1 /*- 2 * Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra. 3 * Copyright 2003 Alexander Kabaev <kan@FreeBSD.ORG>. 4 * All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 * 26 * $FreeBSD$ 27 */ 28 29 /* 30 * Dynamic linker for ELF. 31 * 32 * John Polstra <jdp@polstra.com>. 33 */ 34 35 #ifndef __GNUC__ 36 #error "GCC is needed to compile this file" 37 #endif 38 39 #include <sys/param.h> 40 #include <sys/mman.h> 41 #include <sys/stat.h> 42 43 #include <dlfcn.h> 44 #include <err.h> 45 #include <errno.h> 46 #include <fcntl.h> 47 #include <stdarg.h> 48 #include <stdio.h> 49 #include <stdlib.h> 50 #include <string.h> 51 #include <unistd.h> 52 53 #include "debug.h" 54 #include "rtld.h" 55 #include "libmap.h" 56 57 #ifndef COMPAT_32BIT 58 #define PATH_RTLD "/libexec/ld-elf.so.1" 59 #else 60 #define PATH_RTLD "/libexec/ld-elf32.so.1" 61 #endif 62 63 /* Types. */ 64 typedef void (*func_ptr_type)(); 65 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg); 66 67 /* 68 * This structure provides a reentrant way to keep a list of objects and 69 * check which ones have already been processed in some way. 70 */ 71 typedef struct Struct_DoneList { 72 const Obj_Entry **objs; /* Array of object pointers */ 73 unsigned int num_alloc; /* Allocated size of the array */ 74 unsigned int num_used; /* Number of array slots used */ 75 } DoneList; 76 77 /* 78 * Function declarations. 79 */ 80 static const char *basename(const char *); 81 static void die(void); 82 static void digest_dynamic(Obj_Entry *, int); 83 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *); 84 static Obj_Entry *dlcheck(void *); 85 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *); 86 static bool donelist_check(DoneList *, const Obj_Entry *); 87 static void errmsg_restore(char *); 88 static char *errmsg_save(void); 89 static void *fill_search_info(const char *, size_t, void *); 90 static char *find_library(const char *, const Obj_Entry *); 91 static const char *gethints(void); 92 static void init_dag(Obj_Entry *); 93 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *); 94 static void init_rtld(caddr_t); 95 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list); 96 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, 97 Objlist *list); 98 static bool is_exported(const Elf_Sym *); 99 static void linkmap_add(Obj_Entry *); 100 static void linkmap_delete(Obj_Entry *); 101 static int load_needed_objects(Obj_Entry *); 102 static int load_preload_objects(void); 103 static Obj_Entry *load_object(char *); 104 static Obj_Entry *obj_from_addr(const void *); 105 static void objlist_call_fini(Objlist *); 106 static void objlist_call_init(Objlist *); 107 static void objlist_clear(Objlist *); 108 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *); 109 static void objlist_init(Objlist *); 110 static void objlist_push_head(Objlist *, Obj_Entry *); 111 static void objlist_push_tail(Objlist *, Obj_Entry *); 112 static void objlist_remove(Objlist *, Obj_Entry *); 113 static void objlist_remove_unref(Objlist *); 114 static void *path_enumerate(const char *, path_enum_proc, void *); 115 static int relocate_objects(Obj_Entry *, bool, Obj_Entry *); 116 static int rtld_dirname(const char *, char *); 117 static void rtld_exit(void); 118 static char *search_library_path(const char *, const char *); 119 static const void **get_program_var_addr(const char *name); 120 static void set_program_var(const char *, const void *); 121 static const Elf_Sym *symlook_default(const char *, unsigned long hash, 122 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt); 123 static const Elf_Sym *symlook_list(const char *, unsigned long, 124 Objlist *, const Obj_Entry **, bool in_plt, DoneList *); 125 static void trace_loaded_objects(Obj_Entry *obj); 126 static void unlink_object(Obj_Entry *); 127 static void unload_object(Obj_Entry *); 128 static void unref_dag(Obj_Entry *); 129 static void ref_dag(Obj_Entry *); 130 131 void r_debug_state(struct r_debug*, struct link_map*); 132 133 /* 134 * Data declarations. 135 */ 136 static char *error_message; /* Message for dlerror(), or NULL */ 137 struct r_debug r_debug; /* for GDB; */ 138 static bool libmap_disable; /* Disable libmap */ 139 static bool trust; /* False for setuid and setgid programs */ 140 static char *ld_bind_now; /* Environment variable for immediate binding */ 141 static char *ld_debug; /* Environment variable for debugging */ 142 static char *ld_library_path; /* Environment variable for search path */ 143 static char *ld_preload; /* Environment variable for libraries to 144 load first */ 145 static char *ld_tracing; /* Called from ldd to print libs */ 146 static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 147 static Obj_Entry **obj_tail; /* Link field of last object in list */ 148 static Obj_Entry *obj_main; /* The main program shared object */ 149 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 150 static unsigned int obj_count; /* Number of objects in obj_list */ 151 152 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 153 STAILQ_HEAD_INITIALIZER(list_global); 154 static Objlist list_main = /* Objects loaded at program startup */ 155 STAILQ_HEAD_INITIALIZER(list_main); 156 static Objlist list_fini = /* Objects needing fini() calls */ 157 STAILQ_HEAD_INITIALIZER(list_fini); 158 159 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 160 161 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); 162 163 extern Elf_Dyn _DYNAMIC; 164 #pragma weak _DYNAMIC 165 166 /* 167 * These are the functions the dynamic linker exports to application 168 * programs. They are the only symbols the dynamic linker is willing 169 * to export from itself. 170 */ 171 static func_ptr_type exports[] = { 172 (func_ptr_type) &_rtld_error, 173 (func_ptr_type) &dlclose, 174 (func_ptr_type) &dlerror, 175 (func_ptr_type) &dlopen, 176 (func_ptr_type) &dlsym, 177 (func_ptr_type) &dladdr, 178 (func_ptr_type) &dllockinit, 179 (func_ptr_type) &dlinfo, 180 (func_ptr_type) &_rtld_thread_init, 181 NULL 182 }; 183 184 /* 185 * Global declarations normally provided by crt1. The dynamic linker is 186 * not built with crt1, so we have to provide them ourselves. 187 */ 188 char *__progname; 189 char **environ; 190 191 /* 192 * Fill in a DoneList with an allocation large enough to hold all of 193 * the currently-loaded objects. Keep this as a macro since it calls 194 * alloca and we want that to occur within the scope of the caller. 195 */ 196 #define donelist_init(dlp) \ 197 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ 198 assert((dlp)->objs != NULL), \ 199 (dlp)->num_alloc = obj_count, \ 200 (dlp)->num_used = 0) 201 202 /* 203 * Main entry point for dynamic linking. The first argument is the 204 * stack pointer. The stack is expected to be laid out as described 205 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 206 * Specifically, the stack pointer points to a word containing 207 * ARGC. Following that in the stack is a null-terminated sequence 208 * of pointers to argument strings. Then comes a null-terminated 209 * sequence of pointers to environment strings. Finally, there is a 210 * sequence of "auxiliary vector" entries. 211 * 212 * The second argument points to a place to store the dynamic linker's 213 * exit procedure pointer and the third to a place to store the main 214 * program's object. 215 * 216 * The return value is the main program's entry point. 217 */ 218 func_ptr_type 219 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 220 { 221 Elf_Auxinfo *aux_info[AT_COUNT]; 222 int i; 223 int argc; 224 char **argv; 225 char **env; 226 Elf_Auxinfo *aux; 227 Elf_Auxinfo *auxp; 228 const char *argv0; 229 Obj_Entry *obj; 230 Obj_Entry **preload_tail; 231 Objlist initlist; 232 int lockstate; 233 234 /* 235 * On entry, the dynamic linker itself has not been relocated yet. 236 * Be very careful not to reference any global data until after 237 * init_rtld has returned. It is OK to reference file-scope statics 238 * and string constants, and to call static and global functions. 