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 1.27 2007/02/22 13:15:55 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 *, int); 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, Obj_Entry *); 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 const Elf_Sym *symlook_needed(const char *, unsigned long, 130 const Needed_Entry *, const Obj_Entry **, bool in_plt, DoneList *); 131 static void trace_loaded_objects(Obj_Entry *obj); 132 static void unlink_object(Obj_Entry *); 133 static void unload_object(Obj_Entry *); 134 static void unref_dag(Obj_Entry *); 135 136 void r_debug_state(struct r_debug*, struct link_map*); 137 138 /* 139 * Data declarations. 140 */ 141 static char *error_message; /* Message for dlerror(), or NULL */ 142 struct r_debug r_debug; /* for GDB; */ 143 static bool trust; /* False for setuid and setgid programs */ 144 static const char *ld_bind_now; /* Environment variable for immediate binding */ 145 static const char *ld_debug; /* Environment variable for debugging */ 146 static const char *ld_library_path; /* Environment variable for search path */ 147 static char *ld_preload; /* Environment variable for libraries to 148 load first */ 149 static const char *ld_tracing; /* Called from ldd(1) to print libs */ 150 static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 151 static Obj_Entry **obj_tail; /* Link field of last object in list */ 152 static Obj_Entry **preload_tail; 153 static Obj_Entry *obj_main; /* The main program shared object */ 154 static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 155 static unsigned int obj_count; /* Number of objects in obj_list */ 156 static int ld_resident; /* Non-zero if resident */ 157 static const char *ld_ary[LD_ARY_CACHE]; 158 static int ld_index; 159 static Objlist initlist; 160 161 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 162 STAILQ_HEAD_INITIALIZER(list_global); 163 static Objlist list_main = /* Objects loaded at program startup */ 164 STAILQ_HEAD_INITIALIZER(list_main); 165 static Objlist list_fini = /* Objects needing fini() calls */ 166 STAILQ_HEAD_INITIALIZER(list_fini); 167 168 static LockInfo lockinfo; 169 170 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 171 172 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); 173 174 extern Elf_Dyn _DYNAMIC; 175 #pragma weak _DYNAMIC 176 177 /* 178 * These are the functions the dynamic linker exports to application 179 * programs. They are the only symbols the dynamic linker is willing 180 * to export from itself. 181 */ 182 static func_ptr_type exports[] = { 183 (func_ptr_type) &_rtld_error, 184 (func_ptr_type) &dlclose, 185 (func_ptr_type) &dlerror, 186 (func_ptr_type) &dlopen, 187 (func_ptr_type) &dlsym, 188 (func_ptr_type) &dladdr, 189 (func_ptr_type) &dlinfo, 190 #ifdef __i386__ 191 (func_ptr_type) &___tls_get_addr, 192 #endif 193 (func_ptr_type) &__tls_get_addr, 194 (func_ptr_type) &__tls_get_addr_tcb, 195 (func_ptr_type) &_rtld_allocate_tls, 196 (func_ptr_type) &_rtld_free_tls, 197 (func_ptr_type) &_rtld_call_init, 198 NULL 199 }; 200 201 /* 202 * Global declarations normally provided by crt1. The dynamic linker is 203 * not built with crt1, so we have to provide them ourselves. 204 */ 205 char *__progname; 206 char **environ; 207 208 /* 209 * Globals to control TLS allocation. 210 */ 211 size_t tls_last_offset; /* Static TLS offset of last module */ 212 size_t tls_last_size; /* Static TLS size of last module */ 213 size_t tls_static_space; /* Static TLS space allocated */ 214 int tls_dtv_generation = 1; /* Used to detect when dtv size changes */ 215 int tls_max_index = 1; /* Largest module index allocated */ 216 217 /* 218 * Fill in a DoneList with an allocation large enough to hold all of 219 * the currently-loaded objects. Keep this as a macro since it calls 220 * alloca and we want that to occur within the scope of the caller. 221 */ 222 #define donelist_init(dlp) \ 223 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ 224 assert((dlp)->objs != NULL), \ 225 (dlp)->num_alloc = obj_count, \ 226 (dlp)->num_used = 0) 227 228 static __inline void 229 rlock_acquire(void) 230 { 231 lockinfo.rlock_acquire(lockinfo.thelock); 232 atomic_incr_int(&lockinfo.rcount); 233 lock_check(); 234 } 235 236 static __inline void 237 wlock_acquire(void) 238 { 239 lockinfo.wlock_acquire(lockinfo.thelock); 240 atomic_incr_int(&lockinfo.wcount); 241 lock_check(); 242 } 243 244 static __inline void 245 rlock_release(void) 246 { 247 atomic_decr_int(&lockinfo.rcount); 248 lockinfo.rlock_release(lockinfo.thelock); 249 } 250 251 static __inline void 252 wlock_release(void) 253 { 254 atomic_decr_int(&lockinfo.wcount); 255 lockinfo.wlock_release(lockinfo.thelock); 256 } 257 258 /* 259 * Main entry point for dynamic linking. The first argument is the 260 * stack pointer. The stack is expected to be laid out as described 261 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 262 * Specifically, the stack pointer points to a word containing 263 * ARGC. Following that in the stack is a null-terminated sequence 264 * of pointers to argument strings. Then comes a null-terminated 265 * sequence of pointers to environment strings. Finally, there is a 266 * sequence of "auxiliary vector" entries. 267 * 268 * The second argument points to a place to store the dynamic linker's 269 * exit procedure pointer and the third to a place to store the main 270 * program's object. 271 * 272 * The return value is the main program's entry point. 273 */ 274 275 func_ptr_type 276 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 277 { 278 Elf_Auxinfo *aux_info[AT_COUNT]; 279 int i; 280 int argc; 281 char **argv; 282 char **env; 283 Elf_Auxinfo *aux; 284 Elf_Auxinfo *auxp; 285 const char *argv0; 286 Objlist_Entry *entry; 287 Obj_Entry *obj; 288 289 ld_index = 0; /* don't use old env cache in case we are resident */ 290 291 /* 292 * On entry, the dynamic linker itself has not been relocated yet. 293 * Be very careful not to reference any global data until after 294 * init_rtld has returned. It is OK to reference file-scope statics 295 * and string constants, and to call static and global functions. 296 */ 297 298 /* Find the auxiliary vector on the stack. */ 299 argc = *sp++; 300 argv = (char **) sp; 301 sp += argc + 1; /* Skip over arguments and NULL terminator */ 302 env = (char **) sp; 303 304 /* 305 * If we aren't already resident we have to dig out some more info. 306 * Note that auxinfo does not exist when we are resident. 307 */ 308 if (ld_resident == 0) { 309 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 310 ; 311 aux = (Elf_Auxinfo *) sp; 312 313 /* Digest the auxiliary vector. */ 314 for (i = 0; i < AT_COUNT; i++) 315 aux_info[i] = NULL; 316 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 317 if (auxp->a_type < AT_COUNT) 318 aux_info[auxp->a_type] = auxp; 319 } 320 321 /* Initialize and relocate ourselves. */ 322 assert(aux_info[AT_BASE] != NULL); 323 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 324 } 325 326 __progname = obj_rtld.path; 327 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 328 environ = env; 329 330 trust = (geteuid() == getuid()) && (getegid() == getgid()); 331 332 ld_bind_now = _getenv_ld("LD_BIND_NOW"); 333 if (trust) { 334 ld_debug = _getenv_ld("LD_DEBUG"); 335 ld_library_path = _getenv_ld("LD_LIBRARY_PATH"); 336 ld_preload = (char *)_getenv_ld("LD_PRELOAD"); 337 } 338 ld_tracing = _getenv_ld("LD_TRACE_LOADED_OBJECTS"); 339 340 if (ld_debug != NULL && *ld_debug != '\0') 341 debug = 1; 342 dbg("%s is initialized, base address = %p", __progname, 343 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 344 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 345 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 346 347 /* 348 * If we are resident we can skip work that we have already done. 349 * Note that the stack is reset and there is no Elf_Auxinfo 350 * when running from a resident image, and the static globals setup 351 * between here and resident_skip will have already been setup. 352 */ 353 if (ld_resident) 354 goto resident_skip1; 355 356 /* 357 * Load the main program, or process its program header if it is 358 * already loaded. 