2 * Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra.
3 * Copyright 2003 Alexander Kabaev <kan@FreeBSD.ORG>.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
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.
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.
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 1.16 2005/02/24 16:05:22 joerg Exp $
31 * Dynamic linker for ELF.
33 * John Polstra <jdp@polstra.com>.
37 #error "GCC is needed to compile this file"
40 #include <sys/param.h>
43 #include <sys/resident.h>
58 #define PATH_RTLD "/usr/libexec/ld-elf.so.1"
59 #define LD_ARY_CACHE 16
62 typedef void (*func_ptr_type)();
63 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg);
66 * This structure provides a reentrant way to keep a list of objects and
67 * check which ones have already been processed in some way.
69 typedef struct Struct_DoneList {
70 const Obj_Entry **objs; /* Array of object pointers */
71 unsigned int num_alloc; /* Allocated size of the array */
72 unsigned int num_used; /* Number of array slots used */
76 * Function declarations.
78 static void die(void);
79 static void digest_dynamic(Obj_Entry *);
80 static const char *_getenv_ld(const char *id);
81 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
82 static Obj_Entry *dlcheck(void *);
83 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *);
84 static bool donelist_check(DoneList *, const Obj_Entry *);
85 static void errmsg_restore(char *);
86 static char *errmsg_save(void);
87 static void *fill_search_info(const char *, size_t, void *);
88 static char *find_library(const char *, const Obj_Entry *);
89 static Obj_Entry *find_object(const char *);
90 static Obj_Entry *find_object2(const char *, int *, struct stat *);
91 static const char *gethints(void);
92 static void init_dag(Obj_Entry *);
93 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *);
94 static void init_rtld(caddr_t);
95 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list);
96 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail,
98 static bool is_exported(const Elf_Sym *);
99 static void linkmap_add(Obj_Entry *);
100 static void linkmap_delete(Obj_Entry *);
101 static int load_needed_objects(Obj_Entry *);
102 static int load_preload_objects(void);
103 static Obj_Entry *load_object(char *);
104 static void lock_check(void);
105 static Obj_Entry *obj_from_addr(const void *);
106 static void objlist_call_fini(Objlist *);
107 static void objlist_call_init(Objlist *);
108 static void objlist_clear(Objlist *);
109 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *);
110 static void objlist_init(Objlist *);
111 static void objlist_push_head(Objlist *, Obj_Entry *);
112 static void objlist_push_tail(Objlist *, Obj_Entry *);
113 static void objlist_remove(Objlist *, Obj_Entry *);
114 static void objlist_remove_unref(Objlist *);
115 static void *path_enumerate(const char *, path_enum_proc, void *);
116 static int relocate_objects(Obj_Entry *, bool);
117 static int rtld_dirname(const char *, char *);
118 static void rtld_exit(void);
119 static char *search_library_path(const char *, const char *);
120 static const void **get_program_var_addr(const char *name);
121 static void set_program_var(const char *, const void *);
122 static const Elf_Sym *symlook_default(const char *, unsigned long hash,
123 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt);
124 static const Elf_Sym *symlook_list(const char *, unsigned long,
125 Objlist *, const Obj_Entry **, bool in_plt, DoneList *);
126 static void trace_loaded_objects(Obj_Entry *obj);
127 static void unlink_object(Obj_Entry *);
128 static void unload_object(Obj_Entry *);
129 static void unref_dag(Obj_Entry *);
131 void r_debug_state(struct r_debug*, struct link_map*);
136 static char *error_message; /* Message for dlerror(), or NULL */
137 struct r_debug r_debug; /* for GDB; */
138 static bool trust; /* False for setuid and setgid programs */
139 static const char *ld_bind_now; /* Environment variable for immediate binding */
140 static const char *ld_debug; /* Environment variable for debugging */
141 static const char *ld_library_path; /* Environment variable for search path */
142 static char *ld_preload; /* Environment variable for libraries to
144 static const char *ld_tracing; /* Called from ldd(1) to print libs */
145 static Obj_Entry *obj_list; /* Head of linked list of shared objects */
146 static Obj_Entry **obj_tail; /* Link field of last object in list */
147 static Obj_Entry **preload_tail;
148 static Obj_Entry *obj_main; /* The main program shared object */
149 static Obj_Entry obj_rtld; /* The dynamic linker shared object */
150 static unsigned int obj_count; /* Number of objects in obj_list */
151 static int ld_resident; /* Non-zero if resident */
152 static const char *ld_ary[LD_ARY_CACHE];
155 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */
156 STAILQ_HEAD_INITIALIZER(list_global);
157 static Objlist list_main = /* Objects loaded at program startup */
158 STAILQ_HEAD_INITIALIZER(list_main);
159 static Objlist list_fini = /* Objects needing fini() calls */
160 STAILQ_HEAD_INITIALIZER(list_fini);
162 static LockInfo lockinfo;
164 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */
166 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m);
168 extern Elf_Dyn _DYNAMIC;
169 #pragma weak _DYNAMIC
172 * These are the functions the dynamic linker exports to application
173 * programs. They are the only symbols the dynamic linker is willing
174 * to export from itself.
176 static func_ptr_type exports[] = {
177 (func_ptr_type) &_rtld_error,
178 (func_ptr_type) &dlclose,
179 (func_ptr_type) &dlerror,
180 (func_ptr_type) &dlopen,
181 (func_ptr_type) &dlsym,
182 (func_ptr_type) &dladdr,
183 (func_ptr_type) &dllockinit,
184 (func_ptr_type) &dlinfo,
189 * Global declarations normally provided by crt1. The dynamic linker is
190 * not built with crt1, so we have to provide them ourselves.
196 * Fill in a DoneList with an allocation large enough to hold all of
197 * the currently-loaded objects. Keep this as a macro since it calls
198 * alloca and we want that to occur within the scope of the caller.
200 #define donelist_init(dlp) \
201 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \
202 assert((dlp)->objs != NULL), \
203 (dlp)->num_alloc = obj_count, \
209 lockinfo.rlock_acquire(lockinfo.thelock);
210 atomic_incr_int(&lockinfo.rcount);
217 lockinfo.wlock_acquire(lockinfo.thelock);
218 atomic_incr_int(&lockinfo.wcount);
225 atomic_decr_int(&lockinfo.rcount);
226 lockinfo.rlock_release(lockinfo.thelock);
232 atomic_decr_int(&lockinfo.wcount);
233 lockinfo.wlock_release(lockinfo.thelock);
237 * Main entry point for dynamic linking. The first argument is the
238 * stack pointer. The stack is expected to be laid out as described
239 * in the SVR4 ABI specification, Intel 386 Processor Supplement.
