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 1.7 2004/01/20 21:32:46 dillon 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 END_SYM "_end"
59 #define PATH_RTLD "/usr/libexec/ld-elf.so.1"
60 #define LD_ARY_CACHE 16
63 typedef void (*func_ptr_type)();
64 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg);
67 * This structure provides a reentrant way to keep a list of objects and
68 * check which ones have already been processed in some way.
70 typedef struct Struct_DoneList {
71 const Obj_Entry **objs; /* Array of object pointers */
72 unsigned int num_alloc; /* Allocated size of the array */
73 unsigned int num_used; /* Number of array slots used */
77 * Function declarations.
79 static void die(void);
80 static void digest_dynamic(Obj_Entry *);
81 static const char *_getenv_ld(const char *id);
82 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
83 static Obj_Entry *dlcheck(void *);
84 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *);
85 static bool donelist_check(DoneList *, const Obj_Entry *);
86 static void errmsg_restore(char *);
87 static char *errmsg_save(void);
88 static void *fill_search_info(const char *, size_t, void *);
89 static char *find_library(const char *, const Obj_Entry *);
90 static const char *gethints(void);
91 static void init_dag(Obj_Entry *);
92 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *);
93 static void init_rtld(caddr_t);
94 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list);
95 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail,
97 static bool is_exported(const Elf_Sym *);
98 static void linkmap_add(Obj_Entry *);
99 static void linkmap_delete(Obj_Entry *);
100 static int load_needed_objects(Obj_Entry *);
101 static int load_preload_objects(void);
102 static Obj_Entry *load_object(char *);
103 static void lock_check(void);
104 static Obj_Entry *obj_from_addr(const void *);
105 static void objlist_call_fini(Objlist *);
106 static void objlist_call_init(Objlist *);
107 static void objlist_clear(Objlist *);
108 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *);
109 static void objlist_init(Objlist *);
110 static void objlist_push_head(Objlist *, Obj_Entry *);
111 static void objlist_push_tail(Objlist *, Obj_Entry *);
112 static void objlist_remove(Objlist *, Obj_Entry *);
113 static void objlist_remove_unref(Objlist *);
114 static void *path_enumerate(const char *, path_enum_proc, void *);
115 static int relocate_objects(Obj_Entry *, bool);
116 static int rtld_dirname(const char *, char *);
117 static void rtld_exit(void);
118 static char *search_library_path(const char *, const char *);
119 static const void **get_program_var_addr(const char *name);
120 static void set_program_var(const char *, const void *);
121 static const Elf_Sym *symlook_default(const char *, unsigned long hash,
122 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt);
123 static const Elf_Sym *symlook_list(const char *, unsigned long,
124 Objlist *, const Obj_Entry **, bool in_plt, DoneList *);
125 static void trace_loaded_objects(Obj_Entry *obj);
126 static void unlink_object(Obj_Entry *);
127 static void unload_object(Obj_Entry *);
128 static void unref_dag(Obj_Entry *);
130 void r_debug_state(struct r_debug*, struct link_map*);
135 static char *error_message; /* Message for dlerror(), or NULL */
136 struct r_debug r_debug; /* for GDB; */
137 static bool trust; /* False for setuid and setgid programs */
138 static const char *ld_bind_now; /* Environment variable for immediate binding */
139 static const char *ld_debug; /* Environment variable for debugging */
140 static const char *ld_library_path; /* Environment variable for search path */
141 static char *ld_preload; /* Environment variable for libraries to
143 static const char *ld_tracing; /* Called from ldd(1) to print libs */
144 static Obj_Entry *obj_list; /* Head of linked list of shared objects */
145 static Obj_Entry **obj_tail; /* Link field of last object in list */
146 static Obj_Entry **preload_tail;
147 static Obj_Entry *obj_main; /* The main program shared object */
148 static Obj_Entry obj_rtld; /* The dynamic linker shared object */
149 static unsigned int obj_count; /* Number of objects in obj_list */
150 static int ld_resident; /* Non-zero if resident */
151 static const char *ld_ary[LD_ARY_CACHE];
154 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */
155 STAILQ_HEAD_INITIALIZER(list_global);
156 static Objlist list_main = /* Objects loaded at program startup */
157 STAILQ_HEAD_INITIALIZER(list_main);
158 static Objlist list_fini = /* Objects needing fini() calls */
159 STAILQ_HEAD_INITIALIZER(list_fini);
161 static LockInfo lockinfo;
163 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */
165 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m);
167 extern Elf_Dyn _DYNAMIC;
168 #pragma weak _DYNAMIC
171 * These are the functions the dynamic linker exports to application
172 * programs. They are the only symbols the dynamic linker is willing
173 * to export from itself.
175 static func_ptr_type exports[] = {
176 (func_ptr_type) &_rtld_error,
177 (func_ptr_type) &dlclose,
178 (func_ptr_type) &dlerror,
179 (func_ptr_type) &dlopen,
180 (func_ptr_type) &dlsym,
181 (func_ptr_type) &dladdr,
182 (func_ptr_type) &dllockinit,
183 (func_ptr_type) &dlinfo,
188 * Global declarations normally provided by crt1. The dynamic linker is
189 * not built with crt1, so we have to provide them ourselves.
195 * Fill in a DoneList with an allocation large enough to hold all of
196 * the currently-loaded objects. Keep this as a macro since it calls
197 * alloca and we want that to occur within the scope of the caller.
199 #define donelist_init(dlp) \
200 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \
201 assert((dlp)->objs != NULL), \
202 (dlp)->num_alloc = obj_count, \
208 lockinfo.rlock_acquire(lockinfo.thelock);
209 atomic_incr_int(&lockinfo.rcount);
216 lockinfo.wlock_acquire(lockinfo.thelock);
217 atomic_incr_int(&lockinfo.wcount);
224 atomic_decr_int(&lockinfo.rcount);
225 lockinfo.rlock_release(lockinfo.thelock);
231 atomic_decr_int(&lockinfo.wcount);
232 lockinfo.wlock_release(lockinfo.thelock);
236 * Main entry point for dynamic linking. The first argument is the
237 * stack pointer. The stack is expected to be laid out as described
238 * in the SVR4 ABI specification, Intel 386 Processor Supplement.
239 * Specifically, the stack pointer points to a word containing
240 * ARGC. Following that in the stack is a null-terminated sequence
241 * of pointers to argument strings. Then comes a null-terminated
242 * sequence of pointers to environment strings. Finally, there is a
243 * sequence of "auxiliary vector" entries.
