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 #ifdef WITH_LIBMAP 56 #include "libmap.h" 57 #endif 58 59 #define END_SYM "_end" 60 #define PATH_RTLD "/usr/libexec/ld-elf.so.1" 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 const char *basename(const char *); 80 static void die(void); 81 static void digest_dynamic(Obj_Entry *, int); 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, Obj_Entry *); 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 char *ld_bind_now; /* Environment variable for immediate binding */ 139 static char *ld_debug; /* Environment variable for debugging */ 140 static char *ld_library_path; /* Environment variable for search path */ 141 static char *ld_preload; /* Environment variable for libraries to 142 load first */ 143 static char *ld_tracing; /* Called from ldd 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 *obj_main; /* The main program shared object */ 147 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 148 static unsigned int obj_count; /* Number of objects in obj_list */ 149 150 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 151 STAILQ_HEAD_INITIALIZER(list_global); 152 static Objlist list_main = /* Objects loaded at program startup */ 153 STAILQ_HEAD_INITIALIZER(list_main); 154 static Objlist list_fini = /* Objects needing fini() calls */ 155 STAILQ_HEAD_INITIALIZER(list_fini); 156 157 static LockInfo lockinfo; 158 159 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 160 161 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); 162 163 extern Elf_Dyn _DYNAMIC; 164 #pragma weak _DYNAMIC 165 166 /* 167 * These are the functions the dynamic linker exports to application 168 * programs. They are the only symbols the dynamic linker is willing 169 * to export from itself. 170 */ 171 static func_ptr_type exports[] = { 172 (func_ptr_type) &_rtld_error, 173 (func_ptr_type) &dlclose, 174 (func_ptr_type) &dlerror, 175 (func_ptr_type) &dlopen, 176 (func_ptr_type) &dlsym, 177 (func_ptr_type) &dladdr, 178 (func_ptr_type) &dllockinit, 179 (func_ptr_type) &dlinfo, 180 NULL 181 }; 182 183 /* 184 * Global declarations normally provided by crt1. The dynamic linker is 185 * not built with crt1, so we have to provide them ourselves. 186 */ 187 char *__progname; 188 char **environ; 189 190 /* 191 * Fill in a DoneList with an allocation large enough to hold all of 192 * the currently-loaded objects. Keep this as a macro since it calls 193 * alloca and we want that to occur within the scope of the caller. 194 */ 195 #define donelist_init(dlp) \ 196 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ 197 assert((dlp)->objs != NULL), \ 198 (dlp)->num_alloc = obj_count, \ 199 (dlp)->num_used = 0) 200 201 static __inline void 202 rlock_acquire(void) 203 { 204 lockinfo.rlock_acquire(lockinfo.thelock); 205 atomic_incr_int(&lockinfo.rcount); 206 lock_check(); 207 } 208 209 static __inline void 210 wlock_acquire(void) 211 { 212 lockinfo.wlock_acquire(lockinfo.thelock); 213 atomic_incr_int(&lockinfo.wcount); 214 lock_check(); 215 } 216 217 static __inline void 218 rlock_release(void) 219 { 220 atomic_decr_int(&lockinfo.rcount); 221 lockinfo.rlock_release(lockinfo.thelock); 222 } 223 224 static __inline void 225 wlock_release(void) 226 { 227 atomic_decr_int(&lockinfo.wcount); 228 lockinfo.wlock_release(lockinfo.thelock); 229 } 230 231 /* 232 * Main entry point for dynamic linking. The first argument is the 233 * stack pointer. The stack is expected to be laid out as described 234 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 235 * Specifically, the stack pointer points to a word containing 236 * ARGC. Following that in the stack is a null-terminated sequence 237 * of pointers to argument strings. Then comes a null-terminated 238 * sequence of pointers to environment strings. Finally, there is a 239 * sequence of "auxiliary vector" entries. 240 * 241 * The second argument points to a place to store the dynamic linker's 242 * exit procedure pointer and the third to a place to store the main 243 * program's object. 244 * 245 * The return value is the main program's entry point. 246 */ 247 func_ptr_type 248 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 249 { 250 Elf_Auxinfo *aux_info[AT_COUNT]; 251 int i; 252 int argc; 253 char **argv; 254 char **env; 255 Elf_Auxinfo *aux; 256 Elf_Auxinfo *auxp; 257 const char *argv0; 258 Obj_Entry *obj; 259 Obj_Entry **preload_tail; 260 Objlist initlist; 261 262 /* 263 * On entry, the dynamic linker itself has not been relocated yet. 264 * Be very careful not to reference any global data until after 265 * init_rtld has returned. It is OK to reference file-scope statics 266 * and string constants, and to call static and global functions. 267 */ 268 269 /* Find the auxiliary vector on the stack. */ 270 argc = *sp++; 271 argv = (char **) sp; 272 sp += argc + 1; /* Skip over arguments and NULL terminator */ 273 env = (char **) sp; 274 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 275 ; 276 aux = (Elf_Auxinfo *) sp; 277 278 /* Digest the auxiliary vector. */ 279 for (i = 0; i < AT_COUNT; i++) 280 aux_info[i] = NULL; 281 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 282 if (auxp->a_type < AT_COUNT) 283 aux_info[auxp->a_type] = auxp; 284 } 285 286 /* Initialize and relocate ourselves. */ 287 assert(aux_info[AT_BASE] != NULL); 288 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 289 290 __progname = obj_rtld.path; 291 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 292 environ = env; 293 294 trust = geteuid() == getuid() && getegid() == getgid(); 295 296 ld_bind_now = getenv("LD_BIND_NOW"); 297 if (trust) { 298 ld_debug = getenv("LD_DEBUG"); 299 ld_library_path = getenv("LD_LIBRARY_PATH"); 300 ld_preload = getenv("LD_PRELOAD"); 301 } 302 ld_tracing = getenv("LD_TRACE_LOADED_OBJECTS"); 303 304 if (ld_debug != NULL && *ld_debug != '\0') 305 debug = 1; 306 dbg("%s is initialized, base address = %p", __progname, 307 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 308 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 309 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 310 311 /* 312 * Load the main program, or process its program header if it is 313 * already loaded. 314 */ 315 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 316 int fd = aux_info[AT_EXECFD]->a_un.a_val; 317 dbg("loading main program"); 318 obj_main = map_object(fd, argv0, NULL); 319 close(fd); 320 if (obj_main == NULL) 321 die(); 322 } else { /* Main program already loaded. */ 323 const Elf_Phdr *phdr; 324 int phnum; 325 caddr_t entry; 326 327 dbg("processing main program's program header"); 328 assert(aux_info[AT_PHDR] != NULL); 329 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 330 assert(aux_info[AT_PHNUM] != NULL); 331 phnum = aux_info[AT_PHNUM]->a_un.a_val; 332 assert(aux_info[AT_PHENT] != NULL); 333 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 334 assert(aux_info[AT_ENTRY] != NULL); 335 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 336 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 337 die(); 338 } 339 340 obj_main->path = xstrdup(argv0); 341 obj_main->mainprog = true; 342 343 /* 344 * Get the actual dynamic linker pathname from the executable if 345 * possible. (It should always be possible.) That ensures that 346 * gdb will find the right dynamic linker even if a non-standard 347 * one is being used. 348 */ 349 if (obj_main->interp != NULL && 350 strcmp(obj_main->interp, obj_rtld.path) != 0) { 351 free(obj_rtld.path); 352 obj_rtld.path = xstrdup(obj_main->interp); 353 } 354 355 digest_dynamic(obj_main, 0); 356 357 linkmap_add(obj_main); 358 linkmap_add(&obj_rtld); 359 360 /* Link the main program into the list of objects. */ 361 *obj_tail = obj_main; 362 obj_tail = &obj_main->next; 363 obj_count++; 364 obj_main->refcount++; 