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 1.10 2005/02/04 01:06:05 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 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 (getenv("LD_DUMP_REL_PRE") != NULL) {
417 dump_relocations(obj_main);
421 if (relocate_objects(obj_main,
422 ld_bind_now != NULL && *ld_bind_now != '\0') == -1)
425 dbg("doing copy relocations");
426 if (do_copy_relocations(obj_main) == -1)
431 if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) {
432 if (exec_sys_unregister(-1) < 0) {
433 dbg("exec_sys_unregister failed %d\n", errno);
436 dbg("exec_sys_unregister success\n");
440 if (getenv("LD_DUMP_REL_POST") != NULL) {
441 dump_relocations(obj_main);
445 dbg("initializing key program variables");
446 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : "");
447 set_program_var("environ", env);
449 if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) {
450 extern void resident_start(void);
452 if (exec_sys_register(resident_start) < 0) {
453 dbg("exec_sys_register failed %d\n", errno);
456 dbg("exec_sys_register success\n");
460 dbg("initializing thread locks");
461 lockdflt_init(&lockinfo);
462 lockinfo.thelock = lockinfo.lock_create(lockinfo.context);
464 /* Make a list of init functions to call. */
465 objlist_init(&initlist);
466 initlist_add_objects(obj_list, preload_tail, &initlist);
468 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */
470 objlist_call_init(&initlist);
472 objlist_clear(&initlist);
477 dbg("transferring control to program entry point = %p", obj_main->entry);
479 /* Return the exit procedure and the program entry point. */
480 *exit_proc = rtld_exit;
482 return (func_ptr_type) obj_main->entry;
486 _rtld_bind(Obj_Entry *obj, Elf_Word reloff)
490 const Obj_Entry *defobj;
496 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff);
498 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff);
500 where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
501 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
505 target = (Elf_Addr)(defobj->relocbase + def->st_value);
507 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"",
508 defobj->strtab + def->st_name, basename(obj->path),
509 (void *)target, basename(defobj->path));
511 reloc_jmpslot(where, target);
517 * Error reporting function. Use it like printf. If formats the message
518 * into a buffer, and sets things up so that the next call to dlerror()
519 * will return the message.
522 _rtld_error(const char *fmt, ...)
524 static char buf[512];
528 vsnprintf(buf, sizeof buf, fmt, ap);
534 * Return a dynamically-allocated copy of the current error message, if any.
539 return error_message == NULL ? NULL : xstrdup(error_message);
543 * Restore the current error message from a copy which was previously saved
544 * by errmsg_save(). The copy is freed.
547 errmsg_restore(char *saved_msg)
549 if (saved_msg == NULL)
550 error_message = NULL;
552 _rtld_error("%s", saved_msg);
558 basename(const char *name)
560 const char *p = strrchr(name, '/');
561 return p != NULL ? p + 1 : name;
567 const char *msg = dlerror();
575 * Process a shared object's DYNAMIC section, and save the important
576 * information in its Obj_Entry structure.
579 digest_dynamic(Obj_Entry *obj)
582 Needed_Entry **needed_tail = &obj->needed;
583 const Elf_Dyn *dyn_rpath = NULL;
584 int plttype = DT_REL;
586 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) {
587 switch (dynp->d_tag) {
590 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr);
594 obj->relsize = dynp->d_un.d_val;
598 assert(dynp->d_un.d_val == sizeof(Elf_Rel));
602 obj->pltrel = (const Elf_Rel *)
603 (obj->relocbase + dynp->d_un.d_ptr);
607 obj->pltrelsize = dynp->d_un.d_val;
611 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr);
615 obj->relasize = dynp->d_un.d_val;
619 assert(dynp->d_un.d_val == sizeof(Elf_Rela));
623 plttype = dynp->d_un.d_val;
624 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA);
628 obj->symtab = (const Elf_Sym *)
629 (obj->relocbase + dynp->d_un.d_ptr);
633 assert(dynp->d_un.d_val == sizeof(Elf_Sym));
637 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr);
641 obj->strsize = dynp->d_un.d_val;
646 const Elf_Addr *hashtab = (const Elf_Addr *)
647 (obj->relocbase + dynp->d_un.d_ptr);
648 obj->nbuckets = hashtab[0];
649 obj->nchains = hashtab[1];
650 obj->buckets = hashtab + 2;
651 obj->chains = obj->buckets + obj->nbuckets;
657 Needed_Entry *nep = NEW(Needed_Entry);
658 nep->name = dynp->d_un.d_val;
663 needed_tail = &nep->next;
668 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr);
676 obj->symbolic = true;
681 * We have to wait until later to process this, because we
682 * might not have gotten the address of the string table yet.
688 /* Not used by the dynamic linker. */
692 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
696 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
700 /* XXX - not implemented yet */
701 dbg("Filling in DT_DEBUG entry");
702 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug;
706 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag);
713 if (plttype == DT_RELA) {
714 obj->pltrela = (const Elf_Rela *) obj->pltrel;
716 obj->pltrelasize = obj->pltrelsize;
720 if (dyn_rpath != NULL)
721 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val;
725 * Process a shared object's program header. This is used only for the
726 * main program, when the kernel has already loaded the main program
727 * into memory before calling the dynamic linker. It creates and
728 * returns an Obj_Entry structure.
