rtld.c revision 85004
1169689Skan/*- 2169689Skan * Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra. 3169689Skan * All rights reserved. 4169689Skan * 5169689Skan * Redistribution and use in source and binary forms, with or without 6169689Skan * modification, are permitted provided that the following conditions 7169689Skan * are met: 8169689Skan * 1. Redistributions of source code must retain the above copyright 9169689Skan * notice, this list of conditions and the following disclaimer. 10169689Skan * 2. Redistributions in binary form must reproduce the above copyright 11169689Skan * notice, this list of conditions and the following disclaimer in the 12169689Skan * documentation and/or other materials provided with the distribution. 13169689Skan * 14169689Skan * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15169689Skan * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16169689Skan * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17169689Skan * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18169689Skan * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19169689Skan * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20169689Skan * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21169689Skan * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22169689Skan * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23169689Skan * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24169689Skan * 25169689Skan * $FreeBSD: head/libexec/rtld-elf/rtld.c 85004 2001-10-15 18:48:42Z dfr $ 26 */ 27 28/* 29 * Dynamic linker for ELF. 30 * 31 * John Polstra <jdp@polstra.com>. 32 */ 33 34#ifndef __GNUC__ 35#error "GCC is needed to compile this file" 36#endif 37 38#include <sys/param.h> 39#include <sys/mman.h> 40#include <sys/stat.h> 41 42#include <dlfcn.h> 43#include <err.h> 44#include <errno.h> 45#include <fcntl.h> 46#include <stdarg.h> 47#include <stdio.h> 48#include <stdlib.h> 49#include <string.h> 50#include <unistd.h> 51 52#include "debug.h" 53#include "rtld.h" 54 55#define END_SYM "_end" 56#define PATH_RTLD "/usr/libexec/ld-elf.so.1" 57 58/* Types. */ 59typedef void (*func_ptr_type)(); 60 61/* 62 * This structure provides a reentrant way to keep a list of objects and 63 * check which ones have already been processed in some way. 64 */ 65typedef struct Struct_DoneList { 66 const Obj_Entry **objs; /* Array of object pointers */ 67 unsigned int num_alloc; /* Allocated size of the array */ 68 unsigned int num_used; /* Number of array slots used */ 69} DoneList; 70 71/* 72 * Function declarations. 73 */ 74static const char *basename(const char *); 75static void die(void); 76static void digest_dynamic(Obj_Entry *); 77static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *); 78static Obj_Entry *dlcheck(void *); 79static bool donelist_check(DoneList *, const Obj_Entry *); 80static void errmsg_restore(char *); 81static char *errmsg_save(void); 82static char *find_library(const char *, const Obj_Entry *); 83static const char *gethints(void); 84static void init_dag(Obj_Entry *); 85static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *); 86static void init_rtld(caddr_t); 87static void initlist_add_neededs(Needed_Entry *needed, Objlist *list); 88static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, 89 Objlist *list); 90static bool is_exported(const Elf_Sym *); 91static void linkmap_add(Obj_Entry *); 92static void linkmap_delete(Obj_Entry *); 93static int load_needed_objects(Obj_Entry *); 94static int load_preload_objects(void); 95static Obj_Entry *load_object(char *); 96static void lock_check(void); 97static Obj_Entry *obj_from_addr(const void *); 98static void objlist_call_fini(Objlist *); 99static void objlist_call_init(Objlist *); 100static void objlist_clear(Objlist *); 101static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *); 102static void objlist_init(Objlist *); 103static void objlist_push_head(Objlist *, Obj_Entry *); 104static void objlist_push_tail(Objlist *, Obj_Entry *); 105static void objlist_remove(Objlist *, Obj_Entry *); 106static void objlist_remove_unref(Objlist *); 107static int relocate_objects(Obj_Entry *, bool); 108static void rtld_exit(void); 109static char *search_library_path(const char *, const char *); 110static void set_program_var(const char *, const void *); 111static const Elf_Sym *symlook_default(const char *, unsigned long hash, 112 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt); 113static const Elf_Sym *symlook_list(const char *, unsigned long, 114 Objlist *, const Obj_Entry **, bool in_plt, DoneList *); 115static void trace_loaded_objects(Obj_Entry *obj); 116static void unload_object(Obj_Entry *); 117static void unref_dag(Obj_Entry *); 118 119void r_debug_state(struct r_debug*, struct link_map*); 120void xprintf(const char *, ...); 121 122/* 123 * Data declarations. 124 */ 125static char *error_message; /* Message for dlerror(), or NULL */ 126struct r_debug r_debug; /* for GDB; */ 127static bool trust; /* False for setuid and setgid programs */ 128static char *ld_bind_now; /* Environment variable for immediate binding */ 129static char *ld_debug; /* Environment variable for debugging */ 130static char *ld_library_path; /* Environment variable for search path */ 131static char *ld_preload; /* Environment variable for libraries to 132 load first */ 133static char *ld_tracing; /* Called from ldd to print libs */ 134static Obj_Entry *obj_list; /* Head of linked list of shared objects */ 135static Obj_Entry **obj_tail; /* Link field of last object in list */ 136static Obj_Entry *obj_main; /* The main program shared object */ 137static Obj_Entry obj_rtld; /* The dynamic linker shared object */ 138static unsigned int obj_count; /* Number of objects in obj_list */ 139 140static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ 141 STAILQ_HEAD_INITIALIZER(list_global); 142static Objlist list_main = /* Objects loaded at program startup */ 143 STAILQ_HEAD_INITIALIZER(list_main); 144static Objlist list_fini = /* Objects needing fini() calls */ 145 STAILQ_HEAD_INITIALIZER(list_fini); 146 147static LockInfo lockinfo; 148 149static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ 150 151#define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); 152 153extern Elf_Dyn _DYNAMIC; 154#pragma weak _DYNAMIC 155 156/* 157 * These are the functions the dynamic linker exports to application 158 * programs. They are the only symbols the dynamic linker is willing 159 * to export from itself. 160 */ 161static func_ptr_type exports[] = { 162 (func_ptr_type) &_rtld_error, 163 (func_ptr_type) &dlclose, 164 (func_ptr_type) &dlerror, 165 (func_ptr_type) &dlopen, 166 (func_ptr_type) &dlsym, 167 (func_ptr_type) &dladdr, 168 (func_ptr_type) &dllockinit, 169 NULL 170}; 171 172/* 173 * Global declarations normally provided by crt1. The dynamic linker is 174 * not built with crt1, so we have to provide them ourselves. 175 */ 176char *__progname; 177char **environ; 178 179/* 180 * Fill in a DoneList with an allocation large enough to hold all of 181 * the currently-loaded objects. Keep this as a macro since it calls 182 * alloca and we want that to occur within the scope of the caller. 