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 1.29 2008/01/08 00:02:04 corecode 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>
46 #include <machine/tls.h>
61 #define PATH_RTLD "/usr/libexec/ld-elf.so.2"
62 #define LD_ARY_CACHE 16
65 typedef void (*func_ptr_type)();
66 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg);
69 * This structure provides a reentrant way to keep a list of objects and
70 * check which ones have already been processed in some way.
72 typedef struct Struct_DoneList {
73 const Obj_Entry **objs; /* Array of object pointers */
74 unsigned int num_alloc; /* Allocated size of the array */
75 unsigned int num_used; /* Number of array slots used */
79 * Function declarations.
81 static void die(void);
82 static void digest_dynamic(Obj_Entry *, int);
83 static const char *_getenv_ld(const char *id);
84 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
85 static Obj_Entry *dlcheck(void *);
86 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *);
87 static bool donelist_check(DoneList *, const Obj_Entry *);
88 static void errmsg_restore(char *);
89 static char *errmsg_save(void);
90 static void *fill_search_info(const char *, size_t, void *);
91 static char *find_library(const char *, const Obj_Entry *);
92 static Obj_Entry *find_object(const char *);
93 static Obj_Entry *find_object2(const char *, int *, struct stat *);
94 static const char *gethints(void);
95 static void init_dag(Obj_Entry *);
96 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *);
97 static void init_rtld(caddr_t);
98 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list);
99 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail,
101 static bool is_exported(const Elf_Sym *);
102 static void linkmap_add(Obj_Entry *);
103 static void linkmap_delete(Obj_Entry *);
104 static int load_needed_objects(Obj_Entry *);
105 static int load_preload_objects(void);
106 static Obj_Entry *load_object(char *);
107 static void lock_check(void);
108 static Obj_Entry *obj_from_addr(const void *);
109 static void objlist_call_fini(Objlist *);
110 static void objlist_call_init(Objlist *);
111 static void objlist_clear(Objlist *);
112 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *);
113 static void objlist_init(Objlist *);
114 static void objlist_push_head(Objlist *, Obj_Entry *);
115 static void objlist_push_tail(Objlist *, Obj_Entry *);
116 static void objlist_remove(Objlist *, Obj_Entry *);
117 static void objlist_remove_unref(Objlist *);
118 static void *path_enumerate(const char *, path_enum_proc, void *);
119 static int relocate_objects(Obj_Entry *, bool, Obj_Entry *);
120 static int rtld_dirname(const char *, char *);
121 static void rtld_exit(void);
122 static char *search_library_path(const char *, const char *);
123 static const void **get_program_var_addr(const char *name);
124 static void set_program_var(const char *, const void *);
125 static const Elf_Sym *symlook_default(const char *, unsigned long hash,
126 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt);
127 static const Elf_Sym *symlook_list(const char *, unsigned long,
128 const Objlist *, const Obj_Entry **, bool in_plt, DoneList *);
129 static const Elf_Sym *symlook_needed(const char *, unsigned long,
130 const Needed_Entry *, const Obj_Entry **, bool in_plt, DoneList *);
131 static void trace_loaded_objects(Obj_Entry *obj);
132 static void unlink_object(Obj_Entry *);
133 static void unload_object(Obj_Entry *);
134 static void unref_dag(Obj_Entry *);
136 void r_debug_state(struct r_debug*, struct link_map*);
141 static char *error_message; /* Message for dlerror(), or NULL */
142 struct r_debug r_debug; /* for GDB; */
143 static bool trust; /* False for setuid and setgid programs */
144 static const char *ld_bind_now; /* Environment variable for immediate binding */
145 static const char *ld_debug; /* Environment variable for debugging */
146 static const char *ld_library_path; /* Environment variable for search path */
147 static char *ld_preload; /* Environment variable for libraries to
149 static const char *ld_tracing; /* Called from ldd(1) to print libs */
150 /* Optional function call tracing hook */
151 static int (*rtld_functrace)(const char *caller_obj,
152 const char *callee_obj,
153 const char *callee_func,
155 static Obj_Entry *rtld_functrace_obj; /* Object thereof */
156 static Obj_Entry *obj_list; /* Head of linked list of shared objects */
157 static Obj_Entry **obj_tail; /* Link field of last object in list */
158 static Obj_Entry **preload_tail;
159 static Obj_Entry *obj_main; /* The main program shared object */
160 static Obj_Entry obj_rtld; /* The dynamic linker shared object */
161 static unsigned int obj_count; /* Number of objects in obj_list */
162 static int ld_resident; /* Non-zero if resident */
163 static const char *ld_ary[LD_ARY_CACHE];
165 static Objlist initlist;
167 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */
168 STAILQ_HEAD_INITIALIZER(list_global);
169 static Objlist list_main = /* Objects loaded at program startup */
170 STAILQ_HEAD_INITIALIZER(list_main);
171 static Objlist list_fini = /* Objects needing fini() calls */
172 STAILQ_HEAD_INITIALIZER(list_fini);
174 static LockInfo lockinfo;
176 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */
178 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m);
180 extern Elf_Dyn _DYNAMIC;
181 #pragma weak _DYNAMIC
184 * These are the functions the dynamic linker exports to application
185 * programs. They are the only symbols the dynamic linker is willing
186 * to export from itself.
188 static func_ptr_type exports[] = {
189 (func_ptr_type) &_rtld_error,
190 (func_ptr_type) &dlclose,
191 (func_ptr_type) &dlerror,
192 (func_ptr_type) &dlopen,
193 (func_ptr_type) &dlsym,
194 (func_ptr_type) &dladdr,
195 (func_ptr_type) &dlinfo,
197 (func_ptr_type) &___tls_get_addr,
199 (func_ptr_type) &__tls_get_addr,
200 (func_ptr_type) &__tls_get_addr_tcb,
201 (func_ptr_type) &_rtld_allocate_tls,
202 (func_ptr_type) &_rtld_free_tls,
203 (func_ptr_type) &_rtld_call_init,
208 * Global declarations normally provided by crt1. The dynamic linker is
209 * not built with crt1, so we have to provide them ourselves.
215 * Globals to control TLS allocation.
217 size_t tls_last_offset; /* Static TLS offset of last module */
218 size_t tls_last_size; /* Static TLS size of last module */
219 size_t tls_static_space; /* Static TLS space allocated */
220 int tls_dtv_generation = 1; /* Used to detect when dtv size changes */
221 int tls_max_index = 1; /* Largest module index allocated */
224 * Fill in a DoneList with an allocation large enough to hold all of
225 * the currently-loaded objects. Keep this as a macro since it calls
226 * alloca and we want that to occur within the scope of the caller.
228 #define donelist_init(dlp) \
229 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \
230 assert((dlp)->objs != NULL), \
231 (dlp)->num_alloc = obj_count, \
237 lockinfo.rlock_acquire(lockinfo.thelock);
238 atomic_incr_int(&lockinfo.rcount);
245 lockinfo.wlock_acquire(lockinfo.thelock);
246 atomic_incr_int(&lockinfo.wcount);
253 atomic_decr_int(&lockinfo.rcount);
254 lockinfo.rlock_release(lockinfo.thelock);
260 atomic_decr_int(&lockinfo.wcount);
261 lockinfo.wlock_release(lockinfo.thelock);
265 * Main entry point for dynamic linking. The first argument is the
266 * stack pointer. The stack is expected to be laid out as described
267 * in the SVR4 ABI specification, Intel 386 Processor Supplement.
268 * Specifically, the stack pointer points to a word containing
269 * ARGC. Following that in the stack is a null-terminated sequence
270 * of pointers to argument strings. Then comes a null-terminated
271 * sequence of pointers to environment strings. Finally, there is a
272 * sequence of "auxiliary vector" entries.
274 * The second argument points to a place to store the dynamic linker's
275 * exit procedure pointer and the third to a place to store the main
278 * The return value is the main program's entry point.
