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.
30 * Dynamic linker for ELF.
32 * John Polstra <jdp@polstra.com>.
36 #error "GCC is needed to compile this file"
39 #include <sys/param.h>
40 #include <sys/mount.h>
60 #define PATH_RTLD "/libexec/ld-elf.so.1"
62 #define PATH_RTLD "/libexec/ld-elf32.so.1"
66 typedef void (*func_ptr_type)();
67 typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg);
70 * This structure provides a reentrant way to keep a list of objects and
71 * check which ones have already been processed in some way.
73 typedef struct Struct_DoneList {
74 const Obj_Entry **objs; /* Array of object pointers */
75 unsigned int num_alloc; /* Allocated size of the array */
76 unsigned int num_used; /* Number of array slots used */
80 * Function declarations.
82 static const char *basename(const char *);
83 static void die(void);
84 static void digest_dynamic(Obj_Entry *, int);
85 static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
86 static Obj_Entry *dlcheck(void *);
87 static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *);
88 static bool donelist_check(DoneList *, const Obj_Entry *);
89 static void errmsg_restore(char *);
90 static char *errmsg_save(void);
91 static void *fill_search_info(const char *, size_t, void *);
92 static char *find_library(const char *, const Obj_Entry *);
93 static const char *gethints(void);
94 static void init_dag(Obj_Entry *);
95 static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *);
96 static void init_rtld(caddr_t);
97 static void initlist_add_neededs(Needed_Entry *needed, Objlist *list);
98 static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail,
100 static bool is_exported(const Elf_Sym *);
101 static void linkmap_add(Obj_Entry *);
102 static void linkmap_delete(Obj_Entry *);
103 static int load_needed_objects(Obj_Entry *);
104 static int load_preload_objects(void);
105 static Obj_Entry *load_object(char *);
106 static Obj_Entry *obj_from_addr(const void *);
107 static void objlist_call_fini(Objlist *);
108 static void objlist_call_init(Objlist *);
109 static void objlist_clear(Objlist *);
110 static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *);
111 static void objlist_init(Objlist *);
112 static void objlist_push_head(Objlist *, Obj_Entry *);
113 static void objlist_push_tail(Objlist *, Obj_Entry *);
114 static void objlist_remove(Objlist *, Obj_Entry *);
115 static void objlist_remove_unref(Objlist *);
116 static void *path_enumerate(const char *, path_enum_proc, void *);
117 static int relocate_objects(Obj_Entry *, bool, Obj_Entry *);
118 static int rtld_dirname(const char *, char *);
119 static void rtld_exit(void);
120 static char *search_library_path(const char *, const char *);
121 static const void **get_program_var_addr(const char *name);
122 static void set_program_var(const char *, const void *);
123 static const Elf_Sym *symlook_default(const char *, unsigned long hash,
124 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt);
125 static const Elf_Sym *symlook_list(const char *, unsigned long,
126 Objlist *, const Obj_Entry **, bool in_plt, DoneList *);
127 static void trace_loaded_objects(Obj_Entry *obj);
128 static void unlink_object(Obj_Entry *);
129 static void unload_object(Obj_Entry *);
130 static void unref_dag(Obj_Entry *);
131 static void ref_dag(Obj_Entry *);
133 void r_debug_state(struct r_debug*, struct link_map*);
138 static char *error_message; /* Message for dlerror(), or NULL */
139 struct r_debug r_debug; /* for GDB; */
140 static bool libmap_disable; /* Disable libmap */
141 static char *libmap_override; /* Maps to use in addition to libmap.conf */
142 static bool trust; /* False for setuid and setgid programs */
143 static bool dangerous_ld_env; /* True if environment variables have been
144 used to affect the libraries loaded */
145 static char *ld_bind_now; /* Environment variable for immediate binding */
146 static char *ld_debug; /* Environment variable for debugging */
147 static char *ld_library_path; /* Environment variable for search path */
148 static char *ld_preload; /* Environment variable for libraries to
150 static char *ld_tracing; /* Called from ldd to print libs */
151 static Obj_Entry *obj_list; /* Head of linked list of shared objects */
152 static Obj_Entry **obj_tail; /* Link field of last object in list */
153 static Obj_Entry *obj_main; /* The main program shared object */
154 static Obj_Entry obj_rtld; /* The dynamic linker shared object */
155 static unsigned int obj_count; /* Number of objects in obj_list */
157 static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */
158 STAILQ_HEAD_INITIALIZER(list_global);
159 static Objlist list_main = /* Objects loaded at program startup */
160 STAILQ_HEAD_INITIALIZER(list_main);
161 static Objlist list_fini = /* Objects needing fini() calls */
162 STAILQ_HEAD_INITIALIZER(list_fini);
164 static Elf_Sym sym_zero; /* For resolving undefined weak refs. */
166 #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m);
168 extern Elf_Dyn _DYNAMIC;
169 #pragma weak _DYNAMIC
170 #ifndef RTLD_IS_DYNAMIC
171 #define RTLD_IS_DYNAMIC() (&_DYNAMIC != NULL)
175 * These are the functions the dynamic linker exports to application
176 * programs. They are the only symbols the dynamic linker is willing
177 * to export from itself.
179 static func_ptr_type exports[] = {
180 (func_ptr_type) &_rtld_error,
181 (func_ptr_type) &dlclose,
182 (func_ptr_type) &dlerror,
183 (func_ptr_type) &dlopen,
184 (func_ptr_type) &dlsym,
185 (func_ptr_type) &dladdr,
186 (func_ptr_type) &dllockinit,
187 (func_ptr_type) &dlinfo,
188 (func_ptr_type) &_rtld_thread_init,
190 (func_ptr_type) &___tls_get_addr,
192 (func_ptr_type) &__tls_get_addr,
193 (func_ptr_type) &_rtld_allocate_tls,
194 (func_ptr_type) &_rtld_free_tls,
199 * Global declarations normally provided by crt1. The dynamic linker is
200 * not built with crt1, so we have to provide them ourselves.
206 * Globals to control TLS allocation.
208 size_t tls_last_offset; /* Static TLS offset of last module */
209 size_t tls_last_size; /* Static TLS size of last module */
210 size_t tls_static_space; /* Static TLS space allocated */
211 int tls_dtv_generation = 1; /* Used to detect when dtv size changes */
212 int tls_max_index = 1; /* Largest module index allocated */
215 * Fill in a DoneList with an allocation large enough to hold all of
216 * the currently-loaded objects. Keep this as a macro since it calls
217 * alloca and we want that to occur within the scope of the caller.
219 #define donelist_init(dlp) \
220 ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \
221 assert((dlp)->objs != NULL), \
222 (dlp)->num_alloc = obj_count, \
226 * Main entry point for dynamic linking. The first argument is the
227 * stack pointer. The stack is expected to be laid out as described
228 * in the SVR4 ABI specification, Intel 386 Processor Supplement.
229 * Specifically, the stack pointer points to a word containing
230 * ARGC. Following that in the stack is a null-terminated sequence
231 * of pointers to argument strings. Then comes a null-terminated
232 * sequence of pointers to environment strings. Finally, there is a
233 * sequence of "auxiliary vector" entries.
235 * The second argument points to a place to store the dynamic linker's
236 * exit procedure pointer and the third to a place to store the main
239 * The return value is the main program's entry point.
242 _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp)
244 Elf_Auxinfo *aux_info[AT_COUNT];
252 Objlist_Entry *entry;
254 Obj_Entry **preload_tail;
259 * On entry, the dynamic linker itself has not been relocated yet.
260 * Be very careful not to reference any global data until after
261 * init_rtld has returned. It is OK to reference file-scope statics
262 * and string constants, and to call static and global functions.