183 */ 184#define donelist_init(dlp) \ 185 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ 186 assert((dlp)->objs != NULL), \ 187 (dlp)->num_alloc = obj_count, \ 188 (dlp)->num_used = 0) 189 190static __inline void 191rlock_acquire(void) 192{ 193 lockinfo.rlock_acquire(lockinfo.thelock); 194 atomic_incr_int(&lockinfo.rcount); 195 lock_check(); 196} 197 198static __inline void 199wlock_acquire(void) 200{ 201 lockinfo.wlock_acquire(lockinfo.thelock); 202 atomic_incr_int(&lockinfo.wcount); 203 lock_check(); 204} 205 206static __inline void 207rlock_release(void) 208{ 209 atomic_decr_int(&lockinfo.rcount); 210 lockinfo.rlock_release(lockinfo.thelock); 211} 212 213static __inline void 214wlock_release(void) 215{ 216 atomic_decr_int(&lockinfo.wcount); 217 lockinfo.wlock_release(lockinfo.thelock); 218} 219 220/* 221 * Main entry point for dynamic linking. The first argument is the 222 * stack pointer. The stack is expected to be laid out as described 223 * in the SVR4 ABI specification, Intel 386 Processor Supplement. 224 * Specifically, the stack pointer points to a word containing 225 * ARGC. Following that in the stack is a null-terminated sequence 226 * of pointers to argument strings. Then comes a null-terminated 227 * sequence of pointers to environment strings. Finally, there is a 228 * sequence of "auxiliary vector" entries. 229 * 230 * The second argument points to a place to store the dynamic linker's 231 * exit procedure pointer and the third to a place to store the main 232 * program's object. 233 * 234 * The return value is the main program's entry point. 235 */ 236func_ptr_type 237_rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) 238{ 239 Elf_Auxinfo *aux_info[AT_COUNT]; 240 int i; 241 int argc; 242 char **argv; 243 char **env; 244 Elf_Auxinfo *aux; 245 Elf_Auxinfo *auxp; 246 const char *argv0; 247 Obj_Entry *obj; 248 Obj_Entry **preload_tail; 249 Objlist initlist; 250 251 /* 252 * On entry, the dynamic linker itself has not been relocated yet. 253 * Be very careful not to reference any global data until after 254 * init_rtld has returned. It is OK to reference file-scope statics 255 * and string constants, and to call static and global functions. 256 */ 257 258 /* Find the auxiliary vector on the stack. */ 259 argc = *sp++; 260 argv = (char **) sp; 261 sp += argc + 1; /* Skip over arguments and NULL terminator */ 262 env = (char **) sp; 263 while (*sp++ != 0) /* Skip over environment, and NULL terminator */ 264 ; 265 aux = (Elf_Auxinfo *) sp; 266 267 /* Digest the auxiliary vector. */ 268 for (i = 0; i < AT_COUNT; i++) 269 aux_info[i] = NULL; 270 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { 271 if (auxp->a_type < AT_COUNT) 272 aux_info[auxp->a_type] = auxp; 273 } 274 275 /* Initialize and relocate ourselves. */ 276 assert(aux_info[AT_BASE] != NULL); 277 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 278 279 __progname = obj_rtld.path; 280 argv0 = argv[0] != NULL ? argv[0] : "(null)"; 281 environ = env; 282 283 trust = geteuid() == getuid() && getegid() == getgid(); 284 285 ld_bind_now = getenv("LD_BIND_NOW"); 286 if (trust) { 287 ld_debug = getenv("LD_DEBUG"); 288 ld_library_path = getenv("LD_LIBRARY_PATH"); 289 ld_preload = getenv("LD_PRELOAD"); 290 } 291 ld_tracing = getenv("LD_TRACE_LOADED_OBJECTS"); 292 293 if (ld_debug != NULL && *ld_debug != '\0') 294 debug = 1; 295 dbg("%s is initialized, base address = %p", __progname, 296 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); 297 dbg("RTLD dynamic = %p", obj_rtld.dynamic); 298 dbg("RTLD pltgot = %p", obj_rtld.pltgot); 299 300 /* 301 * Load the main program, or process its program header if it is 302 * already loaded. 303 */ 304 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ 305 int fd = aux_info[AT_EXECFD]->a_un.a_val; 306 dbg("loading main program"); 307 obj_main = map_object(fd, argv0, NULL); 308 close(fd); 309 if (obj_main == NULL) 310 die(); 311 } else { /* Main program already loaded. */ 312 const Elf_Phdr *phdr; 313 int phnum; 314 caddr_t entry; 315 316 dbg("processing main program's program header"); 317 assert(aux_info[AT_PHDR] != NULL); 318 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; 319 assert(aux_info[AT_PHNUM] != NULL); 320 phnum = aux_info[AT_PHNUM]->a_un.a_val; 321 assert(aux_info[AT_PHENT] != NULL); 322 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); 323 assert(aux_info[AT_ENTRY] != NULL); 324 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; 325 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) 326 die(); 327 } 328 329 obj_main->path = xstrdup(argv0); 330 obj_main->mainprog = true; 331 332 /* 333 * Get the actual dynamic linker pathname from the executable if 334 * possible. (It should always be possible.) That ensures that 335 * gdb will find the right dynamic linker even if a non-standard 336 * one is being used. 337 */ 338 if (obj_main->interp != NULL && 339 strcmp(obj_main->interp, obj_rtld.path) != 0) { 340 free(obj_rtld.path); 341 obj_rtld.path = xstrdup(obj_main->interp); 342 } 343 344 digest_dynamic(obj_main); 345 346 linkmap_add(obj_main); 347 linkmap_add(&obj_rtld); 348 349 /* Link the main program into the list of objects. */ 350 *obj_tail = obj_main; 351 obj_tail = &obj_main->next; 352 obj_count++; 353 obj_main->refcount++; 354 /* Make sure we don't call the main program's init and fini functions. */ 355 obj_main->init = obj_main->fini = NULL; 356 357 /* Initialize a fake symbol for resolving undefined weak references. */ 358 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); 359 sym_zero.st_shndx = SHN_ABS; 360 361 dbg("loading LD_PRELOAD libraries"); 362 if (load_preload_objects() == -1) 363 die(); 364 preload_tail = obj_tail; 365 366 dbg("loading needed objects"); 367 if (load_needed_objects(obj_main) == -1) 368 die(); 369 370 /* Make a list of all objects loaded at startup. */ 371 for (obj = obj_list; obj != NULL; obj = obj->next) 372 objlist_push_tail(&list_main, obj); 373 374 if (ld_tracing) { /* We're done */ 375 trace_loaded_objects(obj_main); 376 exit(0); 377 } 378 379 if (relocate_objects(obj_main, 380 ld_bind_now != NULL && *ld_bind_now != '\0') == -1) 381 die(); 382 383 dbg("doing copy relocations"); 384 if (do_copy_relocations(obj_main) == -1) 385 die(); 386 387 dbg("initializing key program variables"); 388 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); 389 set_program_var("environ", env); 390 391 dbg("initializing thread locks"); 392 lockdflt_init(&lockinfo); 393 lockinfo.thelock = lockinfo.lock_create(lockinfo.context); 394 395 /* Make a list of init functions to call. */ 396 objlist_init(&initlist); 397 initlist_add_objects(obj_list, preload_tail, &initlist); 398 399 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ 400 401 objlist_call_init(&initlist); 402 wlock_acquire(); 403 objlist_clear(&initlist); 404 wlock_release(); 405 406 dbg("transferring control to program entry point = %p", obj_main->entry); 407 408 /* Return the exit procedure and the program entry point. */ 409 *exit_proc = rtld_exit; 410 *objp = obj_main; 411 return (func_ptr_type) obj_main->entry; 412} 413 414Elf_Addr 415_rtld_bind(Obj_Entry *obj, Elf_Word reloff) 416{ 417 const Elf_Rel *rel; 418 const Elf_Sym *def; 419 const Obj_Entry *defobj; 420 Elf_Addr *where; 421 Elf_Addr target; 422 423 rlock_acquire(); 424 if (obj->pltrel) 425 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); 426 else 427 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); 428 429 where = (Elf_Addr *) (obj->relocbase + rel->r_offset); 430 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); 431 if (def == NULL) 432 die(); 433 434 target = (Elf_Addr)(defobj->relocbase + def->st_value); 435 436 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", 437 defobj->strtab + def->st_name, basename(obj->path), 438 (void *)target, basename(defobj->path)); 439 440 /* 441 * Write the new contents for the jmpslot. Note that depending on 442 * architecture, the value which we need to return back to the 443 * lazy binding trampoline may or may not be the target 444 * address. The value returned from reloc_jmpslot() is the value 445 * that the trampoline needs. 