365 /* Make sure we don't call the main program's init and fini functions. */ 366 obj_main->init = obj_main->fini = NULL; 367 368 /* Initialize a fake symbol for resolving undefined weak references. */ 369 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 370 sym_zero.st_shndx = SHN_UNDEF; 371 372 #ifdef WITH_LIBMAP 373 lm_init(); 374 #endif 375 376 dbg("loading LD_PRELOAD libraries"); 377 if (load_preload_objects() == -1) 378 die(); 379 preload_tail = obj_tail; 380 381 dbg("loading needed objects"); 382 if (load_needed_objects(obj_main) == -1) 383 die(); 384 385 /* Make a list of all objects loaded at startup. */ 386 for (obj = obj_list; obj != NULL; obj = obj->next) 387 objlist_push_tail(&list_main, obj); 388 389 if (ld_tracing) { /* We're done */ 390 trace_loaded_objects(obj_main); 391 exit(0); 392 } 393 394 if (relocate_objects(obj_main, 395 ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1) 396 die(); 397 398 dbg("doing copy relocations"); 399 if (do_copy_relocations(obj_main) == -1) 400 die(); 401 402 dbg("initializing key program variables"); 403 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 404 set_program_var("environ", env); 405 406 dbg("initializing thread locks"); 407 lockdflt_init(&lockinfo); 408 lockinfo.thelock = lockinfo.lock_create(lockinfo.context); 409 410 /* Make a list of init functions to call. */ 411 objlist_init(&initlist); 412 initlist_add_objects(obj_list, preload_tail, &initlist); 413 414 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ 415 416 objlist_call_init(&initlist); 417 wlock_acquire(); 418 objlist_clear(&initlist); 419 wlock_release(); 420 421 dbg("transferring control to program entry point = %p", obj_main->entry); 422 423 /* Return the exit procedure and the program entry point. */ 424 *exit_proc = rtld_exit; 425 *objp = obj_main; 426 return (func_ptr_type) obj_main->entry; 427 } 428 429 Elf_Addr 430 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 431 { 432 const Elf_Rel *rel; 433 const Elf_Sym *def; 434 const Obj_Entry *defobj; 435 Elf_Addr *where; 436 Elf_Addr target; 437 438 rlock_acquire(); 439 if (obj->pltrel) 440 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 441 else 442 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 443 444 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 445 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 446 if (def == NULL) 447 die(); 448 449 target = (Elf_Addr)(defobj->relocbase + def->st_value); 450 451 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 452 defobj->strtab + def->st_name, basename(obj->path), 453 (void *)target, basename(defobj->path)); 454 455 /* 456 * Write the new contents for the jmpslot. Note that depending on 457 * architecture, the value which we need to return back to the 458 * lazy binding trampoline may or may not be the target 459 * address. The value returned from reloc_jmpslot() is the value 460 * that the trampoline needs. 461 */ 462 target = reloc_jmpslot(where, target, defobj, obj, rel); 463 rlock_release(); 464 return target; 465 } 466 467 /* 468 * Error reporting function. Use it like printf. If formats the message 469 * into a buffer, and sets things up so that the next call to dlerror() 470 * will return the message. 471 */ 472 void 473 _rtld_error(const char *fmt, ...) 474 { 475 static char buf[512]; 476 va_list ap; 477 478 va_start(ap, fmt); 479 vsnprintf(buf, sizeof buf, fmt, ap); 480 error_message = buf; 481 va_end(ap); 482 } 483 484 /* 485 * Return a dynamically-allocated copy of the current error message, if any. 486 */ 487 static char * 488 errmsg_save(void) 489 { 490 return error_message == NULL ? NULL : xstrdup(error_message); 491 } 492 493 /* 494 * Restore the current error message from a copy which was previously saved 495 * by errmsg_save(). The copy is freed. 496 */ 497 static void 498 errmsg_restore(char *saved_msg) 499 { 500 if (saved_msg == NULL) 501 error_message = NULL; 502 else { 503 _rtld_error("%s", saved_msg); 504 free(saved_msg); 505 } 506 } 507 508 static const char * 509 basename(const char *name) 510 { 511 const char *p = strrchr(name, '/'); 512 return p != NULL ? p + 1 : name; 513 } 514 515 static void 516 die(void) 517 { 518 const char *msg = dlerror(); 519 520 if (msg == NULL) 521 msg = "Fatal error"; 522 errx(1, "%s", msg); 523 } 524 525 /* 526 * Process a shared object's DYNAMIC section, and save the important 527 * information in its Obj_Entry structure. 528 */ 529 static void 530 digest_dynamic(Obj_Entry *obj, int early) 531 { 532 const Elf_Dyn *dynp; 533 Needed_Entry **needed_tail = &obj->needed; 534 const Elf_Dyn *dyn_rpath = NULL; 535 int plttype = DT_REL; 536 537 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 538 switch (dynp->d_tag) { 539 540 case DT_REL: 541 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 542 break; 543 544 case DT_RELSZ: 545 obj->relsize = dynp->d_un.d_val; 546 break; 547 548 case DT_RELENT: 549 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 550 break; 551 552 case DT_JMPREL: 553 obj->pltrel = (const Elf_Rel *) 554 (obj->relocbase + dynp->d_un.d_ptr); 555 break; 556 557 case DT_PLTRELSZ: 558 obj->pltrelsize = dynp->d_un.d_val; 559 break; 560 561 case DT_RELA: 562 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 563 break; 564 565 case DT_RELASZ: 566 obj->relasize = dynp->d_un.d_val; 567 break; 568 569 case DT_RELAENT: 570 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 571 break; 572 573 case DT_PLTREL: 574 plttype = dynp->d_un.d_val; 575 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 576 break; 577 578 case DT_SYMTAB: 579 obj->symtab = (const Elf_Sym *) 580 (obj->relocbase + dynp->d_un.d_ptr); 581 break; 582 583 case DT_SYMENT: 584 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 585 break; 586 587 case DT_STRTAB: 588 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 589 break; 590 591 case DT_STRSZ: 592 obj->strsize = dynp->d_un.d_val; 593 break; 594 595 case DT_HASH: 596 { 597 const Elf_Hashelt *hashtab = (const Elf_Hashelt *) 598 (obj->relocbase + dynp->d_un.d_ptr); 599 obj->nbuckets = hashtab[0]; 600 obj->nchains = hashtab[1]; 601 obj->buckets = hashtab + 2; 602 obj->chains = obj->buckets + obj->nbuckets; 603 } 604 break; 605 606 case DT_NEEDED: 607 if (!obj->rtld) { 608 Needed_Entry *nep = NEW(Needed_Entry); 609 nep->name = dynp->d_un.d_val; 610 nep->obj = NULL; 611 nep->next = NULL; 612 613 *needed_tail = nep; 614 needed_tail = &nep->next; 615 } 616 break; 617 618 case DT_PLTGOT: 619 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 620 break; 621 622 case DT_TEXTREL: 623 obj->textrel = true; 624 break; 625 626 case DT_SYMBOLIC: 627 obj->symbolic = true; 628 break; 629 630 case DT_RPATH: 631 /* 632 * We have to wait until later to process this, because we 633 * might not have gotten the address of the string table yet. 634 */ 635 dyn_rpath = dynp; 636 break; 637 638 case DT_SONAME: 639 /* Not used by the dynamic linker. */ 640 break; 641 642 case DT_INIT: 643 obj->init = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr); 644 break; 645 646 case DT_FINI: 647 obj->fini = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr); 648 break; 649 650 case DT_DEBUG: 651 /* XXX - not implemented yet */ 652 if (!early) 653 dbg("Filling in DT_DEBUG entry"); 654 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 655 break; 656 657 default: 658 if (!early) { 659 dbg("Ignoring d_tag %ld = %#lx", (long)dynp->d_tag, 660 (long)dynp->d_tag); 661 } 662 break; 663 } 664 } 665 666 obj->traced = false; 667 668 if (plttype == DT_RELA) { 669 obj->pltrela = (const Elf_Rela *) obj->pltrel; 670 obj->pltrel = NULL; 671 obj->pltrelasize = obj->pltrelsize; 672 obj->pltrelsize = 0; 673 } 674 675 if (dyn_rpath != NULL) 676 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 677 } 678 679 /* 680 * Process a shared object's program header. This is used only for the 681 * main program, when the kernel has already loaded the main program 682 * into memory before calling the dynamic linker. It creates and 683 * returns an Obj_Entry structure. 