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: src/libexec/rtld-elf/rtld.c,v 1.43.2.15 2003/02/20 20:42:46 kan Exp $ 27 * $DragonFly: src/libexec/rtld-elf/rtld.c,v 1.24 2006/07/16 22:15:38 corecode Exp $ 28 */ 29 30 /* 31 * Dynamic linker for ELF. 32 * 33 * John Polstra <jdp@polstra.com>. 34 */ 35 36 #ifndef __GNUC__ 37 #error "GCC is needed to compile this file" 38 #endif 39 40 #include <sys/param.h> 41 #include <sys/mman.h> 42 #include <sys/stat.h> 43 #include <sys/resident.h> 44 #include <sys/tls.h> 45 46 #include <machine/tls.h> 47 48 #include <dlfcn.h> 49 #include <err.h> 50 #include <errno.h> 51 #include <fcntl.h> 52 #include <stdarg.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include <unistd.h> 57 58 #include "debug.h" 59 #include "rtld.h" 60 61 #define PATH_RTLD "/usr/libexec/ld-elf.so.2" 62 #define LD_ARY_CACHE 16 63 64 /* Types. */ 65 typedef void (*func_ptr_type)(); 66 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg); 67 68 /* 69 * This structure provides a reentrant way to keep a list of objects and 70 * check which ones have already been processed in some way. 71 */ 72 typedef struct Struct_DoneList { 73 const Obj_Entry **objs; /* Array of object pointers */ 74 unsigned int num_alloc; /* Allocated size of the array */ 75 unsigned int num_used; /* Number of array slots used */ 76 } DoneList; 77 78 /* 79 * Function declarations. 80 */ 81 static void die(void); 82 static void digest_dynamic(Obj_Entry *); 83 static const char *_getenv_ld(const char *id); 84 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *); 85 static Obj_Entry *dlcheck(void *); 86 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *); 87 static bool donelist_check(DoneList *, const Obj_Entry *); 88 static void errmsg_restore(char *); 89 static char *errmsg_save(void); 90 static void *fill_search_info(const char *, size_t, void *); 91 static char *find_library(const char *, const Obj_Entry *); 92 static Obj_Entry *find_object(const char *); 93 static Obj_Entry *find_object2(const char *, int *, struct stat *); 94 static const char *gethints(void); 95 static void init_dag(Obj_Entry *); 96 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *); 97 static void init_rtld(caddr_t); 98 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list); 99 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, 100 Objlist *list); 101 static bool is_exported(const Elf_Sym *); 102 static void linkmap_add(Obj_Entry *); 103 static void linkmap_delete(Obj_Entry *); 104 static int load_needed_objects(Obj_Entry *); 105 static int load_preload_objects(void); 106 static Obj_Entry *load_object(char *); 107 static void lock_check(void); 108 static Obj_Entry *obj_from_addr(const void *); 109 static void objlist_call_fini(Objlist *); 110 static void objlist_call_init(Objlist *); 111 static void objlist_clear(Objlist *); 112 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *); 113 static void objlist_init(Objlist *); 114 static void objlist_push_head(Objlist *, Obj_Entry *); 115 static void objlist_push_tail(Objlist *, Obj_Entry *); 116 static void objlist_remove(Objlist *, Obj_Entry *); 117 static void objlist_remove_unref(Objlist *); 118 static void *path_enumerate(const char *, path_enum_proc, void *); 119 static int relocate_objects(Obj_Entry *, bool); 120 static int rtld_dirname(const char *, char *); 121 static void rtld_exit(void); 122 static char *search_library_path(const char *, const char *); 123 static const void **get_program_var_addr(const char *name); 124 static void set_program_var(const char *, const void *); 125 static const Elf_Sym *symlook_default(const char *, unsigned long hash, 126 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt); 127 static const Elf_Sym *symlook_list(const char *, unsigned long, 128 const Objlist *, const Obj_Entry **, bool in_plt, DoneList *); 129 static void trace_loaded_objects(Obj_Entry *obj); 130 static void unlink_object(Obj_Entry *); 131 static void unload_object(Obj_Entry *); 132 static void unref_dag(Obj_Entry *); 133 134 void r_debug_state(struct r_debug*, struct link_map*); 135 136 /* 137 * Data declarations. 138 */ 139 static char *error_message; /* Message for dlerror(), or NULL */ 140 struct r_debug r_debug; /* for GDB; */ 141 static bool trust; /* False for setuid and setgid programs */ 142 static const char *ld_bind_now; /* Environment variable for immediate binding */ 143 static const char *ld_debug; /* Environment variable for debugging */ 144 static const char *ld_library_path; /* Environment variable for search path */ 145 static char *ld_preload; /* Environment variable for libraries to 146 load first */ 147 static const char *ld_tracing; /* Called from ldd(1) to print libs */ 148 static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 149 static Obj_Entry **obj_tail; /* Link field of last object in list */ 150 static Obj_Entry **preload_tail; 151 static Obj_Entry *obj_main; /* The main program shared object */ 152 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 153 static unsigned int obj_count; /* Number of objects in obj_list */ 154 static int ld_resident; /* Non-zero if resident */ 155 static const char *ld_ary[LD_ARY_CACHE]; 156 static int ld_index; 157 static Objlist initlist; 158 159 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 160 STAILQ_HEAD_INITIALIZER(list_global); 161 static Objlist list_main = /* Objects loaded at program startup */ 162 STAILQ_HEAD_INITIALIZER(list_main); 163 static Objlist list_fini = /* Objects needing fini() calls */ 164 STAILQ_HEAD_INITIALIZER(list_fini); 165 166 static LockInfo lockinfo; 167 168 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 169 170 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); 171 172 extern Elf_Dyn _DYNAMIC; 173 #pragma weak _DYNAMIC 174 175 /* 176 * These are the functions the dynamic linker exports to application 177 * programs. They are the only symbols the dynamic linker is willing 178 * to export from itself. 179 */ 180 static func_ptr_type exports[] = { 181 (func_ptr_type) &_rtld_error, 182 (func_ptr_type) &dlclose, 183 (func_ptr_type) &dlerror, 184 (func_ptr_type) &dlopen, 185 (func_ptr_type) &dlsym, 186 (func_ptr_type) &dladdr, 187 (func_ptr_type) &dlinfo, 188 #ifdef __i386__ 189 (func_ptr_type) &___tls_get_addr, 190 #endif 191 (func_ptr_type) &__tls_get_addr, 192 (func_ptr_type) &__tls_get_addr_tcb, 193 (func_ptr_type) &_rtld_allocate_tls, 194 (func_ptr_type) &_rtld_free_tls, 195 (func_ptr_type) &_rtld_call_init, 196 NULL 197 }; 198 199 /* 200 * Global declarations normally provided by crt1. The dynamic linker is 201 * not built with crt1, so we have to provide them ourselves. 202 */ 203 char *__progname; 204 char **environ; 205 206 /* 207 * Globals to control TLS allocation. 208 */ 209 size_t tls_last_offset; /* Static TLS offset of last module */ 210 size_t tls_last_size; /* Static TLS size of last module */ 211 size_t tls_static_space; /* Static TLS space allocated */ 212 int tls_dtv_generation = 1; /* Used to detect when dtv size changes */ 213 int tls_max_index = 1; /* Largest module index allocated */ 214 215 /* 216 * Fill in a DoneList with an allocation large enough to hold all of 217 * the currently-loaded objects. Keep this as a macro since it calls 218 * alloca and we want that to occur within the scope of the caller. 219 */ 220 #define donelist_init(dlp) \ 221 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ 222 assert((dlp)->objs != NULL), \ 223 (dlp)->num_alloc = obj_count, \ 224 (dlp)->num_used = 0) 225 226 static __inline void 227 rlock_acquire(void) 228 { 229 lockinfo.rlock_acquire(lockinfo.thelock); 230 atomic_incr_int(&lockinfo.rcount); 231 lock_check(); 232 } 233 234 static __inline void 235 wlock_acquire(void) 236 { 237 lockinfo.wlock_acquire(lockinfo.thelock); 238 atomic_incr_int(&lockinfo.wcount); 239 lock_check(); 240 } 241 242 static __inline void 243 rlock_release(void) 244 { 245 atomic_decr_int(&lockinfo.rcount); 246 lockinfo.rlock_release(lockinfo.thelock); 247 } 248 249 static __inline void 250 wlock_release(void) 251 { 252 atomic_decr_int(&lockinfo.wcount); 253 lockinfo.wlock_release(lockinfo.thelock); 254 } 255 256 /* 257 * Main entry point for dynamic linking. The first argument is the 258 * stack pointer. The stack is expected to be laid out as described 259 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 260 * Specifically, the stack pointer points to a word containing 261 * ARGC. Following that in the stack is a null-terminated sequence 262 * of pointers to argument strings. Then comes a null-terminated 263 * sequence of pointers to environment strings. Finally, there is a 264 * sequence of "auxiliary vector" entries. 265 * 266 * The second argument points to a place to store the dynamic linker's 267 * exit procedure pointer and the third to a place to store the main 268 * program's object. 269 * 270 * The return value is the main program's entry point. 271 */ 272 273 func_ptr_type 274 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 275 { 276 Elf_Auxinfo *aux_info[AT_COUNT]; 277 int i; 278 int argc; 279 char **argv; 280 char **env; 281 Elf_Auxinfo *aux; 282 Elf_Auxinfo *auxp; 283 const char *argv0; 284 Objlist_Entry *entry; 285 Obj_Entry *obj; 286 287 ld_index = 0; /* don't use old env cache in case we are resident */ 288 289 /* 290 * On entry, the dynamic linker itself has not been relocated yet. 291 * Be very careful not to reference any global data until after 292 * init_rtld has returned. It is OK to reference file-scope statics 293 * and string constants, and to call static and global functions. 