446 */ 447 target = reloc_jmpslot(where, target, defobj); 448 rlock_release(); 449 return target; 450} 451 452/* 453 * Error reporting function. Use it like printf. If formats the message 454 * into a buffer, and sets things up so that the next call to dlerror() 455 * will return the message. 456 */ 457void 458_rtld_error(const char *fmt, ...) 459{ 460 static char buf[512]; 461 va_list ap; 462 463 va_start(ap, fmt); 464 vsnprintf(buf, sizeof buf, fmt, ap); 465 error_message = buf; 466 va_end(ap); 467} 468 469/* 470 * Return a dynamically-allocated copy of the current error message, if any. 471 */ 472static char * 473errmsg_save(void) 474{ 475 return error_message == NULL ? NULL : xstrdup(error_message); 476} 477 478/* 479 * Restore the current error message from a copy which was previously saved 480 * by errmsg_save(). The copy is freed. 481 */ 482static void 483errmsg_restore(char *saved_msg) 484{ 485 if (saved_msg == NULL) 486 error_message = NULL; 487 else { 488 _rtld_error("%s", saved_msg); 489 free(saved_msg); 490 } 491} 492 493static const char * 494basename(const char *name) 495{ 496 const char *p = strrchr(name, '/'); 497 return p != NULL ? p + 1 : name; 498} 499 500static void 501die(void) 502{ 503 const char *msg = dlerror(); 504 505 if (msg == NULL) 506 msg = "Fatal error"; 507 errx(1, "%s", msg); 508} 509 510/* 511 * Process a shared object's DYNAMIC section, and save the important 512 * information in its Obj_Entry structure. 513 */ 514static void 515digest_dynamic(Obj_Entry *obj) 516{ 517 const Elf_Dyn *dynp; 518 Needed_Entry **needed_tail = &obj->needed; 519 const Elf_Dyn *dyn_rpath = NULL; 520 int plttype = DT_REL; 521 522 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { 523 switch (dynp->d_tag) { 524 525 case DT_REL: 526 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); 527 break; 528 529 case DT_RELSZ: 530 obj->relsize = dynp->d_un.d_val; 531 break; 532 533 case DT_RELENT: 534 assert(dynp->d_un.d_val == sizeof(Elf_Rel)); 535 break; 536 537 case DT_JMPREL: 538 obj->pltrel = (const Elf_Rel *) 539 (obj->relocbase + dynp->d_un.d_ptr); 540 break; 541 542 case DT_PLTRELSZ: 543 obj->pltrelsize = dynp->d_un.d_val; 544 break; 545 546 case DT_RELA: 547 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); 548 break; 549 550 case DT_RELASZ: 551 obj->relasize = dynp->d_un.d_val; 552 break; 553 554 case DT_RELAENT: 555 assert(dynp->d_un.d_val == sizeof(Elf_Rela)); 556 break; 557 558 case DT_PLTREL: 559 plttype = dynp->d_un.d_val; 560 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); 561 break; 562 563 case DT_SYMTAB: 564 obj->symtab = (const Elf_Sym *) 565 (obj->relocbase + dynp->d_un.d_ptr); 566 break; 567 568 case DT_SYMENT: 569 assert(dynp->d_un.d_val == sizeof(Elf_Sym)); 570 break; 571 572 case DT_STRTAB: 573 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); 574 break; 575 576 case DT_STRSZ: 577 obj->strsize = dynp->d_un.d_val; 578 break; 579 580 case DT_HASH: 581 { 582 const Elf_Hashelt *hashtab = (const Elf_Hashelt *) 583 (obj->relocbase + dynp->d_un.d_ptr); 584 obj->nbuckets = hashtab[0]; 585 obj->nchains = hashtab[1]; 586 obj->buckets = hashtab + 2; 587 obj->chains = obj->buckets + obj->nbuckets; 588 } 589 break; 590 591 case DT_NEEDED: 592 if (!obj->rtld) { 593 Needed_Entry *nep = NEW(Needed_Entry); 594 nep->name = dynp->d_un.d_val; 595 nep->obj = NULL; 596 nep->next = NULL; 597 598 *needed_tail = nep; 599 needed_tail = &nep->next; 600 } 601 break; 602 603 case DT_PLTGOT: 604 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); 605 break; 606 607 case DT_TEXTREL: 608 obj->textrel = true; 609 break; 610 611 case DT_SYMBOLIC: 612 obj->symbolic = true; 613 break; 614 615 case DT_RPATH: 616 /* 617 * We have to wait until later to process this, because we 618 * might not have gotten the address of the string table yet. 619 */ 620 dyn_rpath = dynp; 621 break; 622 623 case DT_SONAME: 624 /* Not used by the dynamic linker. */ 625 break; 626 627 case DT_INIT: 628 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 629 break; 630 631 case DT_FINI: 632 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); 633 break; 634 635 case DT_DEBUG: 636 /* XXX - not implemented yet */ 637 dbg("Filling in DT_DEBUG entry"); 638 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; 639 break; 640 641 default: 642 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag); 643 break; 644 } 645 } 646 647 obj->traced = false; 648 649 if (plttype == DT_RELA) { 650 obj->pltrela = (const Elf_Rela *) obj->pltrel; 651 obj->pltrel = NULL; 652 obj->pltrelasize = obj->pltrelsize; 653 obj->pltrelsize = 0; 654 } 655 656 if (dyn_rpath != NULL) 657 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; 658} 659 660/* 661 * Process a shared object's program header. This is used only for the 662 * main program, when the kernel has already loaded the main program 663 * into memory before calling the dynamic linker. It creates and 664 * returns an Obj_Entry structure. 665 */ 666static Obj_Entry * 667digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) 668{ 669 Obj_Entry *obj; 670 const Elf_Phdr *phlimit = phdr + phnum; 671 const Elf_Phdr *ph; 672 int nsegs = 0; 673 674 obj = obj_new(); 675 for (ph = phdr; ph < phlimit; ph++) { 676 switch (ph->p_type) { 677 678 case PT_PHDR: 679 if ((const Elf_Phdr *)ph->p_vaddr != phdr) { 680 _rtld_error("%s: invalid PT_PHDR", path); 681 return NULL; 682 } 683 obj->phdr = (const Elf_Phdr *) ph->p_vaddr; 684 obj->phsize = ph->p_memsz; 685 break; 686 687 case PT_INTERP: 688 obj->interp = (const char *) ph->p_vaddr; 689 break; 690 691 case PT_LOAD: 692 if (nsegs >= 2) { 693 _rtld_error("%s: too many PT_LOAD segments", path); 694 return NULL; 695 } 696 if (nsegs == 0) { /* First load segment */ 697 obj->vaddrbase = trunc_page(ph->p_vaddr); 698 obj->mapbase = (caddr_t) obj->vaddrbase; 699 obj->relocbase = obj->mapbase - obj->vaddrbase; 700 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - 701 obj->vaddrbase; 702 } else { /* Last load segment */ 703 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - 704 obj->vaddrbase; 705 } 706 nsegs++; 707 break; 708 709 case PT_DYNAMIC: 710 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; 711 break; 712 } 713 } 714 if (nsegs < 2) { 715 _rtld_error("%s: too few PT_LOAD segments", path); 716 return NULL; 717 } 718 719 obj->entry = entry; 720 return obj; 721} 722 723static Obj_Entry * 724dlcheck(void *handle) 725{ 726 Obj_Entry *obj; 727 728 for (obj = obj_list; obj != NULL; obj = obj->next) 729 if (obj == (Obj_Entry *) handle) 730 break; 731 732 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { 733 _rtld_error("Invalid shared object handle %p", handle); 734 return NULL; 735 } 736 return obj; 737} 738 739/* 740 * If the given object is already in the donelist, return true. Otherwise 741 * add the object to the list and return false. 