731 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
734 const Elf_Phdr *phlimit = phdr + phnum;
739 for (ph = phdr; ph < phlimit; ph++) {
740 switch (ph->p_type) {
743 if ((const Elf_Phdr *)ph->p_vaddr != phdr) {
744 _rtld_error("%s: invalid PT_PHDR", path);
747 obj->phdr = (const Elf_Phdr *) ph->p_vaddr;
748 obj->phsize = ph->p_memsz;
752 obj->interp = (const char *) ph->p_vaddr;
756 if (nsegs == 0) { /* First load segment */
757 obj->vaddrbase = trunc_page(ph->p_vaddr);
758 obj->mapbase = (caddr_t) obj->vaddrbase;
759 obj->relocbase = obj->mapbase - obj->vaddrbase;
760 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
762 } else { /* Last load segment */
763 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) -
770 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr;
775 _rtld_error("%s: too few PT_LOAD segments", path);
784 dlcheck(void *handle)
788 for (obj = obj_list; obj != NULL; obj = obj->next)
789 if (obj == (Obj_Entry *) handle)
792 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) {
793 _rtld_error("Invalid shared object handle %p", handle);
800 * If the given object is already in the donelist, return true. Otherwise
801 * add the object to the list and return false.
804 donelist_check(DoneList *dlp, const Obj_Entry *obj)
808 for (i = 0; i < dlp->num_used; i++)
809 if (dlp->objs[i] == obj)
812 * Our donelist allocation should always be sufficient. But if
813 * our threads locking isn't working properly, more shared objects
814 * could have been loaded since we allocated the list. That should
815 * never happen, but we'll handle it properly just in case it does.
817 if (dlp->num_used < dlp->num_alloc)
818 dlp->objs[dlp->num_used++] = obj;
823 * Hash function for symbol table lookup. Don't even think about changing
824 * this. It is specified by the System V ABI.
827 elf_hash(const char *name)
829 const unsigned char *p = (const unsigned char *) name;
835 if ((g = h & 0xf0000000) != 0)
843 * Find the library with the given name, and return its full pathname.
844 * The returned string is dynamically allocated. Generates an error
845 * message and returns NULL if the library cannot be found.
847 * If the second argument is non-NULL, then it refers to an already-
848 * loaded shared object, whose library search path will be searched.
850 * The search order is:
852 * rpath in the referencing file
857 find_library(const char *name, const Obj_Entry *refobj)
861 if (strchr(name, '/') != NULL) { /* Hard coded pathname */
862 if (name[0] != '/' && !trust) {
863 _rtld_error("Absolute pathname required for shared object \"%s\"",
867 return xstrdup(name);
870 dbg(" Searching for \"%s\"", name);
872 if ((pathname = search_library_path(name, ld_library_path)) != NULL ||
874 (pathname = search_library_path(name, refobj->rpath)) != NULL) ||
875 (pathname = search_library_path(name, gethints())) != NULL ||
876 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL)
879 if(refobj != NULL && refobj->path != NULL) {
880 _rtld_error("Shared object \"%s\" not found, required by \"%s\"",
881 name, basename(refobj->path));
883 _rtld_error("Shared object \"%s\" not found", name);
889 * Given a symbol number in a referencing object, find the corresponding
890 * definition of the symbol. Returns a pointer to the symbol, or NULL if
891 * no definition was found. Returns a pointer to the Obj_Entry of the
892 * defining object via the reference parameter DEFOBJ_OUT.
895 find_symdef(unsigned long symnum, const Obj_Entry *refobj,
896 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache)
900 const Obj_Entry *defobj;
905 * If we have already found this symbol, get the information from
908 if (symnum >= refobj->nchains)
909 return NULL; /* Bad object */
910 if (cache != NULL && cache[symnum].sym != NULL) {
911 *defobj_out = cache[symnum].obj;
912 return cache[symnum].sym;
915 ref = refobj->symtab + symnum;
916 name = refobj->strtab + ref->st_name;
917 hash = elf_hash(name);
920 def = symlook_default(name, hash, refobj, &defobj, in_plt);
923 * If we found no definition and the reference is weak, treat the
924 * symbol as having the value zero.
926 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) {
932 *defobj_out = defobj;
933 /* Record the information in the cache to avoid subsequent lookups. */
935 cache[symnum].sym = def;
936 cache[symnum].obj = defobj;
939 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
944 * Return the search path from the ldconfig hints file, reading it if
945 * necessary. Returns NULL if there are problems with the hints file,
946 * or if the search path there is empty.
955 struct elfhints_hdr hdr;
958 /* Keep from trying again in case the hints file is bad. */
961 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1)
963 if (read(fd, &hdr, sizeof hdr) != sizeof hdr ||
964 hdr.magic != ELFHINTS_MAGIC ||
969 p = xmalloc(hdr.dirlistlen + 1);
970 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 ||
971 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) {
979 return hints[0] != '\0' ? hints : NULL;
983 init_dag(Obj_Entry *root)
987 donelist_init(&donelist);
988 init_dag1(root, root, &donelist);
992 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp)
994 const Needed_Entry *needed;
996 if (donelist_check(dlp, obj))
998 objlist_push_tail(&obj->dldags, root);
999 objlist_push_tail(&root->dagmembers, obj);
1000 for (needed = obj->needed; needed != NULL; needed = needed->next)
1001 if (needed->obj != NULL)
1002 init_dag1(root, needed->obj, dlp);
1006 * Initialize the dynamic linker. The argument is the address at which
1007 * the dynamic linker has been mapped into memory. The primary task of
1008 * this function is to relocate the dynamic linker.