245 * The second argument points to a place to store the dynamic linker's
246 * exit procedure pointer and the third to a place to store the main
249 * The return value is the main program's entry point.
252 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
254 Elf_Auxinfo *aux_info[AT_COUNT];
265 ld_index = 0; /* don't use old env cache in case we are resident */
268 * On entry, the dynamic linker itself has not been relocated yet.
269 * Be very careful not to reference any global data until after
270 * init_rtld has returned. It is OK to reference file-scope statics
271 * and string constants, and to call static and global functions.
274 /* Find the auxiliary vector on the stack. */
277 sp += argc + 1; /* Skip over arguments and NULL terminator */
281 * If we aren't already resident we have to dig out some more info.
282 * Note that auxinfo does not exist when we are resident.
284 if (ld_resident == 0) {
285 while (*sp++ != 0) /* Skip over environment, and NULL terminator */
287 aux = (Elf_Auxinfo *) sp;
289 /* Digest the auxiliary vector. */
290 for (i = 0; i < AT_COUNT; i++)
292 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
293 if (auxp->a_type < AT_COUNT)
294 aux_info[auxp->a_type] = auxp;
297 /* Initialize and relocate ourselves. */
298 assert(aux_info[AT_BASE] != NULL);
299 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
302 __progname = obj_rtld.path;
303 argv0 = argv[0] != NULL ? argv[0] : "(null)";
306 trust = (geteuid() == getuid()) && (getegid() == getgid());
308 ld_bind_now = _getenv_ld("LD_BIND_NOW");
310 ld_debug = _getenv_ld("LD_DEBUG");
311 ld_library_path = _getenv_ld("LD_LIBRARY_PATH");
312 ld_preload = (char *)_getenv_ld("LD_PRELOAD");
314 ld_tracing = _getenv_ld("LD_TRACE_LOADED_OBJECTS");
316 if (ld_debug != NULL && *ld_debug != '\0')
318 dbg("%s is initialized, base address = %p", __progname,
319 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
320 dbg("RTLD dynamic = %p", obj_rtld.dynamic);
321 dbg("RTLD pltgot = %p", obj_rtld.pltgot);
324 * If we are resident we can skip work that we have already done.
325 * Note that the stack is reset and there is no Elf_Auxinfo
326 * when running from a resident image, and the static globals setup
327 * between here and resident_skip will have already been setup.
333 * Load the main program, or process its program header if it is
336 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */
337 int fd = aux_info[AT_EXECFD]->a_un.a_val;
338 dbg("loading main program");
339 obj_main = map_object(fd, argv0, NULL);
341 if (obj_main == NULL)
343 } else { /* Main program already loaded. */
344 const Elf_Phdr *phdr;
348 dbg("processing main program's program header");
349 assert(aux_info[AT_PHDR] != NULL);
350 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr;
351 assert(aux_info[AT_PHNUM] != NULL);
352 phnum = aux_info[AT_PHNUM]->a_un.a_val;
353 assert(aux_info[AT_PHENT] != NULL);
354 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr));
355 assert(aux_info[AT_ENTRY] != NULL);
356 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr;
357 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL)
361 obj_main->path = xstrdup(argv0);
362 obj_main->mainprog = true;
365 * Get the actual dynamic linker pathname from the executable if
366 * possible. (It should always be possible.) That ensures that
367 * gdb will find the right dynamic linker even if a non-standard
370 if (obj_main->interp != NULL &&
371 strcmp(obj_main->interp, obj_rtld.path) != 0) {
373 obj_rtld.path = xstrdup(obj_main->interp);
376 digest_dynamic(obj_main);
378 linkmap_add(obj_main);
379 linkmap_add(&obj_rtld);
381 /* Link the main program into the list of objects. */
382 *obj_tail = obj_main;
383 obj_tail = &obj_main->next;
385 obj_main->refcount++;
386 /* Make sure we don't call the main program's init and fini functions. */
387 obj_main->init = obj_main->fini = NULL;
389 /* Initialize a fake symbol for resolving undefined weak references. */
390 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
391 sym_zero.st_shndx = SHN_ABS;
393 dbg("loading LD_PRELOAD libraries");
394 if (load_preload_objects() == -1)
396 preload_tail = obj_tail;
398 dbg("loading needed objects");
399 if (load_needed_objects(obj_main) == -1)
402 /* Make a list of all objects loaded at startup. */
403 for (obj = obj_list; obj != NULL; obj = obj->next)
404 objlist_push_tail(&list_main, obj);
408 if (ld_tracing) { /* We're done */
409 trace_loaded_objects(obj_main);
413 if (ld_resident) /* XXX clean this up! */
416 if (relocate_objects(obj_main,
417 ld_bind_now != NULL && *ld_bind_now != '\0') == -1)
420 dbg("doing copy relocations");
421 if (do_copy_relocations(obj_main) == -1)
426 if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) {
427 if (exec_sys_unregister(-1) < 0) {
428 dbg("exec_sys_unregister failed %d\n", errno);
431 dbg("exec_sys_unregister success\n");
435 dbg("initializing key program variables");
436 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : "");
437 set_program_var("environ", env);
439 if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) {
440 extern void resident_start(void);
442 if (exec_sys_register(resident_start) < 0) {
443 dbg("exec_sys_register failed %d\n", errno);
446 dbg("exec_sys_register success\n");
450 dbg("initializing thread locks");
451 lockdflt_init(&lockinfo);
452 lockinfo.thelock = lockinfo.lock_create(lockinfo.context);
454 /* Make a list of init functions to call. */
455 objlist_init(&initlist);
456 initlist_add_objects(obj_list, preload_tail, &initlist);
458 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */
460 objlist_call_init(&initlist);
462 objlist_clear(&initlist);
467 dbg("transferring control to program entry point = %p", obj_main->entry);
469 /* Return the exit procedure and the program entry point. */
470 *exit_proc = rtld_exit;
472 return (func_ptr_type) obj_main->entry;
476 _rtld_bind(Obj_Entry *obj, Elf_Word reloff)
480 const Obj_Entry *defobj;
486 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff);
488 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff);
490 where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
491 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
495 target = (Elf_Addr)(defobj->relocbase + def->st_value);
497 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"",
498 defobj->strtab + def->st_name, basename(obj->path),
499 (void *)target, basename(defobj->path));
501 reloc_jmpslot(where, target);
507 * Error reporting function. Use it like printf. If formats the message
508 * into a buffer, and sets things up so that the next call to dlerror()
509 * will return the message.
