/*- * Copyright 1996, 1997, 1998, 1999, 2000 John D. Polstra. * Copyright 2003 Alexander Kabaev . * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * $FreeBSD: src/libexec/rtld-elf/rtld.c,v 1.43.2.15 2003/02/20 20:42:46 kan Exp $ * $DragonFly: src/libexec/rtld-elf/rtld.c,v 1.27 2007/02/22 13:15:55 corecode Exp $ */ /* * Dynamic linker for ELF. * * John Polstra . */ #ifndef __GNUC__ #error "GCC is needed to compile this file" #endif #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "debug.h" #include "rtld.h" #define PATH_RTLD "/usr/libexec/ld-elf.so.2" #define LD_ARY_CACHE 16 /* Types. */ typedef void (*func_ptr_type)(); typedef void * (*path_enum_proc) (const char *path, size_t len, void *arg); /* * This structure provides a reentrant way to keep a list of objects and * check which ones have already been processed in some way. */ typedef struct Struct_DoneList { const Obj_Entry **objs; /* Array of object pointers */ unsigned int num_alloc; /* Allocated size of the array */ unsigned int num_used; /* Number of array slots used */ } DoneList; /* * Function declarations. */ static void die(void); static void digest_dynamic(Obj_Entry *, int); static const char *_getenv_ld(const char *id); static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *); static Obj_Entry *dlcheck(void *); static int do_search_info(const Obj_Entry *obj, int, struct dl_serinfo *); static bool donelist_check(DoneList *, const Obj_Entry *); static void errmsg_restore(char *); static char *errmsg_save(void); static void *fill_search_info(const char *, size_t, void *); static char *find_library(const char *, const Obj_Entry *); static Obj_Entry *find_object(const char *); static Obj_Entry *find_object2(const char *, int *, struct stat *); static const char *gethints(void); static void init_dag(Obj_Entry *); static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *); static void init_rtld(caddr_t); static void initlist_add_neededs(Needed_Entry *needed, Objlist *list); static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list); static bool is_exported(const Elf_Sym *); static void linkmap_add(Obj_Entry *); static void linkmap_delete(Obj_Entry *); static int load_needed_objects(Obj_Entry *); static int load_preload_objects(void); static Obj_Entry *load_object(char *); static void lock_check(void); static Obj_Entry *obj_from_addr(const void *); static void objlist_call_fini(Objlist *); static void objlist_call_init(Objlist *); static void objlist_clear(Objlist *); static Objlist_Entry *objlist_find(Objlist *, const Obj_Entry *); static void objlist_init(Objlist *); static void objlist_push_head(Objlist *, Obj_Entry *); static void objlist_push_tail(Objlist *, Obj_Entry *); static void objlist_remove(Objlist *, Obj_Entry *); static void objlist_remove_unref(Objlist *); static void *path_enumerate(const char *, path_enum_proc, void *); static int relocate_objects(Obj_Entry *, bool, Obj_Entry *); static int rtld_dirname(const char *, char *); static void rtld_exit(void); static char *search_library_path(const char *, const char *); static const void **get_program_var_addr(const char *name); static void set_program_var(const char *, const void *); static const Elf_Sym *symlook_default(const char *, unsigned long hash, const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt); static const Elf_Sym *symlook_list(const char *, unsigned long, const Objlist *, const Obj_Entry **, bool in_plt, DoneList *); static const Elf_Sym *symlook_needed(const char *, unsigned long, const Needed_Entry *, const Obj_Entry **, bool in_plt, DoneList *); static void trace_loaded_objects(Obj_Entry *obj); static void unlink_object(Obj_Entry *); static void unload_object(Obj_Entry *); static void unref_dag(Obj_Entry *); void r_debug_state(struct r_debug*, struct link_map*); /* * Data declarations. */ static char *error_message; /* Message for dlerror(), or NULL */ struct r_debug r_debug; /* for GDB; */ static bool trust; /* False for setuid and setgid programs */ static const char *ld_bind_now; /* Environment variable for immediate binding */ static const char *ld_debug; /* Environment variable for debugging */ static const char *ld_library_path; /* Environment variable for search path */ static char *ld_preload; /* Environment variable for libraries to load first */ static const char *ld_tracing; /* Called from ldd(1) to print libs */ static Obj_Entry *obj_list; /* Head of linked list of shared objects */ static Obj_Entry **obj_tail; /* Link field of last object in list */ static Obj_Entry **preload_tail; static Obj_Entry *obj_main; /* The main program shared object */ static Obj_Entry obj_rtld; /* The dynamic linker shared object */ static unsigned int obj_count; /* Number of objects in obj_list */ static int ld_resident; /* Non-zero if resident */ static const char *ld_ary[LD_ARY_CACHE]; static int ld_index; static Objlist initlist; static Objlist list_global = /* Objects dlopened with RTLD_GLOBAL */ STAILQ_HEAD_INITIALIZER(list_global); static Objlist list_main = /* Objects loaded at program startup */ STAILQ_HEAD_INITIALIZER(list_main); static Objlist list_fini = /* Objects needing fini() calls */ STAILQ_HEAD_INITIALIZER(list_fini); static LockInfo lockinfo; static Elf_Sym sym_zero; /* For resolving undefined weak refs. */ #define GDB_STATE(s,m) r_debug.r_state = s; r_debug_state(&r_debug,m); extern Elf_Dyn _DYNAMIC; #pragma weak _DYNAMIC /* * These are the functions the dynamic linker exports to application * programs. They are the only symbols the dynamic linker is willing * to export from itself. */ static func_ptr_type exports[] = { (func_ptr_type) &_rtld_error, (func_ptr_type) &dlclose, (func_ptr_type) &dlerror, (func_ptr_type) &dlopen, (func_ptr_type) &dlsym, (func_ptr_type) &dladdr, (func_ptr_type) &dlinfo, #ifdef __i386__ (func_ptr_type) &___tls_get_addr, #endif (func_ptr_type) &__tls_get_addr, (func_ptr_type) &__tls_get_addr_tcb, (func_ptr_type) &_rtld_allocate_tls, (func_ptr_type) &_rtld_free_tls, (func_ptr_type) &_rtld_call_init, NULL }; /* * Global declarations normally provided by crt1. The dynamic linker is * not built with crt1, so we have to provide them ourselves. */ char *__progname; char **environ; /* * Globals to control TLS allocation. */ size_t tls_last_offset; /* Static TLS offset of last module */ size_t tls_last_size; /* Static TLS size of last module */ size_t tls_static_space; /* Static TLS space allocated */ int tls_dtv_generation = 1; /* Used to detect when dtv size changes */ int tls_max_index = 1; /* Largest module index allocated */ /* * Fill in a DoneList with an allocation large enough to hold all of * the currently-loaded objects. Keep this as a macro since it calls * alloca and we want that to occur within the scope of the caller. */ #define donelist_init(dlp) \ ((dlp)->objs = alloca(obj_count * sizeof (dlp)->objs[0]), \ assert((dlp)->objs != NULL), \ (dlp)->num_alloc = obj_count, \ (dlp)->num_used = 0) static __inline void rlock_acquire(void) { lockinfo.rlock_acquire(lockinfo.thelock); atomic_incr_int(&lockinfo.rcount); lock_check(); } static __inline void wlock_acquire(void) { lockinfo.wlock_acquire(lockinfo.thelock); atomic_incr_int(&lockinfo.wcount); lock_check(); } static __inline void rlock_release(void) { atomic_decr_int(&lockinfo.rcount); lockinfo.rlock_release(lockinfo.thelock); } static __inline void wlock_release(void) { atomic_decr_int(&lockinfo.wcount); lockinfo.wlock_release(lockinfo.thelock); } /* * Main entry point for dynamic linking. The first argument is the * stack pointer. The stack is expected to be laid out as described * in the SVR4 ABI specification, Intel 386 Processor Supplement. * Specifically, the stack pointer points to a word containing * ARGC. Following that in the stack is a null-terminated sequence * of pointers to argument strings. Then comes a null-terminated * sequence of pointers to environment strings. Finally, there is a * sequence of "auxiliary vector" entries. * * The second argument points to a place to store the dynamic linker's * exit procedure pointer and the third to a place to store the main * program's object. * * The return value is the main program's entry point. */ func_ptr_type _rtld(Elf_Addr *sp, func_ptr_type *exit_proc, Obj_Entry **objp) { Elf_Auxinfo *aux_info[AT_COUNT]; int i; int argc; char **argv; char **env; Elf_Auxinfo *aux; Elf_Auxinfo *auxp; const char *argv0; Objlist_Entry *entry; Obj_Entry *obj; ld_index = 0; /* don't use old env cache in case we are resident */ /* * On entry, the dynamic linker itself has not been relocated yet. * Be very careful not to reference any global data until after * init_rtld has returned. It is OK to reference file-scope statics * and string constants, and to call static and global functions. */ /* Find the auxiliary vector on the stack. */ argc = *sp++; argv = (char **) sp; sp += argc + 1; /* Skip over arguments and NULL terminator */ env = (char **) sp; /* * If we aren't already resident we have to dig out some more info. * Note that auxinfo does not exist when we are resident. */ if (ld_resident == 0) { while (*sp++ != 0) /* Skip over environment, and NULL terminator */ ; aux = (Elf_Auxinfo *) sp; /* Digest the auxiliary vector. */ for (i = 0; i < AT_COUNT; i++) aux_info[i] = NULL; for (auxp = aux; auxp->a_type != AT_NULL; auxp++) { if (auxp->a_type < AT_COUNT) aux_info[auxp->a_type] = auxp; } /* Initialize and relocate ourselves. */ assert(aux_info[AT_BASE] != NULL); init_rtld((caddr_t) aux_info[AT_BASE]->a_un.a_ptr); } __progname = obj_rtld.path; argv0 = argv[0] != NULL ? argv[0] : "(null)"; environ = env; trust = (geteuid() == getuid()) && (getegid() == getgid()); ld_bind_now = _getenv_ld("LD_BIND_NOW"); if (trust) { ld_debug = _getenv_ld("LD_DEBUG"); ld_library_path = _getenv_ld("LD_LIBRARY_PATH"); ld_preload = (char *)_getenv_ld("LD_PRELOAD"); } ld_tracing = _getenv_ld("LD_TRACE_LOADED_OBJECTS"); if (ld_debug != NULL && *ld_debug != '\0') debug = 1; dbg("%s is initialized, base address = %p", __progname, (caddr_t) aux_info[AT_BASE]->a_un.a_ptr); dbg("RTLD dynamic = %p", obj_rtld.dynamic); dbg("RTLD pltgot = %p", obj_rtld.pltgot); /* * If we are resident we can skip work that we have already done. * Note that the stack is reset and there is no Elf_Auxinfo * when running from a resident image, and the static globals setup * between here and resident_skip will have already been setup. */ if (ld_resident) goto resident_skip1; /* * Load the main program, or process its program header if it is * already loaded. */ if (aux_info[AT_EXECFD] != NULL) { /* Load the main program. */ int fd = aux_info[AT_EXECFD]->a_un.a_val; dbg("loading main program"); obj_main = map_object(fd, argv0, NULL); close(fd); if (obj_main == NULL) die(); } else { /* Main program already loaded. */ const Elf_Phdr *phdr; int phnum; caddr_t entry; dbg("processing main program's program header"); assert(aux_info[AT_PHDR] != NULL); phdr = (const Elf_Phdr *) aux_info[AT_PHDR]->a_un.a_ptr; assert(aux_info[AT_PHNUM] != NULL); phnum = aux_info[AT_PHNUM]->a_un.a_val; assert(aux_info[AT_PHENT] != NULL); assert(aux_info[AT_PHENT]->a_un.a_val == sizeof(Elf_Phdr)); assert(aux_info[AT_ENTRY] != NULL); entry = (caddr_t) aux_info[AT_ENTRY]->a_un.a_ptr; if ((obj_main = digest_phdr(phdr, phnum, entry, argv0)) == NULL) die(); } obj_main->path = xstrdup(argv0); obj_main->mainprog = true; /* * Get the actual dynamic linker pathname from the executable if * possible. (It should always be possible.) That ensures that * gdb will find the right dynamic linker even if a non-standard * one is being used. */ if (obj_main->interp != NULL && strcmp(obj_main->interp, obj_rtld.path) != 0) { free(obj_rtld.path); obj_rtld.path = xstrdup(obj_main->interp); __progname = obj_rtld.path; } digest_dynamic(obj_main, 0); linkmap_add(obj_main); linkmap_add(&obj_rtld); /* Link the main program into the list of objects. */ *obj_tail = obj_main; obj_tail = &obj_main->next; obj_count++; obj_main->refcount++; /* Make sure we don't call the main program's init and fini functions. */ obj_main->init = obj_main->fini = NULL; /* Initialize a fake symbol for resolving undefined weak references. */ sym_zero.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE); sym_zero.st_shndx = SHN_ABS; dbg("loading LD_PRELOAD libraries"); if (load_preload_objects() == -1) die(); preload_tail = obj_tail; dbg("loading needed objects"); if (load_needed_objects(obj_main) == -1) die(); /* Make a list of all objects loaded at startup. */ for (obj = obj_list; obj != NULL; obj = obj->next) objlist_push_tail(&list_main, obj); resident_skip1: if (ld_tracing) { /* We're done */ trace_loaded_objects(obj_main); exit(0); } if (ld_resident) /* XXX clean this up! */ goto resident_skip2; if (getenv("LD_DUMP_REL_PRE") != NULL) { dump_relocations(obj_main); exit (0); } /* setup TLS for main thread */ dbg("initializing initial thread local storage"); STAILQ_FOREACH(entry, &list_main, link) { /* * Allocate all the initial objects out of the static TLS * block even if they didn't ask for it. */ allocate_tls_offset(entry->obj); } tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA; /* * Do not try to allocate the TLS here, let libc do it itself. * (crt1 for the program will call _init_tls()) */ if (relocate_objects(obj_main, ld_bind_now != NULL && *ld_bind_now != '\0', &obj_rtld) == -1) die(); dbg("doing copy relocations"); if (do_copy_relocations(obj_main) == -1) die(); resident_skip2: if (_getenv_ld("LD_RESIDENT_UNREGISTER_NOW")) { if (exec_sys_unregister(-1) < 0) { dbg("exec_sys_unregister failed %d\n", errno); exit(errno); } dbg("exec_sys_unregister success\n"); exit(0); } if (getenv("LD_DUMP_REL_POST") != NULL) { dump_relocations(obj_main); exit (0); } dbg("initializing key program variables"); set_program_var("__progname", argv[0] != NULL ? basename(argv[0]) : ""); set_program_var("environ", env); if (_getenv_ld("LD_RESIDENT_REGISTER_NOW")) { extern void resident_start(void); ld_resident = 1; if (exec_sys_register(resident_start) < 0) { dbg("exec_sys_register failed %d\n", errno); exit(errno); } dbg("exec_sys_register success\n"); exit(0); } dbg("initializing thread locks"); lockdflt_init(&lockinfo); lockinfo.thelock = lockinfo.lock_create(lockinfo.context); /* Make a list of init functions to call. */ objlist_init(&initlist); initlist_add_objects(obj_list, preload_tail, &initlist); r_debug_state(NULL, &obj_main->linkmap); /* say hello to gdb! */ /* * Do NOT call the initlist here, give libc a chance to set up * the initial TLS segment. crt1 will then call _rtld_call_init(). */ dbg("transferring control to program entry point = %p", obj_main->entry); /* Return the exit procedure and the program entry point. */ *exit_proc = rtld_exit; *objp = obj_main; return (func_ptr_type) obj_main->entry; } /* * Call the initialization list for dynamically loaded libraries. * (called from crt1.c). */ void _rtld_call_init(void) { objlist_call_init(&initlist); wlock_acquire(); objlist_clear(&initlist); wlock_release(); } Elf_Addr _rtld_bind(Obj_Entry *obj, Elf_Word reloff) { const Elf_Rel *rel; const Elf_Sym *def; const Obj_Entry *defobj; Elf_Addr *where; Elf_Addr target; rlock_acquire(); if (obj->pltrel) rel = (const Elf_Rel *) ((caddr_t) obj->pltrel + reloff); else rel = (const Elf_Rel *) ((caddr_t) obj->pltrela + reloff); where = (Elf_Addr *) (obj->relocbase + rel->r_offset); def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true, NULL); if (def == NULL) die(); target = (Elf_Addr)(defobj->relocbase + def->st_value); dbg("\"%s\" in \"%s\" ==> %p in \"%s\"", defobj->strtab + def->st_name, basename(obj->path), (void *)target, basename(defobj->path)); reloc_jmpslot(where, target); rlock_release(); return target; } /* * Error reporting function. Use it like printf. If formats the message * into a buffer, and sets things up so that the next call to dlerror() * will return the message. */ void _rtld_error(const char *fmt, ...) { static char buf[512]; va_list ap; va_start(ap, fmt); vsnprintf(buf, sizeof buf, fmt, ap); error_message = buf; va_end(ap); } /* * Return a dynamically-allocated copy of the current error message, if any. */ static char * errmsg_save(void) { return error_message == NULL ? NULL : xstrdup(error_message); } /* * Restore the current error message from a copy which was previously saved * by errmsg_save(). The copy is freed. */ static void errmsg_restore(char *saved_msg) { if (saved_msg == NULL) error_message = NULL; else { _rtld_error("%s", saved_msg); free(saved_msg); } } const char * basename(const char *name) { const char *p = strrchr(name, '/'); return p != NULL ? p + 1 : name; } static void die(void) { const char *msg = dlerror(); if (msg == NULL) msg = "Fatal error"; errx(1, "%s", msg); } /* * Process a shared object's DYNAMIC section, and save the important * information in its Obj_Entry structure. */ static void digest_dynamic(Obj_Entry *obj, int early) { const Elf_Dyn *dynp; Needed_Entry **needed_tail = &obj->needed; const Elf_Dyn *dyn_rpath = NULL; int plttype = DT_REL; for (dynp = obj->dynamic; dynp->d_tag != DT_NULL; dynp++) { switch (dynp->d_tag) { case DT_REL: obj->rel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_RELSZ: obj->relsize = dynp->d_un.d_val; break; case DT_RELENT: assert(dynp->d_un.d_val == sizeof(Elf_Rel)); break; case DT_JMPREL: obj->pltrel = (const Elf_Rel *) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_PLTRELSZ: obj->pltrelsize = dynp->d_un.d_val; break; case DT_RELA: obj->rela = (const Elf_Rela *) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_RELASZ: obj->relasize = dynp->d_un.d_val; break; case DT_RELAENT: assert(dynp->d_un.d_val == sizeof(Elf_Rela)); break; case DT_PLTREL: plttype = dynp->d_un.d_val; assert(dynp->d_un.d_val == DT_REL || plttype == DT_RELA); break; case DT_SYMTAB: obj->symtab = (const Elf_Sym *) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_SYMENT: assert(dynp->d_un.d_val == sizeof(Elf_Sym)); break; case DT_STRTAB: obj->strtab = (const char *) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_STRSZ: obj->strsize = dynp->d_un.d_val; break; case DT_HASH: { const Elf_Addr *hashtab = (const Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); obj->nbuckets = hashtab[0]; obj->nchains = hashtab[1]; obj->buckets = hashtab + 2; obj->chains = obj->buckets + obj->nbuckets; } break; case DT_NEEDED: if (!obj->rtld) { Needed_Entry *nep = NEW(Needed_Entry); nep->name = dynp->d_un.d_val; nep->obj = NULL; nep->next = NULL; *needed_tail = nep; needed_tail = &nep->next; } break; case DT_PLTGOT: obj->pltgot = (Elf_Addr *) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_TEXTREL: obj->textrel = true; break; case DT_SYMBOLIC: obj->symbolic = true; break; case DT_RPATH: case DT_RUNPATH: /* XXX: process separately */ /* * We have to wait until later to process this, because we * might not have gotten the address of the string table yet. */ dyn_rpath = dynp; break; case DT_SONAME: /* Not used by the dynamic linker. */ break; case DT_INIT: obj->init = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_FINI: obj->fini = (InitFunc) (obj->relocbase + dynp->d_un.d_ptr); break; case DT_DEBUG: /* XXX - not implemented yet */ if (!early) dbg("Filling in DT_DEBUG entry"); ((Elf_Dyn*)dynp)->d_un.d_ptr = (Elf_Addr) &r_debug; break; case DT_FLAGS: if (dynp->d_un.d_val & DF_ORIGIN) { obj->origin_path = xmalloc(PATH_MAX); if (rtld_dirname(obj->path, obj->origin_path) == -1) die(); } if (dynp->d_un.d_val & DF_SYMBOLIC) obj->symbolic = true; if (dynp->d_un.d_val & DF_TEXTREL) obj->textrel = true; if (dynp->d_un.d_val & DF_BIND_NOW) obj->bind_now = true; if (dynp->d_un.d_val & DF_STATIC_TLS) ; break; default: if (!early) dbg("Ignoring d_tag %d = %#x", dynp->d_tag, dynp->d_tag); break; } } obj->traced = false; if (plttype == DT_RELA) { obj->pltrela = (const Elf_Rela *) obj->pltrel; obj->pltrel = NULL; obj->pltrelasize = obj->pltrelsize; obj->pltrelsize = 0; } if (dyn_rpath != NULL) obj->rpath = obj->strtab + dyn_rpath->d_un.d_val; } /* * Process a shared object's program header. This is used only for the * main program, when the kernel has already loaded the main program * into memory before calling the dynamic linker. It creates and * returns an Obj_Entry structure. */ static Obj_Entry * digest_phdr(const Elf_Phdr *phdr, int phnum, caddr_t entry, const char *path) { Obj_Entry *obj; const Elf_Phdr *phlimit = phdr + phnum; const Elf_Phdr *ph; int nsegs = 0; obj = obj_new(); for (ph = phdr; ph < phlimit; ph++) { switch (ph->p_type) { case PT_PHDR: if ((const Elf_Phdr *)ph->p_vaddr != phdr) { _rtld_error("%s: invalid PT_PHDR", path); return NULL; } obj->phdr = (const Elf_Phdr *) ph->p_vaddr; obj->phsize = ph->p_memsz; break; case PT_INTERP: obj->interp = (const char *) ph->p_vaddr; break; case PT_LOAD: if (nsegs == 0) { /* First load segment */ obj->vaddrbase = trunc_page(ph->p_vaddr); obj->mapbase = (caddr_t) obj->vaddrbase; obj->relocbase = obj->mapbase - obj->vaddrbase; obj->textsize = round_page(ph->p_vaddr + ph->p_memsz) - obj->vaddrbase; } else { /* Last load segment */ obj->mapsize = round_page(ph->p_vaddr + ph->p_memsz) - obj->vaddrbase; } nsegs++; break; case PT_DYNAMIC: obj->dynamic = (const Elf_Dyn *) ph->p_vaddr; break; case PT_TLS: obj->tlsindex = 1; obj->tlssize = ph->p_memsz; obj->tlsalign = ph->p_align; obj->tlsinitsize = ph->p_filesz; obj->tlsinit = (void*) ph->p_vaddr; break; } } if (nsegs < 1) { _rtld_error("%s: too few PT_LOAD segments", path); return NULL; } obj->entry = entry; return obj; } static Obj_Entry * dlcheck(void *handle) { Obj_Entry *obj; for (obj = obj_list; obj != NULL; obj = obj->next) if (obj == (Obj_Entry *) handle) break; if (obj == NULL || obj->refcount == 0 || obj->dl_refcount == 0) { _rtld_error("Invalid shared object handle %p", handle); return NULL; } return obj; } /* * If the given object is already in the donelist, return true. Otherwise * add the object to the list and return false. */ static bool donelist_check(DoneList *dlp, const Obj_Entry *obj) { unsigned int i; for (i = 0; i < dlp->num_used; i++) if (dlp->objs[i] == obj) return true; /* * Our donelist allocation should always be sufficient. But if * our threads locking isn't working properly, more shared objects * could have been loaded since we allocated the list. That should * never happen, but we'll handle it properly just in case it does. */ if (dlp->num_used < dlp->num_alloc) dlp->objs[dlp->num_used++] = obj; return false; } /* * Hash function for symbol table lookup. Don't even think about changing * this. It is specified by the System V ABI. */ unsigned long elf_hash(const char *name) { const unsigned char *p = (const unsigned char *) name; unsigned long h = 0; unsigned long g; while (*p != '\0') { h = (h << 4) + *p++; if ((g = h & 0xf0000000) != 0) h ^= g >> 24; h &= ~g; } return h; } /* * Find the library with the given name, and return its full pathname. * The returned string is dynamically allocated. Generates an error * message and returns NULL if the library cannot be found. * * If the second argument is non-NULL, then it refers to an already- * loaded shared object, whose library search path will be searched. * * The search order is: * LD_LIBRARY_PATH * rpath in the referencing file * ldconfig hints * /usr/lib */ static char * find_library(const char *name, const Obj_Entry *refobj) { char *pathname; if (strchr(name, '/') != NULL) { /* Hard coded pathname */ if (name[0] != '/' && !trust) { _rtld_error("Absolute pathname required for shared object \"%s\"", name); return NULL; } return xstrdup(name); } dbg(" Searching for \"%s\"", name); if ((pathname = search_library_path(name, ld_library_path)) != NULL || (refobj != NULL && (pathname = search_library_path(name, refobj->rpath)) != NULL) || (pathname = search_library_path(name, gethints())) != NULL || (pathname = search_library_path(name, STANDARD_LIBRARY_PATH)) != NULL) return pathname; if(refobj != NULL && refobj->path != NULL) { _rtld_error("Shared object \"%s\" not found, required by \"%s\"", name, basename(refobj->path)); } else { _rtld_error("Shared object \"%s\" not found", name); } return NULL; } /* * Given a symbol number in a referencing object, find the corresponding * definition of the symbol. Returns a pointer to the symbol, or NULL if * no definition was found. Returns a pointer to the Obj_Entry of the * defining object via the reference parameter DEFOBJ_OUT. */ const Elf_Sym * find_symdef(unsigned long symnum, const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt, SymCache *cache) { const Elf_Sym *ref; const Elf_Sym *def; const Obj_Entry *defobj; const