1011 init_rtld(caddr_t mapbase)
1014 * Conjure up an Obj_Entry structure for the dynamic linker.
1016 * The "path" member is supposed to be dynamically-allocated, but we
1017 * aren't yet initialized sufficiently to do that. Below we will
1018 * replace the static version with a dynamically-allocated copy.
1020 obj_rtld.path = PATH_RTLD;
1021 obj_rtld.rtld = true;
1022 obj_rtld.mapbase = mapbase;
1024 obj_rtld.relocbase = mapbase;
1026 if (&_DYNAMIC != 0) {
1027 obj_rtld.dynamic = rtld_dynamic(&obj_rtld);
1028 digest_dynamic(&obj_rtld);
1029 assert(obj_rtld.needed == NULL);
1030 assert(!obj_rtld.textrel);
1033 * Temporarily put the dynamic linker entry into the object list, so
1034 * that symbols can be found.
1036 obj_list = &obj_rtld;
1037 obj_tail = &obj_rtld.next;
1040 relocate_objects(&obj_rtld, true);
1043 /* Make the object list empty again. */
1045 obj_tail = &obj_list;
1048 /* Replace the path with a dynamically allocated copy. */
1049 obj_rtld.path = xstrdup(obj_rtld.path);
1051 r_debug.r_brk = r_debug_state;
1052 r_debug.r_state = RT_CONSISTENT;
1056 * Add the init functions from a needed object list (and its recursive
1057 * needed objects) to "list". This is not used directly; it is a helper
1058 * function for initlist_add_objects(). The write lock must be held
1059 * when this function is called.
1062 initlist_add_neededs(Needed_Entry *needed, Objlist *list)
1064 /* Recursively process the successor needed objects. */
1065 if (needed->next != NULL)
1066 initlist_add_neededs(needed->next, list);
1068 /* Process the current needed object. */
1069 if (needed->obj != NULL)
1070 initlist_add_objects(needed->obj, &needed->obj->next, list);
1074 * Scan all of the DAGs rooted in the range of objects from "obj" to
1075 * "tail" and add their init functions to "list". This recurses over
1076 * the DAGs and ensure the proper init ordering such that each object's
1077 * needed libraries are initialized before the object itself. At the
1078 * same time, this function adds the objects to the global finalization
1079 * list "list_fini" in the opposite order. The write lock must be
1080 * held when this function is called.
1083 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list)
1087 obj->init_done = true;
1089 /* Recursively process the successor objects. */
1090 if (&obj->next != tail)
1091 initlist_add_objects(obj->next, tail, list);
1093 /* Recursively process the needed objects. */
1094 if (obj->needed != NULL)
1095 initlist_add_neededs(obj->needed, list);
1097 /* Add the object to the init list. */
1098 if (obj->init != NULL)
1099 objlist_push_tail(list, obj);
1101 /* Add the object to the global fini list in the reverse order. */
1102 if (obj->fini != NULL)
1103 objlist_push_head(&list_fini, obj);
1107 is_exported(const Elf_Sym *def)
1109 func_ptr_type value;
1110 const func_ptr_type *p;
1112 value = (func_ptr_type)(obj_rtld.relocbase + def->st_value);
1113 for (p = exports; *p != NULL; p++)
1120 * Given a shared object, traverse its list of needed objects, and load
1121 * each of them. Returns 0 on success. Generates an error message and
1122 * returns -1 on failure.
1125 load_needed_objects(Obj_Entry *first)
1129 for (obj = first; obj != NULL; obj = obj->next) {
1130 Needed_Entry *needed;
1132 for (needed = obj->needed; needed != NULL; needed = needed->next) {
1133 const char *name = obj->strtab + needed->name;
1134 char *path = find_library(name, obj);
1137 if (path == NULL && !ld_tracing)
1141 needed->obj = load_object(path);
1142 if (needed->obj == NULL && !ld_tracing)
1143 return -1; /* XXX - cleanup */
1152 load_preload_objects(void)
1154 char *p = ld_preload;
1155 static const char delim[] = " \t:;";
1160 p += strspn(p, delim);
1161 while (*p != '\0') {
1162 size_t len = strcspn(p, delim);
1168 if ((path = find_library(p, NULL)) == NULL)
1170 if (load_object(path) == NULL)
1171 return -1; /* XXX - cleanup */
1174 p += strspn(p, delim);
1180 * Load a shared object into memory, if it is not already loaded. The
1181 * argument must be a string allocated on the heap. This function assumes
1182 * responsibility for freeing it when necessary.
1184 * Returns a pointer to the Obj_Entry for the object. Returns NULL
1188 load_object(char *path)
1194 for (obj = obj_list->next; obj != NULL; obj = obj->next)
1195 if (strcmp(obj->path, path) == 0)
1199 * If we didn't find a match by pathname, open the file and check
1200 * again by device and inode. This avoids false mismatches caused
1201 * by multiple links or ".." in pathnames.