359 */ 360 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 361 int fd = aux_info[AT_EXECFD]->a_un.a_val; 362 dbg("loading main program"); 363 obj_main = map_object(fd, argv0, NULL); 364 close(fd); 365 if (obj_main == NULL) 366 die(); 367 } else { /* Main program already loaded. */ 368 const Elf_Phdr *phdr; 369 int phnum; 370 caddr_t entry; 371 372 dbg("processing main program's program header"); 373 assert(aux_info[AT_PHDR] != NULL); 374 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 375 assert(aux_info[AT_PHNUM] != NULL); 376 phnum = aux_info[AT_PHNUM]->a_un.a_val; 377 assert(aux_info[AT_PHENT] != NULL); 378 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 379 assert(aux_info[AT_ENTRY] != NULL); 380 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 381 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 382 die(); 383 } 384 385 obj_main->path = xstrdup(argv0); 386 obj_main->mainprog = true; 387 388 /* 389 * Get the actual dynamic linker pathname from the executable if 390 * possible. (It should always be possible.) That ensures that 391 * gdb will find the right dynamic linker even if a non-standard 392 * one is being used. 393 */ 394 if (obj_main->interp != NULL && 395 strcmp(obj_main->interp, obj_rtld.path) != 0) { 396 free(obj_rtld.path); 397 obj_rtld.path = xstrdup(obj_main->interp); 398 __progname = obj_rtld.path; 399 } 400 401 digest_dynamic(obj_main, 0); 402 403 linkmap_add(obj_main); 404 linkmap_add(&obj_rtld); 405 406 /* Link the main program into the list of objects. */ 407 *obj_tail = obj_main; 408 obj_tail = &obj_main->next; 409 obj_count++; 410 obj_main->refcount++; 411 /* Make sure we don't call the main program's init and fini functions. */ 412 obj_main->init = obj_main->fini = NULL; 413 414 /* Initialize a fake symbol for resolving undefined weak references. */ 415 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 416 sym_zero.st_shndx = SHN_ABS; 417 418 dbg("loading LD_PRELOAD libraries"); 419 if (load_preload_objects() == -1) 420 die(); 421 preload_tail = obj_tail; 422 423 dbg("loading needed objects"); 424 if (load_needed_objects(obj_main) == -1) 425 die(); 426 427 /* Make a list of all objects loaded at startup. */ 428 for (obj = obj_list; obj != NULL; obj = obj->next) 429 objlist_push_tail(&list_main, obj); 430 431 resident_skip1: 432 433 if (ld_tracing) { /* We're done */ 434 trace_loaded_objects(obj_main); 435 exit(0); 436 } 437 438 if (ld_resident) /* XXX clean this up! */ 439 goto resident_skip2; 440 441 if (getenv("LD_DUMP_REL_PRE") != NULL) { 442 dump_relocations(obj_main); 443 exit (0); 444 } 445 446 /* setup TLS for main thread */ 447 dbg("initializing initial thread local storage"); 448 STAILQ_FOREACH(entry, &list_main, link) { 449 /* 450 * Allocate all the initial objects out of the static TLS 451 * block even if they didn't ask for it. 452 */ 453 allocate_tls_offset(entry->obj); 454 } 455 456 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; 457 458 /* 459 * Do not try to allocate the TLS here, let libc do it itself. 460 * (crt1 for the program will call _init_tls()) 461 */ 462 463 if (relocate_objects(obj_main, 464 ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1) 465 die(); 466 467 dbg("doing copy relocations"); 468 if (do_copy_relocations(obj_main) == -1) 469 die(); 470 471 resident_skip2: 472 473 if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) { 474 if (exec_sys_unregister(-1) < 0) { 475 dbg("exec_sys_unregister failed %d\n", errno); 476 exit(errno); 477 } 478 dbg("exec_sys_unregister success\n"); 479 exit(0); 480 } 481 482 if (getenv("LD_DUMP_REL_POST") != NULL) { 483 dump_relocations(obj_main); 484 exit (0); 485 } 486 487 dbg("initializing key program variables"); 488 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 489 set_program_var("environ", env); 490 491 if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) { 492 extern void resident_start(void); 493 ld_resident = 1; 494 if (exec_sys_register(resident_start) < 0) { 495 dbg("exec_sys_register failed %d\n", errno); 496 exit(errno); 497 } 498 dbg("exec_sys_register success\n"); 499 exit(0); 500 } 501 502 dbg("initializing thread locks"); 503 lockdflt_init(&lockinfo); 504 lockinfo.thelock = lockinfo.lock_create(lockinfo.context); 505 506 /* Make a list of init functions to call. */ 507 objlist_init(&initlist); 508 initlist_add_objects(obj_list, preload_tail, &initlist); 509 510 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ 511 512 /* 513 * Do NOT call the initlist here, give libc a chance to set up 514 * the initial TLS segment. crt1 will then call _rtld_call_init(). 515 */ 516 517 dbg("transferring control to program entry point = %p", obj_main->entry); 518 519 /* Return the exit procedure and the program entry point. */ 520 *exit_proc = rtld_exit; 521 *objp = obj_main; 522 return (func_ptr_type) obj_main->entry; 523 } 524 525 /* 526 * Call the initialization list for dynamically loaded libraries. 527 * (called from crt1.c). 528 */ 529 void 530 _rtld_call_init(void) 531 { 532 objlist_call_init(&initlist); 533 wlock_acquire(); 534 objlist_clear(&initlist); 535 wlock_release(); 536 } 537 538 Elf_Addr 539 _rtld_bind(Obj_Entry *obj, Elf_Word reloff) 540 { 541 const Elf_Rel *rel; 542 const Elf_Sym *def; 543 const Obj_Entry *defobj; 544 Elf_Addr *where; 545 Elf_Addr target; 546 547 rlock_acquire(); 548 if (obj->pltrel) 549 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 550 else 551 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 552 553 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 554 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 555 if (def == NULL) 556 die(); 557 558 target = (Elf_Addr)(defobj->relocbase + def->st_value); 559 560 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 561 defobj->strtab + def->st_name, basename(obj->path), 562 (void *)target, basename(defobj->path)); 563 564 reloc_jmpslot(where, target); 565 rlock_release(); 566 return target; 567 } 568 569 /* 570 * Error reporting function. Use it like printf. If formats the message 571 * into a buffer, and sets things up so that the next call to dlerror() 572 * will return the message. 573 */ 574 void 575 _rtld_error(const char *fmt, ...) 576 { 577 static char buf[512]; 578 va_list ap; 579 580 va_start(ap, fmt); 581 vsnprintf(buf, sizeof buf, fmt, ap); 582 error_message = buf; 583 va_end(ap); 584 } 585 586 /* 587 * Return a dynamically-allocated copy of the current error message, if any. 588 */ 589 static char * 590 errmsg_save(void) 591 { 592 return error_message == NULL ? NULL : xstrdup(error_message); 593 } 594 595 /* 596 * Restore the current error message from a copy which was previously saved 597 * by errmsg_save(). The copy is freed. 598 */ 599 static void 600 errmsg_restore(char *saved_msg) 601 { 602 if (saved_msg == NULL) 603 error_message = NULL; 604 else { 605 _rtld_error("%s", saved_msg); 606 free(saved_msg); 607 } 608 } 609 610 const char * 611 basename(const char *name) 612 { 613 const char *p = strrchr(name, '/'); 614 return p != NULL ? p + 1 : name; 615 } 616 617 static void 618 die(void) 619 { 620 const char *msg = dlerror(); 621 622 if (msg == NULL) 623 msg = "Fatal error"; 624 errx(1, "%s", msg); 625 } 626 627 /* 628 * Process a shared object's DYNAMIC section, and save the important 629 * information in its Obj_Entry structure. 630 */ 631 static void 632 digest_dynamic(Obj_Entry *obj, int early) 633 { 634 const Elf_Dyn *dynp; 635 Needed_Entry **needed_tail = &obj->needed; 636 const Elf_Dyn *dyn_rpath = NULL; 637 int plttype = DT_REL; 638 639 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 640 switch (dynp->d_tag) { 641 642 case DT_REL: 643 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 644 break; 645 646 case DT_RELSZ: 647 obj->relsize = dynp->d_un.d_val; 648 break; 649 650 case DT_RELENT: 651 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 652 break; 653 654 case DT_JMPREL: 655 obj->pltrel = (const Elf_Rel *) 656 (obj->relocbase + dynp->d_un.d_ptr); 657 break; 658 659 case DT_PLTRELSZ: 660 obj->pltrelsize = dynp->d_un.d_val; 661 break; 662 663 case DT_RELA: 664 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 665 break; 666 667 case DT_RELASZ: 668 obj->relasize = dynp->d_un.d_val; 669 break; 670 671 case DT_RELAENT: 672 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 673 break; 674 675 case DT_PLTREL: 676 plttype = dynp->d_un.d_val; 677 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 678 break; 679 680 case DT_SYMTAB: 681 obj->symtab = (const Elf_Sym *) 682 (obj->relocbase + dynp->d_un.d_ptr); 683 break; 684 685 case DT_SYMENT: 686 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 687 break; 688 689 case DT_STRTAB: 690 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 691 break; 692 693 case DT_STRSZ: 694 obj->strsize = dynp->d_un.d_val; 695 break; 696 697 case DT_HASH: 698 { 699 const Elf_Addr *hashtab = (const Elf_Addr *) 700 (obj->relocbase + dynp->d_un.d_ptr); 701 obj->nbuckets = hashtab[0]; 702 obj->nchains = hashtab[1]; 703 obj->buckets = hashtab + 2; 704 obj->chains = obj->buckets + obj->nbuckets; 705 } 706 break; 707 708 case DT_NEEDED: 709 if (!obj->rtld) { 710 Needed_Entry *nep = NEW(Needed_Entry); 711 nep->name = dynp->d_un.d_val; 712 nep->obj = NULL; 713 nep->next = NULL; 714 715 *needed_tail = nep; 716 needed_tail = &nep->next; 717 } 718 break; 719 720 case DT_PLTGOT: 721 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 722 break; 723 724 case DT_TEXTREL: 725 obj->textrel = true; 726 break; 727 728 case DT_SYMBOLIC: 729 obj->symbolic = true; 730 break; 731 732 case DT_RPATH: 733 case DT_RUNPATH: /* XXX: process separately */ 734 /* 735 * We have to wait until later to process this, because we 736 * might not have gotten the address of the string table yet. 737 */ 738 dyn_rpath = dynp; 739 break; 740 741 case DT_SONAME: 742 /* Not used by the dynamic linker. */ 743 break; 744 745 case DT_INIT: 746 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 747 break; 748 749 case DT_FINI: 750 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 751 break; 752 753 case DT_DEBUG: 754 /* XXX - not implemented yet */ 755 if (!early) 756 dbg("Filling in DT_DEBUG entry"); 757 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 758 break; 759 760 case DT_FLAGS: 761 if (dynp->d_un.d_val & DF_ORIGIN) { 762 obj->origin_path = xmalloc(PATH_MAX); 763 if (rtld_dirname(obj->path, obj->origin_path) == -1) 764 die(); 765 } 766 if (dynp->d_un.d_val & DF_SYMBOLIC) 767 obj->symbolic = true; 768 if (dynp->d_un.d_val & DF_TEXTREL) 769 obj->textrel = true; 770 if (dynp->d_un.d_val & DF_BIND_NOW) 771 obj->bind_now = true; 772 if (dynp->d_un.d_val & DF_STATIC_TLS) 773 ; 774 break; 775 776 default: 777 if (!early) 778 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag); 779 break; 780 } 781 } 782 783 obj->traced = false; 784 785 if (plttype == DT_RELA) { 786 obj->pltrela = (const Elf_Rela *) obj->pltrel; 787 obj->pltrel = NULL; 788 obj->pltrelasize = obj->pltrelsize; 789 obj->pltrelsize = 0; 790 } 791 792 if (dyn_rpath != NULL) 793 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 794 } 795 796 /* 797 * Process a shared object's program header. This is used only for the 798 * main program, when the kernel has already loaded the main program 799 * into memory before calling the dynamic linker. It creates and 800 * returns an Obj_Entry structure. 