char *name; unsigned long hash; /* * If we have already found this symbol, get the information from * the cache. */ if (symnum >= refobj->nchains) return NULL; /* Bad object */ if (cache != NULL && cache[symnum].sym != NULL) { *defobj_out = cache[symnum].obj; return cache[symnum].sym; } ref = refobj->symtab + symnum; name = refobj->strtab + ref->st_name; defobj = NULL; /* * We don't have to do a full scale lookup if the symbol is local. * We know it will bind to the instance in this load module; to * which we already have a pointer (ie ref). By not doing a lookup, * we not only improve performance, but it also avoids unresolvable * symbols when local symbols are not in the hash table. * * This might occur for TLS module relocations, which simply use * symbol 0. */ if (ELF_ST_BIND(ref->st_info) != STB_LOCAL) { if (ELF_ST_TYPE(ref->st_info) == STT_SECTION) { _rtld_error("%s: Bogus symbol table entry %lu", refobj->path, symnum); } hash = elf_hash(name); def = symlook_default(name, hash, refobj, &defobj, in_plt); } else { def = ref; defobj = refobj; } /* * If we found no definition and the reference is weak, treat the * symbol as having the value zero. */ if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) { def = &sym_zero; defobj = obj_main; } if (def != NULL) { *defobj_out = defobj; /* Record the information in the cache to avoid subsequent lookups. */ if (cache != NULL) { cache[symnum].sym = def; cache[symnum].obj = defobj; } } else _rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name); return def; } /* * Return the search path from the ldconfig hints file, reading it if * necessary. Returns NULL if there are problems with the hints file, * or if the search path there is empty. */ static const char * gethints(void) { static char *hints; if (hints == NULL) { int fd; struct elfhints_hdr hdr; char *p; /* Keep from trying again in case the hints file is bad. */ hints = ""; if ((fd = open(_PATH_ELF_HINTS, O_RDONLY)) == -1) return NULL; if (read(fd, &hdr, sizeof hdr) != sizeof hdr || hdr.magic != ELFHINTS_MAGIC || hdr.version != 1) { close(fd); return NULL; } p = xmalloc(hdr.dirlistlen + 1); if (lseek(fd, hdr.strtab + hdr.dirlist, SEEK_SET) == -1 || read(fd, p, hdr.dirlistlen + 1) != hdr.dirlistlen + 1) { free(p); close(fd); return NULL; } hints = p; close(fd); } return hints[0] != '\0' ? hints : NULL; } static void init_dag(Obj_Entry *root) { DoneList donelist; donelist_init(&donelist); init_dag1(root, root, &donelist); } static void init_dag1(Obj_Entry *root, Obj_Entry *obj, DoneList *dlp) { const Needed_Entry *needed; if (donelist_check(dlp, obj)) return; objlist_push_tail(&obj->dldags, root); objlist_push_tail(&root->dagmembers, obj); for (needed = obj->needed; needed != NULL; needed = needed->next) if (needed->obj != NULL) init_dag1(root, needed->obj, dlp); } /* * Initialize the dynamic linker. The argument is the address at which * the dynamic linker has been mapped into memory. The primary task of * this function is to relocate the dynamic linker. */ static void init_rtld(caddr_t mapbase) { Obj_Entry objtmp; /* Temporary rtld object */ /* * Conjure up an Obj_Entry structure for the dynamic linker. * * The "path" member can't be initialized yet because string constatns * cannot yet be acessed. Below we will set it correctly. */ objtmp.path = NULL; objtmp.rtld = true; objtmp.mapbase = mapbase; #ifdef PIC objtmp.relocbase = mapbase; #endif if (&_DYNAMIC != 0) { objtmp.dynamic = rtld_dynamic(&objtmp); digest_dynamic(&objtmp, 1); assert(objtmp.needed == NULL); assert(!objtmp.textrel); /* * Temporarily put the dynamic linker entry into the object list, so * that symbols can be found. */ relocate_objects(&objtmp, true, &objtmp); } /* Initialize the object list. */ obj_tail = &obj_list; /* Now that non-local variables can be accesses, copy out obj_rtld. */ memcpy(&obj_rtld, &objtmp, sizeof(obj_rtld)); /* Replace the path with a dynamically allocated copy. */ obj_rtld.path = xstrdup(PATH_RTLD); r_debug.r_brk = r_debug_state; r_debug.r_state = RT_CONSISTENT; } /* * Add the init functions from a needed object list (and its recursive * needed objects) to "list". This is not used directly; it is a helper * function for initlist_add_objects(). The write lock must be held * when this function is called. */ static void initlist_add_neededs(Needed_Entry *needed, Objlist *list) { /* Recursively process the successor needed objects. */ if (needed->next != NULL) initlist_add_neededs(needed->next, list); /* Process the current needed object. */ if (needed->obj != NULL) initlist_add_objects(needed->obj, &needed->obj->next, list); } /* * Scan all of the DAGs rooted in the range of objects from "obj" to * "tail" and add their init functions to "list". This recurses over * the DAGs and ensure the proper init ordering such that each object's * needed libraries are initialized before the object itself. At the * same time, this function adds the objects to the global finalization * list "list_fini" in the opposite order. The write lock must be * held when this function is called. */ static void initlist_add_objects(Obj_Entry *obj, Obj_Entry **tail, Objlist *list) { if (obj->init_done) return; obj->init_done = true; /* Recursively process the successor objects. */ if (&obj->next != tail) initlist_add_objects(obj->next, tail, list); /* Recursively process the needed objects. */ if (obj->needed != NULL) initlist_add_neededs(obj->needed, list); /* Add the object to the init list. */ if (obj->init != NULL) objlist_push_tail(list, obj); /* Add the object to the global fini list in the reverse order. */ if (obj->fini != NULL) objlist_push_head(&list_fini, obj); } static bool is_exported(const Elf_Sym *def) { func_ptr_type value; const func_ptr_type *p; value = (func_ptr_type)(obj_rtld.relocbase + def->st_value); for (p = exports; *p != NULL; p++) if (*p == value) return true; return false; } /* * Given a shared object, traverse its list of needed objects, and load * each of them. Returns 0 on success. Generates an error message and * returns -1 on failure. */ static int load_needed_objects(Obj_Entry *first) { Obj_Entry *obj; for (obj = first; obj != NULL; obj = obj->next) { Needed_Entry *needed; for (needed = obj->needed; needed != NULL; needed = needed->next) { const char *name = obj->strtab + needed->name; char *path = find_library(name, obj); needed->obj = NULL; if (path == NULL && !ld_tracing) return -1; if (path) { needed->obj = load_object(path); if (needed->obj == NULL && !ld_tracing) return -1; /* XXX - cleanup */ } } } return 0; } static int load_preload_objects(void) { char *p = ld_preload; static const char delim[] = " \t:;"; if (p == NULL) return NULL; p += strspn(p, delim); while (*p != '\0') { size_t len = strcspn(p, delim); char *path; char savech; savech = p[len]; p[len] = '\0'; if ((path = find_library(p, NULL)) == NULL) return -1; if (load_object(path) == NULL) return -1; /* XXX - cleanup */ p[len] = savech; p += len; p += strspn(p, delim); } return 0; } /* * Returns a pointer to the Obj_Entry for the object with the given path. * Returns NULL if no matching object was found. */ static Obj_Entry * find_object(const char *path) { Obj_Entry *obj; for (obj = obj_list->next; obj != NULL; obj = obj->next) { if (strcmp(obj->path, path) == 0) return(obj); } return(NULL); } /* * Returns a pointer to the Obj_Entry for the object matching device and * inode of the given path. If no matching object was found, the descriptor * is returned in fd. * Returns with obj == NULL && fd == -1 on error. */ static Obj_Entry * find_object2(const char *path, int *fd, struct stat *sb) { Obj_Entry *obj; if ((*fd = open(path, O_RDONLY)) == -1) { _rtld_error("Cannot open \"%s\"", path); return(NULL); } if (fstat(*fd, sb) == -1) { _rtld_error("Cannot fstat \"%s\"", path); close(*fd); *fd = -1; return NULL; } for (obj = obj_list->next; obj != NULL; obj = obj->next) { if (obj->ino == sb->st_ino && obj->dev == sb->st_dev) { close(*fd); break; } } return(obj); } /* * Load a shared object into memory, if it is not already loaded. The * argument must be a string allocated on the heap. This function assumes * responsibility for freeing it when necessary. * * Returns