NetBSD/libexec/ld.elf_so/rtld.c

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/* $NetBSD: rtld.c,v 1.5 1997/10/08 08:55:37 mrg Exp $ */
/*
* Copyright 1996 John D. Polstra.
* Copyright 1996 Matt Thomas <matt@3am-software.com>
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Polstra.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* 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.
*/
/*
* Dynamic linker for ELF.
*
* John Polstra <jdp@polstra.com>.
*/
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/mman.h>
#include <dirent.h>
#include <ctype.h>
#include <dlfcn.h>
#include "debug.h"
#include "rtld.h"
#include "sysident.h"
#ifndef RTLD_NOW
#define RTLD_NOW (RTLD_LAZY + 1)
#endif
/*
* Debugging support.
*/
typedef void (*funcptr)(void);
/*
* Function declarations.
*/
static void _rtld_init(caddr_t);
static void _rtld_exit(void);
/*
* Data declarations.
*/
static char *error_message; /* Message for dlopen(), or NULL */
struct r_debug _rtld_debug; /* for GDB; */
bool _rtld_trust; /* False for setuid and setgid programs */
Obj_Entry *_rtld_objlist; /* Head of linked list of shared objects */
Obj_Entry **_rtld_objtail; /* Link field of last object in list */
Obj_Entry *_rtld_objmain; /* The main program shared object */
Obj_Entry _rtld_objself; /* The dynamic linker shared object */
char _rtld_path[] = _PATH_RTLD;
Search_Path *_rtld_paths;
/*
* Global declarations normally provided by crt0.
*/
char *__progname;
char **environ;
#ifdef OLD_GOT
extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
#else
extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
extern Elf_Dyn _DYNAMIC;
#endif
static void
_rtld_call_fini_functions(
Obj_Entry *first)
{
Obj_Entry *obj;
for (obj = first; obj != NULL; obj = obj->next)
if (obj->fini != NULL)
(*obj->fini)();
}
static void
_rtld_call_init_functions(
Obj_Entry *first)
{
if (first != NULL) {
_rtld_call_init_functions(first->next);
if (first->init != NULL)
(*first->init)();
}
}
/*
* 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
_rtld_init(
caddr_t mapbase)
{
_rtld_add_paths(&_rtld_paths, RTLD_DEFAULT_LIBRARY_PATH);
/* Conjure up an Obj_Entry structure for the dynamic linker. */
_rtld_objself.path = _rtld_path;
_rtld_objself.rtld = true;
_rtld_objself.mapbase = mapbase;
_rtld_objself.relocbase = mapbase;
_rtld_objself.pltgot = NULL;
#ifdef OLD_GOT
_rtld_objself.dynamic = (Elf_Dyn *) _GLOBAL_OFFSET_TABLE_[0];
#else
_rtld_objself.dynamic = &_DYNAMIC;
#endif
_rtld_digest_dynamic(&_rtld_objself);
#ifdef __alpha__
/* XXX XXX XXX */
_rtld_objself.pltgot = NULL;
#endif
assert(_rtld_objself.needed == NULL);
assert(!_rtld_objself.textrel);
/* Set up the _rtld_objlist pointer, so that rtld symbols can be found. */
_rtld_objlist = &_rtld_objself;
_rtld_relocate_objects(&_rtld_objself, true);
/* Make the object list empty again. */
_rtld_objlist = NULL;
_rtld_objtail = &_rtld_objlist;
_rtld_debug.r_brk = _rtld_debug_state;
_rtld_debug.r_state = RT_CONSISTENT;
}
/*
* Cleanup procedure. It will be called (by the atexit() mechanism) just
* before the process exits.
*/
static void
_rtld_exit(void)
{
dbg("rtld_exit()");
_rtld_call_fini_functions(_rtld_objlist->next);
}
/*
* Main entry point for dynamic linking. The 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.
*
* This function returns the entry point for the main program in %eax,
* and the dynamic linker's exit procedure in %edx. We accomplish this
* by declaring the return value to have the 64-bit type "long long".
* Such values are returned with their most-significant 32 bits in %edx,
* and their least-significant 32 bits in %eax.
*/
Elf_Addr _rtld(Elf_Word *);
Elf_Addr
_rtld(
Elf_Word *sp)
{
const AuxInfo *aux_info[AUX_count];
int i = 0;
char **env;
const AuxInfo *aux;
const AuxInfo *auxp;
Elf_Word * const osp = sp;
bool bind_now = 0;
const char *ld_bind_now;
const char **argv;
/*
* On entry, the dynamic linker itself has not been relocated yet.