742 */ 743static bool 744donelist_check(DoneList *dlp, const Obj_Entry *obj) 745{ 746 unsigned int i; 747 748 for (i = 0; i < dlp->num_used; i++) 749 if (dlp->objs[i] == obj) 750 return true; 751 /* 752 * Our donelist allocation should always be sufficient. But if 753 * our threads locking isn't working properly, more shared objects 754 * could have been loaded since we allocated the list. That should 755 * never happen, but we'll handle it properly just in case it does. 756 */ 757 if (dlp->num_used < dlp->num_alloc) 758 dlp->objs[dlp->num_used++] = obj; 759 return false; 760} 761 762/* 763 * Hash function for symbol table lookup. Don't even think about changing 764 * this. It is specified by the System V ABI. 765 */ 766unsigned long 767elf_hash(const char *name) 768{ 769 const unsigned char *p = (const unsigned char *) name; 770 unsigned long h = 0; 771 unsigned long g; 772 773 while (*p != '\0') { 774 h = (h << 4) + *p++; 775 if ((g = h & 0xf0000000) != 0) 776 h ^= g >> 24; 777 h &= ~g; 778 } 779 return h; 780} 781 782/* 783 * Find the library with the given name, and return its full pathname. 784 * The returned string is dynamically allocated. Generates an error 785 * message and returns NULL if the library cannot be found. 786 * 787 * If the second argument is non-NULL, then it refers to an already- 788 * loaded shared object, whose library search path will be searched. 789 * 790 * The search order is: 791 * rpath in the referencing file 792 * LD_LIBRARY_PATH 793 * ldconfig hints 794 * /usr/lib 795 */ 796static char * 797find_library(const char *name, const Obj_Entry *refobj) 798{ 799 char *pathname; 800 801 if (strchr(name, '/') != NULL) { /* Hard coded pathname */ 802 if (name[0] != '/' && !trust) { 803 _rtld_error("Absolute pathname required for shared object \"%s\"", 804 name); 805 return NULL; 806 } 807 return xstrdup(name); 808 } 809 810 dbg(" Searching for \"%s\"", name); 811 812 if ((refobj != NULL && 813 (pathname = search_library_path(name, refobj->rpath)) != NULL) || 814 (pathname = search_library_path(name, ld_library_path)) != NULL || 815 (pathname = search_library_path(name, gethints())) != NULL || 816 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) 817 return pathname; 818 819 _rtld_error("Shared object \"%s\" not found", name); 820 return NULL; 821} 822 823/* 824 * Given a symbol number in a referencing object, find the corresponding 825 * definition of the symbol. Returns a pointer to the symbol, or NULL if 826 * no definition was found. Returns a pointer to the Obj_Entry of the 827 * defining object via the reference parameter DEFOBJ_OUT. 828 */ 829const Elf_Sym * 830find_symdef(unsigned long symnum, const Obj_Entry *refobj, 831 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) 832{ 833 const Elf_Sym *ref; 834 const Elf_Sym *def; 835 const Obj_Entry *defobj; 836 const char *name; 837 unsigned long hash; 838 839 /* 840 * If we have already found this symbol, get the information from 841 * the cache. 842 */ 843 if (symnum >= refobj->nchains) 844 return NULL; /* Bad object */ 845 if (cache != NULL && cache[symnum].sym != NULL) { 846 *defobj_out = cache[symnum].obj; 847 return cache[symnum].sym; 848 } 849 850 ref = refobj->symtab + symnum; 851 name = refobj->strtab + ref->st_name; 852 hash = elf_hash(name); 853 defobj = NULL; 854 855 def = symlook_default(name, hash, refobj, &defobj, in_plt); 856 857 /* 858 * If we found no definition and the reference is weak, treat the 859 * symbol as having the value zero. 860 */ 861 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { 862 def = &sym_zero; 863 defobj = obj_main; 864 } 865 866 if (def != NULL) { 867 *defobj_out = defobj; 868 /* Record the information in the cache to avoid subsequent lookups. */ 869 if (cache != NULL) { 870 cache[symnum].sym = def; 871 cache[symnum].obj = defobj; 872 } 873 } else { 874 if (refobj != &obj_rtld) 875 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); 876 } 877 return def; 878} 879 880/* 881 * Return the search path from the ldconfig hints file, reading it if 882 * necessary. Returns NULL if there are problems with the hints file, 883 * or if the search path there is empty. 884 */ 885static const char * 886gethints(void) 887{ 888 static char *hints; 889 890 if (hints == NULL) { 891 int fd; 892 struct elfhints_hdr hdr; 893 char *p; 894 895 /* Keep from trying again in case the hints file is bad. */ 896 hints = ""; 897 898 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) 899 return NULL; 900 if (read(fd, &hdr, sizeof hdr) != sizeof hdr || 901 hdr.magic != ELFHINTS_MAGIC || 902 hdr.version != 1) { 903 close(fd); 904 return NULL; 905 } 906 p = xmalloc(hdr.dirlistlen + 1); 907 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || 908 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { 909 free(p); 910 close(fd); 911 return NULL; 912 } 913 hints = p; 914 close(fd); 915 } 916 return hints[0] != '\0' ? hints : NULL; 917} 918 919static void 920init_dag(Obj_Entry *root) 921{ 922 DoneList donelist; 923 924 donelist_init(&donelist); 925 init_dag1(root, root, &donelist); 926} 927 928static void 929init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) 930{ 931 const Needed_Entry *needed; 932 933 if (donelist_check(dlp, obj)) 934 return; 935 objlist_push_tail(&obj->dldags, root); 936 objlist_push_tail(&root->dagmembers, obj); 937 for (needed = obj->needed; needed != NULL; needed = needed->next) 938 if (needed->obj != NULL) 939 init_dag1(root, needed->obj, dlp); 940} 941 942/* 943 * Initialize the dynamic linker. The argument is the address at which 944 * the dynamic linker has been mapped into memory. The primary task of 945 * this function is to relocate the dynamic linker. 946 */ 947static void 948init_rtld(caddr_t mapbase) 949{ 950 /* 951 * Conjure up an Obj_Entry structure for the dynamic linker. 952 * 953 * The "path" member is supposed to be dynamically-allocated, but we 954 * aren't yet initialized sufficiently to do that. Below we will 955 * replace the static version with a dynamically-allocated copy. 956 */ 957 obj_rtld.path = PATH_RTLD; 958 obj_rtld.rtld = true; 959 obj_rtld.mapbase = mapbase; 960#ifdef PIC 961 obj_rtld.relocbase = mapbase; 962#endif 963 if (&_DYNAMIC != 0) { 964 obj_rtld.dynamic = rtld_dynamic(&obj_rtld); 965 digest_dynamic(&obj_rtld); 966 assert(obj_rtld.needed == NULL); 967 assert(!obj_rtld.textrel); 968 969 /* 970 * Temporarily put the dynamic linker entry into the object list, so 971 * that symbols can be found. 972 */ 973 obj_list = &obj_rtld; 974 obj_tail = &obj_rtld.next; 975 obj_count = 1; 976 977 relocate_objects(&obj_rtld, true); 978 } 979 980 /* Make the object list empty again. */ 981 obj_list = NULL; 982 obj_tail = &obj_list; 983 obj_count = 0; 984 985 /* Replace the path with a dynamically allocated copy. */ 986 obj_rtld.path = xstrdup(obj_rtld.path); 987 988 r_debug.r_brk = r_debug_state; 989 r_debug.r_state = RT_CONSISTENT; 990} 991 992/* 993 * Add the init functions from a needed object list (and its recursive 994 * needed objects) to "list". This is not used directly; it is a helper 995 * function for initlist_add_objects(). The write lock must be held 996 * when this function is called. 