239 */ 240 241 /* Find the auxiliary vector on the stack. */ 242 argc = *sp++; 243 argv = (char **) sp; 244 sp += argc + 1; /* Skip over arguments and NULL terminator */ 245 env = (char **) sp; 246 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 247 ; 248 aux = (Elf_Auxinfo *) sp; 249 250 /* Digest the auxiliary vector. */ 251 for (i = 0; i < AT_COUNT; i++) 252 aux_info[i] = NULL; 253 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 254 if (auxp->a_type < AT_COUNT) 255 aux_info[auxp->a_type] = auxp; 256 } 257 258 /* Initialize and relocate ourselves. */ 259 assert(aux_info[AT_BASE] != NULL); 260 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 261 262 __progname = obj_rtld.path; 263 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 264 environ = env; 265 266 trust = !issetugid(); 267 268 ld_bind_now = getenv(LD_ "BIND_NOW"); 269 if (trust) { 270 ld_debug = getenv(LD_ "DEBUG"); 271 libmap_disable = getenv(LD_ "LIBMAP_DISABLE") != NULL; 272 ld_library_path = getenv(LD_ "LIBRARY_PATH"); 273 ld_preload = getenv(LD_ "PRELOAD"); 274 } 275 ld_tracing = getenv(LD_ "TRACE_LOADED_OBJECTS"); 276 277 if (ld_debug != NULL && *ld_debug != '\0') 278 debug = 1; 279 dbg("%s is initialized, base address = %p", __progname, 280 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 281 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 282 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 283 284 /* 285 * Load the main program, or process its program header if it is 286 * already loaded. 287 */ 288 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 289 int fd = aux_info[AT_EXECFD]->a_un.a_val; 290 dbg("loading main program"); 291 obj_main = map_object(fd, argv0, NULL); 292 close(fd); 293 if (obj_main == NULL) 294 die(); 295 } else { /* Main program already loaded. */ 296 const Elf_Phdr *phdr; 297 int phnum; 298 caddr_t entry; 299 300 dbg("processing main program's program header"); 301 assert(aux_info[AT_PHDR] != NULL); 302 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 303 assert(aux_info[AT_PHNUM] != NULL); 304 phnum = aux_info[AT_PHNUM]->a_un.a_val; 305 assert(aux_info[AT_PHENT] != NULL); 306 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 307 assert(aux_info[AT_ENTRY] != NULL); 308 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 309 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 310 die(); 311 } 312 313 obj_main->path = xstrdup(argv0); 314 obj_main->mainprog = true; 315 316 /* 317 * Get the actual dynamic linker pathname from the executable if 318 * possible. (It should always be possible.) That ensures that 319 * gdb will find the right dynamic linker even if a non-standard 320 * one is being used. 321 */ 322 if (obj_main->interp != NULL && 323 strcmp(obj_main->interp, obj_rtld.path) != 0) { 324 free(obj_rtld.path); 325 obj_rtld.path = xstrdup(obj_main->interp); 326 __progname = obj_rtld.path; 327 } 328 329 digest_dynamic(obj_main, 0); 330 331 linkmap_add(obj_main); 332 linkmap_add(&obj_rtld); 333 334 /* Link the main program into the list of objects. */ 335 *obj_tail = obj_main; 336 obj_tail = &obj_main->next; 337 obj_count++; 338 /* Make sure we don't call the main program's init and fini functions. */ 339 obj_main->init = obj_main->fini = (Elf_Addr)NULL; 340 341 /* Initialize a fake symbol for resolving undefined weak references. */ 342 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 343 sym_zero.st_shndx = SHN_UNDEF; 344 345 if (!libmap_disable) 346 libmap_disable = (bool)lm_init(); 347 348 dbg("loading LD_PRELOAD libraries"); 349 if (load_preload_objects() == -1) 350 die(); 351 preload_tail = obj_tail; 352 353 dbg("loading needed objects"); 354 if (load_needed_objects(obj_main) == -1) 355 die(); 356 357 /* Make a list of all objects loaded at startup. */ 358 for (obj = obj_list; obj != NULL; obj = obj->next) { 359 objlist_push_tail(&list_main, obj); 360 obj->refcount++; 361 } 362 363 if (ld_tracing) { /* We're done */ 364 trace_loaded_objects(obj_main); 365 exit(0); 366 } 367 368 if (getenv(LD_ "DUMP_REL_PRE") != NULL) { 369 dump_relocations(obj_main); 370 exit (0); 371 } 372 373 if (relocate_objects(obj_main, 374 ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1) 375 die(); 376 377 dbg("doing copy relocations"); 378 if (do_copy_relocations(obj_main) == -1) 379 die(); 380 381 if (getenv(LD_ "DUMP_REL_POST") != NULL) { 382 dump_relocations(obj_main); 383 exit (0); 384 } 385 386 dbg("initializing key program variables"); 387 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 388 set_program_var("environ", env); 389 390 dbg("initializing thread locks"); 391 lockdflt_init(); 392 393 /* Make a list of init functions to call. */ 394 objlist_init(&initlist); 395 initlist_add_objects(obj_list, preload_tail, &initlist); 396 397 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ 398 399 objlist_call_init(&initlist); 400 lockstate = wlock_acquire(rtld_bind_lock); 401 objlist_clear(&initlist); 402 wlock_release(rtld_bind_lock, lockstate); 403 404 dbg("transferring control to program entry point = %p", obj_main->entry); 405 406 /* Return the exit procedure and the program entry point. */ 407 *exit_proc = rtld_exit; 408 *objp = obj_main; 409 return (func_ptr_type) obj_main->entry; 410 } 411 412 Elf_Addr 413 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 414 { 415 const Elf_Rel *rel; 416 const Elf_Sym *def; 417 const Obj_Entry *defobj; 418 Elf_Addr *where; 419 Elf_Addr target; 420 int lockstate; 421 422 lockstate = rlock_acquire(rtld_bind_lock); 423 if (obj->pltrel) 424 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 425 else 426 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 427 428 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 429 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 430 if (def == NULL) 431 die(); 432 433 target = (Elf_Addr)(defobj->relocbase + def->st_value); 434 435 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 436 defobj->strtab + def->st_name, basename(obj->path), 437 (void *)target, basename(defobj->path)); 438 439 /* 440 * Write the new contents for the jmpslot. Note that depending on 441 * architecture, the value which we need to return back to the 442 * lazy binding trampoline may or may not be the target 443 * address. The value returned from reloc_jmpslot() is the value 444 * that the trampoline needs. 445 */ 446 target = reloc_jmpslot(where, target, defobj, obj, rel); 447 rlock_release(rtld_bind_lock, lockstate); 448 return target; 449 } 450 451 /* 452 * Error reporting function. Use it like printf. If formats the message 453 * into a buffer, and sets things up so that the next call to dlerror() 454 * will return the message. 455 */ 456 void 457 _rtld_error(const char *fmt, ...) 458 { 459 static char buf[512]; 460 va_list ap; 461 462 va_start(ap, fmt); 463 vsnprintf(buf, sizeof buf, fmt, ap); 464 error_message = buf; 465 va_end(ap); 466 } 467 468 /* 469 * Return a dynamically-allocated copy of the current error message, if any. 470 */ 471 static char * 472 errmsg_save(void) 473 { 474 return error_message == NULL ? NULL : xstrdup(error_message); 475 } 476 477 /* 478 * Restore the current error message from a copy which was previously saved 479 * by errmsg_save(). The copy is freed. 480 */ 481 static void 482 errmsg_restore(char *saved_msg) 483 { 484 if (saved_msg == NULL) 485 error_message = NULL; 486 else { 487 _rtld_error("%s", saved_msg); 488 free(saved_msg); 489 } 490 } 491 492 static const char * 493 basename(const char *name) 494 { 495 const char *p = strrchr(name, '/'); 496 return p != NULL ? p + 1 : name; 497 } 498 499 static void 500 die(void) 501 { 502 const char *msg = dlerror(); 503 504 if (msg == NULL) 505 msg = "Fatal error"; 506 errx(1, "%s", msg); 507 } 508 509 /* 510 * Process a shared object's DYNAMIC section, and save the important 511 * information in its Obj_Entry structure. 