240 * Specifically, the stack pointer points to a word containing
241 * ARGC. Following that in the stack is a null-terminated sequence
242 * of pointers to argument strings. Then comes a null-terminated
243 * sequence of pointers to environment strings. Finally, there is a
244 * sequence of "auxiliary vector" entries.
246 * The second argument points to a place to store the dynamic linker's
247 * exit procedure pointer and the third to a place to store the main
250 * The return value is the main program's entry point.
253 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
255 Elf_Auxinfo *aux_info[AT_COUNT];
266 ld_index = 0; /* don't use old env cache in case we are resident */
269 * On entry, the dynamic linker itself has not been relocated yet.
270 * Be very careful not to reference any global data until after
271 * init_rtld has returned. It is OK to reference file-scope statics
272 * and string constants, and to call static and global functions.
275 /* Find the auxiliary vector on the stack. */
278 sp += argc + 1; /* Skip over arguments and NULL terminator */
282 * If we aren't already resident we have to dig out some more info.
283 * Note that auxinfo does not exist when we are resident.
285 if (ld_resident == 0) {
286 while (*sp++ != 0) /* Skip over environment, and NULL terminator */
288 aux = (Elf_Auxinfo *) sp;
290 /* Digest the auxiliary vector. */
291 for (i = 0; i < AT_COUNT; i++)
293 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
294 if (auxp->a_type < AT_COUNT)
295 aux_info[auxp->a_type] = auxp;
298 /* Initialize and relocate ourselves. */
299 assert(aux_info[AT_BASE] != NULL);
300 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
303 __progname = obj_rtld.path;
304 argv0 = argv[0] != NULL ? argv[0] : "(null)";
307 trust = (geteuid() == getuid()) && (getegid() == getgid());
309 ld_bind_now = _getenv_ld("LD_BIND_NOW");
311 ld_debug = _getenv_ld("LD_DEBUG");
312 ld_library_path = _getenv_ld("LD_LIBRARY_PATH");
313 ld_preload = (char *)_getenv_ld("LD_PRELOAD");
315 ld_tracing = _getenv_ld("LD_TRACE_LOADED_OBJECTS");
317 if (ld_debug != NULL && *ld_debug != '\0')
319 dbg("%s is initialized, base address = %p", __progname,
320 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
321 dbg("RTLD dynamic = %p", obj_rtld.dynamic);
322 dbg("RTLD pltgot = %p", obj_rtld.pltgot);
325 * If we are resident we can skip work that we have already done.
326 * Note that the stack is reset and there is no Elf_Auxinfo
327 * when running from a resident image, and the static globals setup
328 * between here and resident_skip will have already been setup.
334 * Load the main program, or process its program header if it is
337 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */
338 int fd = aux_info[AT_EXECFD]->a_un.a_val;
339 dbg("loading main program");
340 obj_main = map_object(fd, argv0, NULL);
342 if (obj_main == NULL)
344 } else { /* Main program already loaded. */
345 const Elf_Phdr *phdr;
349 dbg("processing main program's program header");
350 assert(aux_info[AT_PHDR] != NULL);
351 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr;
352 assert(aux_info[AT_PHNUM] != NULL);
353 phnum = aux_info[AT_PHNUM]->a_un.a_val;
354 assert(aux_info[AT_PHENT] != NULL);
355 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr));
356 assert(aux_info[AT_ENTRY] != NULL);
357 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr;
358 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL)
362 obj_main->path = xstrdup(argv0);
363 obj_main->mainprog = true;
366 * Get the actual dynamic linker pathname from the executable if
367 * possible. (It should always be possible.) That ensures that
368 * gdb will find the right dynamic linker even if a non-standard
371 if (obj_main->interp != NULL &&
372 strcmp(obj_main->interp, obj_rtld.path) != 0) {
374 obj_rtld.path = xstrdup(obj_main->interp);
375 __progname = obj_rtld.path;
378 digest_dynamic(obj_main);
380 linkmap_add(obj_main);
381 linkmap_add(&obj_rtld);
383 /* Link the main program into the list of objects. */
384 *obj_tail = obj_main;
385 obj_tail = &obj_main->next;
387 obj_main->refcount++;
388 /* Make sure we don't call the main program's init and fini functions. */
389 obj_main->init = obj_main->fini = NULL;
391 /* Initialize a fake symbol for resolving undefined weak references. */
392 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
393 sym_zero.st_shndx = SHN_ABS;
395 dbg("loading LD_PRELOAD libraries");
396 if (load_preload_objects() == -1)
398 preload_tail = obj_tail;
400 dbg("loading needed objects");
401 if (load_needed_objects(obj_main) == -1)
404 /* Make a list of all objects loaded at startup. */
405 for (obj = obj_list; obj != NULL; obj = obj->next)
406 objlist_push_tail(&list_main, obj);
410 if (ld_tracing) { /* We're done */
411 trace_loaded_objects(obj_main);
415 if (ld_resident) /* XXX clean this up! */
418 if (getenv("LD_DUMP_REL_PRE") != NULL) {
419 dump_relocations(obj_main);
423 if (relocate_objects(obj_main,
424 ld_bind_now != NULL && *ld_bind_now != '\0') == -1)
427 dbg("doing copy relocations");
428 if (do_copy_relocations(obj_main) == -1)
433 if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) {
434 if (exec_sys_unregister(-1) < 0) {
435 dbg("exec_sys_unregister failed %d\n", errno);
438 dbg("exec_sys_unregister success\n");
442 if (getenv("LD_DUMP_REL_POST") != NULL) {
443 dump_relocations(obj_main);
447 dbg("initializing key program variables");
448 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : "");
449 set_program_var("environ", env);
451 if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) {
452 extern void resident_start(void);
454 if (exec_sys_register(resident_start) < 0) {
455 dbg("exec_sys_register failed %d\n", errno);
458 dbg("exec_sys_register success\n");
462 dbg("initializing thread locks");
463 lockdflt_init(&lockinfo);
464 lockinfo.thelock = lockinfo.lock_create(lockinfo.context);
466 /* Make a list of init functions to call. */
467 objlist_init(&initlist);
468 initlist_add_objects(obj_list, preload_tail, &initlist);
470 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */
472 objlist_call_init(&initlist);
474 objlist_clear(&initlist);
479 dbg("transferring control to program entry point = %p", obj_main->entry);
481 /* Return the exit procedure and the program entry point. */
482 *exit_proc = rtld_exit;
484 return (func_ptr_type) obj_main->entry;
488 _rtld_bind(Obj_Entry *obj, Elf_Word reloff)
492 const Obj_Entry *defobj;
498 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff);
500 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff);
502 where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
503 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
507 target = (Elf_Addr)(defobj->relocbase + def->st_value);
509 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"",
510 defobj->strtab + def->st_name, basename(obj->path),
511 (void *)target, basename(defobj->path));
513 reloc_jmpslot(where, target);
519 * Error reporting function. Use it like printf. If formats the message
520 * into a buffer, and sets things up so that the next call to dlerror()
521 * will return the message.
