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/* $NetBSD: rtld.c,v 1.212 2022/09/13 10:18:58 riastradh Exp $ */
/*
* Copyright 1996 John D. Polstra.
* Copyright 1996 Matt Thomas <matt@3am-software.com>
* Copyright 2002 Charles M. Hannum <root@ihack.net>
* 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 <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: rtld.c,v 1.212 2022/09/13 10:18:58 riastradh Exp $");
#endif /* not lint */
#include <sys/param.h>
#include <sys/atomic.h>
#include <sys/mman.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <lwp.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <dirent.h>
#include <ctype.h>
#include <dlfcn.h>
#include "debug.h"
#include "rtld.h"
#if !defined(lint)
#include "sysident.h"
#endif
/*
* Function declarations.
*/
static void _rtld_init(caddr_t, caddr_t, const char *);
static void _rtld_exit(void);
Elf_Addr _rtld(Elf_Addr *, Elf_Addr);
/*
* Data declarations.
*/
static char *error_message; /* Message for dlopen(), or NULL */
struct r_debug _rtld_debug; /* The SVR4 interface for the debugger */
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 */
u_int _rtld_objcount; /* Number of objects in _rtld_objlist */
u_int _rtld_objloads; /* Number of objects loaded in _rtld_objlist */
u_int _rtld_objgen; /* Generation count for _rtld_objlist */
const char _rtld_path[] = _PATH_RTLD;
/* Initialize a fake symbol for resolving undefined weak references. */
Elf_Sym _rtld_sym_zero = {
.st_info = ELF_ST_INFO(STB_GLOBAL, STT_NOTYPE),
.st_shndx = SHN_ABS,
};
size_t _rtld_pagesz; /* Page size, as provided by kernel */
Search_Path *_rtld_default_paths;
Search_Path *_rtld_paths;
Library_Xform *_rtld_xforms;
static void *auxinfo;
/*
* Global declarations normally provided by crt0.
*/
char *__progname;
char **environ;
static volatile bool _rtld_mutex_may_recurse;
#if defined(RTLD_DEBUG)
#ifndef __sh__
extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
#else /* 32-bit SuperH */
register Elf_Addr *_GLOBAL_OFFSET_TABLE_ asm("r12");
#endif
#endif /* RTLD_DEBUG */
extern Elf_Dyn _DYNAMIC;
static void _rtld_call_fini_functions(sigset_t *, int);
static void _rtld_call_init_functions(sigset_t *);
static void _rtld_initlist_visit(Objlist *, Obj_Entry *, int);
static void _rtld_initlist_tsort(Objlist *, int);
static Obj_Entry *_rtld_dlcheck(void *);
static void _rtld_init_dag(Obj_Entry *);
static void _rtld_init_dag1(Obj_Entry *, Obj_Entry *);
static void _rtld_objlist_remove(Objlist *, Obj_Entry *);
static void _rtld_objlist_clear(Objlist *);
static void _rtld_unload_object(sigset_t *, Obj_Entry *, bool);
static void _rtld_unref_dag(Obj_Entry *);
static Obj_Entry *_rtld_obj_from_addr(const void *);
static void _rtld_fill_dl_phdr_info(const Obj_Entry *, struct dl_phdr_info *);
static inline void
_rtld_call_initfini_function(fptr_t func, sigset_t *mask)
{
_rtld_exclusive_exit(mask);
(*func)();
_rtld_exclusive_enter(mask);
}
static void
_rtld_call_fini_function(Obj_Entry *obj, sigset_t *mask, u_int cur_objgen)
{
if (obj->fini_arraysz == 0 && (obj->fini == NULL || obj->fini_called))
return;
if (obj->fini != NULL && !obj->fini_called) {
dbg (("calling fini function %s at %p%s", obj->path,
(void *)obj->fini,
obj->z_initfirst ? " (DF_1_INITFIRST)" : ""));
obj->fini_called = 1;
_rtld_call_initfini_function(obj->fini, mask);
}
#ifdef HAVE_INITFINI_ARRAY
/*
* Now process the fini_array if it exists. Simply go from
* start to end. We need to make restartable so just advance
* the array pointer and decrement the size each time through
* the loop.
*/
while (obj->fini_arraysz > 0 && _rtld_objgen == cur_objgen) {
fptr_t fini = *obj->fini_array++;
obj->fini_arraysz--;
dbg (("calling fini array function %s at %p%s", obj->path,
(void *)fini,
obj->z_initfirst ? " (DF_1_INITFIRST)" : ""));
_rtld_call_initfini_function(fini, mask);
}
#endif /* HAVE_INITFINI_ARRAY */
}
static void
_rtld_call_fini_functions(sigset_t *mask, int force)
{
Objlist_Entry *elm;
Objlist finilist;
u_int cur_objgen;
dbg(("_rtld_call_fini_functions(%d)", force));
restart:
cur_objgen = ++_rtld_objgen;
SIMPLEQ_INIT(&finilist);
_rtld_initlist_tsort(&finilist, 1);
/* First pass: objects _not_ marked with DF_1_INITFIRST. */
SIMPLEQ_FOREACH(elm, &finilist, link) {
Obj_Entry * const obj = elm->obj;
if (!obj->z_initfirst) {
if (obj->refcount > 0 && !force) {
continue;
}
/*
* XXX This can race against a concurrent dlclose().
* XXX In that case, the object could be unmapped before
* XXX the fini() call or the fini_array has completed.