512 */ 513 static void 514 digest_dynamic(Obj_Entry *obj, int early) 515 { 516 const Elf_Dyn *dynp; 517 Needed_Entry **needed_tail = &obj->needed; 518 const Elf_Dyn *dyn_rpath = NULL; 519 int plttype = DT_REL; 520 521 obj->bind_now = false; 522 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 523 switch (dynp->d_tag) { 524 525 case DT_REL: 526 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 527 break; 528 529 case DT_RELSZ: 530 obj->relsize = dynp->d_un.d_val; 531 break; 532 533 case DT_RELENT: 534 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 535 break; 536 537 case DT_JMPREL: 538 obj->pltrel = (const Elf_Rel *) 539 (obj->relocbase + dynp->d_un.d_ptr); 540 break; 541 542 case DT_PLTRELSZ: 543 obj->pltrelsize = dynp->d_un.d_val; 544 break; 545 546 case DT_RELA: 547 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 548 break; 549 550 case DT_RELASZ: 551 obj->relasize = dynp->d_un.d_val; 552 break; 553 554 case DT_RELAENT: 555 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 556 break; 557 558 case DT_PLTREL: 559 plttype = dynp->d_un.d_val; 560 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 561 break; 562 563 case DT_SYMTAB: 564 obj->symtab = (const Elf_Sym *) 565 (obj->relocbase + dynp->d_un.d_ptr); 566 break; 567 568 case DT_SYMENT: 569 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 570 break; 571 572 case DT_STRTAB: 573 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 574 break; 575 576 case DT_STRSZ: 577 obj->strsize = dynp->d_un.d_val; 578 break; 579 580 case DT_HASH: 581 { 582 const Elf_Hashelt *hashtab = (const Elf_Hashelt *) 583 (obj->relocbase + dynp->d_un.d_ptr); 584 obj->nbuckets = hashtab[0]; 585 obj->nchains = hashtab[1]; 586 obj->buckets = hashtab + 2; 587 obj->chains = obj->buckets + obj->nbuckets; 588 } 589 break; 590 591 case DT_NEEDED: 592 if (!obj->rtld) { 593 Needed_Entry *nep = NEW(Needed_Entry); 594 nep->name = dynp->d_un.d_val; 595 nep->obj = NULL; 596 nep->next = NULL; 597 598 *needed_tail = nep; 599 needed_tail = &nep->next; 600 } 601 break; 602 603 case DT_PLTGOT: 604 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 605 break; 606 607 case DT_TEXTREL: 608 obj->textrel = true; 609 break; 610 611 case DT_SYMBOLIC: 612 obj->symbolic = true; 613 break; 614 615 case DT_RPATH: 616 case DT_RUNPATH: /* XXX: process separately */ 617 /* 618 * We have to wait until later to process this, because we 619 * might not have gotten the address of the string table yet. 620 */ 621 dyn_rpath = dynp; 622 break; 623 624 case DT_SONAME: 625 /* Not used by the dynamic linker. */ 626 break; 627 628 case DT_INIT: 629 obj->init = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr); 630 break; 631 632 case DT_FINI: 633 obj->fini = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr); 634 break; 635 636 case DT_DEBUG: 637 /* XXX - not implemented yet */ 638 if (!early) 639 dbg("Filling in DT_DEBUG entry"); 640 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 641 break; 642 643 case DT_FLAGS: 644 if (dynp->d_un.d_val & DF_ORIGIN) { 645 obj->origin_path = xmalloc(PATH_MAX); 646 if (rtld_dirname(obj->path, obj->origin_path) == -1) 647 die(); 648 } 649 if (dynp->d_un.d_val & DF_SYMBOLIC) 650 obj->symbolic = true; 651 if (dynp->d_un.d_val & DF_TEXTREL) 652 obj->textrel = true; 653 if (dynp->d_un.d_val & DF_BIND_NOW) 654 obj->bind_now = true; 655 if (dynp->d_un.d_val & DF_STATIC_TLS) 656 ; 657 break; 658 659 default: 660 if (!early) { 661 dbg("Ignoring d_tag %ld = %#lx", (long)dynp->d_tag, 662 (long)dynp->d_tag); 663 } 664 break; 665 } 666 } 667 668 obj->traced = false; 669 670 if (plttype == DT_RELA) { 671 obj->pltrela = (const Elf_Rela *) obj->pltrel; 672 obj->pltrel = NULL; 673 obj->pltrelasize = obj->pltrelsize; 674 obj->pltrelsize = 0; 675 } 676 677 if (dyn_rpath != NULL) 678 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 679 } 680 681 /* 682 * Process a shared object's program header. This is used only for the 683 * main program, when the kernel has already loaded the main program 684 * into memory before calling the dynamic linker. It creates and 685 * returns an Obj_Entry structure. 686 */ 687 static Obj_Entry * 688 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 689 { 690 Obj_Entry *obj; 691 const Elf_Phdr *phlimit = phdr + phnum; 692 const Elf_Phdr *ph; 693 int nsegs = 0; 694 695 obj = obj_new(); 696 for (ph = phdr; ph < phlimit; ph++) { 697 switch (ph->p_type) { 698 699 case PT_PHDR: 700 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 701 _rtld_error("%s: invalid PT_PHDR", path); 702 return NULL; 703 } 704 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 705 obj->phsize = ph->p_memsz; 706 break; 707 708 case PT_INTERP: 709 obj->interp = (const char *) ph->p_vaddr; 710 break; 711 712 case PT_LOAD: 713 if (nsegs == 0) { /* First load segment */ 714 obj->vaddrbase = trunc_page(ph->p_vaddr); 715 obj->mapbase = (caddr_t) obj->vaddrbase; 716 obj->relocbase = obj->mapbase - obj->vaddrbase; 717 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 718 obj->vaddrbase; 719 } else { /* Last load segment */ 720 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 721 obj->vaddrbase; 722 } 723 nsegs++; 724 break; 725 726 case PT_DYNAMIC: 727 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 728 break; 729 } 730 } 731 if (nsegs < 1) { 732 _rtld_error("%s: too few PT_LOAD segments", path); 733 return NULL; 734 } 735 736 obj->entry = entry; 737 return obj; 738 } 739 740 static Obj_Entry * 741 dlcheck(void *handle) 742 { 743 Obj_Entry *obj; 744 745 for (obj = obj_list; obj != NULL; obj = obj->next) 746 if (obj == (Obj_Entry *) handle) 747 break; 748 749 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { 750 _rtld_error("Invalid shared object handle %p", handle); 751 return NULL; 752 } 753 return obj; 754 } 755 756 /* 757 * If the given object is already in the donelist, return true. Otherwise 758 * add the object to the list and return false. 759 */ 760 static bool 761 donelist_check(DoneList *dlp, const Obj_Entry *obj) 762 { 763 unsigned int i; 764 765 for (i = 0; i < dlp->num_used; i++) 766 if (dlp->objs[i] == obj) 767 return true; 768 /* 769 * Our donelist allocation should always be sufficient. But if 770 * our threads locking isn't working properly, more shared objects 771 * could have been loaded since we allocated the list. That should 772 * never happen, but we'll handle it properly just in case it does. 773 */ 774 if (dlp->num_used < dlp->num_alloc) 775 dlp->objs[dlp->num_used++] = obj; 776 return false; 777 } 778 779 /* 780 * Hash function for symbol table lookup. Don't even think about changing 781 * this. It is specified by the System V ABI. 782 */ 783 unsigned long 784 elf_hash(const char *name) 785 { 786 const unsigned char *p = (const unsigned char *) name; 787 unsigned long h = 0; 788 unsigned long g; 789 790 while (*p != '\0') { 791 h = (h << 4) + *p++; 792 if ((g = h & 0xf0000000) != 0) 793 h ^= g >> 24; 794 h &= ~g; 795 } 796 return h; 797 } 798 799 /* 800 * Find the library with the given name, and return its full pathname. 801 * The returned string is dynamically allocated. Generates an error 802 * message and returns NULL if the library cannot be found. 803 * 804 * If the second argument is non-NULL, then it refers to an already- 805 * loaded shared object, whose library search path will be searched. 806 * 807 * The search order is: 808 * LD_LIBRARY_PATH 809 * rpath in the referencing file 810 * ldconfig hints 811 * /lib:/usr/lib 812 */ 813 static char * 814 find_library(const char *xname, const Obj_Entry *refobj) 815 { 816 char *pathname; 817 char *name; 818 819 if (strchr(xname, '/') != NULL) { /* Hard coded pathname */ 820 if (xname[0] != '/' && !trust) { 821 _rtld_error("Absolute pathname required for shared object \"%s\"", 822 xname); 823 return NULL; 824 } 825 return xstrdup(xname); 826 } 827 828 if (libmap_disable || (refobj == NULL) || 829 (name = lm_find(refobj->path, xname)) == NULL) 830 name = (char *)xname; 831 832 dbg(" Searching for \"%s\"", name); 833 834 if ((pathname = search_library_path(name, ld_library_path)) != NULL || 835 (refobj != NULL && 836 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 837 (pathname = search_library_path(name, gethints())) != NULL || 838 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 839 return pathname; 840 841 if(refobj != NULL && refobj->path != NULL) { 842 _rtld_error("Shared object \"%s\" not found, required by \"%s\"", 843 name, basename(refobj->path)); 844 } else { 845 _rtld_error("Shared object \"%s\" not found", name); 846 } 847 return NULL; 848 } 849 850 /* 851 * Given a symbol number in a referencing object, find the corresponding 852 * definition of the symbol. Returns a pointer to the symbol, or NULL if 853 * no definition was found. Returns a pointer to the Obj_Entry of the 854 * defining object via the reference parameter DEFOBJ_OUT. 855 */ 856 const Elf_Sym * 857 find_symdef(unsigned long symnum, const Obj_Entry *refobj, 858 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) 859 { 860 const Elf_Sym *ref; 861 const Elf_Sym *def; 862 const Obj_Entry *defobj; 863 const char *name; 864 unsigned long hash; 865 866 /* 867 * If we have already found this symbol, get the information from 868 * the cache. 