524 _rtld_error(const char *fmt, ...)
526 static char buf[512];
530 vsnprintf(buf, sizeof buf, fmt, ap);
536 * Return a dynamically-allocated copy of the current error message, if any.
541 return error_message == NULL ? NULL : xstrdup(error_message);
545 * Restore the current error message from a copy which was previously saved
546 * by errmsg_save(). The copy is freed.
549 errmsg_restore(char *saved_msg)
551 if (saved_msg == NULL)
552 error_message = NULL;
554 _rtld_error("%s", saved_msg);
560 basename(const char *name)
562 const char *p = strrchr(name, '/');
563 return p != NULL ? p + 1 : name;
569 const char *msg = dlerror();
577 * Process a shared object's DYNAMIC section, and save the important
578 * information in its Obj_Entry structure.
581 digest_dynamic(Obj_Entry *obj)
584 Needed_Entry **needed_tail = &obj->needed;
585 const Elf_Dyn *dyn_rpath = NULL;
586 int plttype = DT_REL;
588 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) {
589 switch (dynp->d_tag) {
592 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr);
596 obj->relsize = dynp->d_un.d_val;
600 assert(dynp->d_un.d_val == sizeof(Elf_Rel));
604 obj->pltrel = (const Elf_Rel *)
605 (obj->relocbase + dynp->d_un.d_ptr);
609 obj->pltrelsize = dynp->d_un.d_val;
613 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr);
617 obj->relasize = dynp->d_un.d_val;
621 assert(dynp->d_un.d_val == sizeof(Elf_Rela));
625 plttype = dynp->d_un.d_val;
626 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA);
630 obj->symtab = (const Elf_Sym *)
631 (obj->relocbase + dynp->d_un.d_ptr);
635 assert(dynp->d_un.d_val == sizeof(Elf_Sym));
639 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr);
643 obj->strsize = dynp->d_un.d_val;
648 const Elf_Addr *hashtab = (const Elf_Addr *)
649 (obj->relocbase + dynp->d_un.d_ptr);
650 obj->nbuckets = hashtab[0];
651 obj->nchains = hashtab[1];
652 obj->buckets = hashtab + 2;
653 obj->chains = obj->buckets + obj->nbuckets;
659 Needed_Entry *nep = NEW(Needed_Entry);
660 nep->name = dynp->d_un.d_val;
665 needed_tail = &nep->next;
670 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr);
678 obj->symbolic = true;
682 case DT_RUNPATH: /* XXX: process separately */
684 * We have to wait until later to process this, because we
685 * might not have gotten the address of the string table yet.
691 /* Not used by the dynamic linker. */
695 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
699 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
703 /* XXX - not implemented yet */
704 dbg("Filling in DT_DEBUG entry");
705 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug;
709 if (dynp->d_un.d_val & DF_ORIGIN) {
710 obj->origin_path = xmalloc(PATH_MAX);
711 if (rtld_dirname(obj->path, obj->origin_path) == -1)
714 if (dynp->d_un.d_val & DF_SYMBOLIC)
715 obj->symbolic = true;
716 if (dynp->d_un.d_val & DF_TEXTREL)
718 if (dynp->d_un.d_val & DF_BIND_NOW)
719 obj->bind_now = true;
720 if (dynp->d_un.d_val & DF_STATIC_TLS)
725 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag);
732 if (plttype == DT_RELA) {
733 obj->pltrela = (const Elf_Rela *) obj->pltrel;
735 obj->pltrelasize = obj->pltrelsize;
739 if (dyn_rpath != NULL)
740 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val;
744 * Process a shared object's program header. This is used only for the
745 * main program, when the kernel has already loaded the main program
746 * into memory before calling the dynamic linker. It creates and
747 * returns an Obj_Entry structure.
750 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
753 const Elf_Phdr *phlimit = phdr + phnum;
758 for (ph = phdr; ph < phlimit; ph++) {
759 switch (ph->p_type) {
762 if ((const Elf_Phdr *)ph->p_vaddr != phdr) {
763 _rtld_error("%s: invalid PT_PHDR", path);
766 obj->phdr = (const Elf_Phdr *) ph->p_vaddr;
767 obj->phsize = ph->p_memsz;
771 obj->interp = (const char *) ph->p_vaddr;
775 if (nsegs == 0) { /* First load segment */
776 obj->vaddrbase = trunc_page(ph->p_vaddr);
777 obj->mapbase = (caddr_t) obj->vaddrbase;
778 obj->relocbase = obj->mapbase - obj->vaddrbase;
779 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
781 } else { /* Last load segment */
782 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) -
789 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr;
794 _rtld_error("%s: too few PT_LOAD segments", path);
803 dlcheck(void *handle)
807 for (obj = obj_list; obj != NULL; obj = obj->next)
808 if (obj == (Obj_Entry *) handle)
811 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) {
812 _rtld_error("Invalid shared object handle %p", handle);
819 * If the given object is already in the donelist, return true. Otherwise
820 * add the object to the list and return false.
823 donelist_check(DoneList *dlp, const Obj_Entry *obj)
827 for (i = 0; i < dlp->num_used; i++)
828 if (dlp->objs[i] == obj)
831 * Our donelist allocation should always be sufficient. But if
832 * our threads locking isn't working properly, more shared objects
833 * could have been loaded since we allocated the list. That should
834 * never happen, but we'll handle it properly just in case it does.
836 if (dlp->num_used < dlp->num_alloc)
837 dlp->objs[dlp->num_used++] = obj;
842 * Hash function for symbol table lookup. Don't even think about changing
843 * this. It is specified by the System V ABI.
846 elf_hash(const char *name)
848 const unsigned char *p = (const unsigned char *) name;
854 if ((g = h & 0xf0000000) != 0)
862 * Find the library with the given name, and return its full pathname.
863 * The returned string is dynamically allocated. Generates an error
864 * message and returns NULL if the library cannot be found.
866 * If the second argument is non-NULL, then it refers to an already-
867 * loaded shared object, whose library search path will be searched.