265 /* Find the auxiliary vector on the stack. */
268 sp += argc + 1; /* Skip over arguments and NULL terminator */
270 while (*sp++ != 0) /* Skip over environment, and NULL terminator */
272 aux = (Elf_Auxinfo *) sp;
274 /* Digest the auxiliary vector. */
275 for (i = 0; i < AT_COUNT; i++)
277 for (auxp = aux; auxp->a_type != AT_NULL; auxp++) {
278 if (auxp->a_type < AT_COUNT)
279 aux_info[auxp->a_type] = auxp;
282 /* Initialize and relocate ourselves. */
283 assert(aux_info[AT_BASE] != NULL);
284 init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
286 __progname = obj_rtld.path;
287 argv0 = argv[0] != NULL ? argv[0] : "(null)";
290 trust = !issetugid();
292 ld_bind_now = getenv(LD_ "BIND_NOW");
294 ld_debug = getenv(LD_ "DEBUG");
295 libmap_disable = getenv(LD_ "LIBMAP_DISABLE") != NULL;
296 libmap_override = getenv(LD_ "LIBMAP");
297 ld_library_path = getenv(LD_ "LIBRARY_PATH");
298 ld_preload = getenv(LD_ "PRELOAD");
299 dangerous_ld_env = libmap_disable || (libmap_override != NULL) ||
300 (ld_library_path != NULL) || (ld_preload != NULL);
302 dangerous_ld_env = 0;
303 ld_tracing = getenv(LD_ "TRACE_LOADED_OBJECTS");
305 if (ld_debug != NULL && *ld_debug != '\0')
307 dbg("%s is initialized, base address = %p", __progname,
308 (caddr_t) aux_info[AT_BASE]->a_un.a_ptr);
309 dbg("RTLD dynamic = %p", obj_rtld.dynamic);
310 dbg("RTLD pltgot = %p", obj_rtld.pltgot);
313 * Load the main program, or process its program header if it is
316 if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */
317 int fd = aux_info[AT_EXECFD]->a_un.a_val;
318 dbg("loading main program");
319 obj_main = map_object(fd, argv0, NULL);
321 if (obj_main == NULL)
323 } else { /* Main program already loaded. */
324 const Elf_Phdr *phdr;
328 dbg("processing main program's program header");
329 assert(aux_info[AT_PHDR] != NULL);
330 phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr;
331 assert(aux_info[AT_PHNUM] != NULL);
332 phnum = aux_info[AT_PHNUM]->a_un.a_val;
333 assert(aux_info[AT_PHENT] != NULL);
334 assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr));
335 assert(aux_info[AT_ENTRY] != NULL);
336 entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr;
337 if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL)
341 obj_main->path = xstrdup(argv0);
342 obj_main->mainprog = true;
345 * Get the actual dynamic linker pathname from the executable if
346 * possible. (It should always be possible.) That ensures that
347 * gdb will find the right dynamic linker even if a non-standard
350 if (obj_main->interp != NULL &&
351 strcmp(obj_main->interp, obj_rtld.path) != 0) {
353 obj_rtld.path = xstrdup(obj_main->interp);
354 __progname = obj_rtld.path;
357 digest_dynamic(obj_main, 0);
359 linkmap_add(obj_main);
360 linkmap_add(&obj_rtld);
362 /* Link the main program into the list of objects. */
363 *obj_tail = obj_main;
364 obj_tail = &obj_main->next;
366 /* Make sure we don't call the main program's init and fini functions. */
367 obj_main->init = obj_main->fini = (Elf_Addr)NULL;
369 /* Initialize a fake symbol for resolving undefined weak references. */
370 sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE);
371 sym_zero.st_shndx = SHN_UNDEF;
374 libmap_disable = (bool)lm_init(libmap_override);
376 dbg("loading LD_PRELOAD libraries");
377 if (load_preload_objects() == -1)
379 preload_tail = obj_tail;
381 dbg("loading needed objects");
382 if (load_needed_objects(obj_main) == -1)
385 /* Make a list of all objects loaded at startup. */
386 for (obj = obj_list; obj != NULL; obj = obj->next) {
387 objlist_push_tail(&list_main, obj);
391 if (ld_tracing) { /* We're done */
392 trace_loaded_objects(obj_main);
396 if (getenv(LD_ "DUMP_REL_PRE") != NULL) {
397 dump_relocations(obj_main);
401 /* setup TLS for main thread */
402 dbg("initializing initial thread local storage");
403 STAILQ_FOREACH(entry, &list_main, link) {
405 * Allocate all the initial objects out of the static TLS
406 * block even if they didn't ask for it.
408 allocate_tls_offset(entry->obj);
410 allocate_initial_tls(obj_list);
412 if (relocate_objects(obj_main,
413 ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1)
416 dbg("doing copy relocations");
417 if (do_copy_relocations(obj_main) == -1)
420 if (getenv(LD_ "DUMP_REL_POST") != NULL) {
421 dump_relocations(obj_main);
425 dbg("initializing key program variables");
426 set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : "");
427 set_program_var("environ", env);
429 dbg("initializing thread locks");
432 /* Make a list of init functions to call. */
433 objlist_init(&initlist);
434 initlist_add_objects(obj_list, preload_tail, &initlist);
436 r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */
438 objlist_call_init(&initlist);
439 lockstate = wlock_acquire(rtld_bind_lock);
440 objlist_clear(&initlist);
441 wlock_release(rtld_bind_lock, lockstate);
443 dbg("transferring control to program entry point = %p", obj_main->entry);
445 /* Return the exit procedure and the program entry point. */
446 *exit_proc = rtld_exit;
448 return (func_ptr_type) obj_main->entry;
452 _rtld_bind(Obj_Entry *obj, Elf_Word reloff)
456 const Obj_Entry *defobj;
461 lockstate = rlock_acquire(rtld_bind_lock);
463 rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff);
465 rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff);
467 where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
468 def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL);
472 target = (Elf_Addr)(defobj->relocbase + def->st_value);
474 dbg("\"%s\" in \"%s\" ==> %p in \"%s\"",
475 defobj->strtab + def->st_name, basename(obj->path),
476 (void *)target, basename(defobj->path));
479 * Write the new contents for the jmpslot. Note that depending on
480 * architecture, the value which we need to return back to the
481 * lazy binding trampoline may or may not be the target
482 * address. The value returned from reloc_jmpslot() is the value
483 * that the trampoline needs.
485 target = reloc_jmpslot(where, target, defobj, obj, rel);
486 rlock_release(rtld_bind_lock, lockstate);
491 * Error reporting function. Use it like printf. If formats the message
492 * into a buffer, and sets things up so that the next call to dlerror()
493 * will return the message.
496 _rtld_error(const char *fmt, ...)
498 static char buf[512];
502 vsnprintf(buf, sizeof buf, fmt, ap);
508 * Return a dynamically-allocated copy of the current error message, if any.
513 return error_message == NULL ? NULL : xstrdup(error_message);
517 * Restore the current error message from a copy which was previously saved
518 * by errmsg_save(). The copy is freed.
521 errmsg_restore(char *saved_msg)
523 if (saved_msg == NULL)
524 error_message = NULL;
526 _rtld_error("%s", saved_msg);
532 basename(const char *name)
534 const char *p = strrchr(name, '/');
535 return p != NULL ? p + 1 : name;
541 const char *msg = dlerror();
549 * Process a shared object's DYNAMIC section, and save the important
550 * information in its Obj_Entry structure.
553 digest_dynamic(Obj_Entry *obj, int early)
556 Needed_Entry **needed_tail = &obj->needed;
557 const Elf_Dyn *dyn_rpath = NULL;
558 int plttype = DT_REL;
560 obj->bind_now = false;
561 for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) {
562 switch (dynp->d_tag) {
565 obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr);
569 obj->relsize = dynp->d_un.d_val;
573 assert(dynp->d_un.d_val == sizeof(Elf_Rel));
577 obj->pltrel = (const Elf_Rel *)
578 (obj->relocbase + dynp->d_un.d_ptr);
582 obj->pltrelsize = dynp->d_un.d_val;
586 obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr);
590 obj->relasize = dynp->d_un.d_val;
594 assert(dynp->d_un.d_val == sizeof(Elf_Rela));
598 plttype = dynp->d_un.d_val;
599 assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA);
603 obj->symtab = (const Elf_Sym *)
604 (obj->relocbase + dynp->d_un.d_ptr);
608 assert(dynp->d_un.d_val == sizeof(Elf_Sym));
612 obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr);
616 obj->strsize = dynp->d_un.d_val;
621 const Elf_Hashelt *hashtab = (const Elf_Hashelt *)
622 (obj->relocbase + dynp->d_un.d_ptr);
623 obj->nbuckets = hashtab[0];
624 obj->nchains = hashtab[1];
625 obj->buckets = hashtab + 2;
626 obj->chains = obj->buckets + obj->nbuckets;
632 Needed_Entry *nep = NEW(Needed_Entry);
633 nep->name = dynp->d_un.d_val;
638 needed_tail = &nep->next;
643 obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr);
651 obj->symbolic = true;
655 case DT_RUNPATH: /* XXX: process separately */
657 * We have to wait until later to process this, because we
658 * might not have gotten the address of the string table yet.