869 */ 870 if (symnum >= refobj->nchains) 871 return NULL; /* Bad object */ 872 if (cache != NULL && cache[symnum].sym != NULL) { 873 *defobj_out = cache[symnum].obj; 874 return cache[symnum].sym; 875 } 876 877 ref = refobj->symtab + symnum; 878 name = refobj->strtab + ref->st_name; 879 defobj = NULL; 880 881 /* 882 * We don't have to do a full scale lookup if the symbol is local. 883 * We know it will bind to the instance in this load module; to 884 * which we already have a pointer (ie ref). By not doing a lookup, 885 * we not only improve performance, but it also avoids unresolvable 886 * symbols when local symbols are not in the hash table. This has 887 * been seen with the ia64 toolchain. 888 */ 889 if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) { 890 if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) { 891 _rtld_error("%s: Bogus symbol table entry %lu", refobj->path, 892 symnum); 893 } 894 hash = elf_hash(name); 895 def = symlook_default(name, hash, refobj, &defobj, in_plt); 896 } else { 897 def = ref; 898 defobj = refobj; 899 } 900 901 /* 902 * If we found no definition and the reference is weak, treat the 903 * symbol as having the value zero. 904 */ 905 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 906 def = &sym_zero; 907 defobj = obj_main; 908 } 909 910 if (def != NULL) { 911 *defobj_out = defobj; 912 /* Record the information in the cache to avoid subsequent lookups. */ 913 if (cache != NULL) { 914 cache[symnum].sym = def; 915 cache[symnum].obj = defobj; 916 } 917 } else { 918 if (refobj != &obj_rtld) 919 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 920 } 921 return def; 922 } 923 924 /* 925 * Return the search path from the ldconfig hints file, reading it if 926 * necessary. Returns NULL if there are problems with the hints file, 927 * or if the search path there is empty. 928 */ 929 static const char * 930 gethints(void) 931 { 932 static char *hints; 933 934 if (hints == NULL) { 935 int fd; 936 struct elfhints_hdr hdr; 937 char *p; 938 939 /* Keep from trying again in case the hints file is bad. */ 940 hints = ""; 941 942 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 943 return NULL; 944 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 945 hdr.magic != ELFHINTS_MAGIC || 946 hdr.version != 1) { 947 close(fd); 948 return NULL; 949 } 950 p = xmalloc(hdr.dirlistlen + 1); 951 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 952 read(fd, p, hdr.dirlistlen + 1) != (ssize_t)hdr.dirlistlen + 1) { 953 free(p); 954 close(fd); 955 return NULL; 956 } 957 hints = p; 958 close(fd); 959 } 960 return hints[0] != '\0' ? hints : NULL; 961 } 962 963 static void 964 init_dag(Obj_Entry *root) 965 { 966 DoneList donelist; 967 968 donelist_init(&donelist); 969 init_dag1(root, root, &donelist); 970 } 971 972 static void 973 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) 974 { 975 const Needed_Entry *needed; 976 977 if (donelist_check(dlp, obj)) 978 return; 979 980 obj->refcount++; 981 objlist_push_tail(&obj->dldags, root); 982 objlist_push_tail(&root->dagmembers, obj); 983 for (needed = obj->needed; needed != NULL; needed = needed->next) 984 if (needed->obj != NULL) 985 init_dag1(root, needed->obj, dlp); 986 } 987 988 /* 989 * Initialize the dynamic linker. The argument is the address at which 990 * the dynamic linker has been mapped into memory. The primary task of 991 * this function is to relocate the dynamic linker. 992 */ 993 static void 994 init_rtld(caddr_t mapbase) 995 { 996 Obj_Entry objtmp; /* Temporary rtld object */ 997 998 /* 999 * Conjure up an Obj_Entry structure for the dynamic linker. 1000 * 1001 * The "path" member can't be initialized yet because string constatns 1002 * cannot yet be acessed. Below we will set it correctly. 1003 */ 1004 memset(&objtmp, 0, sizeof(objtmp)); 1005 objtmp.path = NULL; 1006 objtmp.rtld = true; 1007 objtmp.mapbase = mapbase; 1008 #ifdef PIC 1009 objtmp.relocbase = mapbase; 1010 #endif 1011 if (&_DYNAMIC != 0) { 1012 objtmp.dynamic = rtld_dynamic(&objtmp); 1013 digest_dynamic(&objtmp, 1); 1014 assert(objtmp.needed == NULL); 1015 assert(!objtmp.textrel); 1016 1017 /* 1018 * Temporarily put the dynamic linker entry into the object list, so 1019 * that symbols can be found. 1020 */ 1021 1022 relocate_objects(&objtmp, true, &objtmp); 1023 } 1024 1025 /* Initialize the object list. */ 1026 obj_tail = &obj_list; 1027 1028 /* Now that non-local variables can be accesses, copy out obj_rtld. */ 1029 memcpy(&obj_rtld, &objtmp, sizeof(obj_rtld)); 1030 1031 /* Replace the path with a dynamically allocated copy. */ 1032 obj_rtld.path = xstrdup(PATH_RTLD); 1033 1034 r_debug.r_brk = r_debug_state; 1035 r_debug.r_state = RT_CONSISTENT; 1036 } 1037 1038 /* 1039 * Add the init functions from a needed object list (and its recursive 1040 * needed objects) to "list". This is not used directly; it is a helper 1041 * function for initlist_add_objects(). The write lock must be held 1042 * when this function is called. 1043 */ 1044 static void 1045 initlist_add_neededs(Needed_Entry *needed, Objlist *list) 1046 { 1047 /* Recursively process the successor needed objects. */ 1048 if (needed->next != NULL) 1049 initlist_add_neededs(needed->next, list); 1050 1051 /* Process the current needed object. */ 1052 if (needed->obj != NULL) 1053 initlist_add_objects(needed->obj, &needed->obj->next, list); 1054 } 1055 1056 /* 1057 * Scan all of the DAGs rooted in the range of objects from "obj" to 1058 * "tail" and add their init functions to "list". This recurses over 1059 * the DAGs and ensure the proper init ordering such that each object's 1060 * needed libraries are initialized before the object itself. At the 1061 * same time, this function adds the objects to the global finalization 1062 * list "list_fini" in the opposite order. The write lock must be 1063 * held when this function is called. 1064 */ 1065 static void 1066 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) 1067 { 1068 if (obj->init_done) 1069 return; 1070 obj->init_done = true; 1071 1072 /* Recursively process the successor objects. */ 1073 if (&obj->next != tail) 1074 initlist_add_objects(obj->next, tail, list); 1075 1076 /* Recursively process the needed objects. */ 1077 if (obj->needed != NULL) 1078 initlist_add_neededs(obj->needed, list); 1079 1080 /* Add the object to the init list. */ 1081 if (obj->init != (Elf_Addr)NULL) 1082 objlist_push_tail(list, obj); 1083 1084 /* Add the object to the global fini list in the reverse order. */ 1085 if (obj->fini != (Elf_Addr)NULL) 1086 objlist_push_head(&list_fini, obj); 1087 } 1088 1089 #ifndef FPTR_TARGET 1090 #define FPTR_TARGET(f) ((Elf_Addr) (f)) 1091 #endif 1092 1093 static bool 1094 is_exported(const Elf_Sym *def) 1095 { 1096 Elf_Addr value; 1097 const func_ptr_type *p; 1098 1099 value = (Elf_Addr)(obj_rtld.relocbase + def->st_value); 1100 for (p = exports; *p != NULL; p++) 1101 if (FPTR_TARGET(*p) == value) 1102 return true; 1103 return false; 1104 } 1105 1106 /* 1107 * Given a shared object, traverse its list of needed objects, and load 1108 * each of them. Returns 0 on success. Generates an error message and 1109 * returns -1 on failure. 1110 */ 1111 static int 1112 load_needed_objects(Obj_Entry *first) 1113 { 1114 Obj_Entry *obj; 1115 1116 for (obj = first; obj != NULL; obj = obj->next) { 1117 Needed_Entry *needed; 1118 1119 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1120 const char *name = obj->strtab + needed->name; 1121 char *path = find_library(name, obj); 1122 1123 needed->obj = NULL; 1124 if (path == NULL && !ld_tracing) 1125 return -1; 1126 1127 if (path) { 1128 needed->obj = load_object(path); 1129 if (needed->obj == NULL && !ld_tracing) 1130 return -1; /* XXX - cleanup */ 1131 } 1132 } 1133 } 1134 1135 return 0; 1136 } 1137 1138 static int 1139 load_preload_objects(void) 1140 { 1141 char *p = ld_preload; 1142 static const char delim[] = " \t:;"; 1143 1144 if (p == NULL) 1145 return 0; 1146 1147 p += strspn(p, delim); 1148 while (*p != '\0') { 1149 size_t len = strcspn(p, delim); 1150 char *path; 1151 char savech; 1152 1153 savech = p[len]; 1154 p[len] = '\0'; 1155 if ((path = find_library(p, NULL)) == NULL) 1156 return -1; 1157 if (load_object(path) == NULL) 1158 return -1; /* XXX - cleanup */ 1159 p[len] = savech; 1160 p += len; 1161 p += strspn(p, delim); 1162 } 1163 return 0; 1164 } 1165 1166 /* 1167 * Load a shared object into memory, if it is not already loaded. The 1168 * argument must be a string allocated on the heap. This function assumes 1169 * responsibility for freeing it when necessary. 