684 */ 685 static Obj_Entry * 686 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 687 { 688 Obj_Entry *obj; 689 const Elf_Phdr *phlimit = phdr + phnum; 690 const Elf_Phdr *ph; 691 int nsegs = 0; 692 693 obj = obj_new(); 694 for (ph = phdr; ph < phlimit; ph++) { 695 switch (ph->p_type) { 696 697 case PT_PHDR: 698 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 699 _rtld_error("%s: invalid PT_PHDR", path); 700 return NULL; 701 } 702 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 703 obj->phsize = ph->p_memsz; 704 break; 705 706 case PT_INTERP: 707 obj->interp = (const char *) ph->p_vaddr; 708 break; 709 710 case PT_LOAD: 711 if (nsegs == 0) { /* First load segment */ 712 obj->vaddrbase = trunc_page(ph->p_vaddr); 713 obj->mapbase = (caddr_t) obj->vaddrbase; 714 obj->relocbase = obj->mapbase - obj->vaddrbase; 715 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 716 obj->vaddrbase; 717 } else { /* Last load segment */ 718 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 719 obj->vaddrbase; 720 } 721 nsegs++; 722 break; 723 724 case PT_DYNAMIC: 725 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 726 break; 727 } 728 } 729 if (nsegs < 1) { 730 _rtld_error("%s: too few PT_LOAD segments", path); 731 return NULL; 732 } 733 734 obj->entry = entry; 735 return obj; 736 } 737 738 static Obj_Entry * 739 dlcheck(void *handle) 740 { 741 Obj_Entry *obj; 742 743 for (obj = obj_list; obj != NULL; obj = obj->next) 744 if (obj == (Obj_Entry *) handle) 745 break; 746 747 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { 748 _rtld_error("Invalid shared object handle %p", handle); 749 return NULL; 750 } 751 return obj; 752 } 753 754 /* 755 * If the given object is already in the donelist, return true. Otherwise 756 * add the object to the list and return false. 757 */ 758 static bool 759 donelist_check(DoneList *dlp, const Obj_Entry *obj) 760 { 761 unsigned int i; 762 763 for (i = 0; i < dlp->num_used; i++) 764 if (dlp->objs[i] == obj) 765 return true; 766 /* 767 * Our donelist allocation should always be sufficient. But if 768 * our threads locking isn't working properly, more shared objects 769 * could have been loaded since we allocated the list. That should 770 * never happen, but we'll handle it properly just in case it does. 771 */ 772 if (dlp->num_used < dlp->num_alloc) 773 dlp->objs[dlp->num_used++] = obj; 774 return false; 775 } 776 777 /* 778 * Hash function for symbol table lookup. Don't even think about changing 779 * this. It is specified by the System V ABI. 780 */ 781 unsigned long 782 elf_hash(const char *name) 783 { 784 const unsigned char *p = (const unsigned char *) name; 785 unsigned long h = 0; 786 unsigned long g; 787 788 while (*p != '\0') { 789 h = (h << 4) + *p++; 790 if ((g = h & 0xf0000000) != 0) 791 h ^= g >> 24; 792 h &= ~g; 793 } 794 return h; 795 } 796 797 /* 798 * Find the library with the given name, and return its full pathname. 799 * The returned string is dynamically allocated. Generates an error 800 * message and returns NULL if the library cannot be found. 801 * 802 * If the second argument is non-NULL, then it refers to an already- 803 * loaded shared object, whose library search path will be searched. 804 * 805 * The search order is: 806 * rpath in the referencing file 807 * LD_LIBRARY_PATH 808 * ldconfig hints 809 * /usr/lib 810 */ 811 static char * 812 find_library(const char *xname, const Obj_Entry *refobj) 813 { 814 char *pathname; 815 char *name; 816 817 if (strchr(xname, '/') != NULL) { /* Hard coded pathname */ 818 if (xname[0] != '/' && !trust) { 819 _rtld_error("Absolute pathname required for shared object \"%s\"", 820 xname); 821 return NULL; 822 } 823 return xstrdup(xname); 824 } 825 826 #ifdef WITH_LIBMAP 827 if ((name = lm_find(refobj->path, xname)) == NULL) 828 #endif 829 name = (char *)xname; 830 831 dbg(" Searching for \"%s\"", name); 832 833 if ((pathname = search_library_path(name, ld_library_path)) != NULL || 834 (refobj != NULL && 835 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 836 (pathname = search_library_path(name, gethints())) != NULL || 837 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 838 return pathname; 839 840 _rtld_error("Shared object \"%s\" not found", name); 841 return NULL; 842 } 843 844 /* 845 * Given a symbol number in a referencing object, find the corresponding 846 * definition of the symbol. Returns a pointer to the symbol, or NULL if 847 * no definition was found. Returns a pointer to the Obj_Entry of the 848 * defining object via the reference parameter DEFOBJ_OUT. 849 */ 850 const Elf_Sym * 851 find_symdef(unsigned long symnum, const Obj_Entry *refobj, 852 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) 853 { 854 const Elf_Sym *ref; 855 const Elf_Sym *def; 856 const Obj_Entry *defobj; 857 const char *name; 858 unsigned long hash; 859 860 /* 861 * If we have already found this symbol, get the information from 862 * the cache. 863 */ 864 if (symnum >= refobj->nchains) 865 return NULL; /* Bad object */ 866 if (cache != NULL && cache[symnum].sym != NULL) { 867 *defobj_out = cache[symnum].obj; 868 return cache[symnum].sym; 869 } 870 871 ref = refobj->symtab + symnum; 872 name = refobj->strtab + ref->st_name; 873 defobj = NULL; 874 875 /* 876 * We don't have to do a full scale lookup if the symbol is local. 877 * We know it will bind to the instance in this load module; to 878 * which we already have a pointer (ie ref). By not doing a lookup, 879 * we not only improve performance, but it also avoids unresolvable 880 * symbols when local symbols are not in the hash table. This has 881 * been seen with the ia64 toolchain. 882 */ 883 if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) { 884 if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) { 885 _rtld_error("%s: Bogus symbol table entry %lu", refobj->path, 886 symnum); 887 } 888 hash = elf_hash(name); 889 def = symlook_default(name, hash, refobj, &defobj, in_plt); 890 } else { 891 def = ref; 892 defobj = refobj; 893 } 894 895 /* 896 * If we found no definition and the reference is weak, treat the 897 * symbol as having the value zero. 898 */ 899 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 900 def = &sym_zero; 901 defobj = obj_main; 902 } 903 904 if (def != NULL) { 905 *defobj_out = defobj; 906 /* Record the information in the cache to avoid subsequent lookups. */ 907 if (cache != NULL) { 908 cache[symnum].sym = def; 909 cache[symnum].obj = defobj; 910 } 911 } else { 912 if (refobj != &obj_rtld) 913 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 914 } 915 return def; 916 } 917 918 /* 919 * Return the search path from the ldconfig hints file, reading it if 920 * necessary. Returns NULL if there are problems with the hints file, 921 * or if the search path there is empty. 