801 */ 802 static Obj_Entry * 803 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 804 { 805 Obj_Entry *obj; 806 const Elf_Phdr *phlimit = phdr + phnum; 807 const Elf_Phdr *ph; 808 int nsegs = 0; 809 810 obj = obj_new(); 811 for (ph = phdr; ph < phlimit; ph++) { 812 switch (ph->p_type) { 813 814 case PT_PHDR: 815 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 816 _rtld_error("%s: invalid PT_PHDR", path); 817 return NULL; 818 } 819 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 820 obj->phsize = ph->p_memsz; 821 break; 822 823 case PT_INTERP: 824 obj->interp = (const char *) ph->p_vaddr; 825 break; 826 827 case PT_LOAD: 828 if (nsegs == 0) { /* First load segment */ 829 obj->vaddrbase = trunc_page(ph->p_vaddr); 830 obj->mapbase = (caddr_t) obj->vaddrbase; 831 obj->relocbase = obj->mapbase - obj->vaddrbase; 832 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 833 obj->vaddrbase; 834 } else { /* Last load segment */ 835 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 836 obj->vaddrbase; 837 } 838 nsegs++; 839 break; 840 841 case PT_DYNAMIC: 842 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 843 break; 844 845 case PT_TLS: 846 obj->tlsindex = 1; 847 obj->tlssize = ph->p_memsz; 848 obj->tlsalign = ph->p_align; 849 obj->tlsinitsize = ph->p_filesz; 850 obj->tlsinit = (void*) ph->p_vaddr; 851 break; 852 } 853 } 854 if (nsegs < 1) { 855 _rtld_error("%s: too few PT_LOAD segments", path); 856 return NULL; 857 } 858 859 obj->entry = entry; 860 return obj; 861 } 862 863 static Obj_Entry * 864 dlcheck(void *handle) 865 { 866 Obj_Entry *obj; 867 868 for (obj = obj_list; obj != NULL; obj = obj->next) 869 if (obj == (Obj_Entry *) handle) 870 break; 871 872 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { 873 _rtld_error("Invalid shared object handle %p", handle); 874 return NULL; 875 } 876 return obj; 877 } 878 879 /* 880 * If the given object is already in the donelist, return true. Otherwise 881 * add the object to the list and return false. 882 */ 883 static bool 884 donelist_check(DoneList *dlp, const Obj_Entry *obj) 885 { 886 unsigned int i; 887 888 for (i = 0; i < dlp->num_used; i++) 889 if (dlp->objs[i] == obj) 890 return true; 891 /* 892 * Our donelist allocation should always be sufficient. But if 893 * our threads locking isn't working properly, more shared objects 894 * could have been loaded since we allocated the list. That should 895 * never happen, but we'll handle it properly just in case it does. 896 */ 897 if (dlp->num_used < dlp->num_alloc) 898 dlp->objs[dlp->num_used++] = obj; 899 return false; 900 } 901 902 /* 903 * Hash function for symbol table lookup. Don't even think about changing 904 * this. It is specified by the System V ABI. 905 */ 906 unsigned long 907 elf_hash(const char *name) 908 { 909 const unsigned char *p = (const unsigned char *) name; 910 unsigned long h = 0; 911 unsigned long g; 912 913 while (*p != '\0') { 914 h = (h << 4) + *p++; 915 if ((g = h & 0xf0000000) != 0) 916 h ^= g >> 24; 917 h &= ~g; 918 } 919 return h; 920 } 921 922 /* 923 * Find the library with the given name, and return its full pathname. 924 * The returned string is dynamically allocated. Generates an error 925 * message and returns NULL if the library cannot be found. 926 * 927 * If the second argument is non-NULL, then it refers to an already- 928 * loaded shared object, whose library search path will be searched. 929 * 930 * The search order is: 931 * LD_LIBRARY_PATH 932 * rpath in the referencing file 933 * ldconfig hints 934 * /usr/lib 935 */ 936 static char * 937 find_library(const char *name, const Obj_Entry *refobj) 938 { 939 char *pathname; 940 941 if (strchr(name, '/') != NULL) { /* Hard coded pathname */ 942 if (name[0] != '/' && !trust) { 943 _rtld_error("Absolute pathname required for shared object \"%s\"", 944 name); 945 return NULL; 946 } 947 return xstrdup(name); 948 } 949 950 dbg(" Searching for \"%s\"", name); 951 952 if ((pathname = search_library_path(name, ld_library_path)) != NULL || 953 (refobj != NULL && 954 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 955 (pathname = search_library_path(name, gethints())) != NULL || 956 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 957 return pathname; 958 959 if(refobj != NULL && refobj->path != NULL) { 960 _rtld_error("Shared object \"%s\" not found, required by \"%s\"", 961 name, basename(refobj->path)); 962 } else { 963 _rtld_error("Shared object \"%s\" not found", name); 964 } 965 return NULL; 966 } 967 968 /* 969 * Given a symbol number in a referencing object, find the corresponding 970 * definition of the symbol. Returns a pointer to the symbol, or NULL if 971 * no definition was found. Returns a pointer to the Obj_Entry of the 972 * defining object via the reference parameter DEFOBJ_OUT. 973 */ 974 const Elf_Sym * 975 find_symdef(unsigned long symnum, const Obj_Entry *refobj, 976 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) 977 { 978 const Elf_Sym *ref; 979 const Elf_Sym *def; 980 const Obj_Entry *defobj; 981 const char *name; 982 unsigned long hash; 983 984 /* 985 * If we have already found this symbol, get the information from 986 * the cache. 987 */ 988 if (symnum >= refobj->nchains) 989 return NULL; /* Bad object */ 990 if (cache != NULL && cache[symnum].sym != NULL) { 991 *defobj_out = cache[symnum].obj; 992 return cache[symnum].sym; 993 } 994 995 ref = refobj->symtab + symnum; 996 name = refobj->strtab + ref->st_name; 997 defobj = NULL; 998 999 /* 1000 * We don't have to do a full scale lookup if the symbol is local. 1001 * We know it will bind to the instance in this load module; to 1002 * which we already have a pointer (ie ref). By not doing a lookup, 1003 * we not only improve performance, but it also avoids unresolvable 1004 * symbols when local symbols are not in the hash table. 1005 * 1006 * This might occur for TLS module relocations, which simply use 1007 * symbol 0. 1008 */ 1009 if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) { 1010 if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) { 1011 _rtld_error("%s: Bogus symbol table entry %lu", refobj->path, 1012 symnum); 1013 } 1014 hash = elf_hash(name); 1015 def = symlook_default(name, hash, refobj, &defobj, in_plt); 1016 } else { 1017 def = ref; 1018 defobj = refobj; 1019 } 1020 1021 /* 1022 * If we found no definition and the reference is weak, treat the 1023 * symbol as having the value zero. 1024 */ 1025 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 1026 def = &sym_zero; 1027 defobj = obj_main; 1028 } 1029 1030 if (def != NULL) { 1031 *defobj_out = defobj; 1032 /* Record the information in the cache to avoid subsequent lookups. */ 1033 if (cache != NULL) { 1034 cache[symnum].sym = def; 1035 cache[symnum].obj = defobj; 1036 } 1037 } else 1038 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 1039 return def; 1040 } 1041 1042 /* 1043 * Return the search path from the ldconfig hints file, reading it if 1044 * necessary. Returns NULL if there are problems with the hints file, 1045 * or if the search path there is empty. 1046 */ 1047 static const char * 1048 gethints(void) 1049 { 1050 static char *hints; 1051 1052 if (hints == NULL) { 1053 int fd; 1054 struct elfhints_hdr hdr; 1055 char *p; 1056 1057 /* Keep from trying again in case the hints file is bad. */ 1058 hints = ""; 1059 1060 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 1061 return NULL; 1062 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 1063 hdr.magic != ELFHINTS_MAGIC || 1064 hdr.version != 1) { 1065 close(fd); 1066 return NULL; 1067 } 1068 p = xmalloc(hdr.dirlistlen + 1); 1069 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 1070 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { 1071 free(p); 1072 close(fd); 1073 return NULL; 1074 } 1075 hints = p; 1076 close(fd); 1077 } 1078 return hints[0] != '\0' ? hints : NULL; 1079 } 1080 1081 static void 1082 init_dag(Obj_Entry *root) 1083 { 1084 DoneList donelist; 1085 1086 donelist_init(&donelist); 1087 init_dag1(root, root, &donelist); 1088 } 1089 1090 static void 1091 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) 1092 { 1093 const Needed_Entry *needed; 1094 1095 if (donelist_check(dlp, obj)) 1096 return; 1097 objlist_push_tail(&obj->dldags, root); 1098 objlist_push_tail(&root->dagmembers, obj); 1099 for (needed = obj->needed; needed != NULL; needed = needed->next) 1100 if (needed->obj != NULL) 1101 init_dag1(root, needed->obj, dlp); 1102 } 1103 1104 /* 1105 * Initialize the dynamic linker. The argument is the address at which 1106 * the dynamic linker has been mapped into memory. The primary task of 1107 * this function is to relocate the dynamic linker. 