512 _rtld_error(const char *fmt, ...)
514 static char buf[512];
518 vsnprintf(buf, sizeof buf, fmt, ap);
524 * Return a dynamically-allocated copy of the current error message, if any.
529 return error_message == NULL ? NULL : xstrdup(error_message);
533 * Restore the current error message from a copy which was previously saved
534 * by errmsg_save(). The copy is freed.
537 errmsg_restore(char *saved_msg)
539 if (saved_msg == NULL)
540 error_message = NULL;
542 _rtld_error("%s", saved_msg);
548 basename(const char *name)
550 const char *p = strrchr(name, '/');
551 return p != NULL ? p + 1 : name;
557 const char *msg = dlerror();
565 * Process a shared object's DYNAMIC section, and save the important
566 * information in its Obj_Entry structure.
569 digest_dynamic(Obj_Entry *obj)
572 Needed_Entry **needed_tail = &obj->needed;
573 const Elf_Dyn *dyn_rpath = NULL;
574 int plttype = DT_REL;
576 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) {
577 switch (dynp->d_tag) {
580 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr);
584 obj->relsize = dynp->d_un.d_val;
588 assert(dynp->d_un.d_val == sizeof(Elf_Rel));
592 obj->pltrel = (const Elf_Rel *)
593 (obj->relocbase + dynp->d_un.d_ptr);
597 obj->pltrelsize = dynp->d_un.d_val;
601 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr);
605 obj->relasize = dynp->d_un.d_val;
609 assert(dynp->d_un.d_val == sizeof(Elf_Rela));
613 plttype = dynp->d_un.d_val;
614 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA);
618 obj->symtab = (const Elf_Sym *)
619 (obj->relocbase + dynp->d_un.d_ptr);
623 assert(dynp->d_un.d_val == sizeof(Elf_Sym));
627 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr);
631 obj->strsize = dynp->d_un.d_val;
636 const Elf_Addr *hashtab = (const Elf_Addr *)
637 (obj->relocbase + dynp->d_un.d_ptr);
638 obj->nbuckets = hashtab[0];
639 obj->nchains = hashtab[1];
640 obj->buckets = hashtab + 2;
641 obj->chains = obj->buckets + obj->nbuckets;
647 Needed_Entry *nep = NEW(Needed_Entry);
648 nep->name = dynp->d_un.d_val;
653 needed_tail = &nep->next;
658 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr);
666 obj->symbolic = true;
671 * We have to wait until later to process this, because we
672 * might not have gotten the address of the string table yet.
678 /* Not used by the dynamic linker. */
682 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
686 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
690 /* XXX - not implemented yet */
691 dbg("Filling in DT_DEBUG entry");
692 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug;
696 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag);
703 if (plttype == DT_RELA) {
704 obj->pltrela = (const Elf_Rela *) obj->pltrel;
706 obj->pltrelasize = obj->pltrelsize;
710 if (dyn_rpath != NULL)
711 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val;
715 * Process a shared object's program header. This is used only for the
716 * main program, when the kernel has already loaded the main program
717 * into memory before calling the dynamic linker. It creates and
718 * returns an Obj_Entry structure.
721 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
724 const Elf_Phdr *phlimit = phdr + phnum;
729 for (ph = phdr; ph < phlimit; ph++) {
730 switch (ph->p_type) {
733 if ((const Elf_Phdr *)ph->p_vaddr != phdr) {
734 _rtld_error("%s: invalid PT_PHDR", path);
737 obj->phdr = (const Elf_Phdr *) ph->p_vaddr;
738 obj->phsize = ph->p_memsz;
742 obj->interp = (const char *) ph->p_vaddr;
746 if (nsegs == 0) { /* First load segment */
747 obj->vaddrbase = trunc_page(ph->p_vaddr);
748 obj->mapbase = (caddr_t) obj->vaddrbase;
749 obj->relocbase = obj->mapbase - obj->vaddrbase;
750 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
752 } else { /* Last load segment */
753 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) -
760 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr;
765 _rtld_error("%s: too few PT_LOAD segments", path);
774 dlcheck(void *handle)
778 for (obj = obj_list; obj != NULL; obj = obj->next)
779 if (obj == (Obj_Entry *) handle)
782 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) {
783 _rtld_error("Invalid shared object handle %p", handle);
790 * If the given object is already in the donelist, return true. Otherwise
791 * add the object to the list and return false.
794 donelist_check(DoneList *dlp, const Obj_Entry *obj)
798 for (i = 0; i < dlp->num_used; i++)
799 if (dlp->objs[i] == obj)
802 * Our donelist allocation should always be sufficient. But if
803 * our threads locking isn't working properly, more shared objects
804 * could have been loaded since we allocated the list. That should
805 * never happen, but we'll handle it properly just in case it does.
807 if (dlp->num_used < dlp->num_alloc)
808 dlp->objs[dlp->num_used++] = obj;
813 * Hash function for symbol table lookup. Don't even think about changing
814 * this. It is specified by the System V ABI.
817 elf_hash(const char *name)
819 const unsigned char *p = (const unsigned char *) name;
825 if ((g = h & 0xf0000000) != 0)
833 * Find the library with the given name, and return its full pathname.
834 * The returned string is dynamically allocated. Generates an error
835 * message and returns NULL if the library cannot be found.
837 * If the second argument is non-NULL, then it refers to an already-
838 * loaded shared object, whose library search path will be searched.
840 * The search order is:
842 * rpath in the referencing file
847 find_library(const char *name, const Obj_Entry *refobj)
851 if (strchr(name, '/') != NULL) { /* Hard coded pathname */
852 if (name[0] != '/' && !trust) {
853 _rtld_error("Absolute pathname required for shared object \"%s\"",
857 return xstrdup(name);
860 dbg(" Searching for \"%s\"", name);
862 if ((pathname = search_library_path(name, ld_library_path)) != NULL ||
864 (pathname = search_library_path(name, refobj->rpath)) != NULL) ||
865 (pathname = search_library_path(name, gethints())) != NULL ||
866 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL)
869 _rtld_error("Shared object \"%s\" not found", name);
874 * Given a symbol number in a referencing object, find the corresponding
875 * definition of the symbol. Returns a pointer to the symbol, or NULL if
876 * no definition was found. Returns a pointer to the Obj_Entry of the
877 * defining object via the reference parameter DEFOBJ_OUT.
