rtld to support __thread tls

[David Xu]

Oh, forgot to attach file rtld_tls.h which is needed
by libthread_xu, please copy it into src/libexec/rtld-elf
David Xu wrote:
Matthew Dillon wrote:

    Well, lets not let this slip through the cracks.  We want __thread 
/ TLS
    support and we have the GDT infrastructure to do it now.    Maybe you
    should push your current patch set to David Xu with a quick 
summary and     you and he can discuss architectural issues over the 
weekend.

                    -Matt
                    Matthew Dillon                     
<dillon at xxxxxxxxxxxxx>


Hi All,

Because Joerg is working on rtld, I just picked up an relative easier
task --- hack all necessary code to support __thread for static libary,
I have spent two hours to work out all patches, please see attached
file, they works on my machine (a SMP box).
I don't know what was committed into rtld by Joerg yet, since I have to
fix some broken code due to FreeBSD's swappable kernel stack issue,
not have enough time. =(
Note, this only works for static library! the patches do not affect
shared objects, however applying the patch should be safe.
you should use gcc3 to compile sample code tls_test.c. the gcc 2.95 does
not support __thread.
I use csh, so:
# setenv CCVER gcc34
# cc -o tls_test tls_test.c -static -lthread_xu
David Xu
/*-
 * Copyright (c) 2004 Doug Rabson
 * 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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: src/libexec/rtld-elf/rtld_tls.h,v 1.1 2004/08/03 08:50:58 dfr Exp $
 */

/*
 * Semi-public interface from thread libraries to rtld for managing
 * TLS.
 */

#ifndef _RTLD_TLS_H_
#define	_RTLD_TLS_H_

/*
 * Allocate a TLS block for a new thread. The memory allocated will
 * include 'tcbsize' bytes aligned to a 'tcbalign' boundary (in bytes)
 * for the thread library's private purposes. The location of the TCB
 * block is returned by this function. For architectures using
 * 'Variant I' TLS, the thread local storage follows the TCB, and for
 * 'Variant II', the thread local storage precedes it. For
 * architectures using the 'Variant II' model (e.g. i386, amd64,
 * sparc64), the TCB must begin with two pointer fields which are used
 * by rtld for its TLS implementation. For the 'Variant I' model, the
 * TCB must begin with a single pointer field for rtld's
 * implementation.
 *
 * If the value of 'oldtls' is non-NULL, the new TLS block will be
 * initialised using the values contained in 'oldtls' and 'oldtls'
 * will be freed. This is typically used when initialising a thread
 * library to migrate from using the initial bootstrap TLS block
 * created by rtld to one which contains suitable thread library
 * private data.
 *
 * The value returned from this function is suitable for installing
 * directly into the thread pointer register.
 */
extern void *_rtld_allocate_tls(void* oldtls, size_t tcbsize, size_t tcbalign);

/*
 * Free a TLS block allocated using _rtld_allocate_tls(). The tcbsize
 * and tcbalign parameters must be the same as those used to allocate
 * the block.
 */
extern void _rtld_free_tls(void *tcb, size_t tcbsize, size_t tcbalign);

#endif