1108 */ 1109 static void 1110 init_rtld(caddr_t mapbase) 1111 { 1112 Obj_Entry objtmp; /* Temporary rtld object */ 1113 1114 /* 1115 * Conjure up an Obj_Entry structure for the dynamic linker. 1116 * 1117 * The "path" member can't be initialized yet because string constatns 1118 * cannot yet be acessed. Below we will set it correctly. 1119 */ 1120 objtmp.path = NULL; 1121 objtmp.rtld = true; 1122 objtmp.mapbase = mapbase; 1123 #ifdef PIC 1124 objtmp.relocbase = mapbase; 1125 #endif 1126 if (&_DYNAMIC != 0) { 1127 objtmp.dynamic = rtld_dynamic(&objtmp); 1128 digest_dynamic(&objtmp, 1); 1129 assert(objtmp.needed == NULL); 1130 assert(!objtmp.textrel); 1131 1132 /* 1133 * Temporarily put the dynamic linker entry into the object list, so 1134 * that symbols can be found. 1135 */ 1136 1137 relocate_objects(&objtmp, true, &objtmp); 1138 } 1139 1140 /* Initialize the object list. */ 1141 obj_tail = &obj_list; 1142 1143 /* Now that non-local variables can be accesses, copy out obj_rtld. */ 1144 memcpy(&obj_rtld, &objtmp, sizeof(obj_rtld)); 1145 1146 /* Replace the path with a dynamically allocated copy. */ 1147 obj_rtld.path = xstrdup(PATH_RTLD); 1148 1149 r_debug.r_brk = r_debug_state; 1150 r_debug.r_state = RT_CONSISTENT; 1151 } 1152 1153 /* 1154 * Add the init functions from a needed object list (and its recursive 1155 * needed objects) to "list". This is not used directly; it is a helper 1156 * function for initlist_add_objects(). The write lock must be held 1157 * when this function is called. 1158 */ 1159 static void 1160 initlist_add_neededs(Needed_Entry *needed, Objlist *list) 1161 { 1162 /* Recursively process the successor needed objects. */ 1163 if (needed->next != NULL) 1164 initlist_add_neededs(needed->next, list); 1165 1166 /* Process the current needed object. */ 1167 if (needed->obj != NULL) 1168 initlist_add_objects(needed->obj, &needed->obj->next, list); 1169 } 1170 1171 /* 1172 * Scan all of the DAGs rooted in the range of objects from "obj" to 1173 * "tail" and add their init functions to "list". This recurses over 1174 * the DAGs and ensure the proper init ordering such that each object's 1175 * needed libraries are initialized before the object itself. At the 1176 * same time, this function adds the objects to the global finalization 1177 * list "list_fini" in the opposite order. The write lock must be 1178 * held when this function is called. 1179 */ 1180 static void 1181 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) 1182 { 1183 if (obj->init_done) 1184 return; 1185 obj->init_done = true; 1186 1187 /* Recursively process the successor objects. */ 1188 if (&obj->next != tail) 1189 initlist_add_objects(obj->next, tail, list); 1190 1191 /* Recursively process the needed objects. */ 1192 if (obj->needed != NULL) 1193 initlist_add_neededs(obj->needed, list); 1194 1195 /* Add the object to the init list. */ 1196 if (obj->init != NULL) 1197 objlist_push_tail(list, obj); 1198 1199 /* Add the object to the global fini list in the reverse order. */ 1200 if (obj->fini != NULL) 1201 objlist_push_head(&list_fini, obj); 1202 } 1203 1204 static bool 1205 is_exported(const Elf_Sym *def) 1206 { 1207 func_ptr_type value; 1208 const func_ptr_type *p; 1209 1210 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value); 1211 for (p = exports; *p != NULL; p++) 1212 if (*p == value) 1213 return true; 1214 return false; 1215 } 1216 1217 /* 1218 * Given a shared object, traverse its list of needed objects, and load 1219 * each of them. Returns 0 on success. Generates an error message and 1220 * returns -1 on failure. 1221 */ 1222 static int 1223 load_needed_objects(Obj_Entry *first) 1224 { 1225 Obj_Entry *obj; 1226 1227 for (obj = first; obj != NULL; obj = obj->next) { 1228 Needed_Entry *needed; 1229 1230 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1231 const char *name = obj->strtab + needed->name; 1232 char *path = find_library(name, obj); 1233 1234 needed->obj = NULL; 1235 if (path == NULL && !ld_tracing) 1236 return -1; 1237 1238 if (path) { 1239 needed->obj = load_object(path); 1240 if (needed->obj == NULL && !ld_tracing) 1241 return -1; /* XXX - cleanup */ 1242 } 1243 } 1244 } 1245 1246 return 0; 1247 } 1248 1249 static int 1250 load_preload_objects(void) 1251 { 1252 char *p = ld_preload; 1253 static const char delim[] = " \t:;"; 1254 1255 if (p == NULL) 1256 return NULL; 1257 1258 p += strspn(p, delim); 1259 while (*p != '\0') { 1260 size_t len = strcspn(p, delim); 1261 char *path; 1262 char savech; 1263 1264 savech = p[len]; 1265 p[len] = '\0'; 1266 if ((path = find_library(p, NULL)) == NULL) 1267 return -1; 1268 if (load_object(path) == NULL) 1269 return -1; /* XXX - cleanup */ 1270 p[len] = savech; 1271 p += len; 1272 p += strspn(p, delim); 1273 } 1274 return 0; 1275 } 1276 1277 /* 1278 * Returns a pointer to the Obj_Entry for the object with the given path. 1279 * Returns NULL if no matching object was found. 1280 */ 1281 static Obj_Entry * 1282 find_object(const char *path) 1283 { 1284 Obj_Entry *obj; 1285 1286 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1287 if (strcmp(obj->path, path) == 0) 1288 return(obj); 1289 } 1290 return(NULL); 1291 } 1292 1293 /* 1294 * Returns a pointer to the Obj_Entry for the object matching device and 1295 * inode of the given path. If no matching object was found, the descriptor 1296 * is returned in fd. 1297 * Returns with obj == NULL && fd == -1 on error. 1298 */ 1299 static Obj_Entry * 1300 find_object2(const char *path, int *fd, struct stat *sb) 1301 { 1302 Obj_Entry *obj; 1303 1304 if ((*fd = open(path, O_RDONLY)) == -1) { 1305 _rtld_error("Cannot open \"%s\"", path); 1306 return(NULL); 1307 } 1308 1309 if (fstat(*fd, sb) == -1) { 1310 _rtld_error("Cannot fstat \"%s\"", path); 1311 close(*fd); 1312 *fd = -1; 1313 return NULL; 1314 } 1315 1316 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1317 if (obj->ino == sb->st_ino && obj->dev == sb->st_dev) { 1318 close(*fd); 1319 break; 1320 } 1321 } 1322 1323 return(obj); 1324 } 1325 1326 /* 1327 * Load a shared object into memory, if it is not already loaded. The 1328 * argument must be a string allocated on the heap. This function assumes 1329 * responsibility for freeing it when necessary. 1330 * 1331 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1332 * on failure. 1333 */ 1334 static Obj_Entry * 1335 load_object(char *path) 1336 { 1337 Obj_Entry *obj; 1338 int fd = -1; 1339 struct stat sb; 1340 1341 obj = find_object(path); 1342 if (obj != NULL) { 1343 obj->refcount++; 1344 free(path); 1345 return(obj); 1346 } 1347 1348 obj = find_object2(path, &fd, &sb); 1349 if (obj != NULL) { 1350 obj->refcount++; 1351 free(path); 1352 return(obj); 1353 } else if (fd == -1) { 1354 free(path); 1355 return(NULL); 1356 } 1357 1358 dbg("loading \"%s\"", path); 1359 obj = map_object(fd, path, &sb); 1360 close(fd); 1361 if (obj == NULL) { 1362 free(path); 1363 return NULL; 1364 } 1365 1366 obj->path = path; 1367 digest_dynamic(obj, 0); 1368 1369 *obj_tail = obj; 1370 obj_tail = &obj->next; 1371 obj_count++; 1372 linkmap_add(obj); /* for GDB & dlinfo() */ 1373 1374 dbg(" %p .. %p: %s", obj->mapbase, obj->mapbase + obj->mapsize - 1, 1375 obj->path); 1376 if (obj->textrel) 1377 dbg(" WARNING: %s has impure text", obj->path); 1378 1379 obj->refcount++; 1380 return obj; 1381 } 1382 1383 /* 1384 * Check for locking violations and die if one is found. 1385 */ 1386 static void 1387 lock_check(void) 1388 { 1389 int rcount, wcount; 1390 1391 rcount = lockinfo.rcount; 1392 wcount = lockinfo.wcount; 1393 assert(rcount >= 0); 1394 assert(wcount >= 0); 1395 if (wcount > 1 || (wcount != 0 && rcount != 0)) { 1396 _rtld_error("Application locking error: %d readers and %d writers" 1397 " in dynamic linker. See DLLOCKINIT(3) in manual pages.", 1398 rcount, wcount); 1399 die(); 1400 } 1401 } 1402 1403 static Obj_Entry * 1404 obj_from_addr(const void *addr) 1405 { 1406 Obj_Entry *obj; 1407 1408 for (obj = obj_list; obj != NULL; obj = obj->next) { 1409 if (addr < (void *) obj->mapbase) 1410 continue; 1411 if (addr < (void *) (obj->mapbase + obj->mapsize)) 1412 return obj; 1413 } 1414 return NULL; 1415 } 1416 1417 /* 1418 * Call the finalization functions for each of the objects in "list" 1419 * which are unreferenced. All of the objects are expected to have 1420 * non-NULL fini functions. 1421 */ 1422 static void 1423 objlist_call_fini(Objlist *list) 1424 { 1425 Objlist_Entry *elm; 1426 char *saved_msg; 1427 1428 /* 1429 * Preserve the current error message since a fini function might 1430 * call into the dynamic linker and overwrite it. 1431 */ 1432 saved_msg = errmsg_save(); 1433 STAILQ_FOREACH(elm, list, link) { 1434 if (elm->obj->refcount == 0) { 1435 dbg("calling fini function for %s", elm->obj->path); 1436 (*elm->obj->fini)(); 1437 } 1438 } 1439 errmsg_restore(saved_msg); 1440 } 1441 1442 /* 1443 * Call the initialization functions for each of the objects in 1444 * "list". All of the objects are expected to have non-NULL init 1445 * functions. 