*/
_rtld_call_fini_function(obj, mask, cur_objgen);
if (_rtld_objgen != cur_objgen) {
dbg(("restarting fini iteration"));
_rtld_objlist_clear(&finilist);
goto restart;
}
}
}
/* Second pass: objects marked with DF_1_INITFIRST. */
SIMPLEQ_FOREACH(elm, &finilist, link) {
Obj_Entry * const obj = elm->obj;
if (obj->refcount > 0 && !force) {
continue;
}
/* XXX See above for the race condition here */
_rtld_call_fini_function(obj, mask, cur_objgen);
if (_rtld_objgen != cur_objgen) {
dbg(("restarting fini iteration"));
_rtld_objlist_clear(&finilist);
goto restart;
}
}
_rtld_objlist_clear(&finilist);
}
static void
_rtld_call_init_function(Obj_Entry *obj, sigset_t *mask, u_int cur_objgen)
{
if (obj->init_arraysz == 0 && (obj->init_called || obj->init == NULL))
return;
if (!obj->init_called && obj->init != NULL) {
dbg (("calling init function %s at %p%s",
obj->path, (void *)obj->init,
obj->z_initfirst ? " (DF_1_INITFIRST)" : ""));
obj->init_called = 1;
_rtld_call_initfini_function(obj->init, mask);
}
#ifdef HAVE_INITFINI_ARRAY
/*
* Now process the init_array if it exists. Simply go from
* start to end. We need to make restartable so just advance
* the array pointer and decrement the size each time through
* the loop.
*/
while (obj->init_arraysz > 0 && _rtld_objgen == cur_objgen) {
fptr_t init = *obj->init_array++;
obj->init_arraysz--;
dbg (("calling init_array function %s at %p%s",
obj->path, (void *)init,
obj->z_initfirst ? " (DF_1_INITFIRST)" : ""));
_rtld_call_initfini_function(init, mask);
}
#endif /* HAVE_INITFINI_ARRAY */
}
static bool
_rtld_call_ifunc_functions(sigset_t *mask, Obj_Entry *obj, u_int cur_objgen)
{
if (obj->ifunc_remaining
#if defined(IFUNC_NONPLT)
|| obj->ifunc_remaining_nonplt
#endif
) {
_rtld_call_ifunc(obj, mask, cur_objgen);
if (_rtld_objgen != cur_objgen) {
return true;
}
}
return false;
}
static void
_rtld_call_init_functions(sigset_t *mask)
{
Objlist_Entry *elm;
Objlist initlist;
u_int cur_objgen;
dbg(("_rtld_call_init_functions()"));
restart:
cur_objgen = ++_rtld_objgen;
SIMPLEQ_INIT(&initlist);
_rtld_initlist_tsort(&initlist, 0);
/* First pass: objects with IRELATIVE relocations. */
SIMPLEQ_FOREACH(elm, &initlist, link) {
if (_rtld_call_ifunc_functions(mask, elm->obj, cur_objgen)) {
dbg(("restarting init iteration"));
_rtld_objlist_clear(&initlist);
goto restart;
}
}
/*
* XXX: For historic reasons, init/fini of the main object are called
* from crt0. Don't introduce that mistake for ifunc, so look at
* the head of _rtld_objlist that _rtld_initlist_tsort skipped.
*/
if (_rtld_call_ifunc_functions(mask, _rtld_objlist, cur_objgen)) {
dbg(("restarting init iteration"));
_rtld_objlist_clear(&initlist);
goto restart;
}
/* Second pass: objects marked with DF_1_INITFIRST. */
SIMPLEQ_FOREACH(elm, &initlist, link) {
Obj_Entry * const obj = elm->obj;
if (obj->z_initfirst) {
_rtld_call_init_function(obj, mask, cur_objgen);
if (_rtld_objgen != cur_objgen) {
dbg(("restarting init iteration"));
_rtld_objlist_clear(&initlist);
goto restart;
}
}
}
/* Third pass: all other objects. */
SIMPLEQ_FOREACH(elm, &initlist, link) {
_rtld_call_init_function(elm->obj, mask, cur_objgen);
if (_rtld_objgen != cur_objgen) {
dbg(("restarting init iteration"));
_rtld_objlist_clear(&initlist);
goto restart;
}
}
_rtld_objlist_clear(&initlist);
}
/*
* 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 create an Obj_Entry for the dynamic linker and
* to resolve the PLT relocation for platforms that need it (those that
* define __HAVE_FUNCTION_DESCRIPTORS
*/
static void
_rtld_init(caddr_t mapbase, caddr_t relocbase, const char *execname)
{
const Elf_Ehdr *ehdr;
/* Conjure up an Obj_Entry structure for the dynamic linker. */
_rtld_objself.path = __UNCONST(_rtld_path);
_rtld_objself.pathlen = sizeof(_rtld_path)-1;
_rtld_objself.rtld = true;
_rtld_objself.mapbase = mapbase;
_rtld_objself.relocbase = relocbase;
_rtld_objself.dynamic = (Elf_Dyn *) &_DYNAMIC;
_rtld_objself.strtab = "_rtld_sym_zero";
/*
* Set value to -relocbase so that
*
* _rtld_objself.relocbase + _rtld_sym_zero.st_value == 0
*
* This allows unresolved references to weak symbols to be computed
* to a value of 0.
*/
_rtld_sym_zero.st_value = -(uintptr_t)relocbase;
_rtld_digest_dynamic(_rtld_path, &_rtld_objself);
assert(!_rtld_objself.needed);
#if !defined(__hppa__)
assert(!_rtld_objself.pltrel && !_rtld_objself.pltrela);
#else
_rtld_relocate_plt_objects(&_rtld_objself);
#endif
#if !defined(__mips__) && !defined(__hppa__)
assert(!_rtld_objself.pltgot);
#endif
#if !defined(__arm__) && !defined(__mips__) && !defined(__sh__)
/* ARM, MIPS and SH{3,5} have a bogus DT_TEXTREL. */
assert(!_rtld_objself.textrel);
#endif
_rtld_add_paths(execname, &_rtld_default_paths,
RTLD_DEFAULT_LIBRARY_PATH);
#ifdef RTLD_ARCH_SUBDIR
_rtld_add_paths(execname, &_rtld_default_paths,
RTLD_DEFAULT_LIBRARY_PATH "/" RTLD_ARCH_SUBDIR);
#endif
/* Make the object list empty. */
_rtld_objlist = NULL;
_rtld_objtail = &_rtld_objlist;
_rtld_objcount = 0;
_rtld_debug.r_version = R_DEBUG_VERSION;
_rtld_debug.r_brk = _rtld_debug_state;
_rtld_debug.r_state = RT_CONSISTENT;
_rtld_debug.r_ldbase = _rtld_objself.relocbase;
ehdr = (Elf_Ehdr *)mapbase;
_rtld_objself.phdr = (Elf_Phdr *)((char *)mapbase + ehdr->e_phoff);
_rtld_objself.phsize = ehdr->e_phnum * sizeof(_rtld_objself.phdr[0]);
}
/*
* Cleanup procedure. It will be called (by the atexit() mechanism) just
* before the process exits.
