Add support for dlsym(RTLD_DEFAULT, ...).
This commit is contained in:
John Polstra
parent
362a3eadeb
commit
185db83c04
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@ -63,7 +63,7 @@ typedef void (*func_ptr_type)();
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* check which ones have already been processed in some way.
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*/
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typedef struct Struct_DoneList {
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Obj_Entry **objs; /* Array of object pointers */
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const Obj_Entry **objs; /* Array of object pointers */
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unsigned int num_alloc; /* Allocated size of the array */
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unsigned int num_used; /* Number of array slots used */
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} DoneList;
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@ -76,7 +76,7 @@ static void die(void);
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static void digest_dynamic(Obj_Entry *);
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static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
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static Obj_Entry *dlcheck(void *);
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static bool donelist_check(DoneList *, Obj_Entry *);
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static bool donelist_check(DoneList *, const Obj_Entry *);
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static char *find_library(const char *, const Obj_Entry *);
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static const char *gethints(void);
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static void init_dag(Obj_Entry *);
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@ -106,6 +106,8 @@ static int relocate_objects(Obj_Entry *, bool);
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static void rtld_exit(void);
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static char *search_library_path(const char *, const char *);
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static void set_program_var(const char *, const void *);
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static const Elf_Sym *symlook_default(const char *, unsigned long hash,
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const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt);
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static const Elf_Sym *symlook_list(const char *, unsigned long,
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Objlist *, const Obj_Entry **, bool in_plt, DoneList *);
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static void trace_loaded_objects(Obj_Entry *obj);
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@ -706,7 +708,7 @@ dlcheck(void *handle)
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* add the object to the list and return false.
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*/
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static bool
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donelist_check(DoneList *dlp, Obj_Entry *obj)
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donelist_check(DoneList *dlp, const Obj_Entry *obj)
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{
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unsigned int i;
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@ -792,81 +794,21 @@ find_library(const char *name, const Obj_Entry *refobj)
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* defining object via the reference parameter DEFOBJ_OUT.
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*/
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const Elf_Sym *
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find_symdef(unsigned long symnum, Obj_Entry *refobj,
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find_symdef(unsigned long symnum, const Obj_Entry *refobj,
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const Obj_Entry **defobj_out, bool in_plt)
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{
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DoneList donelist;
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const Elf_Sym *ref;
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const Elf_Sym *def;
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const Elf_Sym *symp;
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const Obj_Entry *obj;
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const Obj_Entry *defobj;
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const Objlist_Entry *elm;
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const char *name;
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unsigned long hash;
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ref = refobj->symtab + symnum;
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name = refobj->strtab + ref->st_name;
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hash = elf_hash(name);
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def = NULL;
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defobj = NULL;
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donelist_init(&donelist);
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/* Look first in the referencing object if linked symbolically. */
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if (refobj->symbolic && !donelist_check(&donelist, refobj)) {
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symp = symlook_obj(name, hash, refobj, in_plt);
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if (symp != NULL) {
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def = symp;
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defobj = refobj;
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}
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}
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/* Search all objects loaded at program start up. */
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if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
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symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist);
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if (symp != NULL &&
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(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
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def = symp;
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defobj = obj;
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}
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}
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/* Search all dlopened DAGs containing the referencing object. */
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STAILQ_FOREACH(elm, &refobj->dldags, link) {
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if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
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break;
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symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
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&donelist);
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if (symp != NULL &&
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(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
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def = symp;
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defobj = obj;
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}
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}
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/* Search all RTLD_GLOBAL objects. */
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if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
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symp = symlook_list(name, hash, &list_global, &obj, in_plt, &donelist);
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if (symp != NULL &&
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(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
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def = symp;
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defobj = obj;
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}
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}
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/*
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* Search the dynamic linker itself, and possibly resolve the
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* symbol from there. This is how the application links to
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* dynamic linker services such as dlopen. Only the values listed
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* in the "exports" array can be resolved from the dynamic linker.