1446 */ 1447 static void 1448 objlist_call_init(Objlist *list) 1449 { 1450 Objlist_Entry *elm; 1451 char *saved_msg; 1452 1453 /* 1454 * Preserve the current error message since an init function might 1455 * call into the dynamic linker and overwrite it. 1456 */ 1457 saved_msg = errmsg_save(); 1458 STAILQ_FOREACH(elm, list, link) { 1459 dbg("calling init function for %s", elm->obj->path); 1460 (*elm->obj->init)(); 1461 } 1462 errmsg_restore(saved_msg); 1463 } 1464 1465 static void 1466 objlist_clear(Objlist *list) 1467 { 1468 Objlist_Entry *elm; 1469 1470 while (!STAILQ_EMPTY(list)) { 1471 elm = STAILQ_FIRST(list); 1472 STAILQ_REMOVE_HEAD(list, link); 1473 free(elm); 1474 } 1475 } 1476 1477 static Objlist_Entry * 1478 objlist_find(Objlist *list, const Obj_Entry *obj) 1479 { 1480 Objlist_Entry *elm; 1481 1482 STAILQ_FOREACH(elm, list, link) 1483 if (elm->obj == obj) 1484 return elm; 1485 return NULL; 1486 } 1487 1488 static void 1489 objlist_init(Objlist *list) 1490 { 1491 STAILQ_INIT(list); 1492 } 1493 1494 static void 1495 objlist_push_head(Objlist *list, Obj_Entry *obj) 1496 { 1497 Objlist_Entry *elm; 1498 1499 elm = NEW(Objlist_Entry); 1500 elm->obj = obj; 1501 STAILQ_INSERT_HEAD(list, elm, link); 1502 } 1503 1504 static void 1505 objlist_push_tail(Objlist *list, Obj_Entry *obj) 1506 { 1507 Objlist_Entry *elm; 1508 1509 elm = NEW(Objlist_Entry); 1510 elm->obj = obj; 1511 STAILQ_INSERT_TAIL(list, elm, link); 1512 } 1513 1514 static void 1515 objlist_remove(Objlist *list, Obj_Entry *obj) 1516 { 1517 Objlist_Entry *elm; 1518 1519 if ((elm = objlist_find(list, obj)) != NULL) { 1520 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1521 free(elm); 1522 } 1523 } 1524 1525 /* 1526 * Remove all of the unreferenced objects from "list". 1527 */ 1528 static void 1529 objlist_remove_unref(Objlist *list) 1530 { 1531 Objlist newlist; 1532 Objlist_Entry *elm; 1533 1534 STAILQ_INIT(&newlist); 1535 while (!STAILQ_EMPTY(list)) { 1536 elm = STAILQ_FIRST(list); 1537 STAILQ_REMOVE_HEAD(list, link); 1538 if (elm->obj->refcount == 0) 1539 free(elm); 1540 else 1541 STAILQ_INSERT_TAIL(&newlist, elm, link); 1542 } 1543 *list = newlist; 1544 } 1545 1546 /* 1547 * Relocate newly-loaded shared objects. The argument is a pointer to 1548 * the Obj_Entry for the first such object. All objects from the first 1549 * to the end of the list of objects are relocated. Returns 0 on success, 1550 * or -1 on failure. 1551 */ 1552 static int 1553 relocate_objects(Obj_Entry *first, bool bind_now, Obj_Entry *rtldobj) 1554 { 1555 Obj_Entry *obj; 1556 1557 for (obj = first; obj != NULL; obj = obj->next) { 1558 if (obj != rtldobj) 1559 dbg("relocating \"%s\"", obj->path); 1560 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1561 obj->symtab == NULL || obj->strtab == NULL) { 1562 _rtld_error("%s: Shared object has no run-time symbol table", 1563 obj->path); 1564 return -1; 1565 } 1566 1567 if (obj->textrel) { 1568 /* There are relocations to the write-protected text segment. */ 1569 if (mprotect(obj->mapbase, obj->textsize, 1570 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1571 _rtld_error("%s: Cannot write-enable text segment: %s", 1572 obj->path, strerror(errno)); 1573 return -1; 1574 } 1575 } 1576 1577 /* Process the non-PLT relocations. */ 1578 if (reloc_non_plt(obj, rtldobj)) 1579 return -1; 1580 1581 /* 1582 * Reprotect the text segment. Make sure it is included in the 1583 * core dump since we modified it. This unfortunately causes the 1584 * entire text segment to core-out but we don't have much of a 1585 * choice. We could try to only reenable core dumps on pages 1586 * in which relocations occured but that is likely most of the text 1587 * pages anyway, and even that would not work because the rest of 1588 * the text pages would wind up as a read-only OBJT_DEFAULT object 1589 * (created due to our modifications) backed by the original OBJT_VNODE 1590 * object, and the ELF coredump code is currently only able to dump 1591 * vnode records for pure vnode-backed mappings, not vnode backings 1592 * to memory objects. 1593 */ 1594 if (obj->textrel) { 1595 madvise(obj->mapbase, obj->textsize, MADV_CORE); 1596 if (mprotect(obj->mapbase, obj->textsize, 1597 PROT_READ|PROT_EXEC) == -1) { 1598 _rtld_error("%s: Cannot write-protect text segment: %s", 1599 obj->path, strerror(errno)); 1600 return -1; 1601 } 1602 } 1603 1604 /* Process the PLT relocations. */ 1605 if (reloc_plt(obj) == -1) 1606 return -1; 1607 /* Relocate the jump slots if we are doing immediate binding. */ 1608 if (obj->bind_now || bind_now) 1609 if (reloc_jmpslots(obj) == -1) 1610 return -1; 1611 1612 1613 /* 1614 * Set up the magic number and version in the Obj_Entry. These 1615 * were checked in the crt1.o from the original ElfKit, so we 1616 * set them for backward compatibility. 1617 */ 1618 obj->magic = RTLD_MAGIC; 1619 obj->version = RTLD_VERSION; 1620 1621 /* Set the special PLT or GOT entries. */ 1622 init_pltgot(obj); 1623 } 1624 1625 return 0; 1626 } 1627 1628 /* 1629 * Cleanup procedure. It will be called (by the atexit mechanism) just 1630 * before the process exits. 1631 */ 1632 static void 1633 rtld_exit(void) 1634 { 1635 Obj_Entry *obj; 1636 1637 dbg("rtld_exit()"); 1638 /* Clear all the reference counts so the fini functions will be called. */ 1639 for (obj = obj_list; obj != NULL; obj = obj->next) 1640 obj->refcount = 0; 1641 objlist_call_fini(&list_fini); 1642 /* No need to remove the items from the list, since we are exiting. */ 1643 } 1644 1645 static void * 1646 path_enumerate(const char *path, path_enum_proc callback, void *arg) 1647 { 1648 if (path == NULL) 1649 return (NULL); 1650 1651 path += strspn(path, ":;"); 1652 while (*path != '\0') { 1653 size_t len; 1654 char *res; 1655 1656 len = strcspn(path, ":;"); 1657 res = callback(path, len, arg); 1658 1659 if (res != NULL) 1660 return (res); 1661 1662 path += len; 1663 path += strspn(path, ":;"); 1664 } 1665 1666 return (NULL); 1667 } 1668 1669 struct try_library_args { 1670 const char *name; 1671 size_t namelen; 1672 char *buffer; 1673 size_t buflen; 1674 }; 1675 1676 static void * 1677 try_library_path(const char *dir, size_t dirlen, void *param) 1678 { 1679 struct try_library_args *arg; 1680 1681 arg = param; 1682 if (*dir == '/' || trust) { 1683 char *pathname; 1684 1685 if (dirlen + 1 + arg->namelen + 1 > arg->buflen) 1686 return (NULL); 1687 1688 pathname = arg->buffer; 1689 strncpy(pathname, dir, dirlen); 1690 pathname[dirlen] = '/'; 1691 strcpy(pathname + dirlen + 1, arg->name); 1692 1693 dbg(" Trying \"%s\"", pathname); 1694 if (access(pathname, F_OK) == 0) { /* We found it */ 1695 pathname = xmalloc(dirlen + 1 + arg->namelen + 1); 1696 strcpy(pathname, arg->buffer); 1697 return (pathname); 1698 } 1699 } 1700 return (NULL); 1701 } 1702 1703 static char * 1704 search_library_path(const char *name, const char *path) 1705 { 1706 char *p; 1707 struct try_library_args arg; 1708 1709 if (path == NULL) 1710 return NULL; 1711 1712 arg.name = name; 1713 arg.namelen = strlen(name); 1714 arg.buffer = xmalloc(PATH_MAX); 1715 arg.buflen = PATH_MAX; 1716 1717 p = path_enumerate(path, try_library_path, &arg); 1718 1719 free(arg.buffer); 1720 1721 return (p); 1722 } 1723 1724 int 1725 dlclose(void *handle) 1726 { 1727 Obj_Entry *root; 1728 1729 wlock_acquire(); 1730 root = dlcheck(handle); 1731 if (root == NULL) { 1732 wlock_release(); 1733 return -1; 1734 } 1735 1736 /* Unreference the object and its dependencies. */ 1737 root->dl_refcount--; 1738 unref_dag(root); 1739 1740 if (root->refcount == 0) { 1741 /* 1742 * The object is no longer referenced, so we must unload it. 1743 * First, call the fini functions with no locks held. 1744 */ 1745 wlock_release(); 1746 objlist_call_fini(&list_fini); 1747 wlock_acquire(); 1748 objlist_remove_unref(&list_fini); 1749 1750 /* Finish cleaning up the newly-unreferenced objects. */ 1751 GDB_STATE(RT_DELETE,&root->linkmap); 1752 unload_object(root); 1753 GDB_STATE(RT_CONSISTENT,NULL); 1754 } 1755 wlock_release(); 1756 return 0; 1757 } 1758 1759 const char * 1760 dlerror(void) 1761 { 1762 char *msg = error_message; 1763 error_message = NULL; 1764 return msg; 1765 } 1766 1767 void * 1768 dlopen(const char *name, int mode) 1769 { 1770 Obj_Entry **old_obj_tail; 1771 Obj_Entry *obj; 1772 Objlist initlist; 1773 int result; 1774 1775 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1"; 1776 if (ld_tracing != NULL) 1777 environ = (char **)*get_program_var_addr("environ"); 1778 1779 objlist_init(&initlist); 1780 1781 wlock_acquire(); 1782 GDB_STATE(RT_ADD,NULL); 1783 1784 old_obj_tail = obj_tail; 1785 obj = NULL; 1786 if (name == NULL) { 1787 obj = obj_main; 1788 obj->refcount++; 1789 } else { 1790 char *path = find_library(name, obj_main); 1791 if (path != NULL) 1792 obj = load_object(path); 1793 } 1794 1795 if (obj) { 1796 obj->dl_refcount++; 1797 if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL) 1798 objlist_push_tail(&list_global, obj); 1799 mode &= RTLD_MODEMASK; 1800 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1801 assert(*old_obj_tail == obj); 1802 1803 result = load_needed_objects(obj); 1804 if (result != -1 && ld_tracing) 1805 goto trace; 1806 1807 if (result == -1 || 1808 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW, 1809 &obj_rtld)) == -1) { 