294 */ 295 296 /* Find the auxiliary vector on the stack. */ 297 argc = *sp++; 298 argv = (char **) sp; 299 sp += argc + 1; /* Skip over arguments and NULL terminator */ 300 env = (char **) sp; 301 302 /* 303 * If we aren't already resident we have to dig out some more info. 304 * Note that auxinfo does not exist when we are resident. 305 */ 306 if (ld_resident == 0) { 307 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 308 ; 309 aux = (Elf_Auxinfo *) sp; 310 311 /* Digest the auxiliary vector. */ 312 for (i = 0; i < AT_COUNT; i++) 313 aux_info[i] = NULL; 314 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 315 if (auxp->a_type < AT_COUNT) 316 aux_info[auxp->a_type] = auxp; 317 } 318 319 /* Initialize and relocate ourselves. */ 320 assert(aux_info[AT_BASE] != NULL); 321 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 322 } 323 324 __progname = obj_rtld.path; 325 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 326 environ = env; 327 328 trust = (geteuid() == getuid()) && (getegid() == getgid()); 329 330 ld_bind_now = _getenv_ld("LD_BIND_NOW"); 331 if (trust) { 332 ld_debug = _getenv_ld("LD_DEBUG"); 333 ld_library_path = _getenv_ld("LD_LIBRARY_PATH"); 334 ld_preload = (char *)_getenv_ld("LD_PRELOAD"); 335 } 336 ld_tracing = _getenv_ld("LD_TRACE_LOADED_OBJECTS"); 337 338 if (ld_debug != NULL && *ld_debug != '\0') 339 debug = 1; 340 dbg("%s is initialized, base address = %p", __progname, 341 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 342 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 343 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 344 345 /* 346 * If we are resident we can skip work that we have already done. 347 * Note that the stack is reset and there is no Elf_Auxinfo 348 * when running from a resident image, and the static globals setup 349 * between here and resident_skip will have already been setup. 350 */ 351 if (ld_resident) 352 goto resident_skip1; 353 354 /* 355 * Load the main program, or process its program header if it is 356 * already loaded. 357 */ 358 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 359 int fd = aux_info[AT_EXECFD]->a_un.a_val; 360 dbg("loading main program"); 361 obj_main = map_object(fd, argv0, NULL); 362 close(fd); 363 if (obj_main == NULL) 364 die(); 365 } else { /* Main program already loaded. */ 366 const Elf_Phdr *phdr; 367 int phnum; 368 caddr_t entry; 369 370 dbg("processing main program's program header"); 371 assert(aux_info[AT_PHDR] != NULL); 372 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 373 assert(aux_info[AT_PHNUM] != NULL); 374 phnum = aux_info[AT_PHNUM]->a_un.a_val; 375 assert(aux_info[AT_PHENT] != NULL); 376 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 377 assert(aux_info[AT_ENTRY] != NULL); 378 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 379 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 380 die(); 381 } 382 383 obj_main->path = xstrdup(argv0); 384 obj_main->mainprog = true; 385 386 /* 387 * Get the actual dynamic linker pathname from the executable if 388 * possible. (It should always be possible.) That ensures that 389 * gdb will find the right dynamic linker even if a non-standard 390 * one is being used. 391 */ 392 if (obj_main->interp != NULL && 393 strcmp(obj_main->interp, obj_rtld.path) != 0) { 394 free(obj_rtld.path); 395 obj_rtld.path = xstrdup(obj_main->interp); 396 __progname = obj_rtld.path; 397 } 398 399 digest_dynamic(obj_main); 400 401 linkmap_add(obj_main); 402 linkmap_add(&obj_rtld); 403 404 /* Link the main program into the list of objects. */ 405 *obj_tail = obj_main; 406 obj_tail = &obj_main->next; 407 obj_count++; 408 obj_main->refcount++; 409 /* Make sure we don't call the main program's init and fini functions. */ 410 obj_main->init = obj_main->fini = NULL; 411 412 /* Initialize a fake symbol for resolving undefined weak references. */ 413 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 414 sym_zero.st_shndx = SHN_ABS; 415 416 dbg("loading LD_PRELOAD libraries"); 417 if (load_preload_objects() == -1) 418 die(); 419 preload_tail = obj_tail; 420 421 dbg("loading needed objects"); 422 if (load_needed_objects(obj_main) == -1) 423 die(); 424 425 /* Make a list of all objects loaded at startup. */ 426 for (obj = obj_list; obj != NULL; obj = obj->next) 427 objlist_push_tail(&list_main, obj); 428 429 resident_skip1: 430 431 if (ld_tracing) { /* We're done */ 432 trace_loaded_objects(obj_main); 433 exit(0); 434 } 435 436 if (ld_resident) /* XXX clean this up! */ 437 goto resident_skip2; 438 439 if (getenv("LD_DUMP_REL_PRE") != NULL) { 440 dump_relocations(obj_main); 441 exit (0); 442 } 443 444 /* setup TLS for main thread */ 445 dbg("initializing initial thread local storage"); 446 STAILQ_FOREACH(entry, &list_main, link) { 447 /* 448 * Allocate all the initial objects out of the static TLS 449 * block even if they didn't ask for it. 450 */ 451 allocate_tls_offset(entry->obj); 452 } 453 454 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 455 456 /* 457 * Do not try to allocate the TLS here, let libc do it itself. 458 * (crt1 for the program will call _init_tls()) 459 */ 460 461 if (relocate_objects(obj_main, 462 ld_bind_now != NULL && *ld_bind_now != '\0') == -1) 463 die(); 464 465 dbg("doing copy relocations"); 466 if (do_copy_relocations(obj_main) == -1) 467 die(); 468 469 resident_skip2: 470 471 if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) { 472 if (exec_sys_unregister(-1) < 0) { 473 dbg("exec_sys_unregister failed %d\n", errno); 474 exit(errno); 475 } 476 dbg("exec_sys_unregister success\n"); 477 exit(0); 478 } 479 480 if (getenv("LD_DUMP_REL_POST") != NULL) { 481 dump_relocations(obj_main); 482 exit (0); 483 } 484 485 dbg("initializing key program variables"); 486 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 487 set_program_var("environ", env); 488 489 if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) { 490 extern void resident_start(void); 491 ld_resident = 1; 492 if (exec_sys_register(resident_start) < 0) { 493 dbg("exec_sys_register failed %d\n", errno); 494 exit(errno); 495 } 496 dbg("exec_sys_register success\n"); 497 exit(0); 498 } 499 500 dbg("initializing thread locks"); 501 lockdflt_init(&lockinfo); 502 lockinfo.thelock = lockinfo.lock_create(lockinfo.context); 503 504 /* Make a list of init functions to call. */ 505 objlist_init(&initlist); 506 initlist_add_objects(obj_list, preload_tail, &initlist); 507 508 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ 509 510 /* 511 * Do NOT call the initlist here, give libc a chance to set up 512 * the initial TLS segment. crt1 will then call _rtld_call_init(). 513 */ 514 515 dbg("transferring control to program entry point = %p", obj_main->entry); 516 517 /* Return the exit procedure and the program entry point. */ 518 *exit_proc = rtld_exit; 519 *objp = obj_main; 520 return (func_ptr_type) obj_main->entry; 521 } 522 523 /* 524 * Call the initialization list for dynamically loaded libraries. 525 * (called from crt1.c). 526 */ 527 void 528 _rtld_call_init(void) 529 { 530 objlist_call_init(&initlist); 531 wlock_acquire(); 532 objlist_clear(&initlist); 533 wlock_release(); 534 } 535 536 Elf_Addr 537 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 538 { 539 const Elf_Rel *rel; 540 const Elf_Sym *def; 541 const Obj_Entry *defobj; 542 Elf_Addr *where; 543 Elf_Addr target; 544 545 rlock_acquire(); 546 if (obj->pltrel) 547 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 548 else 549 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 550 551 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 552 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 553 if (def == NULL) 554 die(); 555 556 target = (Elf_Addr)(defobj->relocbase + def->st_value); 557 558 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 559 defobj->strtab + def->st_name, basename(obj->path), 560 (void *)target, basename(defobj->path)); 561 562 reloc_jmpslot(where, target); 563 rlock_release(); 564 return target; 565 } 566 567 /* 568 * Error reporting function. Use it like printf. If formats the message 569 * into a buffer, and sets things up so that the next call to dlerror() 570 * will return the message. 571 */ 572 void 573 _rtld_error(const char *fmt, ...) 574 { 575 static char buf[512]; 576 va_list ap; 577 578 va_start(ap, fmt); 579 vsnprintf(buf, sizeof buf, fmt, ap); 580 error_message = buf; 581 va_end(ap); 582 } 583 584 /* 585 * Return a dynamically-allocated copy of the current error message, if any. 586 */ 587 static char * 588 errmsg_save(void) 589 { 590 return error_message == NULL ? NULL : xstrdup(error_message); 591 } 592 593 /* 594 * Restore the current error message from a copy which was previously saved 595 * by errmsg_save(). The copy is freed. 596 */ 597 static void 598 errmsg_restore(char *saved_msg) 599 { 600 if (saved_msg == NULL) 601 error_message = NULL; 602 else { 603 _rtld_error("%s", saved_msg); 604 free(saved_msg); 605 } 606 } 607 608 const char * 609 basename(const char *name) 610 { 611 const char *p = strrchr(name, '/'); 612 return p != NULL ? p + 1 : name; 613 } 614 615 static void 616 die(void) 617 { 618 const char *msg = dlerror(); 619 620 if (msg == NULL) 621 msg = "Fatal error"; 622 errx(1, "%s", msg); 623 } 624 625 /* 626 * Process a shared object's DYNAMIC section, and save the important 627 * information in its Obj_Entry structure. 