*/
static void
_rtld_exit(void)
{
sigset_t mask;
dbg(("rtld_exit()"));
_rtld_exclusive_enter(&mask);
_rtld_call_fini_functions(&mask, 1);
_rtld_exclusive_exit(&mask);
}
__dso_public void *
_dlauxinfo(void)
{
return auxinfo;
}
/*
* 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(Elf_Addr *sp, Elf_Addr relocbase)
{
const AuxInfo *pAUX_base, *pAUX_entry, *pAUX_execfd, *pAUX_phdr,
*pAUX_phent, *pAUX_phnum, *pAUX_euid, *pAUX_egid,
*pAUX_ruid, *pAUX_rgid;
const AuxInfo *pAUX_pagesz;
char **env, **oenvp;
const AuxInfo *auxp;
Obj_Entry *obj;
Elf_Addr *const osp = sp;
bool bind_now = 0;
const char *ld_bind_now, *ld_preload, *ld_library_path;
const char **argv;
const char *execname;
long argc;
const char **real___progname;
const Obj_Entry **real___mainprog_obj;
char ***real_environ;
sigset_t mask;
#ifdef DEBUG
const char *ld_debug;
#endif
#ifdef RTLD_DEBUG
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)
debug = 1;
dbg(("sp = %p, argc = %ld, argv = %p <%s> relocbase %p", sp,
(long)sp[2], &sp[3], (char *) sp[3], (void *)relocbase));
#ifndef __x86_64__
dbg(("got is at %p, dynamic is at %p", _GLOBAL_OFFSET_TABLE_,
&_DYNAMIC));
#endif
#endif
sp += 2; /* skip over return argument space */
argv = (const char **) &sp[1];
argc = *(long *)sp;
sp += 2 + argc; /* Skip over argc, arguments, and NULL
* terminator */
env = (char **) sp;
while (*sp++ != 0) { /* Skip over environment, and NULL terminator */
#if defined(RTLD_DEBUG)
dbg(("env[%d] = %p %s", i++, (void *)sp[-1], (char *)sp[-1]));
#endif
}
auxinfo = (AuxInfo *) sp;
pAUX_base = pAUX_entry = pAUX_execfd = NULL;
pAUX_phdr = pAUX_phent = pAUX_phnum = NULL;
pAUX_euid = pAUX_ruid = pAUX_egid = pAUX_rgid = NULL;
pAUX_pagesz = NULL;
execname = NULL;
/* Digest the auxiliary vector. */
for (auxp = auxinfo; auxp->a_type != AT_NULL; ++auxp) {
switch (auxp->a_type) {
case AT_BASE:
pAUX_base = auxp;
break;
case AT_ENTRY:
pAUX_entry = auxp;
break;
case AT_EXECFD:
pAUX_execfd = auxp;
break;
case AT_PHDR:
pAUX_phdr = auxp;
break;
case AT_PHENT:
pAUX_phent = auxp;
break;
case AT_PHNUM:
pAUX_phnum = auxp;
break;
#ifdef AT_EUID
case AT_EUID:
pAUX_euid = auxp;
break;
case AT_RUID:
pAUX_ruid = auxp;
break;
case AT_EGID:
pAUX_egid = auxp;
break;
case AT_RGID:
pAUX_rgid = auxp;
break;
#endif
#ifdef AT_SUN_EXECNAME
case AT_SUN_EXECNAME:
execname = (const char *)(const void *)auxp->a_v;
break;
#endif
case AT_PAGESZ:
pAUX_pagesz = auxp;
break;
}
}
/* Initialize and relocate ourselves. */
if (pAUX_base == NULL) {
_rtld_error("Bad pAUX_base");
_rtld_die();
}
assert(pAUX_pagesz != NULL);
_rtld_pagesz = (int)pAUX_pagesz->a_v;
_rtld_init((caddr_t)pAUX_base->a_v, (caddr_t)relocbase, execname);
__progname = _rtld_objself.path;
environ = env;
_rtld_trust = ((pAUX_euid ? (uid_t)pAUX_euid->a_v : geteuid()) ==
(pAUX_ruid ? (uid_t)pAUX_ruid->a_v : getuid())) &&
((pAUX_egid ? (gid_t)pAUX_egid->a_v : getegid()) ==
(pAUX_rgid ? (gid_t)pAUX_rgid->a_v : getgid()));
#ifdef DEBUG
ld_debug = NULL;
#endif
ld_bind_now = NULL;
ld_library_path = NULL;
ld_preload = NULL;
/*
* Inline avoid using normal getenv/unsetenv here as the libc
* code is quite a bit more complicated.
*/
for (oenvp = env; *env != NULL; ++env) {
static const char bind_var[] = "LD_BIND_NOW=";
static const char debug_var[] = "LD_DEBUG=";
static const char path_var[] = "LD_LIBRARY_PATH=";
static const char preload_var[] = "LD_PRELOAD=";
#define LEN(x) (sizeof(x) - 1)
if ((*env)[0] != 'L' || (*env)[1] != 'D') {
/*
* Special case to skip most entries without
* the more expensive calls to strncmp.
