337 lines
8.4 KiB
C
337 lines
8.4 KiB
C
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/*-
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* Copyright 1999, 2000 John D. Polstra.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* from: FreeBSD: src/libexec/rtld-elf/sparc64/lockdflt.c,v 1.3 2002/10/09
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* $FreeBSD$
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*/
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/*
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* Thread locking implementation for the dynamic linker.
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*
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* We use the "simple, non-scalable reader-preference lock" from:
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*
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* J. M. Mellor-Crummey and M. L. Scott. "Scalable Reader-Writer
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* Synchronization for Shared-Memory Multiprocessors." 3rd ACM Symp. on
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* Principles and Practice of Parallel Programming, April 1991.
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*
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* In this algorithm the lock is a single word. Its low-order bit is
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* set when a writer holds the lock. The remaining high-order bits
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* contain a count of readers desiring the lock. The algorithm requires
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* atomic "compare_and_store" and "add" operations, which we implement
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* using assembly language sequences in "rtld_start.S".
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*/
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#include <signal.h>
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#include <stdlib.h>
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#include <time.h>
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#include "debug.h"
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#include "rtld.h"
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#include "rtld_machdep.h"
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#define WAFLAG 0x1 /* A writer holds the lock */
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#define RC_INCR 0x2 /* Adjusts count of readers desiring lock */
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typedef struct Struct_Lock {
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volatile int lock;
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void *base;
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} Lock;
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static sigset_t fullsigmask, oldsigmask;
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static int thread_flag;
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static void *
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def_lock_create()
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{
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void *base;
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char *p;
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uintptr_t r;
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Lock *l;
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/*
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* Arrange for the lock to occupy its own cache line. First, we
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* optimistically allocate just a cache line, hoping that malloc
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* will give us a well-aligned block of memory. If that doesn't
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* work, we allocate a larger block and take a well-aligned cache
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* line from it.
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*/
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base = xmalloc(CACHE_LINE_SIZE);
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p = (char *)base;
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if ((uintptr_t)p % CACHE_LINE_SIZE != 0) {
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free(base);
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base = xmalloc(2 * CACHE_LINE_SIZE);
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p = (char *)base;
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if ((r = (uintptr_t)p % CACHE_LINE_SIZE) != 0)
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p += CACHE_LINE_SIZE - r;
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}
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l = (Lock *)p;
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l->base = base;
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l->lock = 0;
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return l;
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}
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static void
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def_lock_destroy(void *lock)
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{
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Lock *l = (Lock *)lock;
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free(l->base);
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}
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static void
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def_rlock_acquire(void *lock)
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{
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Lock *l = (Lock *)lock;
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atomic_add_acq_int(&l->lock, RC_INCR);
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while (l->lock & WAFLAG)
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; /* Spin */
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}
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static void
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def_wlock_acquire(void *lock)
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{
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Lock *l = (Lock *)lock;
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sigset_t tmp_oldsigmask;
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for ( ; ; ) {
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sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask);
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if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG))
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break;
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sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL);
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}
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oldsigmask = tmp_oldsigmask;
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}
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static void
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def_lock_release(void *lock)
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{
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Lock *l = (Lock *)lock;
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if ((l->lock & WAFLAG) == 0)
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atomic_add_rel_int(&l->lock, -RC_INCR);
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else {
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atomic_add_rel_int(&l->lock, -WAFLAG);
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sigprocmask(SIG_SETMASK, &oldsigmask, NULL);
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}
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}
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#if __i386__
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/*
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* Import a crude exclusive lock implementation for i386 processors.
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* This file will be removed once i386 support is deprecated in favor
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* of i486+.
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*/
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#include "i386/lockdflt.c"
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#endif
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static int
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def_thread_set_flag(int mask)
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{
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int old_val = thread_flag;
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thread_flag |= mask;
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return (old_val);
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}
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static int
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def_thread_clr_flag(int mask)
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{
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int old_val = thread_flag;
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thread_flag &= ~mask;
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return (old_val);
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}
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/*
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* Public interface exposed to the rest of the dynamic linker.