* Be very careful not to reference any global data until after
* _rtld_init 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. */
/* first Elf_Word reserved to address of exit routine */
#ifdef RTLD_DEBUG
xprintf("sp = %p, argc = %d, argv = %p <%s>\n", sp, sp[2], &sp[3], sp[3]);
xprintf("got is at %p, dynamic is at %p\n", _GLOBAL_OFFSET_TABLE_, &_DYNAMIC);
debug = 1;
xprintf("_ctype_ is %p\n", _ctype_);
#endif
sp += 2; /* skip over return argument space */
argv = (const char **) &sp[1];
sp += sp[0] + 2; /* Skip over argc, arguments, and NULL terminator */
env = (char **) sp;
while (*sp++ != 0) { /* Skip over environment, and NULL terminator */
#ifdef RTLD_DEBUG
xprintf("env[%d] = %p\n", i++, sp[-1]);
#endif
}
aux = (const AuxInfo *) sp;
/* Digest the auxiliary vector. */
for (i = 0; i < AUX_count; ++i)
aux_info[i] = NULL;
for (auxp = aux; auxp->au_id != AUX_null; ++auxp) {
if (auxp->au_id < AUX_count)
aux_info[auxp->au_id] = auxp;
}
/* Initialize and relocate ourselves. */
assert(aux_info[AUX_base] != NULL);
_rtld_init((caddr_t) aux_info[AUX_base]->au_v);
#ifdef RTLD_DEBUG
xprintf("_ctype_ is %p\n", _ctype_);
#endif
if (aux_info[AUX_debug] != NULL) /* Set debugging level */
debug = aux_info[AUX_debug]->au_v;
__progname = _rtld_objself.path;
environ = env;
_rtld_trust = geteuid() == getuid() && getegid() == getgid();
ld_bind_now = getenv("LD_BIND_NOW");
if (ld_bind_now != NULL && *ld_bind_now != '\0')
bind_now = true;
if (_rtld_trust) {
const char *ld_debug = getenv("LD_DEBUG");
if (ld_debug != NULL && *ld_debug != '\0')
debug = 1;
_rtld_add_paths(&_rtld_paths, getenv("LD_LIBRARY_PATH"));
}
dbg("%s is initialized, base address = %p", __progname,
(caddr_t) aux_info[AUX_base]->au_v);
/*
* Load the main program, or process its program header if it is
* already loaded.
*/
if (aux_info[AUX_execfd] != NULL) { /* Load the main program. */
int fd = aux_info[AUX_execfd]->au_v;
dbg("loading main program");
_rtld_objmain = _rtld_map_object(argv[0], fd);
close(fd);
if (_rtld_objmain == NULL)
_rtld_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[AUX_phdr] != NULL);
phdr = (const Elf_Phdr *) aux_info[AUX_phdr]->au_v;
assert(aux_info[AUX_phnum] != NULL);
phnum = aux_info[AUX_phnum]->au_v;
assert(aux_info[AUX_phent] != NULL);
assert(aux_info[AUX_phent]->au_v == sizeof(Elf_Phdr));
assert(aux_info[AUX_entry] != NULL);
entry = (caddr_t) aux_info[AUX_entry]->au_v;
_rtld_objmain = _rtld_digest_phdr(phdr, phnum, entry);
}
_rtld_objmain->path = xstrdup("main program");
_rtld_objmain->mainprog = true;
_rtld_digest_dynamic(_rtld_objmain);
_rtld_linkmap_add(_rtld_objmain);
_rtld_linkmap_add(&_rtld_objself);
/* Link the main program into the list of objects. */
*_rtld_objtail = _rtld_objmain;
_rtld_objtail = &_rtld_objmain->next;
++_rtld_objmain->refcount;
dbg("loading needed objects");
if (_rtld_load_needed_objects(_rtld_objmain) == -1)
_rtld_die();
dbg("relocating objects");
if (_rtld_relocate_objects(_rtld_objmain, bind_now) == -1)
_rtld_die();
dbg("doing copy relocations");
if (_rtld_do_copy_relocations(_rtld_objmain) == -1)
_rtld_die();
dbg("calling _init functions");
_rtld_call_init_functions(_rtld_objmain->next);
dbg("transferring control to program entry point = %p",
_rtld_objmain->entry);
/* Return with the entry point and the exit procedure in at the top of
* stack.