880 find_symdef(unsigned long symnum, const Obj_Entry *refobj,
881 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache)
885 const Obj_Entry *defobj;
890 * If we have already found this symbol, get the information from
893 if (symnum >= refobj->nchains)
894 return NULL; /* Bad object */
895 if (cache != NULL && cache[symnum].sym != NULL) {
896 *defobj_out = cache[symnum].obj;
897 return cache[symnum].sym;
900 ref = refobj->symtab + symnum;
901 name = refobj->strtab + ref->st_name;
902 hash = elf_hash(name);
905 def = symlook_default(name, hash, refobj, &defobj, in_plt);
908 * If we found no definition and the reference is weak, treat the
909 * symbol as having the value zero.
911 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) {
917 *defobj_out = defobj;
918 /* Record the information in the cache to avoid subsequent lookups. */
920 cache[symnum].sym = def;
921 cache[symnum].obj = defobj;
924 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
929 * Return the search path from the ldconfig hints file, reading it if
930 * necessary. Returns NULL if there are problems with the hints file,
931 * or if the search path there is empty.
940 struct elfhints_hdr hdr;
943 /* Keep from trying again in case the hints file is bad. */
946 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1)
948 if (read(fd, &hdr, sizeof hdr) != sizeof hdr ||
949 hdr.magic != ELFHINTS_MAGIC ||
954 p = xmalloc(hdr.dirlistlen + 1);
955 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 ||
956 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) {
964 return hints[0] != '\0' ? hints : NULL;
968 init_dag(Obj_Entry *root)
972 donelist_init(&donelist);
973 init_dag1(root, root, &donelist);
977 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp)
979 const Needed_Entry *needed;
981 if (donelist_check(dlp, obj))
983 objlist_push_tail(&obj->dldags, root);
984 objlist_push_tail(&root->dagmembers, obj);
985 for (needed = obj->needed; needed != NULL; needed = needed->next)
986 if (needed->obj != NULL)
987 init_dag1(root, needed->obj, dlp);
991 * Initialize the dynamic linker. The argument is the address at which
992 * the dynamic linker has been mapped into memory. The primary task of
993 * this function is to relocate the dynamic linker.
996 init_rtld(caddr_t mapbase)
999 * Conjure up an Obj_Entry structure for the dynamic linker.
1001 * The "path" member is supposed to be dynamically-allocated, but we
1002 * aren't yet initialized sufficiently to do that. Below we will
1003 * replace the static version with a dynamically-allocated copy.
1005 obj_rtld.path = PATH_RTLD;
1006 obj_rtld.rtld = true;
1007 obj_rtld.mapbase = mapbase;
1009 obj_rtld.relocbase = mapbase;
1011 if (&_DYNAMIC != 0) {
1012 obj_rtld.dynamic = rtld_dynamic(&obj_rtld);
1013 digest_dynamic(&obj_rtld);
1014 assert(obj_rtld.needed == NULL);
1015 assert(!obj_rtld.textrel);
1018 * Temporarily put the dynamic linker entry into the object list, so
1019 * that symbols can be found.
1021 obj_list = &obj_rtld;
1022 obj_tail = &obj_rtld.next;
1025 relocate_objects(&obj_rtld, true);
1028 /* Make the object list empty again. */
1030 obj_tail = &obj_list;
1033 /* Replace the path with a dynamically allocated copy. */
1034 obj_rtld.path = xstrdup(obj_rtld.path);
1036 r_debug.r_brk = r_debug_state;
1037 r_debug.r_state = RT_CONSISTENT;
1041 * Add the init functions from a needed object list (and its recursive
1042 * needed objects) to "list". This is not used directly; it is a helper
1043 * function for initlist_add_objects(). The write lock must be held
1044 * when this function is called.
1047 initlist_add_neededs(Needed_Entry *needed, Objlist *list)
1049 /* Recursively process the successor needed objects. */
1050 if (needed->next != NULL)
1051 initlist_add_neededs(needed->next, list);
1053 /* Process the current needed object. */
1054 if (needed->obj != NULL)
1055 initlist_add_objects(needed->obj, &needed->obj->next, list);
1059 * Scan all of the DAGs rooted in the range of objects from "obj" to
1060 * "tail" and add their init functions to "list". This recurses over
1061 * the DAGs and ensure the proper init ordering such that each object's
1062 * needed libraries are initialized before the object itself. At the
1063 * same time, this function adds the objects to the global finalization
1064 * list "list_fini" in the opposite order. The write lock must be
1065 * held when this function is called.
1068 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list)
1072 obj->init_done = true;
1074 /* Recursively process the successor objects. */
1075 if (&obj->next != tail)
1076 initlist_add_objects(obj->next, tail, list);
1078 /* Recursively process the needed objects. */
1079 if (obj->needed != NULL)
1080 initlist_add_neededs(obj->needed, list);
1082 /* Add the object to the init list. */
1083 if (obj->init != NULL)
1084 objlist_push_tail(list, obj);
1086 /* Add the object to the global fini list in the reverse order. */
1087 if (obj->fini != NULL)
1088 objlist_push_head(&list_fini, obj);
1092 is_exported(const Elf_Sym *def)
1094 func_ptr_type value;
1095 const func_ptr_type *p;
1097 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value);
1098 for (p = exports; *p != NULL; p++)
1105 * Given a shared object, traverse its list of needed objects, and load
1106 * each of them. Returns 0 on success. Generates an error message and
1107 * returns -1 on failure.
1110 load_needed_objects(Obj_Entry *first)
1114 for (obj = first; obj != NULL; obj = obj->next) {
1115 Needed_Entry *needed;
1117 for (needed = obj->needed; needed != NULL; needed = needed->next) {
1118 const char *name = obj->strtab + needed->name;
1119 char *path = find_library(name, obj);
1122 if (path == NULL && !ld_tracing)
1126 needed->obj = load_object(path);
1127 if (needed->obj == NULL && !ld_tracing)
1128 return -1; /* XXX - cleanup */
1137 load_preload_objects(void)
1139 char *p = ld_preload;
1140 static const char delim[] = " \t:;";
1145 p += strspn(p, delim);
1146 while (*p != '\0') {
1147 size_t len = strcspn(p, delim);
1153 if ((path = find_library(p, NULL)) == NULL)
1155 if (load_object(path) == NULL)
1156 return -1; /* XXX - cleanup */
1159 p += strspn(p, delim);
1165 * Load a shared object into memory, if it is not already loaded. The
1166 * argument must be a string allocated on the heap. This function assumes
1167 * responsibility for freeing it when necessary.
