { 1426 _rtld_error("%s: Cannot write-protect text segment: %s", 1427 obj->path, strerror(errno)); 1428 return -1; 1429 } 1430 } 1431 1432 /* Process the PLT relocations. */ 1433 if (reloc_plt(obj) == -1) 1434 return -1; 1435 /* Relocate the jump slots if we are doing immediate binding. */ 1436 if (bind_now) 1437 if (reloc_jmpslots(obj) == -1) 1438 return -1; 1439 1440 1441 /* 1442 * Set up the magic number and version in the Obj_Entry. These 1443 * were checked in the crt1.o from the original ElfKit, so we 1444 * set them for backward compatibility. 1445 */ 1446 obj->magic = RTLD_MAGIC; 1447 obj->version = RTLD_VERSION; 1448 1449 /* Set the special PLT or GOT entries. */ 1450 init_pltgot(obj); 1451 } 1452 1453 return 0; 1454 } 1455 1456 /* 1457 * Cleanup procedure. It will be called (by the atexit mechanism) just 1458 * before the process exits. 1459 */ 1460 static void 1461 rtld_exit(void) 1462 { 1463 Obj_Entry *obj; 1464 1465 dbg("rtld_exit()"); 1466 /* Clear all the reference counts so the fini functions will be called. */ 1467 for (obj = obj_list; obj != NULL; obj = obj->next) 1468 obj->refcount = 0; 1469 objlist_call_fini(&list_fini); 1470 /* No need to remove the items from the list, since we are exiting. */ 1471 } 1472 1473 static void * 1474 path_enumerate(const char *path, path_enum_proc callback, void *arg) 1475 { 1476 if (path == NULL) 1477 return (NULL); 1478 1479 path += strspn(path, ":;"); 1480 while (*path != '\0') { 1481 size_t len; 1482 char *res; 1483 1484 len = strcspn(path, ":;"); 1485 res = callback(path, len, arg); 1486 1487 if (res != NULL) 1488 return (res); 1489 1490 path += len; 1491 path += strspn(path, ":;"); 1492 } 1493 1494 return (NULL); 1495 } 1496 1497 struct try_library_args { 1498 const char *name; 1499 size_t namelen; 1500 char *buffer; 1501 size_t buflen; 1502 }; 1503 1504 static void * 1505 try_library_path(const char *dir, size_t dirlen, void *param) 1506 { 1507 struct try_library_args *arg; 1508 1509 arg = param; 1510 if (*dir == '/' || trust) { 1511 char *pathname; 1512 1513 if (dirlen + 1 + arg->namelen + 1 > arg->buflen) 1514 return (NULL); 1515 1516 pathname = arg->buffer; 1517 strncpy(pathname, dir, dirlen); 1518 pathname[dirlen] = '/'; 1519 strcpy(pathname + dirlen + 1, arg->name); 1520 1521 dbg(" Trying \"%s\"", pathname); 1522 if (access(pathname, F_OK) == 0) { /* We found it */ 1523 pathname = xmalloc(dirlen + 1 + arg->namelen + 1); 1524 strcpy(pathname, arg->buffer); 1525 return (pathname); 1526 } 1527 } 1528 return (NULL); 1529 } 1530 1531 static char * 1532 search_library_path(const char *name, const char *path) 1533 { 1534 char *p; 1535 struct try_library_args arg; 1536 1537 if (path == NULL) 1538 return NULL; 1539 1540 arg.name = name; 1541 arg.namelen = strlen(name); 1542 arg.buffer = xmalloc(PATH_MAX); 1543 arg.buflen = PATH_MAX; 1544 1545 p = path_enumerate(path, try_library_path, &arg); 1546 1547 free(arg.buffer); 1548 1549 return (p); 1550 } 1551 1552 int 1553 dlclose(void *handle) 1554 { 1555 Obj_Entry *root; 1556 1557 wlock_acquire(); 1558 root = dlcheck(handle); 1559 if (root == NULL) { 1560 wlock_release(); 1561 return -1; 1562 } 1563 1564 /* Unreference the object and its dependencies. */ 1565 root->dl_refcount--; 1566 unref_dag(root); 1567 1568 if (root->refcount == 0) { 1569 /* 1570 * The object is no longer referenced, so we must unload it. 1571 * First, call the fini functions with no locks held. 1572 */ 1573 wlock_release(); 1574 objlist_call_fini(&list_fini); 1575 wlock_acquire(); 1576 objlist_remove_unref(&list_fini); 1577 1578 /* Finish cleaning up the newly-unreferenced objects. */ 1579 GDB_STATE(RT_DELETE,&root->linkmap); 1580 unload_object(root); 1581 GDB_STATE(RT_CONSISTENT,NULL); 1582 } 1583 wlock_release(); 1584 return 0; 1585 } 1586 1587 const char * 1588 dlerror(void) 1589 { 1590 char *msg = error_message; 1591 error_message = NULL; 1592 return msg; 1593 } 1594 1595 /* 1596 * This function is deprecated and has no effect. 