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Add support for dlsym(RTLD_DEFAULT, ...).

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This commit is contained in:
John Polstra 2000-09-19 04:27:16 +00:00
parent 362a3eadeb
commit 185db83c04
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=66056
2 changed files with 97 additions and 69 deletions
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162
libexec/rtld-elf/rtld.c
View File

@ -63,7 +63,7 @@ typedef void (*func_ptr_type)();
* check which ones have already been processed in some way.
*/
typedef struct Struct_DoneList {
Obj_Entry **objs; /* Array of object pointers */
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;
@ -76,7 +76,7 @@ static void die(void);
static void digest_dynamic(Obj_Entry *);
static Obj_Entry *digest_phdr(const Elf_Phdr *, int, caddr_t, const char *);
static Obj_Entry *dlcheck(void *);
static bool donelist_check(DoneList *, Obj_Entry *);
static bool donelist_check(DoneList *, const Obj_Entry *);
static char *find_library(const char *, const Obj_Entry *);
static const char *gethints(void);
static void init_dag(Obj_Entry *);
@ -106,6 +106,8 @@ static int relocate_objects(Obj_Entry *, bool);
static void rtld_exit(void);
static char *search_library_path(const char *, const char *);
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,
Objlist *, const Obj_Entry **, bool in_plt, DoneList *);
static void trace_loaded_objects(Obj_Entry *obj);
@ -706,7 +708,7 @@ dlcheck(void *handle)
* add the object to the list and return false.
*/
static bool
donelist_check(DoneList *dlp, Obj_Entry *obj)
donelist_check(DoneList *dlp, const Obj_Entry *obj)
{
unsigned int i;
@ -792,81 +794,21 @@ find_library(const char *name, const Obj_Entry *refobj)
* defining object via the reference parameter DEFOBJ_OUT.
*/
const Elf_Sym *
find_symdef(unsigned long symnum, Obj_Entry *refobj,
find_symdef(unsigned long symnum, const Obj_Entry *refobj,
const Obj_Entry **defobj_out, bool in_plt)
{
DoneList donelist;
const Elf_Sym *ref;
const Elf_Sym *def;
const Elf_Sym *symp;
const Obj_Entry *obj;
const Obj_Entry *defobj;
const Objlist_Entry *elm;
const char *name;
unsigned long hash;
ref = refobj->symtab + symnum;
name = refobj->strtab + ref->st_name;
hash = elf_hash(name);
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 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 all RTLD_GLOBAL objects. */
if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
symp = symlook_list(name, hash, &list_global, &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;
}
}
def = symlook_default(name, hash, refobj, &defobj, in_plt);
/*
* If we found no definition and the reference is weak, treat the
@ -1605,7 +1547,7 @@ dlsym(void *handle, const char *name)
defobj = NULL;
rlock_acquire();
if (handle == NULL || handle == RTLD_NEXT) {
if (handle == NULL || handle == RTLD_NEXT || handle == RTLD_DEFAULT) {
void *retaddr;
retaddr = __builtin_return_address(0); /* __GNUC__ only */
@ -1617,13 +1559,16 @@ dlsym(void *handle, const char *name)
if (handle == NULL) { /* Just the caller's shared object. */
def = symlook_obj(name, hash, obj, true);
defobj = obj;
} else { /* All the shared objects after the caller's */
} else if (handle == RTLD_NEXT) { /* Objects after caller's */
while ((obj = obj->next) != NULL) {
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 {
if ((obj = dlcheck(handle)) == NULL) {
@ -1808,6 +1753,89 @@ set_program_var(const char *name, const void *value)
}
}
/*
* 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 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 all RTLD_GLOBAL objects. */
if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
symp = symlook_list(name, hash, &list_global, &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;
else
_rtld_error("%s: Undefined symbol \"%s\"", refobj->path, name);
return def;
}
static const Elf_Sym *
symlook_list(const char *name, unsigned long hash, Objlist *objlist,
const Obj_Entry **defobj_out, bool in_plt, DoneList *dlp)

4
libexec/rtld-elf/rtld.h
View File

@ -177,8 +177,8 @@ extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
*/
int do_copy_relocations(Obj_Entry *);
unsigned long elf_hash(const char *);
const Elf_Sym *find_symdef(unsigned long, Obj_Entry *, const Obj_Entry **,
bool);
const Elf_Sym *find_symdef(unsigned long, const Obj_Entry *,
const Obj_Entry **, bool);
void init_pltgot(Obj_Entry *);
void lockdflt_init(LockInfo *);
void obj_free(Obj_Entry *);