1810 obj->dl_refcount--; 1811 unref_dag(obj); 1812 if (obj->refcount == 0) 1813 unload_object(obj); 1814 obj = NULL; 1815 } else { 1816 /* Make list of init functions to call. */ 1817 initlist_add_objects(obj, &obj->next, &initlist); 1818 } 1819 } else if (ld_tracing) 1820 goto trace; 1821 } 1822 1823 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); 1824 1825 /* Call the init functions with no locks held. */ 1826 wlock_release(); 1827 objlist_call_init(&initlist); 1828 wlock_acquire(); 1829 objlist_clear(&initlist); 1830 wlock_release(); 1831 return obj; 1832 trace: 1833 trace_loaded_objects(obj); 1834 wlock_release(); 1835 exit(0); 1836 } 1837 1838 void * 1839 dlsym(void *handle, const char *name) 1840 { 1841 const Obj_Entry *obj; 1842 unsigned long hash; 1843 const Elf_Sym *def; 1844 const Obj_Entry *defobj; 1845 1846 hash = elf_hash(name); 1847 def = NULL; 1848 defobj = NULL; 1849 1850 rlock_acquire(); 1851 if (handle == NULL || handle == RTLD_NEXT || 1852 handle == RTLD_DEFAULT || 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 rlock_release(); 1859 return NULL; 1860 } 1861 if (handle == NULL) { /* Just the caller's shared object. */ 1862 def = symlook_obj(name, hash, obj, true); 1863 defobj = obj; 1864 } else if (handle == RTLD_NEXT || /* Objects after caller's */ 1865 handle == RTLD_SELF) { /* ... caller included */ 1866 if (handle == RTLD_NEXT) 1867 obj = obj->next; 1868 for (; obj != NULL; obj = obj->next) { 1869 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1870 defobj = obj; 1871 break; 1872 } 1873 } 1874 } else { 1875 assert(handle == RTLD_DEFAULT); 1876 def = symlook_default(name, hash, obj, &defobj, true); 1877 } 1878 } else { 1879 DoneList donelist; 1880 1881 if ((obj = dlcheck(handle)) == NULL) { 1882 rlock_release(); 1883 return NULL; 1884 } 1885 1886 donelist_init(&donelist); 1887 if (obj->mainprog) { 1888 /* Search main program and all libraries loaded by it. */ 1889 def = symlook_list(name, hash, &list_main, &defobj, true, 1890 &donelist); 1891 } else { 1892 Needed_Entry fake; 1893 1894 /* Search the given object and its needed objects. */ 1895 fake.next = NULL; 1896 fake.obj = (Obj_Entry *)obj; 1897 fake.name = 0; 1898 def = symlook_needed(name, hash, &fake, &defobj, true, 1899 &donelist); 1900 } 1901 } 1902 1903 if (def != NULL) { 1904 rlock_release(); 1905 return defobj->relocbase + def->st_value; 1906 } 1907 1908 _rtld_error("Undefined symbol \"%s\"", name); 1909 rlock_release(); 1910 return NULL; 1911 } 1912 1913 int 1914 dladdr(const void *addr, Dl_info *info) 1915 { 1916 const Obj_Entry *obj; 1917 const Elf_Sym *def; 1918 void *symbol_addr; 1919 unsigned long symoffset; 1920 1921 rlock_acquire(); 1922 obj = obj_from_addr(addr); 1923 if (obj == NULL) { 1924 _rtld_error("No shared object contains address"); 1925 rlock_release(); 1926 return 0; 1927 } 1928 info->dli_fname = obj->path; 1929 info->dli_fbase = obj->mapbase; 1930 info->dli_saddr = (void *)0; 1931 info->dli_sname = NULL; 1932 1933 /* 1934 * Walk the symbol list looking for the symbol whose address is 1935 * closest to the address sent in. 1936 */ 1937 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1938 def = obj->symtab + symoffset; 1939 1940 /* 1941 * For skip the symbol if st_shndx is either SHN_UNDEF or 1942 * SHN_COMMON. 1943 */ 1944 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1945 continue; 1946 1947 /* 1948 * If the symbol is greater than the specified address, or if it 1949 * is further away from addr than the current nearest symbol, 1950 * then reject it. 1951 */ 1952 symbol_addr = obj->relocbase + def->st_value; 1953 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1954 continue; 1955 1956 /* Update our idea of the nearest symbol. */ 1957 info->dli_sname = obj->strtab + def->st_name; 1958 info->dli_saddr = symbol_addr; 1959 1960 /* Exact match? */ 1961 if (info->dli_saddr == addr) 1962 break; 1963 } 1964 rlock_release(); 1965 return 1; 1966 } 1967 1968 int 1969 dlinfo(void *handle, int request, void *p) 1970 { 1971 const Obj_Entry *obj; 1972 int error; 1973 1974 rlock_acquire(); 1975 1976 if (handle == NULL || handle == RTLD_SELF) { 1977 void *retaddr; 1978 1979 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1980 if ((obj = obj_from_addr(retaddr)) == NULL) 1981 _rtld_error("Cannot determine caller's shared object"); 1982 } else 1983 obj = dlcheck(handle); 1984 1985 if (obj == NULL) { 1986 rlock_release(); 1987 return (-1); 1988 } 1989 1990 error = 0; 1991 switch (request) { 1992 case RTLD_DI_LINKMAP: 1993 *((struct link_map const **)p) = &obj->linkmap; 1994 break; 1995 case RTLD_DI_ORIGIN: 1996 error = rtld_dirname(obj->path, p); 1997 break; 1998 1999 case RTLD_DI_SERINFOSIZE: 2000 case RTLD_DI_SERINFO: 2001 error = do_search_info(obj, request, (struct dl_serinfo *)p); 2002 break; 2003 2004 default: 2005 _rtld_error("Invalid request %d passed to dlinfo()", request); 2006 error = -1; 2007 } 2008 2009 rlock_release(); 2010 2011 return (error); 2012 } 2013 2014 struct fill_search_info_args { 2015 int request; 2016 unsigned int flags; 2017 Dl_serinfo *serinfo; 2018 Dl_serpath *serpath; 2019 char *strspace; 2020 }; 2021 2022 static void * 2023 fill_search_info(const char *dir, size_t dirlen, void *param) 2024 { 2025 struct fill_search_info_args *arg; 2026 2027 arg = param; 2028 2029 if (arg->request == RTLD_DI_SERINFOSIZE) { 2030 arg->serinfo->dls_cnt ++; 2031 arg->serinfo->dls_size += dirlen + 1; 2032 } else { 2033 struct dl_serpath *s_entry; 2034 2035 s_entry = arg->serpath; 2036 s_entry->dls_name = arg->strspace; 2037 s_entry->dls_flags = arg->flags; 2038 2039 strncpy(arg->strspace, dir, dirlen); 2040 arg->strspace[dirlen] = '\0'; 2041 2042 arg->strspace += dirlen + 1; 2043 arg->serpath++; 2044 } 2045 2046 return (NULL); 2047 } 2048 2049 static int 2050 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info) 2051 { 2052 struct dl_serinfo _info; 2053 struct fill_search_info_args args; 2054 2055 args.request = RTLD_DI_SERINFOSIZE; 2056 args.serinfo = &_info; 2057 2058 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath); 2059 _info.dls_cnt = 0; 2060 2061 path_enumerate(ld_library_path, fill_search_info, &args); 2062 path_enumerate(obj->rpath, fill_search_info, &args); 2063 path_enumerate(gethints(), fill_search_info, &args); 2064 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args); 2065 2066 2067 if (request == RTLD_DI_SERINFOSIZE) { 2068 info->dls_size = _info.dls_size; 2069 info->dls_cnt = _info.dls_cnt; 2070 return (0); 2071 } 2072 2073 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) { 2074 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()"); 2075 return (-1); 2076 } 2077 2078 args.request = RTLD_DI_SERINFO; 2079 args.serinfo = info; 2080 args.serpath = &info->dls_serpath[0]; 2081 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt]; 2082 2083 args.flags = LA_SER_LIBPATH; 2084 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL) 2085 return (-1); 2086 2087 args.flags = LA_SER_RUNPATH; 2088 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL) 2089 return (-1); 2090 2091 args.flags = LA_SER_CONFIG; 2092 if (path_enumerate(gethints(), fill_search_info, &args) != NULL) 2093 return (-1); 2094 2095 args.flags = LA_SER_DEFAULT; 2096 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL) 2097 return (-1); 2098 return (0); 2099 } 2100 2101 static int 2102 rtld_dirname(const char *path, char *bname) 2103 { 2104 const char *endp; 2105 2106 /* Empty or NULL string gets treated as "." */ 2107 if (path == NULL || *path == '\0') { 2108 bname[0] = '.'; 2109 bname[1] = '\0'; 2110 return (0); 2111 } 2112 2113 /* Strip trailing slashes */ 2114 endp = path + strlen(path) - 1; 2115 while (endp > path && *endp == '/') 2116 endp--; 2117 2118 /* Find the start of the dir */ 2119 while (endp > path && *endp != '/') 2120 endp--; 2121 2122 /* Either the dir is "/" or there are no slashes */ 2123 if (endp == path) { 2124 bname[0] = *endp == '/' ? '/' : '.'; 2125 bname[1] = '\0'; 2126 return (0); 2127 } else { 2128 do { 2129 endp--; 2130 } while (endp > path && *endp == '/'); 2131 } 2132 2133 if (endp - path + 2 > PATH_MAX) 2134 { 2135 _rtld_error("Filename is too long: %s", path); 2136 return(-1); 2137 } 2138 2139 strncpy(bname, path, endp - path + 1); 2140 bname[endp - path + 1] = '\0'; 2141 return (0); 2142 } 2143 2144 static void 2145 linkmap_add(Obj_Entry *obj) 2146 { 2147 struct link_map *l = &obj->linkmap; 2148 struct link_map *prev; 2149 2150 obj->linkmap.l_name = obj->path; 2151 obj->linkmap.l_addr = obj->mapbase; 2152 obj->linkmap.l_ld = obj->dynamic; 2153 #ifdef __mips__ 2154 /* GDB needs load offset on MIPS to use the symbols */ 2155 obj->linkmap.l_offs = obj->relocbase; 2156 #endif 2157 2158 if (r_debug.r_map == NULL) { 2159 r_debug.r_map = l; 2160 return; 2161 } 2162 2163 /* 2164 * Scan to the end of the list, but not past the entry for the 2165 * dynamic linker, which we want to keep at the very end. 2166 */ 2167 for (prev = r_debug.r_map; 2168 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 2169 prev = prev->l_next) 2170 ; 2171 2172 /* Link in the new entry. */ 2173 l->l_prev = prev; 2174 l->l_next = prev->l_next; 2175 if (l->l_next != NULL) 2176 l->l_next->l_prev = l; 2177 prev->l_next = l; 2178 } 2179 2180 static void 2181 linkmap_delete(Obj_Entry *obj) 2182 { 2183 struct link_map *l = &obj->linkmap; 2184 2185 if (l->l_prev == NULL) { 2186 if ((r_debug.r_map = l->l_next) != NULL) 2187 l->l_next->l_prev = NULL; 2188 return; 2189 } 2190 2191 if ((l->l_prev->l_next = l->l_next) != NULL) 2192 l->l_next->l_prev = l->l_prev; 2193 } 2194 2195 /* 2196 * Function for the debugger to set a breakpoint on to gain control. 