1597 */ 1598 void 1599 dllockinit(void *context, 1600 void *(*lock_create)(void *context), 1601 void (*rlock_acquire)(void *lock), 1602 void (*wlock_acquire)(void *lock), 1603 void (*lock_release)(void *lock), 1604 void (*lock_destroy)(void *lock), 1605 void (*context_destroy)(void *context)) 1606 { 1607 static void *cur_context; 1608 static void (*cur_context_destroy)(void *); 1609 1610 /* Just destroy the context from the previous call, if necessary. */ 1611 if (cur_context_destroy != NULL) 1612 cur_context_destroy(cur_context); 1613 cur_context = context; 1614 cur_context_destroy = context_destroy; 1615 } 1616 1617 void * 1618 dlopen(const char *name, int mode) 1619 { 1620 Obj_Entry **old_obj_tail; 1621 Obj_Entry *obj; 1622 Objlist initlist; 1623 int result; 1624 1625 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1"; 1626 if (ld_tracing != NULL) 1627 environ = (char **)*get_program_var_addr("environ"); 1628 1629 objlist_init(&initlist); 1630 1631 wlock_acquire(); 1632 GDB_STATE(RT_ADD,NULL); 1633 1634 old_obj_tail = obj_tail; 1635 obj = NULL; 1636 if (name == NULL) { 1637 obj = obj_main; 1638 obj->refcount++; 1639 } else { 1640 char *path = find_library(name, obj_main); 1641 if (path != NULL) 1642 obj = load_object(path); 1643 } 1644 1645 if (obj) { 1646 obj->dl_refcount++; 1647 if (mode & RTLD_GLOBAL && objlist_find(&list_global, obj) == NULL) 1648 objlist_push_tail(&list_global, obj); 1649 mode &= RTLD_MODEMASK; 1650 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1651 assert(*old_obj_tail == obj); 1652 1653 result = load_needed_objects(obj); 1654 if (result != -1 && ld_tracing) 1655 goto trace; 1656 1657 if (result == -1 || 1658 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW, 1659 &obj_rtld)) == -1) { 1660 obj->dl_refcount--; 1661 unref_dag(obj); 1662 if (obj->refcount == 0) 1663 unload_object(obj); 1664 obj = NULL; 1665 } else { 1666 /* Make list of init functions to call. */ 1667 initlist_add_objects(obj, &obj->next, &initlist); 1668 } 1669 } else if (ld_tracing) 1670 goto trace; 1671 } 1672 1673 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); 1674 1675 /* Call the init functions with no locks held. */ 1676 wlock_release(); 1677 objlist_call_init(&initlist); 1678 wlock_acquire(); 1679 objlist_clear(&initlist); 1680 wlock_release(); 1681 return obj; 1682 trace: 1683 trace_loaded_objects(obj); 1684 wlock_release(); 1685 exit(0); 1686 } 1687 1688 void * 1689 dlsym(void *handle, const char *name) 1690 { 1691 const Obj_Entry *obj; 1692 unsigned long hash; 1693 const Elf_Sym *def; 1694 const Obj_Entry *defobj; 1695 1696 hash = elf_hash(name); 1697 def = NULL; 1698 defobj = NULL; 1699 1700 rlock_acquire(); 1701 if (handle == NULL || handle == RTLD_NEXT || 1702 handle == RTLD_DEFAULT || handle == RTLD_SELF) { 1703 void *retaddr; 1704 1705 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1706 if ((obj = obj_from_addr(retaddr)) == NULL) { 1707 _rtld_error("Cannot determine caller's shared object"); 1708 rlock_release(); 1709 return NULL; 1710 } 1711 if (handle == NULL) { /* Just the caller's shared object. */ 1712 def = symlook_obj(name, hash, obj, true); 1713 defobj = obj; 1714 } else if (handle == RTLD_NEXT || /* Objects after caller's */ 1715 handle == RTLD_SELF) { /* ... caller included */ 1716 if (handle == RTLD_NEXT) 1717 obj = obj->next; 1718 for (; obj != NULL; obj = obj->next) { 1719 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1720 