8609 want a position independent CRT

          --- old/usr/src/lib/libc/i386/gen/makectxt.c
          +++ new/usr/src/lib/libc/i386/gen/makectxt.c

   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  /*
  23   23   * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24   24   * Use is subject to license terms.
  25   25   */
  26   26  
  27   27  /*      Copyright (c) 1988 AT&T */
  28   28  /*        All Rights Reserved   */
  29   29  
  30   30  #pragma weak _makecontext = makecontext
  31   31  
  32   32  #include "lint.h"
  33   33  #include <stdarg.h>
  34   34  #include <ucontext.h>
  35   35  #include <sys/stack.h>
  36   36  
  37   37  /*
  38   38   * The ucontext_t that the user passes in must have been primed with a
  39   39   * call to getcontext(2), have the uc_stack member set to reflect the
  40   40   * stack which this context will use, and have the uc_link member set
  41   41   * to the context which should be resumed when this context returns.
  42   42   * When makecontext() returns, the ucontext_t will be set to run the
  43   43   * given function with the given parameters on the stack specified by
  44   44   * uc_stack, and which will return to the ucontext_t specified by uc_link.
  45   45   */
  46   46  
  47   47  /*
  48   48   * The original i386 ABI said that the stack pointer need be only 4-byte
  49   49   * aligned before a function call (STACK_ALIGN == 4).  The ABI supplement
  50   50   * version 1.0 changed the required alignment to 16-byte for the benefit of
  51   51   * floating point code compiled using sse2.  The compiler assumes this
  52   52   * alignment and maintains it for calls it generates.  If the stack is
  53   53   * initially properly aligned, it will continue to be so aligned.  If it is
  54   54   * not initially so aligned, it will never become so aligned.
  55   55   *
  56   56   * One slightly confusing detail to keep in mind is that the 16-byte

  57   57   * alignment (%esp & 0xf == 0) is true just *before* the call instruction.
  58   58   * The call instruction will then push a return value, decrementing %esp by
  59   59   * 4.  Therefore, if one dumps %esp at the at the very first instruction in
  60   60   * a function, it will end with a 0xc.  The compiler expects this and
  61   61   * compensates for it properly.
  62   62   *
  63   63   * Note: If you change this value, you need to change it in the following
  64   64   * files as well:
  65   65   *
  66   66   *  - lib/libc/i386/threads/machdep.c
  67      - *  - lib/common/i386/crti.s
  68      - *  - lib/common/i386/crt1.s
       67 + *  - lib/crt/i86/crti.s
       68 + *  - lib/crt/i86/crt1.s
  69   69   */
  70   70  #undef  STACK_ALIGN
  71   71  #define STACK_ALIGN     16
  72   72  
  73   73  static void resumecontext(void);
  74   74  
  75   75  void
  76   76  makecontext(ucontext_t *ucp, void (*func)(), int argc, ...)
  77   77  {
  78   78          long *sp;

  79   79          long *tsp;
  80   80          va_list ap;
  81   81          size_t size;
  82   82  
  83   83          ucp->uc_mcontext.gregs[EIP] = (greg_t)func;
  84   84  
  85   85          size = sizeof (long) * (argc + 1);
  86   86  
  87   87          tsp = (long *)(((uintptr_t)ucp->uc_stack.ss_sp +
  88   88              ucp->uc_stack.ss_size - size) & ~(STACK_ALIGN - 1));
  89   89  
  90   90          /*
  91   91           * Since we're emulating the call instruction, we must push the
  92   92           * return address (which involves adjusting the stack pointer to
  93   93           * have the proper 4-byte bias).
  94   94           */
  95   95          sp = tsp - 1;
  96   96  
  97   97          *sp = (long)resumecontext;              /* return address */
  98   98  
  99   99          ucp->uc_mcontext.gregs[UESP] = (greg_t)sp;
 100  100  
 101  101          /*
 102  102           * "push" all the arguments
 103  103           */
 104  104          va_start(ap, argc);
 105  105          while (argc-- > 0)
 106  106                  *tsp++ = va_arg(ap, long);
 107  107          va_end(ap);
 108  108  }
 109  109  
 110  110  
 111  111  static void
 112  112  resumecontext(void)
 113  113  {
 114  114          ucontext_t uc;
 115  115  
 116  116          (void) getcontext(&uc);
 117  117          (void) setcontext(uc.uc_link);
 118  118  }

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