922 */ 923 static const char * 924 gethints(void) 925 { 926 static char *hints; 927 928 if (hints == NULL) { 929 int fd; 930 struct elfhints_hdr hdr; 931 char *p; 932 933 /* Keep from trying again in case the hints file is bad. */ 934 hints = ""; 935 936 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 937 return NULL; 938 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 939 hdr.magic != ELFHINTS_MAGIC || 940 hdr.version != 1) { 941 close(fd); 942 return NULL; 943 } 944 p = xmalloc(hdr.dirlistlen + 1); 945 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 946 read(fd, p, hdr.dirlistlen + 1) != (ssize_t)hdr.dirlistlen + 1) { 947 free(p); 948 close(fd); 949 return NULL; 950 } 951 hints = p; 952 close(fd); 953 } 954 return hints[0] != '\0' ? hints : NULL; 955 } 956 957 static void 958 init_dag(Obj_Entry *root) 959 { 960 DoneList donelist; 961 962 donelist_init(&donelist); 963 init_dag1(root, root, &donelist); 964 } 965 966 static void 967 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) 968 { 969 const Needed_Entry *needed; 970 971 if (donelist_check(dlp, obj)) 972 return; 973 objlist_push_tail(&obj->dldags, root); 974 objlist_push_tail(&root->dagmembers, obj); 975 for (needed = obj->needed; needed != NULL; needed = needed->next) 976 if (needed->obj != NULL) 977 init_dag1(root, needed->obj, dlp); 978 } 979 980 /* 981 * Initialize the dynamic linker. The argument is the address at which 982 * the dynamic linker has been mapped into memory. The primary task of 983 * this function is to relocate the dynamic linker. 984 */ 985 static void 986 init_rtld(caddr_t mapbase) 987 { 988 Obj_Entry objtmp; /* Temporary rtld object */ 989 990 /* 991 * Conjure up an Obj_Entry structure for the dynamic linker. 992 * 993 * The "path" member can't be initialized yet because string constatns 994 * cannot yet be acessed. Below we will set it correctly. 995 */ 996 objtmp.path = NULL; 997 objtmp.rtld = true; 998 objtmp.mapbase = mapbase; 999 #ifdef PIC 1000 objtmp.relocbase = mapbase; 1001 #endif 1002 if (&_DYNAMIC != 0) { 1003 objtmp.dynamic = rtld_dynamic(&objtmp); 1004 digest_dynamic(&objtmp, 1); 1005 assert(objtmp.needed == NULL); 1006 assert(!objtmp.textrel); 1007 1008 /* 1009 * Temporarily put the dynamic linker entry into the object list, so 1010 * that symbols can be found. 1011 */ 1012 1013 relocate_objects(&objtmp, true, &objtmp); 1014 } 1015 1016 /* Initialize the object list. */ 1017 obj_tail = &obj_list; 1018 1019 /* Now that non-local variables can be accesses, copy out obj_rtld. */ 1020 memcpy(&obj_rtld, &objtmp, sizeof(obj_rtld)); 1021 1022 /* Replace the path with a dynamically allocated copy. */ 1023 obj_rtld.path = xstrdup(PATH_RTLD); 1024 1025 r_debug.r_brk = r_debug_state; 1026 r_debug.r_state = RT_CONSISTENT; 1027 } 1028 1029 /* 1030 * Add the init functions from a needed object list (and its recursive 1031 * needed objects) to "list". This is not used directly; it is a helper 1032 * function for initlist_add_objects(). The write lock must be held 1033 * when this function is called. 1034 */ 1035 static void 1036 initlist_add_neededs(Needed_Entry *needed, Objlist *list) 1037 { 1038 /* Recursively process the successor needed objects. */ 1039 if (needed->next != NULL) 1040 initlist_add_neededs(needed->next, list); 1041 1042 /* Process the current needed object. */ 1043 if (needed->obj != NULL) 1044 initlist_add_objects(needed->obj, &needed->obj->next, list); 1045 } 1046 1047 /* 1048 * Scan all of the DAGs rooted in the range of objects from "obj" to 1049 * "tail" and add their init functions to "list". This recurses over 1050 * the DAGs and ensure the proper init ordering such that each object's 1051 * needed libraries are initialized before the object itself. At the 1052 * same time, this function adds the objects to the global finalization 1053 * list "list_fini" in the opposite order. The write lock must be 1054 * held when this function is called. 1055 */ 1056 static void 1057 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) 1058 { 1059 if (obj->init_done) 1060 return; 1061 obj->init_done = true; 1062 1063 /* Recursively process the successor objects. */ 1064 if (&obj->next != tail) 1065 initlist_add_objects(obj->next, tail, list); 1066 1067 /* Recursively process the needed objects. */ 1068 if (obj->needed != NULL) 1069 initlist_add_neededs(obj->needed, list); 1070 1071 /* Add the object to the init list. */ 1072 if (obj->init != NULL) 1073 objlist_push_tail(list, obj); 1074 1075 /* Add the object to the global fini list in the reverse order. */ 1076 if (obj->fini != NULL) 1077 objlist_push_head(&list_fini, obj); 1078 } 1079 1080 #ifndef FPTR_TARGET 1081 #define FPTR_TARGET(f) ((Elf_Addr) (f)) 1082 #endif 1083 1084 static bool 1085 is_exported(const Elf_Sym *def) 1086 { 1087 Elf_Addr value; 1088 const func_ptr_type *p; 1089 1090 value = (Elf_Addr)(obj_rtld.relocbase + def->st_value); 1091 for (p = exports; *p != NULL; p++) 1092 if (FPTR_TARGET(*p) == value) 1093 return true; 1094 return false; 1095 } 1096 1097 /* 1098 * Given a shared object, traverse its list of needed objects, and load 1099 * each of them. Returns 0 on success. Generates an error message and 1100 * returns -1 on failure. 1101 */ 1102 static int 1103 load_needed_objects(Obj_Entry *first) 1104 { 1105 Obj_Entry *obj; 1106 1107 for (obj = first; obj != NULL; obj = obj->next) { 1108 Needed_Entry *needed; 1109 1110 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1111 const char *name = obj->strtab + needed->name; 1112 char *path = find_library(name, obj); 1113 1114 needed->obj = NULL; 1115 if (path == NULL && !ld_tracing) 1116 return -1; 1117 1118 if (path) { 1119 needed->obj = load_object(path); 1120 if (needed->obj == NULL && !ld_tracing) 1121 return -1; /* XXX - cleanup */ 1122 } 1123 } 1124 } 1125 1126 return 0; 1127 } 1128 1129 static int 1130 load_preload_objects(void) 1131 { 1132 char *p = ld_preload; 1133 static const char delim[] = " \t:;"; 1134 1135 if (p == NULL) 1136 return NULL; 1137 1138 p += strspn(p, delim); 1139 while (*p != '\0') { 1140 size_t len = strcspn(p, delim); 1141 char *path; 1142 char savech; 1143 1144 savech = p[len]; 1145 p[len] = '\0'; 1146 if ((path = find_library(p, NULL)) == NULL) 1147 return -1; 1148 if (load_object(path) == NULL) 1149 return -1; /* XXX - cleanup */ 1150 p[len] = savech; 1151 p += len; 1152 p += strspn(p, delim); 1153 } 1154 return 0; 1155 } 1156 1157 /* 1158 * Load a shared object into memory, if it is not already loaded. The 1159 * argument must be a string allocated on the heap. This function assumes 1160 * responsibility for freeing it when necessary. 1161 * 1162 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1163 * on failure. 1164 */ 1165 static Obj_Entry * 1166 load_object(char *path) 1167 { 1168 Obj_Entry *obj; 1169 int fd = -1; 1170 struct stat sb; 1171 1172 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1173 if (strcmp(obj->path, path) == 0) 1174 break; 1175 1176 /* 1177 * If we didn't find a match by pathname, open the file and check 1178 * again by device and inode. This avoids false mismatches caused 1179 * by multiple links or ".." in pathnames. 1180 * 1181 * To avoid a race, we open the file and use fstat() rather than 1182 * using stat(). 1183 */ 1184 if (obj == NULL) { 1185 if ((fd = open(path, O_RDONLY)) == -1) { 1186 _rtld_error("Cannot open \"%s\"", path); 1187 return NULL; 1188 } 1189 if (fstat(fd, &sb) == -1) { 1190 _rtld_error("Cannot fstat \"%s\"", path); 1191 close(fd); 1192 return NULL; 1193 } 1194 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1195 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) { 1196 close(fd); 1197 break; 1198 } 1199 } 1200 } 1201 1202 if (obj == NULL) { /* First use of this object, so we must map it in */ 1203 dbg("loading \"%s\"", path); 1204 obj = map_object(fd, path, &sb); 1205 close(fd); 1206 if (obj == NULL) { 1207 free(path); 1208 return NULL; 1209 } 1210 1211 obj->path = path; 1212 digest_dynamic(obj, 0); 1213 1214 *obj_tail = obj; 1215 obj_tail = &obj->next; 1216 obj_count++; 1217 linkmap_add(obj); /* for GDB & dlinfo() */ 1218 1219 dbg(" %p .. %p: %s", obj->mapbase, 1220 obj->mapbase + obj->mapsize - 1, obj->path); 1221 if (obj->textrel) 1222 dbg(" WARNING: %s has impure text", obj->path); 1223 } else 1224 free(path); 1225 1226 obj->refcount++; 1227 return obj; 1228 } 1229 1230 /* 1231 * Check for locking violations and die if one is found. 