defobj = obj; 1721 break; 1722 } 1723 } 1724 } else { 1725 assert(handle == RTLD_DEFAULT); 1726 def = symlook_default(name, hash, obj, &defobj, true); 1727 } 1728 } else { 1729 if ((obj = dlcheck(handle)) == NULL) { 1730 rlock_release(); 1731 return NULL; 1732 } 1733 1734 if (obj->mainprog) { 1735 DoneList donelist; 1736 1737 /* Search main program and all libraries loaded by it. */ 1738 donelist_init(&donelist); 1739 def = symlook_list(name, hash, &list_main, &defobj, true, 1740 &donelist); 1741 } else { 1742 /* 1743 * XXX - This isn't correct. The search should include the whole 1744 * DAG rooted at the given object. 1745 */ 1746 def = symlook_obj(name, hash, obj, true); 1747 defobj = obj; 1748 } 1749 } 1750 1751 if (def != NULL) { 1752 rlock_release(); 1753 1754 /* 1755 * The value required by the caller is derived from the value 1756 * of the symbol. For the ia64 architecture, we need to 1757 * construct a function descriptor which the caller can use to 1758 * call the function with the right 'gp' value. For other 1759 * architectures and for non-functions, the value is simply 1760 * the relocated value of the symbol. 1761 */ 1762 if (ELF_ST_TYPE(def->st_info) == STT_FUNC) 1763 return make_function_pointer(def, defobj); 1764 else 1765 return defobj->relocbase + def->st_value; 1766 } 1767 1768 _rtld_error("Undefined symbol \"%s\"", name); 1769 rlock_release(); 1770 return NULL; 1771 } 1772 1773 int 1774 dladdr(const void *addr, Dl_info *info) 1775 { 1776 const Obj_Entry *obj; 1777 const Elf_Sym *def; 1778 void *symbol_addr; 1779 unsigned long symoffset; 1780 1781 rlock_acquire(); 1782 obj = obj_from_addr(addr); 1783 if (obj == NULL) { 1784 _rtld_error("No shared object contains address"); 1785 rlock_release(); 1786 return 0; 1787 } 1788 info->dli_fname = obj->path; 1789 info->dli_fbase = obj->mapbase; 1790 info->dli_saddr = (void *)0; 1791 info->dli_sname = NULL; 1792 1793 /* 1794 * Walk the symbol list looking for the symbol whose address is 1795 * closest to the address sent in. 1796 */ 1797 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1798 def = obj->symtab + symoffset; 1799 1800 /* 1801 * For skip the symbol if st_shndx is either SHN_UNDEF or 1802 * SHN_COMMON. 1803 */ 1804 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1805 continue; 1806 1807 /* 1808 * If the symbol is greater than the specified address, or if it 1809 * is further away from addr than the current nearest symbol, 1810 * then reject it. 1811 */ 1812 symbol_addr = obj->relocbase + def->st_value; 1813 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1814 continue; 1815 1816 /* Update our idea of the nearest symbol. */ 1817 info->dli_sname = obj->strtab + def->st_name; 1818 info->dli_saddr = symbol_addr; 1819 1820 /* Exact match? */ 1821 if (info->dli_saddr == addr) 1822 break; 1823 } 1824 rlock_release(); 1825 return 1; 1826 } 1827 1828 int 1829 dlinfo(void *handle, int request, void *p) 1830 { 1831 const Obj_Entry *obj; 1832 int error; 1833 1834 rlock_acquire(); 1835 1836 if (handle == NULL || handle == RTLD_SELF) { 1837 void *retaddr; 1838 1839 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1840 if ((obj = obj_from_addr(retaddr)) == NULL) 1841 _rtld_error("Cannot determine caller's shared object"); 1842 } else 1843 obj = dlcheck(handle); 1844 1845 if (obj == NULL) { 1846 rlock_release(); 1847 return (-1); 1848 } 1849 1850 error = 0; 1851 switch (request) { 1852 case RTLD_DI_LINKMAP: 1853 *((struct link_map const **)p) = &obj->linkmap; 1854 break; 1855 case RTLD_DI_ORIGIN: 1856 error = rtld_dirname(obj->path, p); 1857 break; 1858 1859 case RTLD_DI_SERINFOSIZE: 1860 case RTLD_DI_SERINFO: 1861 error = do_search_info(obj, request, (struct dl_serinfo *)p); 1862 break; 1863 1864 default: 1865 _rtld_error("Invalid request %d passed to dlinfo()", request); 1866 error = -1; 1867 } 1868 1869 rlock_release(); 1870 1871 return (error); 1872 } 1873 1874 struct fill_search_info_args { 1875 int request; 1876 unsigned int flags; 1877 Dl_serinfo *serinfo; 1878 Dl_serpath *serpath; 1879 char *strspace; 1880 }; 1881 1882 static void * 1883 fill_search_info(const char *dir, size_t dirlen, void *param) 1884 { 1885 struct fill_search_info_args *arg; 1886 1887 arg = param; 1888 1889 if (arg->request == RTLD_DI_SERINFOSIZE) { 1890 arg->serinfo->dls_cnt ++; 1891 arg->serinfo->dls_size += dirlen + 1; 1892 } else { 1893 struct dl_serpath *s_entry; 1894 1895 s_entry = arg->serpath; 1896 s_entry->dls_name = arg->strspace; 1897 s_entry->dls_flags = arg->flags; 1898 1899 strncpy(arg->strspace, dir, dirlen); 1900 arg->strspace[dirlen] = '\0'; 1901 1902 arg->strspace += dirlen + 1; 1903 arg->serpath++; 1904 } 1905 1906 return (NULL); 1907 } 1908 1909 static int 1910 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info) 1911 { 1912 struct dl_serinfo _info; 1913 struct fill_search_info_args args; 1914 1915 args.request = RTLD_DI_SERINFOSIZE; 1916 args.serinfo = &_info; 1917 1918 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath); 1919 _info.dls_cnt = 0; 1920 1921 path_enumerate(ld_library_path, fill_search_info, &args); 1922 path_enumerate(obj->rpath, fill_search_info, &args); 1923 path_enumerate(gethints(), fill_search_info, &args); 1924 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args); 1925 1926 1927 if (request == RTLD_DI_SERINFOSIZE) { 1928 info->dls_size = _info.dls_size; 1929 info->dls_cnt = _info.dls_cnt; 1930 return (0); 1931 } 1932 1933 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) { 1934 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()"); 1935 return (-1); 1936 } 1937 1938 args.request = RTLD_DI_SERINFO; 1939 args.serinfo = info; 1940 args.serpath = &info->dls_serpath[0]; 1941 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt]; 1942 1943 args.flags = LA_SER_LIBPATH; 1944 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL) 1945 return (-1); 1946 1947 args.flags = LA_SER_RUNPATH; 1948 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL) 1949 return (-1); 1950 1951 args.flags = LA_SER_CONFIG; 1952 if (path_enumerate(gethints(), fill_search_info, &args) != NULL) 1953 return (-1); 1954 1955 args.flags = LA_SER_DEFAULT; 1956 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL) 1957 return (-1); 1958 return (0); 1959 } 1960 1961 static int 1962 rtld_dirname(const char *path, char *bname) 1963 { 1964 const char *endp; 1965 1966 /* Empty or NULL string gets treated as "." */ 1967 if (path == NULL || *path == '\0') { 1968 bname[0] = '.'; 1969 bname[1] = '\0'; 1970 return (0); 1971 } 1972 1973 /* Strip trailing slashes */ 1974 endp = path + strlen(path) - 1; 1975 while (endp > path && *endp == '/') 1976 endp--; 1977 1978 /* Find the start of the dir */ 1979 while (endp > path && *endp != '/') 1980 endp--; 1981 1982 /* Either the dir is "/" or there are no slashes */ 1983 if (endp == path) { 1984 bname[0] = *endp == '/' ? '/' : '.'; 1985 bname[1] = '\0'; 1986 return (0); 1987 } else { 1988 do { 1989 endp--; 1990 } while (endp > path && *endp == '/'); 1991 } 1992 1993 if (endp - path + 2 > PATH_MAX) 1994 { 1995 _rtld_error("Filename is too long: %s", path); 1996 return(-1); 1997 } 1998 1999 strncpy(bname, path, endp - path + 1); 2000 bname[endp - path + 1] = '\0'; 2001 return (0); 2002 } 2003 2004 static void 2005 linkmap_add(Obj_Entry *obj) 2006 { 2007 struct link_map *l = &obj->linkmap; 2008 struct link_map *prev; 2009 