*/
*oenvp++ = *env;
} else if (strncmp(*env, debug_var, LEN(debug_var)) == 0) {
if (_rtld_trust) {
#ifdef DEBUG
ld_debug = *env + LEN(debug_var);
#endif
*oenvp++ = *env;
}
} else if (strncmp(*env, bind_var, LEN(bind_var)) == 0) {
if (_rtld_trust) {
ld_bind_now = *env + LEN(bind_var);
*oenvp++ = *env;
}
} else if (strncmp(*env, path_var, LEN(path_var)) == 0) {
if (_rtld_trust) {
ld_library_path = *env + LEN(path_var);
*oenvp++ = *env;
}
} else if (strncmp(*env, preload_var, LEN(preload_var)) == 0) {
if (_rtld_trust) {
ld_preload = *env + LEN(preload_var);
*oenvp++ = *env;
}
} else {
*oenvp++ = *env;
}
#undef LEN
}
*oenvp++ = NULL;
if (ld_bind_now != NULL && *ld_bind_now != '\0')
bind_now = true;
if (_rtld_trust) {
#ifdef DEBUG
#ifdef RTLD_DEBUG
debug = 0;
#endif
if (ld_debug != NULL && *ld_debug != '\0')
debug = 1;
#endif
_rtld_add_paths(execname, &_rtld_paths, ld_library_path);
} else {
execname = NULL;
}
_rtld_process_hints(execname, &_rtld_paths, &_rtld_xforms,
_PATH_LD_HINTS);
dbg(("dynamic linker is initialized, mapbase=%p, relocbase=%p",
_rtld_objself.mapbase, _rtld_objself.relocbase));
/*
* 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->a_v;
const char *obj_name = argv[0] ? argv[0] : "main program";
dbg(("loading main program"));
_rtld_objmain = _rtld_map_object(obj_name, fd, NULL);
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->a_v;
assert(pAUX_phnum != NULL);
phnum = pAUX_phnum->a_v;
assert(pAUX_phent != NULL);
assert(pAUX_phent->a_v == sizeof(Elf_Phdr));
assert(pAUX_entry != NULL);
entry = (caddr_t) pAUX_entry->a_v;
_rtld_objmain = _rtld_digest_phdr(phdr, phnum, entry);
_rtld_objmain->path = xstrdup(argv[0] ? argv[0] :
"main program");
_rtld_objmain->pathlen = strlen(_rtld_objmain->path);
}
_rtld_objmain->mainprog = true;
/*
* Get the actual dynamic linker pathname from the executable if
* possible. (It should always be possible.) That ensures that
* the debugger will find the right dynamic linker even if a
* non-standard one is being used.
*/
if (_rtld_objmain->interp != NULL &&
strcmp(_rtld_objmain->interp, _rtld_objself.path) != 0) {
_rtld_objself.path = xstrdup(_rtld_objmain->interp);
_rtld_objself.pathlen = strlen(_rtld_objself.path);
}
dbg(("actual dynamic linker is %s", _rtld_objself.path));
_rtld_digest_dynamic(execname, _rtld_objmain);
/* Link the main program into the list of objects. */
*_rtld_objtail = _rtld_objmain;
_rtld_objtail = &_rtld_objmain->next;
_rtld_objcount++;
_rtld_objloads++;
_rtld_linkmap_add(_rtld_objmain);
_rtld_objself.path = xstrdup(_rtld_objself.path);
_rtld_linkmap_add(&_rtld_objself);
++_rtld_objmain->refcount;
_rtld_objmain->mainref = 1;
_rtld_objlist_push_tail(&_rtld_list_main, _rtld_objmain);
if (ld_preload) {
/*
* Pre-load user-specified objects after the main program
* but before any shared object dependencies.
*/
dbg(("preloading objects"));
if (_rtld_preload(ld_preload) == -1)
_rtld_die();
}
dbg(("loading needed objects"));
if (_rtld_load_needed_objects(_rtld_objmain, _RTLD_MAIN) == -1)
_rtld_die();
dbg(("checking for required versions"));
for (obj = _rtld_objlist; obj != NULL; obj = obj->next) {
if (_rtld_verify_object_versions(obj) == -1)
_rtld_die();
}
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
dbg(("initializing initial Thread Local Storage offsets"));
/*
* All initial objects get the TLS space from the static block.
*/
for (obj = _rtld_objlist; obj != NULL; obj = obj->next)
_rtld_tls_offset_allocate(obj);
#endif
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();
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
dbg(("initializing Thread Local Storage for main thread"));
/*
* Set up TLS area for the main thread.
* This has to be done after all relocations are processed,
* since .tdata may contain relocations.
*/
_rtld_tls_initial_allocation();
#endif
/*
* Set the __progname, environ and, __mainprog_obj before
* calling anything that might use them.
*/
real___progname = _rtld_objmain_sym("__progname");
if (real___progname) {
if (argv[0] != NULL) {
if ((*real___progname = strrchr(argv[0], '/')) == NULL)
(*real___progname) = argv[0];
else
(*real___progname)++;
} else {
(*real___progname) = NULL;
}
}
real_environ = _rtld_objmain_sym("environ");
if (real_environ)
*real_environ = environ;
/*
* Set __mainprog_obj for old binaries.
*/
real___mainprog_obj = _rtld_objmain_sym("__mainprog_obj");
if (real___mainprog_obj)
*real___mainprog_obj = _rtld_objmain;
_rtld_debug_state(); /* say hello to the debugger! */
_rtld_exclusive_enter(&mask);
dbg(("calling _init functions"));
_rtld_call_init_functions(&mask);
dbg(("control at program entry point = %p, obj = %p, exit = %p",
_rtld_objmain->entry, _rtld_objmain, _rtld_exit));
_rtld_exclusive_exit(&mask);
/*
* Return with the entry point and the exit procedure in at the top
* of stack.
