libexec/rtld-elf/rtld_tls.h

   1 /*-
   2  * SPDX-License-Identifier: BSD-2-Clause
   3  *
   4  * Copyright (c) 2004 Doug Rabson
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  26  * SUCH DAMAGE.
  27  */
  28
  29 /*
  30  * Semi-public interface from thread libraries to rtld for managing
  31  * TLS.
  32  */
  33
  34 #ifndef _RTLD_TLS_H_
  35 #define _RTLD_TLS_H_
  36
  37 /*
  38  * Allocate a TLS block for a new thread. The memory allocated will
  39  * include 'tcbsize' bytes aligned to a 'tcbalign' boundary (in bytes)
  40  * for the thread library's private purposes. The location of the TCB
  41  * block is returned by this function. For architectures using
  42  * 'Variant I' TLS, the thread local storage follows the TCB, and for
  43  * 'Variant II', the thread local storage precedes it. For
  44  * architectures using the 'Variant II' model (e.g. i386, amd64) the
  45  * TCB must begin with two pointer fields which are used by rtld for
  46  * its TLS implementation. For the 'Variant I' model, the TCB must
  47  * begin with a single pointer field for rtld's implementation.
  48  *
  49  * If the value of 'oldtls' is non-NULL, the new TLS block will be
  50  * initialised using the values contained in 'oldtls' and 'oldtls'
  51  * will be freed. This is typically used when initialising a thread
  52  * library to migrate from using the initial bootstrap TLS block
  53  * created by rtld to one which contains suitable thread library
  54  * private data.
  55  *
  56  * The value returned from this function is suitable for installing
  57  * directly into the thread pointer register.
  58  */
  59 void *_rtld_allocate_tls(void *oldtls, size_t tcbsize, size_t tcbalign)
  60     __exported;
  61
  62 /*
  63  * Free a TLS block allocated using _rtld_allocate_tls(). The tcbsize
  64  * and tcbalign parameters must be the same as those used to allocate
  65  * the block.
  66  */
  67 void _rtld_free_tls(void *tcb, size_t tcbsize, size_t tcbalign) __exported;
  68
  69 #endif