2010 obj->linkmap.l_name = obj->path; 2011 obj->linkmap.l_addr = obj->mapbase; 2012 obj->linkmap.l_ld = obj->dynamic; 2013 #ifdef __mips__ 2014 /* GDB needs load offset on MIPS to use the symbols */ 2015 obj->linkmap.l_offs = obj->relocbase; 2016 #endif 2017 2018 if (r_debug.r_map == NULL) { 2019 r_debug.r_map = l; 2020 return; 2021 } 2022 2023 /* 2024 * Scan to the end of the list, but not past the entry for the 2025 * dynamic linker, which we want to keep at the very end. 2026 */ 2027 for (prev = r_debug.r_map; 2028 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 2029 prev = prev->l_next) 2030 ; 2031 2032 /* Link in the new entry. */ 2033 l->l_prev = prev; 2034 l->l_next = prev->l_next; 2035 if (l->l_next != NULL) 2036 l->l_next->l_prev = l; 2037 prev->l_next = l; 2038 } 2039 2040 static void 2041 linkmap_delete(Obj_Entry *obj) 2042 { 2043 struct link_map *l = &obj->linkmap; 2044 2045 if (l->l_prev == NULL) { 2046 if ((r_debug.r_map = l->l_next) != NULL) 2047 l->l_next->l_prev = NULL; 2048 return; 2049 } 2050 2051 if ((l->l_prev->l_next = l->l_next) != NULL) 2052 l->l_next->l_prev = l->l_prev; 2053 } 2054 2055 /* 2056 * Function for the debugger to set a breakpoint on to gain control. 2057 * 2058 * The two parameters allow the debugger to easily find and determine 2059 * what the runtime loader is doing and to whom it is doing it. 2060 * 2061 * When the loadhook trap is hit (r_debug_state, set at program 2062 * initialization), the arguments can be found on the stack: 2063 * 2064 * +8 struct link_map *m 2065 * +4 struct r_debug *rd 2066 * +0 RetAddr 2067 */ 2068 void 2069 r_debug_state(struct r_debug* rd, struct link_map *m) 2070 { 2071 } 2072 2073 /* 2074 * Get address of the pointer variable in the main program. 2075 */ 2076 static const void ** 2077 get_program_var_addr(const char *name) 2078 { 2079 const Obj_Entry *obj; 2080 unsigned long hash; 2081 2082 hash = elf_hash(name); 2083 for (obj = obj_main; obj != NULL; obj = obj->next) { 2084 const Elf_Sym *def; 2085 2086 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 2087 const void **addr; 2088 2089 addr = (const void **)(obj->relocbase + def->st_value); 2090 return addr; 2091 } 2092 } 2093 return NULL; 2094 } 2095 2096 /* 2097 * Set a pointer variable in the main program to the given value. This 2098 * is used to set key variables such as "environ" before any of the 2099 * init functions are called. 2100 */ 2101 static void 2102 set_program_var(const char *name, const void *value) 2103 { 2104 const void **addr; 2105 2106 if ((addr = get_program_var_addr(name)) != NULL) { 2107 dbg("\"%s\": *%p <-- %p", name, addr, value); 2108 *addr = value; 2109 } 2110 } 2111 2112 /* 2113 * Given a symbol name in a referencing object, find the corresponding 2114 * definition of the symbol. Returns a pointer to the symbol, or NULL if 2115 * no definition was found. Returns a pointer to the Obj_Entry of the 2116 * defining object via the reference parameter DEFOBJ_OUT. 2117 */ 2118 static const Elf_Sym * 2119 symlook_default(const char *name, unsigned long hash, 2120 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) 2121 { 2122 DoneList donelist; 2123 const Elf_Sym *def; 2124 const Elf_Sym *symp; 2125 const Obj_Entry *obj; 2126 const Obj_Entry *defobj; 2127 const Objlist_Entry *elm; 2128 def = NULL; 2129 defobj = NULL; 2130 donelist_init(&donelist); 2131 2132 /* Look first in the referencing object if linked symbolically. */ 2133 if (refobj->symbolic && !donelist_check(&donelist, refobj)) { 2134 symp = symlook_obj(name, hash, refobj, in_plt); 2135 if (symp != NULL) { 2136 def = symp; 2137 defobj = refobj; 2138 } 2139 } 2140 2141 /* Search all objects loaded at program start