a pointer to the Obj_Entry for the object. Returns NULL * on failure. */ static Obj_Entry * load_object(char *path) { Obj_Entry *obj; int fd = -1; struct stat sb; obj = find_object(path); if (obj != NULL) { obj->refcount++; free(path); return(obj); } obj = find_object2(path, &fd, &sb); if (obj != NULL) { obj->refcount++; free(path); return(obj); } else if (fd == -1) { free(path); return(NULL); } dbg("loading \"%s\"", path); obj = map_object(fd, path, &sb); close(fd); if (obj == NULL) { free(path); return NULL; } obj->path = path; digest_dynamic(obj, 0); *obj_tail = obj; obj_tail = &obj->next; obj_count++; linkmap_add(obj); /* for GDB & dlinfo() */ dbg(" %p .. %p: %s", obj->mapbase, obj->mapbase + obj->mapsize - 1, obj->path); if (obj->textrel) dbg(" WARNING: %s has impure text", obj->path); obj->refcount++; return obj; } /* * Check for locking violations and die if one is found. */ static void lock_check(void) { int rcount, wcount; rcount = lockinfo.rcount; wcount = lockinfo.wcount; assert(rcount >= 0); assert(wcount >= 0); if (wcount > 1 || (wcount != 0 && rcount != 0)) { _rtld_error("Application locking error: %d readers and %d writers" " in dynamic linker. See DLLOCKINIT(3) in manual pages.", rcount, wcount); die(); } } static Obj_Entry * obj_from_addr(const void *addr) { Obj_Entry *obj; for (obj = obj_list; obj != NULL; obj = obj->next) { if (addr < (void *) obj->mapbase) continue; if (addr < (void *) (obj->mapbase + obj->mapsize)) return obj; } return NULL; } /* * Call the finalization functions for each of the objects in "list" * which are unreferenced. All of the objects are expected to have * non-NULL fini functions. */ static void objlist_call_fini(Objlist *list) { Objlist_Entry *elm; char *saved_msg; /* * Preserve the current error message since a fini function might * call into the dynamic linker and overwrite it. */ saved_msg = errmsg_save(); STAILQ_FOREACH(elm, list, link) { if (elm->obj->refcount == 0) { dbg("calling fini function for %s", elm->obj->path); (*elm->obj->fini)(); } } errmsg_restore(saved_msg); } /* * Call the initialization functions for each of the objects in * "list". All of the objects are expected to have non-NULL init * functions. */ static void objlist_call_init(Objlist *list) { Objlist_Entry *elm; char *saved_msg; /* * Preserve the current error message since an init function might * call into the dynamic linker and overwrite it. */ saved_msg = errmsg_save(); STAILQ_FOREACH(elm, list, link) { dbg("calling init function for %s", elm->obj->path); (*elm->obj->init)(); } errmsg_restore(saved_msg); } static void objlist_clear(Objlist *list) { Objlist_Entry *elm; while (!STAILQ_EMPTY(list)) { elm = STAILQ_FIRST(list); STAILQ_REMOVE_HEAD(list, link); free(elm); } } static Objlist_Entry * objlist_find(Objlist *list, const Obj_Entry *obj) { Objlist_Entry *elm; STAILQ_FOREACH(elm, list, link) if (elm->obj == obj) return elm; return NULL; } static void objlist_init(Objlist *list) { STAILQ_INIT(list); } static void objlist_push_head(Objlist *list, Obj_Entry *obj) { Objlist_Entry *elm; elm = NEW(Objlist_Entry); elm->obj = obj; STAILQ_INSERT_HEAD(list, elm, link); } static void objlist_push_tail(Objlist *list, Obj_Entry *obj) { Objlist_Entry *elm; elm = NEW(Objlist_Entry); elm->obj = obj; STAILQ_INSERT_TAIL(list, elm, link); } static void objlist_remove(Objlist *list, Obj_Entry *obj) { Objlist_Entry *elm; if ((elm = objlist_find(list, obj)) != NULL) { STAILQ_REMOVE(list, elm, Struct_Objlist_Entry, link); free(elm); } } /* * Remove all of the unreferenced objects from "list". */ static void objlist_remove_unref(Objlist *list) { Objlist newlist; Objlist_Entry *elm; STAILQ_INIT(&newlist); while (!STAILQ_EMPTY(list)) { elm = STAILQ_FIRST(list); STAILQ_REMOVE_HEAD(list, link); if (elm->obj->refcount == 0) free(elm); else STAILQ_INSERT_TAIL(&newlist, elm, link); } *list = newlist; } /* * Relocate newly-loaded shared objects. The argument is a pointer to * the Obj_Entry for the first such object. All objects from the first * to the end of the list of objects are relocated. Returns 0 on success, * or -1 on failure. */ static int relocate_objects(Obj_Entry *first, bool bind_now, Obj_Entry *rtldobj) { Obj_Entry *obj; for (obj = first; obj != NULL; obj = obj->next) { if (obj != rtldobj) dbg("relocating \"%s\"", obj->path); if (obj->nbuckets == 0 || obj->nchains == 0 || obj->buckets == NULL || obj->symtab == NULL || obj->strtab == NULL) { _rtld_error("%s: Shared object has no run-time symbol table", obj->path); return -1; } if (obj->textrel) { /* There are relocations to the write-protected text segment. */ if (mprotect(obj->mapbase, obj->textsize, PROT_READ|PROT_WRITE|PROT_EXEC) == -1) { _rtld_error("%s: Cannot write-enable text segment: %s", obj->path, strerror(errno)); return -1; } } /* Process the non-PLT relocations. */ if (reloc_non_plt(obj, rtldobj)) return -1; /* * Reprotect the text segment. Make sure it is included in the * core dump since we modified it. This unfortunately causes the * entire text segment to core-out but we don't have much of a * choice. We could try to only reenable core dumps on pages * in which relocations occured but that is likely most of the text * pages anyway, and even that would not work because the rest of * the text pages would wind up as a read-only OBJT_DEFAULT object * (created due to our modifications) backed by the original OBJT_VNODE * object, and the ELF coredump code is currently only able to dump * vnode records for pure vnode-backed mappings, not vnode backings * to memory objects. */ if (obj->textrel) { madvise(obj->mapbase, obj->textsize, MADV_CORE); if (mprotect(obj->mapbase, obj->textsize, PROT_READ|PROT_EXEC) == -1) { _rtld_error("%s: Cannot write-protect text segment: %s", obj->path, strerror(errno)); return -1; } } /* Process the PLT relocations. */ if (reloc_plt(obj) == -1) return -1; /* Relocate the jump slots if we are doing immediate binding. */ if (obj->bind_now || bind_now) if (reloc_jmpslots(obj) == -1) return -1; /* * Set up the magic number and version in the Obj_Entry. These * were checked in the crt1.o from the original ElfKit, so we * set them for backward compatibility. */ obj->magic = RTLD_MAGIC; obj->version = RTLD_VERSION; /* Set the special PLT or GOT entries. */ init_pltgot(obj); } return 0; } /* * Cleanup procedure. It will be called (by the atexit mechanism) just * before the process exits. */ static void rtld_exit(void) { Obj_Entry *obj; dbg("rtld_exit()"); /* Clear all the reference counts so the fini functions will be called. */ for (obj = obj_list; obj != NULL; obj = obj->next) obj->refcount = 0; objlist_call_fini(&list_fini); /* No need to remove the items from the list, since we are exiting. */ } static void * path_enumerate(const char *path, path_enum_proc callback, void *arg) { if (path == NULL) return (NULL); path += strspn(path, ":;"); while (*path != '\0') { size_t len; char *res; len = strcspn(path, ":;"); res = callback(path, len, arg); if (res != NULL) return (res); path += len; path += strspn(path, ":;"); } return (NULL); } struct try_library_args { const char *name; size_t namelen; char *buffer; size_t buflen; }; static void * try_library_path(const char *dir, size_t dirlen, void *param) { struct try_library_args *arg; arg = param; if (*dir == '/' || trust) { char *pathname; if (dirlen + 1 + arg->namelen + 1 > arg->buflen) return (NULL); pathname = arg->buffer; strncpy(pathname, dir, dirlen); pathname[dirlen] = '/'; strcpy(pathname + dirlen + 1, arg->name); dbg(" Trying \"%s\"", pathname); if (access(pathname, F_OK) == 0) { /* We found it */ pathname = xmalloc(dirlen + 1 + arg->namelen + 1); strcpy(pathname, arg->buffer); return (pathname); } } return (NULL); } static char * search_library_path(const char *name, const char *path) { char *p; struct try_library_args arg; if (path == NULL) return NULL; arg.name = name; arg.namelen = strlen(name); arg.buffer = xmalloc(PATH_MAX); arg.buflen = PATH_MAX; p = path_enumerate(path, try_library_path, &arg); free(arg.buffer); return (p); } int dlclose(void *handle) { Obj_Entry *root; wlock_acquire(); root = dlcheck(handle); if (root == NULL) { wlock_release(); return -1; } /* Unreference