1169 * Returns a pointer to the Obj_Entry for the object. Returns NULL
1173 load_object(char *path)
1179 for (obj = obj_list->next; obj != NULL; obj = obj->next)
1180 if (strcmp(obj->path, path) == 0)
1184 * If we didn't find a match by pathname, open the file and check
1185 * again by device and inode. This avoids false mismatches caused
1186 * by multiple links or ".." in pathnames.
1188 * To avoid a race, we open the file and use fstat() rather than
1192 if ((fd = open(path, O_RDONLY)) == -1) {
1193 _rtld_error("Cannot open \"%s\"", path);
1196 if (fstat(fd, &sb) == -1) {
1197 _rtld_error("Cannot fstat \"%s\"", path);
1201 for (obj = obj_list->next; obj != NULL; obj = obj->next) {
1202 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) {
1209 if (obj == NULL) { /* First use of this object, so we must map it in */
1210 dbg("loading \"%s\"", path);
1211 obj = map_object(fd, path, &sb);
1219 digest_dynamic(obj);
1222 obj_tail = &obj->next;
1224 linkmap_add(obj); /* for GDB & dlinfo() */
1226 dbg(" %p .. %p: %s", obj->mapbase,
1227 obj->mapbase + obj->mapsize - 1, obj->path);
1229 dbg(" WARNING: %s has impure text", obj->path);
1238 * Check for locking violations and die if one is found.
1245 rcount = lockinfo.rcount;
1246 wcount = lockinfo.wcount;
1247 assert(rcount >= 0);
1248 assert(wcount >= 0);
1249 if (wcount > 1 || (wcount != 0 && rcount != 0)) {
1250 _rtld_error("Application locking error: %d readers and %d writers"
1251 " in dynamic linker. See DLLOCKINIT(3) in manual pages.",
1258 obj_from_addr(const void *addr)
1260 unsigned long endhash;
1263 endhash = elf_hash(END_SYM);
1264 for (obj = obj_list; obj != NULL; obj = obj->next) {
1265 const Elf_Sym *endsym;
1267 if (addr < (void *) obj->mapbase)
1269 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL)
1270 continue; /* No "end" symbol?! */
1271 if (addr < (void *) (obj->relocbase + endsym->st_value))
1278 * Call the finalization functions for each of the objects in "list"
1279 * which are unreferenced. All of the objects are expected to have
1280 * non-NULL fini functions.
1283 objlist_call_fini(Objlist *list)
1289 * Preserve the current error message since a fini function might
1290 * call into the dynamic linker and overwrite it.
1292 saved_msg = errmsg_save();
1293 STAILQ_FOREACH(elm, list, link) {
1294 if (elm->obj->refcount == 0) {
1295 dbg("calling fini function for %s", elm->obj->path);
1296 (*elm->obj->fini)();
1299 errmsg_restore(saved_msg);
1303 * Call the initialization functions for each of the objects in
1304 * "list". All of the objects are expected to have non-NULL init
1308 objlist_call_init(Objlist *list)
1314 * Preserve the current error message since an init function might
1315 * call into the dynamic linker and overwrite it.
1317 saved_msg = errmsg_save();
1318 STAILQ_FOREACH(elm, list, link) {
1319 dbg("calling init function for %s", elm->obj->path);
1320 (*elm->obj->init)();
1322 errmsg_restore(saved_msg);
1326 objlist_clear(Objlist *list)
1330 while (!STAILQ_EMPTY(list)) {
1331 elm = STAILQ_FIRST(list);
1332 STAILQ_REMOVE_HEAD(list, link);
1337 static Objlist_Entry *
1338 objlist_find(Objlist *list, const Obj_Entry *obj)
1342 STAILQ_FOREACH(elm, list, link)
1343 if (elm->obj == obj)
1349 objlist_init(Objlist *list)
1355 objlist_push_head(Objlist *list, Obj_Entry *obj)
1359 elm = NEW(Objlist_Entry);
1361 STAILQ_INSERT_HEAD(list, elm, link);
1365 objlist_push_tail(Objlist *list, Obj_Entry *obj)
1369 elm = NEW(Objlist_Entry);
1371 STAILQ_INSERT_TAIL(list, elm, link);
1375 objlist_remove(Objlist *list, Obj_Entry *obj)
1379 if ((elm = objlist_find(list, obj)) != NULL) {
1380 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link);
1386 * Remove all of the unreferenced objects from "list".
1389 objlist_remove_unref(Objlist *list)
1394 STAILQ_INIT(&newlist);
1395 while (!STAILQ_EMPTY(list)) {
1396 elm = STAILQ_FIRST(list);
1397 STAILQ_REMOVE_HEAD(list, link);
1398 if (elm->obj->refcount == 0)
1401 STAILQ_INSERT_TAIL(&newlist, elm, link);
1407 * Relocate newly-loaded shared objects. The argument is a pointer to
1408 * the Obj_Entry for the first such object. All objects from the first
1409 * to the end of the list of objects are relocated. Returns 0 on success,
1413 relocate_objects(Obj_Entry *first, bool bind_now)
1417 for (obj = first; obj != NULL; obj = obj->next) {
1418 if (obj != &obj_rtld)
1419 dbg("relocating \"%s\"", obj->path);
1420 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL ||
1421 obj->symtab == NULL || obj->strtab == NULL) {
1422 _rtld_error("%s: Shared object has no run-time symbol table",
1428 /* There are relocations to the write-protected text segment. */
1429 if (mprotect(obj->mapbase, obj->textsize,
1430 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
1431 _rtld_error("%s: Cannot write-enable text segment: %s",
1432 obj->path, strerror(errno));
1437 /* Process the non-PLT relocations. */
1438 if (reloc_non_plt(obj, &obj_rtld))
1441 if (obj->textrel) { /* Re-protected the text segment. */
1442 if (mprotect(obj->mapbase, obj->textsize,
1443 PROT_READ|PROT_EXEC) == -1) {
1444 _rtld_error("%s: Cannot write-protect text segment: %s",
1445 obj->path, strerror(errno));
1450 /* Process the PLT relocations. */
1451 if (reloc_plt(obj) == -1)
1453 /* Relocate the jump slots if we are doing immediate binding. */
1455 if (reloc_jmpslots(obj) == -1)
1460 * Set up the magic number and version in the Obj_Entry. These
1461 * were checked in the crt1.o from the original ElfKit, so we
1462 * set them for backward compatibility.