997 */ 998static void 999initlist_add_neededs(Needed_Entry *needed, Objlist *list) 1000{ 1001 /* Recursively process the successor needed objects. */ 1002 if (needed->next != NULL) 1003 initlist_add_neededs(needed->next, list); 1004 1005 /* Process the current needed object. */ 1006 if (needed->obj != NULL) 1007 initlist_add_objects(needed->obj, &needed->obj->next, list); 1008} 1009 1010/* 1011 * Scan all of the DAGs rooted in the range of objects from "obj" to 1012 * "tail" and add their init functions to "list". This recurses over 1013 * the DAGs and ensure the proper init ordering such that each object's 1014 * needed libraries are initialized before the object itself. At the 1015 * same time, this function adds the objects to the global finalization 1016 * list "list_fini" in the opposite order. The write lock must be 1017 * held when this function is called. 1018 */ 1019static void 1020initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) 1021{ 1022 if (obj->init_done) 1023 return; 1024 obj->init_done = true; 1025 1026 /* Recursively process the successor objects. */ 1027 if (&obj->next != tail) 1028 initlist_add_objects(obj->next, tail, list); 1029 1030 /* Recursively process the needed objects. */ 1031 if (obj->needed != NULL) 1032 initlist_add_neededs(obj->needed, list); 1033 1034 /* Add the object to the init list. */ 1035 if (obj->init != NULL) 1036 objlist_push_tail(list, obj); 1037 1038 /* Add the object to the global fini list in the reverse order. */ 1039 if (obj->fini != NULL) 1040 objlist_push_head(&list_fini, obj); 1041} 1042 1043#ifndef FPTR_TARGET 1044#define FPTR_TARGET(f) ((Elf_Addr) (f)) 1045#endif 1046 1047static bool 1048is_exported(const Elf_Sym *def) 1049{ 1050 Elf_Addr value; 1051 const func_ptr_type *p; 1052 1053 value = (Elf_Addr)(obj_rtld.relocbase + def->st_value); 1054 for (p = exports; *p != NULL; p++) 1055 if (FPTR_TARGET(*p) == value) 1056 return true; 1057 return false; 1058} 1059 1060/* 1061 * Given a shared object, traverse its list of needed objects, and load 1062 * each of them. Returns 0 on success. Generates an error message and 1063 * returns -1 on failure. 1064 */ 1065static int 1066load_needed_objects(Obj_Entry *first) 1067{ 1068 Obj_Entry *obj; 1069 1070 for (obj = first; obj != NULL; obj = obj->next) { 1071 Needed_Entry *needed; 1072 1073 for (needed = obj->needed; needed != NULL; needed = needed->next) { 1074 const char *name = obj->strtab + needed->name; 1075 char *path = find_library(name, obj); 1076 1077 needed->obj = NULL; 1078 if (path == NULL && !ld_tracing) 1079 return -1; 1080 1081 if (path) { 1082 needed->obj = load_object(path); 1083 if (needed->obj == NULL && !ld_tracing) 1084 return -1; /* XXX - cleanup */ 1085 } 1086 } 1087 } 1088 1089 return 0; 1090} 1091 1092static int 1093load_preload_objects(void) 1094{ 1095 char *p = ld_preload; 1096 static const char delim[] = " \t:;"; 1097 1098 if (p == NULL) 1099 return NULL; 1100 1101 p += strspn(p, delim); 1102 while (*p != '\0') { 1103 size_t len = strcspn(p, delim); 1104 char *path; 1105 char savech; 1106 1107 savech = p[len]; 1108 p[len] = '\0'; 1109 if ((path = find_library(p, NULL)) == NULL) 1110 return -1; 1111 if (load_object(path) == NULL) 1112 return -1; /* XXX - cleanup */ 1113 p[len] = savech; 1114 p += len; 1115 p += strspn(p, delim); 1116 } 1117 return 0; 1118} 1119 1120/* 1121 * Load a shared object into memory, if it is not already loaded. The 1122 * argument must be a string allocated on the heap. This function assumes 1123 * responsibility for freeing it when necessary. 1124 * 1125 * Returns a pointer to the Obj_Entry for the object. Returns NULL 1126 * on failure. 1127 */ 1128static Obj_Entry * 1129load_object(char *path) 1130{ 1131 Obj_Entry *obj; 1132 int fd = -1; 1133 struct stat sb; 1134 1135 for (obj = obj_list->next; obj != NULL; obj = obj->next) 1136 if (strcmp(obj->path, path) == 0) 1137 break; 1138 1139 /* 1140 * If we didn't find a match by pathname, open the file and check 1141 * again by device and inode. This avoids false mismatches caused 1142 * by multiple links or ".." in pathnames. 1143 * 1144 * To avoid a race, we open the file and use fstat() rather than 1145 * using stat(). 1146 */ 1147 if (obj == NULL) { 1148 if ((fd = open(path, O_RDONLY)) == -1) { 1149 _rtld_error("Cannot open \"%s\"", path); 1150 return NULL; 1151 } 1152 if (fstat(fd, &sb) == -1) { 1153 _rtld_error("Cannot fstat \"%s\"", path); 1154 close(fd); 1155 return NULL; 1156 } 1157 for (obj = obj_list->next; obj != NULL; obj = obj->next) { 1158 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) { 1159 close(fd); 1160 break; 1161 } 1162 } 1163 } 1164 1165 if (obj == NULL) { /* First use of this object, so we must map it in */ 1166 dbg("loading \"%s\"", path); 1167 obj = map_object(fd, path, &sb); 1168 close(fd); 1169 if (obj == NULL) { 1170 free(path); 1171 return NULL; 1172 } 1173 1174 obj->path = path; 1175 digest_dynamic(obj); 1176 1177 *obj_tail = obj; 1178 obj_tail = &obj->next; 1179 obj_count++; 1180 linkmap_add(obj); /* for GDB */ 1181 1182 dbg(" %p .. %p: %s", obj->mapbase, 1183 obj->mapbase + obj->mapsize - 1, obj->path); 1184 if (obj->textrel) 1185 dbg(" WARNING: %s has impure text", obj->path); 1186 } else 1187 free(path); 1188 1189 obj->refcount++; 1190 return obj; 1191} 1192 1193/* 1194 * Check for locking violations and die if one is found. 1195 */ 1196static void 1197lock_check(void) 1198{ 1199 int rcount, wcount; 1200 1201 rcount = lockinfo.rcount; 1202 wcount = lockinfo.wcount; 1203 assert(rcount >= 0); 1204 assert(wcount >= 0); 1205 if (wcount > 1 || (wcount != 0 && rcount != 0)) { 1206 _rtld_error("Application locking error: %d readers and %d writers" 1207 " in dynamic linker. See DLLOCKINIT(3) in manual pages.", 1208 rcount, wcount); 1209 die(); 1210 } 1211} 1212 1213static Obj_Entry * 1214obj_from_addr(const void *addr) 1215{ 1216 unsigned long endhash; 1217 Obj_Entry *obj; 1218 1219 endhash = elf_hash(END_SYM); 1220 for (obj = obj_list; obj != NULL; obj = obj->next) { 1221 const Elf_Sym *endsym; 1222 1223 if (addr < (void *) obj->mapbase) 1224 continue; 1225 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL) 1226 continue; /* No "end" symbol?! */ 1227 if (addr < (void *) (obj->relocbase + endsym->st_value)) 1228 return obj; 1229 } 1230 return NULL; 1231} 1232 1233/* 1234 * Call the finalization functions for each of the objects in "list" 1235 * which are unreferenced. All of the objects are expected to have 1236 * non-NULL fini functions. 1237 */ 1238static void 1239objlist_call_fini(Objlist *list) 1240{ 1241 Objlist_Entry *elm; 1242 char *saved_msg; 1243 1244 /* 1245 * Preserve the current error message since a fini function might 1246 * call into the dynamic linker and overwrite it. 1247 */ 1248 saved_msg = errmsg_save(); 1249 STAILQ_FOREACH(elm, list, link) { 1250 if (elm->obj->refcount == 0) { 1251 dbg("calling fini function for %s", elm->obj->path); 1252 (*elm->obj->fini)(); 1253 } 1254 } 1255 errmsg_restore(saved_msg); 1256} 1257 1258/* 1259 * Call the initialization functions for each of the objects in 1260 * "list". All of the objects are expected to have non-NULL init 1261 * functions. 