664 /* Not used by the dynamic linker. */
668 obj->init = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr);
672 obj->fini = (Elf_Addr) (obj->relocbase + dynp->d_un.d_ptr);
676 /* XXX - not implemented yet */
678 dbg("Filling in DT_DEBUG entry");
679 ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug;
683 if (dynp->d_un.d_val & DF_ORIGIN) {
684 obj->origin_path = xmalloc(PATH_MAX);
685 if (rtld_dirname(obj->path, obj->origin_path) == -1)
688 if (dynp->d_un.d_val & DF_SYMBOLIC)
689 obj->symbolic = true;
690 if (dynp->d_un.d_val & DF_TEXTREL)
692 if (dynp->d_un.d_val & DF_BIND_NOW)
693 obj->bind_now = true;
694 if (dynp->d_un.d_val & DF_STATIC_TLS)
700 dbg("Ignoring d_tag %ld = %#lx", (long)dynp->d_tag,
709 if (plttype == DT_RELA) {
710 obj->pltrela = (const Elf_Rela *) obj->pltrel;
712 obj->pltrelasize = obj->pltrelsize;
716 if (dyn_rpath != NULL)
717 obj->rpath = obj->strtab + dyn_rpath->d_un.d_val;
721 * Process a shared object's program header. This is used only for the
722 * main program, when the kernel has already loaded the main program
723 * into memory before calling the dynamic linker. It creates and
724 * returns an Obj_Entry structure.
727 digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path)
730 const Elf_Phdr *phlimit = phdr + phnum;
735 for (ph = phdr; ph < phlimit; ph++) {
736 switch (ph->p_type) {
739 if ((const Elf_Phdr *)ph->p_vaddr != phdr) {
740 _rtld_error("%s: invalid PT_PHDR", path);
743 obj->phdr = (const Elf_Phdr *) ph->p_vaddr;
744 obj->phsize = ph->p_memsz;
748 obj->interp = (const char *) ph->p_vaddr;
752 if (nsegs == 0) { /* First load segment */
753 obj->vaddrbase = trunc_page(ph->p_vaddr);
754 obj->mapbase = (caddr_t) obj->vaddrbase;
755 obj->relocbase = obj->mapbase - obj->vaddrbase;
756 obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) -
758 } else { /* Last load segment */
759 obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) -
766 obj->dynamic = (const Elf_Dyn *) ph->p_vaddr;
771 obj->tlssize = ph->p_memsz;
772 obj->tlsalign = ph->p_align;
773 obj->tlsinitsize = ph->p_filesz;
774 obj->tlsinit = (void*) ph->p_vaddr;
779 _rtld_error("%s: too few PT_LOAD segments", path);
788 dlcheck(void *handle)
792 for (obj = obj_list; obj != NULL; obj = obj->next)
793 if (obj == (Obj_Entry *) handle)
796 if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) {
797 _rtld_error("Invalid shared object handle %p", handle);
804 * If the given object is already in the donelist, return true. Otherwise
805 * add the object to the list and return false.
808 donelist_check(DoneList *dlp, const Obj_Entry *obj)
812 for (i = 0; i < dlp->num_used; i++)
813 if (dlp->objs[i] == obj)
816 * Our donelist allocation should always be sufficient. But if
817 * our threads locking isn't working properly, more shared objects
818 * could have been loaded since we allocated the list. That should
819 * never happen, but we'll handle it properly just in case it does.
821 if (dlp->num_used < dlp->num_alloc)
822 dlp->objs[dlp->num_used++] = obj;
827 * Hash function for symbol table lookup. Don't even think about changing
828 * this. It is specified by the System V ABI.
831 elf_hash(const char *name)
833 const unsigned char *p = (const unsigned char *) name;
839 if ((g = h & 0xf0000000) != 0)
847 * Find the library with the given name, and return its full pathname.
848 * The returned string is dynamically allocated. Generates an error
849 * message and returns NULL if the library cannot be found.
851 * If the second argument is non-NULL, then it refers to an already-
852 * loaded shared object, whose library search path will be searched.
854 * The search order is:
856 * rpath in the referencing file
861 find_library(const char *xname, const Obj_Entry *refobj)
866 if (strchr(xname, '/') != NULL) { /* Hard coded pathname */
867 if (xname[0] != '/' && !trust) {
868 _rtld_error("Absolute pathname required for shared object \"%s\"",
872 return xstrdup(xname);
875 if (libmap_disable || (refobj == NULL) ||
876 (name = lm_find(refobj->path, xname)) == NULL)
877 name = (char *)xname;
879 dbg(" Searching for \"%s\"", name);
881 if ((pathname = search_library_path(name, ld_library_path)) != NULL ||
883 (pathname = search_library_path(name, refobj->rpath)) != NULL) ||
884 (pathname = search_library_path(name, gethints())) != NULL ||
885 (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL)
888 if(refobj != NULL && refobj->path != NULL) {
889 _rtld_error("Shared object \"%s\" not found, required by \"%s\"",
890 name, basename(refobj->path));
892 _rtld_error("Shared object \"%s\" not found", name);
898 * Given a symbol number in a referencing object, find the corresponding
899 * definition of the symbol. Returns a pointer to the symbol, or NULL if
900 * no definition was found. Returns a pointer to the Obj_Entry of the
901 * defining object via the reference parameter DEFOBJ_OUT.
904 find_symdef(unsigned long symnum, const Obj_Entry *refobj,
905 const Obj_Entry **defobj_out, bool in_plt, SymCache *cache)
909 const Obj_Entry *defobj;
914 * If we have already found this symbol, get the information from
917 if (symnum >= refobj->nchains)
918 return NULL; /* Bad object */
919 if (cache != NULL && cache[symnum].sym != NULL) {
920 *defobj_out = cache[symnum].obj;
921 return cache[symnum].sym;
924 ref = refobj->symtab + symnum;
925 name = refobj->strtab + ref->st_name;
929 * We don't have to do a full scale lookup if the symbol is local.
930 * We know it will bind to the instance in this load module; to
931 * which we already have a pointer (ie ref). By not doing a lookup,
932 * we not only improve performance, but it also avoids unresolvable
933 * symbols when local symbols are not in the hash table. This has
934 * been seen with the ia64 toolchain.
936 if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) {
937 if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) {
938 _rtld_error("%s: Bogus symbol table entry %lu", refobj->path,
941 hash = elf_hash(name);
942 def = symlook_default(name, hash, refobj, &defobj, in_plt);
949 * If we found no definition and the reference is weak, treat the
950 * symbol as having the value zero.
952 if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) {
958 *defobj_out = defobj;
959 /* Record the information in the cache to avoid subsequent lookups. */
961 cache[symnum].sym = def;
962 cache[symnum].obj = defobj;
965 if (refobj != &obj_rtld)
966 _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
972 * Return the search path from the ldconfig hints file, reading it if
973 * necessary. Returns NULL if there are problems with the hints file,
974 * or if the search path there is empty.
983 struct elfhints_hdr hdr;
986 /* Keep from trying again in case the hints file is bad. */
989 if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1)
991 if (read(fd, &hdr, sizeof hdr) != sizeof hdr ||
992 hdr.magic != ELFHINTS_MAGIC ||
997 p = xmalloc(hdr.dirlistlen + 1);
998 if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 ||
999 read(fd, p, hdr.dirlistlen + 1) != (ssize_t)hdr.dirlistlen + 1) {
1007 return hints[0] != '\0' ? hints : NULL;
1011 init_dag(Obj_Entry *root)
1015 donelist_init(&donelist);
1016 init_dag1(root, root, &donelist);
1020 init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp)
1022 const Needed_Entry *needed;
1024 if (donelist_check(dlp, obj))
1028 objlist_push_tail(&obj->dldags, root);
1029 objlist_push_tail(&root->dagmembers, obj);
1030 for (needed = obj->needed; needed != NULL; needed = needed->next)
1031 if (needed->obj != NULL)
1032 init_dag1(root, needed->obj, dlp);
1036 * Initialize the dynamic linker. The argument is the address at which
1037 * the dynamic linker has been mapped into memory. The primary task of
1038 * this function is to relocate the dynamic linker.