1203 * To avoid a race, we open the file and use fstat() rather than
1207 if ((fd = open(path, O_RDONLY)) == -1) {
1208 _rtld_error("Cannot open \"%s\"", path);
1211 if (fstat(fd, &sb) == -1) {
1212 _rtld_error("Cannot fstat \"%s\"", path);
1216 for (obj = obj_list->next; obj != NULL; obj = obj->next) {
1217 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) {
1224 if (obj == NULL) { /* First use of this object, so we must map it in */
1225 dbg("loading \"%s\"", path);
1226 obj = map_object(fd, path, &sb);
1234 digest_dynamic(obj);
1237 obj_tail = &obj->next;
1239 linkmap_add(obj); /* for GDB & dlinfo() */
1241 dbg(" %p .. %p: %s", obj->mapbase,
1242 obj->mapbase + obj->mapsize - 1, obj->path);
1244 dbg(" WARNING: %s has impure text", obj->path);
1253 * Check for locking violations and die if one is found.
1260 rcount = lockinfo.rcount;
1261 wcount = lockinfo.wcount;
1262 assert(rcount >= 0);
1263 assert(wcount >= 0);
1264 if (wcount > 1 || (wcount != 0 && rcount != 0)) {
1265 _rtld_error("Application locking error: %d readers and %d writers"
1266 " in dynamic linker. See DLLOCKINIT(3) in manual pages.",
1273 obj_from_addr(const void *addr)
1275 unsigned long endhash;
1278 endhash = elf_hash(END_SYM);
1279 for (obj = obj_list; obj != NULL; obj = obj->next) {
1280 const Elf_Sym *endsym;
1282 if (addr < (void *) obj->mapbase)
1284 if ((endsym = symlook_obj(END_SYM, endhash, obj, true)) == NULL)
1285 continue; /* No "end" symbol?! */
1286 if (addr < (void *) (obj->relocbase + endsym->st_value))
1293 * Call the finalization functions for each of the objects in "list"
1294 * which are unreferenced. All of the objects are expected to have
1295 * non-NULL fini functions.
1298 objlist_call_fini(Objlist *list)
1304 * Preserve the current error message since a fini function might
1305 * call into the dynamic linker and overwrite it.
1307 saved_msg = errmsg_save();
1308 STAILQ_FOREACH(elm, list, link) {
1309 if (elm->obj->refcount == 0) {
1310 dbg("calling fini function for %s", elm->obj->path);
1311 (*elm->obj->fini)();
1314 errmsg_restore(saved_msg);
1318 * Call the initialization functions for each of the objects in
1319 * "list". All of the objects are expected to have non-NULL init
1323 objlist_call_init(Objlist *list)
1329 * Preserve the current error message since an init function might
1330 * call into the dynamic linker and overwrite it.
1332 saved_msg = errmsg_save();
1333 STAILQ_FOREACH(elm, list, link) {
1334 dbg("calling init function for %s", elm->obj->path);
1335 (*elm->obj->init)();
1337 errmsg_restore(saved_msg);
1341 objlist_clear(Objlist *list)
1345 while (!STAILQ_EMPTY(list)) {
1346 elm = STAILQ_FIRST(list);
1347 STAILQ_REMOVE_HEAD(list, link);
1352 static Objlist_Entry *
1353 objlist_find(Objlist *list, const Obj_Entry *obj)
1357 STAILQ_FOREACH(elm, list, link)
1358 if (elm->obj == obj)
1364 objlist_init(Objlist *list)
1370 objlist_push_head(Objlist *list, Obj_Entry *obj)
1374 elm = NEW(Objlist_Entry);
1376 STAILQ_INSERT_HEAD(list, elm, link);
1380 objlist_push_tail(Objlist *list, Obj_Entry *obj)
1384 elm = NEW(Objlist_Entry);
1386 STAILQ_INSERT_TAIL(list, elm, link);
1390 objlist_remove(Objlist *list, Obj_Entry *obj)
1394 if ((elm = objlist_find(list, obj)) != NULL) {
1395 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link);
1401 * Remove all of the unreferenced objects from "list".
1404 objlist_remove_unref(Objlist *list)
1409 STAILQ_INIT(&newlist);
1410 while (!STAILQ_EMPTY(list)) {
1411 elm = STAILQ_FIRST(list);
1412 STAILQ_REMOVE_HEAD(list, link);
1413 if (elm->obj->refcount == 0)
1416 STAILQ_INSERT_TAIL(&newlist, elm, link);
1422 * Relocate newly-loaded shared objects. The argument is a pointer to
1423 * the Obj_Entry for the first such object. All objects from the first
1424 * to the end of the list of objects are relocated. Returns 0 on success,
1428 relocate_objects(Obj_Entry *first, bool bind_now)
1432 for (obj = first; obj != NULL; obj = obj->next) {
1433 if (obj != &obj_rtld)
1434 dbg("relocating \"%s\"", obj->path);
1435 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL ||
1436 obj->symtab == NULL || obj->strtab == NULL) {
1437 _rtld_error("%s: Shared object has no run-time symbol table",
1443 /* There are relocations to the write-protected text segment. */
1444 if (mprotect(obj->mapbase, obj->textsize,
1445 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
1446 _rtld_error("%s: Cannot write-enable text segment: %s",
1447 obj->path, strerror(errno));
1452 /* Process the non-PLT relocations. */
1453 if (reloc_non_plt(obj, &obj_rtld))
1457 * Reprotect the text segment. Make sure it is included in the
1458 * core dump since we modified it. This unfortunately causes the
1459 * entire text segment to core-out but we don't have much of a
1460 * choice. We could try to only reenable core dumps on pages
1461 * in which relocations occured but that is likely most of the text
1462 * pages anyway, and even that would not work because the rest of
1463 * the text pages would wind up as a read-only OBJT_DEFAULT object
1464 * (created due to our modifications) backed by the original OBJT_VNODE
1465 * object, and the ELF coredump code is currently only able to dump
1466 * vnode records for pure vnode-backed mappings, not vnode backings
1467 * to memory objects.