1464 obj->magic = RTLD_MAGIC;
1465 obj->version = RTLD_VERSION;
1467 /* Set the special PLT or GOT entries. */
1475 * Cleanup procedure. It will be called (by the atexit mechanism) just
1476 * before the process exits.
1484 /* Clear all the reference counts so the fini functions will be called. */
1485 for (obj = obj_list; obj != NULL; obj = obj->next)
1487 objlist_call_fini(&list_fini);
1488 /* No need to remove the items from the list, since we are exiting. */
1492 path_enumerate(const char *path, path_enum_proc callback, void *arg)
1497 path += strspn(path, ":;");
1498 while (*path != '\0') {
1502 len = strcspn(path, ":;");
1503 res = callback(path, len, arg);
1509 path += strspn(path, ":;");
1515 struct try_library_args {
1523 try_library_path(const char *dir, size_t dirlen, void *param)
1525 struct try_library_args *arg;
1528 if (*dir == '/' || trust) {
1531 if (dirlen + 1 + arg->namelen + 1 > arg->buflen)
1534 pathname = arg->buffer;
1535 strncpy(pathname, dir, dirlen);
1536 pathname[dirlen] = '/';
1537 strcpy(pathname + dirlen + 1, arg->name);
1539 dbg(" Trying \"%s\"", pathname);
1540 if (access(pathname, F_OK) == 0) { /* We found it */
1541 pathname = xmalloc(dirlen + 1 + arg->namelen + 1);
1542 strcpy(pathname, arg->buffer);
1550 search_library_path(const char *name, const char *path)
1553 struct try_library_args arg;
1559 arg.namelen = strlen(name);
1560 arg.buffer = xmalloc(PATH_MAX);
1561 arg.buflen = PATH_MAX;
1563 p = path_enumerate(path, try_library_path, &arg);
1571 dlclose(void *handle)
1576 root = dlcheck(handle);
1582 /* Unreference the object and its dependencies. */
1583 root->dl_refcount--;
1586 if (root->refcount == 0) {
1588 * The object is no longer referenced, so we must unload it.
1589 * First, call the fini functions with no locks held.
1592 objlist_call_fini(&list_fini);
1594 objlist_remove_unref(&list_fini);
1596 /* Finish cleaning up the newly-unreferenced objects. */
1597 GDB_STATE(RT_DELETE,&root->linkmap);
1598 unload_object(root);
1599 GDB_STATE(RT_CONSISTENT,NULL);
1608 char *msg = error_message;
1609 error_message = NULL;
1614 * This function is deprecated and has no effect.
1617 dllockinit(void *context,
1618 void *(*lock_create)(void *context),
1619 void (*rlock_acquire)(void *lock),
1620 void (*wlock_acquire)(void *lock),
1621 void (*lock_release)(void *lock),
1622 void (*lock_destroy)(void *lock),
1623 void (*context_destroy)(void *context))
1625 static void *cur_context;
1626 static void (*cur_context_destroy)(void *);
1628 /* Just destroy the context from the previous call, if necessary. */
1629 if (cur_context_destroy != NULL)
1630 cur_context_destroy(cur_context);
1631 cur_context = context;
1632 cur_context_destroy = context_destroy;
1636 dlopen(const char *name, int mode)
1638 Obj_Entry **old_obj_tail;
1643 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1";
1644 if (ld_tracing != NULL)
1645 environ = (char **)*get_program_var_addr("environ");
1647 objlist_init(&initlist);
1650 GDB_STATE(RT_ADD,NULL);
1652 old_obj_tail = obj_tail;
1658 char *path = find_library(name, obj_main);
1660 obj = load_object(path);
1665 if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL)
1666 objlist_push_tail(&list_global, obj);
1667 mode &= RTLD_MODEMASK;
1668 if (*old_obj_tail != NULL) { /* We loaded something new. */
1669 assert(*old_obj_tail == obj);
1671 result = load_needed_objects(obj);
1672 if (result != -1 && ld_tracing)
1676 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) {
1679 if (obj->refcount == 0)
1683 /* Make list of init functions to call. */
1684 initlist_add_objects(obj, &obj->next, &initlist);
1686 } else if (ld_tracing)
1690 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL);
1692 /* Call the init functions with no locks held. */
1694 objlist_call_init(&initlist);
1696 objlist_clear(&initlist);
1700 trace_loaded_objects(obj);
1706 dlsym(void *handle, const char *name)
1708 const Obj_Entry *obj;
1711 const Obj_Entry *defobj;
1713 hash = elf_hash(name);
1718 if (handle == NULL || handle == RTLD_NEXT ||
1719 handle == RTLD_DEFAULT || handle == RTLD_SELF) {
1722 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1723 if ((obj = obj_from_addr(retaddr)) == NULL) {
1724 _rtld_error("Cannot determine caller's shared object");
1728 if (handle == NULL) { /* Just the caller's shared object. */
1729 def = symlook_obj(name, hash, obj, true);
1731 } else if (handle == RTLD_NEXT || /* Objects after caller's */
1732 handle == RTLD_SELF) { /* ... caller included */
1733 if (handle == RTLD_NEXT)
1735 for (; obj != NULL; obj = obj->next) {
1736 if ((def = symlook_obj(name, hash, obj, true)) != NULL) {
1742 assert(handle == RTLD_DEFAULT);
1743 def = symlook_default(name, hash, obj, &defobj, true);
1746 if ((obj = dlcheck(handle)) == NULL) {
1751 if (obj->mainprog) {
1754 /* Search main program and all libraries loaded by it. */
1755 donelist_init(&donelist);
1756 def = symlook_list(name, hash, &list_main, &defobj, true,
1760 * XXX - This isn't correct. The search should include the whole
1761 * DAG rooted at the given object.
1763 def = symlook_obj(name, hash, obj, true);
1770 return defobj->relocbase + def->st_value;
1773 _rtld_error("Undefined symbol \"%s\"", name);
1779 dladdr(const void *addr, Dl_info *info)
1781 const Obj_Entry *obj;
1784 unsigned long symoffset;
1787 obj = obj_from_addr(addr);
1789 _rtld_error("No shared object contains address");
1793 info->dli_fname = obj->path;
1794 info->dli_fbase = obj->mapbase;
1795 info->dli_saddr = (void *)0;
1796 info->dli_sname = NULL;
1799 * Walk the symbol list looking for the symbol whose address is
1800 * closest to the address sent in.