1041 init_rtld(caddr_t mapbase)
1043 Obj_Entry objtmp; /* Temporary rtld object */
1046 * Conjure up an Obj_Entry structure for the dynamic linker.
1048 * The "path" member can't be initialized yet because string constatns
1049 * cannot yet be acessed. Below we will set it correctly.
1051 memset(&objtmp, 0, sizeof(objtmp));
1054 objtmp.mapbase = mapbase;
1056 objtmp.relocbase = mapbase;
1058 if (RTLD_IS_DYNAMIC()) {
1059 objtmp.dynamic = rtld_dynamic(&objtmp);
1060 digest_dynamic(&objtmp, 1);
1061 assert(objtmp.needed == NULL);
1062 assert(!objtmp.textrel);
1065 * Temporarily put the dynamic linker entry into the object list, so
1066 * that symbols can be found.
1069 relocate_objects(&objtmp, true, &objtmp);
1072 /* Initialize the object list. */
1073 obj_tail = &obj_list;
1075 /* Now that non-local variables can be accesses, copy out obj_rtld. */
1076 memcpy(&obj_rtld, &objtmp, sizeof(obj_rtld));
1078 /* Replace the path with a dynamically allocated copy. */
1079 obj_rtld.path = xstrdup(PATH_RTLD);
1081 r_debug.r_brk = r_debug_state;
1082 r_debug.r_state = RT_CONSISTENT;
1086 * Add the init functions from a needed object list (and its recursive
1087 * needed objects) to "list". This is not used directly; it is a helper
1088 * function for initlist_add_objects(). The write lock must be held
1089 * when this function is called.
1092 initlist_add_neededs(Needed_Entry *needed, Objlist *list)
1094 /* Recursively process the successor needed objects. */
1095 if (needed->next != NULL)
1096 initlist_add_neededs(needed->next, list);
1098 /* Process the current needed object. */
1099 if (needed->obj != NULL)
1100 initlist_add_objects(needed->obj, &needed->obj->next, list);
1104 * Scan all of the DAGs rooted in the range of objects from "obj" to
1105 * "tail" and add their init functions to "list". This recurses over
1106 * the DAGs and ensure the proper init ordering such that each object's
1107 * needed libraries are initialized before the object itself. At the
1108 * same time, this function adds the objects to the global finalization
1109 * list "list_fini" in the opposite order. The write lock must be
1110 * held when this function is called.
1113 initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list)
1117 obj->init_done = true;
1119 /* Recursively process the successor objects. */
1120 if (&obj->next != tail)
1121 initlist_add_objects(obj->next, tail, list);
1123 /* Recursively process the needed objects. */
1124 if (obj->needed != NULL)
1125 initlist_add_neededs(obj->needed, list);
1127 /* Add the object to the init list. */
1128 if (obj->init != (Elf_Addr)NULL)
1129 objlist_push_tail(list, obj);
1131 /* Add the object to the global fini list in the reverse order. */
1132 if (obj->fini != (Elf_Addr)NULL)
1133 objlist_push_head(&list_fini, obj);
1137 #define FPTR_TARGET(f) ((Elf_Addr) (f))
1141 is_exported(const Elf_Sym *def)
1144 const func_ptr_type *p;
1146 value = (Elf_Addr)(obj_rtld.relocbase + def->st_value);
1147 for (p = exports; *p != NULL; p++)
1148 if (FPTR_TARGET(*p) == value)
1154 * Given a shared object, traverse its list of needed objects, and load
1155 * each of them. Returns 0 on success. Generates an error message and
1156 * returns -1 on failure.
1159 load_needed_objects(Obj_Entry *first)
1163 for (obj = first; obj != NULL; obj = obj->next) {
1164 Needed_Entry *needed;
1166 for (needed = obj->needed; needed != NULL; needed = needed->next) {
1167 const char *name = obj->strtab + needed->name;
1168 char *path = find_library(name, obj);
1171 if (path == NULL && !ld_tracing)
1175 needed->obj = load_object(path);
1176 if (needed->obj == NULL && !ld_tracing)
1177 return -1; /* XXX - cleanup */
1186 load_preload_objects(void)
1188 char *p = ld_preload;
1189 static const char delim[] = " \t:;";
1194 p += strspn(p, delim);
1195 while (*p != '\0') {
1196 size_t len = strcspn(p, delim);
1202 if ((path = find_library(p, NULL)) == NULL)
1204 if (load_object(path) == NULL)
1205 return -1; /* XXX - cleanup */
1208 p += strspn(p, delim);
1214 * Load a shared object into memory, if it is not already loaded. The
1215 * argument must be a string allocated on the heap. This function assumes
1216 * responsibility for freeing it when necessary.
1218 * Returns a pointer to the Obj_Entry for the object. Returns NULL
1222 load_object(char *path)
1229 for (obj = obj_list->next; obj != NULL; obj = obj->next)
1230 if (strcmp(obj->path, path) == 0)
1234 * If we didn't find a match by pathname, open the file and check
1235 * again by device and inode. This avoids false mismatches caused
1236 * by multiple links or ".." in pathnames.
1238 * To avoid a race, we open the file and use fstat() rather than
1242 if ((fd = open(path, O_RDONLY)) == -1) {
1243 _rtld_error("Cannot open \"%s\"", path);
1246 if (fstat(fd, &sb) == -1) {
1247 _rtld_error("Cannot fstat \"%s\"", path);
1251 for (obj = obj_list->next; obj != NULL; obj = obj->next) {
1252 if (obj->ino == sb.st_ino && obj->dev == sb.st_dev) {
1259 if (obj == NULL) { /* First use of this object, so we must map it in */
1261 * but first, make sure that environment variables haven't been
1262 * used to circumvent the noexec flag on a filesystem.
1264 if (dangerous_ld_env) {
1265 if (fstatfs(fd, &fs) != 0) {
1266 _rtld_error("Cannot fstatfs \"%s\"", path);
1270 if (fs.f_flags & MNT_NOEXEC) {
1271 _rtld_error("Cannot execute objects on %s\n", fs.f_mntonname);
1276 dbg("loading \"%s\"", path);
1277 obj = map_object(fd, path, &sb);
1285 digest_dynamic(obj, 0);
1288 obj_tail = &obj->next;
1290 linkmap_add(obj); /* for GDB & dlinfo() */
1292 dbg(" %p .. %p: %s", obj->mapbase,
1293 obj->mapbase + obj->mapsize - 1, obj->path);
1295 dbg(" WARNING: %s has impure text", obj->path);
1303 obj_from_addr(const void *addr)
1307 for (obj = obj_list; obj != NULL; obj = obj->next) {
1308 if (addr < (void *) obj->mapbase)
1310 if (addr < (void *) (obj->mapbase + obj->mapsize))
1317 * Call the finalization functions for each of the objects in "list"
1318 * which are unreferenced. All of the objects are expected to have
1319 * non-NULL fini functions.
1322 objlist_call_fini(Objlist *list)
1328 * Preserve the current error message since a fini function might
1329 * call into the dynamic linker and overwrite it.
1331 saved_msg = errmsg_save();
1332 STAILQ_FOREACH(elm, list, link) {
1333 if (elm->obj->refcount == 0) {
1334 dbg("calling fini function for %s at %p", elm->obj->path,
1335 (void *)elm->obj->fini);
1336 call_initfini_pointer(elm->obj, elm->obj->fini);
1339 errmsg_restore(saved_msg);
1343 * Call the initialization functions for each of the objects in
1344 * "list". All of the objects are expected to have non-NULL init
1348 objlist_call_init(Objlist *list)
1354 * Preserve the current error message since an init function might
1355 * call into the dynamic linker and overwrite it.