2197 * 2198 * The two parameters allow the debugger to easily find and determine 2199 * what the runtime loader is doing and to whom it is doing it. 2200 * 2201 * When the loadhook trap is hit (r_debug_state, set at program 2202 * initialization), the arguments can be found on the stack: 2203 * 2204 * +8 struct link_map *m 2205 * +4 struct r_debug *rd 2206 * +0 RetAddr 2207 */ 2208 void 2209 r_debug_state(struct r_debug* rd, struct link_map *m) 2210 { 2211 } 2212 2213 /* 2214 * Get address of the pointer variable in the main program. 2215 */ 2216 static const void ** 2217 get_program_var_addr(const char *name) 2218 { 2219 const Obj_Entry *obj; 2220 unsigned long hash; 2221 2222 hash = elf_hash(name); 2223 for (obj = obj_main; obj != NULL; obj = obj->next) { 2224 const Elf_Sym *def; 2225 2226 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 2227 const void **addr; 2228 2229 addr = (const void **)(obj->relocbase + def->st_value); 2230 return addr; 2231 } 2232 } 2233 return NULL; 2234 } 2235 2236 /* 2237 * Set a pointer variable in the main program to the given value. This 2238 * is used to set key variables such as "environ" before any of the 2239 * init functions are called. 2240 */ 2241 static void 2242 set_program_var(const char *name, const void *value) 2243 { 2244 const void **addr; 2245 2246 if ((addr = get_program_var_addr(name)) != NULL) { 2247 dbg("\"%s\": *%p <-- %p", name, addr, value); 2248 *addr = value; 2249 } 2250 } 2251 2252 /* 2253 * This is a special version of getenv which is far more efficient 2254 * at finding LD_ environment vars. 2255 */ 2256 static 2257 const char * 2258 _getenv_ld(const char *id) 2259 { 2260 const char *envp; 2261 int i, j; 2262 int idlen = strlen(id); 2263 2264 if (ld_index == LD_ARY_CACHE) 2265 return(getenv(id)); 2266 if (ld_index == 0) { 2267 for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) { 2268 if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_') 2269 ld_ary[j++] = envp; 2270 } 2271 if (j == 0) 2272 ld_ary[j++] = ""; 2273 ld_index = j; 2274 } 2275 for (i = ld_index - 1; i >= 0; --i) { 2276 if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=') 2277 return(ld_ary[i] + idlen + 1); 2278 } 2279 return(NULL); 2280 } 2281 2282 /* 2283 * Given a symbol name in a referencing object, find the corresponding 2284 * definition of the symbol. Returns a pointer to the symbol, or NULL if 2285 * no definition was found. Returns a pointer to the Obj_Entry of the 2286 * defining object via the reference parameter DEFOBJ_OUT. 2287 */ 2288 static const Elf_Sym * 2289 symlook_default(const char *name, unsigned long hash, 2290 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) 2291 { 2292 DoneList donelist; 2293 const Elf_Sym *def; 2294 const Elf_Sym *symp; 2295 const Obj_Entry *obj; 2296 const Obj_Entry *defobj; 2297 const Objlist_Entry *elm; 2298 def = NULL; 2299 defobj = NULL; 2300 donelist_init(&donelist); 2301 2302 /* Look first in the referencing object if linked symbolically. */ 2303 if (refobj->symbolic && !donelist_check(&donelist, refobj)) { 2304 symp = symlook_obj(name, hash, refobj, in_plt); 2305 if (symp != NULL) { 2306 def = symp; 2307 defobj = refobj; 2308 } 2309 } 2310 2311 /* Search all objects loaded at program start up. */ 2312 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2313 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); 2314 if (symp != NULL && 2315 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2316 def = symp; 2317 defobj = obj; 2318 } 2319 } 2320 2321 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */ 2322 STAILQ_FOREACH(elm, &list_global, link) { 2323 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2324 break; 2325 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2326 &donelist); 2327 if (symp != NULL && 2328 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2329 def = symp; 2330 defobj = obj; 2331 } 2332 } 2333 2334 /* Search all dlopened DAGs containing the referencing object. */ 2335 STAILQ_FOREACH(elm, &refobj->dldags, link) { 2336 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 2337 break; 2338 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 2339 &donelist); 2340 if (symp != NULL && 2341 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 2342 def = symp; 2343 defobj = obj; 2344 } 2345 } 2346 2347 /* 2348 * Search the dynamic linker itself, and possibly resolve the 2349 * symbol from there. This is how the application links to 2350 * dynamic linker services such as dlopen. Only the values listed 2351 * in the "exports" array can be resolved from the dynamic linker. 2352 */ 2353 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 2354 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 2355 if (symp != NULL && is_exported(symp)) { 2356 def = symp; 2357 defobj = &obj_rtld; 2358 } 2359 } 2360 2361 if (def != NULL) 2362 *defobj_out = defobj; 2363 return def; 2364 } 2365 2366 static const Elf_Sym * 2367 symlook_list(const char *name, unsigned long hash, const Objlist *objlist, 2368 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 2369 { 2370 const Elf_Sym *symp; 2371 const Elf_Sym *def; 2372 const Obj_Entry *defobj; 2373 const Objlist_Entry *elm; 2374 2375 def = NULL; 2376 defobj = NULL; 2377 STAILQ_FOREACH(elm, objlist, link) { 2378 if (donelist_check(dlp, elm->obj)) 2379 continue; 2380 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 2381 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 2382 def = symp; 2383 defobj = elm->obj; 2384 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 2385 break; 2386 } 2387 } 2388 } 2389 if (def != NULL) 2390 *defobj_out = defobj; 2391 return def; 2392 } 2393 2394 /* 2395 * Search the symbol table of a shared object and all objects needed 2396 * by it for a symbol of the given name. Search order is 2397 * breadth-first. Returns a pointer to the symbol, or NULL if no 2398 * definition was found. 2399 */ 2400 static const Elf_Sym * 2401 symlook_needed(const char *name, unsigned long hash, const Needed_Entry *needed, 2402 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 2403 { 2404 const Elf_Sym *def, *def_w; 2405 const Needed_Entry *n; 2406 const Obj_Entry *obj, *defobj, *defobj1; 2407 2408 def = def_w = NULL; 2409 defobj = NULL; 2410 for (n = needed; n != NULL; n = n->next) { 2411 if ((obj = n->obj) == NULL || 2412 donelist_check(dlp, obj) || 2413 (def = symlook_obj(name, hash, obj, in_plt)) == NULL) 2414 continue; 2415 defobj = obj; 2416 if (ELF_ST_BIND(def->st_info) != STB_WEAK) { 2417 *defobj_out = defobj; 2418 return (def); 2419 } 2420 } 2421 /* 2422 * There we come when either symbol definition is not found in 2423 * directly needed objects, or found symbol is weak. 2424 */ 2425 for (n = needed; n != NULL; n = n->next) { 2426 if ((obj = n->obj) == NULL) 2427 continue; 2428 def_w = symlook_needed(name, hash, obj->needed, &defobj1, 2429 in_plt, dlp); 2430 if (def_w == NULL) 2431 continue; 2432 if (def == NULL || ELF_ST_BIND(def_w->st_info) != STB_WEAK) { 2433 def = def_w; 2434 defobj = defobj1; 2435 } 2436 if (ELF_ST_BIND(def_w->st_info) != STB_WEAK) 2437 break; 2438 } 2439 if (def != NULL) 2440 *defobj_out = defobj; 2441 return def; 2442 } 2443 2444 /* 2445 * Search the symbol table of a single shared object for a symbol of 2446 * the given name. Returns a pointer to the symbol, or NULL if no 2447 * definition was found. 2448 * 2449 * The symbol's hash value is passed in for efficiency reasons; that 2450 * eliminates many recomputations of the hash value. 2451 */ 2452 const Elf_Sym * 2453 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 2454 bool in_plt) 2455 { 2456 if (obj->buckets != NULL) { 2457 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 2458 2459 while (symnum != STN_UNDEF) { 2460 const Elf_Sym *symp; 2461 const char *strp; 2462 2463 if (symnum >= obj->nchains) 2464 return NULL; /* Bad object */ 2465 symp = obj->symtab + symnum; 2466 strp = obj->strtab + symp->st_name; 2467 2468 if (name[0] == strp[0] && strcmp(name, strp) == 0) 2469 return symp->st_shndx != SHN_UNDEF || 2470 (!in_plt && symp->st_value != 0 && 2471 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 2472 2473 symnum = obj->chains[symnum]; 2474 } 2475 } 2476 return NULL; 2477 } 2478 2479 static void 2480 trace_loaded_objects(Obj_Entry *obj) 2481 { 2482 const char *fmt1, *fmt2, *fmt, *main_local; 2483 int c; 2484 2485 if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 2486 main_local = ""; 2487 2488 if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 2489 fmt1 = "\t%o => %p (%x)\n"; 2490 2491 if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 2492 fmt2 = "\t%o (%x)\n"; 2493 2494 for (; obj; obj = obj->next) { 2495 Needed_Entry *needed; 2496 char *name, *path; 2497 bool is_lib; 2498 2499 for (needed = obj->needed; needed; needed = needed->next) { 2500 if (needed->obj != NULL) { 2501 if (needed->obj->traced) 2502 continue; 2503 needed->obj->traced = true; 2504 path = needed->obj->path; 2505 } else 2506 path = "not found"; 2507 2508 name = (char *)obj->strtab + needed->name; 2509 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 2510 2511 fmt = is_lib ? fmt1 : fmt2; 2512 while ((c = *fmt++) != '\0') { 2513 switch (c) { 2514 default: 2515 putchar(c); 2516 continue; 2517 case '\\': 2518 switch (c = *fmt) { 2519 case '\0': 2520 continue; 2521 case 'n': 2522 putchar('\n'); 2523 break; 2524 case 't': 2525 putchar('\t'); 2526 break; 2527 } 2528 break; 2529 case '%': 2530 switch (c = *fmt) { 2531 case '\0': 2532 continue; 2533 case '%': 2534 default: 2535 putchar(c); 2536 break; 2537 case 'A': 2538 printf("%s", main_local); 2539 break; 2540 case 'a': 2541 printf("%s", obj_main->path); 2542 break; 2543 case 'o': 2544 printf("%s", name); 2545 break; 2546 #if 0 2547 case 'm': 2548 printf("%d", sodp->sod_major); 2549 break; 2550 case 'n': 2551 printf("%d", sodp->sod_minor); 2552 break; 2553 #endif 2554 case 'p': 2555 printf("%s", path); 2556 break; 2557 case 'x': 2558 printf("%p", needed->obj ? needed->obj->mapbase : 0); 2559 break; 2560 } 2561 break; 2562 } 2563 ++fmt; 2564 } 2565 } 2566 } 2567 } 2568 2569 /* 2570 * Unload a dlopened object and its dependencies from memory and from 2571 * our data structures. It is assumed that the DAG rooted in the 2572 * object has already been unreferenced, and that the object has a 2573 * reference count of 0. 