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*/
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static struct RtldLockInfo lockinfo;
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static struct RtldLockInfo deflockinfo;
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static __inline__ int
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thread_mask_set(int mask)
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{
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return lockinfo.thread_set_flag(mask);
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}
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static __inline__ void
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thread_mask_clear(int mask)
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{
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lockinfo.thread_clr_flag(mask);
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}
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#define RTLD_LOCK_CNT 2
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struct rtld_lock {
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void *handle;
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int mask;
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} rtld_locks[RTLD_LOCK_CNT];
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rtld_lock_t rtld_bind_lock = &rtld_locks[0];
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rtld_lock_t rtld_libc_lock = &rtld_locks[1];
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int
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rlock_acquire(rtld_lock_t lock)
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{
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if (thread_mask_set(lock->mask)) {
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dbg("rlock_acquire: recursed");
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return (0);
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}
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lockinfo.rlock_acquire(lock->handle);
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return (1);
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}
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int
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wlock_acquire(rtld_lock_t lock)
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{
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if (thread_mask_set(lock->mask)) {
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dbg("wlock_acquire: recursed");
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return (0);
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}
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lockinfo.wlock_acquire(lock->handle);
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return (1);
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}
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void
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rlock_release(rtld_lock_t lock, int locked)
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{
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if (locked == 0)
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return;
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thread_mask_clear(lock->mask);
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lockinfo.lock_release(lock->handle);
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}
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void
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wlock_release(rtld_lock_t lock, int locked)
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{
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if (locked == 0)
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return;
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thread_mask_clear(lock->mask);
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lockinfo.lock_release(lock->handle);
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}
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void
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lockdflt_init()
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{
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int i;
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deflockinfo.rtli_version = RTLI_VERSION;
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deflockinfo.lock_create = def_lock_create;
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deflockinfo.lock_destroy = def_lock_destroy;
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deflockinfo.rlock_acquire = def_rlock_acquire;
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deflockinfo.wlock_acquire = def_wlock_acquire;
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deflockinfo.lock_release = def_lock_release;
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deflockinfo.thread_set_flag = def_thread_set_flag;
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deflockinfo.thread_clr_flag = def_thread_clr_flag;
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deflockinfo.at_fork = NULL;
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for (i = 0; i < RTLD_LOCK_CNT; i++) {
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rtld_locks[i].mask = (1 << i);
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rtld_locks[i].handle = NULL;
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}
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#if __i386__
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if (!cpu_supports_cmpxchg()) {
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/* It's a cruddy old 80386. */
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deflockinfo.rlock_acquire = lock80386_acquire;
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deflockinfo.wlock_acquire = lock80386_acquire;
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deflockinfo.lock_release = lock80386_release;
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}
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#endif
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memcpy(&lockinfo, &deflockinfo, sizeof(lockinfo));
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_rtld_thread_init(NULL);
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/*
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* Construct a mask to block all signals except traps which might
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* conceivably be generated within the dynamic linker itself.
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*/
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sigfillset(&fullsigmask);
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sigdelset(&fullsigmask, SIGILL);
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sigdelset(&fullsigmask, SIGTRAP);
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sigdelset(&fullsigmask, SIGABRT);
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sigdelset(&fullsigmask, SIGEMT);
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sigdelset(&fullsigmask, SIGFPE);
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sigdelset(&fullsigmask, SIGBUS);
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sigdelset(&fullsigmask, SIGSEGV);
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sigdelset(&fullsigmask, SIGSYS);
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}
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/*
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* Callback function to allow threads implementation to
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* register their own locking primitives if the default
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* one is not suitable.
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* The current context should be the only context
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* executing at the invocation time.
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*/
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void
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_rtld_thread_init(struct RtldLockInfo *pli)
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{
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int flags, i;
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void *locks[RTLD_LOCK_CNT];
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/* disable all locking while this function is running */
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flags = thread_mask_set(~0);
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if (pli == NULL)
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pli = &deflockinfo;
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for (i = 0; i < RTLD_LOCK_CNT; i++)
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if ((locks[i] = pli->lock_create()) == NULL)
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break;
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if (i < RTLD_LOCK_CNT) {
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while (--i >= 0)
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pli->lock_destroy(locks[i]);
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abort();
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}
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for (i = 0; i < RTLD_LOCK_CNT; i++) {
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if (rtld_locks[i].handle == NULL)
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continue;
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if (flags & rtld_locks[i].mask)
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lockinfo.lock_release(rtld_locks[i].handle);
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lockinfo.lock_destroy(rtld_locks[i].handle);
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}
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for (i = 0; i < RTLD_LOCK_CNT; i++) {
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rtld_locks[i].handle = locks[i];
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if (flags & rtld_locks[i].mask)
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pli->wlock_acquire(rtld_locks[i].handle);
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}
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lockinfo.lock_create = pli->lock_create;
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lockinfo.lock_destroy = pli->lock_destroy;
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lockinfo.rlock_acquire = pli->rlock_acquire;
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lockinfo.wlock_acquire = pli->wlock_acquire;
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lockinfo.lock_release = pli->lock_release;
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lockinfo.thread_set_flag = pli->thread_set_flag;
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lockinfo.thread_clr_flag = pli->thread_clr_flag;
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lockinfo.at_fork = pli->at_fork;
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/* restore thread locking state, this time with new locks */
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thread_mask_clear(~0);
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thread_mask_set(flags);
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dbg("_rtld_thread_init: done");
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}
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