1357 saved_msg = errmsg_save();
1358 STAILQ_FOREACH(elm, list, link) {
1359 dbg("calling init function for %s at %p", elm->obj->path,
1360 (void *)elm->obj->init);
1361 call_initfini_pointer(elm->obj, elm->obj->init);
1363 errmsg_restore(saved_msg);
1367 objlist_clear(Objlist *list)
1371 while (!STAILQ_EMPTY(list)) {
1372 elm = STAILQ_FIRST(list);
1373 STAILQ_REMOVE_HEAD(list, link);
1378 static Objlist_Entry *
1379 objlist_find(Objlist *list, const Obj_Entry *obj)
1383 STAILQ_FOREACH(elm, list, link)
1384 if (elm->obj == obj)
1390 objlist_init(Objlist *list)
1396 objlist_push_head(Objlist *list, Obj_Entry *obj)
1400 elm = NEW(Objlist_Entry);
1402 STAILQ_INSERT_HEAD(list, elm, link);
1406 objlist_push_tail(Objlist *list, Obj_Entry *obj)
1410 elm = NEW(Objlist_Entry);
1412 STAILQ_INSERT_TAIL(list, elm, link);
1416 objlist_remove(Objlist *list, Obj_Entry *obj)
1420 if ((elm = objlist_find(list, obj)) != NULL) {
1421 STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link);
1427 * Remove all of the unreferenced objects from "list".
1430 objlist_remove_unref(Objlist *list)
1435 STAILQ_INIT(&newlist);
1436 while (!STAILQ_EMPTY(list)) {
1437 elm = STAILQ_FIRST(list);
1438 STAILQ_REMOVE_HEAD(list, link);
1439 if (elm->obj->refcount == 0)
1442 STAILQ_INSERT_TAIL(&newlist, elm, link);
1448 * Relocate newly-loaded shared objects. The argument is a pointer to
1449 * the Obj_Entry for the first such object. All objects from the first
1450 * to the end of the list of objects are relocated. Returns 0 on success,
1454 relocate_objects(Obj_Entry *first, bool bind_now, Obj_Entry *rtldobj)
1458 for (obj = first; obj != NULL; obj = obj->next) {
1460 dbg("relocating \"%s\"", obj->path);
1461 if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL ||
1462 obj->symtab == NULL || obj->strtab == NULL) {
1463 _rtld_error("%s: Shared object has no run-time symbol table",
1469 /* There are relocations to the write-protected text segment. */
1470 if (mprotect(obj->mapbase, obj->textsize,
1471 PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
1472 _rtld_error("%s: Cannot write-enable text segment: %s",
1473 obj->path, strerror(errno));
1478 /* Process the non-PLT relocations. */
1479 if (reloc_non_plt(obj, rtldobj))
1482 if (obj->textrel) { /* Re-protected the text segment. */
1483 if (mprotect(obj->mapbase, obj->textsize,
1484 PROT_READ|PROT_EXEC) == -1) {
1485 _rtld_error("%s: Cannot write-protect text segment: %s",
1486 obj->path, strerror(errno));
1491 /* Process the PLT relocations. */
1492 if (reloc_plt(obj) == -1)
1494 /* Relocate the jump slots if we are doing immediate binding. */
1495 if (obj->bind_now || bind_now)
1496 if (reloc_jmpslots(obj) == -1)
1501 * Set up the magic number and version in the Obj_Entry. These
1502 * were checked in the crt1.o from the original ElfKit, so we
1503 * set them for backward compatibility.
1505 obj->magic = RTLD_MAGIC;
1506 obj->version = RTLD_VERSION;
1508 /* Set the special PLT or GOT entries. */
1516 * Cleanup procedure. It will be called (by the atexit mechanism) just
1517 * before the process exits.
1525 /* Clear all the reference counts so the fini functions will be called. */
1526 for (obj = obj_list; obj != NULL; obj = obj->next)
1528 objlist_call_fini(&list_fini);
1529 /* No need to remove the items from the list, since we are exiting. */
1530 if (!libmap_disable)
1535 path_enumerate(const char *path, path_enum_proc callback, void *arg)
1543 path += strspn(path, ":;");
1544 while (*path != '\0') {
1548 len = strcspn(path, ":;");
1550 trans = lm_findn(NULL, path, len);
1552 res = callback(trans, strlen(trans), arg);
1555 res = callback(path, len, arg);
1561 path += strspn(path, ":;");
1567 struct try_library_args {
1575 try_library_path(const char *dir, size_t dirlen, void *param)
1577 struct try_library_args *arg;
1580 if (*dir == '/' || trust) {
1583 if (dirlen + 1 + arg->namelen + 1 > arg->buflen)
1586 pathname = arg->buffer;
1587 strncpy(pathname, dir, dirlen);
1588 pathname[dirlen] = '/';
1589 strcpy(pathname + dirlen + 1, arg->name);
1591 dbg(" Trying \"%s\"", pathname);
1592 if (access(pathname, F_OK) == 0) { /* We found it */
1593 pathname = xmalloc(dirlen + 1 + arg->namelen + 1);
1594 strcpy(pathname, arg->buffer);
1602 search_library_path(const char *name, const char *path)
1605 struct try_library_args arg;
1611 arg.namelen = strlen(name);
1612 arg.buffer = xmalloc(PATH_MAX);
1613 arg.buflen = PATH_MAX;
1615 p = path_enumerate(path, try_library_path, &arg);
1623 dlclose(void *handle)
1628 lockstate = wlock_acquire(rtld_bind_lock);
1629 root = dlcheck(handle);
1631 wlock_release(rtld_bind_lock, lockstate);
1635 /* Unreference the object and its dependencies. */
1636 root->dl_refcount--;
1640 if (root->refcount == 0) {
1642 * The object is no longer referenced, so we must unload it.
1643 * First, call the fini functions with no locks held.
1645 wlock_release(rtld_bind_lock, lockstate);
1646 objlist_call_fini(&list_fini);
1647 lockstate = wlock_acquire(rtld_bind_lock);
1648 objlist_remove_unref(&list_fini);
1650 /* Finish cleaning up the newly-unreferenced objects. */
1651 GDB_STATE(RT_DELETE,&root->linkmap);
1652 unload_object(root);
1653 GDB_STATE(RT_CONSISTENT,NULL);
1655 wlock_release(rtld_bind_lock, lockstate);
1662 char *msg = error_message;
1663 error_message = NULL;
1668 * This function is deprecated and has no effect.
1671 dllockinit(void *context,
1672 void *(*lock_create)(void *context),
1673 void (*rlock_acquire)(void *lock),
1674 void (*wlock_acquire)(void *lock),
1675 void (*lock_release)(void *lock),
1676 void (*lock_destroy)(void *lock),
1677 void (*context_destroy)(void *context))
1679 static void *cur_context;
1680 static void (*cur_context_destroy)(void *);
1682 /* Just destroy the context from the previous call, if necessary. */
1683 if (cur_context_destroy != NULL)
1684 cur_context_destroy(cur_context);
1685 cur_context = context;
1686 cur_context_destroy = context_destroy;
1690 dlopen(const char *name, int mode)
1692 Obj_Entry **old_obj_tail;
1695 int result, lockstate;
1697 ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1";
1698 if (ld_tracing != NULL)
1699 environ = (char **)*get_program_var_addr("environ");
1701 objlist_init(&initlist);
1703 lockstate = wlock_acquire(rtld_bind_lock);
1704 GDB_STATE(RT_ADD,NULL);
1706 old_obj_tail = obj_tail;
1712 char *path = find_library(name, obj_main);
1714 obj = load_object(path);
1719 if (mode & RTLD_GLOBAL && objlist_find(&list_global, obj) == NULL)
1720 objlist_push_tail(&list_global, obj);
1721 mode &= RTLD_MODEMASK;
1722 if (*old_obj_tail != NULL) { /* We loaded something new. */
1723 assert(*old_obj_tail == obj);
1725 result = load_needed_objects(obj);
1726 if (result != -1 && ld_tracing)
1730 (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW,
1731 &obj_rtld)) == -1) {
1734 if (obj->refcount == 0)
1738 /* Make list of init functions to call. */
1739 initlist_add_objects(obj, &obj->next, &initlist);
1743 /* Bump the reference counts for objects on this DAG. */
1751 GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL);
1753 /* Call the init functions with no locks held. */
1754 wlock_release(rtld_bind_lock, lockstate);
1755 objlist_call_init(&initlist);
1756 lockstate = wlock_acquire(rtld_bind_lock);
1757 objlist_clear(&initlist);
1758 wlock_release(rtld_bind_lock, lockstate);
1761 trace_loaded_objects(obj);
1762 wlock_release(rtld_bind_lock, lockstate);
1767 dlsym(void *handle, const char *name)
1769 const Obj_Entry *obj;
1772 const Obj_Entry *defobj;
1775 hash = elf_hash(name);
1779 lockstate = rlock_acquire(rtld_bind_lock);
1780 if (handle == NULL || handle == RTLD_NEXT ||
1781 handle == RTLD_DEFAULT || handle == RTLD_SELF) {
1784 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1785 if ((obj = obj_from_addr(retaddr)) == NULL) {
1786 _rtld_error("Cannot determine caller's shared object");
1787 rlock_release(rtld_bind_lock, lockstate);
1790 if (handle == NULL) { /* Just the caller's shared object. */
1791 def = symlook_obj(name, hash, obj, true);
1793 } else if (handle == RTLD_NEXT || /* Objects after caller's */
1794 handle == RTLD_SELF) { /* ... caller included */
1795 if (handle == RTLD_NEXT)
1797 for (; obj != NULL; obj = obj->next) {
1798 if ((def = symlook_obj(name, hash, obj, true)) != NULL) {
1804 assert(handle == RTLD_DEFAULT);
1805 def = symlook_default(name, hash, obj, &defobj, true);
1808 if ((obj = dlcheck(handle)) == NULL) {
1809 rlock_release(rtld_bind_lock, lockstate);
1813 if (obj->mainprog) {
1816 /* Search main program and all libraries loaded by it. */
1817 donelist_init(&donelist);
1818 def = symlook_list(name, hash, &list_main, &defobj, true,
1822 * XXX - This isn't correct. The search should include the whole
1823 * DAG rooted at the given object.
