NetBSD/libexec/ld.elf_so/rtld.c

677 lines
16 KiB
C

/* $NetBSD: rtld.c,v 1.23 1999/08/19 23:42:15 christos 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"
#if !defined(lint)
#include "sysident.h"
#endif
/*
* Debugging support.
*/
typedef void (*funcptr) __P((void));
/*
* Function declarations.
*/
static void _rtld_init __P((caddr_t));
static void _rtld_exit __P((void));
Elf_Addr _rtld __P((Elf_Word *));
/*
* 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;
#ifdef VARPSZ
int _rtld_pagesz; /* Page size, as provided by kernel */
#endif
Search_Path *_rtld_default_paths;
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 __P((Obj_Entry *));
static void _rtld_call_init_functions __P((Obj_Entry *));
static Obj_Entry *_rtld_dlcheck __P((void *));
static void _rtld_unref_object_dag __P((Obj_Entry *));
static void
_rtld_call_fini_functions(first)
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(first)
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(mapbase)
caddr_t mapbase;
{
Obj_Entry objself;/* The dynamic linker shared object */
#ifdef RTLD_RELOCATE_SELF
int dodebug = false;
#else
int dodebug = true;
#endif
memset(&objself, 0, sizeof objself);
/* Conjure up an Obj_Entry structure for the dynamic linker. */
objself.path = NULL;
objself.rtld = true;
objself.mapbase = mapbase;
#if defined(__mips__)
/*
* mips and ld.so currently linked at load address,
* so no relocation needed
*/
objself.relocbase = 0;
#else
objself.relocbase = mapbase;
#endif
objself.pltgot = NULL;
#ifdef OLD_GOT
objself.dynamic = (Elf_Dyn *) _GLOBAL_OFFSET_TABLE_[0];
#else
objself.dynamic = (Elf_Dyn *) & _DYNAMIC;
#endif
#ifdef RTLD_RELOCATE_SELF
/* We have not been relocated yet, so fix the dynamic address */
objself.dynamic = (Elf_Dyn *)
((u_long) mapbase + (char *) objself.dynamic);
#endif /* RTLD_RELOCATE_SELF */
_rtld_digest_dynamic(&objself);
#ifdef __alpha__
/* XXX XXX XXX */
objself.pltgot = NULL;
#endif
assert(objself.needed == NULL);
#if !defined(__mips__) && !defined(__i386__)
/* no relocation for mips/i386 */
assert(!objself.textrel);
#endif
_rtld_relocate_objects(&objself, true, dodebug);
/*
* Now that we relocated ourselves, we can use globals.
*/
_rtld_objself = objself;
_rtld_objself.path = _rtld_path;
_rtld_add_paths(&_rtld_default_paths, RTLD_DEFAULT_LIBRARY_PATH, true);
/*
* Set up the _rtld_objlist pointer, so that rtld symbols can be found.
*/
_rtld_objlist = &_rtld_objself;
/* 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()
{
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, the dynamic
* linker's exit procedure in sp[0], and a pointer to the main object in
* sp[1].