up. */ 2142 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2143 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); 2144 if (symp != NULL && 2145 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2146 def = symp; 2147 defobj = obj; 2148 } 2149 } 2150 2151 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */ 2152 STAILQ_FOREACH(elm, &list_global, link) { 2153 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2154 break; 2155 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2156 &donelist); 2157 if (symp != NULL && 2158 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2159 def = symp; 2160 defobj = obj; 2161 } 2162 } 2163 2164 /* Search all dlopened DAGs containing the referencing object. */ 2165 STAILQ_FOREACH(elm, &refobj->dldags, link) { 2166 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2167 break; 2168 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2169 &donelist); 2170 if (symp != NULL && 2171 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2172 def = symp; 2173 defobj = obj; 2174 } 2175 } 2176 2177 /* 2178 * Search the dynamic linker itself, and possibly resolve the 2179 * symbol from there. This is how the application links to 2180 * dynamic linker services such as dlopen. Only the values listed 2181 * in the "exports" array can be resolved from the dynamic linker. 2182 */ 2183 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2184 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 2185 if (symp != NULL && is_exported(symp)) { 2186 def = symp; 2187 defobj = &obj_rtld; 2188 } 2189 } 2190 2191 if (def != NULL) 2192 *defobj_out = defobj; 2193 return def; 2194 } 2195 2196 static const Elf_Sym * 2197 symlook_list(const char *name, unsigned long hash, Objlist *objlist, 2198 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 2199 { 2200 const Elf_Sym *symp; 2201 const Elf_Sym *def; 2202 const Obj_Entry *defobj; 2203 const Objlist_Entry *elm; 2204 2205 def = NULL; 2206 defobj = NULL; 2207 STAILQ_FOREACH(elm, objlist, link) { 2208 if (donelist_check(dlp, elm->obj)) 2209 continue; 2210 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 2211 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 2212 def = symp; 2213 defobj = elm->obj; 2214 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 2215 break; 2216 } 2217 } 2218 } 2219 if (def != NULL) 2220 *defobj_out = defobj; 2221 return def; 2222 } 2223 2224 /* 2225 * Search the symbol table of a single shared object for a symbol of 2226 * the given name. Returns a pointer to the symbol, or NULL if no 2227 * definition was found. 2228 * 2229 * The symbol's hash value is passed in for efficiency reasons; that 2230 * eliminates many recomputations of the hash value. 2231 */ 2232 const Elf_Sym * 2233 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 2234 bool in_plt) 2235 { 2236 if (obj->buckets != NULL) { 2237 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 2238 2239 while (symnum != STN_UNDEF) { 2240 const Elf_Sym *symp; 2241 const char *strp; 2242 2243 if (symnum >= obj->nchains) 2244 return NULL; /* Bad object */ 2245 symp = obj->symtab + symnum; 2246 strp = obj->strtab + symp->st_name; 2247 2248 if (name[0] == strp[0] && strcmp(name, strp) == 0) 2249 return symp->st_shndx != SHN_UNDEF || 2250 (!in_plt && symp->st_value != 0 && 2251 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 2252 2253 symnum = obj->chains[symnum]; 2254 } 2255 } 2256 return NULL; 2257 } 2258 2259 static void 2260 trace_loaded_objects(Obj_Entry *obj) 2261 { 2262 char *fmt1, *fmt2, *fmt, *main_local, *list_containers; 2263 int c; 2264 2265 if ((main_local = getenv("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 2266 main_local = ""; 2267 