282 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
284 Elf_Auxinfo *aux_info[AT_COUNT];
292 Objlist_Entry *entry;
295 ld_index = 0; /* don't use old env cache in case we are resident */
298 * On entry, the dynamic linker itself has not been relocated yet.
299 * Be very careful not to reference any global data until after
300 * init_rtld has returned. It is OK to reference file-scope statics
301 * and string constants, and to call static and global functions.
304 /* Find the auxiliary vector on the stack. */
307 sp += argc + 1; /* Skip over arguments and NULL terminator */
311 * If we aren't already resident we have to dig out some more info.
312 * Note that auxinfo does not exist when we are resident.
314 if (ld_resident == 0) {
315 while (*sp++ != 0) /* Skip over environment, and NULL terminator */
317 aux = (Elf_Auxinfo *) sp;
319 /* Digest the auxiliary vector. */
320 for (i = 0; i < AT_COUNT; i++)
322 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
323 if (auxp->a_type < AT_COUNT)
324 aux_info[auxp->a_type] = auxp;
327 /* Initialize and relocate ourselves. */
328 assert(aux_info[AT_BASE] != NULL);
329 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
332 __progname = obj_rtld.path;
333 argv0 = argv[0] != NULL ? argv[0] : "(null)";
336 trust = (geteuid() == getuid()) && (getegid() == getgid());
338 ld_bind_now = _getenv_ld("LD_BIND_NOW");
340 ld_debug = _getenv_ld("LD_DEBUG");
341 ld_library_path = _getenv_ld("LD_LIBRARY_PATH");
342 ld_preload = (char *)_getenv_ld("LD_PRELOAD");
344 ld_tracing = _getenv_ld("LD_TRACE_LOADED_OBJECTS");
346 if (ld_debug != NULL && *ld_debug != '\0')
348 dbg("%s is initialized, base address = %p", __progname,
349 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
350 dbg("RTLD dynamic = %p", obj_rtld.dynamic);
351 dbg("RTLD pltgot = %p", obj_rtld.pltgot);
354 * If we are resident we can skip work that we have already done.
355 * Note that the stack is reset and there is no Elf_Auxinfo
356 * when running from a resident image, and the static globals setup
357 * between here and resident_skip will have already been setup.
363 * Load the main program, or process its program header if it is
366 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */
367 int fd = aux_info[AT_EXECFD]->a_un.a_val;
368 dbg("loading main program");
369 obj_main = map_object(fd, argv0, NULL);
371 if (obj_main == NULL)
373 } else { /* Main program already loaded. */
374 const Elf_Phdr *phdr;
378 dbg("processing main program's program header");
379 assert(aux_info[AT_PHDR] != NULL);
380 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr;
381 assert(aux_info[AT_PHNUM] != NULL);
382 phnum = aux_info[AT_PHNUM]->a_un.a_val;
383 assert(aux_info[AT_PHENT] != NULL);
384 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr));
385 assert(aux_info[AT_ENTRY] != NULL);
386 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr;
387 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL)
391 obj_main->path = xstrdup(argv0);
392 obj_main->mainprog = true;
395 * Get the actual dynamic linker pathname from the executable if
396 * possible. (It should always be possible.) That ensures that
397 * gdb will find the right dynamic linker even if a non-standard
400 if (obj_main->interp != NULL &&
401 strcmp(obj_main->interp, obj_rtld.path) != 0) {
403 obj_rtld.path = xstrdup(obj_main->interp);
404 __progname = obj_rtld.path;
407 digest_dynamic(obj_main, 0);
409 linkmap_add(obj_main);
410 linkmap_add(&obj_rtld);
412 /* Link the main program into the list of objects. */
413 *obj_tail = obj_main;
414 obj_tail = &obj_main->next;
416 obj_main->refcount++;
417 /* Make sure we don't call the main program's init and fini functions. */
418 obj_main->init = obj_main->fini = NULL;
420 /* Initialize a fake symbol for resolving undefined weak references. */
421 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
422 sym_zero.st_shndx = SHN_ABS;
424 dbg("loading LD_PRELOAD libraries");
425 if (load_preload_objects() == -1)
427 preload_tail = obj_tail;
429 dbg("loading needed objects");
430 if (load_needed_objects(obj_main) == -1)
433 /* Make a list of all objects loaded at startup. */
434 for (obj = obj_list; obj != NULL; obj = obj->next)
435 objlist_push_tail(&list_main, obj);
439 if (ld_tracing) { /* We're done */
440 trace_loaded_objects(obj_main);
444 if (ld_resident) /* XXX clean this up! */
447 if (getenv("LD_DUMP_REL_PRE") != NULL) {
448 dump_relocations(obj_main);
452 /* setup TLS for main thread */
453 dbg("initializing initial thread local storage");
454 STAILQ_FOREACH(entry, &list_main, link) {
456 * Allocate all the initial objects out of the static TLS
457 * block even if they didn't ask for it.
459 allocate_tls_offset(entry->obj);
462 tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA;
465 * Do not try to allocate the TLS here, let libc do it itself.
466 * (crt1 for the program will call _init_tls())
469 if (relocate_objects(obj_main,
470 ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1)
473 dbg("doing copy relocations");
474 if (do_copy_relocations(obj_main) == -1)
479 if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) {
480 if (exec_sys_unregister(-1) < 0) {
481 dbg("exec_sys_unregister failed %d\n", errno);
484 dbg("exec_sys_unregister success\n");
488 if (getenv("LD_DUMP_REL_POST") != NULL) {
489 dump_relocations(obj_main);
493 dbg("initializing key program variables");
494 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : "");
495 set_program_var("environ", env);
497 if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) {
498 extern void resident_start(void);
500 if (exec_sys_register(resident_start) < 0) {
501 dbg("exec_sys_register failed %d\n", errno);
504 dbg("exec_sys_register success\n");
508 dbg("initializing thread locks");
509 lockdflt_init(&lockinfo);
510 lockinfo.thelock = lockinfo.lock_create(lockinfo.context);
512 /* Make a list of init functions to call. */
513 objlist_init(&initlist);
514 initlist_add_objects(obj_list, preload_tail, &initlist);
516 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */
519 * Do NOT call the initlist here, give libc a chance to set up
520 * the initial TLS segment. crt1 will then call _rtld_call_init().
523 dbg("transferring control to program entry point = %p", obj_main->entry);
525 /* Return the exit procedure and the program entry point. */
526 *exit_proc = rtld_exit;
528 return (func_ptr_type) obj_main->entry;
532 * Call the initialization list for dynamically loaded libraries.
533 * (called from crt1.c).
536 _rtld_call_init(void)
538 objlist_call_init(&initlist);
540 objlist_clear(&initlist);
545 _rtld_bind(Obj_Entry *obj, Elf_Word reloff, void *stack)
549 const Obj_Entry *defobj;
556 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff);
558 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff);
560 where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
561 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
565 target = (Elf_Addr)(defobj->relocbase + def->st_value);
567 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"",
568 defobj->strtab + def->st_name, basename(obj->path),
569 (void *)target, basename(defobj->path));
573 * If we have a function call tracing hook, and the
574 * hook would like to keep tracing this one function,
575 * prevent the relocation so we will wind up here
576 * the next time again.
578 * We don't want to functrace calls from the functracer
579 * to avoid recursive loops.
581 if (rtld_functrace != NULL && obj != rtld_functrace_obj) {
582 if (rtld_functrace(obj->path,
584 defobj->strtab + def->st_name,
590 reloc_jmpslot(where, target);
595 * Error reporting function. Use it like printf. If formats the message
596 * into a buffer, and sets things up so that the next call to dlerror()
597 * will return the message.
600 _rtld_error(const char *fmt, ...)
602 static char buf[512];
606 vsnprintf(buf, sizeof buf, fmt, ap);
612 * Return a dynamically-allocated copy of the current error message, if any.
617 return error_message == NULL ? NULL : xstrdup(error_message);
621 * Restore the current error message from a copy which was previously saved
622 * by errmsg_save(). The copy is freed.