869 * The search order is:
871 * rpath in the referencing file
876 find_library(const char *name, const Obj_Entry *refobj)
880 if (strchr(name, '/') != NULL) { /* Hard coded pathname */
881 if (name[0] != '/' && !trust) {
882 _rtld_error("Absolute pathname required for shared object \"%s\"",
886 return xstrdup(name);
889 dbg(" Searching for \"%s\"", name);
891 if ((pathname = search_library_path(name, ld_library_path)) != NULL ||
893 (pathname = search_library_path(name, refobj->rpath)) != NULL) ||
894 (pathname = search_library_path(name, gethints())) != NULL ||
895 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL)
898 if(refobj != NULL && refobj->path != NULL) {
899 _rtld_error("Shared object \"%s\" not found, required by \"%s\"",
900 name, basename(refobj->path));
902 _rtld_error("Shared object \"%s\" not found", name);
908 * Given a symbol number in a referencing object, find the corresponding
909 * definition of the symbol. Returns a pointer to the symbol, or NULL if
910 * no definition was found. Returns a pointer to the Obj_Entry of the
911 * defining object via the reference parameter DEFOBJ_OUT.
914 find_symdef(unsigned long symnum, const Obj_Entry *refobj,
915 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache)
919 const Obj_Entry *defobj;
924 * If we have already found this symbol, get the information from
927 if (symnum >= refobj->nchains)
928 return NULL; /* Bad object */
929 if (cache != NULL && cache[symnum].sym != NULL) {
930 *defobj_out = cache[symnum].obj;
931 return cache[symnum].sym;
934 ref = refobj->symtab + symnum;
935 name = refobj->strtab + ref->st_name;
936 hash = elf_hash(name);
939 def = symlook_default(name, hash, refobj, &defobj, in_plt);
942 * If we found no definition and the reference is weak, treat the
943 * symbol as having the value zero.
945 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) {
951 *defobj_out = defobj;
952 /* Record the information in the cache to avoid subsequent lookups. */
954 cache[symnum].sym = def;
955 cache[symnum].obj = defobj;
958 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
963 * Return the search path from the ldconfig hints file, reading it if
964 * necessary. Returns NULL if there are problems with the hints file,
965 * or if the search path there is empty.
974 struct elfhints_hdr hdr;
977 /* Keep from trying again in case the hints file is bad. */
980 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1)
982 if (read(fd, &hdr, sizeof hdr) != sizeof hdr ||
983 hdr.magic != ELFHINTS_MAGIC ||
988 p = xmalloc(hdr.dirlistlen + 1);
989 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 ||
990 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) {
998 return hints[0] != '\0' ? hints : NULL;
1002 init_dag(Obj_Entry *root)
1006 donelist_init(&donelist);
1007 init_dag1(root, root, &donelist);
1011 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp)
1013 const Needed_Entry *needed;
1015 if (donelist_check(dlp, obj))
1017 objlist_push_tail(&obj->dldags, root);
1018 objlist_push_tail(&root->dagmembers, obj);
1019 for (needed = obj->needed; needed != NULL; needed = needed->next)
1020 if (needed->obj != NULL)
1021 init_dag1(root, needed->obj, dlp);
1025 * Initialize the dynamic linker. The argument is the address at which
1026 * the dynamic linker has been mapped into memory. The primary task of
1027 * this function is to relocate the dynamic linker.
1030 init_rtld(caddr_t mapbase)
1033 * Conjure up an Obj_Entry structure for the dynamic linker.
1035 * The "path" member is supposed to be dynamically-allocated, but we
1036 * aren't yet initialized sufficiently to do that. Below we will
1037 * replace the static version with a dynamically-allocated copy.
1039 obj_rtld.path = PATH_RTLD;
1040 obj_rtld.rtld = true;
1041 obj_rtld.mapbase = mapbase;
1043 obj_rtld.relocbase = mapbase;
1045 if (&_DYNAMIC != 0) {
1046 obj_rtld.dynamic = rtld_dynamic(&obj_rtld);
1047 digest_dynamic(&obj_rtld);
1048 assert(obj_rtld.needed == NULL);
1049 assert(!obj_rtld.textrel);
1052 * Temporarily put the dynamic linker entry into the object list, so
1053 * that symbols can be found.
1055 obj_list = &obj_rtld;
1056 obj_tail = &obj_rtld.next;
1059 relocate_objects(&obj_rtld, true);
1062 /* Make the object list empty again. */
1064 obj_tail = &obj_list;
1067 /* Replace the path with a dynamically allocated copy. */
1068 obj_rtld.path = xstrdup(obj_rtld.path);
1070 r_debug.r_brk = r_debug_state;
1071 r_debug.r_state = RT_CONSISTENT;
1075 * Add the init functions from a needed object list (and its recursive
1076 * needed objects) to "list". This is not used directly; it is a helper
1077 * function for initlist_add_objects(). The write lock must be held
1078 * when this function is called.
1081 initlist_add_neededs(Needed_Entry *needed, Objlist *list)
1083 /* Recursively process the successor needed objects. */
1084 if (needed->next != NULL)
1085 initlist_add_neededs(needed->next, list);
1087 /* Process the current needed object. */
1088 if (needed->obj != NULL)
1089 initlist_add_objects(needed->obj, &needed->obj->next, list);
1093 * Scan all of the DAGs rooted in the range of objects from "obj" to
1094 * "tail" and add their init functions to "list". This recurses over
1095 * the DAGs and ensure the proper init ordering such that each object's
1096 * needed libraries are initialized before the object itself. At the
1097 * same time, this function adds the objects to the global finalization
1098 * list "list_fini" in the opposite order. The write lock must be
1099 * held when this function is called.
1102 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list)
1106 obj->init_done = true;
1108 /* Recursively process the successor objects. */
1109 if (&obj->next != tail)
1110 initlist_add_objects(obj->next, tail, list);
1112 /* Recursively process the needed objects. */
1113 if (obj->needed != NULL)
1114 initlist_add_neededs(obj->needed, list);
1116 /* Add the object to the init list. */
1117 if (obj->init != NULL)
1118 objlist_push_tail(list, obj);
1120 /* Add the object to the global fini list in the reverse order. */
1121 if (obj->fini != NULL)
1122 objlist_push_head(&list_fini, obj);
1126 is_exported(const Elf_Sym *def)
1128 func_ptr_type value;
1129 const func_ptr_type *p;
1131 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value);
1132 for (p = exports; *p != NULL; p++)
1139 * Given a shared object, traverse its list of needed objects, and load
1140 * each of them. Returns 0 on success. Generates an error message and
1141 * returns -1 on failure.
1144 load_needed_objects(Obj_Entry *first)
1148 for (obj = first; obj != NULL; obj = obj->next) {
1149 Needed_Entry *needed;
1151 for (needed = obj->needed; needed != NULL; needed = needed->next) {
1152 const char *name = obj->strtab + needed->name;
1153 char *path = find_library(name, obj);
1156 if (path == NULL && !ld_tracing)
1160 needed->obj = load_object(path);
1161 if (needed->obj == NULL && !ld_tracing)
1162 return -1; /* XXX - cleanup */
1171 load_preload_objects(void)
1173 char *p = ld_preload;
1174 static const char delim[] = " \t:;";
1179 p += strspn(p, delim);
1180 while (*p != '\0') {
1181 size_t len = strcspn(p, delim);
1187 if ((path = find_library(p, NULL)) == NULL)
1189 if (load_object(path) == NULL)
1190 return -1; /* XXX - cleanup */
1193 p += strspn(p, delim);
1199 * Returns a pointer to the Obj_Entry for the object with the given path.
