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