1470 madvise(obj->mapbase, obj->textsize, MADV_CORE);
1471 if (mprotect(obj->mapbase, obj->textsize,
1472 PROT_READ|PROT_EXEC) == -1) {
1473 _rtld_error("%s: Cannot write-protect text segment: %s",
1474 obj->path, strerror(errno));
1479 /* Process the PLT relocations. */
1480 if (reloc_plt(obj) == -1)
1482 /* Relocate the jump slots if we are doing immediate binding. */
1484 if (reloc_jmpslots(obj) == -1)
1489 * Set up the magic number and version in the Obj_Entry. These
1490 * were checked in the crt1.o from the original ElfKit, so we
1491 * set them for backward compatibility.
1493 obj->magic = RTLD_MAGIC;
1494 obj->version = RTLD_VERSION;
1496 /* Set the special PLT or GOT entries. */
1504 * Cleanup procedure. It will be called (by the atexit mechanism) just
1505 * before the process exits.
1513 /* Clear all the reference counts so the fini functions will be called. */
1514 for (obj = obj_list; obj != NULL; obj = obj->next)
1516 objlist_call_fini(&list_fini);
1517 /* No need to remove the items from the list, since we are exiting. */
1521 path_enumerate(const char *path, path_enum_proc callback, void *arg)
1526 path += strspn(path, ":;");
1527 while (*path != '\0') {
1531 len = strcspn(path, ":;");
1532 res = callback(path, len, arg);
1538 path += strspn(path, ":;");
1544 struct try_library_args {
1552 try_library_path(const char *dir, size_t dirlen, void *param)
1554 struct try_library_args *arg;
1557 if (*dir == '/' || trust) {
1560 if (dirlen + 1 + arg->namelen + 1 > arg->buflen)
1563 pathname = arg->buffer;
1564 strncpy(pathname, dir, dirlen);
1565 pathname[dirlen] = '/';
1566 strcpy(pathname + dirlen + 1, arg->name);
1568 dbg(" Trying \"%s\"", pathname);
1569 if (access(pathname, F_OK) == 0) { /* We found it */
1570 pathname = xmalloc(dirlen + 1 + arg->namelen + 1);
1571 strcpy(pathname, arg->buffer);
1579 search_library_path(const char *name, const char *path)
1582 struct try_library_args arg;
1588 arg.namelen = strlen(name);
1589 arg.buffer = xmalloc(PATH_MAX);
1590 arg.buflen = PATH_MAX;
1592 p = path_enumerate(path, try_library_path, &arg);
1600 dlclose(void *handle)
1605 root = dlcheck(handle);
1611 /* Unreference the object and its dependencies. */
1612 root->dl_refcount--;
1615 if (root->refcount == 0) {
1617 * The object is no longer referenced, so we must unload it.
1618 * First, call the fini functions with no locks held.
1621 objlist_call_fini(&list_fini);
1623 objlist_remove_unref(&list_fini);
1625 /* Finish cleaning up the newly-unreferenced objects. */
1626 GDB_STATE(RT_DELETE,&root->linkmap);
1627 unload_object(root);
1628 GDB_STATE(RT_CONSISTENT,NULL);
1637 char *msg = error_message;
1638 error_message = NULL;
1643 * This function is deprecated and has no effect.