1232 */ 1233 static void 1234 lock_check(void) 1235 { 1236 int rcount, wcount; 1237 1238 rcount = lockinfo.rcount; 1239 wcount = lockinfo.wcount; 1240 assert(rcount >= 0); 1241 assert(wcount >= 0); 1242 if (wcount > 1 || (wcount != 0 && rcount != 0)) { 1243 _rtld_error("Application locking error: %d readers and %d writers" 1244 " in dynamic linker. See DLLOCKINIT(3) in manual pages.", 1245 rcount, wcount); 1246 die(); 1247 } 1248 } 1249 1250 static Obj_Entry * 1251 obj_from_addr(const void *addr) 1252 { 1253 unsigned long endhash; 1254 Obj_Entry *obj; 1255 1256 endhash = elf_hash(END_SYM); 1257 for (obj = obj_list; obj != NULL; obj = obj->next) { 1258 const Elf_Sym *endsym; 1259 1260 if (addr < (void *) obj->mapbase) 1261 continue; 1262 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL) 1263 continue; /* No "end" symbol?! */ 1264 if (addr < (void *) (obj->relocbase + endsym->st_value)) 1265 return obj; 1266 } 1267 return NULL; 1268 } 1269 1270 /* 1271 * Call the finalization functions for each of the objects in "list" 1272 * which are unreferenced. All of the objects are expected to have 1273 * non-NULL fini functions. 1274 */ 1275 static void 1276 objlist_call_fini(Objlist *list) 1277 { 1278 Objlist_Entry *elm; 1279 char *saved_msg; 1280 1281 /* 1282 * Preserve the current error message since a fini function might 1283 * call into the dynamic linker and overwrite it. 1284 */ 1285 saved_msg = errmsg_save(); 1286 STAILQ_FOREACH(elm, list, link) { 1287 if (elm->obj->refcount == 0) { 1288 dbg("calling fini function for %s at %p", elm->obj->path, 1289 (void *)elm->obj->fini); 1290 call_initfini_pointer(elm->obj, elm->obj->fini); 1291 } 1292 } 1293 errmsg_restore(saved_msg); 1294 } 1295 1296 /* 1297 * Call the initialization functions for each of the objects in 1298 * "list". All of the objects are expected to have non-NULL init 1299 * functions. 1300 */ 1301 static void 1302 objlist_call_init(Objlist *list) 1303 { 1304 Objlist_Entry *elm; 1305 char *saved_msg; 1306 1307 /* 1308 * Preserve the current error message since an init function might 1309 * call into the dynamic linker and overwrite it. 1310 */ 1311 saved_msg = errmsg_save(); 1312 STAILQ_FOREACH(elm, list, link) { 1313 dbg("calling init function for %s at %p", elm->obj->path, 1314 (void *)elm->obj->init); 1315 call_initfini_pointer(elm->obj, elm->obj->init); 1316 } 1317 errmsg_restore(saved_msg); 1318 } 1319 1320 static void 1321 objlist_clear(Objlist *list) 1322 { 1323 Objlist_Entry *elm; 1324 1325 while (!STAILQ_EMPTY(list)) { 1326 elm = STAILQ_FIRST(list); 1327 STAILQ_REMOVE_HEAD(list, link); 1328 free(elm); 1329 } 1330 } 1331 1332 static Objlist_Entry * 1333 objlist_find(Objlist *list, const Obj_Entry *obj) 1334 { 1335 Objlist_Entry *elm; 1336 1337 STAILQ_FOREACH(elm, list, link) 1338 if (elm->obj == obj) 1339 return elm; 1340 return NULL; 1341 } 1342 1343 static void 1344 objlist_init(Objlist *list) 1345 { 1346 STAILQ_INIT(list); 1347 } 1348 1349 static void 1350 objlist_push_head(Objlist *list, Obj_Entry *obj) 1351 { 1352 Objlist_Entry *elm; 1353 1354 elm = NEW(Objlist_Entry); 1355 elm->obj = obj; 1356 STAILQ_INSERT_HEAD(list, elm, link); 1357 } 1358 1359 static void 1360 objlist_push_tail(Objlist *list, Obj_Entry *obj) 1361 { 1362 Objlist_Entry *elm; 1363 1364 elm = NEW(Objlist_Entry); 1365 elm->obj = obj; 1366 STAILQ_INSERT_TAIL(list, elm, link); 1367 } 1368 1369 static void 1370 objlist_remove(Objlist *list, Obj_Entry *obj) 1371 { 1372 Objlist_Entry *elm; 1373 1374 if ((elm = objlist_find(list, obj)) != NULL) { 1375 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1376 free(elm); 1377 } 1378 } 1379 1380 /* 1381 * Remove all of the unreferenced objects from "list". 1382 */ 1383 static void 1384 objlist_remove_unref(Objlist *list) 1385 { 1386 Objlist newlist; 1387 Objlist_Entry *elm; 1388 1389 STAILQ_INIT(&newlist); 1390 while (!STAILQ_EMPTY(list)) { 1391 elm = STAILQ_FIRST(list); 1392 STAILQ_REMOVE_HEAD(list, link); 1393 if (elm->obj->refcount == 0) 1394 free(elm); 1395 else 1396 STAILQ_INSERT_TAIL(&newlist, elm, link); 1397 } 1398 *list = newlist; 1399 } 1400 1401 /* 1402 * Relocate newly-loaded shared objects. The argument is a pointer to 1403 * the Obj_Entry for the first such object. All objects from the first 1404 * to the end of the list of objects are relocated. Returns 0 on success, 1405 * or -1 on failure. 1406 */ 1407 static int 1408 relocate_objects(Obj_Entry *first, bool bind_now, Obj_Entry *rtldobj) 1409 { 1410 Obj_Entry *obj; 1411 1412 for (obj = first; obj != NULL; obj = obj->next) { 1413 if (obj != rtldobj) 1414 dbg("relocating \"%s\"", obj->path); 1415 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1416 obj->symtab == NULL || obj->strtab == NULL) { 1417 _rtld_error("%s: Shared object has no run-time symbol table", 1418 obj->path); 1419 return -1; 1420 } 1421 1422 if (obj->textrel) { 1423 /* There are relocations to the write-protected text segment. */ 1424 if (mprotect(obj->mapbase, obj->textsize, 1425 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1426 _rtld_error("%s: Cannot write-enable text segment: %s", 1427 obj->path, strerror(errno)); 1428 return -1; 1429 } 1430 } 1431 1432 /* Process the non-PLT relocations. */ 1433 if (reloc_non_plt(obj, rtldobj)) 1434 return -1; 1435 1436 if (obj->textrel) { /* Re-protected the text segment. */ 1437 if (mprotect(obj->mapbase, obj->textsize, 1438 PROT_READ|PROT_EXEC) == -1) { 1439 _rtld_error("%s: Cannot write-protect text segment: %s", 1440 obj->path, strerror(errno)); 1441 return -1; 1442 } 1443 } 1444 1445 /* Process the PLT relocations. */ 1446 if (reloc_plt(obj) == -1) 1447 return -1; 1448 /* Relocate the jump slots if we are doing immediate binding. */ 1449 if (bind_now) 1450 if (reloc_jmpslots(obj) == -1) 1451 return -1; 1452 1453 1454 /* 1455 * Set up the magic number and version in the Obj_Entry. These 1456 * were checked in the crt1.o from the original ElfKit, so we 1457 * set them for backward compatibility. 1458 */ 1459 obj->magic = RTLD_MAGIC; 1460 obj->version = RTLD_VERSION; 1461 1462 /* Set the special PLT or GOT entries. */ 1463 init_pltgot(obj); 1464 } 1465 1466 return 0; 1467 } 1468 1469 /* 1470 * Cleanup procedure. It will be called (by the atexit mechanism) just 1471 * before the process exits. 1472 */ 1473 static void 1474 rtld_exit(void) 1475 { 1476 Obj_Entry *obj; 1477 1478 dbg("rtld_exit()"); 1479 /* Clear all the reference counts so the fini functions will be called. */ 1480 for (obj = obj_list; obj != NULL; obj = obj->next) 1481 obj->refcount = 0; 1482 objlist_call_fini(&list_fini); 1483 /* No need to remove the items from the list, since we are exiting. */ 1484 #ifdef WITH_LIBMAP 1485 lm_fini(); 1486 #endif 1487 } 1488 1489 static void * 1490 path_enumerate(const char *path, path_enum_proc callback, void *arg) 1491 { 1492 if (path == NULL) 1493 return (NULL); 1494 1495 path += strspn(path, ":;"); 1496 while (*path != '\0') { 1497 size_t len; 1498 char *res; 1499 1500 len = strcspn(path, ":;"); 1501 res = callback(path, len, arg); 1502 1503 if (res != NULL) 1504 return (res); 1505 1506 path += len; 1507 path += strspn(path, ":;"); 1508 } 1509 1510 return (NULL); 1511 } 1512 1513 struct try_library_args { 1514 const char *name; 1515 size_t namelen; 1516 char *buffer; 1517 size_t buflen; 1518 }; 1519 1520 static void * 1521 try_library_path(const char *dir, size_t dirlen, void *param) 1522 { 1523 struct try_library_args *arg; 1524 1525 arg = param; 1526 if (*dir == '/' || trust) { 1527 char *pathname; 1528 1529 if (dirlen + 1 + arg->namelen + 1 > arg->buflen) 1530 return (NULL); 1531 1532 pathname = arg->buffer; 1533 strncpy(pathname, dir, dirlen); 1534 pathname[dirlen] = '/'; 1535 strcpy(pathname + dirlen + 1, arg->name); 1536 1537 dbg(" Trying \"%s\"", pathname); 1538 if (access(pathname, F_OK) == 0) { /* We found it */ 1539 pathname = xmalloc(dirlen + 1 + arg->namelen + 1); 1540 strcpy(pathname, arg->buffer); 1541 return (pathname); 1542 } 1543 } 1544 return (NULL); 1545 } 1546 1547 static char * 1548 search_library_path(const char *name, const char *path) 1549 { 1550 char *p; 1551 struct try_library_args arg; 1552 1553 if (path == NULL) 1554 return NULL; 1555 1556 arg.name = name; 1557 arg.namelen = strlen(name); 1558 arg.buffer = xmalloc(PATH_MAX); 1559 arg.buflen = PATH_MAX; 1560 1561 p = path_enumerate(path, try_library_path, &arg); 1562 1563 free(arg.buffer); 1564 1565 return (p); 1566 } 1567 1568 int 1569 dlclose(void *handle) 1570 { 1571 Obj_Entry *root; 1572 1573 wlock_acquire(); 1574 root = dlcheck(handle); 1575 if (root == NULL) { 1576 wlock_release(); 1577 return -1; 1578 } 1579 1580 /* Unreference the object and its dependencies. */ 1581 root->dl_refcount--; 1582 unref_dag(root); 1583 1584 if (root->refcount == 0) { 1585 /* 1586 * The object is no longer referenced, so we must unload it. 1587 * First, call the fini functions with no locks held. 1588 */ 1589 wlock_release(); 1590 objlist_call_fini(&list_fini); 1591 wlock_acquire(); 1592 objlist_remove_unref(&list_fini); 1593 1594 /* Finish cleaning up the newly-unreferenced objects. */ 1595 GDB_STATE(RT_DELETE,&root->linkmap); 1596 unload_object(root); 1597 GDB_STATE(RT_CONSISTENT,NULL); 1598 } 1599 wlock_release(); 1600 return 0; 1601 } 1602 1603 const char * 1604 dlerror(void) 1605 { 1606 char *msg = error_message; 1607 error_message = NULL; 1608 return msg; 1609 } 1610 1611 /* 1612 * This function is deprecated and has no effect. 1613 */ 1614 void 1615 dllockinit(void *context, 1616 void *(*lock_create)(void *context), 1617 void (*rlock_acquire)(void *lock), 1618 void (*wlock_acquire)(void *lock), 1619 void (*lock_release)(void *lock), 1620 void (*lock_destroy)(void *lock), 1621 void (*context_destroy)(void *context)) 1622 { 1623 static void *cur_context; 1624 static void (*cur_context_destroy)(void *); 1625 1626 /* Just destroy the context from the previous call, if necessary. */ 1627 if (cur_context_destroy != NULL) 1628 cur_context_destroy(cur_context); 1629 cur_context = context; 1630 cur_context_destroy = context_destroy; 1631 } 1632 1633 void * 1634 dlopen(const char *name, int mode) 1635 { 1636 Obj_Entry **old_obj_tail; 1637 Obj_Entry *obj; 1638 Objlist initlist; 1639 int result; 1640 1641 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1"; 1642 if (ld_tracing != NULL) 1643 environ = (char **)*get_program_var_addr("environ"); 1644 1645 objlist_init(&initlist); 1646 1647 wlock_acquire(); 1648 GDB_STATE(RT_ADD,NULL); 1649 1650 old_obj_tail = obj_tail; 1651 obj = NULL; 1652 if (name == NULL) { 1653 obj = obj_main; 1654 obj->refcount++; 1655 } else { 1656 char *path = find_library(name, obj_main); 1657 if (path != NULL) 1658 obj = load_object(path); 1659 } 1660 1661 if (obj) { 1662 obj->dl_refcount++; 1663 if (mode & RTLD_GLOBAL && objlist_find(&list_global, obj) == NULL) 1664 objlist_push_tail(&list_global, obj); 1665 mode &= RTLD_MODEMASK; 1666 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1667 assert(*old_obj_tail == obj); 1668 1669 result = load_needed_objects(obj); 1670 if (result != -1 && ld_tracing) 1671 goto trace; 1672 1673 if (result == -1 || 1674 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW, 1675 &obj_rtld)) == -1) { 1676 obj->dl_refcount--; 1677 unref_dag(obj); 1678 if (obj->refcount == 0) 1679 unload_object(obj); 1680 obj = NULL; 1681 } else { 1682 /* Make list of init functions to call. */ 1683 initlist_add_objects(obj, &obj->next, &initlist); 1684 } 1685 } else if (ld_tracing) 1686 goto trace; 1687 } 1688 1689 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); 1690 1691 /* Call the init functions with no locks held. */ 1692 wlock_release(); 1693 objlist_call_init(&initlist); 1694 wlock_acquire(); 1695 objlist_clear(&initlist); 1696 wlock_release(); 1697 return obj; 1698 trace: 1699 trace_loaded_objects(obj); 1700 wlock_release(); 1701 exit(0); 1702 } 1703 1704 void * 1705 dlsym(void *handle, const char *name) 1706 { 1707 const Obj_Entry *obj; 1708 unsigned long hash; 1709 const Elf_Sym *def; 1710 const Obj_Entry *defobj; 1711 1712 hash = elf_hash(name); 1713 def = NULL; 1714 defobj = NULL; 1715 1716 rlock_acquire(); 1717 if (handle == NULL || handle == RTLD_NEXT || 1718 handle == RTLD_DEFAULT || handle == RTLD_SELF) { 1719 void *retaddr; 1720 1721 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1722 if ((obj = obj_from_addr(retaddr)) == NULL) { 1723 _rtld_error("Cannot determine caller's shared object"); 1724 rlock_release(); 1725 return NULL; 1726 } 1727 if (handle == NULL) { /* Just the caller's shared object. */ 1728 def = symlook_obj(name, hash, obj, true); 1729 defobj = obj; 1730 } else if (handle == RTLD_NEXT || /* Objects after caller's */ 1731 handle == RTLD_SELF) { /* ... caller included */ 1732 if (handle == RTLD_NEXT) 1733 obj = obj->next; 1734 for (; obj != NULL; obj = obj->next) { 1735 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1736 defobj = obj; 1737 break; 1738 } 1739 } 1740 } else { 1741 assert(handle == RTLD_DEFAULT); 1742 def = symlook_default(name, hash, obj, &defobj, true); 1743 } 1744 } else { 1745 if ((obj = dlcheck(handle)) == NULL) { 1746 rlock_release(); 1747 return NULL; 1748 } 1749 1750 if (obj->mainprog) { 1751 DoneList donelist; 1752 1753 /* Search main program and all libraries loaded by it. */ 1754 donelist_init(&donelist); 1755 def = symlook_list(name, hash, &list_main, &defobj, true, 1756 &donelist); 1757 } else { 1758 /* 1759 * XXX - This isn't correct. The search should include the whole 1760 * DAG rooted at the given object. 1761 */ 1762 def = symlook_obj(name, hash, obj, true); 1763 defobj = obj; 1764 } 1765 } 1766 1767 if (def != NULL) { 1768 rlock_release(); 1769 1770 /* 1771 * The value required by the caller is derived from the value 1772 * of the symbol. For the ia64 architecture, we need to 1773 * construct a function descriptor which the caller can use to 1774 * call the function with the right 'gp' value. For other 1775 * architectures and for non-functions, the value is simply 1776 * the relocated value of the symbol. 1777 */ 1778 if (ELF_ST_TYPE(def->st_info) == STT_FUNC) 1779 return make_function_pointer(def, defobj); 1780 else 1781 return defobj->relocbase + def->st_value; 1782 } 1783 1784 _rtld_error("Undefined symbol \"%s\"", name); 1785 rlock_release(); 1786 return NULL; 1787 } 1788 1789 int 1790 dladdr(const void *addr, Dl_info *info) 1791 { 1792 const Obj_Entry *obj; 1793 const Elf_Sym *def; 1794 void *symbol_addr; 1795 unsigned long symoffset; 1796 1797 rlock_acquire(); 1798 obj = obj_from_addr(addr); 1799 if (obj == NULL) { 1800 _rtld_error("No shared object contains address"); 1801 rlock_release(); 1802 return 0; 1803 } 1804 info->dli_fname = obj->path; 1805 info->dli_fbase = obj->mapbase; 1806 info->dli_saddr = (void *)0; 1807 info->dli_sname = NULL; 1808 1809 /* 1810 * Walk the symbol list looking for the symbol whose address is 1811 * closest to the address sent in. 1812 */ 1813 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1814 def = obj->symtab + symoffset; 1815 1816 /* 1817 * For skip the symbol if st_shndx is either SHN_UNDEF or 1818 * SHN_COMMON. 