*/
((void **) osp)[0] = _rtld_exit;
((void **) osp)[1] = __UNCONST(_rtld_compat_obj);
return (Elf_Addr) _rtld_objmain->entry;
}
void
_rtld_die(void)
{
const char *msg = dlerror();
if (msg == NULL)
msg = "Fatal error";
xerrx(1, "%s", 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) {
_rtld_error("Invalid shared object handle %p", handle);
return NULL;
}
return obj;
}
static void
_rtld_initlist_visit(Objlist* list, Obj_Entry *obj, int rev)
{
Needed_Entry* elm;
/* dbg(("_rtld_initlist_visit(%s)", obj->path)); */
if (obj->init_done)
return;
obj->init_done = 1;
for (elm = obj->needed; elm != NULL; elm = elm->next) {
if (elm->obj != NULL) {
_rtld_initlist_visit(list, elm->obj, rev);
}
}
if (rev) {
_rtld_objlist_push_head(list, obj);
} else {
_rtld_objlist_push_tail(list, obj);
}
}
static void
_rtld_initlist_tsort(Objlist* list, int rev)
{
dbg(("_rtld_initlist_tsort"));
Obj_Entry* obj;
/*
* We don't include objmain here (starting from next)
* because csu handles it
*/
for (obj = _rtld_objlist->next; obj; obj = obj->next) {
obj->init_done = 0;
}
for (obj = _rtld_objlist->next; obj; obj = obj->next) {
_rtld_initlist_visit(list, obj, rev);
}
}
static void
_rtld_init_dag(Obj_Entry *root)
{
_rtld_init_dag1(root, root);
}
static void
_rtld_init_dag1(Obj_Entry *root, Obj_Entry *obj)
{
const Needed_Entry *needed;
if (!obj->mainref) {
if (_rtld_objlist_find(&obj->dldags, root))
return;
dbg(("add %p (%s) to %p (%s) DAG", obj, obj->path, root,
root->path));
_rtld_objlist_push_tail(&obj->dldags, root);
_rtld_objlist_push_tail(&root->dagmembers, obj);
}
for (needed = obj->needed; needed != NULL; needed = needed->next)
if (needed->obj != NULL)
_rtld_init_dag1(root, needed->obj);
}
/*
* Note, this is called only for objects loaded by dlopen().
*/
static void
_rtld_unload_object(sigset_t *mask, Obj_Entry *root, bool do_fini_funcs)
{
_rtld_unref_dag(root);
if (root->refcount == 0) { /* We are finished with some objects. */
Obj_Entry *obj;
Obj_Entry **linkp;
Objlist_Entry *elm;
/* Finalize objects that are about to be unmapped. */
if (do_fini_funcs)
_rtld_call_fini_functions(mask, 0);
/* Remove the DAG from all objects' DAG lists. */
SIMPLEQ_FOREACH(elm, &root->dagmembers, link)
_rtld_objlist_remove(&elm->obj->dldags, root);
/* Remove the DAG from the RTLD_GLOBAL list. */
if (root->globalref) {
root->globalref = 0;
_rtld_objlist_remove(&_rtld_list_global, root);
}
/* Unmap all objects that are no longer referenced. */
linkp = &_rtld_objlist->next;
while ((obj = *linkp) != NULL) {
if (obj->refcount == 0) {
dbg(("unloading \"%s\"", obj->path));
if (obj->ehdr != MAP_FAILED)
munmap(obj->ehdr, _rtld_pagesz);
munmap(obj->mapbase, obj->mapsize);
_rtld_objlist_remove(&_rtld_list_global, obj);
_rtld_linkmap_delete(obj);
*linkp = obj->next;
_rtld_objcount--;
_rtld_obj_free(obj);
} else
linkp = &obj->next;
}
_rtld_objtail = linkp;
}
}
void
_rtld_ref_dag(Obj_Entry *root)
{
const Needed_Entry *needed;
assert(root);
++root->refcount;
dbg(("incremented reference on \"%s\" (%d)", root->path,
root->refcount));
for (needed = root->needed; needed != NULL;
needed = needed->next) {
if (needed->obj != NULL)
_rtld_ref_dag(needed->obj);
}
}
static void
_rtld_unref_dag(Obj_Entry *root)
{
assert(root);
assert(root->refcount != 0);
--root->refcount;
dbg(("decremented reference on \"%s\" (%d)", root->path,
root->refcount));
if (root->refcount == 0) {
const Needed_Entry *needed;
for (needed = root->needed; needed != NULL;
needed = needed->next) {
if (needed->obj != NULL)
_rtld_unref_dag(needed->obj);
}
}
}
__strong_alias(__dlclose,dlclose)
int
dlclose(void *handle)
{
Obj_Entry *root;
sigset_t mask;
dbg(("dlclose of %p", handle));
_rtld_exclusive_enter(&mask);
root = _rtld_dlcheck(handle);
if (root == NULL) {
_rtld_exclusive_exit(&mask);
return -1;
}
_rtld_debug.r_state = RT_DELETE;
_rtld_debug_state();
--root->dl_refcount;
_rtld_unload_object(&mask, root, true);
_rtld_debug.r_state = RT_CONSISTENT;
_rtld_debug_state();
_rtld_exclusive_exit(&mask);
return 0;
}
__strong_alias(__dlerror,dlerror)
char *
dlerror(void)
{
char *msg = error_message;
error_message = NULL;
return msg;
}
__strong_alias(__dlopen,dlopen)
void *
dlopen(const char *name, int mode)
{
Obj_Entry **old_obj_tail = _rtld_objtail;
Obj_Entry *obj = NULL;
int flags = _RTLD_DLOPEN;
bool nodelete;
bool now;
sigset_t mask;
int result;
dbg(("dlopen of %s %d", name, mode));
_rtld_exclusive_enter(&mask);
flags |= (mode & RTLD_GLOBAL) ? _RTLD_GLOBAL : 0;
flags |= (mode & RTLD_NOLOAD) ? _RTLD_NOLOAD : 0;
nodelete = (mode & RTLD_NODELETE) ? true : false;
now = ((mode & RTLD_MODEMASK) == RTLD_NOW) ? true : false;
_rtld_debug.r_state = RT_ADD;
_rtld_debug_state();
if (name == NULL) {
obj = _rtld_objmain;
obj->refcount++;
} else
obj = _rtld_load_library(name, _rtld_objmain, flags);
if (obj != NULL) {
++obj->dl_refcount;
if (*old_obj_tail != NULL) { /* We loaded something new. */
assert(*old_obj_tail == obj);
result = _rtld_load_needed_objects(obj, flags);
if (result != -1) {
Objlist_Entry *entry;
_rtld_init_dag(obj);
SIMPLEQ_FOREACH(entry, &obj->dagmembers, link) {
result = _rtld_verify_object_versions(entry->obj);
if (result == -1)
break;
}
}
if (result == -1 || _rtld_relocate_objects(obj,
(now || obj->z_now)) == -1) {
_rtld_unload_object(&mask, obj, false);
obj->dl_refcount--;
obj = NULL;
} else {
_rtld_call_init_functions(&mask);
}
}
if (obj != NULL) {
if ((nodelete || obj->z_nodelete) && !obj->ref_nodel) {
dbg(("dlopen obj %s nodelete", obj->path));
_rtld_ref_dag(obj);
obj->z_nodelete = obj->ref_nodel = true;
}
}
}
_rtld_debug.r_state = RT_CONSISTENT;
_rtld_debug_state();
_rtld_exclusive_exit(&mask);
return obj;
}
/*
* Find a symbol in the main program.