1200 * Returns NULL if no matching object was found.
1203 find_object(const char *path)
1207 for (obj = obj_list->next; obj != NULL; obj = obj->next) {
1208 if (strcmp(obj->path, path) == 0)
1215 * Returns a pointer to the Obj_Entry for the object matching device and
1216 * inode of the given path. If no matching object was found, the descriptor
1217 * is returned in fd.
1218 * Returns with obj == NULL && fd == -1 on error.
1221 find_object2(const char *path, int *fd, struct stat *sb)
1225 if ((*fd = open(path, O_RDONLY)) == -1) {
1226 _rtld_error("Cannot open \"%s\"", path);
1230 if (fstat(*fd, sb) == -1) {
1231 _rtld_error("Cannot fstat \"%s\"", path);
1237 for (obj = obj_list->next; obj != NULL; obj = obj->next) {
1238 if (obj->ino == sb->st_ino && obj->dev == sb->st_dev) {
1248 * Load a shared object into memory, if it is not already loaded. The
1249 * argument must be a string allocated on the heap. This function assumes
1250 * responsibility for freeing it when necessary.
1252 * Returns a pointer to the Obj_Entry for the object. Returns NULL
1256 load_object(char *path)
1262 obj = find_object(path);
1269 obj = find_object2(path, &fd, &sb);
1274 } else if (fd == -1) {
1279 dbg("loading \"%s\"", path);
1280 obj = map_object(fd, path, &sb);
1288 digest_dynamic(obj);
1291 obj_tail = &obj->next;
1293 linkmap_add(obj); /* for GDB & dlinfo() */
1295 dbg(" %p .. %p: %s", obj->mapbase, obj->mapbase + obj->mapsize - 1,
1298 dbg(" WARNING: %s has impure text", obj->path);
1305 * Check for locking violations and die if one is found.
1312 rcount = lockinfo.rcount;
1313 wcount = lockinfo.wcount;
1314 assert(rcount >= 0);
1315 assert(wcount >= 0);
1316 if (wcount > 1 || (wcount != 0 && rcount != 0)) {
1317 _rtld_error("Application locking error: %d readers and %d writers"
1318 " in dynamic linker. See DLLOCKINIT(3) in manual pages.",
1325 obj_from_addr(const void *addr)
1329 for (obj = obj_list; obj != NULL; obj = obj->next) {
1330 if (addr < (void *) obj->mapbase)
1332 if (addr < (void *) (obj->mapbase + obj->mapsize))
1339 * Call the finalization functions for each of the objects in "list"
1340 * which are unreferenced. All of the objects are expected to have
1341 * non-NULL fini functions.
1344 objlist_call_fini(Objlist *list)
1350 * Preserve the current error message since a fini function might
1351 * call into the dynamic linker and overwrite it.
1353 saved_msg = errmsg_save();
1354 STAILQ_FOREACH(elm, list, link) {
1355 if (elm->obj->refcount == 0) {
1356 dbg("calling fini function for %s", elm->obj->path);
1357 (*elm->obj->fini)();
1360 errmsg_restore(saved_msg);
1364 * Call the initialization functions for each of the objects in
1365 * "list". All of the objects are expected to have non-NULL init
1369 objlist_call_init(Objlist *list)
1375 * Preserve the current error message since an init function might
1376 * call into the dynamic linker and overwrite it.
1378 saved_msg = errmsg_save();
1379 STAILQ_FOREACH(elm, list, link) {
1380 dbg("calling init function for %s", elm->obj->path);
1381 (*elm->obj->init)();
1383 errmsg_restore(saved_msg);
1387 objlist_clear(Objlist *list)
1391 while (!STAILQ_EMPTY(list)) {
1392 elm = STAILQ_FIRST(list);
1393 STAILQ_REMOVE_HEAD(list, link);
1398 static Objlist_Entry *
1399 objlist_find(Objlist *list, const Obj_Entry *obj)
1403 STAILQ_FOREACH(elm, list, link)
1404 if (elm->obj == obj)
1410 objlist_init(Objlist *list)
1416 objlist_push_head(Objlist *list, Obj_Entry *obj)
1420 elm = NEW(Objlist_Entry);
1422 STAILQ_INSERT_HEAD(list, elm, link);
1426 objlist_push_tail(Objlist *list, Obj_Entry *obj)
1430 elm = NEW(Objlist_Entry);
1432 STAILQ_INSERT_TAIL(list, elm, link);
1436 objlist_remove(Objlist *list, Obj_Entry *obj)
1440 if ((elm = objlist_find(list, obj)) != NULL) {
1441 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link);
1447 * Remove all of the unreferenced objects from "list".
1450 objlist_remove_unref(Objlist *list)
1455 STAILQ_INIT(&newlist);
1456 while (!STAILQ_EMPTY(list)) {
1457 elm = STAILQ_FIRST(list);
1458 STAILQ_REMOVE_HEAD(list, link);
1459 if (elm->obj->refcount == 0)
1462 STAILQ_INSERT_TAIL(&newlist, elm, link);
1468 * Relocate newly-loaded shared objects. The argument is a pointer to
1469 * the Obj_Entry for the first such object. All objects from the first
1470 * to the end of the list of objects are relocated. Returns 0 on success,
1474 relocate_objects(Obj_Entry *first, bool bind_now)
1478 for (obj = first; obj != NULL; obj = obj->next) {
1479 if (obj != &obj_rtld)
1480 dbg("relocating \"%s\"", obj->path);
1481 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL ||
1482 obj->symtab == NULL || obj->strtab == NULL) {
1483 _rtld_error("%s: Shared object has no run-time symbol table",
1489 /* There are relocations to the write-protected text segment. */
1490 if (mprotect(obj->mapbase, obj->textsize,
1491 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
1492 _rtld_error("%s: Cannot write-enable text segment: %s",
1493 obj->path, strerror(errno));
1498 /* Process the non-PLT relocations. */
1499 if (reloc_non_plt(obj, &obj_rtld))
1503 * Reprotect the text segment. Make sure it is included in the
1504 * core dump since we modified it. This unfortunately causes the
1505 * entire text segment to core-out but we don't have much of a
1506 * choice. We could try to only reenable core dumps on pages
1507 * in which relocations occured but that is likely most of the text
1508 * pages anyway, and even that would not work because the rest of
1509 * the text pages would wind up as a read-only OBJT_DEFAULT object
1510 * (created due to our modifications) backed by the original OBJT_VNODE
1511 * object, and the ELF coredump code is currently only able to dump
1512 * vnode records for pure vnode-backed mappings, not vnode backings
1513 * to memory objects.