1825 def = symlook_obj(name, hash, obj, true);
1831 rlock_release(rtld_bind_lock, lockstate);
1834 * The value required by the caller is derived from the value
1835 * of the symbol. For the ia64 architecture, we need to
1836 * construct a function descriptor which the caller can use to
1837 * call the function with the right 'gp' value. For other
1838 * architectures and for non-functions, the value is simply
1839 * the relocated value of the symbol.
1841 if (ELF_ST_TYPE(def->st_info) == STT_FUNC)
1842 return make_function_pointer(def, defobj);
1844 return defobj->relocbase + def->st_value;
1847 _rtld_error("Undefined symbol \"%s\"", name);
1848 rlock_release(rtld_bind_lock, lockstate);
1853 dladdr(const void *addr, Dl_info *info)
1855 const Obj_Entry *obj;
1858 unsigned long symoffset;
1861 lockstate = rlock_acquire(rtld_bind_lock);
1862 obj = obj_from_addr(addr);
1864 _rtld_error("No shared object contains address");
1865 rlock_release(rtld_bind_lock, lockstate);
1868 info->dli_fname = obj->path;
1869 info->dli_fbase = obj->mapbase;
1870 info->dli_saddr = (void *)0;
1871 info->dli_sname = NULL;
1874 * Walk the symbol list looking for the symbol whose address is
1875 * closest to the address sent in.
1877 for (symoffset = 0; symoffset < obj->nchains; symoffset++) {
1878 def = obj->symtab + symoffset;
1881 * For skip the symbol if st_shndx is either SHN_UNDEF or
1884 if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON)
1888 * If the symbol is greater than the specified address, or if it
1889 * is further away from addr than the current nearest symbol,
1892 symbol_addr = obj->relocbase + def->st_value;
1893 if (symbol_addr > addr || symbol_addr < info->dli_saddr)
1896 /* Update our idea of the nearest symbol. */
1897 info->dli_sname = obj->strtab + def->st_name;
1898 info->dli_saddr = symbol_addr;
1901 if (info->dli_saddr == addr)
1904 rlock_release(rtld_bind_lock, lockstate);
1909 dlinfo(void *handle, int request, void *p)
1911 const Obj_Entry *obj;
1912 int error, lockstate;
1914 lockstate = rlock_acquire(rtld_bind_lock);
1916 if (handle == NULL || handle == RTLD_SELF) {
1919 retaddr = __builtin_return_address(0); /* __GNUC__ only */
1920 if ((obj = obj_from_addr(retaddr)) == NULL)
1921 _rtld_error("Cannot determine caller's shared object");
1923 obj = dlcheck(handle);
1926 rlock_release(rtld_bind_lock, lockstate);
1932 case RTLD_DI_LINKMAP:
1933 *((struct link_map const **)p) = &obj->linkmap;
1935 case RTLD_DI_ORIGIN:
1936 error = rtld_dirname(obj->path, p);
1939 case RTLD_DI_SERINFOSIZE:
1940 case RTLD_DI_SERINFO:
1941 error = do_search_info(obj, request, (struct dl_serinfo *)p);
1945 _rtld_error("Invalid request %d passed to dlinfo()", request);
1949 rlock_release(rtld_bind_lock, lockstate);
1954 struct fill_search_info_args {
1957 Dl_serinfo *serinfo;
1958 Dl_serpath *serpath;
1963 fill_search_info(const char *dir, size_t dirlen, void *param)
1965 struct fill_search_info_args *arg;
1969 if (arg->request == RTLD_DI_SERINFOSIZE) {
1970 arg->serinfo->dls_cnt ++;
1971 arg->serinfo->dls_size += dirlen + 1;
1973 struct dl_serpath *s_entry;
1975 s_entry = arg->serpath;
1976 s_entry->dls_name = arg->strspace;
1977 s_entry->dls_flags = arg->flags;
1979 strncpy(arg->strspace, dir, dirlen);
1980 arg->strspace[dirlen] = '\0';
1982 arg->strspace += dirlen + 1;
1990 do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info)
1992 struct dl_serinfo _info;
1993 struct fill_search_info_args args;
1995 args.request = RTLD_DI_SERINFOSIZE;
1996 args.serinfo = &_info;
1998 _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath);
2001 path_enumerate(ld_library_path, fill_search_info, &args);
2002 path_enumerate(obj->rpath, fill_search_info, &args);
2003 path_enumerate(gethints(), fill_search_info, &args);
2004 path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args);
2007 if (request == RTLD_DI_SERINFOSIZE) {
2008 info->dls_size = _info.dls_size;
2009 info->dls_cnt = _info.dls_cnt;
2013 if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) {
2014 _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()");
2018 args.request = RTLD_DI_SERINFO;
2019 args.serinfo = info;
2020 args.serpath = &info->dls_serpath[0];
2021 args.strspace = (char *)&info->dls_serpath[_info.dls_cnt];
2023 args.flags = LA_SER_LIBPATH;
2024 if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL)
2027 args.flags = LA_SER_RUNPATH;
2028 if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL)
2031 args.flags = LA_SER_CONFIG;
2032 if (path_enumerate(gethints(), fill_search_info, &args) != NULL)
2035 args.flags = LA_SER_DEFAULT;
2036 if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL)
2042 rtld_dirname(const char *path, char *bname)
2046 /* Empty or NULL string gets treated as "." */
2047 if (path == NULL || *path == '\0') {
2053 /* Strip trailing slashes */
2054 endp = path + strlen(path) - 1;
2055 while (endp > path && *endp == '/')
2058 /* Find the start of the dir */
2059 while (endp > path && *endp != '/')
2062 /* Either the dir is "/" or there are no slashes */
2064 bname[0] = *endp == '/' ? '/' : '.';
2070 } while (endp > path && *endp == '/');
2073 if (endp - path + 2 > PATH_MAX)
2075 _rtld_error("Filename is too long: %s", path);
2079 strncpy(bname, path, endp - path + 1);
2080 bname[endp - path + 1] = '\0';
2085 linkmap_add(Obj_Entry *obj)
2087 struct link_map *l = &obj->linkmap;
2088 struct link_map *prev;
2090 obj->linkmap.l_name = obj->path;
2091 obj->linkmap.l_addr = obj->mapbase;
2092 obj->linkmap.l_ld = obj->dynamic;
2094 /* GDB needs load offset on MIPS to use the symbols */
2095 obj->linkmap.l_offs = obj->relocbase;
2098 if (r_debug.r_map == NULL) {
2104 * Scan to the end of the list, but not past the entry for the
2105 * dynamic linker, which we want to keep at the very end.
2107 for (prev = r_debug.r_map;
2108 prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap;
2109 prev = prev->l_next)
2112 /* Link in the new entry. */
2114 l->l_next = prev->l_next;
2115 if (l->l_next != NULL)
2116 l->l_next->l_prev = l;
2121 linkmap_delete(Obj_Entry *obj)
2123 struct link_map *l = &obj->linkmap;
2125 if (l->l_prev == NULL) {
2126 if ((r_debug.r_map = l->l_next) != NULL)
2127 l->l_next->l_prev = NULL;
2131 if ((l->l_prev->l_next = l->l_next) != NULL)
2132 l->l_next->l_prev = l->l_prev;
2136 * Function for the debugger to set a breakpoint on to gain control.