628 */ 629 static void 630 digest_dynamic(Obj_Entry *obj) 631 { 632 const Elf_Dyn *dynp; 633 Needed_Entry **needed_tail = &obj->needed; 634 const Elf_Dyn *dyn_rpath = NULL; 635 int plttype = DT_REL; 636 637 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 638 switch (dynp->d_tag) { 639 640 case DT_REL: 641 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 642 break; 643 644 case DT_RELSZ: 645 obj->relsize = dynp->d_un.d_val; 646 break; 647 648 case DT_RELENT: 649 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 650 break; 651 652 case DT_JMPREL: 653 obj->pltrel = (const Elf_Rel *) 654 (obj->relocbase + dynp->d_un.d_ptr); 655 break; 656 657 case DT_PLTRELSZ: 658 obj->pltrelsize = dynp->d_un.d_val; 659 break; 660 661 case DT_RELA: 662 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 663 break; 664 665 case DT_RELASZ: 666 obj->relasize = dynp->d_un.d_val; 667 break; 668 669 case DT_RELAENT: 670 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 671 break; 672 673 case DT_PLTREL: 674 plttype = dynp->d_un.d_val; 675 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 676 break; 677 678 case DT_SYMTAB: 679 obj->symtab = (const Elf_Sym *) 680 (obj->relocbase + dynp->d_un.d_ptr); 681 break; 682 683 case DT_SYMENT: 684 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 685 break; 686 687 case DT_STRTAB: 688 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 689 break; 690 691 case DT_STRSZ: 692 obj->strsize = dynp->d_un.d_val; 693 break; 694 695 case DT_HASH: 696 { 697 const Elf_Addr *hashtab = (const Elf_Addr *) 698 (obj->relocbase + dynp->d_un.d_ptr); 699 obj->nbuckets = hashtab[0]; 700 obj->nchains = hashtab[1]; 701 obj->buckets = hashtab + 2; 702 obj->chains = obj->buckets + obj->nbuckets; 703 } 704 break; 705 706 case DT_NEEDED: 707 if (!obj->rtld) { 708 Needed_Entry *nep = NEW(Needed_Entry); 709 nep->name = dynp->d_un.d_val; 710 nep->obj = NULL; 711 nep->next = NULL; 712 713 *needed_tail = nep; 714 needed_tail = &nep->next; 715 } 716 break; 717 718 case DT_PLTGOT: 719 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 720 break; 721 722 case DT_TEXTREL: 723 obj->textrel = true; 724 break; 725 726 case DT_SYMBOLIC: 727 obj->symbolic = true; 728 break; 729 730 case DT_RPATH: 731 case DT_RUNPATH: /* XXX: process separately */ 732 /* 733 * We have to wait until later to process this, because we 734 * might not have gotten the address of the string table yet. 735 */ 736 dyn_rpath = dynp; 737 break; 738 739 case DT_SONAME: 740 /* Not used by the dynamic linker. */ 741 break; 742 743 case DT_INIT: 744 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 745 break; 746 747 case DT_FINI: 748 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 749 break; 750 751 case DT_DEBUG: 752 /* XXX - not implemented yet */ 753 dbg("Filling in DT_DEBUG entry"); 754 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 755 break; 756 757 case DT_FLAGS: 758 if (dynp->d_un.d_val & DF_ORIGIN) { 759 obj->origin_path = xmalloc(PATH_MAX); 760 if (rtld_dirname(obj->path, obj->origin_path) == -1) 761 die(); 762 } 763 if (dynp->d_un.d_val & DF_SYMBOLIC) 764 obj->symbolic = true; 765 if (dynp->d_un.d_val & DF_TEXTREL) 766 obj->textrel = true; 767 if (dynp->d_un.d_val & DF_BIND_NOW) 768 obj->bind_now = true; 769 if (dynp->d_un.d_val & DF_STATIC_TLS) 770 ; 771 break; 772 773 default: 774 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag); 775 break; 776 } 777 } 778 779 obj->traced = false; 780 781 if (plttype == DT_RELA) { 782 obj->pltrela = (const Elf_Rela *) obj->pltrel; 783 obj->pltrel = NULL; 784 obj->pltrelasize = obj->pltrelsize; 785 obj->pltrelsize = 0; 786 } 787 788 if (dyn_rpath != NULL) 789 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 790 } 791 792 /* 793 * Process a shared object's program header. This is used only for the 794 * main program, when the kernel has already loaded the main program 795 * into memory before calling the dynamic linker. It creates and 796 * returns an Obj_Entry structure. 797 */ 798 static Obj_Entry * 799 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 800 { 801 Obj_Entry *obj; 802 const Elf_Phdr *phlimit = phdr + phnum; 803 const Elf_Phdr *ph; 804 int nsegs = 0; 805 806 obj = obj_new(); 807 for (ph = phdr; ph < phlimit; ph++) { 808 switch (ph->p_type) { 809 810 case PT_PHDR: 811 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 812 _rtld_error("%s: invalid PT_PHDR", path); 813 return NULL; 814 } 815 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 816 obj->phsize = ph->p_memsz; 817 break; 818 819 case PT_INTERP: 820 obj->interp = (const char *) ph->p_vaddr; 821 break; 822 823 case PT_LOAD: 824 if (nsegs == 0) { /* First load segment */ 825 obj->vaddrbase = trunc_page(ph->p_vaddr); 826 obj->mapbase = (caddr_t) obj->vaddrbase; 827 obj->relocbase = obj->mapbase - obj->vaddrbase; 828 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 829 obj->vaddrbase; 830 } else { /* Last load segment */ 831 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 832 obj->vaddrbase; 833 } 834 nsegs++; 835 break; 836 837 case PT_DYNAMIC: 838 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 839 break; 840 841 case PT_TLS: 842 obj->tlsindex = 1; 843 obj->tlssize = ph->p_memsz; 844 obj->tlsalign = ph->p_align; 845 obj->tlsinitsize = ph->p_filesz; 846 obj->tlsinit = (void*) ph->p_vaddr; 847 break; 848 } 849 } 850 if (nsegs < 1) { 851 _rtld_error("%s: too few PT_LOAD segments", path); 852 return NULL; 853 } 854 855 obj->entry = entry; 856 return obj; 857 } 858 859 static Obj_Entry * 860 dlcheck(void *handle) 861 { 862 Obj_Entry *obj; 863 864 for (obj = obj_list; obj != NULL; obj = obj->next) 865 if (obj == (Obj_Entry *) handle) 866 break; 867 868 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { 869 _rtld_error("Invalid shared object handle %p", handle); 870 return NULL; 871 } 872 return obj; 873 } 874 875 /* 876 * If the given object is already in the donelist, return true. Otherwise 877 * add the object to the list and return false. 878 */ 879 static bool 880 donelist_check(DoneList *dlp, const Obj_Entry *obj) 881 { 882 unsigned int i; 883 884 for (i = 0; i < dlp->num_used; i++) 885 if (dlp->objs[i] == obj) 886 return true; 887 /* 888 * Our donelist allocation should always be sufficient. But if 889 * our threads locking isn't working properly, more shared objects 890 * could have been loaded since we allocated the list. That should 891 * never happen, but we'll handle it properly just in case it does. 892 */ 893 if (dlp->num_used < dlp->num_alloc) 894 dlp->objs[dlp->num_used++] = obj; 895 return false; 896 } 897 898 /* 899 * Hash function for symbol table lookup. Don't even think about changing 900 * this. It is specified by the System V ABI. 901 */ 902 unsigned long 903 elf_hash(const char *name) 904 { 905 const unsigned char *p = (const unsigned char *) name; 906 unsigned long h = 0; 907 unsigned long g; 908 909 while (*p != '\0') { 910 h = (h << 4) + *p++; 911 if ((g = h & 0xf0000000) != 0) 912 h ^= g >> 24; 913 h &= ~g; 914 } 915 return h; 916 } 917 918 /* 919 * Find the library with the given name, and return its full pathname. 920 * The returned string is dynamically allocated. Generates an error 921 * message and returns NULL if the library cannot be found. 922 * 923 * If the second argument is non-NULL, then it refers to an already- 924 * loaded shared object, whose library search path will be searched. 925 * 926 * The search order is: 927 * LD_LIBRARY_PATH 928 * rpath in the referencing file 929 * ldconfig hints 930 * /usr/lib 931 */ 932 static char * 933 find_library(const char *name, const Obj_Entry *refobj) 934 { 935 char *pathname; 936 937 if (strchr(name, '/') != NULL) { /* Hard coded pathname */ 938 if (name[0] != '/' && !trust) { 939 _rtld_error("Absolute pathname required for shared object \"%s\"", 940 name); 941 return NULL; 942 } 943 return xstrdup(name); 944 } 945 946 dbg(" Searching for \"%s\"", name); 947 948 if ((pathname = search_library_path(name, ld_library_path)) != NULL || 949 (refobj != NULL && 950 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 951 (pathname = search_library_path(name, gethints())) != NULL || 952 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 953 return pathname; 954 955 if(refobj != NULL && refobj->path != NULL) { 956 _rtld_error("Shared object \"%s\" not found, required by \"%s\"", 957 name, basename(refobj->path)); 958 } else { 959 _rtld_error("Shared object \"%s\" not found", name); 960 } 961 return NULL; 962 } 963 964 /* 965 * Given a symbol number in a referencing object, find the corresponding 966 * definition of the symbol. Returns a pointer to the symbol, or NULL if 967 * no definition was found. Returns a pointer to the Obj_Entry of the 968 * defining object via the reference parameter DEFOBJ_OUT. 969 */ 970 const Elf_Sym * 971 find_symdef(unsigned long symnum, const Obj_Entry *refobj, 972 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) 973 { 974 const Elf_Sym *ref; 975 const Elf_Sym *def; 976 const Obj_Entry *defobj; 977 const char *name; 978 unsigned long hash; 979 980 /* 981 * If we have already found this symbol, get the information from 982 * the cache. 