1646 dllockinit(void *context,
1647 void *(*lock_create)(void *context),
1648 void (*rlock_acquire)(void *lock),
1649 void (*wlock_acquire)(void *lock),
1650 void (*lock_release)(void *lock),
1651 void (*lock_destroy)(void *lock),
1652 void (*context_destroy)(void *context))
1654 static void *cur_context;
1655 static void (*cur_context_destroy)(void *);
1657 /* Just destroy the context from the previous call, if necessary. */
1658 if (cur_context_destroy != NULL)
1659 cur_context_destroy(cur_context);
1660 cur_context = context;
1661 cur_context_destroy = context_destroy;
1665 dlopen(const char *name, int mode)
1667 Obj_Entry **old_obj_tail;
1672 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1";
1673 if (ld_tracing != NULL)
1674 environ = (char **)*get_program_var_addr("environ");
1676 objlist_init(&initlist);
1679 GDB_STATE(RT_ADD,NULL);
1681 old_obj_tail = obj_tail;
1687 char *path = find_library(name, obj_main);
1689 obj = load_object(path);
1694 if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL)
1695 objlist_push_tail(&list_global, obj);
1696 mode &= RTLD_MODEMASK;
1697 if (*old_obj_tail != NULL) { /* We loaded something new. */
1698 assert(*old_obj_tail == obj);
1700 result = load_needed_objects(obj);
1701 if (result != -1 && ld_tracing)
1705 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW)) == -1) {
1708 if (obj->refcount == 0)
1712 /* Make list of init functions to call. */
1713 initlist_add_objects(obj, &obj->next, &initlist);
1715 } else if (ld_tracing)
1719 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL);
1721 /* Call the init functions with no locks held. */
1723 objlist_call_init(&initlist);
1725 objlist_clear(&initlist);
1729 trace_loaded_objects(obj);
1735 dlsym(void *handle, const char *name)
1737 const Obj_Entry *obj;
1740 const Obj_Entry *defobj;
1742 hash = elf_hash(name);
1747 if (handle == NULL || handle == RTLD_NEXT ||
1748 handle == RTLD_DEFAULT || handle == RTLD_SELF) {
1751 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1752 if ((obj = obj_from_addr(retaddr)) == NULL) {
1753 _rtld_error("Cannot determine caller's shared object");
1757 if (handle == NULL) { /* Just the caller's shared object. */
1758 def = symlook_obj(name, hash, obj, true);
1760 } else if (handle == RTLD_NEXT || /* Objects after caller's */
1761 handle == RTLD_SELF) { /* ... caller included */
1762 if (handle == RTLD_NEXT)
1764 for (; obj != NULL; obj = obj->next) {
1765 if ((def = symlook_obj(name, hash, obj, true)) != NULL) {
1771 assert(handle == RTLD_DEFAULT);
1772 def = symlook_default(name, hash, obj, &defobj, true);
1775 if ((obj = dlcheck(handle)) == NULL) {
1780 if (obj->mainprog) {
1783 /* Search main program and all libraries loaded by it. */
1784 donelist_init(&donelist);
1785 def = symlook_list(name, hash, &list_main, &defobj, true,
1789 * XXX - This isn't correct. The search should include the whole
1790 * DAG rooted at the given object.
1792 def = symlook_obj(name, hash, obj, true);
1799 return defobj->relocbase + def->st_value;
1802 _rtld_error("Undefined symbol \"%s\"", name);
1808 dladdr(const void *addr, Dl_info *info)
1810 const Obj_Entry *obj;
1813 unsigned long symoffset;
1816 obj = obj_from_addr(addr);
1818 _rtld_error("No shared object contains address");
1822 info->dli_fname = obj->path;
1823 info->dli_fbase = obj->mapbase;
1824 info->dli_saddr = (void *)0;
1825 info->dli_sname = NULL;
1828 * Walk the symbol list looking for the symbol whose address is
1829 * closest to the address sent in.
1831 for (symoffset = 0; symoffset < obj->nchains; symoffset++) {
1832 def = obj->symtab + symoffset;
1835 * For skip the symbol if st_shndx is either SHN_UNDEF or
1838 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON)
1842 * If the symbol is greater than the specified address, or if it
1843 * is further away from addr than the current nearest symbol,
1846 symbol_addr = obj->relocbase + def->st_value;
1847 if (symbol_addr > addr || symbol_addr < info->dli_saddr)
1850 /* Update our idea of the nearest symbol. */
1851 info->dli_sname = obj->strtab + def->st_name;
1852 info->dli_saddr = symbol_addr;
1855 if (info->dli_saddr == addr)
1863 dlinfo(void *handle, int request, void *p)
1865 const Obj_Entry *obj;
1870 if (handle == NULL || handle == RTLD_SELF) {
1873 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1874 if ((obj = obj_from_addr(retaddr)) == NULL)
1875 _rtld_error("Cannot determine caller's shared object");
1877 obj = dlcheck(handle);
1886 case RTLD_DI_LINKMAP:
1887 *((struct link_map const **)p) = &obj->linkmap;
1889 case RTLD_DI_ORIGIN:
1890 error = rtld_dirname(obj->path, p);
1893 case RTLD_DI_SERINFOSIZE:
1894 case RTLD_DI_SERINFO:
1895 error = do_search_info(obj, request, (struct dl_serinfo *)p);
1899 _rtld_error("Invalid request %d passed to dlinfo()", request);
1908 struct fill_search_info_args {
1911 Dl_serinfo *serinfo;
1912 Dl_serpath *serpath;
1917 fill_search_info(const char *dir, size_t dirlen, void *param)
1919 struct fill_search_info_args *arg;
1923 if (arg->request == RTLD_DI_SERINFOSIZE) {
1924 arg->serinfo->dls_cnt ++;
1925 arg->serinfo->dls_size += dirlen + 1;
1927 struct dl_serpath *s_entry;