1516 madvise(obj->mapbase, obj->textsize, MADV_CORE);
1517 if (mprotect(obj->mapbase, obj->textsize,
1518 PROT_READ|PROT_EXEC) == -1) {
1519 _rtld_error("%s: Cannot write-protect text segment: %s",
1520 obj->path, strerror(errno));
1525 /* Process the PLT relocations. */
1526 if (reloc_plt(obj) == -1)
1528 /* Relocate the jump slots if we are doing immediate binding. */
1529 if (obj->bind_now || bind_now)
1530 if (reloc_jmpslots(obj) == -1)
1535 * Set up the magic number and version in the Obj_Entry. These
1536 * were checked in the crt1.o from the original ElfKit, so we
1537 * set them for backward compatibility.
1539 obj->magic = RTLD_MAGIC;
1540 obj->version = RTLD_VERSION;
1542 /* Set the special PLT or GOT entries. */
1550 * Cleanup procedure. It will be called (by the atexit mechanism) just
1551 * before the process exits.
1559 /* Clear all the reference counts so the fini functions will be called. */
1560 for (obj = obj_list; obj != NULL; obj = obj->next)
1562 objlist_call_fini(&list_fini);
1563 /* No need to remove the items from the list, since we are exiting. */
1567 path_enumerate(const char *path, path_enum_proc callback, void *arg)
1572 path += strspn(path, ":;");
1573 while (*path != '\0') {
1577 len = strcspn(path, ":;");
1578 res = callback(path, len, arg);
1584 path += strspn(path, ":;");
1590 struct try_library_args {
1598 try_library_path(const char *dir, size_t dirlen, void *param)
1600 struct try_library_args *arg;
1603 if (*dir == '/' || trust) {
1606 if (dirlen + 1 + arg->namelen + 1 > arg->buflen)
1609 pathname = arg->buffer;
1610 strncpy(pathname, dir, dirlen);
1611 pathname[dirlen] = '/';
1612 strcpy(pathname + dirlen + 1, arg->name);
1614 dbg(" Trying \"%s\"", pathname);
1615 if (access(pathname, F_OK) == 0) { /* We found it */
1616 pathname = xmalloc(dirlen + 1 + arg->namelen + 1);
1617 strcpy(pathname, arg->buffer);
1625 search_library_path(const char *name, const char *path)
1628 struct try_library_args arg;
1634 arg.namelen = strlen(name);
1635 arg.buffer = xmalloc(PATH_MAX);
1636 arg.buflen = PATH_MAX;
1638 p = path_enumerate(path, try_library_path, &arg);
1646 dlclose(void *handle)
1651 root = dlcheck(handle);
1657 /* Unreference the object and its dependencies. */
1658 root->dl_refcount--;
1661 if (root->refcount == 0) {
1663 * The object is no longer referenced, so we must unload it.
1664 * First, call the fini functions with no locks held.
1667 objlist_call_fini(&list_fini);
1669 objlist_remove_unref(&list_fini);
1671 /* Finish cleaning up the newly-unreferenced objects. */
1672 GDB_STATE(RT_DELETE,&root->linkmap);
1673 unload_object(root);
1674 GDB_STATE(RT_CONSISTENT,NULL);
1683 char *msg = error_message;
1684 error_message = NULL;
1689 * This function is deprecated and has no effect.
1692 dllockinit(void *context,
1693 void *(*lock_create)(void *context),
1694 void (*rlock_acquire)(void *lock),
1695 void (*wlock_acquire)(void *lock),
1696 void (*lock_release)(void *lock),
1697 void (*lock_destroy)(void *lock),
1698 void (*context_destroy)(void *context))
1700 static void *cur_context;
1701 static void (*cur_context_destroy)(void *);
1703 /* Just destroy the context from the previous call, if necessary. */
1704 if (cur_context_destroy != NULL)
1705 cur_context_destroy(cur_context);
1706 cur_context = context;
1707 cur_context_destroy = context_destroy;
1711 dlopen(const char *name, int mode)
1713 Obj_Entry **old_obj_tail;
1718 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1";
1719 if (ld_tracing != NULL)
1720 environ = (char **)*get_program_var_addr("environ");
1722 objlist_init(&initlist);
1725 GDB_STATE(RT_ADD,NULL);
1727 old_obj_tail = obj_tail;
1733 char *path = find_library(name, obj_main);
1735 obj = load_object(path);
1740 if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL)
1741 objlist_push_tail(&list_global, obj);
1742 mode &= RTLD_MODEMASK;
1743 if (*old_obj_tail != NULL) { /* We loaded something new. */
1744 assert(*old_obj_tail == obj);
1746 result = load_needed_objects(obj);
1747 if (result != -1 && ld_tracing)
1751 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) {
1754 if (obj->refcount == 0)
1758 /* Make list of init functions to call. */
1759 initlist_add_objects(obj, &obj->next, &initlist);
1761 } else if (ld_tracing)
1765 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL);
1767 /* Call the init functions with no locks held. */
1769 objlist_call_init(&initlist);
1771 objlist_clear(&initlist);
1775 trace_loaded_objects(obj);
1781 dlsym(void *handle, const char *name)
1783 const Obj_Entry *obj;
1786 const Obj_Entry *defobj;
1788 hash = elf_hash(name);
1793 if (handle == NULL || handle == RTLD_NEXT ||
1794 handle == RTLD_DEFAULT || handle == RTLD_SELF) {
1797 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1798 if ((obj = obj_from_addr(retaddr)) == NULL) {
1799 _rtld_error("Cannot determine caller's shared object");
1803 if (handle == NULL) { /* Just the caller's shared object. */
1804 def = symlook_obj(name, hash, obj, true);
1806 } else if (handle == RTLD_NEXT || /* Objects after caller's */
1807 handle == RTLD_SELF) { /* ... caller included */
1808 if (handle == RTLD_NEXT)
1810 for (; obj != NULL; obj = obj->next) {
1811 if ((def = symlook_obj(name, hash, obj, true)) != NULL) {
1817 assert(handle == RTLD_DEFAULT);
1818 def = symlook_default(name, hash, obj, &defobj, true);
1821 if ((obj = dlcheck(handle)) == NULL) {
1826 if (obj->mainprog) {
1829 /* Search main program and all libraries loaded by it. */
1830 donelist_init(&donelist);
1831 def = symlook_list(name, hash, &list_main, &defobj, true,
1835 * XXX - This isn't correct. The search should include the whole
1836 * DAG rooted at the given object.