1819 */ 1820 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1821 continue; 1822 1823 /* 1824 * If the symbol is greater than the specified address, or if it 1825 * is further away from addr than the current nearest symbol, 1826 * then reject it. 1827 */ 1828 symbol_addr = obj->relocbase + def->st_value; 1829 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1830 continue; 1831 1832 /* Update our idea of the nearest symbol. */ 1833 info->dli_sname = obj->strtab + def->st_name; 1834 info->dli_saddr = symbol_addr; 1835 1836 /* Exact match? */ 1837 if (info->dli_saddr == addr) 1838 break; 1839 } 1840 rlock_release(); 1841 return 1; 1842 } 1843 1844 int 1845 dlinfo(void *handle, int request, void *p) 1846 { 1847 const Obj_Entry *obj; 1848 int error; 1849 1850 rlock_acquire(); 1851 1852 if (handle == NULL || handle == RTLD_SELF) { 1853 void *retaddr; 1854 1855 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1856 if ((obj = obj_from_addr(retaddr)) == NULL) 1857 _rtld_error("Cannot determine caller's shared object"); 1858 } else 1859 obj = dlcheck(handle); 1860 1861 if (obj == NULL) { 1862 rlock_release(); 1863 return (-1); 1864 } 1865 1866 error = 0; 1867 switch (request) { 1868 case RTLD_DI_LINKMAP: 1869 *((struct link_map const **)p) = &obj->linkmap; 1870 break; 1871 case RTLD_DI_ORIGIN: 1872 error = rtld_dirname(obj->path, p); 1873 break; 1874 1875 case RTLD_DI_SERINFOSIZE: 1876 case RTLD_DI_SERINFO: 1877 error = do_search_info(obj, request, (struct dl_serinfo *)p); 1878 break; 1879 1880 default: 1881 _rtld_error("Invalid request %d passed to dlinfo()", request); 1882 error = -1; 1883 } 1884 1885 rlock_release(); 1886 1887 return (error); 1888 } 1889 1890 struct fill_search_info_args { 1891 int request; 1892 unsigned int flags; 1893 Dl_serinfo *serinfo; 1894 Dl_serpath *serpath; 1895 char *strspace; 1896 }; 1897 1898 static void * 1899 fill_search_info(const char *dir, size_t dirlen, void *param) 1900 { 1901 struct fill_search_info_args *arg; 1902 1903 arg = param; 1904 1905 if (arg->request == RTLD_DI_SERINFOSIZE) { 1906 arg->serinfo->dls_cnt ++; 1907 arg->serinfo->dls_size += dirlen + 1; 1908 } else { 1909 struct dl_serpath *s_entry; 1910 1911 s_entry = arg->serpath; 1912 s_entry->dls_name = arg->strspace; 1913 s_entry->dls_flags = arg->flags; 1914 1915 strncpy(arg->strspace, dir, dirlen); 1916 arg->strspace[dirlen] = '\0'; 1917 1918 arg->strspace += dirlen + 1; 1919 arg->serpath++; 1920 } 1921 1922 return (NULL); 1923 } 1924 1925 static int 1926 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info) 1927 { 1928 struct dl_serinfo _info; 1929 struct fill_search_info_args args; 1930 1931 args.request = RTLD_DI_SERINFOSIZE; 1932 args.serinfo = &_info; 1933 1934 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath); 1935 _info.dls_cnt = 0; 1936 1937 path_enumerate(ld_library_path, fill_search_info, &args); 1938 path_enumerate(obj->rpath, fill_search_info, &args); 1939 path_enumerate(gethints(), fill_search_info, &args); 1940 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args); 1941 1942 1943 if (request == RTLD_DI_SERINFOSIZE) { 1944 info->dls_size = _info.dls_size; 1945 info->dls_cnt = _info.dls_cnt; 1946 return (0); 1947 } 1948 1949 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) { 1950 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()"); 1951 return (-1); 1952 } 1953 1954 args.request = RTLD_DI_SERINFO; 1955 args.serinfo = info; 1956 args.serpath = &info->dls_serpath[0]; 1957 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt]; 1958 1959 args.flags = LA_SER_LIBPATH; 1960 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL) 1961 return (-1); 1962 1963 args.flags = LA_SER_RUNPATH; 1964 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL) 1965 return (-1); 1966 1967 args.flags = LA_SER_CONFIG; 1968 if (path_enumerate(gethints(), fill_search_info, &args) != NULL) 1969 return (-1); 1970 1971 args.flags = LA_SER_DEFAULT; 1972 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL) 1973 return (-1); 1974 return (0); 1975 } 1976 1977 static int 1978 rtld_dirname(const char *path, char *bname) 1979 { 1980 const char *endp; 1981 1982 /* Empty or NULL string gets treated as "." */ 1983 if (path == NULL || *path == '\0') { 1984 bname[0] = '.'; 1985 bname[1] = '\0'; 1986 return (0); 1987 } 1988 1989 /* Strip trailing slashes */ 1990 endp = path + strlen(path) - 1; 1991 while (endp > path && *endp == '/') 1992 endp--; 1993 1994 /* Find the start of the dir */ 1995 while (endp > path && *endp != '/') 1996 endp--; 1997 1998 /* Either the dir is "/" or there are no slashes */ 1999 if (endp == path) { 2000 bname[0] = *endp == '/' ? '/' : '.'; 2001 bname[1] = '\0'; 2002 return (0); 2003 } else { 2004 do { 2005 endp--; 2006 } while (endp > path && *endp == '/'); 2007 } 2008 2009 if (endp - path + 2 > PATH_MAX) 2010 { 2011 _rtld_error("Filename is too long: %s", path); 2012 return(-1); 2013 } 2014 2015 strncpy(bname, path, endp - path + 1); 2016 bname[endp - path + 1] = '\0'; 2017 return (0); 2018 } 2019 2020 static void 2021 linkmap_add(Obj_Entry *obj) 2022 { 2023 struct link_map *l = &obj->linkmap; 2024 struct link_map *prev; 2025 2026 obj->linkmap.l_name = obj->path; 2027 obj->linkmap.l_addr = obj->mapbase; 2028 obj->linkmap.l_ld = obj->dynamic; 2029 #ifdef __mips__ 2030 /* GDB needs load offset on MIPS to use the symbols */ 2031 obj->linkmap.l_offs = obj->relocbase; 2032 #endif 2033 2034 if (r_debug.r_map == NULL) { 2035 r_debug.r_map = l; 2036 return; 2037 } 2038 2039 /* 2040 * Scan to the end of the list, but not past the entry for the 2041 * dynamic linker, which we want to keep at the very end. 2042 */ 2043 for (prev = r_debug.r_map; 2044 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 2045 prev = prev->l_next) 2046 ; 2047 2048 /* Link in the new entry. */ 2049 l->l_prev = prev; 2050 l->l_next = prev->l_next; 2051 if (l->l_next != NULL) 2052 l->l_next->l_prev = l; 2053 prev->l_next = l; 2054 } 2055 2056 static void 2057 linkmap_delete(Obj_Entry *obj) 2058 { 2059 struct link_map *l = &obj->linkmap; 2060 2061 if (l->l_prev == NULL) { 2062 if ((r_debug.r_map = l->l_next) != NULL) 2063 l->l_next->l_prev = NULL; 2064 return; 2065 } 2066 2067 if ((l->l_prev->l_next = l->l_next) != NULL) 2068 l->l_next->l_prev = l->l_prev; 2069 } 2070 2071 /* 2072 * Function for the debugger to set a breakpoint on to gain control. 2073 * 2074 * The two parameters allow the debugger to easily find and determine 2075 * what the runtime loader is doing and to whom it is doing it. 2076 * 2077 * When the loadhook trap is hit (r_debug_state, set at program 2078 * initialization), the arguments can be found on the stack: 2079 * 2080 * +8 struct link_map *m 2081 * +4 struct r_debug *rd 2082 * +0 RetAddr 2083 */ 2084 void 2085 r_debug_state(struct r_debug* rd, struct link_map *m) 2086 { 2087 } 2088 2089 /* 2090 * Get address of the pointer variable in the main program. 2091 */ 2092 static const void ** 2093 get_program_var_addr(const char *name) 2094 { 2095 const Obj_Entry *obj; 2096 unsigned long hash; 2097 2098 hash = elf_hash(name); 2099 for (obj = obj_main; obj != NULL; obj = obj->next) { 2100 const Elf_Sym *def; 2101 2102 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 2103 const void **addr; 2104 2105 addr = (const void **)(obj->relocbase + def->st_value); 2106 return addr; 2107 } 2108 } 2109 return NULL; 2110 } 2111 2112 /* 2113 * Set a pointer variable in the main program to the given value. This 2114 * is used to set key variables such as "environ" before any of the 2115 * init functions are called. 