*/
void *
_rtld_objmain_sym(const char *name)
{
Elf_Hash hash;
const Elf_Sym *def;
const Obj_Entry *obj;
DoneList donelist;
hash.sysv = _rtld_sysv_hash(name);
hash.gnu = _rtld_gnu_hash(name);
obj = _rtld_objmain;
_rtld_donelist_init(&donelist);
def = _rtld_symlook_list(name, &hash, &_rtld_list_main, &obj, 0,
NULL, &donelist);
if (def != NULL)
return obj->relocbase + def->st_value;
return NULL;
}
#if defined(__powerpc__) && !defined(__clang__)
static __noinline void *
hackish_return_address(void)
{
#if __GNUC_PREREQ__(6,0)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wframe-address"
#endif
return __builtin_return_address(1);
#if __GNUC_PREREQ__(6,0)
#pragma GCC diagnostic pop
#endif
}
#endif
#ifdef __HAVE_FUNCTION_DESCRIPTORS
#define lookup_mutex_enter() _rtld_exclusive_enter(&mask)
#define lookup_mutex_exit() _rtld_exclusive_exit(&mask)
#else
#define lookup_mutex_enter() _rtld_shared_enter()
#define lookup_mutex_exit() _rtld_shared_exit()
#endif
static void *
do_dlsym(void *handle, const char *name, const Ver_Entry *ventry, void *retaddr)
{
const Obj_Entry *obj;
Elf_Hash hash;
const Elf_Sym *def;
const Obj_Entry *defobj;
DoneList donelist;
const u_int flags = SYMLOOK_DLSYM | SYMLOOK_IN_PLT;
#ifdef __HAVE_FUNCTION_DESCRIPTORS
sigset_t mask;
#endif
lookup_mutex_enter();
hash.sysv = _rtld_sysv_hash(name);
hash.gnu = _rtld_gnu_hash(name);
def = NULL;
defobj = NULL;
switch ((intptr_t)handle) {
case (intptr_t)NULL:
case (intptr_t)RTLD_NEXT:
case (intptr_t)RTLD_DEFAULT:
case (intptr_t)RTLD_SELF:
if ((obj = _rtld_obj_from_addr(retaddr)) == NULL) {
_rtld_error("Cannot determine caller's shared object");
lookup_mutex_exit();
return NULL;
}
switch ((intptr_t)handle) {
case (intptr_t)NULL: /* Just the caller's shared object. */
def = _rtld_symlook_obj(name, &hash, obj, flags, ventry);
defobj = obj;
break;
case (intptr_t)RTLD_NEXT: /* Objects after callers */
obj = obj->next;
/*FALLTHROUGH*/
case (intptr_t)RTLD_SELF: /* Caller included */
for (; obj; obj = obj->next) {
if ((def = _rtld_symlook_obj(name, &hash, obj,
flags, ventry)) != NULL) {
defobj = obj;
break;
}
}
/*
* Search the dynamic linker itself, and possibly
* resolve the symbol from there if it is not defined
* already or weak. This is how the application links
* to dynamic linker services such as dlopen.
*/
if (!def || ELF_ST_BIND(def->st_info) == STB_WEAK) {
const Elf_Sym *symp = _rtld_symlook_obj(name,
&hash, &_rtld_objself, flags, ventry);
if (symp != NULL) {
def = symp;
defobj = &_rtld_objself;
}
}
break;
case (intptr_t)RTLD_DEFAULT:
def = _rtld_symlook_default(name, &hash, obj, &defobj,
flags, ventry);
break;
default:
abort();
}
break;
default:
if ((obj = _rtld_dlcheck(handle)) == NULL) {
lookup_mutex_exit();
return NULL;
}
_rtld_donelist_init(&donelist);
if (obj->mainprog) {
/* Search main program and all libraries loaded by it */
def = _rtld_symlook_list(name, &hash, &_rtld_list_main,
&defobj, flags, ventry, &donelist);
} else {
Needed_Entry fake;
DoneList depth;
/* Search the object and all the libraries loaded by it. */
fake.next = NULL;
fake.obj = __UNCONST(obj);
fake.name = 0;
_rtld_donelist_init(&depth);
def = _rtld_symlook_needed(name, &hash, &fake, &defobj,
flags, ventry, &donelist, &depth);
}
break;
}
if (def != NULL) {
void *p;
if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
#ifdef __HAVE_FUNCTION_DESCRIPTORS
lookup_mutex_exit();
_rtld_shared_enter();
#endif
p = (void *)_rtld_resolve_ifunc(defobj, def);
_rtld_shared_exit();
return p;
}
#ifdef __HAVE_FUNCTION_DESCRIPTORS
if (ELF_ST_TYPE(def->st_info) == STT_FUNC) {
p = (void *)_rtld_function_descriptor_alloc(defobj,
def, 0);
lookup_mutex_exit();
return p;
}
#endif /* __HAVE_FUNCTION_DESCRIPTORS */
p = defobj->relocbase + def->st_value;
lookup_mutex_exit();
return p;
}
_rtld_error("Undefined symbol \"%s\"", name);
lookup_mutex_exit();
return NULL;
}
__strong_alias(__dlsym,dlsym)
void *
dlsym(void *handle, const char *name)
{
void *retaddr;
dbg(("dlsym of %s in %p", name, handle));
#if defined(__powerpc__) && !defined(__clang__)
retaddr = hackish_return_address();
#else
retaddr = __builtin_return_address(0);
#endif
return do_dlsym(handle, name, NULL, retaddr);
}
__strong_alias(__dlvsym,dlvsym)
void *
dlvsym(void *handle, const char *name, const char *version)
{
Ver_Entry *ventry = NULL;
Ver_Entry ver_entry;
void *retaddr;
dbg(("dlvsym of %s@%s in %p", name, version ? version : NULL, handle));
if (version != NULL) {
ver_entry.name = version;
ver_entry.file = NULL;
ver_entry.hash = _rtld_sysv_hash(version);
ver_entry.flags = 0;
ventry = &ver_entry;
}
#if defined(__powerpc__) && !defined(__clang__)
retaddr = hackish_return_address();
#else
retaddr = __builtin_return_address(0);
#endif
return do_dlsym(handle, name, ventry, retaddr);
}
__strong_alias(__dladdr,dladdr)
int
dladdr(const void *addr, Dl_info *info)
{
const Obj_Entry *obj;
const Elf_Sym *def, *best_def;
void *symbol_addr;
unsigned long symoffset;
#ifdef __HAVE_FUNCTION_DESCRIPTORS
sigset_t mask;
#endif
dbg(("dladdr of %p", addr));
lookup_mutex_enter();
#ifdef __HAVE_FUNCTION_DESCRIPTORS
addr = _rtld_function_descriptor_function(addr);
#endif /* __HAVE_FUNCTION_DESCRIPTORS */
obj = _rtld_obj_from_addr(addr);
if (obj == NULL) {
_rtld_error("No shared object contains address");
lookup_mutex_exit();
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.
