libc: adjust brk(0) to return the existing break, and use it to initialize sbrk()

          --- old/usr/src/lib/libc/common/sys/brk.s
          +++ new/usr/src/lib/libc/common/sys/brk.s

   1    1  /*
   2    2   * CDDL HEADER START
   3    3   *
   4    4   * The contents of this file are subject to the terms of the
   5    5   * Common Development and Distribution License (the "License").
   6    6   * You may not use this file except in compliance with the License.
   7    7   *
   8    8   * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9    9   * or http://www.opensolaris.org/os/licensing.
  10   10   * See the License for the specific language governing permissions
  11   11   * and limitations under the License.
  12   12   *
  13   13   * When distributing Covered Code, include this CDDL HEADER in each
  14   14   * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15   15   * If applicable, add the following below this CDDL HEADER, with the
  16   16   * fields enclosed by brackets "[]" replaced with your own identifying
  17   17   * information: Portions Copyright [yyyy] [name of copyright owner]
  18   18   *
  19   19   * CDDL HEADER END
  20   20   */
  21   21  /*
  22   22   * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
  23   23   * Use is subject to license terms.
  24   24   */
  25   25  
  26   26          .file   "brk.s"
  27   27  
  28   28  #include "SYS.h"
  29   29  

  30   30  /*
  31   31   * _brk_unlocked() simply traps into the kernel to set the brk.  It
  32   32   * returns 0 if the break was successfully set, or -1 otherwise.
  33   33   * It doesn't enforce any alignment and it doesn't perform any locking.
  34   34   * _brk_unlocked() is only called from brk() and _sbrk_unlocked().
  35   35   */
  36   36  
  37   37          ENTRY_NP(_brk_unlocked)
  38   38          SYSTRAP_RVAL1(brk)
  39   39          SYSCERROR
  40      -        RETC
       40 +        RET
  41   41          SET_SIZE(_brk_unlocked)
    

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