2138 * The two parameters allow the debugger to easily find and determine
2139 * what the runtime loader is doing and to whom it is doing it.
2141 * When the loadhook trap is hit (r_debug_state, set at program
2142 * initialization), the arguments can be found on the stack:
2144 * +8 struct link_map *m
2145 * +4 struct r_debug *rd
2149 r_debug_state(struct r_debug* rd, struct link_map *m)
2154 * Get address of the pointer variable in the main program.
2156 static const void **
2157 get_program_var_addr(const char *name)
2159 const Obj_Entry *obj;
2162 hash = elf_hash(name);
2163 for (obj = obj_main; obj != NULL; obj = obj->next) {
2166 if ((def = symlook_obj(name, hash, obj, false)) != NULL) {
2169 addr = (const void **)(obj->relocbase + def->st_value);
2177 * Set a pointer variable in the main program to the given value. This
2178 * is used to set key variables such as "environ" before any of the
2179 * init functions are called.
2182 set_program_var(const char *name, const void *value)
2186 if ((addr = get_program_var_addr(name)) != NULL) {
2187 dbg("\"%s\": *%p <-- %p", name, addr, value);
2193 * Given a symbol name in a referencing object, find the corresponding
2194 * definition of the symbol. Returns a pointer to the symbol, or NULL if
2195 * no definition was found. Returns a pointer to the Obj_Entry of the
2196 * defining object via the reference parameter DEFOBJ_OUT.
2198 static const Elf_Sym *
2199 symlook_default(const char *name, unsigned long hash,
2200 const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt)
2204 const Elf_Sym *symp;
2205 const Obj_Entry *obj;
2206 const Obj_Entry *defobj;
2207 const Objlist_Entry *elm;
2210 donelist_init(&donelist);
2212 /* Look first in the referencing object if linked symbolically. */
2213 if (refobj->symbolic && !donelist_check(&donelist, refobj)) {
2214 symp = symlook_obj(name, hash, refobj, in_plt);
2221 /* Search all objects loaded at program start up. */
2222 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2223 symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist);
2225 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2231 /* Search all DAGs whose roots are RTLD_GLOBAL objects. */
2232 STAILQ_FOREACH(elm, &list_global, link) {
2233 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2235 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2238 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2244 /* Search all dlopened DAGs containing the referencing object. */
2245 STAILQ_FOREACH(elm, &refobj->dldags, link) {
2246 if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
2248 symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
2251 (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
2258 * Search the dynamic linker itself, and possibly resolve the
2259 * symbol from there. This is how the application links to
2260 * dynamic linker services such as dlopen. Only the values listed
2261 * in the "exports" array can be resolved from the dynamic linker.
2263 if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
2264 symp = symlook_obj(name, hash, &obj_rtld, in_plt);
2265 if (symp != NULL && is_exported(symp)) {
2272 *defobj_out = defobj;
2276 static const Elf_Sym *
2277 symlook_list(const char *name, unsigned long hash, Objlist *objlist,
2278 const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)
2280 const Elf_Sym *symp;
2282 const Obj_Entry *defobj;
2283 const Objlist_Entry *elm;
2287 STAILQ_FOREACH(elm, objlist, link) {
2288 if (donelist_check(dlp, elm->obj))
2290 if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) {
2291 if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) {
2294 if (ELF_ST_BIND(def->st_info) != STB_WEAK)
2300 *defobj_out = defobj;
2305 * Search the symbol table of a single shared object for a symbol of
2306 * the given name. Returns a pointer to the symbol, or NULL if no
2307 * definition was found.
2309 * The symbol's hash value is passed in for efficiency reasons; that
2310 * eliminates many recomputations of the hash value.
2313 symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj,
2316 if (obj->buckets != NULL) {
2317 unsigned long symnum = obj->buckets[hash % obj->nbuckets];
2319 while (symnum != STN_UNDEF) {
2320 const Elf_Sym *symp;
2323 if (symnum >= obj->nchains)
2324 return NULL; /* Bad object */
2325 symp = obj->symtab + symnum;
2326 strp = obj->strtab + symp->st_name;
2328 if (name[0] == strp[0] && strcmp(name, strp) == 0)
2329 return symp->st_shndx != SHN_UNDEF ||
2330 (!in_plt && symp->st_value != 0 &&
2331 ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL;
2333 symnum = obj->chains[symnum];
2340 trace_loaded_objects(Obj_Entry *obj)
2342 char *fmt1, *fmt2, *fmt, *main_local, *list_containers;
2345 if ((main_local = getenv(LD_ "TRACE_LOADED_OBJECTS_PROGNAME")) == NULL)
2348 if ((fmt1 = getenv(LD_ "TRACE_LOADED_OBJECTS_FMT1")) == NULL)
2349 fmt1 = "\t%o => %p (%x)\n";
2351 if ((fmt2 = getenv(LD_ "TRACE_LOADED_OBJECTS_FMT2")) == NULL)
2352 fmt2 = "\t%o (%x)\n";
2354 list_containers = getenv(LD_ "TRACE_LOADED_OBJECTS_ALL");
2356 for (; obj; obj = obj->next) {
2357 Needed_Entry *needed;
2361 if (list_containers && obj->needed != NULL)
2362 printf("%s:\n", obj->path);
2363 for (needed = obj->needed; needed; needed = needed->next) {
2364 if (needed->obj != NULL) {
2365 if (needed->obj->traced && !list_containers)
2367 needed->obj->traced = true;
2368 path = needed->obj->path;
2372 name = (char *)obj->strtab + needed->name;
2373 is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */
2375 fmt = is_lib ? fmt1 : fmt2;
2376 while ((c = *fmt++) != '\0') {
2402 printf("%s", main_local);
2405 printf("%s", obj_main->path);
2412 printf("%d", sodp->sod_major);
2415 printf("%d", sodp->sod_minor);
2422 printf("%p", needed->obj ? needed->obj->mapbase : 0);
2434 * Unload a dlopened object and its dependencies from memory and from
2435 * our data structures. It is assumed that the DAG rooted in the
2436 * object has already been unreferenced, and that the object has a
2437 * reference count of 0.
2440 unload_object(Obj_Entry *root)
2445 assert(root->refcount == 0);
2448 * Pass over the DAG removing unreferenced objects from
2449 * appropriate lists.
2451 unlink_object(root);
2453 /* Unmap all objects that are no longer referenced. */
2454 linkp = &obj_list->next;
2455 while ((obj = *linkp) != NULL) {
2456 if (obj->refcount == 0) {
2457 dbg("unloading \"%s\"", obj->path);
2458 munmap(obj->mapbase, obj->mapsize);
2459 linkmap_delete(obj);
2470 unlink_object(Obj_Entry *root)
2474 if (root->refcount == 0) {
2475 /* Remove the object from the RTLD_GLOBAL list. */
2476 objlist_remove(&list_global, root);
2478 /* Remove the object from all objects' DAG lists. */
2479 STAILQ_FOREACH(elm, &root->dagmembers , link) {
2480 objlist_remove(&elm->obj->dldags, root);
2481 if (elm->obj != root)
2482 unlink_object(elm->obj);
2488 ref_dag(Obj_Entry *root)
2492 STAILQ_FOREACH(elm, &root->dagmembers , link)
2493 elm->obj->refcount++;
2497 unref_dag(Obj_Entry *root)
2501 STAILQ_FOREACH(elm, &root->dagmembers , link)
2502 elm->obj->refcount--;
2506 * Common code for MD __tls_get_addr().