1262 */ 1263static void 1264objlist_call_init(Objlist *list) 1265{ 1266 Objlist_Entry *elm; 1267 char *saved_msg; 1268 1269 /* 1270 * Preserve the current error message since an init function might 1271 * call into the dynamic linker and overwrite it. 1272 */ 1273 saved_msg = errmsg_save(); 1274 STAILQ_FOREACH(elm, list, link) { 1275 dbg("calling init function for %s", elm->obj->path); 1276 (*elm->obj->init)(); 1277 } 1278 errmsg_restore(saved_msg); 1279} 1280 1281static void 1282objlist_clear(Objlist *list) 1283{ 1284 Objlist_Entry *elm; 1285 1286 while (!STAILQ_EMPTY(list)) { 1287 elm = STAILQ_FIRST(list); 1288 STAILQ_REMOVE_HEAD(list, link); 1289 free(elm); 1290 } 1291} 1292 1293static Objlist_Entry * 1294objlist_find(Objlist *list, const Obj_Entry *obj) 1295{ 1296 Objlist_Entry *elm; 1297 1298 STAILQ_FOREACH(elm, list, link) 1299 if (elm->obj == obj) 1300 return elm; 1301 return NULL; 1302} 1303 1304static void 1305objlist_init(Objlist *list) 1306{ 1307 STAILQ_INIT(list); 1308} 1309 1310static void 1311objlist_push_head(Objlist *list, Obj_Entry *obj) 1312{ 1313 Objlist_Entry *elm; 1314 1315 elm = NEW(Objlist_Entry); 1316 elm->obj = obj; 1317 STAILQ_INSERT_HEAD(list, elm, link); 1318} 1319 1320static void 1321objlist_push_tail(Objlist *list, Obj_Entry *obj) 1322{ 1323 Objlist_Entry *elm; 1324 1325 elm = NEW(Objlist_Entry); 1326 elm->obj = obj; 1327 STAILQ_INSERT_TAIL(list, elm, link); 1328} 1329 1330static void 1331objlist_remove(Objlist *list, Obj_Entry *obj) 1332{ 1333 Objlist_Entry *elm; 1334 1335 if ((elm = objlist_find(list, obj)) != NULL) { 1336 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); 1337 free(elm); 1338 } 1339} 1340 1341/* 1342 * Remove all of the unreferenced objects from "list". 1343 */ 1344static void 1345objlist_remove_unref(Objlist *list) 1346{ 1347 Objlist newlist; 1348 Objlist_Entry *elm; 1349 1350 STAILQ_INIT(&newlist); 1351 while (!STAILQ_EMPTY(list)) { 1352 elm = STAILQ_FIRST(list); 1353 STAILQ_REMOVE_HEAD(list, link); 1354 if (elm->obj->refcount == 0) 1355 free(elm); 1356 else 1357 STAILQ_INSERT_TAIL(&newlist, elm, link); 1358 } 1359 *list = newlist; 1360} 1361 1362/* 1363 * Relocate newly-loaded shared objects. The argument is a pointer to 1364 * the Obj_Entry for the first such object. All objects from the first 1365 * to the end of the list of objects are relocated. Returns 0 on success, 1366 * or -1 on failure. 1367 */ 1368static int 1369relocate_objects(Obj_Entry *first, bool bind_now) 1370{ 1371 Obj_Entry *obj; 1372 1373 for (obj = first; obj != NULL; obj = obj->next) { 1374 if (obj != &obj_rtld) 1375 dbg("relocating \"%s\"", obj->path); 1376 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || 1377 obj->symtab == NULL || obj->strtab == NULL) { 1378 _rtld_error("%s: Shared object has no run-time symbol table", 1379 obj->path); 1380 return -1; 1381 } 1382 1383 if (obj->textrel) { 1384 /* There are relocations to the write-protected text segment. */ 1385 if (mprotect(obj->mapbase, obj->textsize, 1386 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { 1387 _rtld_error("%s: Cannot write-enable text segment: %s", 1388 obj->path, strerror(errno)); 1389 return -1; 1390 } 1391 } 1392 1393 /* Process the non-PLT relocations. */ 1394 if (reloc_non_plt(obj, &obj_rtld)) 1395 return -1; 1396 1397 if (obj->textrel) { /* Re-protected the text segment. */ 1398 if (mprotect(obj->mapbase, obj->textsize, 1399 PROT_READ|PROT_EXEC) == -1) { 1400 _rtld_error("%s: Cannot write-protect text segment: %s", 1401 obj->path, strerror(errno)); 1402 return -1; 1403 } 1404 } 1405 1406 /* Process the PLT relocations. */ 1407 if (reloc_plt(obj) == -1) 1408 return -1; 1409 /* Relocate the jump slots if we are doing immediate binding. */ 1410 if (bind_now) 1411 if (reloc_jmpslots(obj) == -1) 1412 return -1; 1413 1414 1415 /* 1416 * Set up the magic number and version in the Obj_Entry. These 1417 * were checked in the crt1.o from the original ElfKit, so we 1418 * set them for backward compatibility. 1419 */ 1420 obj->magic = RTLD_MAGIC; 1421 obj->version = RTLD_VERSION; 1422 1423 /* Set the special PLT or GOT entries. */ 1424 init_pltgot(obj); 1425 } 1426 1427 return 0; 1428} 1429 1430/* 1431 * Cleanup procedure. It will be called (by the atexit mechanism) just 1432 * before the process exits. 1433 */ 1434static void 1435rtld_exit(void) 1436{ 1437 Obj_Entry *obj; 1438 1439 dbg("rtld_exit()"); 1440 wlock_acquire(); 1441 /* Clear all the reference counts so the fini functions will be called. */ 1442 for (obj = obj_list; obj != NULL; obj = obj->next) 1443 obj->refcount = 0; 1444 wlock_release(); 1445 objlist_call_fini(&list_fini); 1446 /* No need to remove the items from the list, since we are exiting. */ 1447} 1448 1449static char * 1450search_library_path(const char *name, const char *path) 1451{ 1452 size_t namelen = strlen(name); 1453 const char *p = path; 1454 1455 if (p == NULL) 1456 return NULL; 1457 1458 p += strspn(p, ":;"); 1459 while (*p != '\0') { 1460 size_t len = strcspn(p, ":;"); 1461 1462 if (*p == '/' || trust) { 1463 char *pathname; 1464 const char *dir = p; 1465 size_t dirlen = len; 1466 1467 pathname = xmalloc(dirlen + 1 + namelen + 1); 1468 strncpy(pathname, dir, dirlen); 1469 pathname[dirlen] = '/'; 1470 strcpy(pathname + dirlen + 1, name); 1471 1472 dbg(" Trying \"%s\"", pathname); 1473 if (access(pathname, F_OK) == 0) /* We found it */ 1474 return pathname; 1475 1476 free(pathname); 1477 } 1478 p += len; 1479 p += strspn(p, ":;"); 1480 } 1481 1482 return NULL; 1483} 1484 1485int 1486dlclose(void *handle) 1487{ 1488 Obj_Entry *root; 1489 1490 wlock_acquire(); 1491 root = dlcheck(handle); 1492 if (root == NULL) { 1493 wlock_release(); 1494 return -1; 1495 } 1496 1497 /* Unreference the object and its dependencies. */ 1498 root->dl_refcount--; 1499 unref_dag(root); 1500 1501 if (root->refcount == 0) { 1502 /* 1503 * The object is no longer referenced, so we must unload it. 1504 * First, call the fini functions with no locks held. 1505 */ 1506 wlock_release(); 1507 objlist_call_fini(&list_fini); 1508 wlock_acquire(); 1509 objlist_remove_unref(&list_fini); 1510 1511 /* Finish cleaning up the newly-unreferenced objects. */ 1512 GDB_STATE(RT_DELETE,&root->linkmap); 1513 unload_object(root); 1514 GDB_STATE(RT_CONSISTENT,NULL); 1515 } 1516 wlock_release(); 1517 return 0; 1518} 1519 1520const char * 1521dlerror(void) 1522{ 1523 char *msg = error_message; 1524 error_message = NULL; 1525 return msg; 1526} 1527 1528/* 1529 * This function is deprecated and has no effect. 1530 */ 1531void 1532dllockinit(void *context, 1533 void *(*lock_create)(void *context), 1534 void (*rlock_acquire)(void *lock), 1535 void (*wlock_acquire)(void *lock), 1536 void (*lock_release)(void *lock), 1537 void (*lock_destroy)(void *lock), 1538 void (*context_destroy)(void *context)) 1539{ 1540 static void *cur_context; 1541 static void (*cur_context_destroy)(void *); 1542 1543 /* Just destroy the context from the previous call, if necessary. */ 1544 if (cur_context_destroy != NULL) 1545 cur_context_destroy(cur_context); 1546 cur_context = context; 1547 cur_context_destroy = context_destroy; 1548} 1549 1550void * 1551dlopen(const char *name, int mode) 1552{ 1553 Obj_Entry **old_obj_tail; 1554 Obj_Entry *obj; 1555 Objlist initlist; 1556 1557 objlist_init(&initlist); 1558 1559 wlock_acquire(); 1560 GDB_STATE(RT_ADD,NULL); 1561 1562 old_obj_tail = obj_tail; 1563 obj = NULL; 1564 if (name == NULL) { 1565 obj = obj_main; 1566 obj->refcount++; 1567 } else { 1568 char *path = find_library(name, obj_main); 1569 if (path != NULL) 1570 obj = load_object(path); 1571 } 1572 1573 if (obj) { 1574 obj->dl_refcount++; 1575 if (mode & RTLD_GLOBAL && objlist_find(&list_global, obj) == NULL) 1576 objlist_push_tail(&list_global, obj); 1577 mode &= RTLD_MODEMASK; 1578 if (*old_obj_tail != NULL) { /* We loaded something new. */ 1579 assert(*old_obj_tail == obj); 1580 1581 if (load_needed_objects(obj) == -1 || 1582 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) { 1583 obj->dl_refcount--; 1584 