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