1170 * 1171 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1172 * on failure. 1173 */ 1174 static Obj_Entry * 1175 load_object(char *path) 1176 { 1177 Obj_Entry *obj; 1178 int fd = -1; 1179 struct stat sb; 1180 1181 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1182 if (strcmp(obj->path, path) == 0) 1183 break; 1184 1185 /* 1186 * If we didn't find a match by pathname, open the file and check 1187 * again by device and inode. This avoids false mismatches caused 1188 * by multiple links or ".." in pathnames. 1189 * 1190 * To avoid a race, we open the file and use fstat() rather than 1191 * using stat(). 1192 */ 1193 if (obj == NULL) { 1194 if ((fd = open(path, O_RDONLY)) == -1) { 1195 _rtld_error("Cannot open \"%s\"", path); 1196 return NULL; 1197 } 1198 if (fstat(fd, &sb) == -1) { 1199 _rtld_error("Cannot fstat \"%s\"", path); 1200 close(fd); 1201 return NULL; 1202 } 1203 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1204 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) { 1205 close(fd); 1206 break; 1207 } 1208 } 1209 } 1210 1211 if (obj == NULL) { /* First use of this object, so we must map it in */ 1212 dbg("loading \"%s\"", path); 1213 obj = map_object(fd, path, &sb); 1214 close(fd); 1215 if (obj == NULL) { 1216 free(path); 1217 return NULL; 1218 } 1219 1220 obj->path = path; 1221 digest_dynamic(obj, 0); 1222 1223 *obj_tail = obj; 1224 obj_tail = &obj->next; 1225 obj_count++; 1226 linkmap_add(obj); /* for GDB & dlinfo() */ 1227 1228 dbg(" %p .. %p: %s", obj->mapbase, 1229 obj->mapbase + obj->mapsize - 1, obj->path); 1230 if (obj->textrel) 1231 dbg(" WARNING: %s has impure text", obj->path); 1232 } else 1233 free(path); 1234 1235 return obj; 1236 } 1237 1238 static Obj_Entry * 1239 obj_from_addr(const void *addr) 1240 { 1241 Obj_Entry *obj; 1242 1243 for (obj = obj_list; obj != NULL; obj = obj->next) { 1244 if (addr < (void *) obj->mapbase) 1245 continue; 1246 if (addr < (void *) (obj->mapbase + obj->mapsize)) 1247 return obj; 1248 } 1249 return NULL; 1250 } 1251 1252 /* 1253 * Call the finalization functions for each of the objects in "list" 1254 * which are unreferenced. All of the objects are expected to have 1255 * non-NULL fini functions. 1256 */ 1257 static void 1258 objlist_call_fini(Objlist *list) 1259 { 1260 Objlist_Entry *elm; 1261 char *saved_msg; 1262 1263 /* 1264 * Preserve the current error message since a fini function might 1265 * call into the dynamic linker and overwrite it. 1266 */ 1267 saved_msg = errmsg_save(); 1268 STAILQ_FOREACH(elm, list, link) { 1269 if (elm->obj->refcount == 0) { 1270 dbg("calling fini function for %s at %p", elm->obj->path, 1271 (void *)elm->obj->fini); 1272 call_initfini_pointer(elm->obj, elm->obj->fini); 1273 } 1274 } 1275 errmsg_restore(saved_msg); 1276 } 1277 1278 /* 1279 * Call the initialization functions for each of the objects in 1280 * "list". All of the objects are expected to have non-NULL init 1281 * functions. 1282 */ 1283 static void 1284 objlist_call_init(Objlist *list) 1285 { 1286 Objlist_Entry *elm; 1287 char *saved_msg; 1288 1289 /* 1290 * Preserve the current error message since an init function might 1291 * call into the dynamic linker and overwrite it. 1292 */ 1293 saved_msg = errmsg_save(); 1294 STAILQ_FOREACH(elm, list, link) { 1295 dbg("calling init function for %s at %p", elm->obj->path, 1296 (void *)elm->obj->init); 1297 call_initfini_pointer(elm->obj, elm->obj->init); 1298 } 1299 errmsg_restore(saved_msg); 1300 } 1301 1302 static void 1303 objlist_clear(Objlist *list) 1304 { 1305 Objlist_Entry *elm; 1306 1307 while (!STAILQ_EMPTY(list)) { 1308 elm = STAILQ_FIRST(list); 1309 STAILQ_REMOVE_HEAD(list, link); 1310 free(elm); 1311 } 1312 } 1313 1314 static Objlist_Entry * 1315 objlist_find(Objlist *list, const Obj_Entry *obj) 1316 { 1317 Objlist_Entry *elm; 1318 1319 STAILQ_FOREACH(elm, list, link) 1320 if (elm->obj == obj) 1321 return elm; 1322 return NULL; 1323 } 1324 1325 static void 1326 objlist_init(Objlist *list) 1327 { 1328 STAILQ_INIT(list); 1329 } 1330 1331 static void 1332 objlist_push_head(Objlist *list, Obj_Entry *obj) 1333 { 1334 Objlist_Entry *elm; 1335 1336 elm = NEW(Objlist_Entry); 1337 elm->obj = obj; 1338 STAILQ_INSERT_HEAD(list, elm, link); 1339 } 1340 1341 static void 1342 objlist_push_tail(Objlist *list, Obj_Entry *obj) 1343 { 1344 Objlist_Entry *elm; 1345 1346 elm = NEW(Objlist_Entry); 1347 elm->obj = obj; 1348 STAILQ_INSERT_TAIL(list, elm, link); 1349 } 1350 1351 static void 1352 objlist_remove(Objlist *list, Obj_Entry *obj) 1353 { 1354 Objlist_Entry *elm; 1355 1356 if ((elm = objlist_find(list, obj)) != NULL) { 1357 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1358 free(elm); 1359 } 1360 } 1361 1362 /* 1363 * Remove all of the unreferenced objects from "list". 1364 */ 1365 static void 1366 objlist_remove_unref(Objlist *list) 1367 { 1368 Objlist newlist; 1369 Objlist_Entry *elm; 1370 1371 STAILQ_INIT(&newlist); 1372 while (!STAILQ_EMPTY(list)) { 1373 elm = STAILQ_FIRST(list); 1374 STAILQ_REMOVE_HEAD(list, link); 1375 if (elm->obj->refcount == 0) 1376 free(elm); 1377 else 1378 STAILQ_INSERT_TAIL(&newlist, elm, link); 1379 } 1380 *list = newlist; 1381 } 1382 1383 /* 1384 * Relocate newly-loaded shared objects. The argument is a pointer to 1385 * the Obj_Entry for the first such object. All objects from the first 1386 * to the end of the list of objects are relocated. Returns 0 on success, 1387 * or -1 on failure. 1388 */ 1389 static int 1390 relocate_objects(Obj_Entry *first, bool bind_now, Obj_Entry *rtldobj) 1391 { 1392 Obj_Entry *obj; 1393 1394 for (obj = first; obj != NULL; obj = obj->next) { 1395 if (obj != rtldobj) 1396 dbg("relocating \"%s\"", obj->path); 1397 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1398 obj->symtab == NULL || obj->strtab == NULL) { 1399 _rtld_error("%s: Shared object has no run-time symbol table", 1400 obj->path); 1401 return -1; 1402 } 1403 1404 if (obj->textrel) { 1405 /* There are relocations to the write-protected text segment. */ 1406 if (mprotect(obj->mapbase, obj->textsize, 1407 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1408 _rtld_error("%s: Cannot write-enable text segment: %s", 1409 obj->path, strerror(errno)); 1410 return -1; 1411 } 1412 } 1413 1414 /* Process the non-PLT relocations. */ 1415 if (reloc_non_plt(obj, rtldobj)) 1416 return -1; 1417 1418 if (obj->textrel) { /* Re-protected the text segment. */ 1419 if (mprotect(obj->mapbase, obj->textsize, 1420 PROT_READ|PROT_EXEC) == -1) { 1421 _rtld_error("%s: Cannot write-protect text segment: %s", 1422 obj->path, strerror(errno)); 1423 return -1; 1424 } 1425 } 1426 1427 /* Process the PLT relocations. */ 1428 if (reloc_plt(obj) == -1) 1429 return -1; 1430 /* Relocate the jump slots if we are doing immediate binding. */ 1431 if (obj->bind_now || bind_now) 1432 if (reloc_jmpslots(obj) == -1) 1433 return -1; 1434 1435 1436 /* 1437 * Set up the magic number and version in the Obj_Entry. These 1438 * were checked in the crt1.o from the original ElfKit, so we 1439 * set them for backward compatibility. 1440 */ 1441 obj->magic = RTLD_MAGIC; 1442 obj->version = RTLD_VERSION; 1443 1444 /* Set the special PLT or GOT entries. */ 1445 init_pltgot(obj); 1446 } 1447 1448 return 0; 1449 } 1450 1451 /* 1452 * Cleanup procedure. It will be called (by the atexit mechanism) just 1453 * before the process exits. 