2574 */ 2575 static void 2576 unload_object(Obj_Entry *root) 2577 { 2578 Obj_Entry *obj; 2579 Obj_Entry **linkp; 2580 2581 assert(root->refcount == 0); 2582 2583 /* 2584 * Pass over the DAG removing unreferenced objects from 2585 * appropriate lists. 2586 */ 2587 unlink_object(root); 2588 2589 /* Unmap all objects that are no longer referenced. */ 2590 linkp = &obj_list->next; 2591 while ((obj = *linkp) != NULL) { 2592 if (obj->refcount == 0) { 2593 dbg("unloading \"%s\"", obj->path); 2594 munmap(obj->mapbase, obj->mapsize); 2595 linkmap_delete(obj); 2596 *linkp = obj->next; 2597 obj_count--; 2598 obj_free(obj); 2599 } else 2600 linkp = &obj->next; 2601 } 2602 obj_tail = linkp; 2603 } 2604 2605 static void 2606 unlink_object(Obj_Entry *root) 2607 { 2608 const Needed_Entry *needed; 2609 Objlist_Entry *elm; 2610 2611 if (root->refcount == 0) { 2612 /* Remove the object from the RTLD_GLOBAL list. */ 2613 objlist_remove(&list_global, root); 2614 2615 /* Remove the object from all objects' DAG lists. */ 2616 STAILQ_FOREACH(elm, &root->dagmembers , link) 2617 objlist_remove(&elm->obj->dldags, root); 2618 } 2619 2620 for (needed = root->needed; needed != NULL; needed = needed->next) 2621 if (needed->obj != NULL) 2622 unlink_object(needed->obj); 2623 } 2624 2625 static void 2626 unref_dag(Obj_Entry *root) 2627 { 2628 const Needed_Entry *needed; 2629 2630 if (root->refcount == 0) 2631 return; 2632 root->refcount--; 2633 if (root->refcount == 0) 2634 for (needed = root->needed; needed != NULL; needed = needed->next) 2635 if (needed->obj != NULL) 2636 unref_dag(needed->obj); 2637 } 2638 2639 /* 2640 * Common code for MD __tls_get_addr(). 2641 */ 2642 void * 2643 tls_get_addr_common(void **dtvp, int index, size_t offset) 2644 { 2645 Elf_Addr* dtv = *dtvp; 2646 2647 /* Check dtv generation in case new modules have arrived */ 2648 if (dtv[0] != tls_dtv_generation) { 2649 Elf_Addr* newdtv; 2650 int to_copy; 2651 2652 wlock_acquire(); 2653 2654 newdtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr)); 2655 to_copy = dtv[1]; 2656 if (to_copy > tls_max_index) 2657 to_copy = tls_max_index; 2658 memcpy(&newdtv[2], &dtv[2], to_copy * sizeof(Elf_Addr)); 2659 newdtv[0] = tls_dtv_generation; 2660 newdtv[1] = tls_max_index; 2661 free(dtv); 2662 *dtvp = newdtv; 2663 2664 wlock_release(); 2665 } 2666 2667 /* Dynamically allocate module TLS if necessary */ 2668 if (!dtv[index + 1]) { 2669 /* XXX 2670 * here we should avoid to be re-entered by signal handler 2671 * code, I assume wlock_acquire will masked all signals, 2672 * otherwise there is race and dead lock thread itself. 2673 */ 2674 wlock_acquire(); 2675 if (!dtv[index + 1]) 2676 dtv[index + 1] = (Elf_Addr)allocate_module_tls(index); 2677 wlock_release(); 2678 } 2679 2680 return (void*) (dtv[index + 1] + offset); 2681 } 2682 2683 #if defined(RTLD_STATIC_TLS_VARIANT_II) 2684 2685 /* 2686 * Allocate the static TLS area. Return a pointer to the TCB. The 2687 * static area is based on negative offsets relative to the tcb. 2688 * 2689 * The TCB contains an errno pointer for the system call layer, but because 2690 * we are the RTLD we really have no idea how the caller was compiled so 2691 * the information has to be passed in. errno can either be: 2692 * 2693 * type 0 errno is a simple non-TLS global pointer. 2694 * (special case for e.g. libc_rtld) 2695 * type 1 errno accessed by GOT entry (dynamically linked programs) 2696 * type 2 errno accessed by %gs:OFFSET (statically linked programs) 2697 */ 2698 struct tls_tcb * 2699 allocate_tls(Obj_Entry *objs) 2700 { 2701 Obj_Entry *obj; 2702 size_t data_size; 2703 size_t dtv_size; 2704 struct tls_tcb *tcb; 2705 Elf_Addr *dtv; 2706 Elf_Addr addr; 2707 2708 /* 2709 * Allocate the new TCB. static TLS storage is placed just before the 2710 * TCB to support the %gs:OFFSET (negative offset) model. 2711 */ 2712 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) & 2713 ~RTLD_STATIC_TLS_ALIGN_MASK; 2714 tcb = malloc(data_size + sizeof(*tcb)); 2715 tcb = (void *)((char *)tcb + data_size); /* actual tcb location */ 2716 2717 dtv_size = (tls_max_index + 2) * sizeof(Elf_Addr); 2718 dtv = malloc(dtv_size); 2719 bzero(dtv, dtv_size); 2720 2721 #ifdef RTLD_TCB_HAS_SELF_POINTER 2722 tcb->tcb_self = tcb; 2723 #endif 2724 tcb->tcb_dtv = dtv; 2725 tcb->tcb_pthread = NULL; 2726 2727 dtv[0] = tls_dtv_generation; 2728 dtv[1] = tls_max_index; 2729 2730 for (obj = objs; obj; obj = obj->next) { 2731 if (obj->tlsoffset) { 2732 addr = (Elf_Addr)tcb - obj->tlsoffset; 2733 memset((void *)(addr + obj->tlsinitsize), 2734 0, obj->tlssize - obj->tlsinitsize); 2735 if (obj->tlsinit) 2736 memcpy((void*) addr, obj->tlsinit, obj->tlsinitsize); 2737 dtv[obj->tlsindex + 1] = addr; 2738 } 2739 } 2740 return(tcb); 2741 } 2742 2743 void 2744 free_tls(struct tls_tcb *tcb) 2745 { 2746 Elf_Addr *dtv; 2747 int dtv_size, i; 2748 Elf_Addr tls_start, tls_end; 2749 size_t data_size; 2750 2751 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) & 2752 ~RTLD_STATIC_TLS_ALIGN_MASK; 2753 dtv = tcb->tcb_dtv; 2754 dtv_size = dtv[1]; 2755 tls_end = (Elf_Addr)tcb; 2756 tls_start = (Elf_Addr)tcb - data_size; 2757 for (i = 0; i < dtv_size; i++) { 2758 if (dtv[i+2] != NULL && (dtv[i+2] < tls_start || dtv[i+2] > tls_end)) { 2759 free((void *)dtv[i+2]); 2760 } 2761 } 2762 free((void *)tls_start); 2763 } 2764 2765 #else 2766 #error "Unsupported TLS layout" 2767 #endif 2768 2769 /* 2770 * Allocate TLS block for module with given index. 2771 */ 2772 void * 2773 allocate_module_tls(int index) 2774 { 2775 Obj_Entry* obj; 2776 char* p; 2777 2778 for (obj = obj_list; obj; obj = obj->next) { 2779 if (obj->tlsindex == index) 2780 break; 2781 } 2782 if (!obj) { 2783 _rtld_error("Can't find module with TLS index %d", index); 2784 die(); 2785 } 2786 2787 p = malloc(obj->tlssize); 2788 memcpy(p, obj->tlsinit, obj->tlsinitsize); 2789 memset(p + obj->tlsinitsize, 0, obj->tlssize - obj->tlsinitsize); 2790 2791 return p; 2792 } 2793 2794 bool 2795 allocate_tls_offset(Obj_Entry *obj) 2796 { 2797 size_t off; 2798 2799 if (obj->tls_done) 2800 return true; 2801 2802 if (obj->tlssize == 0) { 2803 obj->tls_done = true; 2804 return true; 2805 } 2806 2807 if (obj->tlsindex == 1) 2808 off = calculate_first_tls_offset(obj->tlssize, obj->tlsalign); 2809 else 2810 off = calculate_tls_offset(tls_last_offset, tls_last_size, 2811 obj->tlssize, obj->tlsalign); 2812 2813 /* 2814 * If we have already fixed the size of the static TLS block, we 2815 * must stay within that size. When allocating the static TLS, we 2816 * leave a small amount of space spare to be used for dynamically 2817 * loading modules which use static TLS. 2818 */ 2819 if (tls_static_space) { 2820 if (calculate_tls_end(off, obj->tlssize) > tls_static_space) 2821 return false; 2822 } 2823 2824 tls_last_offset = obj->tlsoffset = off; 2825 tls_last_size = obj->tlssize; 2826 obj->tls_done = true; 2827 2828 return true; 2829 } 2830 2831 void 2832 free_tls_offset(Obj_Entry *obj) 2833 { 2834 #ifdef RTLD_STATIC_TLS_VARIANT_II 2835 /* 2836 * If we were the last thing to allocate out of the static TLS 2837 * block, we give our space back to the 'allocator'. This is a 2838 * simplistic workaround to allow libGL.so.1 to be loaded and 2839 * unloaded multiple times. We only handle the Variant II 2840 * mechanism for now - this really needs a proper allocator. 2841 */ 2842 if (calculate_tls_end(obj->tlsoffset, obj->tlssize) 2843 == calculate_tls_end(tls_last_offset, tls_last_size)) { 2844 tls_last_offset -= obj->tlssize; 2845 tls_last_size = 0; 2846 } 2847 #endif 2848 } 2849 2850 struct tls_tcb * 2851 _rtld_allocate_tls(void) 2852 { 2853 struct tls_tcb *new_tcb; 2854 2855 wlock_acquire(); 2856 new_tcb = allocate_tls(obj_list); 2857 wlock_release(); 2858 2859 return (new_tcb); 2860 } 2861 2862 void 2863 _rtld_free_tls(struct tls_tcb *tcb) 2864 { 2865 wlock_acquire(); 2866 free_tls(tcb); 2867 wlock_release(); 2868 } 2869 2870