unref_dag(obj); 1585 if (obj->refcount == 0) 1586 unload_object(obj); 1587 obj = NULL; 1588 } else { 1589 /* Make list of init functions to call. */ 1590 initlist_add_objects(obj, &obj->next, &initlist); 1591 } 1592 } 1593 } 1594 1595 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); 1596 1597 /* Call the init functions with no locks held. */ 1598 wlock_release(); 1599 objlist_call_init(&initlist); 1600 wlock_acquire(); 1601 objlist_clear(&initlist); 1602 wlock_release(); 1603 return obj; 1604} 1605 1606void * 1607dlsym(void *handle, const char *name) 1608{ 1609 const Obj_Entry *obj; 1610 unsigned long hash; 1611 const Elf_Sym *def; 1612 const Obj_Entry *defobj; 1613 1614 hash = elf_hash(name); 1615 def = NULL; 1616 defobj = NULL; 1617 1618 rlock_acquire(); 1619 if (handle == NULL || handle == RTLD_NEXT || handle == RTLD_DEFAULT) { 1620 void *retaddr; 1621 1622 retaddr = __builtin_return_address(0); /* __GNUC__ only */ 1623 if ((obj = obj_from_addr(retaddr)) == NULL) { 1624 _rtld_error("Cannot determine caller's shared object"); 1625 rlock_release(); 1626 return NULL; 1627 } 1628 if (handle == NULL) { /* Just the caller's shared object. */ 1629 def = symlook_obj(name, hash, obj, true); 1630 defobj = obj; 1631 } else if (handle == RTLD_NEXT) { /* Objects after caller's */ 1632 while ((obj = obj->next) != NULL) { 1633 if ((def = symlook_obj(name, hash, obj, true)) != NULL) { 1634 defobj = obj; 1635 break; 1636 } 1637 } 1638 } else { 1639 assert(handle == RTLD_DEFAULT); 1640 def = symlook_default(name, hash, obj, &defobj, true); 1641 } 1642 } else { 1643 if ((obj = dlcheck(handle)) == NULL) { 1644 rlock_release(); 1645 return NULL; 1646 } 1647 1648 if (obj->mainprog) { 1649 DoneList donelist; 1650 1651 /* Search main program and all libraries loaded by it. */ 1652 donelist_init(&donelist); 1653 def = symlook_list(name, hash, &list_main, &defobj, true, 1654 &donelist); 1655 } else { 1656 /* 1657 * XXX - This isn't correct. The search should include the whole 1658 * DAG rooted at the given object. 1659 */ 1660 def = symlook_obj(name, hash, obj, true); 1661 defobj = obj; 1662 } 1663 } 1664 1665 if (def != NULL) { 1666 rlock_release(); 1667 1668 /* 1669 * The value required by the caller is derived from the value 1670 * of the symbol. For the ia64 architecture, we need to 1671 * construct a function descriptor which the caller can use to 1672 * call the function with the right 'gp' value. For other 1673 * architectures and for non-functions, the value is simply 1674 * the relocated value of the symbol. 1675 */ 1676 if (ELF_ST_TYPE(def->st_info) == STT_FUNC) 1677 return make_function_pointer(def, defobj); 1678 else 1679 return defobj->relocbase + def->st_value; 1680 } 1681 1682 _rtld_error("Undefined symbol \"%s\"", name); 1683 rlock_release(); 1684 return NULL; 1685} 1686 1687int 1688dladdr(const void *addr, Dl_info *info) 1689{ 1690 const Obj_Entry *obj; 1691 const Elf_Sym *def; 1692 void *symbol_addr; 1693 unsigned long symoffset; 1694 1695 rlock_acquire(); 1696 obj = obj_from_addr(addr); 1697 if (obj == NULL) { 1698 _rtld_error("No shared object contains address"); 1699 rlock_release(); 1700 return 0; 1701 } 1702 info->dli_fname = obj->path; 1703 info->dli_fbase = obj->mapbase; 1704 info->dli_saddr = (void *)0; 1705 info->dli_sname = NULL; 1706 1707 /* 1708 * Walk the symbol list looking for the symbol whose address is 1709 * closest to the address sent in. 1710 */ 1711 for (symoffset = 0; symoffset < obj->nchains; symoffset++) { 1712 def = obj->symtab + symoffset; 1713 1714 /* 1715 * For skip the symbol if st_shndx is either SHN_UNDEF or 1716 * SHN_COMMON. 1717 */ 1718 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) 1719 continue; 1720 1721 /* 1722 * If the symbol is greater than the specified address, or if it 1723 * is further away from addr than the current nearest symbol, 1724 * then reject it. 1725 */ 1726 symbol_addr = obj->relocbase + def->st_value; 1727 if (symbol_addr > addr || symbol_addr < info->dli_saddr) 1728 continue; 1729 1730 /* Update our idea of the nearest symbol. */ 1731 info->dli_sname = obj->strtab + def->st_name; 1732 info->dli_saddr = symbol_addr; 1733 1734 /* Exact match? */ 1735 if (info->dli_saddr == addr) 1736 break; 1737 } 1738 rlock_release(); 1739 return 1; 1740} 1741 1742static void 1743linkmap_add(Obj_Entry *obj) 1744{ 1745 struct link_map *l = &obj->linkmap; 1746 struct link_map *prev; 1747 1748 obj->linkmap.l_name = obj->path; 1749 obj->linkmap.l_addr = obj->mapbase; 1750 obj->linkmap.l_ld = obj->dynamic; 1751#ifdef __mips__ 1752 /* GDB needs load offset on MIPS to use the symbols */ 1753 obj->linkmap.l_offs = obj->relocbase; 1754#endif 1755 1756 if (r_debug.r_map == NULL) { 1757 r_debug.r_map = l; 1758 return; 1759 } 1760 1761 /* 1762 * Scan to the end of the list, but not past the entry for the 1763 * dynamic linker, which we want to keep at the very end. 1764 */ 1765 for (prev = r_debug.r_map; 1766 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; 1767 prev = prev->l_next) 1768 ; 1769 1770 /* Link in the new entry. */ 1771 l->l_prev = prev; 1772 l->l_next = prev->l_next; 1773 if (l->l_next != NULL) 1774 l->l_next->l_prev = l; 1775 prev->l_next = l; 1776} 1777 1778static void 1779linkmap_delete(Obj_Entry *obj) 1780{ 1781 struct link_map *l = &obj->linkmap; 1782 1783 if (l->l_prev == NULL) { 1784 if ((r_debug.r_map = l->l_next) != NULL) 1785 l->l_next->l_prev = NULL; 1786 return; 1787 } 1788 1789 if ((l->l_prev->l_next = l->l_next) != NULL) 1790 l->l_next->l_prev = l->l_prev; 1791} 1792 1793/* 1794 * Function for the debugger to set a breakpoint on to gain control. 1795 * 1796 * The two parameters allow the debugger to easily find and determine 1797 * what the runtime loader is doing and to whom it is doing it. 1798 * 1799 * When the loadhook trap is hit (r_debug_state, set at program 1800 * initialization), the arguments can be found on the stack: 1801 * 1802 * +8 struct link_map *m 1803 * +4 struct r_debug *rd 1804 * +0 RetAddr 1805 */ 1806void 1807r_debug_state(struct r_debug* rd, struct link_map *m) 1808{ 1809} 1810 1811/* 1812 * Set a pointer variable in the main program to the given value. This 1813 * is used to set key variables such as "environ" before any of the 1814 * init functions are called. 1815 */ 1816static void 1817set_program_var(const char *name, const void *value) 1818{ 1819 const Obj_Entry *obj; 1820 unsigned long hash; 1821 1822 hash = elf_hash(name); 1823 for (obj = obj_main; obj != NULL; obj = obj->next) { 1824 const Elf_Sym *def; 1825 1826 if ((def = symlook_obj(name, hash, obj, false)) != NULL) { 1827 const void **addr; 1828 1829 addr = (const void **)(obj->relocbase + def->st_value); 1830 dbg("\"%s\": *%p <-- %p", name, addr, value); 1831 *addr = value; 1832 break; 1833 } 1834 } 1835} 1836 1837/* 1838 * Given a symbol name in a referencing object, find the corresponding 1839 * definition of the symbol. Returns a pointer to the symbol, or NULL if 1840 * no definition was found. Returns a pointer to the Obj_Entry of the 1841 * defining object via the reference parameter DEFOBJ_OUT. 1842 */ 1843static const Elf_Sym * 1844symlook_default(const char *name, unsigned long hash, 1845 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) 1846{ 1847 DoneList donelist; 1848 const Elf_Sym *def; 1849 const Elf_Sym *symp; 1850 const Obj_Entry *obj; 1851 const Obj_Entry *defobj; 1852 const Objlist_Entry *elm; 1853 def = NULL; 