1454 */ 1455 static void 1456 rtld_exit(void) 1457 { 1458 Obj_Entry *obj; 1459 1460 dbg("rtld_exit()"); 1461 /* Clear all the reference counts so the fini functions will be called. */ 1462 for (obj = obj_list; obj != NULL; obj = obj->next) 1463 obj->refcount = 0; 1464 objlist_call_fini(&list_fini); 1465 /* No need to remove the items from the list, since we are exiting. */ 1466 if (!libmap_disable) 1467 lm_fini(); 1468 } 1469 1470 static void * 1471 path_enumerate(const char *path, path_enum_proc callback, void *arg) 1472 { 1473 #ifdef COMPAT_32BIT 1474 const char *trans; 1475 #endif 1476 if (path == NULL) 1477 return (NULL); 1478 1479 path += strspn(path, ":;"); 1480 while (*path != '\0') { 1481 size_t len; 1482 char *res; 1483 1484 len = strcspn(path, ":;"); 1485 #ifdef COMPAT_32BIT 1486 trans = lm_findn(NULL, path, len); 1487 if (trans) 1488 res = callback(trans, strlen(trans), arg); 1489 else 1490 #endif 1491 res = callback(path, len, arg); 1492 1493 if (res != NULL) 1494 return (res); 1495 1496 path += len; 1497 path += strspn(path, ":;"); 1498 } 1499 1500 return (NULL); 1501 } 1502 1503 struct try_library_args { 1504 const char *name; 1505 size_t namelen; 1506 char *buffer; 1507 size_t buflen; 1508 }; 1509 1510 static void * 1511 try_library_path(const char *dir, size_t dirlen, void *param) 1512 { 1513 struct try_library_args *arg; 1514 1515 arg = param; 1516 if (*dir == '/' || trust) { 1517 char *pathname; 1518 1519 if (dirlen + 1 + arg->namelen + 1 > arg->buflen) 1520 return (NULL); 1521 1522 pathname = arg->buffer; 1523 strncpy(pathname, dir, dirlen); 1524 pathname[dirlen] = '/'; 1525 strcpy(pathname + dirlen + 1, arg->name); 1526 1527 dbg(" Trying \"%s\"", pathname); 1528 if (access(pathname, F_OK) == 0) { /* We found it */ 1529 pathname = xmalloc(dirlen + 1 + arg->namelen + 1); 1530 strcpy(pathname, arg->buffer); 1531 return (pathname); 1532 } 1533 } 1534 return (NULL); 1535 } 1536 1537 static char * 1538 search_library_path(const char *name, const char *path) 1539 { 1540 char *p; 1541 struct try_library_args arg; 1542 1543 if (path == NULL) 1544 return NULL; 1545 1546 arg.name = name; 1547 arg.namelen = strlen(name); 1548 arg.buffer = xmalloc(PATH_MAX); 1549 arg.buflen = PATH_MAX; 1550 1551 p = path_enumerate(path, try_library_path, &arg); 1552 1553 free(arg.buffer); 1554 1555 return (p); 1556 } 1557 1558 int 1559 dlclose(void *handle) 1560 { 1561 Obj_Entry *root; 1562 int lockstate; 1563 1564 lockstate = wlock_acquire(rtld_bind_lock); 1565 root = dlcheck(handle); 1566 if (root == NULL) { 1567 wlock_release(rtld_bind_lock, lockstate); 1568 return -1; 1569 } 1570 1571 /* Unreference the object and its dependencies. */ 1572 root->dl_refcount--; 1573 1574 unref_dag(root); 1575 1576 if (root->refcount == 0) { 1577 /* 1578 * The object is no longer referenced, so we must unload it. 1579 * First, call the fini functions with no locks held. 1580 */ 1581 wlock_release(rtld_bind_lock, lockstate); 1582 objlist_call_fini(&list_fini); 1583 lockstate = wlock_acquire(rtld_bind_lock); 1584 objlist_remove_unref(&list_fini); 1585 1586 /* Finish cleaning up the newly-unreferenced objects. */ 1587 GDB_STATE(RT_DELETE,&root->linkmap); 1588 unload_object(root); 1589 GDB_STATE(RT_CONSISTENT,NULL); 1590 } 1591 wlock_release(rtld_bind_lock, lockstate); 1592 return 0; 1593 } 1594 1595 const char * 1596 dlerror(void) 1597 { 1598 char *msg = error_message; 1599 error_message = NULL; 1600 return msg; 1601 } 1602 1603 /* 1604 * This function is deprecated and has no effect. 1605 */ 1606 void 1607 dllockinit(void *context, 1608 void *(*lock_create)(void *context), 1609 void (*rlock_acquire)(void *lock), 1610 void (*wlock_acquire)(void *lock), 1611 void (*lock_release)(void *lock), 1612 void (*lock_destroy)(void *lock), 1613 void (*context_destroy)(void *context)) 1614 { 1615 static void *cur_context; 1616 static void (*cur_context_destroy)(void *); 1617 1618 /* Just destroy the context from the previous call, if necessary. */ 1619 if (cur_context_destroy != NULL) 1620 cur_context_destroy(cur_context); 1621 cur_context = context; 1622 cur_context_destroy = context_destroy; 1623 } 1624 1625 void * 1626 dlopen(const char *name, int mode) 1627 { 1628 Obj_Entry **old_obj_tail; 1629 Obj_Entry *obj; 1630 Objlist initlist; 1631 int result, lockstate; 1632 1633 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1"; 1634 if (ld_tracing != NULL) 1635 environ = (char **)*get_program_var_addr("environ"); 1636 1637 objlist_init(&initlist); 1638 1639 lockstate = wlock_acquire(rtld_bind_lock); 1640 GDB_STATE(RT_ADD,NULL); 1641 1642 old_obj_tail = obj_tail; 1643 obj = NULL; 1644 if (name == NULL) { 1645 obj = obj_main; 1646 obj->refcount++; 1647 } else { 1648 char *path = find_library(name, obj_main); 1649 if (path != NULL) 1650 obj = load_object(path); 1651 } 1652 1653 if (obj) { 1654 obj->dl_refcount++; 1655 if (mode & RTLD_GLOBAL && objlist_find(&list_global, obj) == NULL) 1656 objlist_push_tail(&list_global, obj); 1657 mode &= RTLD_MODEMASK; 1658 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1659 assert(*old_obj_tail == obj); 1660 1661 result = load_needed_objects(obj); 1662 if (result != -1 && ld_tracing) 1663 goto trace; 1664 1665 if (result == -1 || 1666 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW, 1667 &obj_rtld)) == -1) { 1668 obj->dl_refcount--; 1669 unref_dag(obj); 1670 if (obj->refcount == 0) 1671 unload_object(obj); 1672 obj = NULL; 1673 } else { 1674 /* Make list of init functions to call. */ 1675 initlist_add_objects(obj, &obj->next, &initlist); 1676 } 1677 } else { 1678 1679 /* Bump the reference counts for objects on this DAG. */ 1680 ref_dag(obj); 1681 1682 if (ld_tracing) 1683 goto trace; 1684 } 1685 } 1686 1687 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); 1688 1689 /* Call the init functions with no locks held. */ 1690 wlock_release(rtld_bind_lock, lockstate); 1691 objlist_call_init(&initlist); 1692 lockstate = wlock_acquire(rtld_bind_lock); 1693 objlist_clear(&initlist); 1694 wlock_release(rtld_bind_lock, lockstate); 1695 return obj; 1696 trace: 1697 trace_loaded_objects(obj); 1698 wlock_release(rtld_bind_lock, lockstate); 1699 exit(0); 1700 } 1701 1702 void * 1703 dlsym(void *handle, const char *name) 1704 { 1705 const Obj_Entry *obj; 1706 unsigned long hash; 1707 const Elf_Sym *def; 1708 const Obj_Entry *defobj; 1709 int lockstate; 1710 1711 hash = elf_hash(name); 1712 def = NULL; 1713 defobj = NULL; 1714 1715 lockstate = rlock_acquire(rtld_bind_lock); 1716 if (handle == NULL || handle == RTLD_NEXT || 1717 handle == RTLD_DEFAULT || handle == RTLD_SELF) { 1718 void *retaddr; 1719 1720 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1721 if ((obj = obj_from_addr(retaddr)) == NULL) { 1722 _rtld_error("Cannot determine caller's shared object"); 1723 rlock_release(rtld_bind_lock, lockstate); 1724 return NULL; 1725 } 1726 if (handle == NULL) { /* Just the caller's shared object. */ 1727 def = symlook_obj(name, hash, obj, true); 1728 defobj = obj; 1729 } else if (handle == RTLD_NEXT || /* Objects after caller's */ 1730 handle == RTLD_SELF) { /* ... caller included */ 1731 if (handle == RTLD_NEXT) 1732 obj = obj->next; 1733 for (; obj != NULL; obj = obj->next) { 1734 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1735 defobj = obj; 1736 break; 1737 } 1738 } 1739 } else { 1740 assert(handle == RTLD_DEFAULT); 1741 def = symlook_default(name, hash, obj, &defobj, true); 1742 } 1743 } else { 1744 if ((obj = dlcheck(handle)) == NULL) { 1745 rlock_release(rtld_bind_lock, lockstate); 1746 return NULL; 1747 } 1748 1749 if (obj->mainprog) { 1750 DoneList donelist; 1751 1752 /* Search main program and all libraries loaded by it. */ 1753 donelist_init(&donelist); 1754 def = symlook_list(name, hash, &list_main, &defobj, true, 1755 &donelist); 1756 } else { 1757 /* 1758 * XXX - This isn't correct. The search should include the whole 1759 * DAG rooted at the given object. 1760 */ 1761 def = symlook_obj(name, hash, obj, true); 1762 defobj = obj; 1763 } 1764 } 1765 1766 if (def != NULL) { 1767 rlock_release(rtld_bind_lock, lockstate); 1768 1769 /* 1770 * The value required by the caller is derived from the value 1771 * of the symbol. For the ia64 architecture, we need to 1772 * construct a function descriptor which the caller can use to 1773 * call the function with the right 'gp' value. For other 1774 * architectures and for non-functions, the value is simply 1775 * the relocated value of the symbol. 1776 */ 1777 if (ELF_ST_TYPE(def->st_info) == STT_FUNC) 1778 return make_function_pointer(def, defobj); 1779 else 1780 return defobj->relocbase + def->st_value; 1781 } 1782 1783 _rtld_error("Undefined symbol \"%s\"", name); 1784 rlock_release(rtld_bind_lock, lockstate); 1785 return NULL; 1786 } 1787 1788 int 1789 dladdr(const void *addr, Dl_info *info) 1790 { 1791 const Obj_Entry *obj; 1792 const Elf_Sym *def; 1793 void *symbol_addr; 1794 unsigned long symoffset; 1795 int lockstate; 1796 1797 lockstate = rlock_acquire(rtld_bind_lock); 1798 obj = obj_from_addr(addr); 1799 if (obj == NULL) { 1800 _rtld_error("No shared object contains address"); 1801 rlock_release(rtld_bind_lock, lockstate); 1802 return 0; 1803 } 1804 info->dli_fname = obj->path; 1805 info->dli_fbase = obj->mapbase; 1806 info->dli_saddr = (void *)0; 1807 info->dli_sname = NULL; 1808 1809 /* 1810 * Walk the symbol list looking for the symbol whose address is 1811 * closest to the address sent in. 1812 */ 1813 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1814 def = obj->symtab + symoffset; 1815 1816 /* 1817 * For skip the symbol if st_shndx is either SHN_UNDEF or 1818 * SHN_COMMON. 