*/
best_def = NULL;
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;
best_def = def;
/* Exact match? */
if (info->dli_saddr == addr)
break;
}
#ifdef __HAVE_FUNCTION_DESCRIPTORS
if (best_def != NULL && ELF_ST_TYPE(best_def->st_info) == STT_FUNC)
info->dli_saddr = (void *)_rtld_function_descriptor_alloc(obj,
best_def, 0);
#else
__USE(best_def);
#endif /* __HAVE_FUNCTION_DESCRIPTORS */
lookup_mutex_exit();
return 1;
}
__strong_alias(__dlinfo,dlinfo)
int
dlinfo(void *handle, int req, void *v)
{
const Obj_Entry *obj;
void *retaddr;
dbg(("dlinfo for %p %d", handle, req));
_rtld_shared_enter();
if (handle == RTLD_SELF) {
#if defined(__powerpc__) && !defined(__clang__)
retaddr = hackish_return_address();
#else
retaddr = __builtin_return_address(0);
#endif
if ((obj = _rtld_obj_from_addr(retaddr)) == NULL) {
_rtld_error("Cannot determine caller's shared object");
_rtld_shared_exit();
return -1;
}
} else {
if ((obj = _rtld_dlcheck(handle)) == NULL) {
_rtld_shared_exit();
return -1;
}
}
switch (req) {
case RTLD_DI_LINKMAP:
{
const struct link_map **map = v;
*map = &obj->linkmap;
break;
}
default:
_rtld_error("Invalid request");
_rtld_shared_exit();
return -1;
}
_rtld_shared_exit();
return 0;
}
static void
_rtld_fill_dl_phdr_info(const Obj_Entry *obj, struct dl_phdr_info *phdr_info)
{
phdr_info->dlpi_addr = (Elf_Addr)obj->relocbase;
/* XXX: wrong but not fixing it yet */
phdr_info->dlpi_name = obj->path;
phdr_info->dlpi_phdr = obj->phdr;
phdr_info->dlpi_phnum = obj->phsize / sizeof(obj->phdr[0]);
#if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
phdr_info->dlpi_tls_modid = obj->tlsindex;
phdr_info->dlpi_tls_data = obj->tlsinit;
#else
phdr_info->dlpi_tls_modid = 0;
phdr_info->dlpi_tls_data = 0;
#endif
phdr_info->dlpi_adds = _rtld_objloads;
phdr_info->dlpi_subs = _rtld_objloads - _rtld_objcount;
}
__strong_alias(__dl_iterate_phdr,dl_iterate_phdr);
int
dl_iterate_phdr(int (*callback)(struct dl_phdr_info *, size_t, void *), void *param)
{
struct dl_phdr_info phdr_info;
const Obj_Entry *obj;
int error = 0;
dbg(("dl_iterate_phdr"));
_rtld_shared_enter();
for (obj = _rtld_objlist; obj != NULL; obj = obj->next) {
_rtld_fill_dl_phdr_info(obj, &phdr_info);
/* XXXlocking: exit point */
error = callback(&phdr_info, sizeof(phdr_info), param);
if (error)
break;
}
if (error == 0) {
_rtld_fill_dl_phdr_info(&_rtld_objself, &phdr_info);
/* XXXlocking: exit point */
error = callback(&phdr_info, sizeof(phdr_info), param);
}
_rtld_shared_exit();
return error;
}
void
__dl_cxa_refcount(void *addr, ssize_t delta)
{
sigset_t mask;
Obj_Entry *obj;
if (delta == 0)
return;
dbg(("__dl_cxa_refcount of %p with %zd", addr, delta));
_rtld_exclusive_enter(&mask);
obj = _rtld_obj_from_addr(addr);
if (obj == NULL) {
dbg(("__dl_cxa_refcont: address not found"));
_rtld_error("No shared object contains address");
_rtld_exclusive_exit(&mask);
return;
}
if (delta > 0 && obj->cxa_refcount > SIZE_MAX - delta)
_rtld_error("Reference count overflow");
else if (delta < 0 && obj->cxa_refcount < -1 + (size_t)-(delta + 1))
_rtld_error("Reference count underflow");
else {
if (obj->cxa_refcount == 0)
++obj->refcount;
obj->cxa_refcount += delta;
dbg(("new reference count: %zu", obj->cxa_refcount));
if (obj->cxa_refcount == 0) {
--obj->refcount;
if (obj->refcount == 0)
_rtld_unload_object(&mask, obj, true);
}
}
_rtld_exclusive_exit(&mask);
}
pid_t __fork(void);
__dso_public pid_t
__locked_fork(int *my_errno)
{
pid_t result;
_rtld_shared_enter();
result = __fork();
if (result == -1)
*my_errno = errno;
_rtld_shared_exit();
return result;
}
/*
* 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)
{
#if defined(__hppa__)
__asm volatile("nop" ::: "memory");
#endif
/* Prevent optimizer from removing calls to this function */
__insn_barrier();
}
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->relocbase;
obj->linkmap.l_ld = obj->dynamic;
#ifdef __mips__
/* XXX This field is not standard and will be removed eventually. */
obj->linkmap.l_offs = obj->relocbase;
#endif
if (_rtld_debug.r_map == NULL) {
_rtld_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 = _rtld_debug.r_map;
prev->l_next != NULL && prev->l_next != &_rtld_objself.linkmap;
prev = prev->l_next);
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;
}
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;
}
static Obj_Entry *
_rtld_obj_from_addr(const void *addr)