625 errmsg_restore(char *saved_msg)
627 if (saved_msg == NULL)
628 error_message = NULL;
630 _rtld_error("%s", saved_msg);
636 basename(const char *name)
638 const char *p = strrchr(name, '/');
639 return p != NULL ? p + 1 : name;
645 const char *msg = dlerror();
653 * Process a shared object's DYNAMIC section, and save the important
654 * information in its Obj_Entry structure.
657 digest_dynamic(Obj_Entry *obj, int early)
660 Needed_Entry **needed_tail = &obj->needed;
661 const Elf_Dyn *dyn_rpath = NULL;
662 int plttype = DT_REL;
664 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) {
665 switch (dynp->d_tag) {
668 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr);
672 obj->relsize = dynp->d_un.d_val;
676 assert(dynp->d_un.d_val == sizeof(Elf_Rel));
680 obj->pltrel = (const Elf_Rel *)
681 (obj->relocbase + dynp->d_un.d_ptr);
685 obj->pltrelsize = dynp->d_un.d_val;
689 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr);
693 obj->relasize = dynp->d_un.d_val;
697 assert(dynp->d_un.d_val == sizeof(Elf_Rela));
701 plttype = dynp->d_un.d_val;
702 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA);
706 obj->symtab = (const Elf_Sym *)
707 (obj->relocbase + dynp->d_un.d_ptr);
711 assert(dynp->d_un.d_val == sizeof(Elf_Sym));
715 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr);
719 obj->strsize = dynp->d_un.d_val;
724 const Elf_Hashelt *hashtab = (const Elf_Hashelt *)
725 (obj->relocbase + dynp->d_un.d_ptr);
726 obj->nbuckets = hashtab[0];
727 obj->nchains = hashtab[1];
728 obj->buckets = hashtab + 2;
729 obj->chains = obj->buckets + obj->nbuckets;
735 Needed_Entry *nep = NEW(Needed_Entry);
736 nep->name = dynp->d_un.d_val;
741 needed_tail = &nep->next;
746 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr);
754 obj->symbolic = true;
758 case DT_RUNPATH: /* XXX: process separately */
760 * We have to wait until later to process this, because we
761 * might not have gotten the address of the string table yet.
767 /* Not used by the dynamic linker. */
771 obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
775 obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr);
779 /* XXX - not implemented yet */
781 dbg("Filling in DT_DEBUG entry");
782 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug;
786 if (dynp->d_un.d_val & DF_ORIGIN) {
787 obj->origin_path = xmalloc(PATH_MAX);
788 if (rtld_dirname(obj->path, obj->origin_path) == -1)
791 if (dynp->d_un.d_val & DF_SYMBOLIC)
792 obj->symbolic = true;
793 if (dynp->d_un.d_val & DF_TEXTREL)
795 if (dynp->d_un.d_val & DF_BIND_NOW)
796 obj->bind_now = true;
797 if (dynp->d_un.d_val & DF_STATIC_TLS)
803 dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag);
810 if (plttype == DT_RELA) {
811 obj->pltrela = (const Elf_Rela *) obj->pltrel;
813 obj->pltrelasize = obj->pltrelsize;
817 if (dyn_rpath != NULL)
818 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val;
822 * Process a shared object's program header. This is used only for the
823 * main program, when the kernel has already loaded the main program
824 * into memory before calling the dynamic linker. It creates and
825 * returns an Obj_Entry structure.
828 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
831 const Elf_Phdr *phlimit = phdr + phnum;
836 for (ph = phdr; ph < phlimit; ph++) {
837 switch (ph->p_type) {
840 if ((const Elf_Phdr *)ph->p_vaddr != phdr) {
841 _rtld_error("%s: invalid PT_PHDR", path);
844 obj->phdr = (const Elf_Phdr *) ph->p_vaddr;
845 obj->phsize = ph->p_memsz;
849 obj->interp = (const char *) ph->p_vaddr;
853 if (nsegs == 0) { /* First load segment */
854 obj->vaddrbase = trunc_page(ph->p_vaddr);
855 obj->mapbase = (caddr_t) obj->vaddrbase;
856 obj->relocbase = obj->mapbase - obj->vaddrbase;
857 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
859 } else { /* Last load segment */
860 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) -
867 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr;
872 obj->tlssize = ph->p_memsz;
873 obj->tlsalign = ph->p_align;
874 obj->tlsinitsize = ph->p_filesz;
875 obj->tlsinit = (void*) ph->p_vaddr;
880 _rtld_error("%s: too few PT_LOAD segments", path);
889 dlcheck(void *handle)
893 for (obj = obj_list; obj != NULL; obj = obj->next)
894 if (obj == (Obj_Entry *) handle)
897 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) {
898 _rtld_error("Invalid shared object handle %p", handle);
905 * If the given object is already in the donelist, return true. Otherwise
906 * add the object to the list and return false.
909 donelist_check(DoneList *dlp, const Obj_Entry *obj)
913 for (i = 0; i < dlp->num_used; i++)
914 if (dlp->objs[i] == obj)
917 * Our donelist allocation should always be sufficient. But if
918 * our threads locking isn't working properly, more shared objects
919 * could have been loaded since we allocated the list. That should
920 * never happen, but we'll handle it properly just in case it does.
922 if (dlp->num_used < dlp->num_alloc)
923 dlp->objs[dlp->num_used++] = obj;
928 * Hash function for symbol table lookup. Don't even think about changing
929 * this. It is specified by the System V ABI.
932 elf_hash(const char *name)
934 const unsigned char *p = (const unsigned char *) name;
940 if ((g = h & 0xf0000000) != 0)
948 * Find the library with the given name, and return its full pathname.
949 * The returned string is dynamically allocated. Generates an error
950 * message and returns NULL if the library cannot be found.
952 * If the second argument is non-NULL, then it refers to an already-
953 * loaded shared object, whose library search path will be searched.
955 * The search order is:
957 * rpath in the referencing file
962 find_library(const char *name, const Obj_Entry *refobj)
966 if (strchr(name, '/') != NULL) { /* Hard coded pathname */
967 if (name[0] != '/' && !trust) {
968 _rtld_error("Absolute pathname required for shared object \"%s\"",
972 return xstrdup(name);
975 dbg(" Searching for \"%s\"", name);
977 if ((pathname = search_library_path(name, ld_library_path)) != NULL ||
979 (pathname = search_library_path(name, refobj->rpath)) != NULL) ||
980 (pathname = search_library_path(name, gethints())) != NULL ||
981 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL)
984 if(refobj != NULL && refobj->path != NULL) {
985 _rtld_error("Shared object \"%s\" not found, required by \"%s\"",
986 name, basename(refobj->path));
988 _rtld_error("Shared object \"%s\" not found", name);
994 * Given a symbol number in a referencing object, find the corresponding
995 * definition of the symbol. Returns a pointer to the symbol, or NULL if
996 * no definition was found. Returns a pointer to the Obj_Entry of the
997 * defining object via the reference parameter DEFOBJ_OUT.
1000 find_symdef(unsigned long symnum, const Obj_Entry *refobj,
1001 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache)
1005 const Obj_Entry *defobj;
1010 * If we have already found this symbol, get the information from
1013 if (symnum >= refobj->nchains)
1014 return NULL; /* Bad object */
1015 if (cache != NULL && cache[symnum].sym != NULL) {
1016 *defobj_out = cache[symnum].obj;
1017 return cache[symnum].sym;
1020 ref = refobj->symtab + symnum;
1021 name = refobj->strtab + ref->st_name;
1025 * We don't have to do a full scale lookup if the symbol is local.
1026 * We know it will bind to the instance in this load module; to
1027 * which we already have a pointer (ie ref). By not doing a lookup,
1028 * we not only improve performance, but it also avoids unresolvable
1029 * symbols when local symbols are not in the hash table.