*/
Elf_Addr
_rtld(sp)
Elf_Word *sp;
{
const AuxInfo *pAUX_base, *pAUX_entry, *pAUX_execfd, *pAUX_phdr,
*pAUX_phent, *pAUX_phnum;
#ifdef VARPSZ
const AuxInfo *pAUX_pagesz;
#endif
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;
#if defined(RTLD_DEBUG) && !defined(RTLD_RELOCATE_SELF)
int i = 0;
#endif
/*
* 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 */
#if defined(RTLD_DEBUG) && !defined(RTLD_RELOCATE_SELF)
dbg(("sp = %p, argc = %ld, argv = %p <%s>\n", sp, (long)sp[2],
&sp[3], (char *) sp[3]));
dbg(("got is at %p, dynamic is at %p\n",
_GLOBAL_OFFSET_TABLE_, &_DYNAMIC));
debug = 1;
dbg(("_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 */
#if defined(RTLD_DEBUG) && !defined(RTLD_RELOCATE_SELF)
dbg(("env[%d] = %p %s\n", i++, (void *)sp[-1], (char *)sp[-1]));
#endif
}
aux = (const AuxInfo *) sp;
/* Digest the auxiliary vector. */
pAUX_base = pAUX_entry = pAUX_execfd = NULL;
pAUX_phdr = pAUX_phent = pAUX_phnum = NULL;
#ifdef VARPSZ
pAUX_pagesz = NULL;
#endif
for (auxp = aux; auxp->au_id != AUX_null; ++auxp) {
switch (auxp->au_id) {
case AUX_base:
pAUX_base = auxp;
break;
case AUX_entry:
pAUX_entry = auxp;
break;
case AUX_execfd:
pAUX_execfd = auxp;
break;
case AUX_phdr:
pAUX_phdr = auxp;
break;
case AUX_phent:
pAUX_phent = auxp;
break;
case AUX_phnum:
pAUX_phnum = auxp;
break;
#ifdef VARPSZ
case AUX_pagesz:
pAUX_pagesz = auxp;
break;
#endif
}
}
/* Initialize and relocate ourselves. */
assert(pAUX_base != NULL);
_rtld_init((caddr_t) pAUX_base->au_v);
#ifdef VARPSZ
assert(pAUX_pagesz != NULL);
_rtld_pagesz = (int)pAUX_pagesz->au_v;
#endif
#ifdef RTLD_DEBUG
dbg(("_ctype_ is %p\n", _ctype_));
#endif
__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) {
#ifdef DEBUG
const char *ld_debug = getenv("LD_DEBUG");
if (ld_debug != NULL && *ld_debug != '\0')
debug = 1;
#endif
_rtld_add_paths(&_rtld_paths, getenv("LD_LIBRARY_PATH"), true);
}
_rtld_process_hints(&_rtld_paths, _PATH_LD_HINTS, true);
dbg(("%s is initialized, base address = %p", __progname,
(void *) pAUX_base->au_v));
/*
* Load the main program, or process its program header if it is
* already loaded.
*/
if (pAUX_execfd != NULL) { /* Load the main program. */
int fd = pAUX_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(pAUX_phdr != NULL);
phdr = (const Elf_Phdr *) pAUX_phdr->au_v;
assert(pAUX_phnum != NULL);
phnum = pAUX_phnum->au_v;
assert(pAUX_phent != NULL);
assert(pAUX_phent->au_v == sizeof(Elf_Phdr));
assert(pAUX_entry != NULL);
entry = (caddr_t) pAUX_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;
/*
* Pre-load user-specified objects after the main program but before
* any shared object dependencies.
*/
dbg(("preloading objects"));
if (_rtld_trust && _rtld_preload(getenv("LD_PRELOAD"), true) == -1)
_rtld_die();
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, true) == -1)
_rtld_die();
dbg(("doing copy relocations"));
if (_rtld_do_copy_relocations(_rtld_objmain, true) == -1)
_rtld_die();
dbg(("calling _init functions"));
_rtld_call_init_functions(_rtld_objmain->next);
dbg(("control at program entry point = %p, obj = %p, exit = %p",
_rtld_objmain->entry, _rtld_objmain, _rtld_exit));
/*
* 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()
{
const char *msg = _rtld_dlerror();
if (msg == NULL)
msg = "Fatal error";
xerrx(1, "%s\n", msg);
}
static Obj_Entry *
_rtld_dlcheck(handle)
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(root)
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(handle)
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;
if (obj->next == NULL)
_rtld_objtail = linkp;
free(obj);
} else
linkp = &obj->next;
}
}
_rtld_debug.r_state = RT_CONSISTENT;
_rtld_debug_state();
return 0;
}
char *
_rtld_dlerror()
{
char *msg = error_message;
error_message = NULL;
return msg;
}
void *
_rtld_dlopen(name, mode)
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, _rtld_objmain);
if (path != NULL)
obj = _rtld_load_object(path, true);
}
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 & 3) == RTLD_NOW, true) == -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(handle, name)
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
#ifdef __STDC__
_rtld_error(const char *fmt,...)
#else
_rtld_error(va_alist)
va_dcl
#endif
{
static char buf[512];
va_list ap;
#ifdef __STDC__
va_start(ap, fmt);
#else
const char *fmt;
va_start(ap);
fmt = va_arg(ap, const char *);
#endif
xvsnprintf(buf, sizeof buf, fmt, ap);
error_message = buf;
va_end(ap);
}
void
_rtld_debug_state()
{
/* do nothing */
}
void
_rtld_linkmap_add(obj)
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 (_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)
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;
}