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