1031 * This might occur for TLS module relocations, which simply use
1034 if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) {
1035 if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) {
1036 _rtld_error("%s: Bogus symbol table entry %lu", refobj->path,
1039 hash = elf_hash(name);
1040 def = symlook_default(name, hash, refobj, &defobj, in_plt);
1047 * If we found no definition and the reference is weak, treat the
1048 * symbol as having the value zero.
1050 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) {
1056 *defobj_out = defobj;
1057 /* Record the information in the cache to avoid subsequent lookups. */
1058 if (cache != NULL) {
1059 cache[symnum].sym = def;
1060 cache[symnum].obj = defobj;
1063 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
1068 * Return the search path from the ldconfig hints file, reading it if
1069 * necessary. Returns NULL if there are problems with the hints file,
1070 * or if the search path there is empty.
1077 if (hints == NULL) {
1079 struct elfhints_hdr hdr;
1082 /* Keep from trying again in case the hints file is bad. */
1085 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1)
1087 if (read(fd, &hdr, sizeof hdr) != sizeof hdr ||
1088 hdr.magic != ELFHINTS_MAGIC ||
1093 p = xmalloc(hdr.dirlistlen + 1);
1094 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 ||
1095 read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) {
1103 return hints[0] != '\0' ? hints : NULL;
1107 init_dag(Obj_Entry *root)
1111 donelist_init(&donelist);
1112 init_dag1(root, root, &donelist);
1116 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp)
1118 const Needed_Entry *needed;
1120 if (donelist_check(dlp, obj))
1122 objlist_push_tail(&obj->dldags, root);
1123 objlist_push_tail(&root->dagmembers, obj);
1124 for (needed = obj->needed; needed != NULL; needed = needed->next)
1125 if (needed->obj != NULL)
1126 init_dag1(root, needed->obj, dlp);
1130 * Initialize the dynamic linker. The argument is the address at which
1131 * the dynamic linker has been mapped into memory. The primary task of
1132 * this function is to relocate the dynamic linker.
1135 init_rtld(caddr_t mapbase)
1137 Obj_Entry objtmp; /* Temporary rtld object */
1140 * Conjure up an Obj_Entry structure for the dynamic linker.
1142 * The "path" member can't be initialized yet because string constatns
1143 * cannot yet be acessed. Below we will set it correctly.
1147 objtmp.mapbase = mapbase;
1149 objtmp.relocbase = mapbase;
1151 if (&_DYNAMIC != 0) {
1152 objtmp.dynamic = rtld_dynamic(&objtmp);
1153 digest_dynamic(&objtmp, 1);
1154 assert(objtmp.needed == NULL);
1155 assert(!objtmp.textrel);
1158 * Temporarily put the dynamic linker entry into the object list, so
1159 * that symbols can be found.
1162 relocate_objects(&objtmp, true, &objtmp);
1165 /* Initialize the object list. */
1166 obj_tail = &obj_list;
1168 /* Now that non-local variables can be accesses, copy out obj_rtld. */
1169 memcpy(&obj_rtld, &objtmp, sizeof(obj_rtld));
1171 /* Replace the path with a dynamically allocated copy. */
1172 obj_rtld.path = xstrdup(PATH_RTLD);
1174 r_debug.r_brk = r_debug_state;
1175 r_debug.r_state = RT_CONSISTENT;
1179 * Add the init functions from a needed object list (and its recursive
1180 * needed objects) to "list". This is not used directly; it is a helper
1181 * function for initlist_add_objects(). The write lock must be held
1182 * when this function is called.
1185 initlist_add_neededs(Needed_Entry *needed, Objlist *list)
1187 /* Recursively process the successor needed objects. */
1188 if (needed->next != NULL)
1189 initlist_add_neededs(needed->next, list);
1191 /* Process the current needed object. */
1192 if (needed->obj != NULL)
1193 initlist_add_objects(needed->obj, &needed->obj->next, list);
1197 * Scan all of the DAGs rooted in the range of objects from "obj" to
1198 * "tail" and add their init functions to "list". This recurses over
1199 * the DAGs and ensure the proper init ordering such that each object's
1200 * needed libraries are initialized before the object itself. At the
1201 * same time, this function adds the objects to the global finalization
1202 * list "list_fini" in the opposite order. The write lock must be
1203 * held when this function is called.
1206 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list)
1210 obj->init_done = true;
1212 /* Recursively process the successor objects. */
1213 if (&obj->next != tail)
1214 initlist_add_objects(obj->next, tail, list);
1216 /* Recursively process the needed objects. */
1217 if (obj->needed != NULL)
1218 initlist_add_neededs(obj->needed, list);
1220 /* Add the object to the init list. */
1221 if (obj->init != NULL)
1222 objlist_push_tail(list, obj);
1224 /* Add the object to the global fini list in the reverse order. */
1225 if (obj->fini != NULL)
1226 objlist_push_head(&list_fini, obj);
1230 is_exported(const Elf_Sym *def)
1233 const func_ptr_type *p;
1235 value = (Elf_Addr)(obj_rtld.relocbase + def->st_value);
1236 for (p = exports; *p != NULL; p++) {
1237 if ((Elf_Addr)(*p) == value)
1244 * Given a shared object, traverse its list of needed objects, and load
1245 * each of them. Returns 0 on success. Generates an error message and
1246 * returns -1 on failure.
1249 load_needed_objects(Obj_Entry *first)
1253 for (obj = first; obj != NULL; obj = obj->next) {
1254 Needed_Entry *needed;
1256 for (needed = obj->needed; needed != NULL; needed = needed->next) {
1257 const char *name = obj->strtab + needed->name;
1258 char *path = find_library(name, obj);
1261 if (path == NULL && !ld_tracing)
1265 needed->obj = load_object(path);
1266 if (needed->obj == NULL && !ld_tracing)
1267 return -1; /* XXX - cleanup */
1275 #define RTLD_FUNCTRACE "_rtld_functrace"
1278 load_preload_objects(void)
1280 char *p = ld_preload;
1281 static const char delim[] = " \t:;";
1286 p += strspn(p, delim);
1287 while (*p != '\0') {
1288 size_t len = strcspn(p, delim);
1296 if ((path = find_library(p, NULL)) == NULL)
1298 obj = load_object(path);
1300 return -1; /* XXX - cleanup */
1303 p += strspn(p, delim);
1305 /* Check for the magic tracing function */
1306 sym = symlook_obj(RTLD_FUNCTRACE, elf_hash(RTLD_FUNCTRACE), obj, true);
1308 rtld_functrace = (void *)(obj->relocbase + sym->st_value);
1309 rtld_functrace_obj = obj;
1316 * Returns a pointer to the Obj_Entry for the object with the given path.
1317 * Returns NULL if no matching object was found.
1320 find_object(const char *path)
1324 for (obj = obj_list->next; obj != NULL; obj = obj->next) {
1325 if (strcmp(obj->path, path) == 0)
1332 * Returns a pointer to the Obj_Entry for the object matching device and
1333 * inode of the given path. If no matching object was found, the descriptor
1334 * is returned in fd.
1335 * Returns with obj == NULL && fd == -1 on error.
1338 find_object2(const char *path, int *fd, struct stat *sb)
1342 if ((*fd = open(path, O_RDONLY)) == -1) {
1343 _rtld_error("Cannot open \"%s\"", path);
1347 if (fstat(*fd, sb) == -1) {
1348 _rtld_error("Cannot fstat \"%s\"", path);
1354 for (obj = obj_list->next; obj != NULL; obj = obj->next) {
1355 if (obj->ino == sb->st_ino && obj->dev == sb->st_dev) {
1365 * Load a shared object into memory, if it is not already loaded. The
1366 * argument must be a string allocated on the heap. This function assumes
1367 * responsibility for freeing it when necessary.