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*/
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if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
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symp = symlook_obj(name, hash, &obj_rtld, in_plt);
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if (symp != NULL && is_exported(symp)) {
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def = symp;
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defobj = &obj_rtld;
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}
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}
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def = symlook_default(name, hash, refobj, &defobj, in_plt);
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/*
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* If we found no definition and the reference is weak, treat the
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@ -1605,7 +1547,7 @@ dlsym(void *handle, const char *name)
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defobj = NULL;
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rlock_acquire();
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if (handle == NULL || handle == RTLD_NEXT) {
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if (handle == NULL || handle == RTLD_NEXT || handle == RTLD_DEFAULT) {
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void *retaddr;
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retaddr = __builtin_return_address(0); /* __GNUC__ only */
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@ -1617,13 +1559,16 @@ dlsym(void *handle, const char *name)
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if (handle == NULL) { /* Just the caller's shared object. */
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def = symlook_obj(name, hash, obj, true);
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defobj = obj;
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} else { /* All the shared objects after the caller's */
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} else if (handle == RTLD_NEXT) { /* Objects after caller's */
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while ((obj = obj->next) != NULL) {
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if ((def = symlook_obj(name, hash, obj, true)) != NULL) {
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defobj = obj;
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break;
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}
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}
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} else {
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assert(handle == RTLD_DEFAULT);
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def = symlook_default(name, hash, obj, &defobj, true);
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}
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} else {
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if ((obj = dlcheck(handle)) == NULL) {
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@ -1808,6 +1753,89 @@ set_program_var(const char *name, const void *value)
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}
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}
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/*
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* Given a symbol name in a referencing object, find the corresponding
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* definition of the symbol. Returns a pointer to the symbol, or NULL if
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* no definition was found. Returns a pointer to the Obj_Entry of the
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* defining object via the reference parameter DEFOBJ_OUT.
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*/
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static const Elf_Sym *
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symlook_default(const char *name, unsigned long hash,
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const Obj_Entry *refobj, const Obj_Entry **defobj_out, bool in_plt)
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{
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DoneList donelist;
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const Elf_Sym *def;
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const Elf_Sym *symp;
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const Obj_Entry *obj;
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const Obj_Entry *defobj;
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const Objlist_Entry *elm;
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def = NULL;
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defobj = NULL;
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donelist_init(&donelist);
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/* Look first in the referencing object if linked symbolically. */
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if (refobj->symbolic && !donelist_check(&donelist, refobj)) {
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symp = symlook_obj(name, hash, refobj, in_plt);
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if (symp != NULL) {
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def = symp;
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defobj = refobj;
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}
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}
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/* Search all objects loaded at program start up. */
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if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
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symp = symlook_list(name, hash, &list_main, &obj, in_plt, &donelist);
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if (symp != NULL &&
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(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
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def = symp;
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defobj = obj;
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}
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}
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/* Search all dlopened DAGs containing the referencing object. */
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STAILQ_FOREACH(elm, &refobj->dldags, link) {
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if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
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break;
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symp = symlook_list(name, hash, &elm->obj->dagmembers, &obj, in_plt,
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&donelist);
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if (symp != NULL &&
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(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
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def = symp;
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defobj = obj;
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}
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}
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/* Search all RTLD_GLOBAL objects. */
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if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
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symp = symlook_list(name, hash, &list_global, &obj, in_plt, &donelist);
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if (symp != NULL &&
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(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
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def = symp;
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defobj = obj;
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}
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}
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/*
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* Search the dynamic linker itself, and possibly resolve the
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* symbol from there. This is how the application links to
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* dynamic linker services such as dlopen. Only the values listed
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* in the "exports" array can be resolved from the dynamic linker.
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*/
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if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
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symp = symlook_obj(name, hash, &obj_rtld, in_plt);
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if (symp != NULL && is_exported(symp)) {
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def = symp;
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defobj = &obj_rtld;
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}
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}
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if (def != NULL)
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*defobj_out = defobj;
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else
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_rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
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return def;
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}
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static const Elf_Sym *
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symlook_list(const char *name, unsigned long hash, Objlist *objlist,
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const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)
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@ -177,8 +177,8 @@ extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
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*/
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int do_copy_relocations(Obj_Entry *);
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unsigned long elf_hash(const char *);
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const Elf_Sym *find_symdef(unsigned long, Obj_Entry *, const Obj_Entry **,
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bool);
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const Elf_Sym *find_symdef(unsigned long, const Obj_Entry *,
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const Obj_Entry **, bool);
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void init_pltgot(Obj_Entry *);
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void lockdflt_init(LockInfo *);
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void obj_free(Obj_Entry *);
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