983 */ 984 if (symnum >= refobj->nchains) 985 return NULL; /* Bad object */ 986 if (cache != NULL && cache[symnum].sym != NULL) { 987 *defobj_out = cache[symnum].obj; 988 return cache[symnum].sym; 989 } 990 991 ref = refobj->symtab + symnum; 992 name = refobj->strtab + ref->st_name; 993 hash = elf_hash(name); 994 defobj = NULL; 995 996 def = symlook_default(name, hash, refobj, &defobj, in_plt); 997 998 /* 999 * If we found no definition and the reference is weak, treat the 1000 * symbol as having the value zero. 1001 */ 1002 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 1003 def = &sym_zero; 1004 defobj = obj_main; 1005 } 1006 1007 if (def != NULL) { 1008 *defobj_out = defobj; 1009 /* Record the information in the cache to avoid subsequent lookups. */ 1010 if (cache != NULL) { 1011 cache[symnum].sym = def; 1012 cache[symnum].obj = defobj; 1013 } 1014 } else 1015 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 1016 return def; 1017 } 1018 1019 /* 1020 * Return the search path from the ldconfig hints file, reading it if 1021 * necessary. Returns NULL if there are problems with the hints file, 1022 * or if the search path there is empty. 1023 */ 1024 static const char * 1025 gethints(void) 1026 { 1027 static char *hints; 1028 1029 if (hints == NULL) { 1030 int fd; 1031 struct elfhints_hdr hdr; 1032 char *p; 1033 1034 /* Keep from trying again in case the hints file is bad. */ 1035 hints = ""; 1036 1037 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 1038 return NULL; 1039 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 1040 hdr.magic != ELFHINTS_MAGIC || 1041 hdr.version != 1) { 1042 close(fd); 1043 return NULL; 1044 } 1045 p = xmalloc(hdr.dirlistlen + 1); 1046 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 1047 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { 1048 free(p); 1049 close(fd); 1050 return NULL; 1051 } 1052 hints = p; 1053 close(fd); 1054 } 1055 return hints[0] != '\0' ? hints : NULL; 1056 } 1057 1058 static void 1059 init_dag(Obj_Entry *root) 1060 { 1061 DoneList donelist; 1062 1063 donelist_init(&donelist); 1064 init_dag1(root, root, &donelist); 1065 } 1066 1067 static void 1068 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) 1069 { 1070 const Needed_Entry *needed; 1071 1072 if (donelist_check(dlp, obj)) 1073 return; 1074 objlist_push_tail(&obj->dldags, root); 1075 objlist_push_tail(&root->dagmembers, obj); 1076 for (needed = obj->needed; needed != NULL; needed = needed->next) 1077 if (needed->obj != NULL) 1078 init_dag1(root, needed->obj, dlp); 1079 } 1080 1081 /* 1082 * Initialize the dynamic linker. The argument is the address at which 1083 * the dynamic linker has been mapped into memory. The primary task of 1084 * this function is to relocate the dynamic linker. 1085 */ 1086 static void 1087 init_rtld(caddr_t mapbase) 1088 { 1089 /* 1090 * Conjure up an Obj_Entry structure for the dynamic linker. 1091 * 1092 * The "path" member is supposed to be dynamically-allocated, but we 1093 * aren't yet initialized sufficiently to do that. Below we will 1094 * replace the static version with a dynamically-allocated copy. 1095 */ 1096 obj_rtld.path = PATH_RTLD; 1097 obj_rtld.rtld = true; 1098 obj_rtld.mapbase = mapbase; 1099 #ifdef PIC 1100 obj_rtld.relocbase = mapbase; 1101 #endif 1102 if (&_DYNAMIC != 0) { 1103 obj_rtld.dynamic = rtld_dynamic(&obj_rtld); 1104 digest_dynamic(&obj_rtld); 1105 assert(obj_rtld.needed == NULL); 1106 assert(!obj_rtld.textrel); 1107 1108 /* 1109 * Temporarily put the dynamic linker entry into the object list, so 1110 * that symbols can be found. 1111 */ 1112 obj_list = &obj_rtld; 1113 obj_tail = &obj_rtld.next; 1114 obj_count = 1; 1115 1116 relocate_objects(&obj_rtld, true); 1117 } 1118 1119 /* Make the object list empty again. */ 1120 obj_list = NULL; 1121 obj_tail = &obj_list; 1122 obj_count = 0; 1123 1124 /* Replace the path with a dynamically allocated copy. */ 1125 obj_rtld.path = xstrdup(obj_rtld.path); 1126 1127 r_debug.r_brk = r_debug_state; 1128 r_debug.r_state = RT_CONSISTENT; 1129 } 1130 1131 /* 1132 * Add the init functions from a needed object list (and its recursive 1133 * needed objects) to "list". This is not used directly; it is a helper 1134 * function for initlist_add_objects(). The write lock must be held 1135 * when this function is called. 1136 */ 1137 static void 1138 initlist_add_neededs(Needed_Entry *needed, Objlist *list) 1139 { 1140 /* Recursively process the successor needed objects. */ 1141 if (needed->next != NULL) 1142 initlist_add_neededs(needed->next, list); 1143 1144 /* Process the current needed object. */ 1145 if (needed->obj != NULL) 1146 initlist_add_objects(needed->obj, &needed->obj->next, list); 1147 } 1148 1149 /* 1150 * Scan all of the DAGs rooted in the range of objects from "obj" to 1151 * "tail" and add their init functions to "list". This recurses over 1152 * the DAGs and ensure the proper init ordering such that each object's 1153 * needed libraries are initialized before the object itself. At the 1154 * same time, this function adds the objects to the global finalization 1155 * list "list_fini" in the opposite order. The write lock must be 1156 * held when this function is called. 1157 */ 1158 static void 1159 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) 1160 { 1161 if (obj->init_done) 1162 return; 1163 obj->init_done = true; 1164 1165 /* Recursively process the successor objects. */ 1166 if (&obj->next != tail) 1167 initlist_add_objects(obj->next, tail, list); 1168 1169 /* Recursively process the needed objects. */ 1170 if (obj->needed != NULL) 1171 initlist_add_neededs(obj->needed, list); 1172 1173 /* Add the object to the init list. */ 1174 if (obj->init != NULL) 1175 objlist_push_tail(list, obj); 1176 1177 /* Add the object to the global fini list in the reverse order. */ 1178 if (obj->fini != NULL) 1179 objlist_push_head(&list_fini, obj); 1180 } 1181 1182 static bool 1183 is_exported(const Elf_Sym *def) 1184 { 1185 func_ptr_type value; 1186 const func_ptr_type *p; 1187 1188 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value); 1189 for (p = exports; *p != NULL; p++) 1190 if (*p == value) 1191 return true; 1192 return false; 1193 } 1194 1195 /* 1196 * Given a shared object, traverse its list of needed objects, and load 1197 * each of them. Returns 0 on success. Generates an error message and 1198 * returns -1 on failure. 1199 */ 1200 static int 1201 load_needed_objects(Obj_Entry *first) 1202 { 1203 Obj_Entry *obj; 1204 1205 for (obj = first; obj != NULL; obj = obj->next) { 1206 Needed_Entry *needed; 1207 1208 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1209 const char *name = obj->strtab + needed->name; 1210 char *path = find_library(name, obj); 1211 1212 needed->obj = NULL; 1213 if (path == NULL && !ld_tracing) 1214 return -1; 1215 1216 if (path) { 1217 needed->obj = load_object(path); 1218 if (needed->obj == NULL && !ld_tracing) 1219 return -1; /* XXX - cleanup */ 1220 } 1221 } 1222 } 1223 1224 return 0; 1225 } 1226 1227 static int 1228 load_preload_objects(void) 1229 { 1230 char *p = ld_preload; 1231 static const char delim[] = " \t:;"; 1232 1233 if (p == NULL) 1234 return NULL; 1235 1236 p += strspn(p, delim); 1237 while (*p != '\0') { 1238 size_t len = strcspn(p, delim); 1239 char *path; 1240 char savech; 1241 1242 savech = p[len]; 1243 p[len] = '\0'; 1244 if ((path = find_library(p, NULL)) == NULL) 1245 return -1; 1246 if (load_object(path) == NULL) 1247 return -1; /* XXX - cleanup */ 1248 p[len] = savech; 1249 p += len; 1250 p += strspn(p, delim); 1251 } 1252 return 0; 1253 } 1254 1255 /* 1256 * Returns a pointer to the Obj_Entry for the object with the given path. 1257 * Returns NULL if no matching object was found. 1258 */ 1259 static Obj_Entry * 1260 find_object(const char *path) 1261 { 1262 Obj_Entry *obj; 1263 1264 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1265 if (strcmp(obj->path, path) == 0) 1266 return(obj); 1267 } 1268 return(NULL); 1269 } 1270 1271 /* 1272 * Returns a pointer to the Obj_Entry for the object matching device and 1273 * inode of the given path. If no matching object was found, the descriptor 1274 * is returned in fd. 1275 * Returns with obj == NULL && fd == -1 on error. 1276 */ 1277 static Obj_Entry * 1278 find_object2(const char *path, int *fd, struct stat *sb) 1279 { 1280 Obj_Entry *obj; 1281 1282 if ((*fd = open(path, O_RDONLY)) == -1) { 1283 _rtld_error("Cannot open \"%s\"", path); 1284 return(NULL); 1285 } 1286 1287 if (fstat(*fd, sb) == -1) { 1288 _rtld_error("Cannot fstat \"%s\"", path); 1289 close(*fd); 1290 *fd = -1; 1291 return NULL; 1292 } 1293 1294 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1295 if (obj->ino == sb->st_ino && obj->dev == sb->st_dev) { 1296 close(*fd); 1297 break; 1298 } 1299 } 1300 1301 return(obj); 1302 } 1303 1304 /* 1305 * Load a shared object into memory, if it is not already loaded. The 1306 * argument must be a string allocated on the heap. This function assumes 1307 * responsibility for freeing it when necessary. 1308 * 1309 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1310 * on failure. 1311 */ 1312 static Obj_Entry * 1313 load_object(char *path) 1314 { 1315 Obj_Entry *obj; 1316 int fd = -1; 1317 struct stat sb; 1318 1319 obj = find_object(path); 1320 if (obj != NULL) { 1321 obj->refcount++; 1322 free(path); 1323 return(obj); 1324 } 1325 1326 obj = find_object2(path, &fd, &sb); 1327 if (obj != NULL) { 1328 obj->refcount++; 1329 free(path); 1330 return(obj); 1331 } else if (fd == -1) { 1332 free(path); 1333 return(NULL); 1334 } 1335 1336 dbg("loading \"%s\"", path); 1337 obj = map_object(fd, path, &sb); 1338 close(fd); 1339 if (obj == NULL) { 1340 free(path); 1341 return NULL; 1342 } 1343 1344 obj->path = path; 1345 digest_dynamic(obj); 1346 1347 *obj_tail = obj; 1348 obj_tail = &obj->next; 1349 obj_count++; 1350 linkmap_add(obj); /* for GDB & dlinfo() */ 1351 1352 dbg(" %p .. %p: %s", obj->mapbase, obj->mapbase + obj->mapsize - 1, 1353 obj->path); 1354 if (obj->textrel) 1355 dbg(" WARNING: %s has impure text", obj->path); 1356 1357 obj->refcount++; 1358 return obj; 1359 } 1360 1361 /* 1362 * Check for locking violations and die if one is found. 