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+/*-
+ * Copyright 1999, 2000 John D. Polstra.
+ * 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.
+ *
+ * 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.
+ *
+ * from: FreeBSD: src/libexec/rtld-elf/sparc64/lockdflt.c,v 1.3 2002/10/09
+ * $FreeBSD$
+ */
+
+/*
+ * Thread locking implementation for the dynamic linker.
+ *
+ * We use the "simple, non-scalable reader-preference lock" from:
+ *
+ * J. M. Mellor-Crummey and M. L. Scott. "Scalable Reader-Writer
+ * Synchronization for Shared-Memory Multiprocessors." 3rd ACM Symp. on
+ * Principles and Practice of Parallel Programming, April 1991.
+ *
+ * In this algorithm the lock is a single word. Its low-order bit is
+ * set when a writer holds the lock. The remaining high-order bits
+ * contain a count of readers desiring the lock. The algorithm requires
+ * atomic "compare_and_store" and "add" operations, which we implement
+ * using assembly language sequences in "rtld_start.S".
+ */
+
+#include <signal.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include "debug.h"
+#include "rtld.h"
+#include "rtld_machdep.h"
+
+#define WAFLAG 0x1 /* A writer holds the lock */
+#define RC_INCR 0x2 /* Adjusts count of readers desiring lock */
+
+typedef struct Struct_Lock {
+ volatile int lock;
+ void *base;
+} Lock;
+
+static sigset_t fullsigmask, oldsigmask;
+static int thread_flag;
+
+static void *
+def_lock_create()
+{
+ void *base;
+ char *p;
+ uintptr_t r;
+ Lock *l;
+
+ /*
+ * Arrange for the lock to occupy its own cache line. First, we
+ * optimistically allocate just a cache line, hoping that malloc
+ * will give us a well-aligned block of memory. If that doesn't
+ * work, we allocate a larger block and take a well-aligned cache
+ * line from it.
+ */
+ base = xmalloc(CACHE_LINE_SIZE);
+ p = (char *)base;
+ if ((uintptr_t)p % CACHE_LINE_SIZE != 0) {
+ free(base);
+ base = xmalloc(2 * CACHE_LINE_SIZE);
+ p = (char *)base;
+ if ((r = (uintptr_t)p % CACHE_LINE_SIZE) != 0)
+ p += CACHE_LINE_SIZE - r;
+ }
+ l = (Lock *)p;
+ l->base = base;
+ l->lock = 0;
+ return l;
+}
+
+static void
+def_lock_destroy(void *lock)
+{
+ Lock *l = (Lock *)lock;
+
+ free(l->base);
+}
+
+static void
+def_rlock_acquire(void *lock)
+{
+ Lock *l = (Lock *)lock;
+
+ atomic_add_acq_int(&l->lock, RC_INCR);
+ while (l->lock & WAFLAG)
+ ; /* Spin */
+}
+
+static void
+def_wlock_acquire(void *lock)
+{
+ Lock *l = (Lock *)lock;
+ sigset_t tmp_oldsigmask;
+
+ for ( ; ; ) {
+ sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask);
+ if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG))
+ break;
+ sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL);
+ }
+ oldsigmask = tmp_oldsigmask;
+}
+
+static void
+def_lock_release(void *lock)
+{
+ Lock *l = (Lock *)lock;
+
+ if ((l->lock & WAFLAG) == 0)
+ atomic_add_rel_int(&l->lock, -RC_INCR);
+ else {
+ atomic_add_rel_int(&l->lock, -WAFLAG);
+ sigprocmask(SIG_SETMASK, &oldsigmask, NULL);
+ }
+}
+
+#if __i386__
+/*
+ * Import a crude exclusive lock implementation for i386 processors.
+ * This file will be removed once i386 support is deprecated in favor
+ * of i486+.
+ */
+#include "i386/lockdflt.c"
+
+#endif
+
+static int
+def_thread_set_flag(int mask)
+{
+ int old_val = thread_flag;
+ thread_flag |= mask;
+ return (old_val);
+}
+
+static int
+def_thread_clr_flag(int mask)
+{
+ int old_val = thread_flag;
+ thread_flag &= ~mask;
+ return (old_val);
+}
+
+/*
+ * Public interface exposed to the rest of the dynamic linker.