2268 if ((fmt1 = getenv("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 2269 fmt1 = "\t%o => %p (%x)\n"; 2270 2271 if ((fmt2 = getenv("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 2272 fmt2 = "\t%o (%x)\n"; 2273 2274 list_containers = getenv("LD_TRACE_LOADED_OBJECTS_ALL"); 2275 2276 for (; obj; obj = obj->next) { 2277 Needed_Entry *needed; 2278 char *name, *path; 2279 bool is_lib; 2280 2281 if (list_containers && obj->needed != NULL) 2282 printf("%s:\n", obj->path); 2283 for (needed = obj->needed; needed; needed = needed->next) { 2284 if (needed->obj != NULL) { 2285 if (needed->obj->traced && !list_containers) 2286 continue; 2287 needed->obj->traced = true; 2288 path = needed->obj->path; 2289 } else 2290 path = "not found"; 2291 2292 name = (char *)obj->strtab + needed->name; 2293 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 2294 2295 fmt = is_lib ? fmt1 : fmt2; 2296 while ((c = *fmt++) != '\0') { 2297 switch (c) { 2298 default: 2299 putchar(c); 2300 continue; 2301 case '\\': 2302 switch (c = *fmt) { 2303 case '\0': 2304 continue; 2305 case 'n': 2306 putchar('\n'); 2307 break; 2308 case 't': 2309 putchar('\t'); 2310 break; 2311 } 2312 break; 2313 case '%': 2314 switch (c = *fmt) { 2315 case '\0': 2316 continue; 2317 case '%': 2318 default: 2319 putchar(c); 2320 break; 2321 case 'A': 2322 printf("%s", main_local); 2323 break; 2324 case 'a': 2325 printf("%s", obj_main->path); 2326 break; 2327 case 'o': 2328 printf("%s", name); 2329 break; 2330 #if 0 2331 case 'm': 2332 printf("%d", sodp->sod_major); 2333 break; 2334 case 'n': 2335 printf("%d", sodp->sod_minor); 2336 break; 2337 #endif 2338 case 'p': 2339 printf("%s", path); 2340 break; 2341 case 'x': 2342 printf("%p", needed->obj ? needed->obj->mapbase : 0); 2343 break; 2344 } 2345 break; 2346 } 2347 ++fmt; 2348 } 2349 } 2350 } 2351 } 2352 2353 /* 2354 * Unload a dlopened object and its dependencies from memory and from 2355 * our data structures. It is assumed that the DAG rooted in the 2356 * object has already been unreferenced, and that the object has a 2357 * reference count of 0. 2358 */ 2359 static void 2360 unload_object(Obj_Entry *root) 2361 { 2362 Obj_Entry *obj; 2363 Obj_Entry **linkp; 2364 2365 assert(root->refcount == 0); 2366 2367 /* 2368 * Pass over the DAG removing unreferenced objects from 2369 * appropriate lists. 2370 */ 2371 unlink_object(root); 2372 2373 /* Unmap all objects that are no longer referenced. */ 2374 linkp = &obj_list->next; 2375 while ((obj = *linkp) != NULL) { 2376 if (obj->refcount == 0) { 2377 dbg("unloading \"%s\"", obj->path); 2378 munmap(obj->mapbase, obj->mapsize); 2379 linkmap_delete(obj); 2380 *linkp = obj->next; 2381 obj_count--; 2382 obj_free(obj); 2383 } else 2384 linkp = &obj->next; 2385 } 2386 obj_tail = linkp; 2387 } 2388 2389 static void 2390 unlink_object(Obj_Entry *root) 2391 { 2392 const Needed_Entry *needed; 2393 Objlist_Entry *elm; 2394 2395 if (root->refcount == 0) { 2396 /* Remove the object from the RTLD_GLOBAL list. */ 2397 objlist_remove(&list_global, root); 2398 2399 /* Remove the object from all objects' DAG lists. */ 2400 STAILQ_FOREACH(elm, &root->dagmembers , link) 2401 objlist_remove(&elm->obj->dldags, root); 2402 } 2403 2404 for (needed = root->needed; needed != NULL; needed = needed->next) 2405 if (needed->obj != NULL) 2406 unlink_object(needed->obj); 2407 } 2408 2409 static void 2410 unref_dag(Obj_Entry *root) 2411 { 2412 const Needed_Entry *needed; 2413 2414 if (root->refcount == 0) 2415 return; 2416 root->refcount--; 2417 if (root->refcount == 0) 2418 for (needed = root->needed; needed != NULL; needed = needed->next) 2419 if (needed->obj != NULL) 2420 unref_dag(needed->obj); 2421 } 2422