*/
_rtld_debug_state(); /* say hello to gdb! */
((void **) osp)[0] = _rtld_exit;
((void **) osp)[1] = _rtld_objmain;
return (Elf_Addr) _rtld_objmain->entry;
}
void
_rtld_die(
void)
{
const char *msg = _rtld_dlerror();
if (msg == NULL)
msg = "Fatal error";
xerrx(1, "%s\n", msg);
}
static Obj_Entry *
_rtld_dlcheck(
void *handle)
{
Obj_Entry *obj;
for (obj = _rtld_objlist; obj != NULL; obj = obj->next)
if (obj == (Obj_Entry *) handle)
break;
if (obj == NULL || obj->dl_refcount == 0) {
xwarnx("Invalid shared object handle %p", handle);
return NULL;
}
return obj;
}
static void
_rtld_unref_object_dag(
Obj_Entry *root)
{
assert(root->refcount != 0);
--root->refcount;
if (root->refcount == 0) {
const Needed_Entry *needed;
for (needed = root->needed; needed != NULL; needed = needed->next)
_rtld_unref_object_dag(needed->obj);
}
}
int
_rtld_dlclose(
void *handle)
{
Obj_Entry *root = _rtld_dlcheck(handle);
if (root == NULL)
return -1;
_rtld_debug.r_state = RT_DELETE;
_rtld_debug_state();
--root->dl_refcount;
_rtld_unref_object_dag(root);
if (root->refcount == 0) { /* We are finished with some objects. */
Obj_Entry *obj;
Obj_Entry **linkp;
/* Finalize objects that are about to be unmapped. */
for (obj = _rtld_objlist->next; obj != NULL; obj = obj->next)
if (obj->refcount == 0 && obj->fini != NULL)
(*obj->fini)();
/* Unmap all objects that are no longer referenced. */
linkp = &_rtld_objlist->next;
while((obj = *linkp) != NULL) {
if (obj->refcount == 0) {
munmap(obj->mapbase, obj->mapsize);
free(obj->path);
while(obj->needed != NULL) {
Needed_Entry *needed = obj->needed;
obj->needed = needed->next;
free(needed);
}
_rtld_linkmap_delete(obj);
*linkp = obj->next;
free(obj);
} else
linkp = &obj->next;
}
}
_rtld_debug.r_state = RT_CONSISTENT;
_rtld_debug_state();
return 0;
}
char *
_rtld_dlerror(
void)
{
char *msg = error_message;
error_message = NULL;
return msg;
}
void *
_rtld_dlopen(
const char *name,
int mode)
{
Obj_Entry **old_obj_tail = _rtld_objtail;
Obj_Entry *obj = NULL;
_rtld_debug.r_state = RT_ADD;
_rtld_debug_state();
if (name == NULL) {
obj = _rtld_objmain;
} else {
char *path = _rtld_find_library(name, NULL);
if (path != NULL)
obj = _rtld_load_object(path);
}
if (obj != NULL) {
++obj->dl_refcount;
if (*old_obj_tail != NULL) { /* We loaded something new. */
assert(*old_obj_tail == obj);
/* FIXME - Clean up properly after an error. */
if (_rtld_load_needed_objects(obj) == -1) {
--obj->dl_refcount;
obj = NULL;
} else if (_rtld_relocate_objects(obj, mode == RTLD_NOW) == -1) {
--obj->dl_refcount;
obj = NULL;
} else {
_rtld_call_init_functions(obj);
}
}
}
_rtld_debug.r_state = RT_CONSISTENT;
_rtld_debug_state();
return obj;
}
void *
_rtld_dlsym(
void *handle,
const char *name)
{
const Obj_Entry *obj = _rtld_dlcheck(handle);
const Elf_Sym *def;
const Obj_Entry *defobj;
if (obj == NULL)
return NULL;
/*
* FIXME - This isn't correct. The search should include the whole
* DAG rooted at the given object.
*/
def = _rtld_find_symdef(_rtld_objlist, 0, name, obj, &defobj, false);
if (def != NULL)
return defobj->relocbase + def->st_value;
_rtld_error("Undefined symbol \"%s\"", name);
return NULL;
}
/*
* 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);
xvsnprintf(buf, sizeof buf, fmt, ap);
error_message = buf;
va_end(ap);
}
void
_rtld_debug_state(
void)
{
/* do nothing */
}
void
_rtld_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;
if (_rtld_debug.r_map == NULL) {
_rtld_debug.r_map = l;
return;
}
for (prev = _rtld_debug.r_map; prev->l_next != NULL; prev = prev->l_next)
;
l->l_prev = prev;
prev->l_next = l;
l->l_next = NULL;
}
void
_rtld_linkmap_delete(
Obj_Entry *obj)
{
struct link_map *l = &obj->linkmap;
if (l->l_prev == NULL) {
if ((_rtld_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;
}