1838 def = symlook_obj(name, hash, obj, true);
1845 return defobj->relocbase + def->st_value;
1848 _rtld_error("Undefined symbol \"%s\"", name);
1854 dladdr(const void *addr, Dl_info *info)
1856 const Obj_Entry *obj;
1859 unsigned long symoffset;
1862 obj = obj_from_addr(addr);
1864 _rtld_error("No shared object contains address");
1868 info->dli_fname = obj->path;
1869 info->dli_fbase = obj->mapbase;
1870 info->dli_saddr = (void *)0;
1871 info->dli_sname = NULL;
1874 * Walk the symbol list looking for the symbol whose address is
1875 * closest to the address sent in.
1877 for (symoffset = 0; symoffset < obj->nchains; symoffset++) {
1878 def = obj->symtab + symoffset;
1881 * For skip the symbol if st_shndx is either SHN_UNDEF or
1884 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON)
1888 * If the symbol is greater than the specified address, or if it
1889 * is further away from addr than the current nearest symbol,
1892 symbol_addr = obj->relocbase + def->st_value;
1893 if (symbol_addr > addr || symbol_addr < info->dli_saddr)
1896 /* Update our idea of the nearest symbol. */
1897 info->dli_sname = obj->strtab + def->st_name;
1898 info->dli_saddr = symbol_addr;
1901 if (info->dli_saddr == addr)
1909 dlinfo(void *handle, int request, void *p)
1911 const Obj_Entry *obj;
1916 if (handle == NULL || handle == RTLD_SELF) {
1919 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1920 if ((obj = obj_from_addr(retaddr)) == NULL)
1921 _rtld_error("Cannot determine caller's shared object");
1923 obj = dlcheck(handle);
1932 case RTLD_DI_LINKMAP:
1933 *((struct link_map const **)p) = &obj->linkmap;
1935 case RTLD_DI_ORIGIN:
1936 error = rtld_dirname(obj->path, p);
1939 case RTLD_DI_SERINFOSIZE:
1940 case RTLD_DI_SERINFO:
1941 error = do_search_info(obj, request, (struct dl_serinfo *)p);
1945 _rtld_error("Invalid request %d passed to dlinfo()", request);
1954 struct fill_search_info_args {
1957 Dl_serinfo *serinfo;
1958 Dl_serpath *serpath;
1963 fill_search_info(const char *dir, size_t dirlen, void *param)
1965 struct fill_search_info_args *arg;
1969 if (arg->request == RTLD_DI_SERINFOSIZE) {
1970 arg->serinfo->dls_cnt ++;
1971 arg->serinfo->dls_size += dirlen + 1;
1973 struct dl_serpath *s_entry;
1975 s_entry = arg->serpath;
1976 s_entry->dls_name = arg->strspace;
1977 s_entry->dls_flags = arg->flags;
1979 strncpy(arg->strspace, dir, dirlen);
1980 arg->strspace[dirlen] = '\0';
1982 arg->strspace += dirlen + 1;
1990 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info)
1992 struct dl_serinfo _info;
1993 struct fill_search_info_args args;
1995 args.request = RTLD_DI_SERINFOSIZE;
1996 args.serinfo = &_info;
1998 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath);
2001 path_enumerate(ld_library_path, fill_search_info, &args);
2002 path_enumerate(obj->rpath, fill_search_info, &args);
2003 path_enumerate(gethints(), fill_search_info, &args);
2004 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args);
2007 if (request == RTLD_DI_SERINFOSIZE) {
2008 info->dls_size = _info.dls_size;
2009 info->dls_cnt = _info.dls_cnt;
2013 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) {
2014 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()");
2018 args.request = RTLD_DI_SERINFO;
2019 args.serinfo = info;
2020 args.serpath = &info->dls_serpath[0];
2021 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt];
2023 args.flags = LA_SER_LIBPATH;
2024 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL)
2027 args.flags = LA_SER_RUNPATH;
2028 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL)
2031 args.flags = LA_SER_CONFIG;
2032 if (path_enumerate(gethints(), fill_search_info, &args) != NULL)
2035 args.flags = LA_SER_DEFAULT;
2036 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL)
2042 rtld_dirname(const char *path, char *bname)
2046 /* Empty or NULL string gets treated as "." */
2047 if (path == NULL || *path == '\0') {
2053 /* Strip trailing slashes */
2054 endp = path + strlen(path) - 1;
2055 while (endp > path && *endp == '/')
2058 /* Find the start of the dir */
2059 while (endp > path && *endp != '/')
2062 /* Either the dir is "/" or there are no slashes */
2064 bname[0] = *endp == '/' ? '/' : '.';
2070 } while (endp > path && *endp == '/');
2073 if (endp - path + 2 > PATH_MAX)
2075 _rtld_error("Filename is too long: %s", path);
2079 strncpy(bname, path, endp - path + 1);
2080 bname[endp - path + 1] = '\0';
2085 linkmap_add(Obj_Entry *obj)
2087 struct link_map *l = &obj->linkmap;
2088 struct link_map *prev;
2090 obj->linkmap.l_name = obj->path;
2091 obj->linkmap.l_addr = obj->mapbase;
2092 obj->linkmap.l_ld = obj->dynamic;
2094 /* GDB needs load offset on MIPS to use the symbols */
2095 obj->linkmap.l_offs = obj->relocbase;
2098 if (r_debug.r_map == NULL) {
2104 * Scan to the end of the list, but not past the entry for the
2105 * dynamic linker, which we want to keep at the very end.
2107 for (prev = r_debug.r_map;
2108 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap;
2109 prev = prev->l_next)
2112 /* Link in the new entry. */
2114 l->l_next = prev->l_next;
2115 if (l->l_next != NULL)
2116 l->l_next->l_prev = l;
2121 linkmap_delete(Obj_Entry *obj)
2123 struct link_map *l = &obj->linkmap;
2125 if (l->l_prev == NULL) {
2126 if ((r_debug.r_map = l->l_next) != NULL)
2127 l->l_next->l_prev = NULL;
2131 if ((l->l_prev->l_next = l->l_next) != NULL)
2132 l->l_next->l_prev = l->l_prev;
2136 * Function for the debugger to set a breakpoint on to gain control.
2138 * The two parameters allow the debugger to easily find and determine
2139 * what the runtime loader is doing and to whom it is doing it.
2141 * When the loadhook trap is hit (r_debug_state, set at program
2142 * initialization), the arguments can be found on the stack:
2144 * +8 struct link_map *m
2145 * +4 struct r_debug *rd
2149 r_debug_state(struct r_debug* rd, struct link_map *m)
2154 * Get address of the pointer variable in the main program.