1854 defobj = NULL; 1855 donelist_init(&donelist); 1856 1857 /* Look first in the referencing object if linked symbolically. */ 1858 if (refobj->symbolic && !donelist_check(&donelist, refobj)) { 1859 symp = symlook_obj(name, hash, refobj, in_plt); 1860 if (symp != NULL) { 1861 def = symp; 1862 defobj = refobj; 1863 } 1864 } 1865 1866 /* Search all objects loaded at program start up. */ 1867 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 1868 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); 1869 if (symp != NULL && 1870 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 1871 def = symp; 1872 defobj = obj; 1873 } 1874 } 1875 1876 /* Search all dlopened DAGs containing the referencing object. */ 1877 STAILQ_FOREACH(elm, &refobj->dldags, link) { 1878 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) 1879 break; 1880 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, 1881 &donelist); 1882 if (symp != NULL && 1883 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 1884 def = symp; 1885 defobj = obj; 1886 } 1887 } 1888 1889 /* Search all RTLD_GLOBAL objects. */ 1890 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 1891 symp = symlook_list(name, hash, &list_global, &obj, in_plt, &donelist); 1892 if (symp != NULL && 1893 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { 1894 def = symp; 1895 defobj = obj; 1896 } 1897 } 1898 1899 /* 1900 * Search the dynamic linker itself, and possibly resolve the 1901 * symbol from there. This is how the application links to 1902 * dynamic linker services such as dlopen. Only the values listed 1903 * in the "exports" array can be resolved from the dynamic linker. 1904 */ 1905 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { 1906 symp = symlook_obj(name, hash, &obj_rtld, in_plt); 1907 if (symp != NULL && is_exported(symp)) { 1908 def = symp; 1909 defobj = &obj_rtld; 1910 } 1911 } 1912 1913 if (def != NULL) 1914 *defobj_out = defobj; 1915 return def; 1916} 1917 1918static const Elf_Sym * 1919symlook_list(const char *name, unsigned long hash, Objlist *objlist, 1920 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) 1921{ 1922 const Elf_Sym *symp; 1923 const Elf_Sym *def; 1924 const Obj_Entry *defobj; 1925 const Objlist_Entry *elm; 1926 1927 def = NULL; 1928 defobj = NULL; 1929 STAILQ_FOREACH(elm, objlist, link) { 1930 if (donelist_check(dlp, elm->obj)) 1931 continue; 1932 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { 1933 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { 1934 def = symp; 1935 defobj = elm->obj; 1936 if (ELF_ST_BIND(def->st_info) != STB_WEAK) 1937 break; 1938 } 1939 } 1940 } 1941 if (def != NULL) 1942 *defobj_out = defobj; 1943 return def; 1944} 1945 1946/* 1947 * Search the symbol table of a single shared object for a symbol of 1948 * the given name. Returns a pointer to the symbol, or NULL if no 1949 * definition was found. 1950 * 1951 * The symbol's hash value is passed in for efficiency reasons; that 1952 * eliminates many recomputations of the hash value. 1953 */ 1954const Elf_Sym * 1955symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, 1956 bool in_plt) 1957{ 1958 if (obj->buckets != NULL) { 1959 unsigned long symnum = obj->buckets[hash % obj->nbuckets]; 1960 1961 while (symnum != STN_UNDEF) { 1962 const Elf_Sym *symp; 1963 const char *strp; 1964 1965 if (symnum >= obj->nchains) 1966 return NULL; /* Bad object */ 1967 symp = obj->symtab + symnum; 1968 strp = obj->strtab + symp->st_name; 1969 1970 if (name[0] == strp[0] && strcmp(name, strp) == 0) 1971 return symp->st_shndx != SHN_UNDEF || 1972 (!in_plt && symp->st_value != 0 && 1973 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; 1974 1975 symnum = obj->chains[symnum]; 1976 } 1977 } 1978 return NULL; 1979} 1980 1981static void 1982trace_loaded_objects(Obj_Entry *obj) 1983{ 1984 char *fmt1, *fmt2, *fmt, *main_local; 1985 int c; 1986 1987 if ((main_local = getenv("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) 1988 main_local = ""; 1989 1990 if ((fmt1 = getenv("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) 1991 fmt1 = "\t%o => %p (%x)\n"; 1992 1993 if ((fmt2 = getenv("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) 1994 fmt2 = "\t%o (%x)\n"; 1995 1996 for (; obj; obj = obj->next) { 1997 Needed_Entry *needed; 1998 char *name, *path; 1999 bool is_lib; 2000 2001 for (needed = obj->needed; needed; needed = needed->next) { 2002 if (needed->obj != NULL) { 2003 if (needed->obj->traced) 2004 continue; 2005 needed->obj->traced = true; 2006 path = needed->obj->path; 2007 } else 2008 path = "not found"; 2009 2010 name = (char *)obj->strtab + needed->name; 2011 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ 2012 2013 fmt = is_lib ? fmt1 : fmt2; 2014 while ((c = *fmt++) != '\0') { 2015 switch (c) { 2016 default: 2017 putchar(c); 2018 continue; 2019 case '\\': 2020 switch (c = *fmt) { 2021 case '\0': 2022 continue; 2023 case 'n': 2024 putchar('\n'); 2025 break; 2026 case 't': 2027 putchar('\t'); 2028 break; 2029 } 2030 break; 2031 case '%': 2032 switch (c = *fmt) { 2033 case '\0': 2034 continue; 2035 case '%': 2036 default: 2037 putchar(c); 2038 break; 2039 case 'A': 2040 printf("%s", main_local); 2041 break; 2042 case 'a': 2043 printf("%s", obj_main->path); 2044 break; 2045 case 'o': 2046 printf("%s", name); 2047 break; 2048#if 0 2049 case 'm': 2050 printf("%d", sodp->sod_major); 2051 break; 2052 case 'n': 2053 printf("%d", sodp->sod_minor); 2054 break; 2055#endif 2056 case 'p': 2057 printf("%s", path); 2058 break; 2059 case 'x': 2060 printf("%p", needed->obj ? needed->obj->mapbase : 0); 2061 break; 2062 } 2063 break; 2064 } 2065 ++fmt; 2066 } 2067 } 2068 } 2069} 2070 2071/* 2072 * Unload a dlopened object and its dependencies from memory and from 2073 * our data structures. It is assumed that the DAG rooted in the 2074 * object has already been unreferenced, and that the object has a 2075 * reference count of 0. 2076 */ 2077static void 2078unload_object(Obj_Entry *root) 2079{ 2080 Obj_Entry *obj; 2081 Obj_Entry **linkp; 2082 Objlist_Entry *elm; 2083 2084 assert(root->refcount == 0); 2085 2086 /* Remove the DAG from all objects' DAG lists. */ 2087 STAILQ_FOREACH(elm, &root->dagmembers , link) 2088 objlist_remove(&elm->obj->dldags, root); 2089 2090 /* Remove the DAG from the RTLD_GLOBAL list. */ 2091 objlist_remove(&list_global, root); 2092 2093 /* Unmap all objects that are no longer referenced. */ 2094 linkp = &obj_list->next; 2095 while ((obj = *linkp) != NULL) { 2096 if (obj->refcount == 0) { 2097 dbg("unloading \"%s\"", obj->path); 2098 munmap(obj->mapbase, obj->mapsize); 2099 linkmap_delete(obj); 2100 *linkp = obj->next; 2101 obj_count--; 2102 obj_free(obj); 2103 } else 2104 linkp = &obj->next; 2105 } 2106 obj_tail = linkp; 2107} 2108 2109static void 2110unref_dag(Obj_Entry *root) 2111{ 2112 const Needed_Entry *needed; 2113 2114 if (root->refcount == 0) 2115 return; 2116 root->refcount--; 2117 if (root->refcount == 0) 2118 for (needed = root->needed; needed != NULL; needed = needed->next) 2119 if (needed->obj != NULL) 2120 unref_dag(needed->obj); 2121} 2122 2123/* 2124 * Non-mallocing printf, for use by malloc itself. 2125 * XXX - This doesn't belong in this module. 2126 */ 2127void 2128xprintf(const char *fmt, ...) 2129{ 2130 char buf[256]; 2131 va_list ap; 2132 2133 va_start(ap, fmt); 2134 vsprintf(buf, fmt, ap); 2135 (void)write(STDOUT_FILENO, buf, strlen(buf)); 2136 va_end(ap); 2137} 2138