1929 s_entry = arg->serpath;
1930 s_entry->dls_name = arg->strspace;
1931 s_entry->dls_flags = arg->flags;
1933 strncpy(arg->strspace, dir, dirlen);
1934 arg->strspace[dirlen] = '\0';
1936 arg->strspace += dirlen + 1;
1944 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info)
1946 struct dl_serinfo _info;
1947 struct fill_search_info_args args;
1949 args.request = RTLD_DI_SERINFOSIZE;
1950 args.serinfo = &_info;
1952 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath);
1955 path_enumerate(ld_library_path, fill_search_info, &args);
1956 path_enumerate(obj->rpath, fill_search_info, &args);
1957 path_enumerate(gethints(), fill_search_info, &args);
1958 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args);
1961 if (request == RTLD_DI_SERINFOSIZE) {
1962 info->dls_size = _info.dls_size;
1963 info->dls_cnt = _info.dls_cnt;
1967 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) {
1968 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()");
1972 args.request = RTLD_DI_SERINFO;
1973 args.serinfo = info;
1974 args.serpath = &info->dls_serpath[0];
1975 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt];
1977 args.flags = LA_SER_LIBPATH;
1978 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL)
1981 args.flags = LA_SER_RUNPATH;
1982 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL)
1985 args.flags = LA_SER_CONFIG;
1986 if (path_enumerate(gethints(), fill_search_info, &args) != NULL)
1989 args.flags = LA_SER_DEFAULT;
1990 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL)
1996 rtld_dirname(const char *path, char *bname)
2000 /* Empty or NULL string gets treated as "." */
2001 if (path == NULL || *path == '\0') {
2007 /* Strip trailing slashes */
2008 endp = path + strlen(path) - 1;
2009 while (endp > path && *endp == '/')
2012 /* Find the start of the dir */
2013 while (endp > path && *endp != '/')
2016 /* Either the dir is "/" or there are no slashes */
2018 bname[0] = *endp == '/' ? '/' : '.';
2024 } while (endp > path && *endp == '/');
2027 if (endp - path + 2 > PATH_MAX)
2029 _rtld_error("Filename is too long: %s", path);
2033 strncpy(bname, path, endp - path + 1);
2034 bname[endp - path + 1] = '\0';
2039 linkmap_add(Obj_Entry *obj)
2041 struct link_map *l = &obj->linkmap;
2042 struct link_map *prev;
2044 obj->linkmap.l_name = obj->path;
2045 obj->linkmap.l_addr = obj->mapbase;
2046 obj->linkmap.l_ld = obj->dynamic;
2048 /* GDB needs load offset on MIPS to use the symbols */
2049 obj->linkmap.l_offs = obj->relocbase;
2052 if (r_debug.r_map == NULL) {
2058 * Scan to the end of the list, but not past the entry for the
2059 * dynamic linker, which we want to keep at the very end.
2061 for (prev = r_debug.r_map;
2062 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap;
2063 prev = prev->l_next)
2066 /* Link in the new entry. */
2068 l->l_next = prev->l_next;
2069 if (l->l_next != NULL)
2070 l->l_next->l_prev = l;
2075 linkmap_delete(Obj_Entry *obj)
2077 struct link_map *l = &obj->linkmap;
2079 if (l->l_prev == NULL) {
2080 if ((r_debug.r_map = l->l_next) != NULL)
2081 l->l_next->l_prev = NULL;
2085 if ((l->l_prev->l_next = l->l_next) != NULL)
2086 l->l_next->l_prev = l->l_prev;
2090 * Function for the debugger to set a breakpoint on to gain control.
2092 * The two parameters allow the debugger to easily find and determine
2093 * what the runtime loader is doing and to whom it is doing it.
2095 * When the loadhook trap is hit (r_debug_state, set at program
2096 * initialization), the arguments can be found on the stack:
2098 * +8 struct link_map *m
2099 * +4 struct r_debug *rd
2103 r_debug_state(struct r_debug* rd, struct link_map *m)
2108 * Get address of the pointer variable in the main program.
2110 static const void **
2111 get_program_var_addr(const char *name)
2113 const Obj_Entry *obj;
2116 hash = elf_hash(name);
2117 for (obj = obj_main; obj != NULL; obj = obj->next) {
2120 if ((def = symlook_obj(name, hash, obj, false)) != NULL) {
2123 addr = (const void **)(obj->relocbase + def->st_value);
2131 * Set a pointer variable in the main program to the given value. This
2132 * is used to set key variables such as "environ" before any of the
2133 * init functions are called.
2136 set_program_var(const char *name, const void *value)
2140 if ((addr = get_program_var_addr(name)) != NULL) {
2141 dbg("\"%s\": *%p <-- %p", name, addr, value);
2147 * This is a special version of getenv which is far more efficient
2148 * at finding LD_ environment vars.
2152 _getenv_ld(const char *id)
2156 int idlen = strlen(id);
2158 if (ld_index == LD_ARY_CACHE)
2160 if (ld_index == 0) {
2161 for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) {
2162 if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_')
2169 for (i = ld_index - 1; i >= 0; --i) {
2170 if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=')
2171 return(ld_ary[i] + idlen + 1);
2177 * Given a symbol name in a referencing object, find the corresponding
2178 * definition of the symbol. Returns a pointer to the symbol, or NULL if
2179 * no definition was found. Returns a pointer to the Obj_Entry of the
2180 * defining object via the reference parameter DEFOBJ_OUT.