the object and its dependencies. */ root->dl_refcount--; unref_dag(root); if (root->refcount == 0) { /* * The object is no longer referenced, so we must unload it. * First, call the fini functions with no locks held. */ wlock_release(); objlist_call_fini(&list_fini); wlock_acquire(); objlist_remove_unref(&list_fini); /* Finish cleaning up the newly-unreferenced objects. */ GDB_STATE(RT_DELETE,&root->linkmap); unload_object(root); GDB_STATE(RT_CONSISTENT,NULL); } wlock_release(); return 0; } const char * dlerror(void) { char *msg = error_message; error_message = NULL; return msg; } void * dlopen(const char *name, int mode) { Obj_Entry **old_obj_tail; Obj_Entry *obj; Objlist initlist; int result; ld_tracing = (mode & RTLD_TRACE) == 0 ? NULL : "1"; if (ld_tracing != NULL) environ = (char **)*get_program_var_addr("environ"); objlist_init(&initlist); wlock_acquire(); GDB_STATE(RT_ADD,NULL); old_obj_tail = obj_tail; obj = NULL; if (name == NULL) { obj = obj_main; obj->refcount++; } else { char *path = find_library(name, obj_main); if (path != NULL) obj = load_object(path); } if (obj) { obj->dl_refcount++; if ((mode & RTLD_GLOBAL) && objlist_find(&list_global, obj) == NULL) objlist_push_tail(&list_global, obj); mode &= RTLD_MODEMASK; if (*old_obj_tail != NULL) { /* We loaded something new. */ assert(*old_obj_tail == obj); result = load_needed_objects(obj); if (result != -1 && ld_tracing) goto trace; if (result == -1 || (init_dag(obj), relocate_objects(obj, mode == RTLD_NOW, &obj_rtld)) == -1) { obj->dl_refcount--; unref_dag(obj); if (obj->refcount == 0) unload_object(obj); obj = NULL; } else { /* Make list of init functions to call. */ initlist_add_objects(obj, &obj->next, &initlist); } } else if (ld_tracing) goto trace; } GDB_STATE(RT_CONSISTENT,obj ? &obj->linkmap : NULL); /* Call the init functions with no locks held. */ wlock_release(); objlist_call_init(&initlist); wlock_acquire(); objlist_clear(&initlist); wlock_release(); return obj; trace: trace_loaded_objects(obj); wlock_release(); exit(0); } void * dlsym(void *handle, const char *name) { const Obj_Entry *obj; unsigned long hash; const Elf_Sym *def; const Obj_Entry *defobj; hash = elf_hash(name); def = NULL; defobj = NULL; rlock_acquire(); if (handle == NULL || handle == RTLD_NEXT || handle == RTLD_DEFAULT || handle == RTLD_SELF) { void *retaddr; retaddr = __builtin_return_address(0); /* __GNUC__ only */ if ((obj = obj_from_addr(retaddr)) == NULL) { _rtld_error("Cannot determine caller's shared object"); rlock_release(); return NULL; } if (handle == NULL) { /* Just the caller's shared object. */ def = symlook_obj(name, hash, obj, true); defobj = obj; } else if (handle == RTLD_NEXT || /* Objects after caller's */ handle == RTLD_SELF) { /* ... caller included */ if (handle == RTLD_NEXT) obj = obj->next; for (; obj != NULL; obj = obj->next) { if ((def = symlook_obj(name, hash, obj, true)) != NULL) { defobj = obj; break; } } } else { assert(handle == RTLD_DEFAULT); def = symlook_default(name, hash, obj, &defobj, true); } } else { DoneList donelist; if ((obj = dlcheck(handle)) == NULL) { rlock_release(); return NULL; } donelist_init(&donelist); if (obj->mainprog) { /* Search main program and all libraries loaded by it. */ def = symlook_list(name, hash, &list_main, &defobj, true, &donelist); } else { Needed_Entry fake; /* Search the given object and its needed objects. */ fake.next = NULL; fake.obj = (Obj_Entry *)obj; fake.name = 0; def = symlook_needed(name, hash, &fake, &defobj, true, &donelist); } } if (def != NULL) { rlock_release(); return defobj->relocbase + def->st_value; } _rtld_error("Undefined symbol \"%s\"", name); rlock_release(); return NULL; } int dladdr(const void *addr, Dl_info *info) { const Obj_Entry *obj; const Elf_Sym *def; void *symbol_addr; unsigned long symoffset; rlock_acquire(); obj = obj_from_addr(addr); if (obj == NULL) { _rtld_error("No shared object contains address"); rlock_release(); return 0; } info->dli_fname = obj->path; info->dli_fbase = obj->mapbase; info->dli_saddr = (void *)0; info->dli_sname = NULL; /* * Walk the symbol list looking for the symbol whose address is * closest to the address sent in. */ for (symoffset = 0; symoffset < obj->nchains; symoffset++) { def = obj->symtab + symoffset; /* * For skip the symbol if st_shndx is either SHN_UNDEF or * SHN_COMMON. */ if (def->st_shndx == SHN_UNDEF || def->st_shndx == SHN_COMMON) continue; /* * If the symbol is greater than the specified address, or if it * is further away from addr than the current nearest symbol, * then reject it. */ symbol_addr = obj->relocbase + def->st_value; if (symbol_addr > addr || symbol_addr < info->dli_saddr) continue; /* Update our idea of the nearest symbol. */ info->dli_sname = obj->strtab + def->st_name; info->dli_saddr = symbol_addr; /* Exact match? */ if (info->dli_saddr == addr) break; } rlock_release(); return 1; } int dlinfo(void *handle, int request, void *p) { const Obj_Entry *obj; int error; rlock_acquire(); if (handle == NULL || handle == RTLD_SELF) { void *retaddr; retaddr = __builtin_return_address(0); /* __GNUC__ only */ if ((obj = obj_from_addr(retaddr)) == NULL) _rtld_error("Cannot determine caller's shared object"); } else obj = dlcheck(handle); if (obj == NULL) { rlock_release(); return (-1); } error = 0; switch (request) { case RTLD_DI_LINKMAP: *((struct link_map const **)p) = &obj->linkmap; break; case RTLD_DI_ORIGIN: error = rtld_dirname(obj->path, p); break; case RTLD_DI_SERINFOSIZE: case RTLD_DI_SERINFO: error = do_search_info(obj, request, (struct dl_serinfo *)p); break; default: _rtld_error("Invalid request %d passed to dlinfo()", request); error = -1; } rlock_release(); return (error); } struct fill_search_info_args { int request; unsigned int flags; Dl_serinfo *serinfo; Dl_serpath *serpath; char *strspace; }; static void * fill_search_info(const char *dir, size_t dirlen, void *param) { struct fill_search_info_args *arg; arg = param; if (arg->request == RTLD_DI_SERINFOSIZE) { arg->serinfo->dls_cnt ++; arg->serinfo->dls_size += dirlen + 1; } else { struct dl_serpath *s_entry; s_entry = arg->serpath; s_entry->dls_name = arg->strspace; s_entry->dls_flags = arg->flags; strncpy(arg->strspace, dir, dirlen); arg->strspace[dirlen] = '\0'; arg->strspace += dirlen + 1; arg->serpath++; } return (NULL); } static int do_search_info(const Obj_Entry *obj, int request, struct dl_serinfo *info) { struct dl_serinfo _info; struct fill_search_info_args args; args.request = RTLD_DI_SERINFOSIZE; args.serinfo = &_info; _info.dls_size = __offsetof(struct dl_serinfo, dls_serpath); _info.dls_cnt = 0; path_enumerate(ld_library_path, fill_search_info, &args); path_enumerate(obj->rpath, fill_search_info, &args); path_enumerate(gethints(), fill_search_info, &args); path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args); if (request == RTLD_DI_SERINFOSIZE) { info->dls_size = _info.dls_size; info->dls_cnt = _info.dls_cnt; return (0); } if (info->dls_cnt != _info.dls_cnt || info->dls_size != _info.dls_size) { _rtld_error("Uninitialized Dl_serinfo struct passed to dlinfo()"); return (-1); } args.request = RTLD_DI_SERINFO; args.serinfo = info; args.serpath = &info->dls_serpath[0]; args.strspace = (char *)&info->dls_serpath[_info.dls_cnt]; args.flags = LA_SER_LIBPATH; if (path_enumerate(ld_library_path, fill_search_info, &args) != NULL) return (-1); args.flags = LA_SER_RUNPATH; if (path_enumerate(obj->rpath, fill_search_info, &args) != NULL) return (-1); args.flags = LA_SER_CONFIG; if (path_enumerate(gethints(), fill_search_info, &args) != NULL) return (-1); args.flags = LA_SER_DEFAULT; if (path_enumerate(STANDARD_LIBRARY_PATH, fill_search_info, &args) != NULL) return (-1); return (0); } static int rtld_dirname(const char *path, char *bname) { const char *endp; /* Empty or NULL string gets treated as "." */ if (path == NULL || *path == '\0') { bname[0] = '.'; bname[1] = '\0'; return (0); } /* Strip trailing slashes */ endp = path + strlen(path) - 1; while (endp > path && *endp == '/') endp--; /* Find the start of the dir */ while (endp > path && *endp != '/') endp--; /* Either the dir is "/" or there are no slashes */ if (endp == path) { bname[0] = *endp == '/' ? '/' : '.'; bname[1] = '\0'; return (0); } else { do { endp--; } while (endp > path && *endp == '/'); } if (endp - path + 2 > PATH_MAX) { _rtld_error("Filename is too long: %s", path); return(-1); } strncpy(bname, path, endp - path + 1); bname[endp - path + 1] = '\0'; return (0); } static void linkmap_add(Obj_Entry *obj) { struct link_map *l = &obj->linkmap; struct link_map *prev; obj->linkmap.l_name = obj->path; obj->linkmap.l_addr = obj->mapbase; obj->linkmap.l_ld = obj->dynamic; #ifdef __mips__ /* GDB needs load offset on MIPS to use the symbols */ obj->linkmap.l_offs = obj->relocbase; #endif if (r_debug.r_map == NULL) { r_debug.r_map = l; return; } /* * Scan to the end of the list, but not past the entry for the * dynamic linker, which we want to keep at the very end. */ for (prev = r_debug.r_map; prev->l_next != NULL && prev->l_next != &obj_rtld.linkmap; prev = prev->l_next) ; /* Link in the new entry. */ l->l_prev = prev; l->l_next = prev->l_next; if (l->l_next != NULL) l->l_next->l_prev = l; prev->l_next = l; } static void linkmap_delete(Obj_Entry *obj) { struct link_map *l = &obj->linkmap; if (l->l_prev == NULL) { if ((r_debug.r_map = l->l_next) != NULL) l->l_next->l_prev = NULL; return; } if ((l->l_prev->l_next = l->l_next) != NULL) l->l_next->l_prev = l->l_prev; } /* * Function for the debugger to set a breakpoint on to gain control. * * The two parameters allow the debugger to easily find and determine * what the runtime loader is doing and to whom it is doing it. * * When the loadhook trap is hit (r_debug_state, set at program * initialization), the arguments can be found on the stack: * * +8 struct link_map *m * +4 struct r_debug *rd * +0 RetAddr */ void r_debug_state(struct r_debug* rd, struct link_map *m) { } /* * Get address of the pointer variable in the main program. */ static const void ** get_program_var_addr(const char *name) { const Obj_Entry *obj; unsigned long hash; hash = elf_hash(name); for (obj = obj_main; obj != NULL; obj = obj->next) { const Elf_Sym *def; if ((def = symlook_obj(name, hash, obj, false)) != NULL) { const void **addr; addr = (const void **)(obj->relocbase + def->st_value); return addr; } } return NULL; } /* * Set a pointer variable in the main program to the given value. This * is used to set key variables such as "environ" before any of the * init functions are called. */ static void set_program_var(const char *name, const void *value) { const void **addr; if ((addr = get_program_var_addr(name)) != NULL) { dbg("\"%s\": *%p <-- %p", name, addr, value); *addr = value; } } /* * This is a special version of getenv which is far more efficient * at finding LD_ environment vars. */ static const char * _getenv_ld(const char *id) { const char *envp; int i, j; int idlen = strlen(id); if (ld_index == LD_ARY_CACHE) return(getenv(id)); if (ld_index == 0) { for (i = j = 0; (envp = environ[i]) != NULL && j < LD_ARY_CACHE; ++i) { if (envp[0] == 'L' && envp[1] == 'D' && envp[2] == '_') ld_ary[j++] = envp; } if (j == 0) ld_ary[j++] = ""; ld_index = j; } for (i = ld_index - 1; i >= 0; --i) { if (strncmp(ld_ary[i], id, idlen) == 0 && ld_ary[i][idlen] == '=') return(ld_ary[i] + idlen + 1); } return(NULL); } /* * Given a symbol name in a referencing object, find the corresponding * definition of the symbol. Returns a pointer to the symbol, or NULL if * no definition was found. Returns a pointer to the Obj_Entry of the * defining object via the reference parameter DEFOBJ_OUT. */ static const Elf_Sym * symlook_default(const char *name, unsigned long hash, const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt) { DoneList donelist; const Elf_Sym *def; const Elf_Sym *symp; const Obj_Entry *obj; const Obj_Entry *defobj; const Objlist_Entry *elm; def = NULL; defobj = NULL; donelist_init(&donelist); /* Look first in the referencing object if linked symbolically. */ if (refobj->symbolic && !donelist_check(&donelist, refobj)) { symp = symlook_obj(name, hash, refobj, in_plt); if (symp != NULL) { def = symp; defobj = refobj; } } /* Search all objects loaded at program start up. */ if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist); if (symp != NULL && (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { def = symp; defobj = obj; } } /* Search all DAGs whose roots are RTLD_GLOBAL objects. */ STAILQ_FOREACH(elm, &list_global, link) { if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) break; symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, &donelist); if (symp != NULL && (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { def = symp; defobj = obj; } } /* Search all dlopened DAGs containing the referencing object. */ STAILQ_FOREACH(elm, &refobj->dldags, link) { if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK) break; symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt, &donelist); if (symp != NULL && (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) { def = symp; defobj = obj; } } /* * Search the dynamic linker itself, and possibly resolve the * symbol from there. This is how the application links to * dynamic linker services such as dlopen. Only the values listed * in the "exports" array can be resolved from the dynamic linker. */ if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) { symp = symlook_obj(name, hash, &obj_rtld, in_plt); if (symp != NULL && is_exported(symp)) { def = symp; defobj = &obj_rtld; } } if (def != NULL) *defobj_out = defobj; return def; } static const Elf_Sym * symlook_list(const char *name, unsigned long hash, const Objlist *objlist, const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) { const Elf_Sym *symp; const Elf_Sym *def; const Obj_Entry *defobj; const Objlist_Entry *elm; def = NULL; defobj = NULL; STAILQ_FOREACH(elm, objlist, link) { if (donelist_check(dlp, elm->obj)) continue; if ((symp = symlook_obj(name, hash, elm->obj, in_plt)) != NULL) { if (def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK) { def = symp; defobj = elm->obj; if (ELF_ST_BIND(def->st_info) != STB_WEAK) break; } } } if (def != NULL) *defobj_out = defobj; return def; } /* * Search the symbol table of a shared object and all objects needed * by it for a symbol of the given name. Search order is * breadth-first. Returns a pointer to the symbol, or NULL if no * definition was found. */ static const Elf_Sym * symlook_needed(const char *name, unsigned long hash, const Needed_Entry *needed, const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp) { const Elf_Sym *def, *def_w; const Needed_Entry *n; const Obj_Entry *obj, *defobj, *defobj1; def = def_w = NULL; defobj = NULL; for (n = needed; n != NULL; n = n->next) { if ((obj = n->obj) == NULL || donelist_check(dlp, obj) || (def = symlook_obj(name, hash, obj, in_plt)) == NULL) continue; defobj = obj; if (ELF_ST_BIND(def->st_info) != STB_WEAK) { *defobj_out = defobj; return (def); } } /* * There we come when either symbol definition is not found in * directly needed objects, or found symbol is weak. */ for (n = needed; n != NULL; n = n->next) { if ((obj = n->obj) == NULL) continue; def_w = symlook_needed(name, hash, obj->needed, &defobj1, in_plt, dlp); if (def_w == NULL) continue; if (def == NULL || ELF_ST_BIND(def_w->st_info) != STB_WEAK) { def = def_w; defobj = defobj1; } if (ELF_ST_BIND(def_w->st_info) != STB_WEAK) break; } if (def != NULL) *defobj_out = defobj; return def; } /* * Search the symbol table of a single shared object for a symbol of * the given name. Returns a pointer to the symbol, or NULL if no * definition was found. * * The symbol's hash value is passed in for efficiency reasons; that * eliminates many recomputations of the hash value. */ const Elf_Sym * symlook_obj(const char *name, unsigned long hash, const Obj_Entry *obj, bool in_plt) { if (obj->buckets != NULL) { unsigned long symnum = obj->buckets[hash % obj->nbuckets]; while (symnum != STN_UNDEF) { const Elf_Sym *symp; const char *strp; if (symnum >= obj->nchains) return NULL; /* Bad object */ symp = obj->symtab + symnum; strp = obj->strtab + symp->st_name; if (name[0] == strp[0] && strcmp(name, strp) == 0) return symp->st_shndx != SHN_UNDEF || (!in_plt && symp->st_value != 0 && ELF_ST_TYPE(symp->st_info) == STT_FUNC) ? symp : NULL; symnum = obj->chains[symnum]; } } return NULL; } static void trace_loaded_objects(Obj_Entry *obj) { const char *fmt1, *fmt2, *fmt, *main_local; int c; if ((main_local = _getenv_ld("LD_TRACE_LOADED_OBJECTS_PROGNAME")) == NULL) main_local = ""; if ((fmt1 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT1")) == NULL) fmt1 = "\t%o => %p (%x)\n"; if ((fmt2 = _getenv_ld("LD_TRACE_LOADED_OBJECTS_FMT2")) == NULL) fmt2 = "\t%o (%x)\n"; for (; obj; obj = obj->next) { Needed_Entry *needed; char *name, *path; bool is_lib; for (needed = obj->needed; needed; needed = needed->next) { if (needed->obj != NULL) { if (needed->obj->traced) continue; needed->obj->traced = true; path = needed->obj->path; } else path = "not found"; name = (char *)obj->strtab + needed->name; is_lib = strncmp(name, "lib", 3) == 0; /* XXX - bogus */ fmt = is_lib ? fmt1 : fmt2; while ((c = *fmt++) != '\0') { switch (c) { default: putchar(c); continue; case '\\': switch (c = *fmt) { case '\0': continue; case 'n': putchar('\n'); break; case 't': putchar('\t'); break; } break; case '%': switch (c = *fmt) { case '\0': continue; case '%': default: putchar(c); break; case 'A': printf("%s", main_local); break; case 'a': printf("%s", obj_main->path); break; case 'o': printf("%s", name); break; #if 0 case 'm': printf("%d", sodp->sod_major); break; case 'n': printf("%d", sodp->sod_minor); break; #endif case 'p': printf("%s", path); break; case 'x': printf("%p", needed->obj ? needed->obj->mapbase : 0); break; } break; } ++fmt; } } } } /* * Unload a dlopened object and its dependencies from memory and from * our data structures. It is assumed that the DAG rooted in the * object has already been unreferenced, and that the object has a * reference count of 0. */ static void unload_object(Obj_Entry *root) { Obj_Entry *obj; Obj_Entry **linkp; assert(root->refcount == 0); /* * Pass over the DAG removing unreferenced objects from * appropriate lists. */ unlink_object(root); /* Unmap all objects that are no longer referenced. */ linkp = &obj_list->next; while ((obj = *linkp) != NULL) { if (obj->refcount == 0) { dbg("unloading \"%s\"", obj->path); munmap(obj->mapbase, obj->mapsize); linkmap_delete(obj); *linkp = obj->next; obj_count--; obj_free(obj); } else linkp = &obj->next; } obj_tail = linkp; } static void unlink_object(Obj_Entry *root) { const Needed_Entry *needed; Objlist_Entry *elm; if (root->refcount == 0) { /* Remove the object from the RTLD_GLOBAL list. */ objlist_remove(&list_global, root); /* Remove the object from all objects' DAG lists. */ STAILQ_FOREACH(elm, &root->dagmembers , link) objlist_remove(&elm->obj->dldags, root); } for (needed = root->needed; needed != NULL; needed = needed->next) if (needed->obj != NULL) unlink_object(needed->obj); } static void unref_dag(Obj_Entry *root) { const Needed_Entry *needed; if (root->refcount == 0) return; root->refcount--; if (root->refcount == 0) for (needed = root->needed; needed != NULL; needed = needed->next) if (needed->obj != NULL) unref_dag(needed->obj); } /* * Common code for MD __tls_get_addr(). */ void * tls_get_addr_common(void **dtvp, int index, size_t offset) { Elf_Addr* dtv = *dtvp; /* Check dtv generation in case new modules have arrived */ if (dtv[0] != tls_dtv_generation) { Elf_Addr* newdtv; int to_copy; wlock_acquire(); newdtv = calloc(1, (tls_max_index + 2) * sizeof(Elf_Addr)); to_copy = dtv[1]; if (to_copy > tls_max_index) to_copy = tls_max_index; memcpy(&newdtv[2], &dtv[2], to_copy * sizeof(Elf_Addr)); newdtv[0] = tls_dtv_generation; newdtv[1] = tls_max_index; free(dtv); *dtvp = newdtv; wlock_release(); } /* Dynamically allocate module TLS if necessary */ if (!dtv[index + 1]) { /* XXX * here we should avoid to be re-entered by signal handler * code, I assume wlock_acquire will masked all signals, * otherwise there is race and dead lock thread itself. */ wlock_acquire(); if (!dtv[index + 1]) dtv[index + 1] = (Elf_Addr)allocate_module_tls(index); wlock_release(); } return (void*) (dtv[index + 1] + offset); } #if defined(RTLD_STATIC_TLS_VARIANT_II) /* * Allocate the static TLS area. Return a pointer to the TCB. The * static area is based on negative offsets relative to the tcb. * * The TCB contains an errno pointer for the system call layer, but because * we are the RTLD we really have no idea how the caller was compiled so * the information has to be passed in. errno can either be: * * type 0 errno is a simple non-TLS global pointer. * (special case for e.g. libc_rtld) * type 1 errno accessed by GOT entry (dynamically linked programs) * type 2 errno accessed by %gs:OFFSET (statically linked programs) */ struct tls_tcb * allocate_tls(Obj_Entry *objs) { Obj_Entry *obj; size_t data_size; size_t dtv_size; struct tls_tcb *tcb; Elf_Addr *dtv; Elf_Addr addr; /* * Allocate the new TCB. static TLS storage is placed just before the * TCB to support the %gs:OFFSET (negative offset) model. */ data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) & ~RTLD_STATIC_TLS_ALIGN_MASK; tcb = malloc(data_size + sizeof(*tcb)); tcb = (void *)((char *)tcb + data_size); /* actual tcb location */ dtv_size = (tls_max_index + 2) * sizeof(Elf_Addr); dtv = malloc(dtv_size); bzero(dtv, dtv_size); #ifdef RTLD_TCB_HAS_SELF_POINTER tcb->tcb_self = tcb; #endif tcb->tcb_dtv = dtv; tcb->tcb_pthread = NULL; dtv[0] = tls_dtv_generation; dtv[1] = tls_max_index; for (obj = objs; obj; obj = obj->next) { if (obj->tlsoffset) { addr = (Elf_Addr)tcb - obj->tlsoffset; memset((void *)(addr + obj->tlsinitsize), 0, obj->tlssize - obj->tlsinitsize); if (obj->tlsinit) memcpy((void*) addr, obj->tlsinit, obj->tlsinitsize); dtv[obj->tlsindex + 1] = addr; } } return(tcb); } void free_tls(struct tls_tcb *tcb) { Elf_Addr *dtv; int dtv_size, i; Elf_Addr tls_start, tls_end; size_t data_size; data_size = (tls_static_space + RTLD_STATIC_TLS_ALIGN_MASK) & ~RTLD_STATIC_TLS_ALIGN_MASK; dtv = tcb->tcb_dtv; dtv_size = dtv[1]; tls_end = (Elf_Addr)tcb; tls_start = (Elf_Addr)tcb - data_size; for (i = 0; i < dtv_size; i++) { if (dtv[i+2] != NULL && (dtv[i+2] < tls_start || dtv[i+2] > tls_end)) { free((void *)dtv[i+2]); } } free((void *)tls_start); } #else #error "Unsupported TLS layout" #endif /* * Allocate TLS block for module with given index. */ void * allocate_module_tls(int index) { Obj_Entry* obj; char* p; for (obj = obj_list; obj; obj = obj->next) { if (obj->tlsindex == index) break; } if (!obj) { _rtld_error("Can't find module with TLS index %d", index); die(); } p = malloc(obj->tlssize); memcpy(p, obj->tlsinit, obj->tlsinitsize); memset(p + obj->tlsinitsize, 0, obj->tlssize - obj->tlsinitsize); return p; } bool allocate_tls_offset(Obj_Entry *obj) { size_t off; if (obj->tls_done) return true; if (obj->tlssize == 0) { obj->tls_done = true; return true; } if (obj->tlsindex == 1) off = calculate_first_tls_offset(obj->tlssize, obj->tlsalign); else off = calculate_tls_offset(tls_last_offset, tls_last_size, obj->tlssize, obj->tlsalign); /* * If we have already fixed the size of the static TLS block, we * must stay within that size. When allocating the static TLS, we * leave a small amount of space spare to be used for dynamically * loading modules which use static TLS. */ if (tls_static_space) { if (calculate_tls_end(off, obj->tlssize) > tls_static_space) return false; } tls_last_offset = obj->tlsoffset = off; tls_last_size = obj->tlssize; obj->tls_done = true; return true; } void free_tls_offset(Obj_Entry *obj) { #ifdef RTLD_STATIC_TLS_VARIANT_II /* * If we were the last thing to allocate out of the static TLS * block, we give our space back to the 'allocator'. This is a * simplistic workaround to allow libGL.so.1 to be loaded and * unloaded multiple times. We only handle the Variant II * mechanism for now - this really needs a proper allocator. */ if (calculate_tls_end(obj->tlsoffset, obj->tlssize) == calculate_tls_end(tls_last_offset, tls_last_size)) { tls_last_offset -= obj->tlssize; tls_last_size = 0; } #endif } struct tls_tcb * _rtld_allocate_tls(void) { struct tls_tcb *new_tcb; wlock_acquire(); new_tcb = allocate_tls(obj_list); wlock_release(); return (new_tcb); } void _rtld_free_tls(struct tls_tcb *tcb) { wlock_acquire(); free_tls(tcb); wlock_release(); }