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📄 Makefile(2.41 KB)
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📁 aarch64
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📄 debug.c(4.3 KB)
📄 debug.h(2.03 KB)
📁 i386
📄 libmap.c(9.54 KB)
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📄 libmap.h(169 B)
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📄 paths.h(2.55 KB)
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📁 powerpc64
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📁 rtld-libc
📄 rtld.1(12.49 KB)
📄 rtld.c(156.2 KB)
📄 rtld.h(16.54 KB)
📄 rtld_lock.c(10.42 KB)
📄 rtld_lock.h(2.51 KB)
📄 rtld_malloc.c(7.81 KB)
📄 rtld_malloc.h(1.77 KB)
📄 rtld_printf.c(10.5 KB)
📄 rtld_printf.h(2.04 KB)
📄 rtld_tls.h(2.96 KB)
📄 rtld_utrace.h(2.25 KB)
📁 tests
📄 xmalloc.c(2.6 KB)

Editing: rtld_lock.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * 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 take
 * from machine/atomic.h.
 */

#include <sys/param.h>
#include <sys/signalvar.h>
#include <signal.h>
#include <stdlib.h>
#include <time.h>

#include "debug.h"
#include "rtld.h"
#include "rtld_machdep.h"
#include "rtld_libc.h"

void _rtld_thread_init(struct RtldLockInfo *) __exported;
void _rtld_atfork_pre(int *) __exported;
void _rtld_atfork_post(int *) __exported;

#define WAFLAG		0x1	/* A writer holds the lock */
#define RC_INCR		0x2	/* Adjusts count of readers desiring lock */

typedef struct Struct_Lock {
	volatile u_int lock;
	void *base;
} Lock;

static sigset_t fullsigmask, oldsigmask;
static int thread_flag, wnested;
static uint32_t fsigblock;

static void *
def_lock_create(void)
{
    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
sig_fastunblock(void)
{
	uint32_t oldval;

assert((fsigblock & ~SIGFASTBLOCK_FLAGS) >= SIGFASTBLOCK_INC);
	oldval = atomic_fetchadd_32(&fsigblock, -SIGFASTBLOCK_INC);
	if (oldval == (SIGFASTBLOCK_PEND | SIGFASTBLOCK_INC))
		__sys_sigfastblock(SIGFASTBLOCK_UNBLOCK, NULL);
}

static void
def_wlock_acquire(void *lock)
{
	Lock *l;
	sigset_t tmp_oldsigmask;

l = (Lock *)lock;
	if (ld_fast_sigblock) {
		for (;;) {
			atomic_add_32(&fsigblock, SIGFASTBLOCK_INC);
			if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG))
				break;
			sig_fastunblock();
		}
	} else {
		for (;;) {
			sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask);
			if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG))
				break;
			sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL);
		}
		if (atomic_fetchadd_int(&wnested, 1) == 0)
			oldsigmask = tmp_oldsigmask;
	}
}

static void
def_lock_release(void *lock)
{
	Lock *l;

l = (Lock *)lock;
	if ((l->lock & WAFLAG) == 0)
		atomic_add_rel_int(&l->lock, -RC_INCR);
	else {
		atomic_add_rel_int(&l->lock, -WAFLAG);
		if (ld_fast_sigblock)
			sig_fastunblock();
		else if (atomic_fetchadd_int(&wnested, -1) == 1)
			sigprocmask(SIG_SETMASK, &oldsigmask, NULL);
	}
}

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	3
static 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];
rtld_lock_t	rtld_phdr_lock = &rtld_locks[2];

void
rlock_acquire(rtld_lock_t lock, RtldLockState *lockstate)
{