1369 * Returns a pointer to the Obj_Entry for the object. Returns NULL
1373 load_object(char *path)
1379 obj = find_object(path);
1386 obj = find_object2(path, &fd, &sb);
1391 } else if (fd == -1) {
1396 dbg("loading \"%s\"", path);
1397 obj = map_object(fd, path, &sb);
1405 digest_dynamic(obj, 0);
1408 obj_tail = &obj->next;
1410 linkmap_add(obj); /* for GDB & dlinfo() */
1412 dbg(" %p .. %p: %s", obj->mapbase, obj->mapbase + obj->mapsize - 1,
1415 dbg(" WARNING: %s has impure text", obj->path);
1422 * Check for locking violations and die if one is found.
1429 rcount = lockinfo.rcount;
1430 wcount = lockinfo.wcount;
1431 assert(rcount >= 0);
1432 assert(wcount >= 0);
1433 if (wcount > 1 || (wcount != 0 && rcount != 0)) {
1434 _rtld_error("Application locking error: %d readers and %d writers"
1435 " in dynamic linker. See DLLOCKINIT(3) in manual pages.",
1442 obj_from_addr(const void *addr)
1446 for (obj = obj_list; obj != NULL; obj = obj->next) {
1447 if (addr < (void *) obj->mapbase)
1449 if (addr < (void *) (obj->mapbase + obj->mapsize))
1456 * Call the finalization functions for each of the objects in "list"
1457 * which are unreferenced. All of the objects are expected to have
1458 * non-NULL fini functions.
1461 objlist_call_fini(Objlist *list)
1467 * Preserve the current error message since a fini function might
1468 * call into the dynamic linker and overwrite it.
1470 saved_msg = errmsg_save();
1471 STAILQ_FOREACH(elm, list, link) {
1472 if (elm->obj->refcount == 0) {
1473 dbg("calling fini function for %s", elm->obj->path);
1474 (*elm->obj->fini)();
1477 errmsg_restore(saved_msg);
1481 * Call the initialization functions for each of the objects in
1482 * "list". All of the objects are expected to have non-NULL init
1486 objlist_call_init(Objlist *list)
1492 * Preserve the current error message since an init function might
1493 * call into the dynamic linker and overwrite it.
1495 saved_msg = errmsg_save();
1496 STAILQ_FOREACH(elm, list, link) {
1497 dbg("calling init function for %s", elm->obj->path);
1498 (*elm->obj->init)();
1500 errmsg_restore(saved_msg);
1504 objlist_clear(Objlist *list)
1508 while (!STAILQ_EMPTY(list)) {
1509 elm = STAILQ_FIRST(list);
1510 STAILQ_REMOVE_HEAD(list, link);
1515 static Objlist_Entry *
1516 objlist_find(Objlist *list, const Obj_Entry *obj)
1520 STAILQ_FOREACH(elm, list, link)
1521 if (elm->obj == obj)
1527 objlist_init(Objlist *list)
1533 objlist_push_head(Objlist *list, Obj_Entry *obj)
1537 elm = NEW(Objlist_Entry);
1539 STAILQ_INSERT_HEAD(list, elm, link);
1543 objlist_push_tail(Objlist *list, Obj_Entry *obj)
1547 elm = NEW(Objlist_Entry);
1549 STAILQ_INSERT_TAIL(list, elm, link);
1553 objlist_remove(Objlist *list, Obj_Entry *obj)
1557 if ((elm = objlist_find(list, obj)) != NULL) {
1558 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link);
1564 * Remove all of the unreferenced objects from "list".
1567 objlist_remove_unref(Objlist *list)
1572 STAILQ_INIT(&newlist);
1573 while (!STAILQ_EMPTY(list)) {
1574 elm = STAILQ_FIRST(list);
1575 STAILQ_REMOVE_HEAD(list, link);
1576 if (elm->obj->refcount == 0)
1579 STAILQ_INSERT_TAIL(&newlist, elm, link);
1585 * Relocate newly-loaded shared objects. The argument is a pointer to
1586 * the Obj_Entry for the first such object. All objects from the first
1587 * to the end of the list of objects are relocated. Returns 0 on success,
1591 relocate_objects(Obj_Entry *first, bool bind_now, Obj_Entry *rtldobj)
1595 for (obj = first; obj != NULL; obj = obj->next) {
1597 dbg("relocating \"%s\"", obj->path);
1598 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL ||
1599 obj->symtab == NULL || obj->strtab == NULL) {
1600 _rtld_error("%s: Shared object has no run-time symbol table",
1606 /* There are relocations to the write-protected text segment. */
1607 if (mprotect(obj->mapbase, obj->textsize,
1608 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
1609 _rtld_error("%s: Cannot write-enable text segment: %s",
1610 obj->path, strerror(errno));
1615 /* Process the non-PLT relocations. */
1616 if (reloc_non_plt(obj, rtldobj))
1620 * Reprotect the text segment. Make sure it is included in the
1621 * core dump since we modified it. This unfortunately causes the
1622 * entire text segment to core-out but we don't have much of a
1623 * choice. We could try to only reenable core dumps on pages
1624 * in which relocations occured but that is likely most of the text
1625 * pages anyway, and even that would not work because the rest of
1626 * the text pages would wind up as a read-only OBJT_DEFAULT object
1627 * (created due to our modifications) backed by the original OBJT_VNODE
1628 * object, and the ELF coredump code is currently only able to dump
1629 * vnode records for pure vnode-backed mappings, not vnode backings
1630 * to memory objects.
1633 madvise(obj->mapbase, obj->textsize, MADV_CORE);
1634 if (mprotect(obj->mapbase, obj->textsize,
1635 PROT_READ|PROT_EXEC) == -1) {
1636 _rtld_error("%s: Cannot write-protect text segment: %s",
1637 obj->path, strerror(errno));
1642 /* Process the PLT relocations. */
1643 if (reloc_plt(obj) == -1)
1645 /* Relocate the jump slots if we are doing immediate binding. */
1646 if (obj->bind_now || bind_now)
1647 if (reloc_jmpslots(obj) == -1)
1652 * Set up the magic number and version in the Obj_Entry. These
1653 * were checked in the crt1.o from the original ElfKit, so we
1654 * set them for backward compatibility.
1656 obj->magic = RTLD_MAGIC;
1657 obj->version = RTLD_VERSION;
1659 /* Set the special PLT or GOT entries. */
1667 * Cleanup procedure. It will be called (by the atexit mechanism) just
1668 * before the process exits.
1676 /* Clear all the reference counts so the fini functions will be called. */
1677 for (obj = obj_list; obj != NULL; obj = obj->next)
1679 objlist_call_fini(&list_fini);
1680 /* No need to remove the items from the list, since we are exiting. */
1684 path_enumerate(const char *path, path_enum_proc callback, void *arg)
1689 path += strspn(path, ":;");
1690 while (*path != '\0') {
1694 len = strcspn(path, ":;");
1695 res = callback(path, len, arg);
1701 path += strspn(path, ":;");
1707 struct try_library_args {
1715 try_library_path(const char *dir, size_t dirlen, void *param)
1717 struct try_library_args *arg;
1720 if (*dir == '/' || trust) {
1723 if (dirlen + 1 + arg->namelen + 1 > arg->buflen)
1726 pathname = arg->buffer;
1727 strncpy(pathname, dir, dirlen);
1728 pathname[dirlen] = '/';
1729 strcpy(pathname + dirlen + 1, arg->name);
1731 dbg(" Trying \"%s\"", pathname);
1732 if (access(pathname, F_OK) == 0) { /* We found it */
1733 pathname = xmalloc(dirlen + 1 + arg->namelen + 1);
1734 strcpy(pathname, arg->buffer);
1742 search_library_path(const char *name, const char *path)
1745 struct try_library_args arg;
1751 arg.namelen = strlen(name);
1752 arg.buffer = xmalloc(PATH_MAX);
1753 arg.buflen = PATH_MAX;
1755 p = path_enumerate(path, try_library_path, &arg);
1763 dlclose(void *handle)
1768 root = dlcheck(handle);
1774 /* Unreference the object and its dependencies. */
1775 root->dl_refcount--;
1778 if (root->refcount == 0) {
1780 * The object is no longer referenced, so we must unload it.
1781 * First, call the fini functions with no locks held.
