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Diffstat (limited to 'libexec/rtld-elf/powerpc/lockdflt.c')
| -rw-r--r-- | libexec/rtld-elf/powerpc/lockdflt.c | 169 |
1 files changed, 169 insertions, 0 deletions
diff --git a/libexec/rtld-elf/powerpc/lockdflt.c b/libexec/rtld-elf/powerpc/lockdflt.c new file mode 100644 index 0000000..70dc733 --- /dev/null +++ b/libexec/rtld-elf/powerpc/lockdflt.c @@ -0,0 +1,169 @@ +/*- + * 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/alpha/lockdflt.c,v 1.6 2000/07/17 + * $FreeBSD$ + */ + +/* + * 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 <machine/atomic.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 void * +lock_create(void *context) +{ + 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 +lock_destroy(void *lock) +{ + Lock *l = (Lock *)lock; + + free(l->base); +} + +static void +rlock_acquire(void *lock) +{ + Lock *l = (Lock *)lock; + + atomic_add_acq_int(&l->lock, RC_INCR); + while (l->lock & WAFLAG) + ; /* Spin */ +} + +static void +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 +rlock_release(void *lock) +{ + Lock *l = (Lock *)lock; + + atomic_add_rel_int(&l->lock, -RC_INCR); +} + +static void +wlock_release(void *lock) +{ + Lock *l = (Lock *)lock; + + atomic_add_rel_int(&l->lock, -WAFLAG); + sigprocmask(SIG_SETMASK, &oldsigmask, NULL); +} + +void +lockdflt_init(LockInfo *li) +{ + li->context = NULL; + li->lock_create = lock_create; + li->rlock_acquire = rlock_acquire; + li->wlock_acquire = wlock_acquire; + li->rlock_release = rlock_release; + li->wlock_release = wlock_release; + li->lock_destroy = lock_destroy; + li->context_destroy = 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); +} |