1819 */ 1820 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1821 continue; 1822 1823 /* 1824 * If the symbol is greater than the specified address, or if it 1825 * is further away from addr than the current nearest symbol, 1826 * then reject it. 1827 */ 1828 symbol_addr = obj->relocbase + def->st_value; 1829 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1830 continue; 1831 1832 /* Update our idea of the nearest symbol. */ 1833 info->dli_sname = obj->strtab + def->st_name; 1834 info->dli_saddr = symbol_addr; 1835 1836 /* Exact match? */ 1837 if (info->dli_saddr == addr) 1838 break; 1839 } 1840 rlock_release(rtld_bind_lock, lockstate); 1841 return 1; 1842 } 1843 1844 int 1845 dlinfo(void *handle, int request, void *p) 1846 { 1847 const Obj_Entry *obj; 1848 int error, lockstate; 1849 1850 lockstate = rlock_acquire(rtld_bind_lock); 1851 1852 if (handle == NULL || handle == RTLD_SELF) { 1853 void *retaddr; 1854 1855 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1856 if ((obj = obj_from_addr(retaddr)) == NULL) 1857 _rtld_error("Cannot determine caller's shared object"); 1858 } else 1859 obj = dlcheck(handle); 1860 1861 if (obj == NULL) { 1862 rlock_release(rtld_bind_lock, lockstate); 1863 return (-1); 1864 } 1865 1866 error = 0; 1867 switch (request) { 1868 case RTLD_DI_LINKMAP: 1869 *((struct link_map const **)p) = &obj->linkmap; 1870 break; 1871 case RTLD_DI_ORIGIN: 1872 error = rtld_dirname(obj->path, p); 1873 break; 1874 1875 case RTLD_DI_SERINFOSIZE: 1876 case RTLD_DI_SERINFO: 1877 error = do_search_info(obj, request, (struct dl_serinfo *)p); 1878 break; 1879 1880 default: 1881 _rtld_error("Invalid request %d passed to dlinfo()", request); 1882 error = -1; 1883 } 1884 1885 rlock_release(rtld_bind_lock, lockstate); 1886 1887 return (error); 1888 } 1889 1890 struct fill_search_info_args { 1891 int request; 1892 unsigned int flags; 1893 Dl_serinfo *serinfo; 1894 Dl_serpath *serpath; 1895 char *strspace; 1896 }; 1897 1898 static void * 1899 fill_search_info(const char *dir, size_t dirlen, void *param) 1900 { 1901 struct fill_search_info_args *arg; 1902 1903 arg = param; 1904 1905 if (arg->request == RTLD_DI_SERINFOSIZE) { 1906 arg->serinfo->dls_cnt ++; 1907 arg->serinfo->dls_size += dirlen + 1; 1908 } else { 1909 struct dl_serpath *s_entry; 1910 1911 s_entry = arg->serpath; 1912 s_entry->dls_name = arg->strspace; 1913 s_entry->dls_flags = arg->flags; 1914 1915 strncpy(arg->strspace, dir, dirlen); 1916 arg->strspace[dirlen] = '\0'; 1917 1918 arg->strspace += dirlen + 1; 1919 arg->serpath++; 1920 } 1921 1922 return (NULL); 1923 } 1924 1925 static int 1926 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info) 1927 { 1928 struct dl_serinfo _info; 1929 struct fill_search_info_args args; 1930 1931 args.request = RTLD_DI_SERINFOSIZE; 1932 args.serinfo = &_info; 1933 1934 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath); 1935 _info.dls_cnt = 0; 1936 1937 path_enumerate(ld_library_path, fill_search_info, &args); 1938 path_enumerate(obj->rpath, fill_search_info, &args); 1939 path_enumerate(gethints(), fill_search_info, &args); 1940 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args); 1941 1942 1943 if (request == RTLD_DI_SERINFOSIZE) { 1944 info->dls_size = _info.dls_size; 1945 info->dls_cnt = _info.dls_cnt; 1946 return (0); 1947 } 1948 1949 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) { 1950 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()"); 1951 return (-1); 1952 } 1953 1954 args.request = RTLD_DI_SERINFO; 1955 args.serinfo = info; 1956 args.serpath = &info->dls_serpath[0]; 1957 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt]; 1958 1959 args.flags = LA_SER_LIBPATH; 1960 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL) 1961 return (-1); 1962 1963 args.flags = LA_SER_RUNPATH; 1964 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL) 1965 return (-1); 1966 1967 args.flags = LA_SER_CONFIG; 1968 if (path_enumerate(gethints(), fill_search_info, &args) != NULL) 1969 return (-1); 1970 1971 args.flags = LA_SER_DEFAULT; 1972 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL) 1973 return (-1); 1974 return (0); 1975 } 1976 1977 static int 1978 rtld_dirname(const char *path, char *bname) 1979 { 1980 const char *endp; 1981 1982 /* Empty or NULL string gets treated as "." */ 1983 if (path == NULL || *path == '\0') { 1984 bname[0] = '.'; 1985 bname[1] = '\0'; 1986 return (0); 1987 } 1988 1989 /* Strip trailing slashes */ 1990 endp = path + strlen(path) - 1; 1991 while (endp > path && *endp == '/') 1992 endp--; 1993 1994 /* Find the start of the dir */ 1995 while (endp > path && *endp != '/') 1996 endp--; 1997 1998 /* Either the dir is "/" or there are no slashes */ 1999 if (endp == path) { 2000 bname[0] = *endp == '/' ? '/' : '.'; 2001 bname[1] = '\0'; 2002 return (0); 2003 } else { 2004 do { 2005 endp--; 2006 } while (endp > path && *endp == '/'); 2007 } 2008 2009 if (endp - path + 2 > PATH_MAX) 2010 { 2011 _rtld_error("Filename is too long: %s", path); 2012 return(-1); 2013 } 2014 2015 strncpy(bname, path, endp - path + 1); 2016 bname[endp - path + 1] = '\0'; 2017 return (0); 2018 } 2019 2020 static void 2021 linkmap_add(Obj_Entry *obj) 2022 { 2023 struct link_map *l = &obj->linkmap; 2024 struct link_map *prev; 2025 2026 obj->linkmap.l_name = obj->path; 2027 obj->linkmap.l_addr = obj->mapbase; 2028 obj->linkmap.l_ld = obj->dynamic; 2029 #ifdef __mips__ 2030 /* GDB needs load offset on MIPS to use the symbols */ 2031 obj->linkmap.l_offs = obj->relocbase; 2032 #endif 2033 2034 if (r_debug.r_map == NULL) { 2035 r_debug.r_map = l; 2036 return; 2037 } 2038 2039 /* 2040 * Scan to the end of the list, but not past the entry for the 2041 * dynamic linker, which we want to keep at the very end. 2042 */ 2043 for (prev = r_debug.r_map; 2044 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 2045 prev = prev->l_next) 2046 ; 2047 2048 /* Link in the new entry. */ 2049 l->l_prev = prev; 2050 l->l_next = prev->l_next; 2051 if (l->l_next != NULL) 2052 l->l_next->l_prev = l; 2053 prev->l_next = l; 2054 } 2055 2056 static void 2057 linkmap_delete(Obj_Entry *obj) 2058 { 2059 struct link_map *l = &obj->linkmap; 2060 2061 if (l->l_prev == NULL) { 2062 if ((r_debug.r_map = l->l_next) != NULL) 2063 l->l_next->l_prev = NULL; 2064 return; 2065 } 2066 2067 if ((l->l_prev->l_next = l->l_next) != NULL) 2068 l->l_next->l_prev = l->l_prev; 2069 } 2070 2071 /* 2072 * Function for the debugger to set a breakpoint on to gain control. 2073 * 2074 * The two parameters allow the debugger to easily find and determine 2075 * what the runtime loader is doing and to whom it is doing it. 2076 * 2077 * When the loadhook trap is hit (r_debug_state, set at program 2078 * initialization), the arguments can be found on the stack: 2079 * 2080 * +8 struct link_map *m 2081 * +4 struct r_debug *rd 2082 * +0 RetAddr 2083 */ 2084 void 2085 r_debug_state(struct r_debug* rd, struct link_map *m) 2086 { 2087 } 2088 2089 /* 2090 * Get address of the pointer variable in the main program. 2091 */ 2092 static const void ** 2093 get_program_var_addr(const char *name) 2094 { 2095 const Obj_Entry *obj; 2096 unsigned long hash; 2097 2098 hash = elf_hash(name); 2099 for (obj = obj_main; obj != NULL; obj = obj->next) { 2100 const Elf_Sym *def; 2101 2102 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 2103 const void **addr; 2104 2105 addr = (const void **)(obj->relocbase + def->st_value); 2106 return addr; 2107 } 2108 } 2109 return NULL; 2110 } 2111 2112 /* 2113 * Set a pointer variable in the main program to the given value. This 2114 * is used to set key variables such as "environ" before any of the 2115 * init functions are called. 