1784 objlist_call_fini(&list_fini);
1786 objlist_remove_unref(&list_fini);
1788 /* Finish cleaning up the newly-unreferenced objects. */
1789 GDB_STATE(RT_DELETE,&root->linkmap);
1790 unload_object(root);
1791 GDB_STATE(RT_CONSISTENT,NULL);
1800 char *msg = error_message;
1801 error_message = NULL;
1806 dlopen(const char *name, int mode)
1808 Obj_Entry **old_obj_tail;
1813 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1";
1814 if (ld_tracing != NULL)
1815 environ = (char **)*get_program_var_addr("environ");
1817 objlist_init(&initlist);
1820 GDB_STATE(RT_ADD,NULL);
1822 old_obj_tail = obj_tail;
1828 char *path = find_library(name, obj_main);
1830 obj = load_object(path);
1835 if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL)
1836 objlist_push_tail(&list_global, obj);
1837 mode &= RTLD_MODEMASK;
1838 if (*old_obj_tail != NULL) { /* We loaded something new. */
1839 assert(*old_obj_tail == obj);
1841 result = load_needed_objects(obj);
1842 if (result != -1 && ld_tracing)
1846 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW,
1847 &obj_rtld)) == -1) {
1850 if (obj->refcount == 0)
1854 /* Make list of init functions to call. */
1855 initlist_add_objects(obj, &obj->next, &initlist);
1857 } else if (ld_tracing)
1861 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL);
1863 /* Call the init functions with no locks held. */
1865 objlist_call_init(&initlist);
1867 objlist_clear(&initlist);
1871 trace_loaded_objects(obj);
1877 dlsym(void *handle, const char *name)
1879 const Obj_Entry *obj;
1882 const Obj_Entry *defobj;
1884 hash = elf_hash(name);
1889 if (handle == NULL || handle == RTLD_NEXT ||
1890 handle == RTLD_DEFAULT || handle == RTLD_SELF) {
1893 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1894 if ((obj = obj_from_addr(retaddr)) == NULL) {
1895 _rtld_error("Cannot determine caller's shared object");
1899 if (handle == NULL) { /* Just the caller's shared object. */
1900 def = symlook_obj(name, hash, obj, true);
1902 } else if (handle == RTLD_NEXT || /* Objects after caller's */
1903 handle == RTLD_SELF) { /* ... caller included */
1904 if (handle == RTLD_NEXT)
1906 for (; obj != NULL; obj = obj->next) {
1907 if ((def = symlook_obj(name, hash, obj, true)) != NULL) {
1913 assert(handle == RTLD_DEFAULT);
1914 def = symlook_default(name, hash, obj, &defobj, true);
1919 if ((obj = dlcheck(handle)) == NULL) {
1924 donelist_init(&donelist);
1925 if (obj->mainprog) {
1926 /* Search main program and all libraries loaded by it. */
1927 def = symlook_list(name, hash, &list_main, &defobj, true,
1932 /* Search the given object and its needed objects. */
1934 fake.obj = (Obj_Entry *)obj;
1936 def = symlook_needed(name, hash, &fake, &defobj, true,
1943 return defobj->relocbase + def->st_value;
1946 _rtld_error("Undefined symbol \"%s\"", name);
1952 dladdr(const void *addr, Dl_info *info)
1954 const Obj_Entry *obj;
1957 unsigned long symoffset;
1960 obj = obj_from_addr(addr);
1962 _rtld_error("No shared object contains address");
1966 info->dli_fname = obj->path;
1967 info->dli_fbase = obj->mapbase;
1968 info->dli_saddr = (void *)0;
1969 info->dli_sname = NULL;
1972 * Walk the symbol list looking for the symbol whose address is
1973 * closest to the address sent in.
1975 for (symoffset = 0; symoffset < obj->nchains; symoffset++) {
1976 def = obj->symtab + symoffset;
1979 * For skip the symbol if st_shndx is either SHN_UNDEF or
1982 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON)
1986 * If the symbol is greater than the specified address, or if it
1987 * is further away from addr than the current nearest symbol,
1990 symbol_addr = obj->relocbase + def->st_value;
1991 if (symbol_addr > addr || symbol_addr < info->dli_saddr)
1994 /* Update our idea of the nearest symbol. */
1995 info->dli_sname = obj->strtab + def->st_name;
1996 info->dli_saddr = symbol_addr;
1999 if (info->dli_saddr == addr)
2007 dlinfo(void *handle, int request, void *p)
2009 const Obj_Entry *obj;
2014 if (handle == NULL || handle == RTLD_SELF) {
2017 retaddr = __builtin_return_address(0); /* __GNUC__ only */
2018 if ((obj = obj_from_addr(retaddr)) == NULL)
2019 _rtld_error("Cannot determine caller's shared object");
2021 obj = dlcheck(handle);
2030 case RTLD_DI_LINKMAP:
2031 *((struct link_map const **)p) = &obj->linkmap;
2033 case RTLD_DI_ORIGIN:
2034 error = rtld_dirname(obj->path, p);
2037 case RTLD_DI_SERINFOSIZE:
2038 case RTLD_DI_SERINFO:
2039 error = do_search_info(obj, request, (struct dl_serinfo *)p);
2043 _rtld_error("Invalid request %d passed to dlinfo()", request);
2052 struct fill_search_info_args {
2055 Dl_serinfo *serinfo;
2056 Dl_serpath *serpath;
2061 fill_search_info(const char *dir, size_t dirlen, void *param)
2063 struct fill_search_info_args *arg;
2067 if (arg->request == RTLD_DI_SERINFOSIZE) {
2068 arg->serinfo->dls_cnt ++;
2069 arg->serinfo->dls_size += dirlen + 1;
2071 struct dl_serpath *s_entry;
2073 s_entry = arg->serpath;
2074 s_entry->dls_name = arg->strspace;
2075 s_entry->dls_flags = arg->flags;
2077 strncpy(arg->strspace, dir, dirlen);
2078 arg->strspace[dirlen] = '\0';
2080 arg->strspace += dirlen + 1;
2088 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info)
2090 struct dl_serinfo _info;
2091 struct fill_search_info_args args;
2093 args.request = RTLD_DI_SERINFOSIZE;
2094 args.serinfo = &_info;
2096 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath);
2099 path_enumerate(ld_library_path, fill_search_info, &args);
2100 path_enumerate(obj->rpath, fill_search_info, &args);
2101 path_enumerate(gethints(), fill_search_info, &args);
2102 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args);
2105 if (request == RTLD_DI_SERINFOSIZE) {
2106 info->dls_size = _info.dls_size;
2107 info->dls_cnt = _info.dls_cnt;
2111 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) {
2112 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()");
2116 args.request = RTLD_DI_SERINFO;
2117 args.serinfo = info;
2118 args.serpath = &info->dls_serpath[0];
2119 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt];
2121 args.flags = LA_SER_LIBPATH;
2122 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL)
2125 args.flags = LA_SER_RUNPATH;
2126 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL)
2129 args.flags = LA_SER_CONFIG;
2130 if (path_enumerate(gethints(), fill_search_info, &args) != NULL)
2133 args.flags = LA_SER_DEFAULT;
2134 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL)
2140 rtld_dirname(const char *path, char *bname)
2144 /* Empty or NULL string gets treated as "." */
2145 if (path == NULL || *path == '\0') {
2151 /* Strip trailing slashes */
2152 endp = path + strlen(path) - 1;
2153 while (endp > path && *endp == '/')
2156 /* Find the start of the dir */
2157 while (endp > path && *endp != '/')
2160 /* Either the dir is "/" or there are no slashes */
2162 bname[0] = *endp == '/' ? '/' : '.';
2168 } while (endp > path && *endp == '/');
2171 if (endp - path + 2 > PATH_MAX)
2173 _rtld_error("Filename is too long: %s", path);
2177 strncpy(bname, path, endp - path + 1);
2178 bname[endp - path + 1] = '\0';
2183 linkmap_add(Obj_Entry *obj)
2185 struct link_map *l = &obj->linkmap;
2186 struct link_map *prev;
2188 obj->linkmap.l_name = obj->path;
2189 obj->linkmap.l_addr = obj->mapbase;
2190 obj->linkmap.l_ld = obj->dynamic;
2192 /* GDB needs load offset on MIPS to use the symbols */
2193 obj->linkmap.l_offs = obj->relocbase;
2196 if (r_debug.r_map == NULL) {
2202 * Scan to the end of the list, but not past the entry for the
2203 * dynamic linker, which we want to keep at the very end.