1802 for (symoffset = 0; symoffset < obj->nchains; symoffset++) {
1803 def = obj->symtab + symoffset;
1806 * For skip the symbol if st_shndx is either SHN_UNDEF or
1809 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON)
1813 * If the symbol is greater than the specified address, or if it
1814 * is further away from addr than the current nearest symbol,
1817 symbol_addr = obj->relocbase + def->st_value;
1818 if (symbol_addr > addr || symbol_addr < info->dli_saddr)
1821 /* Update our idea of the nearest symbol. */
1822 info->dli_sname = obj->strtab + def->st_name;
1823 info->dli_saddr = symbol_addr;
1826 if (info->dli_saddr == addr)
1834 dlinfo(void *handle, int request, void *p)
1836 const Obj_Entry *obj;
1841 if (handle == NULL || handle == RTLD_SELF) {
1844 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1845 if ((obj = obj_from_addr(retaddr)) == NULL)
1846 _rtld_error("Cannot determine caller's shared object");
1848 obj = dlcheck(handle);
1857 case RTLD_DI_LINKMAP:
1858 *((struct link_map const **)p) = &obj->linkmap;
1860 case RTLD_DI_ORIGIN:
1861 error = rtld_dirname(obj->path, p);
1864 case RTLD_DI_SERINFOSIZE:
1865 case RTLD_DI_SERINFO:
1866 error = do_search_info(obj, request, (struct dl_serinfo *)p);
1870 _rtld_error("Invalid request %d passed to dlinfo()", request);
1879 struct fill_search_info_args {
1882 Dl_serinfo *serinfo;
1883 Dl_serpath *serpath;
1888 fill_search_info(const char *dir, size_t dirlen, void *param)
1890 struct fill_search_info_args *arg;
1894 if (arg->request == RTLD_DI_SERINFOSIZE) {
1895 arg->serinfo->dls_cnt ++;
1896 arg->serinfo->dls_size += dirlen + 1;
1898 struct dl_serpath *s_entry;
1900 s_entry = arg->serpath;
1901 s_entry->dls_name = arg->strspace;
1902 s_entry->dls_flags = arg->flags;
1904 strncpy(arg->strspace, dir, dirlen);
1905 arg->strspace[dirlen] = '\0';
1907 arg->strspace += dirlen + 1;
1915 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info)
1917 struct dl_serinfo _info;
1918 struct fill_search_info_args args;
1920 args.request = RTLD_DI_SERINFOSIZE;
1921 args.serinfo = &_info;
1923 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath);
1926 path_enumerate(ld_library_path, fill_search_info, &args);
1927 path_enumerate(obj->rpath, fill_search_info, &args);
1928 path_enumerate(gethints(), fill_search_info, &args);
1929 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args);
1932 if (request == RTLD_DI_SERINFOSIZE) {
1933 info->dls_size = _info.dls_size;
1934 info->dls_cnt = _info.dls_cnt;
1938 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) {
1939 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()");
1943 args.request = RTLD_DI_SERINFO;
1944 args.serinfo = info;
1945 args.serpath = &info->dls_serpath[0];
1946 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt];
1948 args.flags = LA_SER_LIBPATH;
1949 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL)
1952 args.flags = LA_SER_RUNPATH;
1953 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL)
1956 args.flags = LA_SER_CONFIG;
1957 if (path_enumerate(gethints(), fill_search_info, &args) != NULL)
1960 args.flags = LA_SER_DEFAULT;
1961 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL)
1967 rtld_dirname(const char *path, char *bname)
1971 /* Empty or NULL string gets treated as "." */
1972 if (path == NULL || *path == '\0') {
1978 /* Strip trailing slashes */
1979 endp = path + strlen(path) - 1;
1980 while (endp > path && *endp == '/')
1983 /* Find the start of the dir */
1984 while (endp > path && *endp != '/')
1987 /* Either the dir is "/" or there are no slashes */
1989 bname[0] = *endp == '/' ? '/' : '.';
1995 } while (endp > path && *endp == '/');
1998 if (endp - path + 2 > PATH_MAX)
2000 _rtld_error("Filename is too long: %s", path);
2004 strncpy(bname, path, endp - path + 1);
2005 bname[endp - path + 1] = '\0';
2010 linkmap_add(Obj_Entry *obj)
2012 struct link_map *l = &obj->linkmap;
2013 struct link_map *prev;
2015 obj->linkmap.l_name = obj->path;
2016 obj->linkmap.l_addr = obj->mapbase;
2017 obj->linkmap.l_ld = obj->dynamic;
2019 /* GDB needs load offset on MIPS to use the symbols */
2020 obj->linkmap.l_offs = obj->relocbase;
2023 if (r_debug.r_map == NULL) {
2029 * Scan to the end of the list, but not past the entry for the
2030 * dynamic linker, which we want to keep at the very end.
2032 for (prev = r_debug.r_map;
2033 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap;
2034 prev = prev->l_next)
2037 /* Link in the new entry. */
2039 l->l_next = prev->l_next;
2040 if (l->l_next != NULL)
2041 l->l_next->l_prev = l;
2046 linkmap_delete(Obj_Entry *obj)
2048 struct link_map *l = &obj->linkmap;
2050 if (l->l_prev == NULL) {
2051 if ((r_debug.r_map = l->l_next) != NULL)
2052 l->l_next->l_prev = NULL;
2056 if ((l->l_prev->l_next = l->l_next) != NULL)
2057 l->l_next->l_prev = l->l_prev;
2061 * Function for the debugger to set a breakpoint on to gain control.
2063 * The two parameters allow the debugger to easily find and determine
2064 * what the runtime loader is doing and to whom it is doing it.
2066 * When the loadhook trap is hit (r_debug_state, set at program
2067 * initialization), the arguments can be found on the stack:
2069 * +8 struct link_map *m
2070 * +4 struct r_debug *rd
2074 r_debug_state(struct r_debug* rd, struct link_map *m)
2079 * Get address of the pointer variable in the main program.
2081 static const void **
2082 get_program_var_addr(const char *name)
2084 const Obj_Entry *obj;
2087 hash = elf_hash(name);
2088 for (obj = obj_main; obj != NULL; obj = obj->next) {
2091 if ((def = symlook_obj(name, hash, obj, false)) != NULL) {
2094 addr = (const void **)(obj->relocbase + def->st_value);
2102 * Set a pointer variable in the main program to the given value. This
2103 * is used to set key variables such as "environ" before any of the
2104 * init functions are called.