2116 */ 2117 static void 2118 set_program_var(const char *name, const void *value) 2119 { 2120 const void **addr; 2121 2122 if ((addr = get_program_var_addr(name)) != NULL) { 2123 dbg("\"%s\": *%p <-- %p", name, addr, value); 2124 *addr = value; 2125 } 2126 } 2127 2128 /* 2129 * Given a symbol name in a referencing object, find the corresponding 2130 * definition of the symbol. Returns a pointer to the symbol, or NULL if 2131 * no definition was found. Returns a pointer to the Obj_Entry of the 2132 * defining object via the reference parameter DEFOBJ_OUT. 2133 */ 2134 static const Elf_Sym * 2135 symlook_default(const char *name, unsigned long hash, 2136 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) 2137 { 2138 DoneList donelist; 2139 const Elf_Sym *def; 2140 const Elf_Sym *symp; 2141 const Obj_Entry *obj; 2142 const Obj_Entry *defobj; 2143 const Objlist_Entry *elm; 2144 def = NULL; 2145 defobj = NULL; 2146 donelist_init(&donelist); 2147 2148 /* Look first in the referencing object if linked symbolically. */ 2149 if (refobj->symbolic && !donelist_check(&donelist, refobj)) { 2150 symp = symlook_obj(name, hash, refobj, in_plt); 2151 if (symp != NULL) { 2152 def = symp; 2153 defobj = refobj; 2154 } 2155 } 2156 2157 /* Search all objects loaded at program start up. */ 2158 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2159 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); 2160 if (symp != NULL && 2161 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2162 def = symp; 2163 defobj = obj; 2164 } 2165 } 2166 2167 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */ 2168 STAILQ_FOREACH(elm, &list_global, link) { 2169 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2170 break; 2171 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2172 &donelist); 2173 if (symp != NULL && 2174 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2175 def = symp; 2176 defobj = obj; 2177 } 2178 } 2179 2180 /* Search all dlopened DAGs containing the referencing object. */ 2181 STAILQ_FOREACH(elm, &refobj->dldags, link) { 2182 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2183 break; 2184 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2185 &donelist); 2186 if (symp != NULL && 2187 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2188 def = symp; 2189 defobj = obj; 2190 } 2191 } 2192 2193 /* 2194 * Search the dynamic linker itself, and possibly resolve the 2195 * symbol from there. This is how the application links to 2196 * dynamic linker services such as dlopen. Only the values listed 2197 * in the "exports" array can be resolved from the dynamic linker. 2198 */ 2199 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2200 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 2201 if (symp != NULL && is_exported(symp)) { 2202 def = symp; 2203 defobj = &obj_rtld; 2204 } 2205 } 2206 2207 if (def != NULL) 2208 *defobj_out = defobj; 2209 return def; 2210 } 2211 2212 static const Elf_Sym * 2213 symlook_list(const char *name, unsigned long hash, Objlist *objlist, 2214 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 2215 { 2216 const Elf_Sym *symp; 2217 const Elf_Sym *def; 2218 const Obj_Entry *defobj; 2219 const Objlist_Entry *elm; 2220 2221 def = NULL; 2222 defobj = NULL; 2223 STAILQ_FOREACH(elm, objlist, link) { 2224 if (donelist_check(dlp, elm->obj)) 2225 continue; 2226 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 2227 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 2228 def = symp; 2229 defobj = elm->obj; 2230 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 2231 break; 2232 } 2233 } 2234 } 2235 if (def != NULL) 2236 *defobj_out = defobj; 2237 return def; 2238 } 2239 2240 /* 2241 * Search the symbol table of a single shared object for a symbol of 2242 * the given name. Returns a pointer to the symbol, or NULL if no 2243 * definition was found. 2244 * 2245 * The symbol's hash value is passed in for efficiency reasons; that 2246 * eliminates many recomputations of the hash value. 2247 */ 2248 const Elf_Sym * 2249 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 2250 bool in_plt) 2251 { 2252 if (obj->buckets != NULL) { 2253 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 2254 2255 while (symnum != STN_UNDEF) { 2256 const Elf_Sym *symp; 2257 const char *strp; 2258 2259 if (symnum >= obj->nchains) 2260 return NULL; /* Bad object */ 2261 symp = obj->symtab + symnum; 2262 strp = obj->strtab + symp->st_name; 2263 2264 if (name[0] == strp[0] && strcmp(name, strp) == 0) 2265 return symp->st_shndx != SHN_UNDEF || 2266 (!in_plt && symp->st_value != 0 && 2267 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 2268 2269 symnum = obj->chains[symnum]; 2270 } 2271 } 2272 return NULL; 2273 } 2274 2275 static void 2276 trace_loaded_objects(Obj_Entry *obj) 2277 { 2278 char *fmt1, *fmt2, *fmt, *main_local, *list_containers; 2279 int c; 2280 2281 if ((main_local = getenv(LD_ "TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 2282 main_local = ""; 2283 2284 if ((fmt1 = getenv(LD_ "TRACE_LOADED_OBJECTS_FMT1")) == NULL) 2285 fmt1 = "\t%o => %p (%x)\n"; 2286 2287 if ((fmt2 = getenv(LD_ "TRACE_LOADED_OBJECTS_FMT2")) == NULL) 2288 fmt2 = "\t%o (%x)\n"; 2289 2290 list_containers = getenv(LD_ "TRACE_LOADED_OBJECTS_ALL"); 2291 2292 for (; obj; obj = obj->next) { 2293 Needed_Entry *needed; 2294 char *name, *path; 2295 bool is_lib; 2296 2297 if (list_containers && obj->needed != NULL) 2298 printf("%s:\n", obj->path); 2299 for (needed = obj->needed; needed; needed = needed->next) { 2300 if (needed->obj != NULL) { 2301 if (needed->obj->traced && !list_containers) 2302 continue; 2303 needed->obj->traced = true; 2304 path = needed->obj->path; 2305 } else 2306 path = "not found"; 2307 2308 name = (char *)obj->strtab + needed->name; 2309 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 2310 2311 fmt = is_lib ? fmt1 : fmt2; 2312 while ((c = *fmt++) != '\0') { 2313 switch (c) { 2314 default: 2315 putchar(c); 2316 continue; 2317 case '\\': 2318 switch (c = *fmt) { 2319 case '\0': 2320 continue; 2321 case 'n': 2322 putchar('\n'); 2323 break; 2324 case 't': 2325 putchar('\t'); 2326 break; 2327 } 2328 break; 2329 case '%': 2330 switch (c = *fmt) { 2331 case '\0': 2332 continue; 2333 case '%': 2334 default: 2335 putchar(c); 2336 break; 2337 case 'A': 2338 printf("%s", main_local); 2339 break; 2340 case 'a': 2341 printf("%s", obj_main->path); 2342 break; 2343 case 'o': 2344 printf("%s", name); 2345 break; 2346 #if 0 2347 case 'm': 2348 printf("%d", sodp->sod_major); 2349 break; 2350 case 'n': 2351 printf("%d", sodp->sod_minor); 2352 break; 2353 #endif 2354 case 'p': 2355 printf("%s", path); 2356 break; 2357 case 'x': 2358 printf("%p", needed->obj ? needed->obj->mapbase : 0); 2359 break; 2360 } 2361 break; 2362 } 2363 ++fmt; 2364 } 2365 } 2366 } 2367 } 2368 2369 /* 2370 * Unload a dlopened object and its dependencies from memory and from 2371 * our data structures. It is assumed that the DAG rooted in the 2372 * object has already been unreferenced, and that the object has a 2373 * reference count of 0. 2374 */ 2375 static void 2376 unload_object(Obj_Entry *root) 2377 { 2378 Obj_Entry *obj; 2379 Obj_Entry **linkp; 2380 2381 assert(root->refcount == 0); 2382 2383 /* 2384 * Pass over the DAG removing unreferenced objects from 2385 * appropriate lists. 2386 */ 2387 unlink_object(root); 2388 2389 /* Unmap all objects that are no longer referenced. */ 2390 linkp = &obj_list->next; 2391 while ((obj = *linkp) != NULL) { 2392 if (obj->refcount == 0) { 2393 dbg("unloading \"%s\"", obj->path); 2394 munmap(obj->mapbase, obj->mapsize); 2395 linkmap_delete(obj); 2396 *linkp = obj->next; 2397 obj_count--; 2398 obj_free(obj); 2399 } else 2400 linkp = &obj->next; 2401 } 2402 obj_tail = linkp; 2403 } 2404 2405 static void 2406 unlink_object(Obj_Entry *root) 2407 { 2408 Objlist_Entry *elm; 2409 2410 if (root->refcount == 0) { 2411 /* Remove the object from the RTLD_GLOBAL list. */ 2412 objlist_remove(&list_global, root); 2413 2414 /* Remove the object from all objects' DAG lists. */ 2415 STAILQ_FOREACH(elm, &root->dagmembers , link) { 2416 objlist_remove(&elm->obj->dldags, root); 2417 if (elm->obj != root) 2418 unlink_object(elm->obj); 2419 } 2420 } 2421 } 2422 2423 static void 2424 ref_dag(Obj_Entry *root) 2425 { 2426 Objlist_Entry *elm; 2427 2428 STAILQ_FOREACH(elm, &root->dagmembers , link) 2429 elm->obj->refcount++; 2430 } 2431 2432 static void 2433 unref_dag(Obj_Entry *root) 2434 { 2435 Objlist_Entry *elm; 2436 2437 STAILQ_FOREACH(elm, &root->dagmembers , link) 2438 elm->obj->refcount--; 2439 } 2440 2441 2442