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/*
* Copyright (c) 2006, David Xu <davidxu@freebsd.org>
* 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 unmodified, 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.
*
* 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.
*
* $FreeBSD$
*
*/
/*
* A lockless rwlock for rtld.
*/
#include <sys/cdefs.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <link.h>
#include <stdlib.h>
#include <string.h>
#include "libc_private.h"
#include "rtld_lock.h"
#include "thr_private.h"
#undef errno
extern int errno;
static int _thr_rtld_clr_flag(int);
static void *_thr_rtld_lock_create(void);
static void _thr_rtld_lock_destroy(void *);
static void _thr_rtld_lock_release(void *);
static void _thr_rtld_rlock_acquire(void *);
static int _thr_rtld_set_flag(int);
static void _thr_rtld_wlock_acquire(void *);
struct rtld_lock {
struct urwlock lock;
char _pad[CACHE_LINE_SIZE - sizeof(struct urwlock)];
};
static struct rtld_lock lock_place[MAX_RTLD_LOCKS] __aligned(CACHE_LINE_SIZE);
static int busy_places;
static void *
_thr_rtld_lock_create(void)
{
int locki;
struct rtld_lock *l;
static const char fail[] = "_thr_rtld_lock_create failed\n";
for (locki = 0; locki < MAX_RTLD_LOCKS; locki++) {
if ((busy_places & (1 << locki)) == 0)
break;
}
if (locki == MAX_RTLD_LOCKS) {
write(2, fail, sizeof(fail) - 1);
return (NULL);
}
busy_places |= (1 << locki);
l = &lock_place[locki];
l->lock.rw_flags = URWLOCK_PREFER_READER;
return (l);
}
static void
_thr_rtld_lock_destroy(void *lock)
{
int locki;
size_t i;
locki = (struct rtld_lock *)lock - &lock_place[0];
for (i = 0; i < sizeof(struct rtld_lock); ++i)
((char *)lock)[i] = 0;
busy_places &= ~(1 << locki);
}
#define SAVE_ERRNO() { \
if (curthread != _thr_initial) \
errsave = curthread->error; \
else \
errsave = errno; \
}
#define RESTORE_ERRNO() { \
if (curthread != _thr_initial) \
curthread->error = errsave; \
else \
errno = errsave; \
}
static void
_thr_rtld_rlock_acquire(void *lock)
{
struct pthread *curthread;
struct rtld_lock *l;
int errsave;
curthread = _get_curthread();
SAVE_ERRNO();
l = (struct rtld_lock *)lock;
THR_CRITICAL_ENTER(curthread);
while (_thr_rwlock_rdlock(&l->lock, 0, NULL) != 0)
;
curthread->rdlock_count++;
RESTORE_ERRNO();
}
static void
_thr_rtld_wlock_acquire(void *lock)
{
struct pthread *curthread;
struct rtld_lock *l;
int errsave;
curthread = _get_curthread();
SAVE_ERRNO();
l = (struct rtld_lock *)lock;
THR_CRITICAL_ENTER(curthread);
while (_thr_rwlock_wrlock(&l->lock, NULL) != 0)
;
RESTORE_ERRNO();
}
static void
_thr_rtld_lock_release(void *lock)
{
struct pthread *curthread;
struct rtld_lock *l;
int32_t state;
int errsave;
curthread = _get_curthread();
SAVE_ERRNO();
l = (struct rtld_lock *)lock;
state = l->lock.rw_state;
if (_thr_rwlock_unlock(&l->lock) == 0) {
if ((state & URWLOCK_WRITE_OWNER) == 0)
curthread->rdlock_count--;
THR_CRITICAL_LEAVE(curthread);
}
RESTORE_ERRNO();
}
static int
_thr_rtld_set_flag(int mask __unused)
{
/*
* The caller's code in rtld-elf is broken, it is not signal safe,
* just return zero to fool it.
*/
return (0);
}
static int
_thr_rtld_clr_flag(int mask __unused)
{
return (0);
}
void
_thr_rtld_init(void)
{
struct RtldLockInfo li;
struct pthread *curthread;
ucontext_t *uc;
long dummy = -1;
int uc_len;
curthread = _get_curthread();
/* force to resolve _umtx_op PLT */
_umtx_op_err((struct umtx *)&dummy, UMTX_OP_WAKE, 1, 0, 0);
/* force to resolve errno() PLT */
__error();
/* force to resolve memcpy PLT */
memcpy(&dummy, &dummy, sizeof(dummy));
mprotect(NULL, 0, 0);
_rtld_get_stack_prot();
li.lock_create = _thr_rtld_lock_create;
li.lock_destroy = _thr_rtld_lock_destroy;
li.rlock_acquire = _thr_rtld_rlock_acquire;
li.wlock_acquire = _thr_rtld_wlock_acquire;
li.lock_release = _thr_rtld_lock_release;
li.thread_set_flag = _thr_rtld_set_flag;
li.thread_clr_flag = _thr_rtld_clr_flag;
li.at_fork = NULL;
/*
* Preresolve the symbols needed for the fork interposer. We
* call _rtld_atfork_pre() and _rtld_atfork_post() with NULL
* argument to indicate that no actual locking inside the
* functions should happen. Neither rtld compat locks nor
* libthr rtld locks cannot work there:
* - compat locks do not handle the case of two locks taken
* in write mode (the signal mask for the thread is corrupted);
* - libthr locks would work, but locked rtld_bind_lock prevents
* symbol resolution for _rtld_atfork_post.
*/
_rtld_atfork_pre(NULL);
_rtld_atfork_post(NULL);
_malloc_prefork();
_malloc_postfork();
syscall(SYS_getpid);
/* mask signals, also force to resolve __sys_sigprocmask PLT */
_thr_signal_block(curthread);
_rtld_thread_init(&li);
_thr_signal_unblock(curthread);
uc_len = __getcontextx_size();
uc = alloca(uc_len);
getcontext(uc);
__fillcontextx2((char *)uc);
}
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