2509 tls_get_addr_common(Elf_Addr** dtvp, int index, size_t offset)
2511 Elf_Addr* dtv = *dtvp;
2514 /* Check dtv generation in case new modules have arrived */
2515 if (dtv[0] != tls_dtv_generation) {
2519 lockstate = wlock_acquire(rtld_bind_lock);
2520 newdtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr));
2522 if (to_copy > tls_max_index)
2523 to_copy = tls_max_index;
2524 memcpy(&newdtv[2], &dtv[2], to_copy * sizeof(Elf_Addr));
2525 newdtv[0] = tls_dtv_generation;
2526 newdtv[1] = tls_max_index;
2528 wlock_release(rtld_bind_lock, lockstate);
2532 /* Dynamically allocate module TLS if necessary */
2533 if (!dtv[index + 1]) {
2534 /* Signal safe, wlock will block out signals. */
2535 lockstate = wlock_acquire(rtld_bind_lock);
2536 if (!dtv[index + 1])
2537 dtv[index + 1] = (Elf_Addr)allocate_module_tls(index);
2538 wlock_release(rtld_bind_lock, lockstate);
2540 return (void*) (dtv[index + 1] + offset);
2543 /* XXX not sure what variants to use for arm. */
2545 #if defined(__ia64__) || defined(__alpha__) || defined(__powerpc__)
2548 * Allocate Static TLS using the Variant I method.
2551 allocate_tls(Obj_Entry *objs, void *oldtls, size_t tcbsize, size_t tcbalign)
2556 Elf_Addr *dtv, *olddtv;
2560 size = tls_static_space;
2563 dtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr));
2565 *(Elf_Addr**) tls = dtv;
2567 dtv[0] = tls_dtv_generation;
2568 dtv[1] = tls_max_index;
2572 * Copy the static TLS block over whole.
2574 memcpy(tls + tcbsize, oldtls + tcbsize, tls_static_space - tcbsize);
2577 * If any dynamic TLS blocks have been created tls_get_addr(),
2580 olddtv = *(Elf_Addr**) oldtls;
2581 for (i = 0; i < olddtv[1]; i++) {
2582 if (olddtv[i+2] < (Elf_Addr)oldtls ||
2583 olddtv[i+2] > (Elf_Addr)oldtls + tls_static_space) {
2584 dtv[i+2] = olddtv[i+2];
2590 * We assume that all tls blocks are allocated with the same
2591 * size and alignment.
2593 free_tls(oldtls, tcbsize, tcbalign);
2595 for (obj = objs; obj; obj = obj->next) {
2596 if (obj->tlsoffset) {
2597 addr = (Elf_Addr)tls + obj->tlsoffset;
2598 memset((void*) (addr + obj->tlsinitsize),
2599 0, obj->tlssize - obj->tlsinitsize);
2601 memcpy((void*) addr, obj->tlsinit,
2603 dtv[obj->tlsindex + 1] = addr;
2612 free_tls(void *tls, size_t tcbsize, size_t tcbalign)
2617 Elf_Addr tlsstart, tlsend;
2620 * Figure out the size of the initial TLS block so that we can
2621 * find stuff which __tls_get_addr() allocated dynamically.
2623 size = tls_static_space;
2625 dtv = ((Elf_Addr**)tls)[0];
2627 tlsstart = (Elf_Addr) tls;
2628 tlsend = tlsstart + size;
2629 for (i = 0; i < dtvsize; i++) {
2630 if (dtv[i+2] && (dtv[i+2] < tlsstart || dtv[i+2] > tlsend)) {
2631 free((void*) dtv[i+2]);
2635 free((void*) tlsstart);
2640 #if defined(__i386__) || defined(__amd64__) || defined(__sparc64__) || \
2644 * Allocate Static TLS using the Variant II method.
2647 allocate_tls(Obj_Entry *objs, void *oldtls, size_t tcbsize, size_t tcbalign)
2652 Elf_Addr *dtv, *olddtv;
2653 Elf_Addr segbase, oldsegbase, addr;
2656 size = round(tls_static_space, tcbalign);
2658 assert(tcbsize >= 2*sizeof(Elf_Addr));
2659 tls = malloc(size + tcbsize);
2660 dtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr));
2662 segbase = (Elf_Addr)(tls + size);
2663 ((Elf_Addr*)segbase)[0] = segbase;
2664 ((Elf_Addr*)segbase)[1] = (Elf_Addr) dtv;
2666 dtv[0] = tls_dtv_generation;
2667 dtv[1] = tls_max_index;
2671 * Copy the static TLS block over whole.
2673 oldsegbase = (Elf_Addr) oldtls;
2674 memcpy((void *)(segbase - tls_static_space),
2675 (const void *)(oldsegbase - tls_static_space),
2679 * If any dynamic TLS blocks have been created tls_get_addr(),
2682 olddtv = ((Elf_Addr**)oldsegbase)[1];
2683 for (i = 0; i < olddtv[1]; i++) {
2684 if (olddtv[i+2] < oldsegbase - size || olddtv[i+2] > oldsegbase) {
2685 dtv[i+2] = olddtv[i+2];
2691 * We assume that this block was the one we created with
2692 * allocate_initial_tls().
2694 free_tls(oldtls, 2*sizeof(Elf_Addr), sizeof(Elf_Addr));
2696 for (obj = objs; obj; obj = obj->next) {
2697 if (obj->tlsoffset) {
2698 addr = segbase - obj->tlsoffset;
2699 memset((void*) (addr + obj->tlsinitsize),
2700 0, obj->tlssize - obj->tlsinitsize);
2702 memcpy((void*) addr, obj->tlsinit, obj->tlsinitsize);
2703 dtv[obj->tlsindex + 1] = addr;
2708 return (void*) segbase;
2712 free_tls(void *tls, size_t tcbsize, size_t tcbalign)
2717 Elf_Addr tlsstart, tlsend;
2720 * Figure out the size of the initial TLS block so that we can
2721 * find stuff which ___tls_get_addr() allocated dynamically.
2723 size = round(tls_static_space, tcbalign);
2725 dtv = ((Elf_Addr**)tls)[1];
2727 tlsend = (Elf_Addr) tls;
2728 tlsstart = tlsend - size;
2729 for (i = 0; i < dtvsize; i++) {
2730 if (dtv[i+2] && (dtv[i+2] < tlsstart || dtv[i+2] > tlsend)) {
2731 free((void*) dtv[i+2]);
2735 free((void*) tlsstart);
2741 * Allocate TLS block for module with given index.
2744 allocate_module_tls(int index)
2749 for (obj = obj_list; obj; obj = obj->next) {
2750 if (obj->tlsindex == index)
2754 _rtld_error("Can't find module with TLS index %d", index);
2758 p = malloc(obj->tlssize);
2759 memcpy(p, obj->tlsinit, obj->tlsinitsize);
2760 memset(p + obj->tlsinitsize, 0, obj->tlssize - obj->tlsinitsize);
2766 allocate_tls_offset(Obj_Entry *obj)
2773 if (obj->tlssize == 0) {
2774 obj->tls_done = true;
2778 if (obj->tlsindex == 1)
2779 off = calculate_first_tls_offset(obj->tlssize, obj->tlsalign);
2781 off = calculate_tls_offset(tls_last_offset, tls_last_size,
2782 obj->tlssize, obj->tlsalign);
2785 * If we have already fixed the size of the static TLS block, we
2786 * must stay within that size. When allocating the static TLS, we
2787 * leave a small amount of space spare to be used for dynamically
2788 * loading modules which use static TLS.
2790 if (tls_static_space) {
2791 if (calculate_tls_end(off, obj->tlssize) > tls_static_space)
2795 tls_last_offset = obj->tlsoffset = off;
2796 tls_last_size = obj->tlssize;
2797 obj->tls_done = true;
2803 free_tls_offset(Obj_Entry *obj)
2805 #if defined(__i386__) || defined(__amd64__) || defined(__sparc64__) || \
2808 * If we were the last thing to allocate out of the static TLS
2809 * block, we give our space back to the 'allocator'. This is a
2810 * simplistic workaround to allow libGL.so.1 to be loaded and
2811 * unloaded multiple times. We only handle the Variant II
2812 * mechanism for now - this really needs a proper allocator.
2814 if (calculate_tls_end(obj->tlsoffset, obj->tlssize)
2815 == calculate_tls_end(tls_last_offset, tls_last_size)) {
2816 tls_last_offset -= obj->tlssize;
2823 _rtld_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign)
2828 lockstate = wlock_acquire(rtld_bind_lock);
2829 ret = allocate_tls(obj_list, oldtls, tcbsize, tcbalign);
2830 wlock_release(rtld_bind_lock, lockstate);
2835 _rtld_free_tls(void *tcb, size_t tcbsize, size_t tcbalign)
2839 lockstate = wlock_acquire(rtld_bind_lock);
2840 free_tls(tcb, tcbsize, tcbalign);
2841 wlock_release(rtld_bind_lock, lockstate);