2107 set_program_var(const char *name, const void *value)
2111 if ((addr = get_program_var_addr(name)) != NULL) {
2112 dbg("\"%s\": *%p <-- %p", name, addr, value);
2118 * This is a special version of getenv which is far more efficient
2119 * at finding LD_ environment vars.
2123 _getenv_ld(const char *id)
2127 int idlen = strlen(id);
2129 if (ld_index == LD_ARY_CACHE)
2131 if (ld_index == 0) {
2132 for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) {
2133 if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_')
2140 for (i = ld_index - 1; i >= 0; --i) {
2141 if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=')
2142 return(ld_ary[i] + idlen + 1);
2148 * Given a symbol name in a referencing object, find the corresponding
2149 * definition of the symbol. Returns a pointer to the symbol, or NULL if
2150 * no definition was found. Returns a pointer to the Obj_Entry of the
2151 * defining object via the reference parameter DEFOBJ_OUT.
2153 static const Elf_Sym *
2154 symlook_default(const char *name, unsigned long hash,
2155 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt)
2159 const Elf_Sym *symp;
2160 const Obj_Entry *obj;
2161 const Obj_Entry *defobj;
2162 const Objlist_Entry *elm;
2165 donelist_init(&donelist);
2167 /* Look first in the referencing object if linked symbolically. */
2168 if (refobj->symbolic && !donelist_check(&donelist, refobj)) {
2169 symp = symlook_obj(name, hash, refobj, in_plt);
2176 /* Search all objects loaded at program start up. */
2177 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2178 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist);
2180 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2186 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */
2187 STAILQ_FOREACH(elm, &list_global, link) {
2188 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2190 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2193 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2199 /* Search all dlopened DAGs containing the referencing object. */
2200 STAILQ_FOREACH(elm, &refobj->dldags, link) {
2201 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2203 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2206 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2213 * Search the dynamic linker itself, and possibly resolve the
2214 * symbol from there. This is how the application links to
2215 * dynamic linker services such as dlopen. Only the values listed
2216 * in the "exports" array can be resolved from the dynamic linker.
2218 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2219 symp = symlook_obj(name, hash, &obj_rtld, in_plt);
2220 if (symp != NULL && is_exported(symp)) {
2227 *defobj_out = defobj;
2231 static const Elf_Sym *
2232 symlook_list(const char *name, unsigned long hash, Objlist *objlist,
2233 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)
2235 const Elf_Sym *symp;
2237 const Obj_Entry *defobj;
2238 const Objlist_Entry *elm;
2242 STAILQ_FOREACH(elm, objlist, link) {
2243 if (donelist_check(dlp, elm->obj))
2245 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) {
2246 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) {
2249 if (ELF_ST_BIND(def->st_info) != STB_WEAK)
2255 *defobj_out = defobj;
2260 * Search the symbol table of a single shared object for a symbol of
2261 * the given name. Returns a pointer to the symbol, or NULL if no
2262 * definition was found.
2264 * The symbol's hash value is passed in for efficiency reasons; that
2265 * eliminates many recomputations of the hash value.
2268 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj,
2271 if (obj->buckets != NULL) {
2272 unsigned long symnum = obj->buckets[hash % obj->nbuckets];
2274 while (symnum != STN_UNDEF) {
2275 const Elf_Sym *symp;
2278 if (symnum >= obj->nchains)
2279 return NULL; /* Bad object */
2280 symp = obj->symtab + symnum;
2281 strp = obj->strtab + symp->st_name;
2283 if (name[0] == strp[0] && strcmp(name, strp) == 0)
2284 return symp->st_shndx != SHN_UNDEF ||
2285 (!in_plt && symp->st_value != 0 &&
2286 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL;
2288 symnum = obj->chains[symnum];
2295 trace_loaded_objects(Obj_Entry *obj)
2297 const char *fmt1, *fmt2, *fmt, *main_local;
2300 if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL)
2303 if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL)
2304 fmt1 = "\t%o => %p (%x)\n";
2306 if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL)
2307 fmt2 = "\t%o (%x)\n";
2309 for (; obj; obj = obj->next) {
2310 Needed_Entry *needed;
2314 for (needed = obj->needed; needed; needed = needed->next) {
2315 if (needed->obj != NULL) {
2316 if (needed->obj->traced)
2318 needed->obj->traced = true;
2319 path = needed->obj->path;
2323 name = (char *)obj->strtab + needed->name;
2324 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */
2326 fmt = is_lib ? fmt1 : fmt2;
2327 while ((c = *fmt++) != '\0') {
2353 printf("%s", main_local);
2356 printf("%s", obj_main->path);
2363 printf("%d", sodp->sod_major);
2366 printf("%d", sodp->sod_minor);
2373 printf("%p", needed->obj ? needed->obj->mapbase : 0);
2385 * Unload a dlopened object and its dependencies from memory and from
2386 * our data structures. It is assumed that the DAG rooted in the
2387 * object has already been unreferenced, and that the object has a
2388 * reference count of 0.
2391 unload_object(Obj_Entry *root)
2396 assert(root->refcount == 0);
2399 * Pass over the DAG removing unreferenced objects from
2400 * appropriate lists.
2402 unlink_object(root);
2404 /* Unmap all objects that are no longer referenced. */
2405 linkp = &obj_list->next;
2406 while ((obj = *linkp) != NULL) {
2407 if (obj->refcount == 0) {
2408 dbg("unloading \"%s\"", obj->path);
2409 munmap(obj->mapbase, obj->mapsize);
2410 linkmap_delete(obj);
2421 unlink_object(Obj_Entry *root)
2423 const Needed_Entry *needed;
2426 if (root->refcount == 0) {
2427 /* Remove the object from the RTLD_GLOBAL list. */
2428 objlist_remove(&list_global, root);
2430 /* Remove the object from all objects' DAG lists. */
2431 STAILQ_FOREACH(elm, &root->dagmembers , link)
2432 objlist_remove(&elm->obj->dldags, root);
2435 for (needed = root->needed; needed != NULL; needed = needed->next)
2436 if (needed->obj != NULL)
2437 unlink_object(needed->obj);
2441 unref_dag(Obj_Entry *root)
2443 const Needed_Entry *needed;
2445 if (root->refcount == 0)
2448 if (root->refcount == 0)
2449 for (needed = root->needed; needed != NULL; needed = needed->next)
2450 if (needed->obj != NULL)
2451 unref_dag(needed->obj);