{
Obj_Entry *obj;
for (obj = _rtld_objlist; obj != NULL; obj = obj->next) {
if (addr < (void *) obj->mapbase)
continue;
if (addr < (void *) (obj->mapbase + obj->mapsize))
return obj;
}
return NULL;
}
static void
_rtld_objlist_clear(Objlist *list)
{
while (!SIMPLEQ_EMPTY(list)) {
Objlist_Entry* elm = SIMPLEQ_FIRST(list);
SIMPLEQ_REMOVE_HEAD(list, link);
xfree(elm);
}
}
static void
_rtld_objlist_remove(Objlist *list, Obj_Entry *obj)
{
Objlist_Entry *elm;
if ((elm = _rtld_objlist_find(list, obj)) != NULL) {
SIMPLEQ_REMOVE(list, elm, Struct_Objlist_Entry, link);
xfree(elm);
}
}
#define RTLD_EXCLUSIVE_MASK 0x80000000U
static volatile unsigned int _rtld_mutex;
static volatile unsigned int _rtld_waiter_exclusive;
static volatile unsigned int _rtld_waiter_shared;
void
_rtld_shared_enter(void)
{
unsigned int cur;
lwpid_t waiter, self = 0;
for (;;) {
cur = _rtld_mutex;
/*
* First check if we are currently not exclusively locked.
*/
if ((cur & RTLD_EXCLUSIVE_MASK) == 0) {
/* Yes, so increment use counter */
if (atomic_cas_uint(&_rtld_mutex, cur, cur + 1) != cur)
continue;
membar_acquire();
return;
}
/*
* Someone has an exclusive lock. Puts us on the waiter list.
*/
if (!self)
self = _lwp_self();
if (cur == (self | RTLD_EXCLUSIVE_MASK)) {
if (_rtld_mutex_may_recurse)
return;
_rtld_error("%s: dead lock detected", __func__);
_rtld_die();
}
waiter = atomic_swap_uint(&_rtld_waiter_shared, self);
/*
* Check for race against _rtld_exclusive_exit before sleeping.
*/
membar_sync();
if ((_rtld_mutex & RTLD_EXCLUSIVE_MASK) ||
_rtld_waiter_exclusive)
_lwp_park(CLOCK_REALTIME, 0, NULL, 0,
__UNVOLATILE(&_rtld_mutex), NULL);
/* Try to remove us from the waiter list. */
atomic_cas_uint(&_rtld_waiter_shared, self, 0);
if (waiter)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
}
}
void
_rtld_shared_exit(void)
{
lwpid_t waiter;
/*
* Shared lock taken after an exclusive lock.
* Just assume this is a partial recursion.
*/
if (_rtld_mutex & RTLD_EXCLUSIVE_MASK)
return;
/*
* Wakeup LWPs waiting for an exclusive lock if this is the last
* LWP on the shared lock.
*/
membar_release();
if (atomic_dec_uint_nv(&_rtld_mutex))
return;
membar_sync();
if ((waiter = _rtld_waiter_exclusive) != 0)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
}
void
_rtld_exclusive_enter(sigset_t *mask)
{
lwpid_t waiter, self = _lwp_self();
unsigned int locked_value = (unsigned int)self | RTLD_EXCLUSIVE_MASK;
unsigned int cur;
sigset_t blockmask;
sigfillset(&blockmask);
sigdelset(&blockmask, SIGTRAP); /* Allow the debugger */
sigprocmask(SIG_BLOCK, &blockmask, mask);
for (;;) {
if (atomic_cas_uint(&_rtld_mutex, 0, locked_value) == 0) {
membar_acquire();
break;
}
waiter = atomic_swap_uint(&_rtld_waiter_exclusive, self);
membar_sync();
cur = _rtld_mutex;
if (cur == locked_value) {
_rtld_error("%s: dead lock detected", __func__);
_rtld_die();
}
if (cur)
_lwp_park(CLOCK_REALTIME, 0, NULL, 0,
__UNVOLATILE(&_rtld_mutex), NULL);
atomic_cas_uint(&_rtld_waiter_exclusive, self, 0);
if (waiter)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
}
}
void
_rtld_exclusive_exit(sigset_t *mask)
{
lwpid_t waiter;
membar_release();
_rtld_mutex = 0;
membar_sync();
if ((waiter = _rtld_waiter_exclusive) != 0)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
if ((waiter = _rtld_waiter_shared) != 0)
_lwp_unpark(waiter, __UNVOLATILE(&_rtld_mutex));
sigprocmask(SIG_SETMASK, mask, NULL);
}
int
_rtld_relro(const Obj_Entry *obj, bool wantmain)
{
#ifdef GNU_RELRO
/*
* If our VM page size is larger than the page size used by the
* linker when laying out the object, we could end up making data
* read-only that is unintended. Detect and avoid this situation.
* It may mean we are unable to protect everything we'd like, but
* it's better than crashing.
*/
uintptr_t relro_end = (uintptr_t)obj->relro_page + obj->relro_size;
uintptr_t relro_start = round_down((uintptr_t)obj->relro_page);
assert(relro_end >= relro_start);
size_t relro_size = round_down(relro_end) - relro_start;
if (relro_size == 0)
return 0;
if (wantmain != (obj ==_rtld_objmain))
return 0;
dbg(("RELRO %s %p %zx\n", obj->path, (void *)relro_start, relro_size));
if (mprotect((void *)relro_start, relro_size, PROT_READ) == -1) {
_rtld_error("%s: Cannot enforce relro " "protection: %s",
obj->path, xstrerror(errno));
return -1;
}
#endif
return 0;
}
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