2205 for (prev = r_debug.r_map;
2206 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap;
2207 prev = prev->l_next)
2210 /* Link in the new entry. */
2212 l->l_next = prev->l_next;
2213 if (l->l_next != NULL)
2214 l->l_next->l_prev = l;
2219 linkmap_delete(Obj_Entry *obj)
2221 struct link_map *l = &obj->linkmap;
2223 if (l->l_prev == NULL) {
2224 if ((r_debug.r_map = l->l_next) != NULL)
2225 l->l_next->l_prev = NULL;
2229 if ((l->l_prev->l_next = l->l_next) != NULL)
2230 l->l_next->l_prev = l->l_prev;
2234 * Function for the debugger to set a breakpoint on to gain control.
2236 * The two parameters allow the debugger to easily find and determine
2237 * what the runtime loader is doing and to whom it is doing it.
2239 * When the loadhook trap is hit (r_debug_state, set at program
2240 * initialization), the arguments can be found on the stack:
2242 * +8 struct link_map *m
2243 * +4 struct r_debug *rd
2247 r_debug_state(struct r_debug* rd, struct link_map *m)
2252 * Get address of the pointer variable in the main program.
2254 static const void **
2255 get_program_var_addr(const char *name)
2257 const Obj_Entry *obj;
2260 hash = elf_hash(name);
2261 for (obj = obj_main; obj != NULL; obj = obj->next) {
2264 if ((def = symlook_obj(name, hash, obj, false)) != NULL) {
2267 addr = (const void **)(obj->relocbase + def->st_value);
2275 * Set a pointer variable in the main program to the given value. This
2276 * is used to set key variables such as "environ" before any of the
2277 * init functions are called.
2280 set_program_var(const char *name, const void *value)
2284 if ((addr = get_program_var_addr(name)) != NULL) {
2285 dbg("\"%s\": *%p <-- %p", name, addr, value);
2291 * This is a special version of getenv which is far more efficient
2292 * at finding LD_ environment vars.
2296 _getenv_ld(const char *id)
2300 int idlen = strlen(id);
2302 if (ld_index == LD_ARY_CACHE)
2304 if (ld_index == 0) {
2305 for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) {
2306 if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_')
2313 for (i = ld_index - 1; i >= 0; --i) {
2314 if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=')
2315 return(ld_ary[i] + idlen + 1);
2321 * Given a symbol name in a referencing object, find the corresponding
2322 * definition of the symbol. Returns a pointer to the symbol, or NULL if
2323 * no definition was found. Returns a pointer to the Obj_Entry of the
2324 * defining object via the reference parameter DEFOBJ_OUT.
2326 static const Elf_Sym *
2327 symlook_default(const char *name, unsigned long hash,
2328 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt)
2332 const Elf_Sym *symp;
2333 const Obj_Entry *obj;
2334 const Obj_Entry *defobj;
2335 const Objlist_Entry *elm;
2338 donelist_init(&donelist);
2340 /* Look first in the referencing object if linked symbolically. */
2341 if (refobj->symbolic && !donelist_check(&donelist, refobj)) {
2342 symp = symlook_obj(name, hash, refobj, in_plt);
2349 /* Search all objects loaded at program start up. */
2350 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2351 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist);
2353 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2359 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */
2360 STAILQ_FOREACH(elm, &list_global, link) {
2361 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2363 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2366 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2372 /* Search all dlopened DAGs containing the referencing object. */
2373 STAILQ_FOREACH(elm, &refobj->dldags, link) {
2374 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2376 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2379 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2386 * Search the dynamic linker itself, and possibly resolve the
2387 * symbol from there. This is how the application links to
2388 * dynamic linker services such as dlopen. Only the values listed
2389 * in the "exports" array can be resolved from the dynamic linker.
2391 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2392 symp = symlook_obj(name, hash, &obj_rtld, in_plt);
2393 if (symp != NULL && is_exported(symp)) {
2400 *defobj_out = defobj;
2404 static const Elf_Sym *
2405 symlook_list(const char *name, unsigned long hash, const Objlist *objlist,
2406 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)
2408 const Elf_Sym *symp;
2410 const Obj_Entry *defobj;
2411 const Objlist_Entry *elm;
2415 STAILQ_FOREACH(elm, objlist, link) {
2416 if (donelist_check(dlp, elm->obj))
2418 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) {
2419 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) {
2422 if (ELF_ST_BIND(def->st_info) != STB_WEAK)
2428 *defobj_out = defobj;
2433 * Search the symbol table of a shared object and all objects needed
2434 * by it for a symbol of the given name. Search order is
2435 * breadth-first. Returns a pointer to the symbol, or NULL if no
2436 * definition was found.
2438 static const Elf_Sym *
2439 symlook_needed(const char *name, unsigned long hash, const Needed_Entry *needed,
2440 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)
2442 const Elf_Sym *def, *def_w;
2443 const Needed_Entry *n;
2444 const Obj_Entry *obj, *defobj, *defobj1;
2448 for (n = needed; n != NULL; n = n->next) {
2449 if ((obj = n->obj) == NULL ||
2450 donelist_check(dlp, obj) ||
2451 (def = symlook_obj(name, hash, obj, in_plt)) == NULL)
2454 if (ELF_ST_BIND(def->st_info) != STB_WEAK) {
2455 *defobj_out = defobj;
2460 * There we come when either symbol definition is not found in
2461 * directly needed objects, or found symbol is weak.
2463 for (n = needed; n != NULL; n = n->next) {
2464 if ((obj = n->obj) == NULL)
2466 def_w = symlook_needed(name, hash, obj->needed, &defobj1,
2470 if (def == NULL || ELF_ST_BIND(def_w->st_info) != STB_WEAK) {
2474 if (ELF_ST_BIND(def_w->st_info) != STB_WEAK)
2478 *defobj_out = defobj;
2483 * Search the symbol table of a single shared object for a symbol of
2484 * the given name. Returns a pointer to the symbol, or NULL if no
2485 * definition was found.
2487 * The symbol's hash value is passed in for efficiency reasons; that
2488 * eliminates many recomputations of the hash value.
2491 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj,
2494 if (obj->buckets != NULL) {
2495 unsigned long symnum = obj->buckets[hash % obj->nbuckets];
2497 while (symnum != STN_UNDEF) {
2498 const Elf_Sym *symp;
2501 if (symnum >= obj->nchains)
2502 return NULL; /* Bad object */
2503 symp = obj->symtab + symnum;
2504 strp = obj->strtab + symp->st_name;
2506 if (name[0] == strp[0] && strcmp(name, strp) == 0)
2507 return symp->st_shndx != SHN_UNDEF ||
2508 (!in_plt && symp->st_value != 0 &&
2509 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL;
2511 symnum = obj->chains[symnum];
2518 trace_loaded_objects(Obj_Entry *obj)
2520 const char *fmt1, *fmt2, *fmt, *main_local;
2523 if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL)
2526 if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL)
2527 fmt1 = "\t%o => %p (%x)\n";
2529 if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL)
2530 fmt2 = "\t%o (%x)\n";
2532 for (; obj; obj = obj->next) {
2533 Needed_Entry *needed;
2537 for (needed = obj->needed; needed; needed = needed->next) {
2538 if (needed->obj != NULL) {
2539 if (needed->obj->traced)
2541 needed->obj->traced = true;
2542 path = needed->obj->path;
2546 name = (char *)obj->strtab + needed->name;
2547 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */
2549 fmt = is_lib ? fmt1 : fmt2;
2550 while ((c = *fmt++) != '\0') {
2576 printf("%s", main_local);
2579 printf("%s", obj_main->path);
2586 printf("%d", sodp->sod_major);
2589 printf("%d", sodp->sod_minor);
2596 printf("%p", needed->obj ? needed->obj->mapbase : 0);
2608 * Unload a dlopened object and its dependencies from memory and from
2609 * our data structures. It is assumed that the DAG rooted in the
2610 * object has already been unreferenced, and that the object has a
2611 * reference count of 0.