2156 static const void **
2157 get_program_var_addr(const char *name)
2159 const Obj_Entry *obj;
2162 hash = elf_hash(name);
2163 for (obj = obj_main; obj != NULL; obj = obj->next) {
2166 if ((def = symlook_obj(name, hash, obj, false)) != NULL) {
2169 addr = (const void **)(obj->relocbase + def->st_value);
2177 * Set a pointer variable in the main program to the given value. This
2178 * is used to set key variables such as "environ" before any of the
2179 * init functions are called.
2182 set_program_var(const char *name, const void *value)
2186 if ((addr = get_program_var_addr(name)) != NULL) {
2187 dbg("\"%s\": *%p <-- %p", name, addr, value);
2193 * This is a special version of getenv which is far more efficient
2194 * at finding LD_ environment vars.
2198 _getenv_ld(const char *id)
2202 int idlen = strlen(id);
2204 if (ld_index == LD_ARY_CACHE)
2206 if (ld_index == 0) {
2207 for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) {
2208 if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_')
2215 for (i = ld_index - 1; i >= 0; --i) {
2216 if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=')
2217 return(ld_ary[i] + idlen + 1);
2223 * Given a symbol name in a referencing object, find the corresponding
2224 * definition of the symbol. Returns a pointer to the symbol, or NULL if
2225 * no definition was found. Returns a pointer to the Obj_Entry of the
2226 * defining object via the reference parameter DEFOBJ_OUT.
2228 static const Elf_Sym *
2229 symlook_default(const char *name, unsigned long hash,
2230 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt)
2234 const Elf_Sym *symp;
2235 const Obj_Entry *obj;
2236 const Obj_Entry *defobj;
2237 const Objlist_Entry *elm;
2240 donelist_init(&donelist);
2242 /* Look first in the referencing object if linked symbolically. */
2243 if (refobj->symbolic && !donelist_check(&donelist, refobj)) {
2244 symp = symlook_obj(name, hash, refobj, in_plt);
2251 /* Search all objects loaded at program start up. */
2252 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2253 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist);
2255 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2261 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */
2262 STAILQ_FOREACH(elm, &list_global, link) {
2263 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2265 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2268 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2274 /* Search all dlopened DAGs containing the referencing object. */
2275 STAILQ_FOREACH(elm, &refobj->dldags, link) {
2276 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2278 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2281 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2288 * Search the dynamic linker itself, and possibly resolve the
2289 * symbol from there. This is how the application links to
2290 * dynamic linker services such as dlopen. Only the values listed
2291 * in the "exports" array can be resolved from the dynamic linker.
2293 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2294 symp = symlook_obj(name, hash, &obj_rtld, in_plt);
2295 if (symp != NULL && is_exported(symp)) {
2302 *defobj_out = defobj;
2306 static const Elf_Sym *
2307 symlook_list(const char *name, unsigned long hash, Objlist *objlist,
2308 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)
2310 const Elf_Sym *symp;
2312 const Obj_Entry *defobj;
2313 const Objlist_Entry *elm;
2317 STAILQ_FOREACH(elm, objlist, link) {
2318 if (donelist_check(dlp, elm->obj))
2320 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) {
2321 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) {
2324 if (ELF_ST_BIND(def->st_info) != STB_WEAK)
2330 *defobj_out = defobj;
2335 * Search the symbol table of a single shared object for a symbol of
2336 * the given name. Returns a pointer to the symbol, or NULL if no
2337 * definition was found.
2339 * The symbol's hash value is passed in for efficiency reasons; that
2340 * eliminates many recomputations of the hash value.
2343 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj,
2346 if (obj->buckets != NULL) {
2347 unsigned long symnum = obj->buckets[hash % obj->nbuckets];
2349 while (symnum != STN_UNDEF) {
2350 const Elf_Sym *symp;
2353 if (symnum >= obj->nchains)
2354 return NULL; /* Bad object */
2355 symp = obj->symtab + symnum;
2356 strp = obj->strtab + symp->st_name;
2358 if (name[0] == strp[0] && strcmp(name, strp) == 0)
2359 return symp->st_shndx != SHN_UNDEF ||
2360 (!in_plt && symp->st_value != 0 &&
2361 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL;
2363 symnum = obj->chains[symnum];
2370 trace_loaded_objects(Obj_Entry *obj)
2372 const char *fmt1, *fmt2, *fmt, *main_local;
2375 if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL)
2378 if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL)
2379 fmt1 = "\t%o => %p (%x)\n";
2381 if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL)
2382 fmt2 = "\t%o (%x)\n";
2384 for (; obj; obj = obj->next) {
2385 Needed_Entry *needed;
2389 for (needed = obj->needed; needed; needed = needed->next) {
2390 if (needed->obj != NULL) {
2391 if (needed->obj->traced)
2393 needed->obj->traced = true;
2394 path = needed->obj->path;
2398 name = (char *)obj->strtab + needed->name;
2399 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */
2401 fmt = is_lib ? fmt1 : fmt2;
2402 while ((c = *fmt++) != '\0') {
2428 printf("%s", main_local);
2431 printf("%s", obj_main->path);
2438 printf("%d", sodp->sod_major);
2441 printf("%d", sodp->sod_minor);
2448 printf("%p", needed->obj ? needed->obj->mapbase : 0);
2460 * Unload a dlopened object and its dependencies from memory and from
2461 * our data structures. It is assumed that the DAG rooted in the
2462 * object has already been unreferenced, and that the object has a
2463 * reference count of 0.
2466 unload_object(Obj_Entry *root)
2471 assert(root->refcount == 0);
2474 * Pass over the DAG removing unreferenced objects from
2475 * appropriate lists.
2477 unlink_object(root);
2479 /* Unmap all objects that are no longer referenced. */
2480 linkp = &obj_list->next;
2481 while ((obj = *linkp) != NULL) {
2482 if (obj->refcount == 0) {
2483 dbg("unloading \"%s\"", obj->path);
2484 munmap(obj->mapbase, obj->mapsize);
2485 linkmap_delete(obj);
2496 unlink_object(Obj_Entry *root)
2498 const Needed_Entry *needed;
2501 if (root->refcount == 0) {
2502 /* Remove the object from the RTLD_GLOBAL list. */
2503 objlist_remove(&list_global, root);
2505 /* Remove the object from all objects' DAG lists. */
2506 STAILQ_FOREACH(elm, &root->dagmembers , link)
2507 objlist_remove(&elm->obj->dldags, root);
2510 for (needed = root->needed; needed != NULL; needed = needed->next)
2511 if (needed->obj != NULL)
2512 unlink_object(needed->obj);
2516 unref_dag(Obj_Entry *root)
2518 const Needed_Entry *needed;
2520 if (root->refcount == 0)
2523 if (root->refcount == 0)
2524 for (needed = root->needed; needed != NULL; needed = needed->next)
2525 if (needed->obj != NULL)
2526 unref_dag(needed->obj);