1363 */ 1364 static void 1365 lock_check(void) 1366 { 1367 int rcount, wcount; 1368 1369 rcount = lockinfo.rcount; 1370 wcount = lockinfo.wcount; 1371 assert(rcount >= 0); 1372 assert(wcount >= 0); 1373 if (wcount > 1 || (wcount != 0 && rcount != 0)) { 1374 _rtld_error("Application locking error: %d readers and %d writers" 1375 " in dynamic linker. See DLLOCKINIT(3) in manual pages.", 1376 rcount, wcount); 1377 die(); 1378 } 1379 } 1380 1381 static Obj_Entry * 1382 obj_from_addr(const void *addr) 1383 { 1384 Obj_Entry *obj; 1385 1386 for (obj = obj_list; obj != NULL; obj = obj->next) { 1387 if (addr < (void *) obj->mapbase) 1388 continue; 1389 if (addr < (void *) (obj->mapbase + obj->mapsize)) 1390 return obj; 1391 } 1392 return NULL; 1393 } 1394 1395 /* 1396 * Call the finalization functions for each of the objects in "list" 1397 * which are unreferenced. All of the objects are expected to have 1398 * non-NULL fini functions. 1399 */ 1400 static void 1401 objlist_call_fini(Objlist *list) 1402 { 1403 Objlist_Entry *elm; 1404 char *saved_msg; 1405 1406 /* 1407 * Preserve the current error message since a fini function might 1408 * call into the dynamic linker and overwrite it. 1409 */ 1410 saved_msg = errmsg_save(); 1411 STAILQ_FOREACH(elm, list, link) { 1412 if (elm->obj->refcount == 0) { 1413 dbg("calling fini function for %s", elm->obj->path); 1414 (*elm->obj->fini)(); 1415 } 1416 } 1417 errmsg_restore(saved_msg); 1418 } 1419 1420 /* 1421 * Call the initialization functions for each of the objects in 1422 * "list". All of the objects are expected to have non-NULL init 1423 * functions. 1424 */ 1425 static void 1426 objlist_call_init(Objlist *list) 1427 { 1428 Objlist_Entry *elm; 1429 char *saved_msg; 1430 1431 /* 1432 * Preserve the current error message since an init function might 1433 * call into the dynamic linker and overwrite it. 1434 */ 1435 saved_msg = errmsg_save(); 1436 STAILQ_FOREACH(elm, list, link) { 1437 dbg("calling init function for %s", elm->obj->path); 1438 (*elm->obj->init)(); 1439 } 1440 errmsg_restore(saved_msg); 1441 } 1442 1443 static void 1444 objlist_clear(Objlist *list) 1445 { 1446 Objlist_Entry *elm; 1447 1448 while (!STAILQ_EMPTY(list)) { 1449 elm = STAILQ_FIRST(list); 1450 STAILQ_REMOVE_HEAD(list, link); 1451 free(elm); 1452 } 1453 } 1454 1455 static Objlist_Entry * 1456 objlist_find(Objlist *list, const Obj_Entry *obj) 1457 { 1458 Objlist_Entry *elm; 1459 1460 STAILQ_FOREACH(elm, list, link) 1461 if (elm->obj == obj) 1462 return elm; 1463 return NULL; 1464 } 1465 1466 static void 1467 objlist_init(Objlist *list) 1468 { 1469 STAILQ_INIT(list); 1470 } 1471 1472 static void 1473 objlist_push_head(Objlist *list, Obj_Entry *obj) 1474 { 1475 Objlist_Entry *elm; 1476 1477 elm = NEW(Objlist_Entry); 1478 elm->obj = obj; 1479 STAILQ_INSERT_HEAD(list, elm, link); 1480 } 1481 1482 static void 1483 objlist_push_tail(Objlist *list, Obj_Entry *obj) 1484 { 1485 Objlist_Entry *elm; 1486 1487 elm = NEW(Objlist_Entry); 1488 elm->obj = obj; 1489 STAILQ_INSERT_TAIL(list, elm, link); 1490 } 1491 1492 static void 1493 objlist_remove(Objlist *list, Obj_Entry *obj) 1494 { 1495 Objlist_Entry *elm; 1496 1497 if ((elm = objlist_find(list, obj)) != NULL) { 1498 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1499 free(elm); 1500 } 1501 } 1502 1503 /* 1504 * Remove all of the unreferenced objects from "list". 1505 */ 1506 static void 1507 objlist_remove_unref(Objlist *list) 1508 { 1509 Objlist newlist; 1510 Objlist_Entry *elm; 1511 1512 STAILQ_INIT(&newlist); 1513 while (!STAILQ_EMPTY(list)) { 1514 elm = STAILQ_FIRST(list); 1515 STAILQ_REMOVE_HEAD(list, link); 1516 if (elm->obj->refcount == 0) 1517 free(elm); 1518 else 1519 STAILQ_INSERT_TAIL(&newlist, elm, link); 1520 } 1521 *list = newlist; 1522 } 1523 1524 /* 1525 * Relocate newly-loaded shared objects. The argument is a pointer to 1526 * the Obj_Entry for the first such object. All objects from the first 1527 * to the end of the list of objects are relocated. Returns 0 on success, 1528 * or -1 on failure. 1529 */ 1530 static int 1531 relocate_objects(Obj_Entry *first, bool bind_now) 1532 { 1533 Obj_Entry *obj; 1534 1535 for (obj = first; obj != NULL; obj = obj->next) { 1536 if (obj != &obj_rtld) 1537 dbg("relocating \"%s\"", obj->path); 1538 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1539 obj->symtab == NULL || obj->strtab == NULL) { 1540 _rtld_error("%s: Shared object has no run-time symbol table", 1541 obj->path); 1542 return -1; 1543 } 1544 1545 if (obj->textrel) { 1546 /* There are relocations to the write-protected text segment. */ 1547 if (mprotect(obj->mapbase, obj->textsize, 1548 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1549 _rtld_error("%s: Cannot write-enable text segment: %s", 1550 obj->path, strerror(errno)); 1551 return -1; 1552 } 1553 } 1554 1555 /* Process the non-PLT relocations. */ 1556 if (reloc_non_plt(obj, &obj_rtld)) 1557 return -1; 1558 1559 /* 1560 * Reprotect the text segment. Make sure it is included in the 1561 * core dump since we modified it. This unfortunately causes the 1562 * entire text segment to core-out but we don't have much of a 1563 * choice. We could try to only reenable core dumps on pages 1564 * in which relocations occured but that is likely most of the text 1565 * pages anyway, and even that would not work because the rest of 1566 * the text pages would wind up as a read-only OBJT_DEFAULT object 1567 * (created due to our modifications) backed by the original OBJT_VNODE 1568 * object, and the ELF coredump code is currently only able to dump 1569 * vnode records for pure vnode-backed mappings, not vnode backings 1570 * to memory objects. 1571 */ 1572 if (obj->textrel) { 1573 madvise(obj->mapbase, obj->textsize, MADV_CORE); 1574 if (mprotect(obj->mapbase, obj->textsize, 1575 PROT_READ|PROT_EXEC) == -1) { 1576 _rtld_error("%s: Cannot write-protect text segment: %s", 1577 obj->path, strerror(errno)); 1578 return -1; 1579 } 1580 } 1581 1582 /* Process the PLT relocations. */ 1583 if (reloc_plt(obj) == -1) 1584 return -1; 1585 /* Relocate the jump slots if we are doing immediate binding. */ 1586 if (obj->bind_now || bind_now) 1587 if (reloc_jmpslots(obj) == -1) 1588 return -1; 1589 1590 1591 /* 1592 * Set up the magic number and version in the Obj_Entry. These 1593 * were checked in the crt1.o from the original ElfKit, so we 1594 * set them for backward compatibility. 1595 */ 1596 obj->magic = RTLD_MAGIC; 1597 obj->version = RTLD_VERSION; 1598 1599 /* Set the special PLT or GOT entries. */ 1600 init_pltgot(obj); 1601 } 1602 1603 return 0; 1604 } 1605 1606 /* 1607 * Cleanup procedure. It will be called (by the atexit mechanism) just 1608 * before the process exits. 1609 */ 1610 static void 1611 rtld_exit(void) 1612 { 1613 Obj_Entry *obj; 1614 1615 dbg("rtld_exit()"); 1616 /* Clear all the reference counts so the fini functions will be called. */ 1617 for (obj = obj_list; obj != NULL; obj = obj->next) 1618 obj->refcount = 0; 1619 objlist_call_fini(&list_fini); 1620 /* No need to remove the items from the list, since we are exiting. */ 1621 } 1622 1623 static void * 1624 path_enumerate(const char *path, path_enum_proc callback, void *arg) 1625 { 1626 if (path == NULL) 1627 return (NULL); 1628 1629 path += strspn(path, ":;"); 1630 while (*path != '\0') { 1631 size_t len; 1632 char *res; 1633 1634 len = strcspn(path, ":;"); 1635 res = callback(path, len, arg); 1636 1637 if (res != NULL) 1638 return (res); 1639 1640 path += len; 1641 path += strspn(path, ":;"); 1642 } 1643 1644 return (NULL); 1645 } 1646 1647 struct try_library_args { 1648 const char *name; 1649 size_t namelen; 1650 char *buffer; 1651 size_t buflen; 1652 }; 1653 1654 static void * 1655 try_library_path(const char *dir, size_t dirlen, void *param) 1656 { 1657 struct try_library_args *arg; 1658 1659 arg = param; 1660 if (*dir == '/' || trust) { 1661 char *pathname; 1662 1663 if (dirlen + 1 + arg->namelen + 1 > arg->buflen) 1664 return (NULL); 1665 1666 pathname = arg->buffer; 1667 strncpy(pathname, dir, dirlen); 1668 pathname[dirlen] = '/'; 1669 strcpy(pathname + dirlen + 1, arg->name); 1670 1671 dbg(" Trying \"%s\"", pathname); 1672 if (access(pathname, F_OK) == 0) { /* We found it */ 1673 pathname = xmalloc(dirlen + 1 + arg->namelen + 1); 1674 strcpy(pathname, arg->buffer); 1675 return (pathname); 1676 } 1677 } 1678 return (NULL); 1679 } 1680 1681 static char * 1682 search_library_path(const char *name, const char *path) 1683 { 1684 char *p; 1685 struct try_library_args arg; 1686 1687 if (path == NULL) 1688 return NULL; 1689 1690 arg.name = name; 1691 arg.namelen = strlen(name); 1692 arg.buffer = xmalloc(PATH_MAX); 1693 arg.buflen = PATH_MAX; 1694 1695 p = path_enumerate(path, try_library_path, &arg); 1696 1697 free(arg.buffer); 1698 1699 return (p); 1700 } 1701 1702 int 1703 dlclose(void *handle) 1704 { 1705 Obj_Entry *root; 1706 1707 wlock_acquire(); 1708 root = dlcheck(handle); 1709 if (root == NULL) { 1710 wlock_release(); 1711 return -1; 1712 } 1713 1714 /* Unreference the object and its dependencies. */ 1715 root->dl_refcount--; 1716 unref_dag(root); 1717 1718 if (root->refcount == 0) { 1719 /* 1720 * The object is no longer referenced, so we must unload it. 1721 * First, call the fini functions with no locks held. 1722 */ 1723 wlock_release(); 1724 objlist_call_fini(&list_fini); 1725 wlock_acquire(); 1726 objlist_remove_unref(&list_fini); 1727 1728 /* Finish cleaning up the newly-unreferenced objects. */ 1729 GDB_STATE(RT_DELETE,&root->linkmap); 1730 unload_object(root); 1731 GDB_STATE(RT_CONSISTENT,NULL); 1732 } 1733 wlock_release(); 1734 return 0; 1735 } 1736 1737 const char * 1738 dlerror(void) 1739 { 1740 char *msg = error_message; 1741 error_message = NULL; 1742 return msg; 1743 } 1744 1745 void * 1746 dlopen(const char *name, int mode) 1747 { 1748 Obj_Entry **old_obj_tail; 1749 Obj_Entry *obj; 1750 Objlist initlist; 1751 int result; 1752 1753 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1"; 1754 if (ld_tracing != NULL) 1755 environ = (char **)*get_program_var_addr("environ"); 1756 1757 objlist_init(&initlist); 1758 1759 wlock_acquire(); 1760 GDB_STATE(RT_ADD,NULL); 1761 1762 old_obj_tail = obj_tail; 1763 obj = NULL; 1764 if (name == NULL) { 1765 obj = obj_main; 1766 obj->refcount++; 1767 } else { 1768 char *path = find_library(name, obj_main); 1769 if (path != NULL) 1770 obj = load_object(path); 1771 } 1772 1773 if (obj) { 1774 obj->dl_refcount++; 1775 if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL) 1776 objlist_push_tail(&list_global, obj); 1777 mode &= RTLD_MODEMASK; 1778 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1779 assert(*old_obj_tail == obj); 1780 1781 result = load_needed_objects(obj); 1782 if (result != -1 && ld_tracing) 1783 goto trace; 1784 1785 if (result == -1 || 1786 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) { 1787 obj->dl_refcount--; 1788 unref_dag(obj); 1789 if (obj->refcount == 0) 1790 unload_object(obj); 1791 obj = NULL; 1792 } else { 1793 /* Make list of init functions to call. */ 1794 initlist_add_objects(obj, &obj->next, &initlist); 1795 } 1796 } else if (ld_tracing) 1797 goto trace; 1798 } 1799 1800 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); 1801 1802 /* Call the init functions with no locks held. */ 1803 wlock_release(); 1804 objlist_call_init(&initlist); 1805 wlock_acquire(); 1806 objlist_clear(&initlist); 1807 wlock_release(); 1808 return obj; 1809 trace: 1810 trace_loaded_objects(obj); 1811 wlock_release(); 1812 exit(0); 1813 } 1814 1815 void * 1816 dlsym(void *handle, const char *name) 1817 { 1818 const Obj_Entry *obj; 1819 unsigned long hash; 1820 const Elf_Sym *def; 1821 const Obj_Entry *defobj; 1822 1823 hash = elf_hash(name); 1824 def = NULL; 1825 defobj = NULL; 1826 1827 rlock_acquire(); 1828 if (handle == NULL || handle == RTLD_NEXT || 1829 handle == RTLD_DEFAULT || handle == RTLD_SELF) { 1830 void *retaddr; 1831 1832 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1833 if ((obj = obj_from_addr(retaddr)) == NULL) { 1834 _rtld_error("Cannot determine caller's shared object"); 1835 rlock_release(); 1836 return NULL; 1837 } 1838 if (handle == NULL) { /* Just the caller's shared object. */ 1839 def = symlook_obj(name, hash, obj, true); 1840 defobj = obj; 1841 } else if (handle == RTLD_NEXT || /* Objects after caller's */ 1842 handle == RTLD_SELF) { /* ... caller included */ 1843 if (handle == RTLD_NEXT) 1844 obj = obj->next; 1845 for (; obj != NULL; obj = obj->next) { 1846 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1847 defobj = obj; 1848 break; 1849 } 1850 } 1851 } else { 1852 assert(handle == RTLD_DEFAULT); 1853 def = symlook_default(name, hash, obj, &defobj, true); 1854 } 1855 } else { 1856 DoneList donelist; 1857 1858 if ((obj = dlcheck(handle)) == NULL) { 1859 rlock_release(); 1860 return NULL; 1861 } 1862 1863 donelist_init(&donelist); 1864 if (obj->mainprog) { 1865 /* Search main program and all libraries loaded by it. */ 1866 def = symlook_list(name, hash, &list_main, &defobj, true, 1867 &donelist); 1868 } else { 1869 def = symlook_list(name, hash, &(obj->dagmembers), &defobj, true, 1870 &donelist); 1871 } 1872 } 1873 1874 if (def != NULL) { 1875 rlock_release(); 1876 return defobj->relocbase + def->st_value; 1877 } 1878 1879 _rtld_error("Undefined symbol \"%s\"", name); 1880 rlock_release(); 1881 return NULL; 1882 } 1883 1884 int 1885 dladdr(const void *addr, Dl_info *info) 1886 { 1887 const Obj_Entry *obj; 1888 const Elf_Sym *def; 1889 void *symbol_addr; 1890 unsigned long symoffset; 1891 1892 rlock_acquire(); 1893 obj = obj_from_addr(addr); 1894 if (obj == NULL) { 1895 _rtld_error("No shared object contains address"); 1896 rlock_release(); 1897 return 0; 1898 } 1899 info->dli_fname = obj->path; 1900 info->dli_fbase = obj->mapbase; 1901 info->dli_saddr = (void *)0; 1902 info->dli_sname = NULL; 1903 1904 /* 1905 * Walk the symbol list looking for the symbol whose address is 1906 * closest to the address sent in. 1907 */ 1908 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1909 def = obj->symtab + symoffset; 1910 1911 /* 1912 * For skip the symbol if st_shndx is either SHN_UNDEF or 1913 * SHN_COMMON. 1914 */ 1915 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1916 continue; 1917 1918 /* 1919 * If the symbol is greater than the specified address, or if it 1920 * is further away from addr than the current nearest symbol, 1921 * then reject it. 1922 */ 1923 symbol_addr = obj->relocbase + def->st_value; 1924 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1925 continue; 1926 1927 /* Update our idea of the nearest symbol. */ 1928 info->dli_sname = obj->strtab + def->st_name; 1929 info->dli_saddr = symbol_addr; 1930 1931 /* Exact match? */ 1932 if (info->dli_saddr == addr) 1933 break; 1934 } 1935 rlock_release(); 1936 return 1; 1937 } 1938 1939 int 1940 dlinfo(void *handle, int request, void *p) 1941 { 1942 const Obj_Entry *obj; 1943 int error; 1944 1945 rlock_acquire(); 1946 1947 if (handle == NULL || handle == RTLD_SELF) { 1948 void *retaddr; 1949 1950 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1951 if ((obj = obj_from_addr(retaddr)) == NULL) 1952 _rtld_error("Cannot determine caller's shared object"); 1953 } else 1954 obj = dlcheck(handle); 1955 1956 if (obj == NULL) { 1957 rlock_release(); 1958 return (-1); 1959 } 1960 1961 error = 0; 1962 switch (request) { 1963 case RTLD_DI_LINKMAP: 1964 *((struct link_map const **)p) = &obj->linkmap; 1965 break; 1966 case RTLD_DI_ORIGIN: 1967 error = rtld_dirname(obj->path, p); 1968 break; 1969 1970 case RTLD_DI_SERINFOSIZE: 1971 case RTLD_DI_SERINFO: 1972 error = do_search_info(obj, request, (struct dl_serinfo *)p); 1973 break; 1974 1975 default: 1976 _rtld_error("Invalid request %d passed to dlinfo()", request); 1977 error = -1; 1978 } 1979 1980 rlock_release(); 1981 1982 return (error); 1983 } 1984 1985 struct fill_search_info_args { 1986 int request; 1987 unsigned int flags; 1988 Dl_serinfo *serinfo; 1989 Dl_serpath *serpath; 1990 char *strspace; 1991 }; 1992 1993 static void * 1994 fill_search_info(const char *dir, size_t dirlen, void *param) 1995 { 1996 struct fill_search_info_args *arg; 1997 1998 arg = param; 1999 2000 if (arg->request == RTLD_DI_SERINFOSIZE) { 2001 arg->serinfo->dls_cnt ++; 2002 arg->serinfo->dls_size += dirlen + 1; 2003 } else { 2004 struct dl_serpath *s_entry; 2005 2006 s_entry = arg->serpath; 2007 s_entry->dls_name = arg->strspace; 2008 s_entry->dls_flags = arg->flags; 2009 2010 strncpy(arg->strspace, dir, dirlen); 2011 arg->strspace[dirlen] = '\0'; 2012 2013 arg->strspace += dirlen + 1; 2014 arg->serpath++; 2015 } 2016 2017 return (NULL); 2018 } 2019 2020 static int 2021 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info) 2022 { 2023 struct dl_serinfo _info; 2024 struct fill_search_info_args args; 2025 2026 args.request = RTLD_DI_SERINFOSIZE; 2027 args.serinfo = &_info; 2028 2029 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath); 2030 _info.dls_cnt = 0; 2031 2032 path_enumerate(ld_library_path, fill_search_info, &args); 2033 path_enumerate(obj->rpath, fill_search_info, &args); 2034 path_enumerate(gethints(), fill_search_info, &args); 2035 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args); 2036 2037 2038 if (request == RTLD_DI_SERINFOSIZE) { 2039 info->dls_size = _info.dls_size; 2040 info->dls_cnt = _info.dls_cnt; 2041 return (0); 2042 } 2043 2044 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) { 2045 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()"); 2046 return (-1); 2047 } 2048 2049 args.request = RTLD_DI_SERINFO; 2050 args.serinfo = info; 2051 args.serpath = &info->dls_serpath[0]; 2052 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt]; 2053 2054 args.flags = LA_SER_LIBPATH; 2055 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL) 2056 return (-1); 2057 2058 args.flags = LA_SER_RUNPATH; 2059 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL) 2060 return (-1); 2061 2062 args.flags = LA_SER_CONFIG; 2063 if (path_enumerate(gethints(), fill_search_info, &args) != NULL) 2064 return (-1); 2065 2066 args.flags = LA_SER_DEFAULT; 2067 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL) 2068 return (-1); 2069 return (0); 2070 } 2071 2072 static int 2073 rtld_dirname(const char *path, char *bname) 2074 { 2075 const char *endp; 2076 2077 /* Empty or NULL string gets treated as "." */ 2078 if (path == NULL || *path == '\0') { 2079 bname[0] = '.'; 2080 bname[1] = '\0'; 2081 return (0); 2082 } 2083 2084 /* Strip trailing slashes */ 2085 endp = path + strlen(path) - 1; 2086 while (endp > path && *endp == '/') 2087 endp--; 2088 2089 /* Find the start of the dir */ 2090 while (endp > path && *endp != '/') 2091 endp--; 2092 2093 /* Either the dir is "/" or there are no slashes */ 2094 if (endp == path) { 2095 bname[0] = *endp == '/' ? '/' : '.'; 2096 bname[1] = '\0'; 2097 return (0); 2098 } else { 2099 do { 2100 endp--; 2101 } while (endp > path && *endp == '/'); 2102 } 2103 2104 if (endp - path + 2 > PATH_MAX) 2105 { 2106 _rtld_error("Filename is too long: %s", path); 2107 return(-1); 2108 } 2109 2110 strncpy(bname, path, endp - path + 1); 2111 bname[endp - path + 1] = '\0'; 2112 return (0); 2113 } 2114 2115 static void 2116 linkmap_add(Obj_Entry *obj) 2117 { 2118 struct link_map *l = &obj->linkmap; 2119 struct link_map *prev; 2120 2121 obj->linkmap.l_name = obj->path; 2122 obj->linkmap.l_addr = obj->mapbase; 2123 obj->linkmap.l_ld = obj->dynamic; 2124 #ifdef __mips__ 2125 /* GDB needs load offset on MIPS to use the symbols */ 2126 obj->linkmap.l_offs = obj->relocbase; 2127 #endif 2128 2129 if (r_debug.r_map == NULL) { 2130 r_debug.r_map = l; 2131 return; 2132 } 2133 2134 /* 2135 * Scan to the end of the list, but not past the entry for the 2136 * dynamic linker, which we want to keep at the very end. 2137 */ 2138 for (prev = r_debug.r_map; 2139 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 2140 prev = prev->l_next) 2141 ; 2142 2143 /* Link in the new entry. */ 2144 l->l_prev = prev; 2145 l->l_next = prev->l_next; 2146 if (l->l_next != NULL) 2147 l->l_next->l_prev = l; 2148 prev->l_next = l; 2149 } 2150 2151 static void 2152 linkmap_delete(Obj_Entry *obj) 2153 { 2154 struct link_map *l = &obj->linkmap; 2155 2156 if (l->l_prev == NULL) { 2157 if ((r_debug.r_map = l->l_next) != NULL) 2158 l->l_next->l_prev = NULL; 2159 return; 2160 } 2161 2162 if ((l->l_prev->l_next = l->l_next) != NULL) 2163 l->l_next->l_prev = l->l_prev; 2164 } 2165 2166 /* 2167 * Function for the debugger to set a breakpoint on to gain control. 2168 * 2169 * The two parameters allow the debugger to easily find and determine 2170 * what the runtime loader is doing and to whom it is doing it. 2171 * 2172 * When the loadhook trap is hit (r_debug_state, set at program 2173 * initialization), the arguments can be found on the stack: 2174 * 2175 * +8 struct link_map *m 2176 * +4 struct r_debug *rd 2177 * +0 RetAddr 2178 */ 2179 void 2180 r_debug_state(struct r_debug* rd, struct link_map *m) 2181 { 2182 } 2183 2184 /* 2185 * Get address of the pointer variable in the main program. 2186 */ 2187 static const void ** 2188 get_program_var_addr(const char *name) 2189 { 2190 const Obj_Entry *obj; 2191 unsigned long hash; 2192 2193 hash = elf_hash(name); 2194 for (obj = obj_main; obj != NULL; obj = obj->next) { 2195 const Elf_Sym *def; 2196 2197 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 2198 const void **addr; 2199 2200 addr = (const void **)(obj->relocbase + def->st_value); 2201 return addr; 2202 } 2203 } 2204 return NULL; 2205 } 2206 2207 /* 2208 * Set a pointer variable in the main program to the given value. This 2209 * is used to set key variables such as "environ" before any of the 2210 * init functions are called. 2211 */ 2212 static void 2213 set_program_var(const char *name, const void *value) 2214 { 2215 const void **addr; 2216 2217 if ((addr = get_program_var_addr(name)) != NULL) { 2218 dbg("\"%s\": *%p <-- %p", name, addr, value); 2219 *addr = value; 2220 } 2221 } 2222 2223 /* 2224 * This is a special version of getenv which is far more efficient 2225 * at finding LD_ environment vars. 2226 */ 2227 static 2228 const char * 2229 _getenv_ld(const char *id) 2230 { 2231 const char *envp; 2232 int i, j; 2233 int idlen = strlen(id); 2234 2235 if (ld_index == LD_ARY_CACHE) 2236 return(getenv(id)); 2237 if (ld_index == 0) { 2238 for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) { 2239 if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_') 2240 ld_ary[j++] = envp; 2241 } 2242 if (j == 0) 2243 ld_ary[j++] = ""; 2244 ld_index = j; 2245 } 2246 for (i = ld_index - 1; i >= 0; --i) { 2247 if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=') 2248 return(ld_ary[i] + idlen + 1); 2249 } 2250 return(NULL); 2251 } 2252 2253 /* 2254 * Given a symbol name in a referencing object, find the corresponding 2255 * definition of the symbol. Returns a pointer to the symbol, or NULL if 2256 * no definition was found. Returns a pointer to the Obj_Entry of the 2257 * defining object via the reference parameter DEFOBJ_OUT. 2258 */ 2259 static const Elf_Sym * 2260 symlook_default(const char *name, unsigned long hash, 2261 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) 2262 { 2263 DoneList donelist; 2264 const Elf_Sym *def; 2265 const Elf_Sym *symp; 2266 const Obj_Entry *obj; 2267 const Obj_Entry *defobj; 2268 const Objlist_Entry *elm; 2269 def = NULL; 2270 defobj = NULL; 2271 donelist_init(&donelist); 2272 2273 /* Look first in the referencing object if linked symbolically. */ 2274 if (refobj->symbolic && !donelist_check(&donelist, refobj)) { 2275 symp = symlook_obj(name, hash, refobj, in_plt); 2276 if (symp != NULL) { 2277 def = symp; 2278 defobj = refobj; 2279 } 2280 } 2281 2282 /* Search all objects loaded at program start up. */ 2283 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2284 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); 2285 if (symp != NULL && 2286 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2287 def = symp; 2288 defobj = obj; 2289 } 2290 } 2291 2292 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */ 2293 STAILQ_FOREACH(elm, &list_global, link) { 2294 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2295 break; 2296 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2297 &donelist); 2298 if (symp != NULL && 2299 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2300 def = symp; 2301 defobj = obj; 2302 } 2303 } 2304 2305 /* Search all dlopened DAGs containing the referencing object. */ 2306 STAILQ_FOREACH(elm, &refobj->dldags, link) { 2307 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2308 break; 2309 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2310 &donelist); 2311 if (symp != NULL && 2312 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2313 def = symp; 2314 defobj = obj; 2315 } 2316 } 2317 2318 /* 2319 * Search the dynamic linker itself, and possibly resolve the 2320 * symbol from there. This is how the application links to 2321 * dynamic linker services such as dlopen. Only the values listed 2322 * in the "exports" array can be resolved from the dynamic linker. 2323 */ 2324 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2325 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 2326 if (symp != NULL && is_exported(symp)) { 2327 def = symp; 2328 defobj = &obj_rtld; 2329 } 2330 } 2331 2332 if (def != NULL) 2333 *defobj_out = defobj; 2334 return def; 2335 } 2336 2337 static const Elf_Sym * 2338 symlook_list(const char *name, unsigned long hash, const Objlist *objlist, 2339 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 2340 { 2341 const Elf_Sym *symp; 2342 const Elf_Sym *def; 2343 const Obj_Entry *defobj; 2344 const Objlist_Entry *elm; 2345 2346 def = NULL; 2347 defobj = NULL; 2348 STAILQ_FOREACH(elm, objlist, link) { 2349 if (donelist_check(dlp, elm->obj)) 2350 continue; 2351 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 2352 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 2353 def = symp; 2354 defobj = elm->obj; 2355 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 2356 break; 2357 } 2358 } 2359 } 2360 if (def != NULL) 2361 *defobj_out = defobj; 2362 return def; 2363 } 2364 2365 /* 2366 * Search the symbol table of a single shared object for a symbol of 2367 * the given name. Returns a pointer to the symbol, or NULL if no 2368 * definition was found. 2369 * 2370 * The symbol's hash value is passed in for efficiency reasons; that 2371 * eliminates many recomputations of the hash value. 