2614 unload_object(Obj_Entry *root)
2619 assert(root->refcount == 0);
2622 * Pass over the DAG removing unreferenced objects from
2623 * appropriate lists.
2625 unlink_object(root);
2627 /* Unmap all objects that are no longer referenced. */
2628 linkp = &obj_list->next;
2629 while ((obj = *linkp) != NULL) {
2630 if (obj->refcount == 0) {
2631 dbg("unloading \"%s\"", obj->path);
2632 munmap(obj->mapbase, obj->mapsize);
2633 linkmap_delete(obj);
2644 unlink_object(Obj_Entry *root)
2646 const Needed_Entry *needed;
2649 if (root->refcount == 0) {
2650 /* Remove the object from the RTLD_GLOBAL list. */
2651 objlist_remove(&list_global, root);
2653 /* Remove the object from all objects' DAG lists. */
2654 STAILQ_FOREACH(elm, &root->dagmembers , link)
2655 objlist_remove(&elm->obj->dldags, root);
2658 for (needed = root->needed; needed != NULL; needed = needed->next)
2659 if (needed->obj != NULL)
2660 unlink_object(needed->obj);
2664 unref_dag(Obj_Entry *root)
2666 const Needed_Entry *needed;
2668 if (root->refcount == 0)
2671 if (root->refcount == 0)
2672 for (needed = root->needed; needed != NULL; needed = needed->next)
2673 if (needed->obj != NULL)
2674 unref_dag(needed->obj);
2678 * Common code for MD __tls_get_addr().
2681 tls_get_addr_common(void **dtvp, int index, size_t offset)
2683 Elf_Addr* dtv = *dtvp;
2685 /* Check dtv generation in case new modules have arrived */
2686 if (dtv[0] != tls_dtv_generation) {
2692 newdtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr));
2694 if (to_copy > tls_max_index)
2695 to_copy = tls_max_index;
2696 memcpy(&newdtv[2], &dtv[2], to_copy * sizeof(Elf_Addr));
2697 newdtv[0] = tls_dtv_generation;
2698 newdtv[1] = tls_max_index;
2705 /* Dynamically allocate module TLS if necessary */
2706 if (!dtv[index + 1]) {
2708 * here we should avoid to be re-entered by signal handler
2709 * code, I assume wlock_acquire will masked all signals,
2710 * otherwise there is race and dead lock thread itself.
2713 if (!dtv[index + 1])
2714 dtv[index + 1] = (Elf_Addr)allocate_module_tls(index);
2718 return (void*) (dtv[index + 1] + offset);
2721 #if defined(RTLD_STATIC_TLS_VARIANT_II)
2724 * Allocate the static TLS area. Return a pointer to the TCB. The
2725 * static area is based on negative offsets relative to the tcb.
2727 * The TCB contains an errno pointer for the system call layer, but because
2728 * we are the RTLD we really have no idea how the caller was compiled so
2729 * the information has to be passed in. errno can either be:
2731 * type 0 errno is a simple non-TLS global pointer.
2732 * (special case for e.g. libc_rtld)
2733 * type 1 errno accessed by GOT entry (dynamically linked programs)
2734 * type 2 errno accessed by %gs:OFFSET (statically linked programs)
2737 allocate_tls(Obj_Entry *objs)
2742 struct tls_tcb *tcb;
2747 * Allocate the new TCB. static TLS storage is placed just before the
2748 * TCB to support the %gs:OFFSET (negative offset) model.
2750 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
2751 ~RTLD_STATIC_TLS_ALIGN_MASK;
2752 tcb = malloc(data_size + sizeof(*tcb));
2753 tcb = (void *)((char *)tcb + data_size); /* actual tcb location */
2755 dtv_size = (tls_max_index + 2) * sizeof(Elf_Addr);
2756 dtv = malloc(dtv_size);
2757 bzero(dtv, dtv_size);
2759 #ifdef RTLD_TCB_HAS_SELF_POINTER
2760 tcb->tcb_self = tcb;
2763 tcb->tcb_pthread = NULL;
2765 dtv[0] = tls_dtv_generation;
2766 dtv[1] = tls_max_index;
2768 for (obj = objs; obj; obj = obj->next) {
2769 if (obj->tlsoffset) {
2770 addr = (Elf_Addr)tcb - obj->tlsoffset;
2771 memset((void *)(addr + obj->tlsinitsize),
2772 0, obj->tlssize - obj->tlsinitsize);
2774 memcpy((void*) addr, obj->tlsinit, obj->tlsinitsize);
2775 dtv[obj->tlsindex + 1] = addr;
2782 free_tls(struct tls_tcb *tcb)
2786 Elf_Addr tls_start, tls_end;
2789 data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) &
2790 ~RTLD_STATIC_TLS_ALIGN_MASK;
2793 tls_end = (Elf_Addr)tcb;
2794 tls_start = (Elf_Addr)tcb - data_size;
2795 for (i = 0; i < dtv_size; i++) {
2796 if (dtv[i+2] != 0 && (dtv[i+2] < tls_start || dtv[i+2] > tls_end)) {
2797 free((void *)dtv[i+2]);
2800 free((void *)tls_start);
2804 #error "Unsupported TLS layout"
2808 * Allocate TLS block for module with given index.
2811 allocate_module_tls(int index)
2816 for (obj = obj_list; obj; obj = obj->next) {
2817 if (obj->tlsindex == index)
2821 _rtld_error("Can't find module with TLS index %d", index);
2825 p = malloc(obj->tlssize);
2826 memcpy(p, obj->tlsinit, obj->tlsinitsize);
2827 memset(p + obj->tlsinitsize, 0, obj->tlssize - obj->tlsinitsize);
2833 allocate_tls_offset(Obj_Entry *obj)
2840 if (obj->tlssize == 0) {
2841 obj->tls_done = true;
2845 if (obj->tlsindex == 1)
2846 off = calculate_first_tls_offset(obj->tlssize, obj->tlsalign);
2848 off = calculate_tls_offset(tls_last_offset, tls_last_size,
2849 obj->tlssize, obj->tlsalign);
2852 * If we have already fixed the size of the static TLS block, we
2853 * must stay within that size. When allocating the static TLS, we
2854 * leave a small amount of space spare to be used for dynamically
2855 * loading modules which use static TLS.
2857 if (tls_static_space) {
2858 if (calculate_tls_end(off, obj->tlssize) > tls_static_space)
2862 tls_last_offset = obj->tlsoffset = off;
2863 tls_last_size = obj->tlssize;
2864 obj->tls_done = true;
2870 free_tls_offset(Obj_Entry *obj)
2872 #ifdef RTLD_STATIC_TLS_VARIANT_II
2874 * If we were the last thing to allocate out of the static TLS
2875 * block, we give our space back to the 'allocator'. This is a
2876 * simplistic workaround to allow libGL.so.1 to be loaded and
2877 * unloaded multiple times. We only handle the Variant II
2878 * mechanism for now - this really needs a proper allocator.
2880 if (calculate_tls_end(obj->tlsoffset, obj->tlssize)
2881 == calculate_tls_end(tls_last_offset, tls_last_size)) {
2882 tls_last_offset -= obj->tlssize;
2889 _rtld_allocate_tls(void)
2891 struct tls_tcb *new_tcb;
2894 new_tcb = allocate_tls(obj_list);
2901 _rtld_free_tls(struct tls_tcb *tcb)