2116 */ 2117 static void 2118 set_program_var(const char *name, const void *value) 2119 { 2120 const void **addr; 2121 2122 if ((addr = get_program_var_addr(name)) != NULL) { 2123 dbg("\"%s\": *%p <-- %p", name, addr, value); 2124 *addr = value; 2125 } 2126 } 2127 2128 /* 2129 * Given a symbol name in a referencing object, find the corresponding 2130 * definition of the symbol. Returns a pointer to the symbol, or NULL if 2131 * no definition was found. Returns a pointer to the Obj_Entry of the 2132 * defining object via the reference parameter DEFOBJ_OUT. 2133 */ 2134 static const Elf_Sym * 2135 symlook_default(const char *name, unsigned long hash, 2136 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) 2137 { 2138 DoneList donelist; 2139 const Elf_Sym *def; 2140 const Elf_Sym *symp; 2141 const Obj_Entry *obj; 2142 const Obj_Entry *defobj; 2143 const Objlist_Entry *elm; 2144 def = NULL; 2145 defobj = NULL; 2146 donelist_init(&donelist); 2147 2148 /* Look first in the referencing object if linked symbolically. */ 2149 if (refobj->symbolic && !donelist_check(&donelist, refobj)) { 2150 symp = symlook_obj(name, hash, refobj, in_plt); 2151 if (symp != NULL) { 2152 def = symp; 2153 defobj = refobj; 2154 } 2155 } 2156 2157 /* Search all objects loaded at program start up. */ 2158 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2159 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); 2160 if (symp != NULL && 2161 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2162 def = symp; 2163 defobj = obj; 2164 } 2165 } 2166 2167 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */ 2168 STAILQ_FOREACH(elm, &list_global, link) { 2169 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2170 break; 2171 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2172 &donelist); 2173 if (symp != NULL && 2174 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2175 def = symp; 2176 defobj = obj; 2177 } 2178 } 2179 2180 /* Search all dlopened DAGs containing the referencing object. */ 2181 STAILQ_FOREACH(elm, &refobj->dldags, link) { 2182 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2183 break; 2184 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2185 &donelist); 2186 if (symp != NULL && 2187 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2188 def = symp; 2189 defobj = obj; 2190 } 2191 } 2192 2193 /* 2194 * Search the dynamic linker itself, and possibly resolve the 2195 * symbol from there. This is how the application links to 2196 * dynamic linker services such as dlopen. Only the values listed 2197 * in the "exports" array can be resolved from the dynamic linker. 2198 */ 2199 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2200 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 2201 if (symp != NULL && is_exported(symp)) { 2202 def = symp; 2203 defobj = &obj_rtld; 2204 } 2205 } 2206 2207 if (def != NULL) 2208 *defobj_out = defobj; 2209 return def; 2210 } 2211 2212 static const Elf_Sym * 2213 symlook_list(const char *name, unsigned long hash, Objlist *objlist, 2214 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 2215 { 2216 const Elf_Sym *symp; 2217 const Elf_Sym *def; 2218 const Obj_Entry *defobj; 2219 const Objlist_Entry *elm; 2220 2221 def = NULL; 2222 defobj = NULL; 2223 STAILQ_FOREACH(elm, objlist, link) { 2224 if (donelist_check(dlp, elm->obj)) 2225 continue; 2226 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 2227 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 2228 def = symp; 2229 defobj = elm->obj; 2230 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 2231 break; 2232 } 2233 } 2234 } 2235 if (def != NULL) 2236 *defobj_out = defobj; 2237 return def; 2238 } 2239 2240 /* 2241 * Search the symbol table of a single shared object for a symbol of 2242 * the given name. Returns a pointer to the symbol, or NULL if no 2243 * definition was found. 2244 * 2245 * The symbol's hash value is passed in for efficiency reasons; that 2246 * eliminates many recomputations of the hash value. 2247 */ 2248 const Elf_Sym * 2249 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 2250 bool in_plt) 2251 { 2252 if (obj->buckets != NULL) { 2253 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 2254 2255 while (symnum != STN_UNDEF) { 2256 const Elf_Sym *symp; 2257 const char *strp; 2258 2259 if (symnum >= obj->nchains) 2260 return NULL; /* Bad object */ 2261 symp = obj->symtab + symnum; 2262 strp = obj->strtab + symp->st_name; 2263 2264 if (name[0] == strp[0] && strcmp(name, strp) == 0) 2265 return symp->st_shndx != SHN_UNDEF || 2266 (!in_plt && symp->st_value != 0 && 2267 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 2268 2269 symnum = obj->chains[symnum]; 2270 } 2271 } 2272 return NULL; 2273 } 2274 2275 static void 2276 trace_loaded_objects(Obj_Entry *obj) 2277 { 2278 char *fmt1, *fmt2, *fmt, *main_local, *list_containers; 2279 int c; 2280 2281 if ((main_local = getenv("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 2282 main_local = ""; 2283 2284 if ((fmt1 = getenv("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 2285 fmt1 = "\t%o => %p (%x)\n"; 2286 2287 if ((fmt2 = getenv("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 2288 fmt2 = "\t%o (%x)\n"; 2289 2290 list_containers = getenv("LD_TRACE_LOADED_OBJECTS_ALL"); 2291 2292 for (; obj; obj = obj->next) { 2293 Needed_Entry *needed; 2294 char *name, *path; 2295 bool is_lib; 2296 2297 if (list_containers && obj->needed != NULL) 2298 printf("%s:\n", obj->path); 2299 for (needed = obj->needed; needed; needed = needed->next) { 2300 if (needed->obj != NULL) { 2301 if (needed->obj->traced && !list_containers) 2302 continue; 2303 needed->obj->traced = true; 2304 path = needed->obj->path; 2305 } else 2306 path = "not found"; 2307 2308 name = (char *)obj->strtab + needed->name; 2309 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 2310 2311 fmt = is_lib ? fmt1 : fmt2; 2312 while ((c = *fmt++) != '\0') { 2313 switch (c) { 2314 default: 2315 putchar(c); 2316 continue; 2317 case '\\': 2318 switch (c = *fmt) { 2319 case '\0': 2320 continue; 2321 case 'n': 2322 putchar('\n'); 2323 break; 2324 case 't': 2325 putchar('\t'); 2326 break; 2327 } 2328 break; 2329 case '%': 2330 switch (c = *fmt) { 2331 case '\0': 2332 continue; 2333 case '%': 2334 default: 2335 putchar(c); 2336 break; 2337 case 'A': 2338 printf("%s", main_local); 2339 break; 2340 case 'a': 2341 printf("%s", obj_main->path); 2342 break; 2343 case 'o': 2344 printf("%s", name); 2345 break; 2346 #if 0 2347 case 'm': 2348 printf("%d", sodp->sod_major); 2349 break; 2350 case 'n': 2351 printf("%d", sodp->sod_minor); 2352 break; 2353 #endif 2354 case 'p': 2355 printf("%s", path); 2356 break; 2357 case 'x': 2358 printf("%p", needed->obj ? needed->obj->mapbase : 0); 2359 break; 2360 } 2361 break; 2362 } 2363 ++fmt; 2364 } 2365 } 2366 } 2367 } 2368 2369 /* 2370 * Unload a dlopened object and its dependencies from memory and from 2371 * our data structures. It is assumed that the DAG rooted in the 2372 * object has already been unreferenced, and that the object has a 2373 * reference count of 0. 2374 */ 2375 static void 2376 unload_object(Obj_Entry *root) 2377 { 2378 Obj_Entry *obj; 2379 Obj_Entry **linkp; 2380 2381 assert(root->refcount == 0); 2382 2383 /* 2384 * Pass over the DAG removing unreferenced objects from 2385 * appropriate lists. 2386 */ 2387 unlink_object(root); 2388 2389 /* Unmap all objects that are no longer referenced. */ 2390 linkp = &obj_list->next; 2391 while ((obj = *linkp) != NULL) { 2392 if (obj->refcount == 0) { 2393 dbg("unloading \"%s\"", obj->path); 2394 munmap(obj->mapbase, obj->mapsize); 2395 linkmap_delete(obj); 2396 *linkp = obj->next; 2397 obj_count--; 2398 obj_free(obj); 2399 } else 2400 linkp = &obj->next; 2401 } 2402 obj_tail = linkp; 2403 } 2404 2405 static void 2406 unlink_object(Obj_Entry *root) 2407 { 2408 const Needed_Entry *needed; 2409 Objlist_Entry *elm; 2410 2411 if (root->refcount == 0) { 2412 /* Remove the object from the RTLD_GLOBAL list. */ 2413 objlist_remove(&list_global, root); 2414 2415 /* Remove the object from all objects' DAG lists. */ 2416 STAILQ_FOREACH(elm, &root->dagmembers , link) 2417 objlist_remove(&elm->obj->dldags, root); 2418 } 2419 2420 for (needed = root->needed; needed != NULL; needed = needed->next) 2421 if (needed->obj != NULL) 2422 unlink_object(needed->obj); 2423 } 2424 2425 static void 2426 unref_dag(Obj_Entry *root) 2427 { 2428 const Needed_Entry *needed; 2429 2430 if (root->refcount == 0) 2431 return; 2432 root->refcount--; 2433 if (root->refcount == 0) 2434 for (needed = root->needed; needed != NULL; needed = needed->next) 2435 if (needed->obj != NULL) 2436 unref_dag(needed->obj); 2437 } 2438