2182 static const Elf_Sym *
2183 symlook_default(const char *name, unsigned long hash,
2184 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt)
2188 const Elf_Sym *symp;
2189 const Obj_Entry *obj;
2190 const Obj_Entry *defobj;
2191 const Objlist_Entry *elm;
2194 donelist_init(&donelist);
2196 /* Look first in the referencing object if linked symbolically. */
2197 if (refobj->symbolic && !donelist_check(&donelist, refobj)) {
2198 symp = symlook_obj(name, hash, refobj, in_plt);
2205 /* Search all objects loaded at program start up. */
2206 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2207 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist);
2209 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2215 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */
2216 STAILQ_FOREACH(elm, &list_global, link) {
2217 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2219 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2222 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2228 /* Search all dlopened DAGs containing the referencing object. */
2229 STAILQ_FOREACH(elm, &refobj->dldags, link) {
2230 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2232 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2235 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2242 * Search the dynamic linker itself, and possibly resolve the
2243 * symbol from there. This is how the application links to
2244 * dynamic linker services such as dlopen. Only the values listed
2245 * in the "exports" array can be resolved from the dynamic linker.
2247 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2248 symp = symlook_obj(name, hash, &obj_rtld, in_plt);
2249 if (symp != NULL && is_exported(symp)) {
2256 *defobj_out = defobj;
2260 static const Elf_Sym *
2261 symlook_list(const char *name, unsigned long hash, Objlist *objlist,
2262 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)
2264 const Elf_Sym *symp;
2266 const Obj_Entry *defobj;
2267 const Objlist_Entry *elm;
2271 STAILQ_FOREACH(elm, objlist, link) {
2272 if (donelist_check(dlp, elm->obj))
2274 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) {
2275 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) {
2278 if (ELF_ST_BIND(def->st_info) != STB_WEAK)
2284 *defobj_out = defobj;
2289 * Search the symbol table of a single shared object for a symbol of
2290 * the given name. Returns a pointer to the symbol, or NULL if no
2291 * definition was found.
2293 * The symbol's hash value is passed in for efficiency reasons; that
2294 * eliminates many recomputations of the hash value.
2297 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj,
2300 if (obj->buckets != NULL) {
2301 unsigned long symnum = obj->buckets[hash % obj->nbuckets];
2303 while (symnum != STN_UNDEF) {
2304 const Elf_Sym *symp;
2307 if (symnum >= obj->nchains)
2308 return NULL; /* Bad object */
2309 symp = obj->symtab + symnum;
2310 strp = obj->strtab + symp->st_name;
2312 if (name[0] == strp[0] && strcmp(name, strp) == 0)
2313 return symp->st_shndx != SHN_UNDEF ||
2314 (!in_plt && symp->st_value != 0 &&
2315 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL;
2317 symnum = obj->chains[symnum];
2324 trace_loaded_objects(Obj_Entry *obj)
2326 const char *fmt1, *fmt2, *fmt, *main_local;
2329 if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL)
2332 if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL)
2333 fmt1 = "\t%o => %p (%x)\n";
2335 if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL)
2336 fmt2 = "\t%o (%x)\n";
2338 for (; obj; obj = obj->next) {
2339 Needed_Entry *needed;
2343 for (needed = obj->needed; needed; needed = needed->next) {
2344 if (needed->obj != NULL) {
2345 if (needed->obj->traced)
2347 needed->obj->traced = true;
2348 path = needed->obj->path;
2352 name = (char *)obj->strtab + needed->name;
2353 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */
2355 fmt = is_lib ? fmt1 : fmt2;
2356 while ((c = *fmt++) != '\0') {
2382 printf("%s", main_local);
2385 printf("%s", obj_main->path);
2392 printf("%d", sodp->sod_major);
2395 printf("%d", sodp->sod_minor);
2402 printf("%p", needed->obj ? needed->obj->mapbase : 0);
2414 * Unload a dlopened object and its dependencies from memory and from
2415 * our data structures. It is assumed that the DAG rooted in the
2416 * object has already been unreferenced, and that the object has a
2417 * reference count of 0.
2420 unload_object(Obj_Entry *root)
2425 assert(root->refcount == 0);
2428 * Pass over the DAG removing unreferenced objects from
2429 * appropriate lists.
2431 unlink_object(root);
2433 /* Unmap all objects that are no longer referenced. */
2434 linkp = &obj_list->next;
2435 while ((obj = *linkp) != NULL) {
2436 if (obj->refcount == 0) {
2437 dbg("unloading \"%s\"", obj->path);
2438 munmap(obj->mapbase, obj->mapsize);
2439 linkmap_delete(obj);
2450 unlink_object(Obj_Entry *root)
2452 const Needed_Entry *needed;
2455 if (root->refcount == 0) {
2456 /* Remove the object from the RTLD_GLOBAL list. */
2457 objlist_remove(&list_global, root);
2459 /* Remove the object from all objects' DAG lists. */
2460 STAILQ_FOREACH(elm, &root->dagmembers , link)
2461 objlist_remove(&elm->obj->dldags, root);
2464 for (needed = root->needed; needed != NULL; needed = needed->next)
2465 if (needed->obj != NULL)
2466 unlink_object(needed->obj);
2470 unref_dag(Obj_Entry *root)
2472 const Needed_Entry *needed;
2474 if (root->refcount == 0)
2477 if (root->refcount == 0)
2478 for (needed = root->needed; needed != NULL; needed = needed->next)
2479 if (needed->obj != NULL)
2480 unref_dag(needed->obj);