+ */
+static struct RtldLockInfo lockinfo;
+static struct RtldLockInfo deflockinfo;
+
+static __inline__ int
+thread_mask_set(int mask)
+{
+ return lockinfo.thread_set_flag(mask);
+}
+
+static __inline__ void
+thread_mask_clear(int mask)
+{
+ lockinfo.thread_clr_flag(mask);
+}
+
+#define RTLD_LOCK_CNT 2
+struct rtld_lock {
+ void *handle;
+ int mask;
+} rtld_locks[RTLD_LOCK_CNT];
+
+rtld_lock_t rtld_bind_lock = &rtld_locks[0];
+rtld_lock_t rtld_libc_lock = &rtld_locks[1];
+
+int
+rlock_acquire(rtld_lock_t lock)
+{
+ if (thread_mask_set(lock->mask)) {
+ dbg("rlock_acquire: recursed");
+ return (0);
+ }
+ lockinfo.rlock_acquire(lock->handle);
+ return (1);
+}
+
+int
+wlock_acquire(rtld_lock_t lock)
+{
+ if (thread_mask_set(lock->mask)) {
+ dbg("wlock_acquire: recursed");
+ return (0);
+ }
+ lockinfo.wlock_acquire(lock->handle);
+ return (1);
+}
+
+void
+rlock_release(rtld_lock_t lock, int locked)
+{
+ if (locked == 0)
+ return;
+ thread_mask_clear(lock->mask);
+ lockinfo.lock_release(lock->handle);
+}
+
+void
+wlock_release(rtld_lock_t lock, int locked)
+{
+ if (locked == 0)
+ return;
+ thread_mask_clear(lock->mask);
+ lockinfo.lock_release(lock->handle);
+}
+
+void
+lockdflt_init()
+{
+ int i;
+
+ deflockinfo.rtli_version = RTLI_VERSION;
+ deflockinfo.lock_create = def_lock_create;
+ deflockinfo.lock_destroy = def_lock_destroy;
+ deflockinfo.rlock_acquire = def_rlock_acquire;
+ deflockinfo.wlock_acquire = def_wlock_acquire;
+ deflockinfo.lock_release = def_lock_release;
+ deflockinfo.thread_set_flag = def_thread_set_flag;
+ deflockinfo.thread_clr_flag = def_thread_clr_flag;
+ deflockinfo.at_fork = NULL;
+
+ for (i = 0; i < RTLD_LOCK_CNT; i++) {
+ rtld_locks[i].mask = (1 << i);
+ rtld_locks[i].handle = NULL;
+ }
+
+#if __i386__
+ if (!cpu_supports_cmpxchg()) {
+ /* It's a cruddy old 80386. */
+ deflockinfo.rlock_acquire = lock80386_acquire;
+ deflockinfo.wlock_acquire = lock80386_acquire;
+ deflockinfo.lock_release = lock80386_release;
+ }
+#endif
+
+ memcpy(&lockinfo, &deflockinfo, sizeof(lockinfo));
+ _rtld_thread_init(NULL);
+ /*
+ * Construct a mask to block all signals except traps which might
+ * conceivably be generated within the dynamic linker itself.
+ */
+ sigfillset(&fullsigmask);
+ sigdelset(&fullsigmask, SIGILL);
+ sigdelset(&fullsigmask, SIGTRAP);
+ sigdelset(&fullsigmask, SIGABRT);
+ sigdelset(&fullsigmask, SIGEMT);
+ sigdelset(&fullsigmask, SIGFPE);
+ sigdelset(&fullsigmask, SIGBUS);
+ sigdelset(&fullsigmask, SIGSEGV);
+ sigdelset(&fullsigmask, SIGSYS);
+}
+
+/*
+ * Callback function to allow threads implementation to
+ * register their own locking primitives if the default
+ * one is not suitable.
+ * The current context should be the only context
+ * executing at the invocation time.
+ */
+void
+_rtld_thread_init(struct RtldLockInfo *pli)
+{
+ int flags, i;
+ void *locks[RTLD_LOCK_CNT];
+
+ /* disable all locking while this function is running */
+ flags = thread_mask_set(~0);
+
+ if (pli == NULL)
+ pli = &deflockinfo;
+
+
+ for (i = 0; i < RTLD_LOCK_CNT; i++)
+ if ((locks[i] = pli->lock_create()) == NULL)
+ break;
+
+ if (i < RTLD_LOCK_CNT) {
+ while (--i >= 0)
+ pli->lock_destroy(locks[i]);
+ abort();
+ }
+
+ for (i = 0; i < RTLD_LOCK_CNT; i++) {
+ if (rtld_locks[i].handle == NULL)
+ continue;
+ if (flags & rtld_locks[i].mask)
+ lockinfo.lock_release(rtld_locks[i].handle);
+ lockinfo.lock_destroy(rtld_locks[i].handle);
+ }
+
+ for (i = 0; i < RTLD_LOCK_CNT; i++) {
+ rtld_locks[i].handle = locks[i];
+ if (flags & rtld_locks[i].mask)
+ pli->wlock_acquire(rtld_locks[i].handle);
+ }
+
+ lockinfo.lock_create = pli->lock_create;
+ lockinfo.lock_destroy = pli->lock_destroy;
+ lockinfo.rlock_acquire = pli->rlock_acquire;
+ lockinfo.wlock_acquire = pli->wlock_acquire;
+ lockinfo.lock_release = pli->lock_release;
+ lockinfo.thread_set_flag = pli->thread_set_flag;
+ lockinfo.thread_clr_flag = pli->thread_clr_flag;
+ lockinfo.at_fork = pli->at_fork;
+
+ /* restore thread locking state, this time with new locks */
+ thread_mask_clear(~0);
+ thread_mask_set(flags);
+ dbg("_rtld_thread_init: done");
+}
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