2372 */ 2373 const Elf_Sym * 2374 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 2375 bool in_plt) 2376 { 2377 if (obj->buckets != NULL) { 2378 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 2379 2380 while (symnum != STN_UNDEF) { 2381 const Elf_Sym *symp; 2382 const char *strp; 2383 2384 if (symnum >= obj->nchains) 2385 return NULL; /* Bad object */ 2386 symp = obj->symtab + symnum; 2387 strp = obj->strtab + symp->st_name; 2388 2389 if (name[0] == strp[0] && strcmp(name, strp) == 0) 2390 return symp->st_shndx != SHN_UNDEF || 2391 (!in_plt && symp->st_value != 0 && 2392 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 2393 2394 symnum = obj->chains[symnum]; 2395 } 2396 } 2397 return NULL; 2398 } 2399 2400 static void 2401 trace_loaded_objects(Obj_Entry *obj) 2402 { 2403 const char *fmt1, *fmt2, *fmt, *main_local; 2404 int c; 2405 2406 if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 2407 main_local = ""; 2408 2409 if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 2410 fmt1 = "\t%o => %p (%x)\n"; 2411 2412 if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 2413 fmt2 = "\t%o (%x)\n"; 2414 2415 for (; obj; obj = obj->next) { 2416 Needed_Entry *needed; 2417 char *name, *path; 2418 bool is_lib; 2419 2420 for (needed = obj->needed; needed; needed = needed->next) { 2421 if (needed->obj != NULL) { 2422 if (needed->obj->traced) 2423 continue; 2424 needed->obj->traced = true; 2425 path = needed->obj->path; 2426 } else 2427 path = "not found"; 2428 2429 name = (char *)obj->strtab + needed->name; 2430 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 2431 2432 fmt = is_lib ? fmt1 : fmt2; 2433 while ((c = *fmt++) != '\0') { 2434 switch (c) { 2435 default: 2436 putchar(c); 2437 continue; 2438 case '\\': 2439 switch (c = *fmt) { 2440 case '\0': 2441 continue; 2442 case 'n': 2443 putchar('\n'); 2444 break; 2445 case 't': 2446 putchar('\t'); 2447 break; 2448 } 2449 break; 2450 case '%': 2451 switch (c = *fmt) { 2452 case '\0': 2453 continue; 2454 case '%': 2455 default: 2456 putchar(c); 2457 break; 2458 case 'A': 2459 printf("%s", main_local); 2460 break; 2461 case 'a': 2462 printf("%s", obj_main->path); 2463 break; 2464 case 'o': 2465 printf("%s", name); 2466 break; 2467 #if 0 2468 case 'm': 2469 printf("%d", sodp->sod_major); 2470 break; 2471 case 'n': 2472 printf("%d", sodp->sod_minor); 2473 break; 2474 #endif 2475 case 'p': 2476 printf("%s", path); 2477 break; 2478 case 'x': 2479 printf("%p", needed->obj ? needed->obj->mapbase : 0); 2480 break; 2481 } 2482 break; 2483 } 2484 ++fmt; 2485 } 2486 } 2487 } 2488 } 2489 2490 /* 2491 * Unload a dlopened object and its dependencies from memory and from 2492 * our data structures. It is assumed that the DAG rooted in the 2493 * object has already been unreferenced, and that the object has a 2494 * reference count of 0. 2495 */ 2496 static void 2497 unload_object(Obj_Entry *root) 2498 { 2499 Obj_Entry *obj; 2500 Obj_Entry **linkp; 2501 2502 assert(root->refcount == 0); 2503 2504 /* 2505 * Pass over the DAG removing unreferenced objects from 2506 * appropriate lists. 2507 */ 2508 unlink_object(root); 2509 2510 /* Unmap all objects that are no longer referenced. */ 2511 linkp = &obj_list->next; 2512 while ((obj = *linkp) != NULL) { 2513 if (obj->refcount == 0) { 2514 dbg("unloading \"%s\"", obj->path); 2515 munmap(obj->mapbase, obj->mapsize); 2516 linkmap_delete(obj); 2517 *linkp = obj->next; 2518 obj_count--; 2519 obj_free(obj); 2520 } else 2521 linkp = &obj->next; 2522 } 2523 obj_tail = linkp; 2524 } 2525 2526 static void 2527 unlink_object(Obj_Entry *root) 2528 { 2529 const Needed_Entry *needed; 2530 Objlist_Entry *elm; 2531 2532 if (root->refcount == 0) { 2533 /* Remove the object from the RTLD_GLOBAL list. */ 2534 objlist_remove(&list_global, root); 2535 2536 /* Remove the object from all objects' DAG lists. */ 2537 STAILQ_FOREACH(elm, &root->dagmembers , link) 2538 objlist_remove(&elm->obj->dldags, root); 2539 } 2540 2541 for (needed = root->needed; needed != NULL; needed = needed->next) 2542 if (needed->obj != NULL) 2543 unlink_object(needed->obj); 2544 } 2545 2546 static void 2547 unref_dag(Obj_Entry *root) 2548 { 2549 const Needed_Entry *needed; 2550 2551 if (root->refcount == 0) 2552 return; 2553 root->refcount--; 2554 if (root->refcount == 0) 2555 for (needed = root->needed; needed != NULL; needed = needed->next) 2556 if (needed->obj != NULL) 2557 unref_dag(needed->obj); 2558 } 2559 2560 /* 2561 * Common code for MD __tls_get_addr(). 2562 */ 2563 void * 2564 tls_get_addr_common(void **dtvp, int index, size_t offset) 2565 { 2566 Elf_Addr* dtv = *dtvp; 2567 2568 /* Check dtv generation in case new modules have arrived */ 2569 if (dtv[0] != tls_dtv_generation) { 2570 Elf_Addr* newdtv; 2571 int to_copy; 2572 2573 wlock_acquire(); 2574 2575 newdtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr)); 2576 to_copy = dtv[1]; 2577 if (to_copy > tls_max_index) 2578 to_copy = tls_max_index; 2579 memcpy(&newdtv[2], &dtv[2], to_copy * sizeof(Elf_Addr)); 2580 newdtv[0] = tls_dtv_generation; 2581 newdtv[1] = tls_max_index; 2582 free(dtv); 2583 *dtvp = newdtv; 2584 2585 wlock_release(); 2586 } 2587 2588 /* Dynamically allocate module TLS if necessary */ 2589 if (!dtv[index + 1]) { 2590 /* XXX 2591 * here we should avoid to be re-entered by signal handler 2592 * code, I assume wlock_acquire will masked all signals, 2593 * otherwise there is race and dead lock thread itself. 2594 */ 2595 wlock_acquire(); 2596 if (!dtv[index + 1]) 2597 dtv[index + 1] = (Elf_Addr)allocate_module_tls(index); 2598 wlock_release(); 2599 } 2600 2601 return (void*) (dtv[index + 1] + offset); 2602 } 2603 2604 #if defined(RTLD_STATIC_TLS_VARIANT_II) 2605 2606 /* 2607 * Allocate the static TLS area. Return a pointer to the TCB. The 2608 * static area is based on negative offsets relative to the tcb. 2609 * 2610 * The TCB contains an errno pointer for the system call layer, but because 2611 * we are the RTLD we really have no idea how the caller was compiled so 2612 * the information has to be passed in. errno can either be: 2613 * 2614 * type 0 errno is a simple non-TLS global pointer. 2615 * (special case for e.g. libc_rtld) 2616 * type 1 errno accessed by GOT entry (dynamically linked programs) 2617 * type 2 errno accessed by %gs:OFFSET (statically linked programs) 2618 */ 2619 struct tls_tcb * 2620 allocate_tls(Obj_Entry *objs) 2621 { 2622 Obj_Entry *obj; 2623 size_t data_size; 2624 size_t dtv_size; 2625 struct tls_tcb *tcb; 2626 Elf_Addr *dtv; 2627 Elf_Addr addr; 2628 2629 /* 2630 * Allocate the new TCB. static TLS storage is placed just before the 2631 * TCB to support the %gs:OFFSET (negative offset) model. 2632 */ 2633 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) & 2634 ~RTLD_STATIC_TLS_ALIGN_MASK; 2635 tcb = malloc(data_size + sizeof(*tcb)); 2636 tcb = (void *)((char *)tcb + data_size); /* actual tcb location */ 2637 2638 dtv_size = (tls_max_index + 2) * sizeof(Elf_Addr); 2639 dtv = malloc(dtv_size); 2640 bzero(dtv, dtv_size); 2641 2642 #ifdef RTLD_TCB_HAS_SELF_POINTER 2643 tcb->tcb_self = tcb; 2644 #endif 2645 tcb->tcb_dtv = dtv; 2646 tcb->tcb_pthread = NULL; 2647 2648 dtv[0] = tls_dtv_generation; 2649 dtv[1] = tls_max_index; 2650 2651 for (obj = objs; obj; obj = obj->next) { 2652 if (obj->tlsoffset) { 2653 addr = (Elf_Addr)tcb - obj->tlsoffset; 2654 memset((void *)(addr + obj->tlsinitsize), 2655 0, obj->tlssize - obj->tlsinitsize); 2656 if (obj->tlsinit) 2657 memcpy((void*) addr, obj->tlsinit, obj->tlsinitsize); 2658 dtv[obj->tlsindex + 1] = addr; 2659 } 2660 } 2661 return(tcb); 2662 } 2663 2664 void 2665 free_tls(struct tls_tcb *tcb) 2666 { 2667 Elf_Addr *dtv; 2668 int dtv_size, i; 2669 Elf_Addr tls_start, tls_end; 2670 size_t data_size; 2671 2672 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) & 2673 ~RTLD_STATIC_TLS_ALIGN_MASK; 2674 dtv = tcb->tcb_dtv; 2675 dtv_size = dtv[1]; 2676 tls_end = (Elf_Addr)tcb; 2677 tls_start = (Elf_Addr)tcb - data_size; 2678 for (i = 0; i < dtv_size; i++) { 2679 if (dtv[i+2] != NULL && (dtv[i+2] < tls_start || dtv[i+2] > tls_end)) { 2680 free((void *)dtv[i+2]); 2681 } 2682 } 2683 free((void *)tls_start); 2684 } 2685 2686 #else 2687 #error "Unsupported TLS layout" 2688 #endif 2689 2690 /* 2691 * Allocate TLS block for module with given index. 2692 */ 2693 void * 2694 allocate_module_tls(int index) 2695 { 2696 Obj_Entry* obj; 2697 char* p; 2698 2699 for (obj = obj_list; obj; obj = obj->next) { 2700 if (obj->tlsindex == index) 2701 break; 2702 } 2703 if (!obj) { 2704 _rtld_error("Can't find module with TLS index %d", index); 2705 die(); 2706 } 2707 2708 p = malloc(obj->tlssize); 2709 memcpy(p, obj->tlsinit, obj->tlsinitsize); 2710 memset(p + obj->tlsinitsize, 0, obj->tlssize - obj->tlsinitsize); 2711 2712 return p; 2713 } 2714 2715 bool 2716 allocate_tls_offset(Obj_Entry *obj) 2717 { 2718 size_t off; 2719 2720 if (obj->tls_done) 2721 return true; 2722 2723 if (obj->tlssize == 0) { 2724 obj->tls_done = true; 2725 return true; 2726 } 2727 2728 if (obj->tlsindex == 1) 2729 off = calculate_first_tls_offset(obj->tlssize, obj->tlsalign); 2730 else 2731 off = calculate_tls_offset(tls_last_offset, tls_last_size, 2732 obj->tlssize, obj->tlsalign); 2733 2734 /* 2735 * If we have already fixed the size of the static TLS block, we 2736 * must stay within that size. When allocating the static TLS, we 2737 * leave a small amount of space spare to be used for dynamically 2738 * loading modules which use static TLS. 2739 */ 2740 if (tls_static_space) { 2741 if (calculate_tls_end(off, obj->tlssize) > tls_static_space) 2742 return false; 2743 } 2744 2745 tls_last_offset = obj->tlsoffset = off; 2746 tls_last_size = obj->tlssize; 2747 obj->tls_done = true; 2748 2749 return true; 2750 } 2751 2752 void 2753 free_tls_offset(Obj_Entry *obj) 2754 { 2755 #ifdef RTLD_STATIC_TLS_VARIANT_II 2756 /* 2757 * If we were the last thing to allocate out of the static TLS 2758 * block, we give our space back to the 'allocator'. This is a 2759 * simplistic workaround to allow libGL.so.1 to be loaded and 2760 * unloaded multiple times. We only handle the Variant II 2761 * mechanism for now - this really needs a proper allocator. 2762 */ 2763 if (calculate_tls_end(obj->tlsoffset, obj->tlssize) 2764 == calculate_tls_end(tls_last_offset, tls_last_size)) { 2765 tls_last_offset -= obj->tlssize; 2766 tls_last_size = 0; 2767 } 2768 #endif 2769 } 2770 2771 struct tls_tcb * 2772 _rtld_allocate_tls(void) 2773 { 2774 struct tls_tcb *new_tcb; 2775 2776 wlock_acquire(); 2777 new_tcb = allocate_tls(obj_list); 2778 wlock_release(); 2779 2780 return (new_tcb); 2781 } 2782 2783 void 2784 _rtld_free_tls(struct tls_tcb *tcb) 2785 { 2786 wlock_acquire(); 2787 free_tls(tcb); 2788 wlock_release(); 2789 } 2790 2791